no Postharvest biology and technology of tropical and subtropical fruits (4 volumes) [1-4/1, 1 ed.] 9781845697341, 9781845697358, 9780857090904, 9781845697334, 9780857093622

Table of contents :
Volume 1 of 4, 544 pp. (pp. 1-544): Fundamental issues.
Volume 2 of 4, 586 pp. (pp. 545-1130): Açai to citrus.
Volume 3 of 4, 640 pp. (pp. 1131-1770): Cocona to mango.
Volume 4 of 4, 559 pp. (pp. 1771-2329): Mangosteen to white sapote.

Citation preview

Related titles: Postharvest biology and technology of tropical and subtropical fruits Volume 2 (ISBN 978-1-84569-734-1) Chapters in Volume 2 of this important collection review factors affecting the quality of different tropical and subtropical fruits, concentrating on postharvest biology and technology. Important issues relevant to each specific product are discussed, such as postharvest physiology, preharvest factors affecting postharvest quality, quality maintenance postharvest, pests and diseases and value-added processed products, among other topics. Postharvest biology and technology of tropical and subtropical fruits Volume 3 (ISBN 978-1-84569-735-8) Chapters in Volume 3 of this important collection review factors affecting the quality of different tropical and subtropical fruits, concentrating on postharvest biology and technology. Important issues relevant to each specific product are discussed, such as postharvest physiology, preharvest factors affecting postharvest quality, quality maintenance postharvest, pests and diseases and value-added processed products, among other topics. Postharvest biology and technology of tropical and subtropical fruits Volume 4 (ISBN 978-0-85709-090-4) Chapters in Volume 4 of this important collection review factors affecting the quality of different tropical and subtropical fruits, concentrating on postharvest biology and technology. Important issues relevant to each specific product are discussed, such as postharvest physiology, preharvest factors affecting postharvest quality, quality maintenance postharvest, pests and diseases and value-added processed products, among other topics. Details of these books and a complete list of Woodhead’s titles can be obtained by:

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© Woodhead Publishing Limited, 2011

Woodhead Publishing Series in Food Science, Technology and Nutrition: Number 206

Postharvest biology and technology of tropical and subtropical fruits Volume 1: Fundamental issues

Edited by Elhadi M. Yahia

© Woodhead Publishing Limited, 2011

Published by Woodhead Publishing Limited, 80 High Street, Sawston, Cambridge CB22 3HJ, UK www.woodheadpublishing.com Woodhead Publishing, 1518 Walnut Street, Suite 1100, Philadelphia, PA 19102-3406, USA Woodhead Publishing India Private Limited, G-2, Vardaan House, 7/28 Ansari Road, Daryaganj, New Delhi – 110002, India www.woodheadpublishingindia.com First published 2011, Woodhead Publishing Limited © Woodhead Publishing Limited, 2011; Chapter 8 was prepared by US government employees; this chapter is therefore in the public domain and cannot be copyrighted. The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials. Neither the authors nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Library of Congress Control Number: 2011934951 ISBN 978-1-84569-733-4 (print) ISBN 978-0-85709-362-2 (online) ISSN 2042-8049 Woodhead Publishing Series in Food Science, Technology and Nutrition (print) ISSN 2042-8057 Woodhead Publishing Series in Food Science, Technology and Nutrition (online) The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acid-free and elemental chlorine-free practices. Furthermore, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. Typeset by RefineCatch Limited, Bungay, Suffolk Printed by TJI Digital, Padstow, Cornwall, UK

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Contents

Contributor contact details .......................................................................... Woodhead Publishing Series in Food Science, Technology and Nutrition ........................................................................................ Dr Adel Kader .............................................................................................. Foreword ...................................................................................................... Preface ......................................................................................................... 1

2

Economic importance of tropical and subtropical fruits ................. Z. Mohamed, I. AbdLatif and A. Mahir Abdullah, University of Putra Malaysia, Malaysia 1.1 Introduction................................................................................. 1.2 World fruit production and contribution to gross domestic product (GDP) ............................................................................ 1.3 Global consumption of tropical and subtropical fruits ............... 1.4 International trade in tropical and subtropical fruit .................... 1.5 Price of tropical and subtropical fruit ......................................... 1.6 Conclusions................................................................................. 1.7 References................................................................................... Nutritional and health-promoting properties of tropical and subtropical fruits .......................................................................... E. M. Yahia, Autonomous University of Queretaro, Mexico and J. De Jesus Ornelas-Paz and G. A. Gonzalez-Aguilar, Research Center for Food and Development, Mexico 2.1 Introduction................................................................................. 2.2 Consumption ............................................................................... 2.3 Health components of tropical and subtropical fruits ................. 2.4 Bioactive compounds and antioxidant capacity .........................

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Contents 2.5 2.6 2.7 2.8 2.9 2.10

3

4

Overview of health effects of some tropical and subtropical fruits ............................................................................................ Preharvest factors affecting accumulation of nutritional and health components ............................................................... Postharvest factors affecting nutritional and health components ................................................................................. Enhancement of nutritional and health components in tropical and subtropical fruits ..................................................... Conclusions................................................................................. References...................................................................................

Postharvest biology of tropical and subtropical fruits ..................... A. A. Kader, University of California, Davis, USA and E. M. Yahia, Autonomous University of Queretaro, Mexico 3.1 Introduction................................................................................. 3.2 Diversity in fruit characteristics.................................................. 3.3 Maturation and ripening ............................................................. 3.4 Quality attributes ........................................................................ 3.5 Biological factors affecting deterioration ................................... 3.6 Environmental factors affecting deterioration ............................ 3.7 Pathological disorders and insect infestation .............................. 3.8 Biotechnological approaches for improving quality and postharvest life ............................................................................ 3.9 Conclusions................................................................................. 3.10 References................................................................................... Preharvest and harvest factors influencing the postharvest quality of tropical and subtropical fruits ........................................... N. Benkeblia and P. F. Tennant, University of the West Indies Mona Campus, Jamaica and S. K. Jawandha and P. S. Gill, Punjab Agricultural University, India 4.1 Introduction................................................................................. 4.2 Genetic factors ............................................................................ 4.3 Environmental factors ................................................................. 4.4 Physico-chemical factors ............................................................ 4.5 Diseases ...................................................................................... 4.6 Other factors ............................................................................... 4.7 Harvesting factors ....................................................................... 4.8 Phytohormones and other growth regulators .............................. 4.9 Conclusions................................................................................. 4.10 References...................................................................................

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Contents 5

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Postharvest technologies to maintain the quality of tropical and subtropical fruits .......................................................................... E. M. Yahia, Autonomous University of Queretaro, Mexico, J. De Jesus Ornelas-Paz, Research Center for Food and Development, Mexico and A. Elansari, Alexandria University, Egypt 5.1 Introduction................................................................................. 5.2 Maturity and harvesting indices.................................................. 5.3 Harvesting ................................................................................... 5.4 Conditioning ............................................................................... 5.5 Quality ........................................................................................ 5.6 The cold chain............................................................................. 5.7 Centralized packing operations................................................... 5.8 Ripening ...................................................................................... 5.9 Processing ................................................................................... 5.10 Conclusions................................................................................. 5.11 References................................................................................... Postharvest pathology of tropical and subtropical fruit and strategies for decay control ................................................................. S. Droby, Agricultural Research Organization (ARO), The Volcani Center, Israel, M. Wisniewski, United States Department of Agriculture – Agricultural Research Service (USDA – ARS), USA and N. Benkeblia, University of the West Indies Mona Campus, Jamaica 6.1 Introduction................................................................................. 6.2 Preharvest and postharvest factors affecting disease development ................................................................................ 6.3 Modes of infection by postharvest pathogens ............................ 6.4 Attack mechanisms ..................................................................... 6.5 Fruit defense mechanisms........................................................... 6.6 Major pathogens of subtropical and tropical fruits ..................... 6.7 Control of postharvest pathogens ............................................... 6.8 Conclusions and future challenges ............................................. 6.9 References................................................................................... Quarantine pests of tropical and subtropical fruits and their control .......................................................................................... E. M. Yahia and R. W. Jones, Autonomous University of Queretaro, Mexico and D. B. Thomas, United States Department of Agriculture – Agricultural Research Service (USDA – ARS), USA 7.1 Introduction................................................................................. 7.2 Internal fruit feeders: an introduction ......................................... 7.3 Diptera: Tephritidae .................................................................... 7.4 Lepidoptera: Tortricidae and Elachistidae ..................................

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Contents 7.5 7.6 7.7 7.8 7.9 7.10 7.11

8

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Coleoptera: mango seed weevil: Sternochetus mangiferae (Fabricius) (Curculionidae) ........................................................ External fruit feeders .................................................................. Control measures: an introduction .............................................. Preharvest control measures ....................................................... Postharvest control measures ...................................................... Conclusions................................................................................. References...................................................................................

Microbial safety of tropical and subtropical fruits ........................... M. Sharma and Y. Luo, United States Department of Agriculture – Agricultural Research Service (USDA – ARS), USA and R. Buchanan, University of Maryland, USA 8.1 Introduction................................................................................. 8.2 Foodborne pathogens associated with tropical and subtropical fruit ........................................................................... 8.3 Outbreaks of foodborne illness attributed to tropical and subtropical fruits ......................................................................... 8.4 Routes of contamination of tropical fruits .................................. 8.5 Interventions to reduce contamination of tropical fruits............. 8.6 Food safety programs used to minimize microbial contamination of fruits ................................................................ 8.7 Conclusions................................................................................. 8.8 References................................................................................... Biotechnology and molecular biology of tropical and subtropical fruits .................................................................................. M. A. Islas-Osuna and M. E. Tiznado-Hernández, Research Center for Food and Development, Mexico 9.1 Introduction................................................................................. 9.2 Genetic transformation, transcriptome sequencing, genome mapping and sequencing of fruits ................................. 9.3 Acerola (Malpighia emarginata DC.)......................................... 9.4 Avocado (Persea americana Mill.) ............................................ 9.5 Banana (Musa acuminata) .......................................................... 9.6 Cherimoya (Annona cherimola Mill.) ........................................ 9.7 Citrus........................................................................................... 9.8 Coconut (Cocos nucifera L.) ...................................................... 9.9 Date (Phoenix dactylifera L.) ..................................................... 9.10 Fig (Ficus carica L.) ................................................................... 9.11 Grape (Vitis vinifera L.) .............................................................. 9.12 Guava (Psidium guajava L.) ....................................................... 9.13 Kiwifruit (Actinidia deliciosa) .................................................... 9.14 Litchi (Litchi chinensis Sonn.) .................................................... 9.15 Longan (Dimocarpus longan Lour.) ...........................................

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Loquat (Eriobotrya japonica L.) ................................................ Mango (Mangifera indica L.) ..................................................... Mangosteen (Garcinia mangostana L.) ...................................... Melon (Cucumis melo L.) ........................................................... Nuts ............................................................................................. Olive (Olea europaea L.)............................................................ Papaya (Carica papaya L.) ......................................................... Passion fruit (Passiflora edulis Sim) .......................................... Pineapple (Ananas comosus L. Merr) ......................................... Sapodilla (Manilkara zapota) ..................................................... Conclusions................................................................................. References...................................................................................

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10 Fresh-cut tropical and subtropical fruit products ............................ G. A. Gonzalez-Aguilar, Research Center for Food and Development, Mexico, A. A. Kader, University of California, Davis, USA, J. K. Brecht, University of Florida, USA, and P. M. A. Toivonen, Agriculture and Agri-Food Canada, Canada 10.1 Fresh-cut produce industry worldwide ....................................... 10.2 Handling and conditioning of raw materials for processing ....... 10.3 Sanitation of whole and fresh-cut fruits...................................... 10.4 Mechanical and manual processing of fruits .............................. 10.5 Physiological and biochemical aspects of fresh-cut produce ..... 10.6 Effects of peeling and cutting on overall quality: texture, flavour and colour ....................................................................... 10.7 Preservative treatments for fresh-cut fruits................................. 10.8 Preservation of bioactive compounds and antioxidant capacity ....................................................................................... 10.9 Nutritional aspects of fresh-cut vs whole fruits .......................... 10.10 Hazard Analysis Critical Control Point (HACCP) and hygiene considerations for the fresh-cut produce industry ......... 10.11 Facilities, process design and equipment requirements .............. 10.12 New trends in the fresh-cut fruit industry ................................... 10.13 Economic and market considerations ......................................... 10.14 Conclusions................................................................................. 10.15 References...................................................................................

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11 Preservation and processing of tropical and subtropical fruits ....... A. Rosenthal and R. Torrezan, Embrapa Food Technology Centre, Brazil, F. L. Schmidt, State University of Campinas, Brazil and N. Narain, Federal University of Sergipe, Brazil 11.1 Factors responsible for the deterioration of tropical fruits and their products ....................................................................... 11.2 Microbiological aspects .............................................................. 11.3 Enzymes ......................................................................................

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Principles of conventional methods of preservation ................... Fruit preparation for preservation purposes ................................ Refrigeration and freezing .......................................................... Drying ......................................................................................... Manufacture of fruit beverages and purees ................................ Manufacture of jams and jellies .................................................. Heat treatments applied to fruit products.................................... Non-thermal processes applied to tropical and subtropical fruit processing ........................................................................... 11.12 Conclusions................................................................................. 11.13 References...................................................................................

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Index ............................................................................................................

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Contributor contact details (* = main contact) Chapter 1 Z. Mohamed*, I. AbdLatif and A. Mahir Abdullah Department of Agribusiness and Information Systems Faculty of Agriculture Universiti Putra Malaysia 43400 UPM, Serdang, Selangor Malaysia Email: [email protected]; [email protected]; [email protected]

J. De Jesus Ornelas-Paz Centro de Investigación en Alimentación y Desarrollo A.C. Unidad Cuauhtémoc, 31570 Cd. Cuauhtémoc Chihuahua Mexico Email: [email protected] G. Gonzalez-Aguilar Centro de Investigacion en Alimentacion y Desarrollo, A.C., A.P. 83000, La Victoria, Hermosillo, Sonora, Mexico Email: [email protected]

Chapter 2 E. M. Yahia* Facultad de Ciencias Naturales Universidad Autónoma de Queretaro Avenida las Ciencias S/N Juriquilla, 76230 Queretaro, Qro Mexico

Chapter 3 A. A. Kader* Department of Plant Sciences University of California, Davis CA 95616 USA

Email: [email protected] Email: [email protected]

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Contributor contact details

E. M. Yahia Facultad de Ciencias Naturales Universidad Autónoma de Queretaro Avenida las Ciencias S/N Juriquilla, 76230 Queretaro, Qro Mexico

J. De Jesus Ornelas-Paz Centro de Investigación en Alimentación y Desarrollo A.C. Unidad Cuauhtémoc, 31570 Cd. Cuauhtémoc Chihuahua Mexico

Email: [email protected]

Email: [email protected]

Chapter 4 N. Benkeblia* and P. F. Tennant Department of Life Sciences University of the West Indies Mona Campus, Kingston 7 Jamaica Email: noureddine.benkeblia@ uwimona.edu.jm; paula.tennant@ uwimona.edu.jm S. K. Jawandha and P. S. Gill Department of Horticulture Punjab Agricultural University Ludhiana India Email: [email protected]; [email protected] Chapter 5 E. M. Yahia* Facultad de Ciencias Naturales Universidad Autónoma de Queretaro Avenida las Ciencias S/N Juriquilla, 76230 Queretaro, Qro Mexico Email: [email protected]

A. Elansari Agricultural Engineering Department Faculty of Agriculture Alexandria University Egypt Email: [email protected] Chapter 6 S. Droby* Department of Postharvest Science Agricultural Research Organization The Volcani Center PO Box 6 Bet Dagan 50250 Israel Email: [email protected] M. Wisniewski United States Department of Agriculture – Agricultural Research Service (USDA – ARS) Appalachian Fruit Research Station 2217 Wiltshire Road Kearneysville WV 25430 USA Email: michael.wisniewski@ars. usda.gov

© Woodhead Publishing Limited, 2011

Contributor contact details N. Benkeblia Department of Life Sciences University of the West Indies Mona Campus, Kingston 7 Jamaica Email: noureddine.benkeblia@ uwimona.edu.jm Chapter 7 E. M. Yahia* and R. W. Jones Facultad de Ciencias Naturales Universidad Autónoma de Queretaro Avenida las Ciencias S/N Juriquilla, 76230 Queretaro, Qro Mexico Email: [email protected]; rjones@ uaq.mx D. B. Thomas Kika de la Garza Subtropical Agricultural Research Center United States Department of Agriculture – Agricultural Research Service (USDA – ARS) 2413 East Bus Hwy 83 Weslaco TX 78596 USA Email: [email protected]

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Chapter 8 M. Sharma* and Y. Luo Environmental Microbial and Food Safety Laboratory United States Department of Agriculture – Agricultural Research Service (USDA – ARS) 10300 Baltimore Ave Beltsville MD 20705 USA Email: [email protected] R. L. Buchanan Center for Food Safety and Security Systems University of Maryland 0119 Symons Hall College Park MD 20708 USA Email: [email protected] Chapter 9 M. A. Islas-Osuna* and M. E. Tiznado-Hernández Centro de Investigación en Alimentación y Desarrollo, A. C. CTAOV Carr. La Victoria Km 0.6 Apartado Postal 1735 Hermosillo Sonora, 83000 Mexico Email: [email protected]; tiznado@ ciad.mx

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Contributor contact details

Chapter 10

Chapter 11

G. Gonzalez-Aguilar* Centro de Investigacion en Alimentacion y Desarrollo, A.C. A.P. 83000, La Victoria Hermosillo Sonora Mexico

A. Rosenthal* and R. Torrezan Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Food Technology Av. das Américas, 29501 Guaratiba, Rio de Janeiro CEP 23020-470 Brazil

Email: [email protected] A. A. Kader Department of Plant Sciences University of California, Davis CA 95616 USA Email: [email protected] J. K. Brecht Horticultural Sciences Department Institute of Food and Agricultural Sciences University of Florida PO Box 110690 1301 Fifield Hall Gainesville Florida 32611-0690 USA Email: [email protected] P. M. A. Toivonen Agriculture and Agri-Food Canada PO Box 5000 4200 Hwy 97 Summerland, BC V0H 1Z0 Canada

Email: [email protected]; [email protected] F. L. Schmidt Unicamp (State University of Campinas) Faculty of Food Engineering Department of Food Technology Cidade Universitaria Zeferino Vaz Campinas, SP CEP 13083-862 Brazil Email: [email protected] N. Narain Department of Food Technology Federal University of Sergipe Cidade Universitaria Sao Cristovao, SE CEP 49100-000 Brazil Email: [email protected]

Email: [email protected]

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Food preservation techniques Edited by P. Zeuthen and L. Bøgh-Sørensen Food authenticity and traceability Edited by M. Lees Analytical methods for food additives R. Wood, L. Foster, A. Damant and P. Key Handbook of herbs and spices Volume 2 Edited by K. V. Peter Texture in food Volume 2: solid foods Edited by D. Kilcast Proteins in food processing Edited by R. Yada Detecting foreign bodies in food Edited by M. Edwards Understanding and measuring the shelf-life of food Edited by R. Steele Poultry meat processing and quality Edited by G. Mead Functional foods, ageing and degenerative disease Edited by C. Remacle and B. Reusens Mycotoxins in food: detection and control Edited by N. Magan and M. Olsen Improving the thermal processing of foods Edited by P. Richardson Pesticide, veterinary and other residues in food Edited by D. Watson Starch in food: structure, functions and applications Edited by A-C Eliasson Functional foods, cardiovascular disease and diabetes Edited by A. Arnoldi Brewing: science and practice D. E. Briggs, P. A. Brookes, R. Stevens and C. A. Boulton Using cereal science and technology for the benefit of consumers: proceedings of the 12th International ICC Cereal and Bread Congress, 24–26th May, 2004, Harrogate, UK Edited by S. P. Cauvain, L. S. Young and S. Salmon Improving the safety of fresh meat Edited by J. Sofos Understanding pathogen behaviour in food: virulence, stress response and resistance Edited by M. Griffiths The microwave processing of foods Edited by H. Schubert and M. Regier Food safety control in the poultry industry Edited by G. Mead Improving the safety of fresh fruit and vegetables Edited by W. Jongen Food, diet and obesity Edited by D. Mela Handbook of hygiene control in the food industry Edited by H. L. M. Lelieveld, M. A. Mostert and J. Holah Detecting allergens in food Edited by S. Koppelman and S. Hefle Improving the fat content of foods Edited by C. Williams and J. Buttriss Improving traceability in food processing and distribution Edited by I. Smith and A. Furness Flavour in food Edited by A. Voilley and P. Etievant The Chorleywood bread process S. P. Cauvain and L. S. Young Food spoilage microorganisms Edited by C. de W. Blackburn Emerging foodborne pathogens Edited by Y. Motarjemi and M. Adams Benders’ dictionary of nutrition and food technology Eighth edition D. A. Bender Optimising sweet taste in foods Edited by W. J. Spillane Brewing: new technologies Edited by C. Bamforth Handbook of herbs and spices Volume 3 Edited by K. V. Peter Lawrie’s meat science Seventh edition R. A. Lawrie in collaboration with D. A. Ledward Modifying lipids for use in food Edited by F. Gunstone Meat products handbook: practical science and technology G. Feiner Food consumption and disease risk: consumer-pathogen interactions Edited by M. Potter

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132 Acrylamide and other hazardous compounds in heat-treated foods Edited by K. Skog and J. Alexander 133 Managing allergens in food Edited by C. Mills, H. Wichers and K. HoffmanSommergruber 134 Microbiological analysis of red meat, poultry and eggs Edited by G. Mead 135 Maximising the value of marine by-products Edited by F. Shahidi 136 Chemical migration and food contact materials Edited by K. Barnes, R. Sinclair and D. Watson 137 Understanding consumers of food products Edited by L. Frewer and H. van Trijp 138 Reducing salt in foods: practical strategies Edited by D. Kilcast and F. Angus 139 Modelling microorganisms in food Edited by S. Brul, S. Van Gerwen and M. Zwietering 140 Tamime and Robinson’s Yoghurt: science and technology Third edition A. Y. Tamime and R. K. Robinson 141 Handbook of waste management and co-product recovery in food processing Volume 1 Edited by K. W. Waldron 142 Improving the flavour of cheese Edited by B. Weimer 143 Novel food ingredients for weight control Edited by C. J. K. Henry 144 Consumer-led food product development Edited by H. MacFie 145 Functional dairy products Volume 2 Edited by M. Saarela 146 Modifying flavour in food Edited by A. J. Taylor and J. Hort 147 Cheese problems solved Edited by P. L. H. McSweeney 148 Handbook of organic food safety and quality Edited by J. Cooper, C. Leifert and U. Niggli 149 Understanding and controlling the microstructure of complex foods Edited by D. J. McClements 150 Novel enzyme technology for food applications Edited by R. Rastall 151 Food preservation by pulsed electric fields: from research to application Edited by H. L. M. Lelieveld and S. W. H. de Haan 152 Technology of functional cereal products Edited by B. R. Hamaker 153 Case studies in food product development Edited by M. Earle and R. Earle 154 Delivery and controlled release of bioactives in foods and nutraceuticals Edited by N. Garti 155 Fruit and vegetable flavour: recent advances and future prospects Edited by B. Brückner and S. G. Wyllie 156 Food fortification and supplementation: technological, safety and regulatory aspects Edited by P. Berry Ottaway 157 Improving the health-promoting properties of fruit and vegetable products Edited by F. A. Tomás-Barberán and M. I. Gil 158 Improving seafood products for the consumer Edited by T. Børresen 159 In-pack processed foods: improving quality Edited by P. Richardson 160 Handbook of water and energy management in food processing Edited by J. Klemeš, R. Smith and J-K Kim 161 Environmentally compatible food packaging Edited by E. Chiellini 162 Improving farmed fish quality and safety Edited by Ø. Lie 163 Carbohydrate-active enzymes Edited by K-H Park 164 Chilled foods: a comprehensive guide Third edition Edited by M. Brown 165 Food for the ageing population Edited by M. M. Raats, C. P. G. M. de Groot and W. A Van Staveren

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166 Improving the sensory and nutritional quality of fresh meat Edited by J. P. Kerry and D. A. Ledward 167 Shellfish safety and quality Edited by S. E. Shumway and G. E. Rodrick 168 Functional and speciality beverage technology Edited by P. Paquin 169 Functional foods: principles and technology M. Guo 170 Endocrine-disrupting chemicals in food Edited by I. Shaw 171 Meals in science and practice: interdisciplinary research and business applications Edited by H. L. Meiselman 172 Food constituents and oral health: current status and future prospects Edited by M. Wilson 173 Handbook of hydrocolloids Second edition Edited by G. O. Phillips and P. A. Williams 174 Food processing technology: principles and practice Third edition P. J. Fellows 175 Science and technology of enrobed and filled chocolate, confectionery and bakery products Edited by G. Talbot 176 Foodborne pathogens: hazards, risk analysis and control Second edition Edited by C. de W. Blackburn and P. J. McClure 177 Designing functional foods: measuring and controlling food structure breakdown and absorption Edited by D. J. McClements and E. A. Decker 178 New technologies in aquaculture: improving production efficiency, quality and environmental management Edited by G. Burnell and G. Allan 179 More baking problems solved S. P. Cauvain and L. S. Young 180 Soft drink and fruit juice problems solved P. Ashurst and R. Hargitt 181 Biofilms in the food and beverage industries Edited by P. M. Fratamico, B. A. Annous and N. W. Gunther 182 Dairy-derived ingredients: food and neutraceutical uses Edited by M. Corredig 183 Handbook of waste management and co-product recovery in food processing Volume 2 Edited by K. W. Waldron 184 Innovations in food labelling Edited by J. Albert 185 Delivering performance in food supply chains Edited by C. Mena and G. Stevens 186 Chemical deterioration and physical instability of food and beverages Edited by L. H. Skibsted, J. Risbo and M. L. Andersen 187 Managing wine quality Volume 1: viticulture and wine quality Edited by A.G. Reynolds 188 Improving the safety and quality of milk Volume 1: milk production and processing Edited by M. Griffiths 189 Improving the safety and quality of milk Volume 2: improving quality in milk products Edited by M. Griffiths 190 Cereal grains: assessing and managing quality Edited by C. Wrigley and I. Batey 191 Sensory analysis for food and beverage quality control: a practical guide Edited by D. Kilcast 192 Managing wine quality Volume 2: oenology and wine quality Edited by A. G. Reynolds 193 Winemaking problems solved Edited by C. E. Butzke 194 Environmental assessment and management in the food industry Edited by U. Sonesson, J. Berlin and F. Ziegler 195 Consumer-driven innovation in food and personal care products Edited by S.R. Jaeger and H. MacFie

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196 Tracing pathogens in the food chain Edited by S. Brul, P.M. Fratamico and T.A. McMeekin 197 Case studies in novel food processing technologies: innovations in processing, packaging, and predictive modelling Edited by C. J. Doona, K. Kustin and F. E. Feeherry 198 Freeze-drying of pharmaceutical and food products T-C Hua, B-L Liu and H Zhang 199 Oxidation in foods and beverages and antioxidant applications Volume 1: understanding mechanisms of oxidation and antioxidant activity Edited by E. A. Decker, R. J. Elias and D. J. McClements 200 Oxidation in foods and beverages and antioxidant applications Volume 2: management in different industry sectors Edited by E. A. Decker, R. J. Elias and D. J. McClements 201 Protective cultures, antimicrobial metabolites and bacteriophages for food and beverage biopreservation Edited by C. Lacroix 202 Separation, extraction and concentration processes in the food, beverage and nutraceutical industries Edited by S. S. H. Rizvi 203 Determining mycotoxins and mycotoxigenic fungi in food and feed Edited by S. De Saeger 204 Developing children’s food products Edited by D. Kilcast and F. Angus 205 Functional foods: concept to product Second edition Edited by M. Saarela 206 Postharvest biology and technology of tropical and subtropical fruits Volume 1: Fundamental issues Edited by E. M. Yahia 207 Postharvest biology and technology of tropical and subtropical fruits Volume 2: Açai to citrus Edited by E. M. Yahia 208 Postharvest biology and technology of tropical and subtropical fruits Volume 3: Cocona to mango Edited by E. M. Yahia 209 Postharvest biology and technology of tropical and subtropical fruits Volume 4: Mangosteen to white sapote Edited by E. M. Yahia 210 Food and beverage stability and shelf life Edited by D. Kilcast and P. Subramaniam 211 Processed Meats: improving safety, nutrition and quality Edited by J. P. Kerry and J. F. Kerry 212 Food chain integrity: a holistic approach to food traceability, safety, quality and authenticity Edited by J. Hoorfar, K. Jordan, F. Butler and R. Prugger 213 Improving the safety and quality of eggs and egg products Volume 1 Edited by Y. Nys, M. Bain and F. Van Immerseel 214 Improving the safety and quality of eggs and egg products Volume 2 Edited by F. Van Immerseel, Y. Nys and M. Bain 215 Feed and fodder contamination: effects on livestock and food safety Edited by J. Fink-Gremmels 216 Hygienic design of food factories Edited by J. Holah and H. L. M. Lelieveld 217 Manley’s technology of biscuits, crackers and cookies Fourth edition Edited by D. Manley 218 Nanotechnology in the food, beverage and nutraceutical industries Edited by Q. Huang 219 Rice quality: A guide to rice properties and analysis K. R. Bhattacharya 220 Advances in meat, poultry and seafood packaging Edited by J. P. Kerry 221 Reducing saturated fats in foods Edited by G. Talbot

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222 Handbook of food proteins Edited by G. O. Phillips and P. A. Williams 223 Lifetime nutritional influences on cognition, behaviour and psychiatric illness Edited by D. Benton 224 Food machinery for the production of cereal foods, snack foods and confectionery L-M Cheng

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Dr Adel Kader

Few people have had as much of an impact on a field of scientific study as Dr Adel Kader has had on the discipline of postharvest physiology and technology. Through his numerous publications and students, Dr Kader has influenced an entire generation of researchers, teachers and extension personnel. Just as important as this tangible evidence of his long and illustrious career is the intangible influence he has had on shaping the focus and direction of postharvest research and extension activities worldwide. While most of his time at the University of California, Davis (UCD) was spent on improving the more obvious aspects of postharvest quality of fruits, he became increasingly interested in the less obvious characteristics of flavor and nutritional quality. He realized that an improvement in people’s diets through the consumption of more fruits and vegetables would only occur when the appearance quality of fruits and vegetables was matched by an increase in their flavor and nutritive quality. He became a vocal proponent of coupling the traditional studies of appearance quality with studies of flavor and nutritional quality changes during harvest, storage, transport and marketing of horticultural commodities. During his more than 35 years at UCD he continued his teaching, research and extension activities in the area of postharvest biology and technology of horticultural crops. His prodigious output includes over 230 technical publications and many book chapters. Almost more important than his written output are his mentoring of 36 graduate students and 60 scientists who participated in his ongoing research programs. His commitment to continuing education is exemplified by his participation in the annual two-week Postharvest Technology Short Course which he was instrumental in organizing in 1979 and which has

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Dr Adel Kader

been attended by over 2 500 people. Never one to rest on his laurels, Adel launched in 1998 the postharvest website (http://postharvest.ucdavis.edu) which has become the premier source of postharvest information worldwide. Dr Kader received his BSc in Horticulture from the Faculty of Agriculture at Ain Shams University in Egypt in 1959. He then moved to UCD where he received his MSc in Vegetable Crops in 1962 and his PhD in Plant Physiology in 1966. After receiving his doctorate, he returned to Egypt where he held the position of Assistant Professor in the Faculty of Agriculture at Ain Shams University, Cairo, from 1966 to 1971. While there he was engaged in teaching and research on postharvest horticulture. He then became a lecturer and consultant in the Kuwait Institute for Scientific Research from 1971 to 1972. Again his emphasis was on teaching and consulting on the postharvest handling of horticultural crops. He returned to UCD in 1972, first as an Assistant Researcher, and later as an Assistant, Associate, and full Professor, and he retained this position until his retirement in 2007. He became a US citizen in 1976. During his retirement he and his wife, Aileen, plan to travel and spend time with their children. Dr Kader is currently an Emeritus Professor at UCD, where he was for 35 years. During that time he served as Chairman of the Department of Pomology and received a number of awards. A listing of just a few of them will illustrate the breadth of his accomplishments. He was elected a Fellow of the American Society for Horticultural Science (1986), and served as President-elect (1994–95), President (1995–96), and Chairman of the Board of Directors (1996–97) of the Society. He received from UCD the Outstanding Teaching Award in Extension (1989), the Award of Distinction from the College of Agricultural and Environmental Sciences (2000), the Alumni Citation of Excellence from the Cal Aggie Alumni Association (2000), and the Academic Senate’s Distinguished Graduate Mentoring Award (2003). He was also selected as the Outstanding Horticulturist of 1997 by the Horticultural Research Center at Laval University, Quebec, Canada. Although retired, Dr Kader still maintains an active interest in postharvest programs worldwide and frequently participates in seminars at UCD and international meetings. He continues to do some consulting to raise funds for the UC Davis postharvest endowment. The absence of his experience and sage advice creates a void that is difficult to fill. Professor Mikal Saltveit University of California, Davis, USA

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Foreword

Mangoes, mangosteens, and papayas may have been around for as long as apples and oranges, but you would never have known that based on a visit to a typical North American or European supermarket 20 years ago. Back then, the average grocery store carried only a handful of tropical and subtropical fruits – primarily oranges, bananas, and pineapples. Today, mangoes, papayas, avocados, and kiwifruits are a staple on grocery shelves all over the world, and it’s even possible, here and there, to find a Safeway, a Kroger or an Ahold supermarket with an entire section in the produce department devoted to once exotic tropical and subtropical fruits. It is very unlikely that another 20 years will elapse before such displays are expanded to include mangosteens, cherimoyas, sapodillas, longans, loquats, and rambutans. Much of the steadily growing appeal of tropical and subtropical fruits can be attributed to the new and nutritious tastes and flavors they offer to consumers in the Northern Hemisphere. But any proper explanation would have to also recognize the essential role played by growers, governments, and academics, as well as the vendors, transporters, and other industries that support the sale and distribution of these delectables. Since 1982 I have had the privilege to serve as president of both the International Association of Refrigerated Warehouses (IARW) and the World Food Logistics Organization (WFLO), both of which have since become partners in the Global Cold Chain Alliance (GCCA). The history of IARW dates back 120 years, to a time when large-scale food storage was, for the most part, limited to keeping products surrounded by blocks of ice. With the advent of mechanical refrigeration in the last quarter of the nineteenth century, beer brewers were, apparently, among the first significant users of industrial refrigeration. By the turn of the century, ammonia refrigeration was adopted by the meatpacking industry and before long it was widely embraced by fruit, vegetable, and dairy producers as well.

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Today, there are more than 350 IARW members in 67 countries on six continents, offering a nearly unimaginable variety of freezing, cooling, tempering, storage, handling, and shipping services to the global food industry. To help carry out the important work of feeding much of the world, cold storage companies look to the non-profit WFLO for guidance. Founded in 1943, WFLO is dedicated to the proper handling and storage of perishable products, and to developing best practices for the safe, efficient, and reliable movement of food. As it endeavored to achieve these goals, WFLO developed a Commodity Storage Manual (CSM) and created a Scientific Advisory Council (SAC) comprised of approximately 15 distinguished food scientists and specialists in engineering, agricultural economics, and logistics. The CSM contains detailed information on hundreds of different meats, fish, dairy products, vegetables, and fruits, including a number of tropical and subtropical fruits. SAC members and other food scientists provide CSM readers with details about storage conditions, shelf life, color, odor transfer, product diseases, and additional useful information, all of which is product-specific. During the past 65+ years, SAC members have also conducted or supervised more than 150 research projects addressing such topics as the effect of storage temperatures on quality, mobility threshold temperatures (glass transition), use of an ‘electronic nose’ to measure quality attributes of seafood, the sensitivity of product quality to fluctuating temperatures, and temperature control in frozen food transportation. While much of this research attention has focused on low temperature issues, SAC members are, of course, also very mindful of such other preservation techniques as temperature elevation (blanching, pasteurization, etc.), water reduction, ionizing radiation, and so on. I have had the pleasure of working with Elhadi Yahia in his capacity as a member of the WFLO Scientific Advisory Council, where he has generously shared his expertise in the postharvest technology of perishable foods. Through his work on the council, Dr Yahia has enabled hundreds of cold storage operators and refrigerated transportation providers to better understand and address a wide range of matters related to food preservation, food safety, and food quality. And now, with the publication of Postharvest Biology and Technology of Tropical and Subtropical Fruits, Professor Yahia makes an enduring contribution available to many more people around the globe. This sourcebook contains a wealth of information about every conceivable aspect of tropical and subtropical fruit production, harvesting, and health. It comprehensively addresses the causes and cures of traditionally significant postharvest losses, whether due to biochemical, environmental, economic, or regulatory factors. The book also discusses a variety of control measures and preservation processes that will enable growers and researchers to achieve both higher quality and higher quantities of market caliber fruits. As if that were not enough, the information and guidance included in this publication take into account food safety concerns and are fully compatible with the principles of sustainability. Accompanying this volume are three other tomes containing a total of more than 60 chapters, each one devoted to a particular tropical or subtropical fruit.

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These comprehensive discussions typically cover development, physiology, quality indices, preharvest conditions, diseases, postharvest handling, processing, and other valuable guidance. Tropical fruits occupy a special niche in the world of agriculture. For one thing, more than 90% of tropical fruit production takes place in developing countries. This often connotes the presence of fewer good roads, less reliable power sources, and greater dependence on low-tech storage solutions. Second, harvested crops are frequently subjected to a convoluted supply chain in which the fruit is handled time and again by farm collectors, middlemen, market agents, exporters, and sellers before ever reaching the consumer. These circumstances inflict a great deal of stress on products that are typically more perishable to begin with than fruits from more temperate climates. The UN Food and Agriculture Organization (FAO) states that the reduction of postharvest food loss needs to be a major agricultural goal in a hungry and increasingly competitive world. FAO goes on to point out that investments made to save food postharvest are invariably less costly – for the grower and the consumer – than efforts to increase production by comparable magnitudes. The agency further contends that even a partial reduction in postharvest losses can lessen dependence on marginal land and other scarce resources. Dr Yahia’s encyclopedic work will help growers to better understand latent hazards and how to deal with them. It will help growers and distributors alike to utilize best practices to minimize product losses and maximize quality. It will both help feed more local communities and ensure that fragile tropical fruits are as well suited as possible to long distance shipment. And by better informing food handlers throughout the supply chain it will ultimately boost trade and bring the benefits of tropical and subtropical fruits to millions of people who have never enjoyed the rich flavors and health benefits of mangosteens or breadfruits. Having worked closely with the food industry for a quarter of a century, I know that this project was anything but easy. Dr Yahia’s mission involved mastering the details on literally thousands of tropical and subtropical varieties. It entailed dealing with the newest and most advanced food science as well as ‘nuts and bolts’ applications of that science. And it tackles these issues in the context of increased international trade and a global economic shift that rewards winners handsomely and penalizes others decisively. I think it is fair to say that this milestone publication could not have come at a better time. J. William Hudson President and CEO World Food Logistics Organization

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Preface

Introduction to tropical and subtropical fruits Tropical and subtropical fruits include a large number of crops such as acerola, aonla, avocado, bael, banana, black sapote, breadfruit, breadnut, carambola, cherimoya, chili plum, citrus fruit, cocona, coconut, date, durian, feijoa, fig, golden apple, grape, guava, jaboticaba, jackfruit, kiwifruit, longan, loquat, litchi, macadamia, mamey sapote, mango, mangosteen, nance, noni, olive, papaya, passion fruit, pecan, persimmon, pineapple, pistachio, pitahaya, pitanga, pomegranate, rambutan, salak, sapodilla, soursop, star apple, tamarillo, tamarind, wax apple, among many others (see volumes 2, 3 and 4 of this collection). They are important commodities with multiple uses, and their contribution to human nutrition and health and lives is very significant. Tropical and subtropical fruit plants come from a wide range of botanical families, are of different types, including vines (e.g. passion fruit), herbaceous crops (e.g. bananas) and woody plants (e.g. oranges), and produce various kinds of fruit such as berries (e.g. avocados), drupes (e.g. mangoes), nutlets (e.g. litchis) and compound fruits (e.g. pineapples). It is not straightforward to make a distinction between tropical and subtropical fruits, and, indeed, several can be cultivated both in the tropics and subtropics. Citrus, for example, is of tropical origin, yet achieves better quality when grown in the subtropics, or at higher elevations in the tropics. The geographical boundaries of the tropics may not, in fact, be the best indication of whether a fruit is tropical or subtropical, as some areas within the tropics have a climate that is not typically considered tropical, due to factors such as altitude. In general, tropical areas are those which remain constantly warm. In other words, they are areas in which the warmest month is only a few degrees hotter than the coldest, temperature differences between day and night are greater than those

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between summer and winter and there is little variation in day length. Subtropical regions generally have a greater difference in temperature between summer and winter and are less humid. Though there are tropical and subtropical fruit native to almost all continents, the majority of the most widely traded species originate from the American continent (e.g. papayas, guavas) or Asia (e.g. most citrus fruits, mangoes and bananas), some exceptions being dates from Africa and coconuts from Oceania. Tropical and subtropical fruits have long been part of the diet in certain areas. While the general public may just now be discovering many tropical fruits, these delicacies have served as staples for some cultures for generations. Mango has been cultivated and consumed in India for more than 4000 years, the Chinese have harvested litchis for thousands of years, carambolas (starfruit) have been popular in Malaysia for centuries, papaya was enjoyed throughout Latin America long before Columbus’s arrival, and dates have been the staple food of the Middle East and North Africa for thousands of years. Tropical and subtropical fruit are thought to have spread very early from their respective areas of origin. For example, the conquest of parts of the Iberian peninsula by Moorish Muslim armies from North Africa brought oranges to southern Europe, and the Europeans brought crops from the New World back to the Old World. In general, the establishment of trade routes facilitated the spread of crops, especially those whose fruit and planting material could survive long voyages.

Trade in tropical and subtropical fruits The major traded tropical and subtropical fruits include citrus fruits, banana, mango, pineapple and papaya. Some other tropical and subtropical fruits, such as durian and mangosteen, are not so extensively cultivated or traded, but are still important economically in their own regional markets. There are also a significant number of tropical and subtropical fruits which are not cultivated commercially. According to 2010 FAO statistics, world production of certain fruit amounts to the following: banana – almost 60 million tonnes (mmt), mango – almost 25 mmt, papaya – more than 8 mmt, pineapple – more than 13 mmt and plantain – more than 30 mmt. About 98% of tropical fruits and significant quantities of subtropical fruits are produced in developing countries. More than 50% of tropical and subtropical fruits are consumed fresh, and the rest is consumed in many different processed forms. There has been a major drive to promote several minor fruits (including many tropical and subtropical fruits) in international trade, but in general, it can be postulated that a significant gap still exists between world per capita consumption and estimated consumption saturation. Immigrant communities in several countries (including North America and European countries) who have used minor fruits in their diet for generations, have played a role in the establishment of new markets in their adopted countries of residence. In addition, tourists and travelers from many Western countries have been exposed to many of these fruits in the tropics and subtropics and have either started to

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demand that they are stocked in the shops and marketplaces they usually frequent, or have begun to acquire them from shops and marketplaces that cater primarily for immigrants. In addition, there are areas in North America (around the southern tip of Florida, Hawaii, Puerto Rico) and in Europe (such as in the Canary Islands) which have suitable climates for tropical fruits, and fruits grown in those regions have also found their way to markets and consumers elsewhere in the United States and Europe, therefore increasing the promotion of these minor fruits. The increasing interest in and marketing prospects for tropical and subtropical fruits worldwide have made the science underpinning postharvest technologies for these fruits a priority research and development area in several countries, including many developing countries. There is increasing demand for tropical and subtropical fruit handling information from shippers, importers and trade organizations. However, making handling information available is often of limited importance to whole regions (this applies especially to information on some very minor and exotic fruits). This reflects the characteristics of several tropical and some subtropical fruit industries: they are comparatively small, dispersed and fragmented and production is highly seasonal. Production also mostly takes place in developing countries, where adequate distribution systems are yet to be established. It is in the economic and national interest of food/fruit exporting countries to possess and maintain an international commercial reputation as a reliable supplier of products of acceptable sensory and safety quality, and therefore the establishment of adequate postharvest handling systems for these fruits is essential.

Postharvest handling systems for tropical and subtropical fruits Most tropical fruits and several subtropical fruits are highly perishable and can only be maintained for short periods of time (from a few days to a very few weeks), but some fruits can be maintained for extended period of time (such as oranges, some cultivars of table grapes, nuts and dried fruits). The three major postharvest problems that affect tropical and subtropical fruits (especially tropicals) are chilling injury, decay and insect damage. Chilling injury (CI) is a common problem in most tropical and several subtropical fruits. Most temperate fruits can be stored for the longest period of time at around 0°C (just above the freezing point), and are injured only if they freeze. However, many tropical and subtropical fruits are injured by low, nonfreezing temperatures in the range 0°–13°C. CI results in surface pitting, browning of the peel and flesh, and faster postharvest decay development. Thus, postharvest temperature control is even more critical for tropical and subtropical fruits than for temperate fruits. The high perishability of these fruits (especially tropical fruits) is due not only to the higher storage temperature requirements, but also to their general nature: most tropical fruits are climacteric and produce high quantities of ethylene, but some, such as citrus, are ‘non-climacteric’. Citrus fruit ripen slowly, without going through a burst of respiration, softening, and color change right at the end of development,

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and can be stored on the tree for several weeks, widening the window in which the crop can be marketed and allowing for greater marketing flexibility. Almost all tropical fruits and most subtropical fruits are produced in developing countries and postharvest handling systems in these areas are, in most cases, not adequately developed (see Plate Ia in the color section between p 238 and p 239). Therefore rates of deterioration and losses are commonly high. Common inadequate handling practices causing significant qualitative and quantitative losses include a lack of adequate ripening indices and harvesting methods, a non-existent or inadequate cold chain and inadequate storage and marketing practices (Plate Ia). However, there have recently been improvements in the postharvest handling in particular of fruit for export, and also of locally marketed crops. Plate Ib shows fruits of excellent quality in a local supermarket in a developing country. Fruit intended for export is commonly handled better in developing countries, but improvements have also been seen in postharvest handling of locally consumed commodities. Export of fresh tropical and subtropical fruits is mainly done by ship or surface transport. These transport techniques have improved very significantly, and refrigerated boats (some even providing modified and controlled atmospheres and quarantine facilities) move these commodities from producing countries to their ultimate markets with relative ease. A small proportion of some tropical fruits, such as mangosteen and rambutan, are sometimes still transported by air, especially when they are destined for gourmet or niche markets or for celebrations at certain times of the year, such as Christmas and New Year, when they command higher prices. Several important postharvest techniques are available for the handling of tropical and subtropical fruits; some of them are very simple and can be adapted in any location. The most common pre-cooling techniques for these fruits are forced-air and hydrocooling. Modified and controlled atmospheres are used for storage of a very few fruit (such as kiwifruit), for transport of several fruits (such as mango, banana, avocado, papaya), and for packaging of some minimally processed products. Ethylene is used for the ripening of some fruits (such as banana), and 1-MCP (1-methylcyclopropene) is efficient in controlling ripening of some fruits. Several treatments are legally established for quarantine control, such as low temperature (for citrus and grapes), heat (for mango and grapefruit), and irradiation (for mango and guava). Plate II (also in the color section) shows hot water quarantine treatment of mango in Mexico. Heat treatments (especially hot water treatments) are effective in controlling postharvest decay and are commercially used on the mango, among other fruits. Tropical and subtropical fruits are suitable for the development of many minimally processed and processed products. Biotechnology is also another technique that has excellent potential for the improvement of various product characteristics and for solving several problems associated with tropical and subtropical fruit.

Conclusions Major research efforts and activities are still needed to solve some problems (especially related to chilling injury, decay and insects), and to establish better

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postharvest handling practices, especially for tropical fruits. Major extension and technology transfer efforts are also still needed, especially in developing countries, to establish better mechanisms by which to transfer the results of research and encourage the adoption of the new handling practices developed. Many more details can be found in the following chapters of the four volumes of this collection. The following 78 chapters demonstrate the diversity of tropical and subtropical fruit, their characteristics and importance, and the knowledge that has accumulated on their handling after harvest. Excellent postharvest knowledge has been generated in the past few decades through the efforts of many excellent scientists and extension specialists, such as Prof. Adel A. Kader to whom we dedicate the book for his significant contributions and efforts. I would like to thank all the authors for their excellent efforts and patience. Many thanks are also due to Mr Bill Hudson, Prof. Jules Janick, Prof. Ian Ferguson and Prof. George Wilson for agreeing to write the forewords to the four volumes, to Prof. Mikal Saltveit for writing the dedication, and to Prof. Jeffrey Brecht for his help during the initial preparation of the book proposal. The help and support of the Woodhead team, especially Ms Sarah Whitworth and Ms Vicki Hart, is very much appreciated. Finally, the importance of adequate postharvest handling and prevention of qualitative and quantitative losses of these important food commodities (and any other food commodity) is very important, and I think it could not be explained in a simpler manner than by the following Chinese proverb that states: ‘if you make your plans for a year, plant rice, if you make them for one decade, plant trees, and if you make them for a lifetime, do not waste food.’ Elhadi M. Yahia

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1 Economic importance of tropical and subtropical fruits Z. Mohamed, I. AbdLatif and A. Mahir Abdullah, University of Putra Malaysia, Malaysia

Abstract: Asian countries are among the largest producers of tropical and subtropical fruits in the world. The top five tropical and subtropical fruits in terms of production volume are watermelon, orange, grape, banana and tangerine/mandarin. China is the largest producer of watermelon, Brazil of oranges, Italy of grapes and India of bananas. Most of the fruits are consumed as food in fresh and processed form. EU countries are the main destination for tropical and subtropical fruits, consuming nearly 50% of the total world export, while also supplying temperate and subtropical fruits to the global fruits market. The importance of fruit production for the economic development of a country can be seen in its contribution to the gross domestic product (GDP) and employment through agriculture. Most less-developed countries depend on agriculture as a major source of income and employment. Price demand elasticities for most fruits are elastic. Key words: tropical and subtropical fruits, producers, GDP, employment, consumption, elasticities and prices.

1.1

Introduction

There are a very large number of different tropical and subtropical fruits, yet only 50 or so are well known in most parts of the world (Martin et al., 1987). The estimated gap between world per capita consumption (54.9 kg per year) and estimated consumption saturation (100 to 120 kg per year) is considerable (TFNet, 2003). According to Galán Saúco (1996) and Katz et al. (2003), tropical and subtropical fruit can be divided into three groups based on production and trade figures, (with some overlap between categories). The first group, ‘major fruits’,

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2

Postharvest biology and technology of tropical and subtropical fruits

include crops such as banana and plantain, citrus, coconut, mango and pineapple. These are cultivated in most tropical and subtropical countries and are found in international markets as well as local ones. The next group, ‘minor fruits’ (e.g. avocado, breadfruit, carambola, cashew nut, durian, guava, jackfruit, litchi, macadamia, mangosteen, papaya, passion fruit, sapodilla and soursop) are not cultivated as extensively. Trade in these crops (and therefore also consumption) is likely to be less widespread, both geographically and quantitatively. Nevertheless, some of these minor fruits, such as carambola, durian and mangosteen from South-East Asia are of considerable economic significance in regional markets (Anang and Chan, 1999). The last group, ‘wild fruits’, are not cultivated commercially. They come from various botanical families and have generally not been well characterized (Katz et al., 2003).

1.2 World fruit production and contribution to gross domestic product (GDP) 1.2.1 Global production of tropical and subtropical fruits According to the world food balance sheets published by the Food and Agriculture Organization (FAO), the total world fruit supply in 2005 was 517 million tonnes. It comprised 514 million tonnes of fruit production, 107 million tonnes of imports and 106 million tonnes of exports (stock variations accounted for 2 million tonnes). Asia contributed 46% of the total world fruit production, while the Americas contributed 26%. Europe, Africa and Oceania held 14%, 13% and 1% of the share of world fruit production in 2005, respectively (Fig. 1.1) (FAOSTAT, 2008). The total world production for the ten most popular fruit types in 2008 was over 431 million tonnes. As shown in Fig. 1.2, watermelons, bananas, grapes, oranges, mangoes and tangerines are among the most produced around the globe. Other important fruits include pineapples, papayas, other citrus fruits and dates (FAOSTAT 2008).

Fig. 1.1 World fruit production share by continent.

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Economic importance of tropical and subtropical fruits

3

Fig. 1.2 World production of selected tropical fruits.

World fruit production has increased over the years. There has been an increase of 17% for the ten fruit types for the past five years, as shown in Table 1.1. The production increase was a response from producers to the general increase in demand for tropical and subtropical fruits worldwide. As illustrated in Fig. 1.3, higher production growth was observed for bananas and watermelons, in contrast to a lower growth rate for grapes and oranges from 2003 to 2008. The nature of the crops in question could account for this: short-term crops such as banana and watermelon can respond quickly to increased demand, while longer-term crops such as grapes and oranges cannot.

Fig. 1.3 Production trends for ten most popular fruits.

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369 579 995

Dates

Total

Source: FAOSTAT (2008)

6 815 494 6 669 625

Citrus fruit

7 930 846

Papayas

29 359 957

Mangoes, mangosteens, guavas

22 030 899

59 491 522

Oranges

16 096 896

63 685 749

Grapes

Pineapples

70 209 520

Bananas

Tangerines, mandarins, clementines

87 289 487

2003

Watermelons

Fruit type

386 794 211

7 041 628

7 036 877

8 594 281

16 667 953

23 412 226

29 087 337

64 709 042

67 565 568

74 845 330

87 833 969

2004

393 512 356

6 548 201

7 109 308

8 066 114

17 856 630

23 735 119

31 251 420

62 829 839

67 190 031

78 749 456

90 176 238

2005

Table 1.1 World tropical and subtropical fruit production by fruit types (tonnes), 2003–2008

410 241 458

6 701 968

6 936 267

8 913 064

19 210 902

26 234 839

32 995 171

65 319 196

67 333 393

82 887 488

93 709 170

2006

421 260 621

6 908 900

7 223 647

9 210 748

20 911 077

27 864 626

33 866 557

64 763 648

67 221 000

85 855 856

97 434 562

2007

430 967 277

7 048 089

7 452 302

9 095 875

19 166 560

28 556 834

34 343 083

67 695 802

67 708 587

90 705 922

99 194 223

2008

Economic importance of tropical and subtropical fruits

5

Tables 1.2 to 1.5 illustrate the main fruit producing countries by fruit types. The tables show that China is an important contributor to world fruit production. In 2008, the country produced 67% of the total world watermelon production, and almost 11% of the total world grape production, alongside 9% and 5% of world banana and orange production respectively. Other major producers of watermelons in the same year were Turkey, Iran, Brazil and the USA. India was the leading producer of bananas in 2008, with approximately 26% of the global total. The second most important banana-producing country was the Philippines with a share of almost 10% of world production. Other significant banana producers were Brazil, Ecuador and Indonesia. Table 1.2 Top ten watermelon producing countries 2008 Country

Tonnes

China

67 203 275

Turkey

4 002 280

Iran, Islamic Republic of

3 400 000

Brazil

1 950 000

United States of America

1 793 990

Egypt

1 485 939

Mexico

1 199 711

Russian Federation

1 100 000

Uzbekistan

981 200

Korea, Republic of

856 755

Source: FAOSTAT (2008)

Table 1.3 Top ten banana producing countries 2008 Country

Tonnes

India

23 204 800

Philippines

8 687 624

China

8 042 702

Brazil

7 116 808

Ecuador

6 701 146

Indonesia

5 741 352

Tanzania, United Republic of

3 500 000

Mexico

2 159 280

Thailand

2 000 000

Costa Rica

1 881 783

Source: FAOSTAT (2008)

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6

Postharvest biology and technology of tropical and subtropical fruits Table 1.4 Top ten grape producing countries 2008 Country

Tonnes

Italy

7 793 301

China

7 284 656

United States of America

6 744 840

Spain

6 053 000

France

5 664 195

Turkey

3 918 440

Argentina

2 900 000

Iran, Islamic Republic of

2 900 000

Chile

2 350 000

Australia

1 956 790

Source: FAOSTAT (2008)

Table 1.5 Top ten orange producing countries 2008 Country

Tonnes

Brazil

18 389 752

United States of America

9 138 980

India

4 396 700

Mexico

4 306 633

China

3 454 125

Spain

3 367 000

Italy

2 527 453

Indonesia

2 322 581

Iran, Islamic Republic of

2 300 000

Egypt

2 138 425

Source: FAOSTAT (2008)

The leading grape producers of the world in 2008 were Italy (11.5% of total world grape production), China (11%), the USA (10%), Spain (9%), France (8%) and Turkey (6%). Other important grape producing countries were Argentina, Iran, Chile and Australia. The fifth major fruit produced in 2008 was oranges, with Brazil producing 27% of the global total, while 13.5% was contributed by the USA, and 6.5% by India. Mexico, China, Spain, Italy and Indonesia were among the other major orange producers.

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Economic importance of tropical and subtropical fruits

7

1.2.2 Contribution of agriculture to GDP The agriculture sector plays a very important role in the economic development of many countries, and especially in contributing to their GDP. In 2005 the agriculture sector was responsible for about 4% of world GDP (www.nationmaster.com) with the fruits subsector playing a significant role, particularly in less developed countries. Table 1.6 shows that the major tropical fruit production areas stretch across many developed and less-developed countries. Fruits are thus extremely important as they can provide a major source of income to many nations as well as employment for the population of those countries. Less-developed countries including Ethiopia, the Republic of Congo and Sudan still depend on agricultural activities, including fruit production, as a major contributor to their GDP (see Table 1.7), with the agriculture sector generally responsible for about 30–55% of their GDP. Developing countries such as Vietnam, Pakistan, Syria, India, Bangladesh, Tanzania and Indonesia are increasingly coming to depend less on the agriculture sector, including fruit production, with around 18–30% of their GDP currently provided by agricultural activities; this figure is expected to continue to fall. Many developed countries are also major fruit producers, in particular, Japan, the EU countries and the USA, which is a leading producer and

Table 1.6

Production of major tropical and subtropical fruits in 2000

Fruit

World production (’000 t)

Important producing countries

Orange

66 055

Brazil, United States, India, Mexico, Spain, China, Italy, Egypt, Pakistan, Greece, South Africa

Banana

58 687

Burundi, Nigeria, Costa Rica, Mexico, Colombia, Ecuador, Brazil, India, Indonesia, Philippines, Papua New Guinea, Spain

Coconut

48 375

Indonesia, Philippines, India, Sri Lanka, Brazil, Thailand, Mexico, Vietnam, Malaysia, Papua New Guinea

Plantain

30 583

Colombia, Ecuador, Peru, Venezuela, Ivory Coast, Cameroon, Sri Lanka, Myanmar

Mango

24 975

India, Indonesia, Philippines, Thailand, Mexico, Haiti, Brazil, Nigeria

Pineapple 13 455

Philippines, India, Indonesia, China, Brazil, United States, Mexico, Nigeria, Vietnam

Papaya

8 426

Nigeria, Mexico, Brazil, China, India, Indonesia, Thailand, Sri Lanka

Avocado

2 331

Mexico, United States, Dominican Republic, Brazil, Colombia, Chile, South Africa, Indonesia, Israel, Spain

Source: http://www.fao.org

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Postharvest biology and technology of tropical and subtropical fruits

Table 1.7

Contribution of agriculture to Gross Domestic Product (GDP)

Country

GDP of agriculture (%)

GDP of industry (%)

GDP of services (%)

Congo, Dem Rep

55.0

11.0

34.0

Ethiopia

44.9

12.8

42.3

Sudan

31.0

34.7

34.3

Tanzania

27.1

22.5

50.4

Vietnam

22.0

39.9

38.1

Pakistan

20.4

26.6

53.0

Bangladesh

19.1

28.6

52.3

Syrian Arab Republic

18.5

26.9

54.6

India

17.6

29.0

53.4

Philippines

14.7

31.6

53.7

Guatemala

13.1

25.0

61.9

China

11.3

48.6

40.1

Malaysia

10.1

43.7

46.3

European Union

2.0

27.1

70.9

Japan

1.5

26.3

72.3

United States

1.2

19.2

79.6

Source: www.nationmaster.com

exporter of citrus fruits. Dependence on agriculture is lower in developed countries, with only around 1–2% of their GDP generally contributed by the agriculture sector. Although the percentage contribution of this sector to GDP is low, the production value is higher than in most developing and less-developed countries. 1.2.3

Contribution of agriculture to employment compared to other sectors It is expected that employment activities will have a direct effect upon the composition of a country’s GDP. In less-developed countries including Ethiopia, the Republic of Congo and Sudan it is likely that a major proportion of the labour force will be employed in agricultural activities. Indeed, as can be seen in Table 1.8, about 80% of the labour force of these countries is involved in the agriculture sector (which includes the fruit production subsector). Meanwhile, only 13% are employed in the service sector, and 7% in industry. On the other hand, developing nations like Guatemala have only about 50% of their labour force in the agricultural sector, with a similar trend observed in other countries such as Vietnam, India and Bangladesh.

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Economic importance of tropical and subtropical fruits Table 1.8

9

Contribution of agriculture sector to employment

Country

Employment in agriculture (%)

Employment in industry (%)

Employment in services (%)

Ethiopia

80.2

6.6

13.2

Tanzania

80.0

20.0

0.0

Sudan

80.0

7.0

13.0

Bangladesh

63.0

11.0

26.0

India

60.0

12.0

28.0

Vietnam

55.6

18.9

25.5

Guatemala

50.0

15.0

35.0

Pakistan

43.0

20.3

36.6

China

43.0

25.0

32.0

Philippines

35.0

15.0

50.0

Syrian Arab Republic

19.2

14.5

66.3

Malaysia

13.0

36.0

51.0

European Union

5.6

27.7

66.7

Japan

4.4

27.9

66.4

United States

0.6

22.6

76.8

Source: www.cia.gov

Developed countries including the USA, Japan and EU countries have consistently maintained a small labour force – only around 1–5% of the total – in agriculture. These figures indicate that developed countries are able to make use of advanced technology in fruit production methods (and in agriculture in general), while lessdeveloped countries still rely on a large workforce.

1.3

Global consumption of tropical and subtropical fruits

Fruits are consumed in different forms around the world: some are consumed fresh, while others are used as animal feed or in making processed products such as dried and canned fruit and pickles. There are four categories of fruit usage: animal feed, processing, food and other usages, with food being the most popular form of consumption. The 2005 FAO world food balance sheets (source: FAOSTAT), show that out of a total fruit supply of 517 million tonnes, 5 million tonnes were used as animal feed, 53 million tonnes were processed, 415 million tonnes were used as food and the remaining 44 million tonnes were used in various other ways. In the same year, Asia consumed 233 million tonnes of fruit; the Americas consumed 116 million tonnes, Europe 101 million tonnes, Africa 63 million

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Postharvest biology and technology of tropical and subtropical fruits

tonnes and Oceania 5 million tonnes. In all continents except Oceania the majority was used as food: 87% in Asia, 80% in the Americas, 77% in Africa and almost 67% in Europe. In Oceania 41% of fruits were processed, with a relatively large percentage also being processed in Europe. On the other hand, close to 4% of the fruits consumed in Africa was used as animal feed. Table 1.9 provides a detailed breakdown of fruit consumption. The world average per capita fruit consumption in 2003 was 78 kg (FAOSTAT), but the figures for individual countries vary considerably, from 1 kg to 317 kg per capita annually. These figures are shown in Table 1.10. The Americas have the highest per capita consumption of any continent, at 105.6 kg, followed by Europe at 92.5 kg, Africa at 53.4 kg, and Asia at 52.5 kg.

1.4

International trade in tropical and subtropical fruit

The market demand for fresh horticultural produce has been growing steadily since the 1980s. International trade in fruits and vegetables has expanded rapidly over the past two decades compared to trade in other agricultural commodities. FAOSTAT figures show that in 2005 around 44% of the world’s acreage of fruit production was in Asia, but the quantity of export of fruits from Asia was only 19% of the world market, lagging behind the export quantities of other major fruit-producing regions such as the Americas, which took a 41% share of global exports and Europe, which provides a 33% share. (The remaining exports came from Africa and Oceania.) The EU is the leading destination of temperate and subtropical fruit exports in the global fruit trade, and is also the principal source of supply. During 1999– 2001, EU countries accounted for nearly 50% of the world’s imports and over 40% of the exports of temperate and subtropical fruits. The EU imports almost one-third of its fresh subtropical fruit from banana-exporting countries and from South America, while only around 0.5% of the total tropical and subtropical fresh fruit imports (along with 3.3% of fruit and vegetable juices) come from Asian countries (source: FAOSTAT). According to Filho et al. (2002), the temperate varieties of fruit mostly purchased by consumers in larger markets such as Europe and the United States dominate international trade. However, bananas were the fruit with the fastest growth in consumption during the 1990s (11% per year). The countries exporting the largest quantities of fresh fruit (counting temperate fruit together with tropical and subtropical fruit) are Spain, the United States, Italy, the Netherlands, France and Ecuador, which together account for 54% of sales by value. Main exporting countries are shown in Table 1.11. Spain is the world’s largest exporter. In total, 47% of exports come from Europe while 36% come from the United States. Germany, the United States, Britain and France import 42% of the fresh fruit traded internationally. Germany is the largest importer (16%), followed by the United States (11%). Major fruit distribution centres in Europe are the Netherlands, Belgium, Luxembourg and France. France acts as a European distribution centre for pineapples and bananas.

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203 432

21 377

233 099

Food

Other

Total

Source: FAOSTAT (2008)

7 417

873

Asia

3.18

0.37

100

9.17

87.27

%

116 550

13 482

93 446

8 459

1 163

Americas

7.26

1.00

100

11.57

80.18

%

Fruit consumption by continent in 2005 (thousand tonnes)

Process

Feed

Category

Table 1.9

101 438

4 645

67 613

28 830

350

Europe 0.35

100

4.58

66.65

28.42

%

63 560

6 259

48 698

6 216

2 387

Africa

9.78

3.76

100

9.85

76.62

%

4 978

100

2 845

2 030

3

Oceania

0.06

100

2.01

57.15

40.78

%

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292 United Kingdom

255 Germany

223 USA

222 Dominican Republic

193 Spain

182 Cyprus

178 St Kitts and Nevis 108 Seychelles

168 Turkey

167 Iceland

Belize

St Lucia

Grenada

Bahamas

Uganda

Netherlands

Samoa

Antigua and Barbuda

Ecuador

79 Azerbaijan

82 Vietnam

82 Libyan Arab Jamahiriya

103 Cameroon

157 Australia

155 Colombia

153 Philippines

152 Switzerland

150 Burundi

147 Saudi Arabia

Costa Rica

Sao Tome and Principe

Jamaica

Rwanda

Lebanon

Greece

102 New Caledonia

102 Moldova

103 Uruguay

103 Hungary

103 Estonia

105 Trinidad and Tobago

Iran, Islamic Republic of 158 Malta

105 Honduras

107 Paraguay

70 Belarus

70 Poland

71 Chile

71 Turkmenistan

29

30

30

30

31

32

33

34

Kg

49 Kyrgyzstan

49 Netherlands Antilles

52 Tanzania, United Republic of

46 Mozambique

47 Timor-Leste

47 Namibia

48 Cambodia

18

19

21

23

24

25

27

29

53 Congo, Democratic Republic of 29

53 Angola

53 Uzbekistan

54 Sudan

54 Pakistan

54 Myanmar

55 Nicaragua

55 Yemen

73 Russian Federation 48 Nepal

73 Indonesia

74 China

74 Armenia

75 Swaziland

77 Latvia

78 Kenya

112 Venezuela, Bolivarian 79 Malaysia Republic of 109 Guyana

Kg Country

83 Korea, Democratic 56 Sierra Leone People’s Republic of

Kg Country

112 Former Yugoslav 79 Japan Republic of Macedonia

113 Czech Republic

113 Peru

115 Occupied Palestinian Territory

115 Argentina

317 Sweden

Dominica

Kg Country

Kg Country

Fruit consumption (excluding wine) by country (Kg/capita/year), 2003

Country

Table 1.10

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Source: FAOSTAT (2008)

115 Syrian Arab Republic 84 Congo

Israel

85 Bosnia and Herzegovina

115 Tunisia

Bolivia

86 Slovakia

86 Georgia 86 French Polynesia

118 Panama

Ghana 85 Jordan

119 Haiti

Canada

88 Algeria

116 Comoros

120 Croatia

Mexico

89 Kiribati

90 Morocco

Portugal

120 Egypt

90 Guatemala

91 Korea, Republic of

94 Romania

94 El Salvador

95 Suriname

95 Nigeria

97 Lithuania

98 Belgium

99 Côte d’Ivoire

Serbia and Montenegro 118 Thailand

121 Maldives

130 Vanuatu

Italy

Barbados

137 Bermuda

Ireland

New Zealand

137 France

Austria

128 Finland

141 Brazil

Cuba

124 Albania

142 St Vincent and Grenadines

Slovenia

Norway

146 Brunei Darussalam

Gabon

United Arab Emirates

146 Guinea

Denmark

36 Tajikistan

37 Gambia

38 Niger

38 Burkina Faso

39 Zambia

40 Togo

40 Ethiopia

40 Bangladesh

41 Chad

41 Zimbabwe

43 Mauritania

43 Senegal

45 Lesotho

45 Kazakhstan

46 Djibouti

46 Mongolia

56 Benin

34 Eritrea

57 Lao People’s 35 Mali Democratic Republic

58 Ukraine

58 India

59 Solomon Islands

59 Malawi

60 Fiji

61 Sri Lanka

62 South Africa

62 Kuwait

63 Mauritius

64 Botswana

65 Madagascar

66 Guinea-Bissau

66 Cape Verde

66 Bulgaria

68 Liberia

69 Central African Republic

1

2

3

3

5

5

9

9

10

10

11

12

12

14

14

15

15

16

14

Postharvest biology and technology of tropical and subtropical fruits

Table 1.11

Selected top five tropical fruit exporting countries (quantity and value) 2007

Area

Quantity (tonnes)

Mango, Mangosteen and Guava India Mexico Netherlands Brazil Peru

Value (US$’000)

240 858 236 004 80 598 116 271 82 512

163 622 119 187 114 408 90 102 63 674

Pineapple Costa Rica Belgium Netherlands Philippines USA

1 353 027 263 811 190 626 270 054 89 269

486 860 268 803 194 555 147 807 88 526

Tangerine Spain China Morocco Turkey Netherlands

1 652 428 399 986 243 983 257 935 95 689

1 682 204 174 750 159 209 111 625 107 118

Papaya Mexico Brazil USA Netherlands Belize

101 306 32 267 9 604 8 625 33 341

55 327 34 404 17 715 16 907 13 101

1 167 511 5 174 565 1 793 930 2 272 332 1 639 833

1 303 559 1 282 036 856 447 675 406 531 765

484 676 288 673 177 793 168 259 79 977

191 050 179 295 91 591 87 435 54 072

Banana Belgium Ecuador Philippines Costa Rica Colombia Watermelon Mexico Spain USA Panama Netherlands Source: FAOSTAT (2008)

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Economic importance of tropical and subtropical fruits

15

Spain is the leading example of specialization. This country supplies the world table orange market, which is a niche market as most oranges are processed into juice. Spain accounts for 49% of world table orange supply. Despite the fact that its production has been declining at an annual rate of 2%, exports have risen by an average of 5% per year over the past decade. It exports close to 1.6 billion tonnes and earned US$1.6 billion from exports of tangerines in 2007. Ecuador, the world’s third largest producer of bananas, is another case of specialization. This country’s contribution to world fruit trade is limited to this crop, yet its share of the market is 17%. Due to its involvement in the banana trade, Ecuador is the world’s fourth largest international exporter of fresh fruits. The United States is the leading example of diversification, making a significant contribution to world production, import and export (with the exception of banana production). According to these authors, the US position in the orange market is particularly notable. Production has been boosted at a rate of 7% per year, while imports have fallen (by 13% per year) and exports risen (by 11% per year), in a market that has grown at 5% per year (Filho et al., 2002) According to Rabobank International, four trading companies controlled 80% of world trade in fruits in 1997. Larger players in the European and US fruit markets achieve annual revenues in excess of US$1 billion, notably the two US groups, Dole Foods (US$6.9 billion in 2007) and Chiquita (US$3.6 billion in 2008) (www.unctad.org/infocomm/francais/orange/Doc/brazil.pdf). The World Trade Organization (WTO) agreement reached in Marrakesh on 15 April 1994, which followed the conclusion of the Uruguayan Round of the General Agreement on Tariffs and Trade (GATT) talks is particularly relevant for the development of trade in tropical and subtropical fruit. According to Katz and Weaver (2003), these agreements essentially established the principle of free trade not exposed to arbitrary market entrance taxes, and furthermore obligate signatory countries to use only sanitary and phytosanitary quarantine measures based on solid scientific information. Therefore the use of these measures as a loophole to arbitrarily restrict imports was effectively halted.

1.5

Price of tropical and subtropical fruit

1.5.1 Price trends of selected fruits The increased awareness of the health benefits of fruit consumption in the 1980s has led to an expansion of fruit trade especially from developed countries. This resulted in a double-digit growth in the export of mangoes and avocados during 1989–2001, while the overall fruit exports grew by 4.2% during the same period. Most tropical fruit exporting countries have taken advantage of the growing fruit trade, with Thailand, China and the Philippines taking the lead for Asian production. The expansion in production and supply exerted a downward pressure on prices and tended to depress margins due to intense competition among exporting developing countries. Mangoes are a prime example of this, with prices in Europe falling by 30% since 1988 in conjunction with a 66% increase in import volumes.

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Postharvest biology and technology of tropical and subtropical fruits

Table 1.12

Papaya Pineapple Tangerine Lemon Orange Banana Pomelo Watermelon

Price trends of selected tropical fruits 2003

2004

2005

2006

2007

Average price

351 481 426 461 390 360 336 223

443 489 447 434 403 379 341 245

607 547 493 447 460 430 367 266

695 653 528 507 509 472 415 279

1038 723 593 588 508 560 446 309

627 579 497 487 454 440 381 264

Source: FAOSTAT (2008)

But since 2000, the prices of most tropical fruits have recovered, changing the overall market scenario for certain fruits (Sing Ching Tongdee, 2004). As can be seen from Table 1.12, despite the differences in price received by fruit producers, the general trend of world fruit prices has shown a consistent increasing trend since 2003. The price of papaya has increased from US$351/ tonne in 2003 to US$1038/tonne in 2007 while pineapple prices have increased from US$481 to US$723/tonne during the same period. Among the citrus fruits, tangerine prices have increased from US$426/tonne to US$593/tonne during 2003 to 2007. The average prices of selected popular fruits have ranged from US$264 to US$627/tonne as shown in Table 1.12: papaya and pineapple have always commanded higher prices as compared to pomelo and watermelon. 1.5.2 Demand and supply of tropical and subtropical fruit There have been several studies on the price demand elasticities for tropical and subtropical fruits. Most of the studies have analysed the demand and expenditure/ income elasticities for some of the more popular tropical fruits. It is expected that when prices increase, consumer demand will decrease and similarly, when prices decrease, consumer demand will increase, provided that other variables that can influence demand remain constant. If the price elasticity is elastic it means that consumer demand is very responsive to price changes. For example, if the price decreases by 1%, demand will increase by more than 1%, and if the price increases by 1%, demand will decrease by more than 1%. Similarly, expenditure/income elasticity measures changes in consumer demand caused by changes in income. It is expected that demand will increase when income increases. It is important to understand the concept of price and income elasticities as they have the potential to influence demand for fruits in the global market. Fatimah et al. (2005) analysed the Malaysian household budget and estimated income elasticities for the individual fruits. Fruits are generally considered to be a complementary product with respect to all other food items. Starfruit has the highest income elasticity, at 1.104, suggesting that as Malaysian household

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incomes rise by 1%, the budget share of starfruit will rise by 1.104%. In other words, Malaysian consumers will consume more fruits as per capita income increases. Melon and jackfruit have the lowest income elasticities, at 0.257 and 0.225 respectively. In general, the income elasticities of imported fruits and processed fruits are higher than those of local fruits. Among the imported fruits, grape has the highest income elasticity of 0.961, while processed fruits have an elasticity of 0.918. Mubarak et al. (2006) studied the demand elasticities for fruits and vegetables in Vietnam. The own-price elasticities of cereals and vegetables are inelastic, implying that they are an integral part of the Vietnamese diet. Fruits have an ownprice elasticity of −0.55, indicating that consumers in Vietnam are not very responsive to changes in fruit prices. The elasticity implies that as price of fruits decreases by 1%, the demand for fruits will increase by only 0.55%. The cross price elasticities were mostly negative, suggesting separability among the food groups. Dong et al. (2009) used retail purchase data to investigate the US demand for organic and conventional fresh fruits. All expenditure elasticities are positive, ranging from 0.81 for organic bananas to 1.03 for organic oranges and from 0.98 for conventional bananas to 1.01 for other major conventional fruits. The results show that the expenditure elasticities for organic and conventional fruits tend to be close to unity, implying that given an increase in the spending on fresh fruits, consumers would allocate approximately the same proportional increase to their purchase of conventional and organic fresh fruits. Thus, households with higher incomes are more likely to purchase some organic fruits and spend more on fresh fruits as a whole. An FAO study (Anon., 1998) estimated elasticity (own-price, cross-price and income) for three major fresh tropical fruits (mangoes, avocados and papayas). Results indicate that consumers in all three markets – the USA, the EU and Japan – react quite strongly to price changes affecting these fruits. By contrast, for fruits with smaller volumes (mangosteens, longans and litchis), consumption was price inelastic in most markets. Similarly, substitution and income effects of the fruits were significant factors affecting consumption. As can be seen in Table 1.13, of the three fruits imported to Europe, papaya was the most responsive to a change in its own price (own price elasticity of −2.73), indicating that as price decreases by 1%, the demand for papaya will increase by 2.73%. Similarly the cross-price elasticity of papaya with other fruits is elastic, implying that as the prices of other fruits increase, the demand for papaya will also increase. Thus, there is a substitutability effect between papaya and other fruits (cross-price elasticity of 1.92) indicating that as the prices of other fruits increase, consumer demand for papaya will also increase. In the EU, the demand response to an increase in income results in a significant increase in demand for avocados and mangoes, but not for papayas. Consumer response to price changes in the United States differed from that observed in other markets. Own-price elasticities were much lower for papayas at −0.07, while avocados proved more price elastic at −1.48. Cross-price elasticities

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Table 1.13

Estimated own-price, cross-price and income elasticities EC’s import demand

Avocados Mangoes Papayas

Own-price −2.58 −2.49 −2.73

Cross-price 1.07 1.78 1.92

Income 1.74 1.73 0.66

United States import demand Avocados Mangoes Papayas

Own-price −1.48 −0.74 −0.07

Cross-price 0.34 5.59 2.20

Income 3.23 1.39 0.91

Japan’s import demand Avocados Mangoes Papayas

Own-price −2.01 −1.41 −2.95

Cross-price 0.20 0.34 0.95

Income 1.22 3.23 0.4

Source: Dong and Lin (2009)

for mangoes were surprisingly high at 5.59. As expected, the income effect was low for papayas and highest for avocados, with mangoes in-between. In Japan, the own price elasticities for avocados, mangoes and papayas are highly sensitive to price changes, particularly papayas (−2.95). Of the three major markets, the Japanese market shows the lowest cross-price effects, indicating that these fruits have few substitutes. The response to income changes is again highest for mangoes and lowest for papayas. Similar results were observed for papayas in all three markets. However, for avocados and mangoes, the demand response to increases or decreases in income differed across the three markets. In Japan, the highest demand response was for mangoes, while in the United States it was for avocados; in the EU, mangoes and avocados showed similar results.

1.6

Conclusions

In general there has been an increasing trend towards greater production of major tropical and subtropical fruits over the years. This could be due to higher productivity or alternatively could be the result of fruits being cultivated in more areas. The per capita consumption of fruits varies considerably between countries, with the highest being 317 kg per capita and the lowest 1 kg per capita. It is interesting to note that there is no clear correlation between per capita consumption figures and the level of economic development of a country or region: in some less-developed regions the per capita consumption of fruits is in fact higher than

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in some developed regions. Thus, there is potential for the tropical and subtropical fruits industry to expand or to increase its market share in developed and developing regions. For example, per capita consumption in Japan and Kuwait – categorised as developed countries – is only 54 and 40 kg per capita respectively. Given the right promotion and compliance with trade regulations and the nontariff barrier (NTB), the consumption of fruits in such countries could be increased in the future. In less-developed nations such as Togo, Niger and Mali, which have lower levels of consumption, educational and promotional programmers need to be put in place in order to increase fruit consumption among the population. This is particularly important since fruits are considered to be one of the principal sources of the vitamins and minerals necessary for a healthy diet. Asia contributes almost half of the world production of tropical and subtropical fruits, with China producing the largest share of any country. About 30% is contributed by the Americas, and the rest is shared between other parts of the world. The most popular fruits both in terms of production and consumption include watermelons, bananas, grapes, oranges, mangoes, tangerines, pineapple, papaya, citrus and dates, to name a few. Most of these fruits are found in subtropical regions. The cultivation of fruits forms part of the agricultural activities of a country and makes an extremely important contribution to GDP and employment levels, especially among the less developed nations which still depend on agriculture as their main economic activity. For example, in Ethiopia, the Republic of Congo and Sudan about 80% of the population is engaged in agriculture, while nations such as the US, Japan and the EU countries are less dependent on agriculture, which contributes only around 1–2% of their GDP. Although Asia is the largest producer of tropical and subtropical fruits, exports from Asia account for only about 19% of the world market, possibly due to the high consumption levels among the Asian population. About 41% of global exports come from the Americas, with Dole Foods, Chiquita and Del Monte among the major players in the fruits market. In general, the price demand elasticities of most fruits are price elastic, indicating that consumer demand for fruits is responsive to price fluctuations. An increase in prices will usually cause the demand to decrease, and a decrease in prices will cause demand to increase. Thus setting prices for fruits is crucial in ensuring an adequate level of consumer demand: there are always substitute products for fruits, and unlike tubers and grains, fruit is not a staple food in most parts of the world.

1.7

References

Anon (1998), Committee on commodity problems: Sub-group on tropical fruits: First session: Pattaya, Thailand, 25–28 May 1998: Supply and demand prospects. Available from: www.fao.org/unfao/bodies/CCP/ba-tf/1998/TF98-3E.HTM#P22_30 [accessed 23.2.11]. Anang, S. and Chan, Y. K. (1999). Recent Developments of the Fruit Industry In Malaysia. Paper presented at the FAO–IGG on Bananas and on Tropical Fruits. Gold Coast, Australia, 4–8 May, 1999.

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Dong, D. and Lin, B. H. (2009). Fruit and Vegetable Consumption by Low-income Americans: Would a Price Reduction Make a Difference? Economic Research Report No. 70, 23 pp., January 2009. FAOSTAT (2008, 2010) http://faostat.fao.org. Fatimah, M. A., Alias, R. and Zainalabidin, M. (2005). The Fruit Industry In Malaysia: Issues and Challenges. University Putra Malaysia Press. Filho, P.F., Ormond, J.G.P. and Sergio Roberto Lima de Paula, S.R. (2002). Brazilian Fruit Production: In Search of an Export Model. United Nations Conference on Trade and Development. Available from: www.unctad.org/infocomm/francais/orange/Doc/brazil. pdf [accessed 23.2.11]. Katz, S. H., and Weaver, W. W. (2003). Encyclopedia of Food and Culture. New York: Scribner. Mubarik, A., Nguyen, T. Q. and Ngo, V. N. (2006). Analysis of Food Demand Patterns in Hanoi: Predicting The Structural and Qualitative Changes. AVRDC Technical Bulletin 35. World Vegetable Center, Shanhua, Taiwan. Sing Ching Tongdee (2004). Horticultural Crop Production and Marketing Decision Influencing Postharvest Technology, Extension Bulletin 545, Food and Fertilizer Technology Center, Republic of China. TFNet (2003). Global overview of tropical and subtropical fruits: future potential and challenges.

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2 Nutritional and health-promoting properties of tropical and subtropical fruits E. M. Yahia, Autonomous University of Queretaro, Mexico and J. De Jesus Ornelas-Paz and G. A. Gonzalez-Aguilar, Research Center for Food and Development, Mexico

Abstract: A worldwide increase in the consumption of tropical and subtropical fruits has been observed recently. These fruits are very diverse and contain many nutritional components that have been associated with the prevention of diseases such as cancer and cardiovascular disease, among others. This chapter lists and describes some of the important nutritional components of tropical and subtropical fruits and their effects on health. The effects of pre- and postharvest treatments on the nutritional components of tropical and subtropical fruits are also discussed, including the effects of postharvest preservation technologies and processing. The effects of these compounds on human nutrition and health are emphasized, analyzing the mechanisms involved in their protective actions. Finally, the synergistic effect of the multiple bioactive fruit components is presented, as pure bioactive compounds do not exert the same health effects as the actual consumption of tropical and subtropical fruits. Key words: postharvest, vitamins, minerals, fiber, pigments, antioxidants, phenolics, degenerative diseases, cancer, cardiovascular diseases, nutraceuticals.

2.1

Introduction

Increasing incidences of some chronic diseases such as cancer and cardiovascular problems have raised awareness of the importance of diet (Erbersdobler, 2003). Numerous epidemiological studies suggest that abstaining from smoking, increasing intake of fruits and vegetables, and preventing infectious diseases can have a major effect on reducing rates of several chronic diseases including

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cardiovascular disease and different types of cancer (Percival et al., 2006; Yahia, 2010). Therefore, interest in the health benefits of fruit and vegetable consumption, and in understanding the mechanism and mode of action of the different components that confer health benefits, is increasing. Fruits are considered rich sources of some essential dietary micronutrients, fibers, and more recently they have been recognized as important sources of phytochemicals that individually, or in combination, may benefit health (Table 2.1) (Rechkemmer, 2001; Yahia, 2010). The nutritional compounds and phytochemicals present in tropical and subtropical fruits are very diverse and often include ascorbic acid, carotenoids and phenolic compounds (Table 2.1) (Percival et al., 2006; Yahia, 2010). They have considerable antioxidative activity in vitro which can have important implications for health. A diet rich in fruits and vegetables increases antioxidants concentration in blood and body tissues, and potentially protects against oxidative damage to cells and tissues (Yahia, 2010). However, other more complex mechanisms also seem to be involved in the protective effects of these compounds (Yahia and Ornelas-Paz, 2010). Clarification of the potential protective roles of specific antioxidants and other constituents of tropical and subtropical fruits deserves major attention.

Table 2.1 Some nutrients and phytochemicals in some tropical and subtropical fruits that were established or proposed to have a positive effect on human health (modified from Kader, 2001) Nutrient/phytochemical

Source

Established or proposed effects

Vitamin C (ascorbic acid)

Cantaloupe, citrus fruits, guava, pineapple, mango, papaya

Vitamin A (carotenoids)

Orange-fleshed fruits such as papaya, mango, pineapple, citrus

Vitamin K

Nuts

Vitamin E (tocopherols)

Nuts, avocados, olives

Fiber Folate (folicin or folic acid)

Most fruits and nuts

Calcium

Almonds, orange, raisin, papaya Banana, nuts Banana, plantain, cantaloupe

Prevents scurvy, aids wound healing, healthy immune system, cardiovascular disease Night blindness prevention, chronic fatigue, psoriasis, heart disease, stroke, cataracts Synthesis of procoagulant factors, oesteoporosis Heart disease, LDL-oxidation, immune system, diabetes, cancer Diabetes, heart disease Birth defects, cancer, heart disease, nervous system Osteoporosis, muscular/ skeletal, teeth, blood pressure Osteoporosis, nervous system, teeth, immune system Hypertension, nervous system, teeth, immune system

Pomegranates

Cancer

Magnesium Potassium Phenolic compounds Proanthocyanins: tannins

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Anthocyanidins: cyanidin, malvidin, delphinidin, pelargonidin, penidin, petunidin Flavan-3-ol: epicatechin, epigallocatechin, catechin, gallocatechin Flavonones: hesperetin, naringenin, eriodictyol Flavones: luteolin, apigenin

Grape, pomegranate

Heart disease, cancer initiation, diabetes, cataracts, blood pressure, allergies

Mango

Platelet aggregation, cancer

Citrus fruits

Cancer

Guava

Flavonols: quercetin, kaempferol, myricetin, rutin

Papaya

Cancer, allergies, heart disease Heart disease, cancer initiation, capillary protectant Cancer, cholesterol

Phenolic acids: caffeic acid, chlorogenic acid, coumaric acid, ellagic acid Carotenoids Lycopene β-Carotene

Papaya, Brazilian guava, red grapefruit Mango, cantaloupe, papaya

Xanthophylls: lutein, zeaxanthin, β-cryptoxanthin α-Carotene Monoterpenes: limonene Sulfur compounds: glucosinolates, isothiocyanates, indoles, allicin, diallyl disulphide

Cancer, heart disease, male infertility Cancer Macular degeneration

Cantaloupe, kiwifruit, mango, papaya, Citrus (grapefruit, tangerine) Brassicas

Tumor growth Cancer Cancer, cholesterol, blood pressure, diabetes

It is argued that increasing intake of fruits and vegetables to 400–800 g per day is an adequate public health strategy. For this reason, the World Health Organization (WHO) recommends a daily intake of at least 400 g of fruits and vegetables per person, and health authorities worldwide follow this recommendation. This recommendation has been very difficult to reach in both developed and developing countries due to several reasons. The implementation of policies either at the economic, sanitary, trade or health level may help to reach this goal. With regard to plant physiology, several factors affect the synthesis and metabolism of bioactive compounds in tropical and subtropical fruits. Climatic conditions, especially temperature and light, have major effects both before and after harvest. Factors such as soil type, irrigation, fertilization, mulching, rootstocks, and several other cultural practices are of great importance (Goldmann et al., 1999). Maturity at harvest, harvesting methods, precooling, delays between harvest and consumption or processing, and several postharvest techniques (such as refrigeration, heat treatments, modified and controlled atmospheres, processing

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techniques, and cooking) are other factors that can have major effects on nutritional and health components (Kader, 2001; Yahia, 2010). This chapter will highlight the potential nutritional and health importance of tropical and subtropical fruit.

2.2

Consumption

Despite the relatively low caloric values of tropical and subtropical fruits (banana, plantain and avocado are the notable exceptions), they play an important role in human diet mainly because of their high and diverse content of vitamins, minerals and bioactive compounds. They have been of key importance in the tropics, being a large component of the diet there since ancient times, either by collecting fruit from the wild or by cultivating plants. More recently, they have also become an important part of the diet of people in developed countries, especially due to health and fitness consciousness. Whether these fruits are chosen as a healthy choice or a staple food they have excellent nutritional and health components. Nutritionists have long recommended a minimum of 400 g of fruit per day, and that it should be as varied as possible. Toward the end of the twentieth century marketing campaigns commonly recommended consumption of five fruit portions per day, which, while it may have more to do with commerce than with science, does reinforce the value of fruit as a part of the human diet. Collection and transport from the field to the storage facility or marketplace do not significantly deplete the nutritional and organoleptic properties or the antioxidant capacity of fruits. This is not the case, however, for fruits that undergo lengthy storage duration, since several components such as vitamins and polyphenols are quite sensitive to modifications of enzymatic oxidases and chemical oxidation occurring during storage. The control of environmental conditions and the extent of the storage time of fresh fruits represent important steps for maintaining their nutritional quality (Ninfali and Bacchiocca, 2004). Tropical and subtropical fruits are usually consumed fresh, although there are a few exceptions such as the case of breadfruit which is only eaten cooked. Nuts can be eaten directly or processed (roasted, candied). Salads, both savory and sweet types, are prepared with many tropical and subtropical fruits. Several processed products are made from fresh tropical and subtropical fruits, and include jams, jellies, juices, sauces, ice cream and sherbets, and other desserts and diverse confectionary items, infusions such as social beverages, medicinal remedies, etc. Baby foods are made with ‘healthy’ fruits like banana and mango, based on different kinds of puree. Flour is also made from some tropical and subtropical fruits such as durian, banana and plantain. Consumption of flour from mango kernels has been practiced for a long time in India. Pickles and chutneys are made from many fruits, the most famous being mango chutney, a staple in South Asian cuisine. Dips are also popular in many countries, of which the best known is avocado-based guacamole. Guava paste or spread is consumed, usually with bread and cheese, in many countries, particularly in Cuba, Brazil and the Canary Islands.

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Health components of tropical and subtropical fruits

Tropical and subtropical fruits are rich sources of different nutrients and also have some medicinal properties. Many tropical fruits, notably mango and papaya, are good sources of β-carotene (provitamin A). An indication of the high content of this vitamin is the orange-yellow color of the flesh. Others, including all citrus fruits and the guava, are well known as good sources of ascorbic acid (vitamin C). In general they are not a good source of the B-group vitamins (thiamine, riboflavin and niacin) except for nuts, which are also a good source of vitamin E, proteins and fats (Yahia, 2011a). Tropical and subtropical fruits are also rich in pectin, fiber and cellulase, which promote intestinal motility. In common with other fruits, they are good sources of antioxidants, and some are also good sources of organic acids, which stimulate appetite and aid digestion. Nuts and banana have high calorie content. Avocado has a high oil content (of the different avocado races, the West Indian types have the lowest) composed of highly digestible unsaturated fatty acids, rich in folic acid, and some cultivars contain good quantities of proteins, vitamin A, riboflavin, and phosphorus (Whiley and Schaffer, 2006). Fruits with greater caloric content such as the macadamia nut are also rich in protein, oil, iron, calcium, thiamine, riboflavin and niacin. Guava, which is high in vitamin C, also has good amounts of niacin and iron. Papaya has high quantities of vitamins C and A as well as potassium and calcium, and it is low in carbohydrates. However, its outstanding feature, which distinguishes the papaya from all other fruits, is the fact that it contains papain, a proteolytic enzyme that promotes digestion (although papain content decreases as the fruit ripens). It is highly recommended for people with certain digestive disorders. Passion fruit is rich in provitamin A and carbohydrates and is an acceptable source of vitamin C and niacin. The pineapple is also rich in vitamin C and carbohydrates and is a good source of calcium, phosphorus, iron, potassium and thiamine (Yahia, 2010). The litchi, the longan, most of the Annonaceae, and the durian are all good sources of carbohydrates and vitamin C. The durian also has fair amounts of iron and niacin. Mangosteen is considered by many to be one of the finest tasting fruits of all, and therefore it is known as ‘queen of fruits’ (Yaacob and Tindall, 1995). Although it has a comparatively low nutrititional value, it has reasonable amounts of calcium, phosphorus, ascorbic acid and carbohydrates. The carambola is low in calories and rich in vitamin C, and it is an adequate source of vitamin A. It is not recommended for people with kidney problems (specifically stone formation) due to its high oxalic acid content, but new cultivars have been selected for lower oxalic content while maintaining sugar and vitamin levels (Galán-Saúco, 2002). Dates are rich in carbohydrates, a good source of vitamin A, potassium and iron, but low in fat and sodium. The coconut is high in phosphorus, iron, proteins and fats – in this case all saturated fatty acids, the consumption of which should be limited according to health recommendations. Coconut milk aids in balancing pH in the body due to its alkaline reaction. The next section describes in detail the effect of vitamins, fiber and minerals of importance in tropical fruits on consumers’ health.

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2.3.1 Vitamins Vitamin A Vitamin A includes a group of natural and synthetic compounds, generically named retinoids. Major retinoids and their metabolites are all-trans-retinol, 3,4-didehydroretinol, all-trans-retinal, 11-cis-retinal, all-trans-retinoic acid, 9-cis-retinoic acid and retinoyl-β-glucuronide (Yahia and Ornelas-Paz, 2010). Fruits do not contain vitamin A; however, they are rich in carotenoids, which are precursors of this vitamin. Only carotenoids containing a β-ionone ring without oxygenated groups can be considered precursors of vitamin A. The main dietary provitamin A carotenoids are β-carotene (the major precursor), α-carotene and β-cryptoxanthin. Generally, fruits and vegetables provide 25–35% of total retinol intake. The content of provitamin A carotenoids and the vitamin A value of tropical and subtropical fruits are shown in Tables 2.2 and 2.3. It must be noted that carotenoids from tropical fruits are up to four times more bioavailable than those from vegetables (De Pee et al., 1998). Recently, Ornelas-Paz et al. (2010) demonstrated in experimental rats that vitamin A content derived from β-carotene from ‘Ataulfo’ mango is 1.5 times higher than that from carrots. Differences in the method of carotenoids storage in the cells of fruits and vegetables seem to be Table 2.2 Content (μg 100 g−1) of provitamin A carotenoids in some tropical and subtropical fruits Fruit

β-carotene

α-carotene

Lutein+zeaxanthin

β-cryptoxanthin

Avocado Banana Cantaloupe Carambola Fig Grape Grapefruit Guava Honeydew Key lime Kiwifruit Mandarin Mango Muskmelon Orange Papaya Passion fruit Peach Pineapple Prickly pear Soursop Tamarind Watermelon

62 26 2020 25 85 39 14–686 374 30 30 43–52 155 445 0–2020 71 55 743 30–1480 31–35 25 1 18 303

24 25 16 24 0 1 3–8

271 22 26 66 9 72 5–10 0 27 0 114–122 138 0 26 129 75 0 9–112 0

28

0 0 0 101 17 0–16 11 0 0 0–9 0 0 0 0

1 0 0.11 0 3–6 0.73 0 1.4 407 11 0–1 11.6 761 41 12–510 3

0 8

Sources: USDA, 2005; van den Berg et al., 2000

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0.05–0.1 0.02–0.19 0.11 0.03 0.02 0–0.02 0.01–0.5 0.01–0.06 0.01–0.069 0.034–0.043 0.03–0.07 0.02–0.04 0.02–0.024 0.02–0.09 0.02–0.04 0.04–0.11 0.03–0.06 0.04–0.05 0.04–0.1 0.027–0.03 0–0.01 0.078–0.09 0–0.09 0.01–0.06 0.01–0.014 0.04–0.07 0.2–0.43 0.02–0.08

Avocado Banana Bitter orange Black sapote Blackberry Chico sapote Coconut Fig Grape Grapefruit Guava Key lime Kiwifruit Lemon Mamey Mandarin Mango Muskmelon Orange Papaya Passionfruit Pineapple Pomegranate Pomelo Prickly pear Soursop Tamarind Watermelon

Note: 1International units Source: USDA, 2005

Thiamin (mg)

Fruit

Riboflavin (mg)

0.2–0.14 0.03–0.026 0.03 0.04 0.03–0.04 0.02–0.09 0.01–0.1 0–0.05 0.01–0.13 0.01–0.031 0.03–0.06 0.01–0.06 0.02–0.05 0.01–0.06 0.03–0.06 0.02–0.08 0.02–0.11 0.019–0.04 0.01–0.12 0.02–0.07 0.13–0.17 0.029–0.05 0.1–0.13 0.02–0.07 0.02–0.06 0.05–0.07 0.15–0.19 0.01–0.04

Niacin (mg) 1–2.9 0.4–1 0.4 0.04 0.02–0.4 0.2–0.6 0.1–2.3 0.3–0.7 0.1–0.5 0.19–0.26 0.4–1.4 0.2–1.3 0.28–0.5 0.2–0.6 0.4–1.5 0.1–2 0.2–0.6 0.23–0.9 0.1–0.5 0.3–0.4 0.8–1.5 0.2–0.57 0.2–1.6 0.2–0.6 0.3–0.5 0.6–1.7 0.7–2.5 0–0.2

Vitamin C (mg) 8–15 1.1–15 51 21 15–83 8.9–14.7 0–4.5 0.6–15 1.4–11 31.2–50.6 7.2–250 21–45 92.7–98 30–77 14–59 23–72 19–80 14.8–74 42.2–92.3 31.2–75 20–237 10–56.4 5–30 25–53 9–25.5 19–21 1–20 3–10 0.037 0.05 0.11 0.086 0.042–0.053 0.11 0.04 0.05–0.06

0.257 0.36

0.25 0.14 0.22

0.06 0.05 0.06 0.04

0.1 0.07 0.13 0.07–0.16 0.05–0.063 0.019 0.1 0.19–0.217 0.106–0.114 0.37 0.07

0.1 0.21 0.16 0.084–0.1 0.25 0.21

0.25 0.3 0.3 0.05 0.26–0.283 0.45 0.12 0.18–0.5

1.389 0.33

Pantothenic acid (mg)

Vitamin content in some tropical and subtropical fruits per 100 g of fresh tissue Vitamin B-6 (mg)

Table 2.3 Total folates (μg) 6 14 14 3

14 16 14 8–21 17–39 38 14 11–19 38

14 26 6 2 9–13 49 8 25–34

81 20

Choline (mg) 7.6 8.6 4.1

10.2 7.6 7.6 8.4 6.1 7.6 5.4–5.6 7.6

12.1 4.7 5.6 7.7 7.6 5.1 5–7.8

14.2 9.8

Vitamin A, IU1 2.07 0.1

43 2 30 569

230 681 765 0–3382 225–230 1094 1272 52–58

0.8 0.1 0.05

0.2 1.1 0.05 0.18 0.73 0.02 0.02 0.6

21 0.5

0

0

0.11

0

0.4 2.8 0.1

4.2 2.5 0 2.6 0.7 0.7 16.4

0.2 4.7 0.07 14.6 0 0 2.6 0.6 0.01–0.03 5.5–40.3

0.53

0.33 0.02

Vitamin E (α-tocopherol) (mg) Vitamin E (γ-tocopherol, mg)

0.24 142 66 0.19 10–1150 0.13 624 50 0.22 72–87

60

146 64

Vitamin K (phylloquinone) (μg)

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responsible for these results. Vitamin A and its bioactive metabolites exert pleiotropic effects in vertebrate organisms, modulating cell development, proliferation, metabolism and apoptosis (Wolf, 1984). Vitamin A is needed for growth (Hadi et al., 2000) and is essential for reproduction (Clagett-Dame and DeLuca, 2002). This vitamin is important in the visual process and prevents several diseases of the eye, including night blindness, xeroftalmy, conjunctive xerosis and corneal diseases (Krinsky et al., 2003). Vitamin A is also involved in immune function (Humphrey et al., 2006). Other biological actions of vitamin A have been described elsewhere, including its anticancer effects (Wolf, 1984). Vitamin C Vitamin C or ascorbic acid has long been known for its ability to cure and prevent scurvy. Dehydroascorbic acid, the oxidized form of ascorbic acid, retains vitamin C activity (Johnston et al., 2007). This vitamin is biosynthesized by plants and the majority of vertebrates. A few mammalian species (primates, humans, guinea pigs, etc.) are unable to biosynthesize ascorbic acid and therefore they have to take it from dietary sources. Ascorbic acid is biosynthesized from carbohydrates (Davey et al., 2000). Tropical and subtropical fruits are rich in ascorbic acid. Acerola fruit contains the highest known ascorbic acid content among all fruits (1000–3300 mg 100 gm−1 fresh weight), and some other good sources of vitamin C include guava, litchi, papaya and passion fruit (Yahia, 2006). Mango fruit is also a rich source of vitamin C (Carrillo-Lopez et al., 2010; Siddappa and Bhatia, 1954; Thomas, 1975; Yahia, 2006). Citrus fruit and their juices are rich sources of vitamin C: an 8 fl-oz serving of citrus juice was reported to supply the entire Recommended Daily Intake (RDI) amount of vitamin C (Rouseff and Nagy, 1994). However, there is considerable variation in the vitamin C content of juices of different citrus fruits. Grapefruit, tangerine and lemon generally contain between 20 and 50 mg 100 ml−1 juice (Yahia, 2006). The content of ascorbic acid in commonly consumed fruits is shown in Table 2.3. Many biological actions have been attributed to ascorbic acid. It is one of the most effective and least toxic antioxidants identified in mammalian systems. Ascorbic acid protects lipids in plasma and low-density lipoproteins (LDL) against peroxidative damage (Davey et al., 2000). Several studies have demonstrated that ascorbic acid may be important in protecting against oxidative stress-related diseases and degeneration associated with aging, including coronary heart disease, cataract formation, and cancer (Table 2.1). Ascorbic acid is also essential for collagen and carnitine synthesis. Vitamin C helps to maintain various enzymes in their required reduced forms. Ascorbic acid is a cofactor for the dopamine-β-hydroxylase and peptidylglycine α-amidating monooxygenase systems, which participate in the biosynthesis of norepinephrine and various α-amidated peptides (Sauberlich, 1994). Ascorbic acid is also involved in neural maturation, neuronal transmission, learning/memory and locomotor activity (Harrison and May, 2009). It participates in the normal functioning of fibroblasts and osteoblasts and immune function (Davey et al., 2000).

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Vitamin E The term ‘vitamin E’ is used to describe a family of structurally related compounds, eight of which have been isolated from plants, fruits and vegetables (α, β, γ, and δ-tocopherol and α, β, γ, and δ-tocotrienol). α-Tocopherol is the most important form of vitamin E and possesses the highest antioxidant activity. This form is also the most effective in preventing vitamin E deficiency symptoms (Traber, 2007). Most fruits contain only low concentrations of vitamin E. The major sources of this vitamin are edible vegetable oils, including those from nuts and avocados (Yahia, 2010). The content of tocopherols in some commonly consumed tropical and subtropical fruits is shown in Table 2.3. Vitamin E was discovered to be a nutritional factor that prevented the death and resorption of fetuses in pregnant rats. Other manifestations of vitamin E deficiency have been observed in different animal species, including testicular dystrophy in male rats, and injuries in the nervous system in chicks (Lang et al., 1985). In humans, vitamin E deficiency has been related to an increased risk of suffering atherosclerosis and other degenerative diseases (Lass and Sohal, 2000). Extensive literature supports the fact that vitamin E has protective effects against cardiovascular disease, including the prevention of oxidative modification of lowdensity lipoproteins (LDL), modulation of the arachidonate cascade so as to reduce vasoconstriction and thrombosis, and inhibition of smooth muscle cell proliferation (Table 2.1) (Bramley et al., 2000). Vitamin E also exerts protective effects against several forms of cancer (lung, esophagus, stomach, skin and large bowel) (McVean and Liebler, 1997). It protects the immune system, relieves the symptoms in patients suffering inflammatory conditions (arthritis, rheumatoid arthritis and osteoarthritis), and prevents cataract and age-related macular degeneration (Table 2.1). A possible protective effect of vitamin E on neurological disorders (Alzheimer’s and Parkinson’s diseases) has been proposed. Vitamin E is also known as the anti-ageing vitamin (Bramley et al., 2000), and has good antioxidant properties. Folates The term ‘folates’ is used to describe a family of compounds consisting chemically of a pteridine ring attached to a para-aminobenzoate, which in turn is attached to the amino acid glutamate. These compounds differ in the oxidation state of the molecule, the length of the glutamate side chain, and the specific one-carbon units attached to the molecule. The number of glutamate units in the side chain of natural folates varies from five to eight. The fully oxidized monoglutamate form of the vitamin is referred to as folic acid, which rarely occurs in nature. Polyglutamyl folate is common in foods (Bailey, 2007). Fruits provide 35% of the total folate intake in adults in some European countries. Folate-rich fruits include avocados (6–8 μg 100 g−1), bananas (14 μg 100 g−1) and oranges (31 μg 100 g−1) (Hall et al., 1955; Scott et al., 2000). The folates content in other fruits is shown in Table 2.3. Folates exert several functions in the human body. They are required in biochemical reactions involving one-carbon reactions such as amino acid metabolism, pyrimidine and purine synthesis, and methylation reactions following

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the formation of the body’s primary methylating agent, S-adenosylmethionine (SAM). Consumption of folic acid significantly reduces the risk of neural tube defects. Poor folate status has been associated with an increase in cancer risk, with the strongest support for colorectal cancer and its precancerous lesion, adenoma. Elevated plasma homocysteine concentration is a significant risk factor for vascular disease, and folic acid supplementation lowers plasma concentration of this metabolite (Bailey, 2007). Vitamin K Vitamin K was discovered by Henrik Dam as an antihemorragic agent. The term vitamin K is used to describe 2-methyl-1,4-naphthoquinone and all derivatives of this compound that exhibit antihemorrhagic activity in animals fed a vitamin K-deficient diet. Vitamin K can be found in some tropical and subtropical fruits, including avocados (40 μg 100 g−1), grapes (3 μg 100 g−1), cantaloupe (1 μg 100 g−1), bananas (0.5 μg 100 g−1), and oranges (0.1 μg 100 g−1). Vegetables and oils are better sources of vitamin K than fruits (Traber, 2007). The content of vitamin K in other fruits is shown in Table 2.3. The most important biological action of vitamin K in humans is related to its antihemorrhagic activity, although a possible protective effect of this vitamin on bone health and against the mineralization of cardiovascular tissues has also been postulated. Other vitamins Tropical and subtropical fruits provide low amounts of thiamin. Thiamin-rich fruits include oranges (0.11 mg 100 g−1), avocados, breadfruit and cherimoya (Yahia, 2006; Bates, 2007). Fruits, except almonds (0.93 mg/100 g), are poor sources of riboflavin (vitamin B2); however, avocados contain low amounts of this vitamin (Hall et al., 1955; Rivlin, 2007). Whole fruits and vegetables contain about 5–40 mg total choline per 100 g (Garrow, 2007). Fruits and vegetables do not contain vitamin B12 (Green and Miller, 2007). Breadfruit and cherimoya contain good amounts of niacin (Yahia 2006). Avocados are rich in vitamin B6 (3.9–6.1 μg g−1 pyridoxine) and to a lesser extent in biotin and vitamin D (Hall et al., 1955; Yahia, 2010). The content of thiamin, riboflavin, niacin, pantothenic acid, vitamin B6 and choline in some tropical and subtropical fruits is shown in Table 2.3.

2.3.2

Pigments

Chlorophylls The term ‘chlorophyll’ comes from the Greek roots chlorós (green) and phyllon (leaf). This term includes several forms of ‘chlorophyll’ and their derivatives. Chlorophylls a and b predominate in plants, occurring in the approximate ratio of 3:1. Chlorophyll-rich fruits are kiwi (6.8 mg Kg−1), olives (740–857 nmol fruit−1), avocados (38–101 mg Kg−1), and pistachio (25–160 mg Kg−1, on a dry basis) (Robertson, 1985; Ju et al., 1999; Bellomo and Fallico, 2007; Gallardo-

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Guerrero et al., 2007). Ashton et al. (2006) identified chlorophylls a and b, and pheophytins a in the skin, flesh and oil of avocado fruit. Chlorophyllides a and b were identified in the skin and flesh of avocado (Ashton et al., 2006). Chlorophyll a was the most abundant pigment in several cultivars/lines of Cactus pear with the highest quantity in the line ‘21 441’ (Castellanos-Santiago and Yahia, 2008). Natural chlorophylls and their derivatives (pheophytins and pheophorbides) have shown antimutagenic and antigenotoxic properties in many in vitro tests (bacterial, Drosophila wing spot, and cultures of mammalian cells). In vitro studies also suggest that sodium copper chlorophyllin (SCC) protects against several environmental and dietary mutagens (3-amino-1-methyl-5H-pyrido-[4,3-b]indole, 2-amino-3methylimidazo[4,5-f]quinoline (IQ), chromium (VI) oxide, aflatoxin B1, benzo[a] pyrene, benzo[a]pyrene-7,8-dihydrodiol-9-10-epoxide, 3-methylchloroanthracene, and 7,12-dimethylbenzo[a]anthracene). In vivo studies in rainbow trout and mice have demonstrated that SCC and natural chlorophylls have protective activity against hepatocarcinogenesis, skin carcinogenesis and papillomagenesis. The consumption of chlorophyll-rich foods has been positively correlated with a reduction in the risk of colon cancer in humans. Antioxidant activity, mutagen trapping, modulation of detoxification pathways and induction of apoptosis have been proposed as the cause of the cancer protective effects of chlorophylls and their derivatives. The literature suggests that the protective activity of natural chlorophylls is higher than those of commercial available chlorophyll derivatives (Ferruzzi and Blakeslee, 2007). Flavonoids Flavonoids are the pigments responsible for the color and flavor of many fruits, vegetables, flowers, nuts and seeds and therefore they are an important part of the human diet. Flavonoids belong to the family of phenolic compounds. The term ‘flavonoids’ is employed to describe a large group of structurally related compounds, including chalcones, flavones, flavonols, flavanones, flavanols, anthocyanins and isoflavones (Harborne and Williams, 2000). The content of flavonoids and other pigments in fruits depends on many factors including exposure to light, genotype, environmental conditions, ripening stage, processing, storage, postharvest handling and agricultural practices. Grapes are one of the most important dietary sources of phenolic compounds, including flavonoids (Frankel and Mayers, 1998). The phenolic compounds found in Vitis vinifera include phenolic acids, stilbenes, and flavonoids, which include flavonols, flavanols and anthocyanins, and play an important role in the quality of grapes and wines (Downey et al., 2006). Anthocyanins are directly responsible for the color of grape fruit and young wines, whereas astringency and structure of wines are related to catechins, and proanthocyanidins, and flavonols contribute to bitterness (Hufnagel and Hofman, 2008). Grapes and their products, such as grape juice and wine, have attracted a great deal of attention in recent years, and therefore, the composition and properties of grapes have been extensively investigated and their consumption is increasing.

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Studies in other fruits such as ripe and green papaya using HPLC-MS have identified other phenols, and other catechin conjugates (Mahattanatawe et al., 2006), which is consistent with the small number of compounds reported previously in this fruit (Agrawal and Agrawal, 1982). Quercetin and kaempferol, previously reported in leaves and shoots of C. papaya, were found only in trace amounts in fruit peel extracts (Canini et al., 2007; Miean and Mohamed, 2001). Recently Rivera-Pastrana et al. (2010) found that ferulic acid, caffeic acid and rutin were the most abundant phenols identified in ‘Maradol’ papaya fruit exocarp. Ma et al. (2004) isolated and identified seven phenolic compounds in Pouteria campechiana, P. sapota and P virids, namely gallic acid, (+)-gallocatechin, (+)-catechin, (−)-epicatechin, dihydromyricetin, (+)-catechin-3-O-gallate, and myricitrin. The highest level of the seven phenolic compounds was found in P. sapota, the second highest in P. viridis, and the lowest in P. campechiana. Mangosteen pericarp is rich in 1,3,6,7-tetrahydroxy-2,8-(3-methyl-2-butenyl) xanthone, a phenolic compound with high bioactivity (Yu et al., 2009). Alothman et al. (2008) reported that polyphenol content of Thai seedless guava was 123 to 191 gallic acid equivalents 100 g−1 (GAE 100 g−1), that of pisang mas was 24.4 to 72.2 GAE 100 g−1, and that of honey pineapple was 34.7 to 54.7 GAE 100 g−1. They observed that the high phenol content was significantly correlated with high antioxidant capacity. The content of total flavonoids in some tropical and subtropical fruits is shown in Table 2.4. A number of phenolic compounds, particularly flavonoids, are efficient antiproliferative agents, being able to inhibit proliferation of tumor cells by interfering with cell-cycle proteins or inducing apoptosis (Yang et al., 2001). Flavonoids can markedly improve the condition of patients suffering from various stages of cardiovascular diseases; they can reduce hypertension and ameliorate some of the consequences of diabetes mellitus. Other favorable properties include protective effects against gastrointestinal ulcers, and they also inhibit neuronal transmitter receptors from activating pain neurons, stimulate the immune function in humans, exert antiallergenic effects and prevent the development of Alzheimer’s disease (Wilson et al., 1991; Efrat et al., 1994; Havsteen, 2002). Flavonoids have shown anticancer activity against carcinomas largely consisting of cells of ectodermal (skin, breasts, oral epithelium, urogenital tract, and lungs), entodermal (gastrointestinal tract, mammary glands, gonads, uterus, lungs, prostate, colon, rectum, and mesenchyme) and mesodermal (blood cells, bone, and muscle) origin (Table 2.1). Flavonoids are also effective against some tumors formed by oncogenic viruses (Harborne and Williams, 2000; Moon et al., 2006). They have also shown high activity against many bacterial, protozoan, and fungal infections (Havsteen, 2002). The mechanisms by which polyphenols act as antitumoral agents are manifold and have been shown to be connected with the functions of radical scavengers, detoxification agents, cell signaling modulators, inhibitors of cell-cycle phases, and activators of apoptosis (Fresco et al., 2006). Some flavonoids are able to achieve this effect by inhibiting the enzyme DNA topoisomerase II, which is necessary for the survival and spread of cancerous

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© Woodhead Publishing Limited, 2011

Fruit

Source: USDA, 2005

Avocado Banana Blood orange Fig Grape juice Grapefruit (pink) Grapefruit (white) Grape (black) Grape (red) Grape (green) Kiwi Kumquat Lemon Mango Medlar Cantaloupe Honeydew Orange Papaya Pineapple Pomelo

Quercetin

0 0 0 0.93 0.64 0 0.05 2.54 1.38 1.62 0 0 0 0 0 0 0 0.58 0 0 0

Myricetin

0 0 0 0 0.21 0 0.05 0.45 0.01 0.3 0 0 0 0.03 0 0 0 0.02 0.03 0.01 0

Luteolin

0 0 0 0 0.01 0 0 0 1.30 0 0 0 1.12 0 0 0 1.90 0 0 0 0 0 0.64 0 0 0.01 1.13 0.01 0.02 0 0.01 0 0

Kaempferol

0 0 0 0 0.01 0 0 0

Apigenin 0 0 0 0 0.01 0 0 0 0 0 0 21.87 0 0.01 0 0 0 0.01 0.01 0 0

Naringenin 0 0 1.68 0 0 17.19 20.06 0 0 0 0 57.39 0.55 0 0 0 0 15.32 0 0 24.72

Hesperetin 0 0 13.12 0 0 0.78 3.42 0 0 0 0 0 27.90 0 0 0 0 27.25 0 0 8.40

(+)-Gallocatechin 0 0 0 0 0 0 0 0 0 0.01 0 0 0 0 0 0 0 0 0 0 0

(+)-Catechin 0 6.10 0 0.15 0.19 0 0 10.14 0.82 3.73 0 0 0 1.72 0.02 0 0 0 0 0 0

(−)-Epigallocatechin 3-gallate 0.15 0 0 0 0 0 0 0 0 0 0.09 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0.08 0.02 0 0 0 0 0.01 0 0.04 0 0 0 0

(−)-Epigallocatechin

Content of phenolic compounds (mg 100g−1) in some tropical and subtropical fruits

0 0 0 0 0 0 0 2.81 0.17 0.25 0.01 0 0 0 0.23 0 0 0 0 0 0

(−)-Epicatechin 3-gallate

Table 2.4

(−)-Epicatechin 0.37 0.02 0 0.02 0 0 0 8.68 1.2 1.7 0.27 0 0 0 0.53 0 0.01 0 0 0 0

Petunidin 0 0 0 0 0 0 0 0 2.11 0 0 0 0 0 0 0 0 0 0 0 0

Peonidin 0 0 0 0 0 0 0 0 2.89 0 0 0 0 0 0 0 0 0 0 0 0

Pelargonidin 0 0 0 0 0.02 0 0 0 0.02 0 0 0 0 0.02 0 0 0 0 0 0 0

Malvidin 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 34.71 0 0 0 0

Delphinin 0 7.39 0 0 0.47 0 0 0 3.67 0 0 0 0 0.02 0 0 0 0 0 0 0

0.33 0 0 0 0.56 0 0 0 1.46 0 0 0 0 0.1 0 0 0 0 0 0 0

Cyanidin

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cells (Fresco et al., 2006). Indeed, phenolic compounds show anti-inflammatory activity, which is mediated by inhibiting the formation of transcription factors closely linked to inflammation, such as NF-κB and enzymes such as xanthine oxidase, cytochrome oxidase, and lipoxygenase, which mediate the inflammatory process (Chu et al., 2002). Flavonoids have also been shown to reverse vascular endothelial dysfunction by increasing endothelium-derived nitric oxide bioactivity (Duffy and Vita, 2003). Carotenoids The term ‘carotenoids’ is used to describe a group of lipophyllic pigments. They confer a yellow, orange and red color to some fruits, vegetables, flowers, grains and animals. Carotenoids can be classified as carotenes and xanthophylls. Carotenes’ chemical structure includes carbon and hydrogen atoms, exclusively; while xanthophylls may have different oxygenated groups such as hydroxyl, ketonic, epoxy, etc. (Yahia and Ornelas-Paz, 2010). Fruits and vegetables provide 70–90% of the intake of carotenoids. Tropical and subtropical fruits are rich sources of carotenes and xanthophylls esters, and they have more carotenoids than temperate fruits which contain more anthocyanins. Mango and papaya are among the tropical fruits rich in carotenoids (Ornelas-Paz et al., 2007; 2008a; 2008b; Rivera-Pastrana et al., 2010). Carotenoids in these fruits are highly bioavailable since they occur dissolved in oil droplets (West and Castenmiller, 1998). β-Carotene (all-trans), β-cryptoxthanin (all-trans and cis), zeaxanthin (all-trans), luteoxanthin isomers, violaxanthin (all-trans and cis) and neoxanthin (all-trans and cis) have been identified in several mango cultivars (Mercadante et al., 1997; Ornelas et al., 2007; 2008a; 2008b). Ashton et al. (2006) identified lutein, α-carotene, β-carotene, neoxanthin, violaxanthin, zeaxanthin and antheraxanthin in the skin, flesh and oil of avocado fruit. It has also been reported that avocado is a good source of lutein (containing up to 248 mg 100g−1) (Mazza, 1998). Lycopene, β-cryptoxanthin and β-carotene were identified as major carotenoids in mesocarp of ‘Maradol’ papaya fruit (Rivera-Pastrana et al., 2010). Several cultivars/lines of cactus pear fruit had a similar carotenoid profile, in which lutein was the most abundant compound in ‘Camuesa’, while neoxanthin was the most abundant compound in the line ‘21 441’ (Castellanos-Santiago and Yahia, 2008). The carotenoid content in some common tropical and subtropical fruits is shown in Table 2.2. Epidemiological evidence has demonstrated that the increased consumption of fruits and vegetables rich in carotenoids is associated with a reduced risk of cancer. Carotenoids are involved in the elimination of singlet oxygen and peroxyl radicals, prevent cardiovascular diseases and modulate immune function (Table 2.1). They exhibit biological actions that impact cellular signaling pathways, gene expression or inhibiting certain enzymes. They are found in the macula of the eye, where they decrease the risk of developing age-related macular degeneration and cataracts. These and other biological actions of carotenoids have been described elsewhere (Yahia and Ornelas-Paz, 2010). There has been major interest in the effects of lycopene in the reduction of

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different diseases especially those related to heart disorders. However, in humans, unlike β-carotene, lycopene is not transformed into vitamin A, as it lacks the β-ionone ring required for conversion into retinoids. Additionally, lycopene has been associated with decreased incidence of prostate cancer (Itsiopoulos et al., 2008) Bioavaibility of carotenoids differs depending on fruit cultivar and matrix in which they are contained. Recently, Ornelas et al. (2010) reported that bioavaibility of β-carotene of ‘Ataulfo’ mango was higher than that of carrots. These authors suggested that differences could be attributed to variation in firmness, fiber content between mango and carrots, how carotenoids are stored in chromoplasts and absorptive interactions among carotenoids. Ripe mango fruit is softer than carrots and therefore mechanical and enzymatic disruption of mango tissue during digestion could be more efficient than that of carrots, leading to an increase in carotenoids released from food. Disruption of cell walls from foods is closely related to the carotenoids bioavailability (West and Castenmiller, 1998). Betalains Betalains are water-soluble nitrogen-containing pigments. They can be red-violet (betacyanins) or yellow (betaxanthins). They are immonium conjugates of betalamic acid with cyclo-dopa and amino acids or amines, respectively. The chromophore structure in all betalains is the betalamic acid. Betalains are found in some flowers, fruits and fungi and have been considered a new class of dietary cationized antioxidants (Kanner et al., 2001). Betalains are accumulated in the vacuoles of vegetative and reproductive tissues, and they are found mainly in epidermal and subepidermal tissues. Their presence in reproductive tissue such as petals, seeds and fruits depends generally on the developmental stages, but their presence in vegetative tissue appears to be regulated to a greater extent by environmental conditions. Major dietary sources of betalains include cactus pear (6.6–114 mg 100 g−1) and red-purple pitaya (Stintzing and Carle, 2007; Castellanos-Santiago and Yahia, 2008). Cactus pears contain mainly indicaxanthin, betanin and isobetanin, and can have up to 24 different betalains (Castellanos-Santiago and Yahia, 2008). Red-purple pitaya contains betanin, isobetanin, phyllocactin, hylocerenin and isohylocerenin (Strack et al., 2003; Stintzing and Carle, 2007). The ratio and concentration of betalain pigments in cactus pear fruit are responsible for the color of specific cultivars, showing the highest betalains content in fruit of purple color, comparable to that found in red beet (Beta vulgaris L. cv. Pablo) (Castellanos-Santiago and Yahia, 2008). Several studies have demonstrated that betalains present in these fruits exert antioxidant activity, which is twice that reported in apple, pear, tomato, banana, white grape and orange (Wang et al., 1996; Butera et al., 2002). It has been considered that betalains exert anti-carcinogenic effects (Sreekanth et al., 2007). Gentile et al. (2004) demonstrated that betalains also modulate the expression of adhesive molecules in endothelial cells. This property along with their antioxidant

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activity is the probable cause of the protective effects of betalains in some diseases such as atherosclerosis, atherotrombosis and ischemia. 2.3.3 Fibers The term ‘fiber’ can be defined in several ways, depending on the extraction and quantification method. This term can also be defined on the basis of physiological issues. In general, it includes a group of compounds of plant origin that cannot be hydrolyzed by human digestive enzymes. These compounds include non-starch polysaccharides (cellulose, hemicelluloses, pectins and mucilages) and lignin, a molecule of polyphenylpropane units. Compounds such as sugar alcohol, polydextrose, and other oligosaccharides are not digested by human digestive enzymes and are thought to function like dietary fiber, although they are not considered in the traditional measurements of fiber. Resistant starch, the sum of starch and starch-degradation products, is neither digested in the small intestine nor considered in the fiber quantification (Slavin, 2003). Tropical and subtropical fruits are rich in fibers (Table 2.5). Fiber is commonly classified as soluble and insoluble. Soluble fiber has been shown to have beneficial effects on carbohydrate and lipid metabolism. As indigestible polysaccharides, the fiber health benefits have been linked to the formation of a gelatinous matrix that increases fecal mass. This contributes to a reduction in the concentration of harmful biliary acids and other potential cancerous compounds in excrement. Health-related effects for fibers include lowering serum lipid and blood cholesterol, which exert protective effects against cardiovascular diseases (hyperlipidemia, hypertension and coronary heart disease). Fibers modify gut function, helping against intestinal disorders. They help in controlling blood glucose and therefore protect against diabetes. Insoluble fibers are most effective for relaxation assistance (Slavin, 2003). However, several studies have demonstrated that the ingestion of fibers decreases carotenoids bioavailability. Horvitz et al. (2004) demonstrated that carrot fibers reduce carotenoids bioavailability in humans. Pasquier et al. (1996) showed that several dietary fibers increased the viscosity of reconstituted duodenal medium and affected fat emulsification and lipolysis, two indispensable steps for carotenoid micellarization and absorption (Faulks and Southon, 2005). Several possible mechanisms have been proposed for the effect of fibers on colon cancer, including the dilution of potential carcinogens and speeding their transit through the colon, binding carcinogenic substances, altering the colonic flora, reducing the pH, or serving as the substrate for the generation of short-chain fatty acids that are the preferred substrate for colonic epithelial cells (Slavin, 2003). Currently, the health-protective mechanisms of fiber intake are under close examination in the search for a more complete picture that includes other molecules bound to polysaccharides. Higher intake of fibers has also been hypothesized to reduce risk of breast cancer by interrupting the enterohepatic circulation of estrogens (Willett, 2000). However, the role of dietary fiber in cancer prevention remains controversial. Therefore more evidence is necessary to understand the possible role of fiber in deteriorative biological processes.

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73.2–79.7 54–78.3 82.4–87.7 82 71–79.7 89.5 46.9–94.2 76.1–79.1 77–90.5 88.1–91.6 76–87 87.6–92.8 79.7–83.2 83.8–90.3 77.3–88.9 77.1–90.1 79.6–91.6 90.2–92.9 85–88.6 85.9–91.5 72.9–85.9 85.1–89.3 77.9–84.4 86.4–90.6 81.4–91 81–84 18.4–31.4 90.5–95.7

Avocado Banana Bitter orange Black sapote Chico sapote Citron Coconut Fig Grape Grapefruit Guava Key lime Kiwifruit Lemon Mamey Mandarin Mango Muskmelon Orange Papaya Passionfruit Pineapple Pomegranate Pomelo Prickly pear Soursop Tamarind Watermelon

Source: USDA, 2005

Water

1.4–2 0.5–4.4 0.6–1.5 0.8 0.4–1.7 0.8 1.8–3.8 0.7–1.4 0.2–0.9 0.5–0.9 0.5–2.5 0.4–0.9 1.0–1.2 0.5–1.2 0.4–1.2 0.5–0.9 0.3–0.8 0.5–1.1 0.5–1.2 0.4–1.4 1.5–2.2 0.4–0.6 0.5–1.6 0.5–0.8 0.3–1.1 0.9–1.1 2.8–5.4 0.4–0.7

Protein 12.7–18.4 0.1–1.8 0.2–0.6 0.1 0.3–1.1 0.1 0.2–34.7 0.1–0.4 0–0.6 0.1–0.4 0.1–0.9 0.1–0.5 0.4–1.4 0.3–0.6 0.1–0.5 0.1–0.4 0.0–0.3 0.1–0.2 0.1–0.3 0.1–0.2 0.5–0.7 0.1–0.4 0.1–1.2 0.1–0.4 0.1–0.5 0.2–0.3 0.5–1.7 0.2–0.4

Fat 0.8–1.6 0.4–3.6 0.4–0.8 1.1 0.3–1.2 0.3 0.7–1.4 0.2–1.1 0.3–0.7 0.3–0.4 0.5–1.3 0.3–0.4 0.5–0.8 0.3–0.5 0.3–0.8 0.4–3.8 0.1–0.6 0.4–0.7 0.4–0.6 0.4–0.7 0.5–1.4 0.2–0.4 0.4–1.4 0.3–0.5 0.3–1.6 0.6–0.7 2.5–2.9 0.2–0.4

Ash

3 1.8 1.2–1.8 0.9 2.4–2.7 1.4–1.8 10.4 1.2–1.4 4 2.3 3.6–8.2 3.3 5.1 0.3–0.4

9 2.9 0.4–2.3 1.1–1.6 4.9–5.4 2.8–4.5 2–3

16 2.6–5.3

6.7 0.5–22.8

Dietary fiber 0.6–9.7 12.2–43.3 11.1–14.7 82 18.8–26.2 9.3 4.6–30.2 9–22.1 8.6–21.3 6.9–8.8 8.9–22.4 1.6–10.8 8.9–18 8.1–14.7 9.7–20.6 8.6–21.2 10.8–19.5 5.7–26 9.14–13.5 5.9–12.8 11.2–22.8 9.8–14 12.9–22.8 8.4–12.5 8.5–16.6 13.5–14.6 57.4–73.2 3.7–8.5

Sugars, total

Content of fiber (g 100g−1) and other compounds in some tropical and subtropical fruits

Fruit

Table 2.5

6.1

9.3 6.1

15.4

6.3 5 11.6

8.2–20.1

Sugars available 145–198 81–185 49–70 68 23.6–83 41 21–382 38–95 36–92 30–42 32–96 26–51 60–81 39–50 42–92 40–92 33–81 26–34 42–59 28–54 56–106 43–59 62–106 28–54 41–74 63–66 239–323 16–37

Energy (kcal)

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Postharvest biology and technology of tropical and subtropical fruits

2.3.4 Minerals Tropical and subtropical fruits are mineral-rich foods (Table 2.6). Humans can be deficient in some minerals, either due to insufficient intake or to poor absorption from food, which can cause suffering and even death. Oligoelements, a group of minerals, are transitional metals that have a role in the synthesis and structural stabilization of proteins and nucleic acids (Halliwell and Gutteridge, 1989). Numerous studies have been developed to investigate the role of minerals in preventing or slowing ‘oxidative damage’. Minerals have a function in the mechanism of preventive defense against free radicals performed by antioxidant enzymes. These enzymes work in a coordinated and integrated manner, centered on the availability of oligoelements and NADPH, which is the source of reducing equivalents against oxygen radicals. The most important of these minerals are magnesium, copper, zinc, manganese, iron and selenium (Jackson and Combs, 2008). The content of these compounds varies among species.

Table 2.6

Content of some minerals (mg 100g−1) in some tropical and subtropical fruits

Fruit

Na

K

Ca

P

Fe

Zn

Avocado Banana Bitter orange Black sapote Chico sapote Citron Coconut Fig Grape Grapefruit Guava Key lime Kiwifruit Lemon Mamey Mandarin Mango Muskmelon Orange Papaya Passionfruit Pineapple Pomegranate Pomelo Prickly pear Soursop Tamarind Watermelon

4–7 1–3 1

485–604 348–370 200 193

52–604 20–54 17–26 26 12–28

17–25 1–2 2 0.1 2–4 2 0.3–7 3–6 15 1–2 2–2.9 9–17 0 3 28 1 3–85 0 2–5 14 28 1–8

147–436 232–268 185–191 127–150 284–417 102 312–332 145–163 47 166–178 156–309 182–309 169–181 257 348 108–125 63–348 139 157–220 278 628 73–116

0.5–0.6 0.3–1.4 0.7–0.8 1.6 0.8–2.4 1.6 0.5–3.4 0.3–0.8 0.2–1.1 0.05–2 0.1–0.7 0.2–0.6 0.2–0.4 0.4–0.7 0.2–0.7 0.15–0.8 0.1–1.3 0.2–1.4 0.09–0.8 0.1–0.6 1.6–1.7 0.25–0.4 0.3–1.6 0.1–0.4 0.2–2.6 0.3–0.7 0.8–2.8 0.2–0.7

0.4–0.64 0.15–0.2

12

10–39 4–42 36–65 47 21–46 31 7–46 34–58 5–19 11–34 17–33 21–34 20–36 21–107 11–51 18–35 8–17 9–23 17–43 22–25 9–12 10–221 3–13 13–29 22–57 14–38 74–118 4–12

51–113 14–43 10–33 7–18 15–40 9–27 29–40 21–29 11–46 10–30 11–32 5–32 12–51 5–21 21–68 5–13 8–105 19–32 7–39 27–43 86–113 3–283

Source: USDA, 2005

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0.1 1.1 0.2–1.5 0.07 0.07 0.2–0.23 0.1 0.1–0.2 0.1 0.1 0.07 0–0.04 0.07–0.2 0.06–0.08 0–0.07 0.1 0.08–0.12 0.35 0.1–0.12 0.1 0.1 0–0.1

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Most tropical fruit are good sources of iron (Fe) (Yahia, 2006). In humans, Fe is needed for the synthesis of proteins (i.e. hemoglobin and myoglobin) and Fe-containing enzymes (hemo enzymes, several enzymes required for energy production and those involved in immune defense and thyroid function). Deficiency in Fe can lead to anemia, which can decrease mental and psychomotor development in children, increase both morbidity and mortality of mother and child at childbirth, decrease work performance and decrease resistance to infection. In general, the content of Fe in tropical and subtropical fruits is moderate (Frossard et al., 2000). Some human diseases (Keshan and Kashin-Beck diseases) have been attributed to Selenium (Se) deficiencies. Selenium consumption is inversely correlated with the risk of developing cancer (Jackson and Combs, 2008). Hydrogen selenide, methylselenol and selenomethionine, the principal selenium metabolites, can regulate gene expression, protect DNA from damage, and stimulate the repair and regulation of cell cycles. Selenium deficiency has also been associated with an increased risk of suffering cardiovascular diseases. This mineral is involved in the kwashiorkor disease (protein-energy malnutrition disease), the susceptibility against malaria infection and the activity of some enzymes (Levander, 1987). Zinc (Zn) is found abundantly in bones and skeletal muscle, and acts as a stabilizer of the structures of membranes and cellular components. It is a cofactor of several enzymes, including some involved in the synthesis and degradation of carbohydrates, lipids, proteins and nucleic acids. Zn is involved in gene expression and its deficiency causes a reduction in growth, sexual maturity and the immune response. It seems to be involved in a low incidence of diarrhea and respiratory infections. The content of Zn in tropical and subtropical fruits is moderate (Table 2.6) (Frossard et al., 2000). Magnesium (Mg) is required in many enzymatic reactions involved in the metabolism of macromolecules in humans. It is needed for contraction and relaxation of muscle and is an important component in bones and teeth (Shils, 1988). Mg can act as cofactor of superoxide dismutase enzyme that participates in the dismutation of peroxyl radical. Phosphorus (P) is essential for cell division, involved in the formation and maintenance of bones and teeth, and required for proteins formation. Phosphodiester bonds link mononucleotide units forming long chains of DNA and RNA; the biosynthesis of all complex molecules of life is powered by energy released by the phosphate bond reversibly moving between adenosine diphosphate (ADP) and adenosine triphosphate (ATP). No life (including microbial life) is possible without it (Smil, 2000). Ca has several functions in humans, but its involvement in the growth and development of bone is the most important (Frossard et al., 2000). Most tropical fruit are good sources of potassium (K) (Yahia, 2006). K influences many processes in the human body. It is the principal base in tissues and blood cells and plays an important role in the regulation of acid-base balance. It is also important in the transmission of nerve impulses to muscle fibers and in the contractility of the muscle itself. Sodium (Na) affects the osmotic pressure of

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the plasma, the volume of plasma and interstitial fluid, acid-base balance, the electrical activity of body cells, and the responsiveness of the cardiovascular system to circulating endogenous pressor agents (Fregly, 1981). 2.3.5 Other compounds Tropical and subtropical fruits are good sources of carbohydrates. Examples include bananas, plantains and breadfruit, which are widely used as sources of starch (Yahia, 2006). Avocado fruit and olives are high fat fruit, contain rare sugars of high carbon number and nitrogenous substances (Yahia, 2010). The oil content of avocado is high, ranging from as low as 3% to as high as 30%, while its sugar content is low (about 1%); hence it is recommended as a high energy food for diabetics (Yahia, 2010). A 100 g serving has about 177 calories, contains no cholesterol, and has about 17 g of fat, and the oil content is a key part of the sensory quality of the fruit. Oil quality in avocado fruit is very similar to that of olive oil. A high proportion of the oil (approximately 75%) is mono-unsaturated. Approximate proportions of saturated fatty acids and polyunsaturated fatty acids are 15% and 10% respectively. The major fatty acid in the edible portion of avocado fruit is oleic, followed by palmitic and linoleic acids, while the fatty acids present in trace amounts are myristic, stearic, linolenic and arachidonic (Mazliak, 1971; Tango et al., 1972; Gutfinger and Letan, 1974; Itoh et al., 1975; Swicher, 1984). Avocado and nuts also contain phytosterols, including β-sitosterol, which exert protective effects against cardiovascular diseases (Mazza, 1998). Some chemical components of Carica papaya fruit pulp have been reported by Oloyede (2005), suggesting that the astringent action of the plant, encountered in numerous therapeutic uses, is due to the presence of some phytochemicals such as saponins and cardenolides.

2.4

Bioactive compounds and antioxidant capacity

The human organism can produce high levels of free radicals under certain conditions. These compounds can damage several macromolecules (proteins, nucleic acids and membrane lipids), causing abnormal cellular activity and leading to the development of several degenerative diseases. Free radicals are involved in the pathology of 100 different diseases, including cancer, atherosclerosis, rheumatoid arthritis and cataracts. Tropical and subtropical fruits provide an optimal mixture of phytochemicals, such as vitamins C and E, carotenoids and flavonoids along with complex carbohydrates and fiber. These phytochemicals are able to scavenge or quench free radicals, diminishing the risk of suffering some diseases. Overall, the ability of fruit phytochemicals to avoid oxidation of a substrate has been called their antioxidant activity. Individual phytochemicals contribute to different extents to the total antioxidant capacity of fruits and there are synergistic effects. Several methods have been used to determine the relative antioxidant

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activity of fruits extracts; however, the values obtained by an individual assay reflect only the chemical reactivity under the specific conditions applied in that assay (pressure, temperature, reaction media, coreactants and reference points). Results of antioxidant activity assays can differ from method to method (Huang et al., 2002). Existing methods for measuring the antioxidant activity seem to be considerably sensitive to hydrophilic antioxidants, especially to phenolic compounds. Wu et al. (2004) demonstrated that the lipophilic antioxidant activity of several carotenoids-rich tropical and subtropical fruits (cantaloupe, honeydew, mango and oranges) was 19–70 times lower than the hydrophilic antioxidant activity. In a previous study of some American tropical fruits (acerola, acai, mangaba and uvaia) cultivated in Brazil, it was observed that the high antioxidant capacity of acerola fruit was positively related with its high vitamin C and phenol content (Rufino et al., 2007). Similarly, Corral-Aguayo et al. (2008) found that the content of total phenols and vitamin C in several tropical and subtropical fruits were highly correlated with the antioxidant activity evaluated with six different assays. Corral-Aguayo et al. (2008) also reported that the antioxidant capacity of papaya (a carotenoids-rich fruit) extract was one of the lowest. Vitamin C content in juices from several citrus fruits (orange, and pink grapefruit) contributed 66–100% of the antioxidant activity (Gardner et al., 2000). Banana has the lowest vitamin C, E and β-carotene levels compared with mango, papaya and pineapple. However, banana has a higher phenol content than pineapple and papaya. It appears that the high phenolic content of mango and banana contributes to a greater extent to their total antioxidant capacity than other bioactive compounds (Table 2.7). Vitamin C content in pineapple contributed only 0.8% of the antioxidant activity (Gardner et al., 2000). Several studies have reported polyphenolic compounds in mango, papaya and pineapple flesh and peel, including various flavonoids, xanthones, phenolic acids and gallotannins (Berardini, 2005a; 2005b). Among these compounds, mirecitine, mangiferine, gallic acid and hydrolysable tannins, which are most likely gallotannins, are the major antioxidant polyphenolics found. Tropical and subtropical fruits contain a wide range of antioxidant compounds at different levels, causing variations in antioxidant activity between these fruits. Some examples follow. Pineapple fiber showed higher (86.7%) antioxidant activity than orange peel fiber (34.6%) (Larrauri et al., 1997). Orange (Citrus sinensis) was found to be more active than pink grapefruit (Citrus paradisi) in scavenging peroxyl radicals, while grapefruit juice was more active than orange juice, when the ORAC assay was used (Wang et al., 1996). The total antioxidant activity in orange juice was thought to be accounted for by hesperidin and narirutin (Miller and Rice-Evans, 1997). Several nuts are among the edible plants with high total antioxidant content. Of the tree nuts, walnuts, pecans and chestnuts have the highest antioxidant content. Walnuts contain more than 20 mmol antioxidants per 100 g, mostly in the walnut pellicles (Blomhoff et al., 2006; Yahia, 2010). Nine phenolic compounds have been identified in almonds by Sang et al. (2002), of which eight exhibited strong antioxidant activity. Almond skins were found to contain high levels of four different types of flavanol glycosides,

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Table 2.7 Antioxidant activity of some tropical and subtropical fruits determined by three assays Fruit

Avocado Banana Coconut Grapefruit Guava Kiwifruit Lime Mango Melon Oranges Papaya Pineapple Watermelon

Method Ascorbic Acid Equivalent Antioxidant Capacity (AEAC) (mg EAA 100 g−1)

Oxygen Radical Absorbance Capacity (ORACFL) (μmol TEg−1)

Ferric Reducing Antioxidant Power (FRAP) (mmol 100g−1)

143 48.3 11.5–45.8

10.9 8.1

3.9

15.5 270 136 93.3 139 19.6 142 141 85.6 11.9

9.2 10.0 2.4–3.1 18.2 7.9 1.4

21.0 15.5 4.6 25.1 7.6 2.81

Sources: Prior et al. (2003); Guo et al. (2003); Leong and Shui (2002); Wu et al. (2004); Corral-Aguayo et al. (2008)

which are thought to have powerful effects as antioxidants (Frison and Spons, 2002). Aqueous extracts of cactus pear fruit (O. ficus-indica L. Mill) were reported by Butera et al. (2002) to possess a high total antioxidant capacity, expressed as trolox equivalents, and exhibit a marked antioxidant capacity in several in vitro assays, including the oxidation of red blood cell membrane lipids and the oxidation of human LDLs induced by copper and 2,2′-azobis(2-amidinopropanehydrochloride). Antioxidant components reported by these authors included vitamin C, negligible amounts of carotenoids and vitamin E. However, CorralAguayo et al. (2008) reported that the antioxidant capacity of extracts of prickly pear fruit ranked the lowest compared to seven other fruits. Some prickly pear fruits contain two betalain pigments, the purple-red betanin and the yellow indicaxanthin, both with radical-scavenging and reducing properties (Forni et al., 1992; Fernandez-Lopez and Almela, 2001; Stinzing et al., 2002; CastellanosSantiago and Yahia, 2008). There are also variations in antioxidant activity between different anatomical parts of the same fruit. Kondo et al. (2005) observed that total phenolics in guava and mango fruits were higher in the skin than in the flesh, being high at the immature stage and decreasing towards ripening. In contrast, total phenolic content of banana flesh was higher than in the skin, while those of papaya skin and flesh showed no significant differences. Recently, Rivera-Pastrana et al. (2010) reported that the exocarp of ‘Maradol’ papayas contains significantly higher phenols content than the mesocarp. Kanazawa and Sakakibara (2000) identified

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higher levels of dopamine, a strong water-soluble antioxidant, in banana fruit (Musa cavendishii) peel than in pulp: 80–560 mg 100 g−1 and 2.5–10 mg 100 g−1 respectively. The concentration of ascorbic acid in the skin of bananas and papayas is higher than that in the flesh, while in guavas and mangoes the concentration of this bioactive compound is similar in the skin and the flesh (Kondo et al., 2005). Antioxidant activity is generally higher in the seeds than in the peel (Bocco et al., 1998) due the high content of flavonols, tannins and other related compounds. However, it is important to consider the use of seeds as supplements in the diet since some seeds contain compounds with high antiphysiological potential harmful for the organisms. Seeds of lemons, sour orange, sweet orange, mandarins and limes had greater antioxidant activity than the peel (Bacco et al., 1998).

2.5

Overview of health effects of some tropical and subtropical fruits

2.5.1 Cancer Cancer is a chronic disease with public health relevance worldwide. In a simplistic fashion, cancer is caused by specific mutations in genes associated with cell cycle control, apoptosis and DNA repair enzymes. Epidemiological studies have revealed that the incidence of cancer is strongly related to geographical locations, inferring that it is a consequence of lifestyle rather than genetic differences. The consumption of five portions of fruits and vegetables per day has been proposed as a strategy to reduce the incidence of several chronic diseases, including cancer. Several studies have demonstrated that increased consumption of foods of plant origin reduces the incidence of some forms of cancer (Yahia, 2010). This effect has been attributed to the high content of fiber and some secondary metabolites in these types of foods. Several in vitro studies have demonstrated that these secondary metabolites (such as chlorophylls, phenolic compounds, carotenoids, betalains, vitamins, etc.) are responsible for the anticancer effects of fruits and vegetables (Table 2.8) through several possible mechanisms, such as exerting their antioxidant activity, modulating gene expression, preventing DNA damage, trapping or diluting carcinogens, alleviating the carcinogen-induced oxidative damage, altering the carcinogen metabolism, inducing apoptosis, killing cancer cells, etc. (Shih et al., 2005). However, in vitro studies using pure secondary metabolites commonly found in fruits instead of whole fruits do not support the evidence provided by epidemiological studies (Temple and Gladwin, 2003). For example, epidemiological studies suggest an inverse correlation between apple consumption and colon cancer risk. However, under the cancer promoting condition of obesity, apple juice did not show cancer-preventive bioactivity (Koch et al., 2009). Some intervention trials with pure carotenoids did not show any effect on cancer risk, and in fact other trials have shown increased risk (Stahl and Sies, 2005). Edenharder et al. (1994)

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SGC 7901 (stomach) A549 (lung) HepG2 (liver) Delphinidin 3-O-glucoside and delphinidin AGS (stomach) HCT-116 (colon) 3-O-rutinoside from fruits of Cornus alternifolia, MCF-7 (breast) Cornus controversa, Cornus kousa and Cornus NCI-H460 (lung) florida SF-268 (central nervous system) AGS (stomach) Cornin from fruits of C. kousa HCT-116 (colon) MCF-7 (breast) NCI-H460 (lung) SF-268 (central nervous system) Ursolic acid and β-sitosterol from fruits of C. kousa AGS (stomach) MCF-7 (breast) NCI-H460 (lung) SF-268 (central nervous system) HT-29 (colon) Aqueous extracts from fruits of Rubus coreanum Chebulagic acid from fruits of Terminalia chebula HCT-15 and COLO-205 (colon) MCF-7 and MDA-MB-231 (breast) DU-145 (prostate) K562 (erythromyeloblastoid leukemia)

Human cancer cell line

Vareed et al. (2007)

Vareed et al. (2007)

Kim et al. (2005) Reddy et al. (2009)

Reduction of proliferation (16–35%)

Viability reduction Decreased viability and proliferation and induced cell death

Vareed et al. (2006)

Reduction of proliferation (50%)

Reduction of proliferation (9–40%)

Prasad et al. (2009)

Reference

Reduction of proliferation

Effect

Effect of some tropical and subtropical fruit extracts on human cancer cell lines in culture

Ethanolic extracts from longan fruit

Fruit

Table 2.8

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Cytotoxicity

Oral cancer cells Leukaemia cells

Carotenoids-rich extracts from apples and oranges

Cytotoxicity

Reduction of proliferation Induction of cell death

Liver cancer cells Leukaemia cells

Motohashi et al. (2004) Molnár et al. (2005)

Wang et al. (2006) Nair et al. (2009)

Lim et al. (2009)

Induction of cell death

Hexane extracts from immature fruits of Citrus grandis Osbec Polyphenols-rich extracts from litchi fruits 3-(8′(Z),11′(Z)-pentadecadienyl) catechol from whole fruits of Semecarpus anacardium Extracts from barbados cherry

Extracts from fruits of Fructus Bruceae

Lau et al. (2008)

Ejaz et al. (2006)

Reduction of proliferation

Saleem et al. (2002)

Yu et al. (2009)

Hirata et al. (2009)

Carvalho et al. (2010)

Cytotoxicity (46–73%)

Reduction of proliferation

Reduction of proliferation

Decreased viability, and proliferation Cytotoxicity

LOVO (colon) MCF-7 (breast) Breast cancer cells

Caco-2 (colon) A-498 and 769-P (kidney) HT-29 (colon)

PC-3 (prostate) HOS-1 (osteosarcoma) Pancreatic adenocarcinoma cells U937 (leukaemia cells)

5-Hydroxy-6,7,8,3′,4′-pentamethoxyflavone from Citrus fruits 1,3,6,7-tetrahydroxy-2,8-(3-methyl-2-butenyl) xanthone from mangosteen pericarp Limonoids from citrus fruit of the Rutaceae and Maliaceae families Methanolic extracts of Terminalia chebula fruits

Walnut methanolic extracts

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classified some tropical and subtropical fruits according to their in vitro antimutagenic activity. Strong antimutagenic activities were detected in bananas, pineapple and watermelon while moderate activities were found in kiwifruit, mangoes and honeydew melons. Several in vitro studies have shown that phenolic compounds in fruits and vegetables have an antiproliferative effect in different cancer cell lines (Sun et al., 2002; Mertens-Talcott et al., 2005; Percival et al., 2006; Yahia, 2010). Quercetin, a flavonoid found in many tropical and subtropical fruits, has been shown to affect the metastatic potential of tumor cells in mice (Suzuki et al., 1991). Mutagenicity of quercetin was examined by means of DNA fingerprint analysis using the Pc-1 probe that efficiently detects mutations due to recombination. Treatment of BMT-11 and FM3A tumor cells with quercetin resulted in gain and loss of bands in the fingerprints in both cell lines. The frequencies of the clones having undergone mutation were 3/11 and 6/26, respectively. This suggests that quercetin is mutagenic and induces recombination, and the results seem to provide a molecular basis for the phenotypic variations of BMT-11 tumor cells induced by quercetin. Chlorophyllin (CHL), a food-grade derivative of the ubiquitous tropical and subropical fruits pigment chlorophyll, has been shown to be a potent, dose-responsive inhibitor of aflatoxin B sub(1) DNA adduction and hepatocarcinogenesis in the rainbow trout model when fed with carcinogen (Breinholt et al., 1995). Chlorophyllins are derivatives of chlorophyll in which the central magnesium atom is replaced by other metals, such as cobalt, copper or iron. The relative efficacy of chlorophyll and chlorophyllin has been shown to modify the genotoxic effects of various known toxicants (Sarkar et al., 1994). CHL neither promoted nor suppressed carcinogenesis with chronic postinitiation feeding. By molecular dosimetry analysis, reduced aflatoxin B sub(1)-DNA adduction accounted quantitatively for reduced tumor response up to 2000 ppm dietary CHL, but an additional protective mechanism was operative at 4000 ppm CHL. The finding of potent inhibition (up to 77%) at CHL levels well within the chlorophyll content of some green tropical and subtropical fruits may have important implications in intervention and dietary management of human cancer risks. Monoterpenes, natural plant products found in the essential oils of several commonly consumed tropical and subtropical fruits which have been widely used as flavor and fragrance additives in food and beverages, have been shown to possess antitumorgenic properties (Kelloff et al., 1996). Limonene, the simplest monocyclic monoterpene which is found in some citrus fruits, and perrillyl alcohol, a hydroxylated limonene analog, have demonstrated chemopreventive and chemotherapeutic activity against mammary, skin, lung, pancreas and colon tumors in rodent models (Wattenberg and Coccia, 1991; Crowell and Gould, 1994; Stark et al., 1995). Colon cancer Consumption of tropical and subtropical fruits, and the associated vitamin C, carotene and fiber, have been reported to reduce the risk of colon cancer (Ziegler

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et al., 1981). Diets containing citrus fiber have been reported to reduce the risk of intestinal cancer. Weanling rats were fed semi-purified diets containing 5% fat and 15% citrus fiber, at seven weeks of age, all animals except vehicle-treated controls received weekly injections of 8 mg azoxymethane (AOM) kg−1 body weight for ten weeks, and the AOM- or vehicle-treated groups were autopsied 20 weeks after the last injection of AOM. The animals fed the citrus fiber diet and treated with AOM had a lower incidence (number of animals with tumors) and multiplicity (number of tumors/tumor-bearing animal) of colon tumors and tumors of the small intestine than did those fed the control diet and treated with AOM. The number of adenomas but not the number of adenocarcinomas was reduced in rats fed on the citrus pulp diet. Research has suggested a possible effect of almond consumption on cancer, including colon cancer (Davis et al., 2003). Breast cancer A meta-analysis of 26 prospective and retrospective studies (Gandini et al., 2000) confirmed the reduction of the risk of breast cancer with enhanced intake of fruit and vegetables, in contrast to a pooled analysis of eight prospective studies that indicated that fruit and vegetable consumption did not significantly reduce the risk of breast cancer (Smith-Warner et al., 2001). Garcia-Solis et al. (2008; 2009) studied the antineoplastic properties of some fruits and vegetables using in vivo and in vitro models. The effect of ‘Ataulfo’ mango fruit consumption was studied on chemically induced mammary carcinogenesis and plasma antioxidant capacity (AC) in rats treated with the carcinogen N-methyl-N-nitrosourea (MNU) (Garcia-Solis et al., 2008). Mango was administered in the drinking water (0.02–0.06 gmL−1) during both short-term and long-term periods to rats, and plasma antioxidant capacity was measured by ferric reducing/antioxidant power and total oxyradical scavenging capacity assays. Rats treated with MNU had no differences in mammary carcinogenesis (incidence, latency and number of tumors), and no differences in plasma antioxidant capacity. On the other hand, Garcia-Solis et al. (2009) screened (using methylthiazolydiphenyl-tetrazolium bromide assay) the antiproliferative activity of aqueous extracts of avocado, black sapote, guava, mango, cactus stems (cooked and raw), papaya, pineapple, four different prickly pear fruit, and grapes on the breast cancer cell line MCF-7. Only the papaya extract had a significant antiproliferative effect and there was no relationship between total phenolic content and AC with antiproliferative effect. These results suggested that each plant food has a unique combination in quantity and quality of phytochemicals which could determine its biological activity. The consumption of a mixture of phenolic compounds presented in purple grape juice inhibited mammary carcinogenesis in 7,12-dimethylbenzo[a]anthracene (DMBA) treated rats (Liu et al., 2005; Jung et al., 2006). However, the individual antioxidants studied in clinical trials, including β-carotene, vitamin C and vitamin E, do not appear to have consistent preventive effects comparable to the observed health benefits of diets rich in fruits and vegetables, suggesting that natural phytochemicals in fresh fruits and vegetables could be more effective than a dietary supplement.

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Lung cancer Goodman et al. (1992) concluded that some β-carotene rich fruits such as papaya, mango and yellow orange showed little influence on survival of lung cancer patients, and the intake of β-carotene before diagnosis of lung cancer did not affect the progression of the disease. 2.5.2 Cardiovascular disease (CVD) Reduction of cardiovascular and coronary heart diseases by consumption of nuts is well known (Yahia, 2010). The Nurses Health Study indicated that frequent nut consumption was associated with a reduction in the risk of suffering cardiovascular diseases (Yahia, 2010). Clinical studies have evaluated the effect of nut consumption on blood lipids and lipoproteins as well as several factors of coronary heart disease (CHD) risk (oxidation, inflammation, and vascular reactivity), finding protective effects against CHD and associated risk factors. Jenkins et al. (2008) reported that nut consumption improves the blood lipid profile and causes a reduction in the risk of CHD. A pooled analysis of four US epidemiologic studies showed that subjects with the highest nut intake had a risk of CHD 35% lower than that of other experimental groups (Kris-Etherton et al., 2008). The LDL cholesterol-lowering response caused by nut consumption is considerably high. Polyphenolic compounds and vitamin E in almonds are active in preventing the oxidation of LDL cholesterol (Millburry et al., 2002). Individuals who replaced a half of their daily fat intake with almonds or almond oil for some weeks showed reduced total and LDL cholesterol 4% and 6%, respectively, while HDL cholesterol increased by 6% (Hyson et al., 2002). Besides lipids, polyphenolic compounds and vitamin E, nuts contain other bioactive compounds that also could explain their protective effect on cardiovascular diseases (protein, fiber, K, Ca, Mg, phytosterols, resveratrol and arginine). All of these compounds also have relevance in human nutrition (Kris-Etherton et al., 2008). Avocados are considered as healthy food in terms of protection against heart disease due to their high content of mono- and polyunsaturated fat and low content of saturated lipids. Avocado fat has been shown to reduce blood cholesterol and preserve the level of high-density lipoproteins (Yahia, 2011a). Avocado enriched diet produced a significant reduction in low-density lipoproteins (LDL) and total cholesterol in patients with high cholesterol levels, while diets enriched with soy and sunflower did not change the total cholesterol concentrations (Carranza et al., 1997). Avocados also contain other protective compounds against cardiovascular diseases (chlorophyll, carotenoids, α-tocopherol and β-sitosterol). Avocado fat is an important source of energy, also important in human nutrition. The diverse classes and large amounts of phenolic compounds found in grapes were reported to play an important role in human health, lowering levels of lowdensity lipoprotein (Frankel et al., 1993; Tussedre et al., 1996). Extracts of fresh grapes and commercial grape juice inhibited human LDL oxidation from 22 to 60% and from 68 to 75% (Frankel et al., 1998). The LDL antioxidant activity

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correlated highly with the concentration of total phenolics for both grape extracts and commercial grape juices, and with the level of anthocyanins, flavonols, hydroxycinnamates and flavan-3-ols (Frankel et al., 1993; 1998). Cactus pear was also reported to exert protective effects against cardiovascular diseases, presumably as a consequence of its high content of antioxidants (Yahia, 2010b). Tesoriere et al. (2004) found that consumption of 500 g cactus pear (O. ficus-indica) pulp for two weeks reduced the levels markers of oxidative damage of plasma lipids, such as isoprostanes and malonaldehyde. The oxidative status of LDL, erythrocytes and the levels of plasma antioxidants increased (Tesoriere et al., 2004). 2.5.3 Diabetes mellitus Randomized controlled trials of patients with type 2 diabetes have confirmed the beneficial effects of nuts on blood lipids, also seen in non-diabetic subjects, but the trials have not reported improvement in A1c or other glycated proteins (Jenkins et al., 2008). Therefore, Jenkins et al. (2008) concluded that it is justified to consider the inclusion of nuts in the diets of individuals with diabetes in view of their potential to reduce cardiovascular risk, even though their ability to influence overall glycemic control remains to be established. Nettleton et al. (2008) characterized dietary patterns and their relation to incident type 2 diabetes in 5011 participants from the Multi-Ethnic Study of Atherosclerosis and found that high intake of nuts was associated with a 15% lower risk of diabetes. Some flavonoids, such as procyanidins, have antidiabetic properties because they improve altered glucose and oxidative metabolisms of diabetic states (Pinent et al., 2004). Extract of grape seed procyanidins (PE) administered orally to streptozotocin-induced diabetic rats resulted in an antihyperglycemic effect, which was significantly increased if PE administration was accompanied by a low insulin dose (Pinent et al., 2004). The antihyperglycemic effect of PE may be partially due to the insulinomimetic activity of procyanidins on insulin-sensitive cell lines. 2.5.4 Bone health Antioxidants in fruits and vegetables including vitamin C and ß-carotene reduce oxidative stress on bone mineral density, in addition to the potential role of some nutrients such as vitamin C and vitamin K that can promote bone cell and structural formation (Lanham-New, 2006). Some tropical and subtropical fruits are rich in potassium citrate and generate basic metabolites to help buffer acids and thereby may offset the need for bone dissolution and potentially preserve bone. Potassium intake was significantly and linearly associated with markers of bone turnover and femoral bone mineral density (Macdonald et al., 2005). Lin et al. (2003) indicated that high potassium, magnesium and calcium content in addition to antioxidants, phytochemicals and lower acidity of fruits could be important factors for bone health.

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2.5.5 Arthritis Dietary antioxidants and anti-inflammatory components in food are thought to be important in reducing the risk or improving the course of rheumatoid arthritis (RA), and therefore tropical and subtropical fruit can be associated with reduced risk of RA (Yahia, 2010). A study involving 29 368 married women from the US, predominantly white, average age 61.4 years, over 11 years, indicated that total fruit consumption (> 83 servings per month) was associated with reduced risk of RA (Cerhan et al., 2003), oranges were the only individual fruit linked to reduced incidence of RA, and β-cryptoxanthin, a corotenoid found in this fruit, was consistently highly protective. 2.5.6 Birth defects The effect of folic acid supplementation on reducing the risk of neural tube defects of the brain and spine, including spina bifida and anencephaly, is well documented (Eichholzer et al., 2006). Tropical and subtropical fruits are an important source of dietary folate and their consumption has been associated with increased plasma levels of folate. 2.5.7 Diverticulosis Studies have established an association between low fiber diets and the presence of diverticulosis (Aldoori and Rayan-Harschman, 2002). The intake of fruit fiber was inversely associated with risk of diverticulosis in a large prospective study of male health professionals, and therefore a high fiber diet including tropical and subtropical fruits is considered to be an important aspect of therapy for diverticulosis (American Dietetic Association, 2002). 2.5.8 Aging and cognition Oxidative stress and inflammation are considered significant mediators in healthy aging of the brain and in age-related neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease (Shukitt-Hale et al., 2006; Yahia, 2010). Animal and human studies have suggested that fruits and vegetables have the potential to mitigate some age-related processes, primarily due to the antioxidant and anti-inflammatory properties of several phytochemicals. An in vitro study has suggested that some classes of phytochemicals also act on cell signaling and thus may protect against aging by mechanisms other than oxidative and inflammatory processes (William et al., 2004). Fruit extracts have been demonstrated to reverse or retard various age-related cognitive and motor deficits in rats (Lau et al., 2005). Aging rats provided with ‘Concord’ grape juice at low concentration (10%) for nine weeks improved cognitive performance, while high (50%) concentration improved motor performance (Shukitt-Hale et al., 2006). ‘Concord’ grape and juice contain a variety of flavonoids, and 10% grape juice supplementation was reported to be associated with the most effective increase in muscarinic receptor sensitivity in aging rats.

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Preharvest factors affecting accumulation of nutritional and health components

The importance of fruit bioactive metabolites as protective compounds in human nutrition and health has been widely recognized. Interestingly, the same metabolites are also essential for the health of the fruit itself (Yahia, 2010). Tropical and subtropical fruits provide an optimal mixture of antioxidants; however, their qualitative and quantitative content can be affected by different conditions that could change negatively the nutraceutical value of these fruits. Many preharvest factors affect the nutritional and health components in tropical and subtropical fruits. The influence of climatic conditions, cultural practices, ripening stage at harvest, season, geographical origin and genotype on healthpromoting components of several (especially temperate) fruit has been extensively studied during the past decade. However, cultural practices affecting nutritional/ health quality of fruit such as soil and substrate properties, growing systems (field, greenhouse, organic farming), mulch and covering material, grafting and pruning, irrigation, fertilization, salinity, growth promoters, mechanical and pest injuries and maturity at harvest need to be studied in more detail in tropical and subtropical fruits. Considering the impact of environment and crop management practices on fruit quality, light is often the major factor. Fruit from plants grown under high light intensity, especially those grown in the tropics, generally have high vitamin C, carotenoids such as lycopene and β-carotene, and phenols, while fruit from plants grown under low light have a lower content. This factor can be detrimental in the synthesis of some phytochemical compounds in some tropical fruits. Although light is not essential for the synthesis of ascorbic acid, its amount and intensity during the growing season influences the amount of ascorbic acid formed, because ascorbic acid is synthesized from sugars supplied through photosynthesis (Lee and Kader, 2000). Within the same plant, exterior fruits exposed to maximum sunlight usually contain higher amounts of vitamin C than interior and shaded fruits (Lee and Kader, 2000). Similarly, even though the formation of carotenoids in ripening fruit does not require induction by light, shaded fruits usually have lower carotenoid content than exposed fruits (Merzlyak et al., 2002). Content of bioactive compounds in tropical and subtropical fruits (predominantly climacteric) is markedly altered by ripening (Robles-Sánchez et al., 2007). Ethylene increase in fruits leads to numerous chemical changes, including biosynthesis and degradation of bioactive compounds. Carotenoids accumulation in mangoes increases exponentially during ripening (Ornelas-Paz et al., 2008a). Manthey and Perkins-Veazie (2009) demonstrated that the levels of mangiferin and ellagic acid in mangoes increased from 227 to 996 and from 25.7 to 187 μg 100 g−1 FW as harvest season (as maturity) advanced, respectively. However, González-Aguilar et al. (2008) found that the antioxidant capacity of mangoes remains constant during ripening, suggesting that once mangoes reach maturity on the tree, their phytochemistry relating to radical scavenging activity

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barely changes during ripening (González-Aguilar et al., 2008). Similarly, Manthey and Perkins-Veazie (2009) did not report any effect of the stage of ripening on antioxidant activity of mango. Ripening also alters the content of bioactive compounds in papaya. Rivera-Pastrana et al. (2010) demonstrated that the major carotenoids in ‘Maradol’ papaya are lycopene (0.0015–0.012 g kg−1 fresh weight) and β-cryptoxanthin (0.0031–0.0080 g kg−1 fresh weight), which tend to increase during ripening. Gayosso-García et al. (2010) demonstrated that the stage of ripening of ‘Maradol’ papaya influenced β-carotene and phenolic content, and consequently the antioxidant capacity, measured by DPPH, ABTS and ORAC methods. The highest antioxidant capacity was observed in the mature-green stage, which coincided with the higher phenolic content of fruit (Gayosso-García et al., 2010). Rivera-Pastrana et al. (2010) reported that the content of major phenols (ferulic acid, caffeic acid and rutin) in the exocarp of ‘Maradol’ papaya decreased during ripening. The concentration range for these compounds were 1.33–163, 0.46–0.68 and 0.10–0.16 g kg−1 dry weight for ferulic acid, caffeic acid and rutin, respectively (Rivera-Pastrana et al., 2010). The decrease in phenolic compounds during fruit ripening was also reported in banana and mango (Abu-Goukh and Abu-Sarra, 1993; Ibrahim et al., 1994). During longan fruit development, the content of total phenolics decreased rapidly and then increased while the content of (–)-epicatechin tended to decrease (Yu et al., 2010). Recently, Qing-Yi et al. (2009) reported a significant increase in total carotenoid and fat content in avocados as the season progressed from January to September. The total content of carotenoids was highly correlated with the total fat content (Qing-Yi et al., 2009). The content of ascorbic acid and phenolic compounds in pulp and peel of guavas progressively decreased during ripening (Bashir and Abu-Goukh, 2003). Similar findings have been reported for several other tropical and subtropical fruits. The genotype influences the chemical composition in several fruits. White-fleshed guava contains more sugars than the pink-fleshed type (Bashir and Abu-Goukh, 2003). Ribeiro et al. (2007) reported that phenolic compounds, ascorbate and β-carotene of mangoes differ considerably between cultivars. ‘Haden’, ‘Tommy Atkins’, ‘Palmer’ and ‘Uba’ mangoes represent a potential source of natural antioxidants, but ‘Uba’ mango showed better results with the highest levels of antioxidants. Ornelas-Paz et al. (2007) compared the carotenoids profile in fruit of seven Mexican mango cultivars and found that the most abundant carotenoid in fruit of ‘Ataulfo’, ‘Criollo’ and ‘Haden’ was all-trans-β-carotene, while in the other cultivars all-trans-violaxanthin (as dibutyrate) was predominant. The content of all-trans-violaxanthin was higher than 9-cis-violaxanthin (as dibutyrates) in all cultivars. ‘Haden’ mangoes had high content of the three carotenoids, and its all-trans-β-carotene concentration was the highest compared to all other cultivars, while ‘Ataulfo’ mango showed the lowest amount of xanthophylls compared to the other cultivars (Ornelas-Paz et al., 2007). In general, α-tocopherol content in mango fruit is independent of cultivar although ‘Haden’ and ‘Tommy Atkins’ contain a slightly higher content of this compound (OrnelasPaz et al., 2007). Gonzalez-Aguilar et al. (2007a;b) reported that ‘Ataulfo’

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mangoes contain higher amounts of vitamin C and carotenoids as compared with ‘Keitt’ and ‘Kent’ mangoes. Manthey and Perkins-Veazie (2009) studied the effect of cultivar on phytochemicals of different mango cultivars. They found that ascorbic acid ranged from 11 to 134 mg 100 g−1 of pulp puree, and β-carotene varied from 5 to 30 mg kg−1 among the five varieties. Total phenolic content ranged from 19.5 to 166.7 mg of gallic acid equivalents (GAE) 100 g−1 of puree. ‘Tommy Atkins’, ‘Kent’, ‘Keitt’ and ‘Haden’ mangoes had similar total phenolic contents, averaging 31.2 mg GAE 100 g−1 of puree, whereas ‘Ataulfo’ mango contained substantially higher values. Similar trends were observed in the DPPH radical scavenging activities among the five varieties (Manthey and Perkins-Veazie et al., 2009). Harvest season and geographical origin of fruit also alter the phytochemical content in fruits. For example, Gonzalez et al. (2005) observed that vitamin C content in of pineapple ‘Cayena Lisa’ varied with the harvest season. In contrast, Manthey and Perkins-Veazie (2009) did not report any effect of harvest location on ascorbic acid, total phenolic and DPPH radical scavenging in mango. Similarly, Qing-Yi et al. (2009) found that Hass avocados grown in different regions of southern California have a similar phytochemical profile.

2.7

Postharvest factors affecting nutritional and health components

Recently, due to health awareness campaigns, the general public has become more interested in foods that support and promote health. This trend has resulted in consumers wanting products with high health-promoting compounds rather than having superior external quality attributes as was previously the case. However, many postharvest factors, treatments and techniques can affect the nutritional and health components in tropical and subtropical fruits. Major research has been done focusing on the effect of postharvest treatments on preserving sensorial quality and assuring safety of fresh tropical and subtropical fruits, and some research has been done on the possible changes induced by postharvest treatments on nutraceutical value of tropical and subtropical fruits. The major factors that positively affect phytochemical content in postharvest fruit have been reported recently. Amarowicz et al. (2009) and González-Aguilar et al. (2010) reviewed the influence of postharvest processing and storage on the content bioactive compounds, including phenolic acids and flavonoids, β-carotene, vitamin C, vitamin E and antioxidant capacity, in different foods. However, they do not cover adequately the effects of these treatments on tropical and subtropical fruits. After harvest, tropical fruits are commonly transported to packinghouses, and delivered either to the fresh market or to processing plants. Fruits that are disinfected, cleaned and properly handled in the postharvest chain do not lose significant quantities of phytochemicals, but innapropiate handling can cause significant nutritional losses. Excessive sunlight and high temperature increase the activity of metabolic reactions and consequently enhance the senescence

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processes, diminishing the amount of bioactive compounds. Processing inevitably induces qualitative and quantitative changes on phytochemical content of fruits. The content of total phenols and vitamin C decrease significantly with processing (Ninfali and Bacchiocca, 2004). The antioxidant capacity, when measured on each stock of processed fruits, describes the extent of quality loss. Many variables occur during processing, and producers wishing to provide consumers with high quality products should be aware of total antioxidant capacity and add this value to their packaging labels as proof of their attention to nutritional quality. Among the important postharvest factors affecting the content of bioactive compounds are storage temperature, controlled/modified atmospheres, edible coatings, heat treatments, cutting, use of natural compounds, irradiation and processing. 2.7.1 Storage temperature Temperature has a profound effect on fruit metabolism and thus on its content of bioactive compounds. Lower temperatures slow respiration rates, as well as ripening and senescence processes, and therefore reduce the degradation of nutritional and health components, and prolong the postharvest life of fruits (González-Aguilar et al., 2004). The metabolic effect of temperature can reflect on the phytochemical status of the tropical and subtropical fruits. Many subtropical fruits and most tropical fruits are very susceptible to low temperature storage. These fruits develop different chilling symptoms that become apparent after transferring the fruit to higher temperatures. However, the changes in the phytochemical compounds that occur during these events are not well documented. Antioxidant content of ‘Maradol’ papaya was influenced by postharvest storage temperature with the exception of β-carotene and rutin (Rivera-Pastrana et al., 2010). Ripe papaya stored at 25°C possessed a higher nutritional potential than those stored at 1°C. Low (chilling) temperature (1°C) negatively affected the content of major carotenoids, except β-carotene, and contributed to maintaining or increasing ferulic and caffeic acid levels, as compared to high (safe) temperature (25°C). Similarly, total phenolic content in banana decreased as the storage temperature increased (Aziz et al., 1976). Storage of loquat fruit at 20–30°C caused an increase in sucrose and cryptoxanthin as compared with lower temperatures, and total phenolics did not change at low storage temperatures (≤10°C) (Ding et al., 1998). It has been observed that during cold storage antioxidant activity and total phenolic content changes to a different extent depending on the type of the fruit and other factors (González-Aguilar et al., 2008). 2.7.2 Controlled/modified atmospheres (CA/MA) and edible coatings The effects of CA and MA technologies are well documented to extend the postharvest life of fruits including those of tropical and subtropical origin (Yahia, 2008). These effects include reduction of respiration rate, inhibition of ethylene production and action, retardation of ripening, and maintenance of nutritional and

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sensory quality (Singh and Pal, 2008; Yahia, 2008). These techniques alter the O2, CO2 and/or C2H4 concentrations in the atmosphere surrounding the commodity to produce an atmosphere composition different from that of the normal air. In general, atmospheric treatment within the ranges tolerated by the commodity reduces physiological and biochemical changes, including losses of vitamin C, chlorophylls, carotenoids of fruit and vegetables during storage. Studies on the effect of CA/MA on nutritional quality are limited. Kader (2008) reviewed the impact of this technique on the major nutrients of fruit and vegetables. For most commodities tested, 1–4 kPa O2 generally slows AA degradation through prevention of oxidation. The effects of carbon dioxide on AA may be positive or negative depending upon the commodity, CO2 concentration, duration of exposure, and temperature. CA conditions that delay ripening of fruits result in delayed synthesis of carotenoids, such as β-carotene in mango, but the synthesis of this compound was recovered upon transfer of the fruit to air at ripening temperatures (15–25°C). In general, high CO2 can accelerate losses of AA and reduce the rate of postharvest synthesis of phenolic compounds, which can be desirable (no increase in browning potential and astringency) or undesirable (no increase in antioxidant activity) (Kader, 2009). Litchi fruit stored in air had lower anthocyanin content throughout storage in MA and CA at 38°C. However, there are contrasting effects of MA and CA of fruit indicating that various plant matrices may behave differently even under the same or slightly modified storage conditions. Maintaining the optimal ranges of O2, CO2 and ethylene concentrations around the commodity extends its postharvest life by about 50%–100% relative to air control, including its nutritional quality. Montero-Calderon et al. (2010) studied the effect of low O2 (12% O2 in combination with 1% CO2) and high O2 (38% O2) on fresh-cut pineapple fruit and found an increment of antioxidant capacity, total phenolics, volatile compounds and vitamin C content in low O2 compared with high O2. These results suggest that optimal conditions of CA/MA can improve the nutritional value of tropical fruits. Antioxidant phytochemicals and quality of mango fruit are affected by hot water immersion and controlled atmosphere storage (Kim et al., 2007). The concentration of gallic acid and hydrolysable tannins and their resultant antioxidant capacity were unaffected by the hot water treatment (46°C for 75 minutes), while total polyphenolics naturally decreased throughout fruit ripening, regardless of hot water treatment or storage atmosphere. However, the overall decline in polyphenolic concentration was inhibited by the CA treatments (3% O2 + 97% N2, or 3% O2 + 10% CO2 + 87% N2) as a result of delayed ripening. Litchi packed with the modified atmosphere system PropaFreshTM PFAM maintained proper levels of sugars and individual anthocyanins (Somboonkaew and Terry, 2010). Vitamin C content in longan fruit (cv. Shixia) decreased rapidly during CA storage under several O2 levels (4–70%) (Tian et al., 2002). Changes of ascorbic acid and total phenols in guava during storage were retarded by CA (2.5–1 kPa O2 with 2.5–10 kPa CO2, balance N2) (Singh and Pal, 2008). Vigneault and Artes-Hernandez (2007) reviewed the literature on gas treatment for increasing

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the phytochemical content of fruits and vegetables and concluded that much more research is needed before guidelines for choosing gas treatments to enhance the phytochemical content of fruit can be developed. Some edible coatings, such as chitosan, have antibrowning characteristics and can maintain tissue firmness and reduce microbial decay of harvested fruits for extended periods. Gonzalez-Aguilar et al. (2009) found that chitosan coating is effective in the preservation of fresh-cut papaya. Liu et al. (2007) used chitosan to control gray mold and blue mold in tomato fruit stored at 25°C and 2°C. Chitosan has the potential for inducing defense-related enzymes such as polyphenol oxidase (PPO), peroxidase (POD) and polyphenol ammonia layase (PAL), but the possible mechanism of action is little understood. Robles-Sanchez et al. (2009) reported that dipping treatments containing ascorbic acid and calcium lactate affected total phenols, vitamin C, vitamin E, and gallic and p-OH-benzoic acids, whereas storage time affected all the parameters studied. The initial vitamin C values were of 11 and 44 mg 100 g−1 of fresh weight for control and treated fresh-cut mango cubes, respectively. As expected, a fourfold increase in vitamin C was observed immediately after the treatment with AA + CA + CaCl2. However, in this study vitamin C losses during storage of fresh-cut mangoes were minimal in both control and treated tissue. A higher level of vitamin C in treated fresh-cut cubes was observed compared to controls. The use of vacuum impregnation and edible coatings containing antioxidants is another option to overcome the nutritional losses of fresh-cut fruits during storage. Therefore, use of CA/MA and edible coatings for extending the shelf-life of fresh fruits, including those of tropical and subtropical origin, is widely recognized. However, more research needs to be carried out on the potential of these technologies to improve the nutrimental quality of fruits, especially their antioxidant status. 2.7.3 Heat treatments (HT) Different types of heat treatments (hot air or hot water) are commercially used for different postharvest purposes in different tropical and subtropical fruits. Heat tolerance of different fruits depends on species, genotype, stage of fruit maturity, type and severity of HT applied, and whether postharvest conditioning treatments have been given before or after a HT (Jacobi et al., 2001). Several studies have connected heat tolerance with the increase of heat shock proteins (HSP’s), antioxidants enzymes and secondary metabolites such as carotenoids and phenolic compounds. Ghasemnezhad et al. (2008) found an increase in superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity after hot water treatments in mandarins. Overall, no significant differences in antioxidant capacity were found following the hot water treatment or low-temperature storage with values ranging from 41 to 51 TE g−1 dry weight. Only small differences were found during ripening, and no clear trend in radical scavenging properties was observed as the fruit progressed from green to a full ripe stage by day 16. The increases observed in hydrolysable tannins and carotenoids did not impact

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the overall antioxidant properties as the fruit ripened. No structural information was obtained for the hydrolyzable tannins (that is, number of galloyl groups) to determine their antioxidant potential, but compounds such as carotenoids and P-hydroxybenzoic present in the ripe fruit are known to be poor peroxyl radical scavengers when using polar in vitro testing systems. When mango fruit experience a thermal quarantine treatment and are exposed to low temperatures, enough to induce chill injury, the overall effect on antioxidant phytochemical constituents is relatively small despite adverse effects on aesthetic quality (Talcott et al., 2005). These data indicated that hot water treatment may accelerate fruit ripening based on carotenoid biosynthesis and potentially limit shelf-life, whereas hot water treatments combined with extended low-temperature storage hindered carotenoid development that was attributed to either heat and/or chill injury. Talcott et al. (2006) found an increase in polyphenols and carotenoids and better antioxidant capacity in hot-water-treated compared with untreated mangoes. Similarly, Djioua et al. (2009) found an increase in total carotenoids and vitamin C content in mango fruit induced by the hot water dip treatment. Heat treatment was also demonstrated to accelerate mango ripening, and carotenoid concentration was significantly increased due to hot water treatment (Vazquez-Salinas et al., 1985; Jacobi and Giles, 1997). In mango fruit, hot water treatment (at 42°C for 24 h) inhibited polyphenol oxidase (PPO) and peroxidase (PE) activities leading to delayed anthocyanin synthesis, and thus protected color pigment changes by maintaining the anthocyanins in their red-pigmented form with high antioxidative activity in postharvest (Fallik, 2004). A possible activation of the antioxidative system is suggested by the further induced superoxide dismutase (SOD) activity and suppression of peroxidase activity following heat treatment of papaya (Huajaikaew et al., 2005). These results suggested that adequate HT’s can prolong postharvest life of some fruits and can even promote an increase of some bioactive compounds. However, the potential effects of HTs on tropical and subtropical fruits still need to be investigated in more detail with regard to their effect on the antioxidant status. 2.7.4 Effect of cutting Fresh-cut tropical and subtropical fruits are cut in a wide variety of shapes, and these could influence the degree of damage caused by the wound (Rivera-Lopez et al., 2005). Minimal (fresh-cut) processing includes the unit operation of size reduction, and a given shape has to be provided to the product depending on its final use. Cutting is one of the most delicate steps, since it triggers degradative oxidation as a consequence of the decompartmentalization and contact of the phenolic substrates, present in the vacuoles, with the cytoplasmatic oxidases (Varoquaux and Mazollier, 2002). Therefore, phenolic concentration and antioxidant capacity may change significantly in comparison with the fresh, intact products. These parameters also seem to be relevant in determining the

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bioavailability of phenolic compounds (Robles et al., 2007). Different minimal processing techniques have been applied to tropical and subtropical fruit and its effect on nutritional and phytochemical contents in comparison to whole fruits has been reported by different authors. Gil et al. (2006) observed significant losses in ascorbic acid but an increase in dehydroascorbic acid throughout storage of freshcut pineapple, resulting in greater ascorbic acid content of fresh-cut versus whole fruit. Fresh-cut mango cubes had a decrease in ascorbic acid and an increase in dehydroascorbic acid during storage, maintaining the content of ascorbic acid close to the initial value for both fresh-cut and whole fruit, except at day nine when the high vitamin C contents of whole and fresh-cut fruit were rather different between them (Gil et al., 2006). No significant changes in β-carotene were observed due to the effect of storage temperature and cutting shape. In another study, ascorbic acid content was not affected by cutting shape for both cubes and slices of fresh-cut papaya (Rivera-Lopez et al., 2005). Ascorbic acid content of cubes and slices stored at 5°C decreased by 29.6 and 26.38% after 18 days of storage, respectively. Cubes and slices stored at 10°C decreased by 27.30% and 38.92%, respectively, from their initial ascorbic acid content after 14 days of storage (Rivera-Lopez et al., 2005). Even though this study did not observe significant differences among the cutting shapes of papaya fruit, the cutting step per se could affect the ascorbic acid content. No significant effect of the cutting shape on the antioxidant capacity expressed as ORAC value was observed in fresh-cut papaya fruit (Rivera-Lopez et al., 2005) but storage temperature significantly affected it. Fresh-cut papaya cubes and slices changed slightly during storage at 5°C. However, significant reductions in ORAC values were found in fresh-cut papaya at 10°C and 20°C (Rivera-Lopez et al., 2005). The cutting shape of fresh-cut papaya fruit was not shown to have immediate effect on β-carotene content (Rivera-Lopez et al., 2005). Fresh-cut papaya cubes and slices stored at 5°C did not present any change in β-carotene content during ten days of storage. No changes were observed in β-carotene content after six days of storage at 10°C; however, after 14 days of storage, there was a depletion of 62% for cubes and 63.4% for papaya slices. Fresh-cut papaya cubes and slices stored at 20°C showed the highest β-carotene losses. At this temperature and after six days of storage, β-carotene content of cubes and slices decreased by 57.4% and 60.63%, respectively. Minimal processing steps are expected to induce a rapid enzymatic depletion of several natural antioxidants. Depletion of antioxidant capacity in cubed and sliced papaya fruit could be associated with depletion of both ascorbic acid and β-carotene, but in general, the highest loss of these important nutrients was reached before the product was unacceptable or spoiled (Rivera-Lopez et al., 2005). 2.7.5 Use of natural compounds There are several natural compounds that exhibit positive effects on fruit handling and quality. Among these the most studied are volatile compounds (e.g.

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acetaldehyde, benzaldehyde, hexanal) acetic acid, jasmonates, glucosinolates, chitosan, active principles of some plants, and plant extracts, among others (Tripathi and Dubey, 2004). It has been noticed that jasmonates are associated with defense response in plants (Turner et al., 2002). Jasmonates play an important role as signal molecules in plant defence responses against pathogen attack, induce the synthesis of antioxidant molecules such as vitamin C, phenolic compounds and increase the activity of enzymatic antioxidant systems (Chanjirakul et al., 2006). GonzalezAguilar et al. (2004) found that methyl jasmonate (MJ, 10−5 and 10−4 M) retarded chilling injury in guava fruit after five, ten, and fifteen days at 5°C plus two days at 25°C, maintained better appearance, and increased the activity of phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) enzymes which improve the antioxidant status (Pinsky et al., 2006). MJ at 10−5 M or 10−4 M treatment increased sugar concentrations in mangoes and guava fruit stored at 5°C that were still ripening, and the increase of sugar in MJ-treated fruit was concluded to be part of the plant defense response system (Gonzalez-Aguilar et al., 2004). A positive correlation between MJ treatment and the increase of ascorbic acid and of PAL activity, which is associated with a plant’s defense system, has been observed in guava fruit (Gonzalez-Aguilar et al., 2004). These facts suggest a connection among jasmonates, ascorbic acid, and polyphenols in the inhibition of chilling injury. Changes in antioxidant capacity and the antioxidant enzymatic system in fruits treated with MJ have been reported. Cao et al. (2009) observed that MJ increase the content of organic acids, total phenolics, total flavonoids and the activity of SOD, CAT and APX in loquat fruit, and the treatment also maintained significantly higher antioxidant activity. The reaction of jasmonates to environmental stress has also been observed in drought conditions (Kondo et al., 2005). SOD catalyzes the dismutation of O2 to O2− and H2O2. SOD activities and endogenous jasmonate levels in the skin of fruit that were stored at 12°C were higher than those at 6°C. These results suggest a link between jasmonates, SOD activity, and O2 scavenging activity. The possible relation of the antioxidant enzymes and bioactive compounds present in tropical and subtropical fruits with the antioxidant capacity was not widely reported. It has been observed that the use of antioxidants to prevent browning and deterioration of fresh-cut fruits enhances the antioxidant status. Changes in ascorbic acid of pineapple slices treated with different antibrowning agents have been evaluated (González-Aguilar et al., 2005). No significant changes in ascorbic acid levels were observed in the control or slices treated with acetylcysteine during the storage period at 10°C (Gonzalez-Aguilar et al., 2005). In contrast, it has been found that dehydrated pineapple and guava pretreated with cysteine hydrochloride had high ascorbic acid retention and reduced color change during storage (Mohamed et al., 1993). As is expected, ascorbic acid content was significantly increased after treatments with 0.05 M of ascorbic acid applied to fresh-cut pineapples (Gonzalez-Aguilar et al., 2005). However, after three days, ascorbic acid content of fresh-cut pineapple treated with ascorbic acid decreased continuously from 45 to 18 mg 100 g−1 at the end of the storage period

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(Gonzalez-Aguilar et al., 2005). It has been reported that dipping treatments containing vitamin C, commonly used to prevent browning, increase the total antioxidant capacity of fresh-cut produce due to the addition of antioxidants as components of the dip solutions (Soliva-Fortuny and Martin-Belloso, 2003). Studies on the effects of these treatments in conjunction with other novel approaches, such as edible coating compounds, are scarce for tropical and subtropical fruits and need further investigation. 2.7.6 Use of ultraviolet (UV) light UV-C irradiation (240nm–280nm) can be applied at lethal and sub-lethal doses. The detrimental effect of UV-C includes tissue structural damage, changes in cytomorphology and water permeability of inner epidermal cells (LichtscheidlSchultz, 1985). Nevertheless, low doses of UV-C irradiation stimulated beneficial reactions in biological organs, a phenomenon known as hormesis (Shama, 2007). It has been reported that hormetic doses of UV-C can prolong the postharvest life and maintain the quality of tropical fruits. These effects include delay of deterioration, senescence process and fruit ripening (Gonzalez-Aguilar et al., 2001; 2007). These authors observed an increase in PAL enzymatic activity in guava tissue as a result of the UV-C treatments which in consequence can enhance flavonoid biosynthesis. Results obtained in this study reinforce the evidence of the efficacy of UV-C treatment to prevent deterioration and maintain quality of different crops, including some mango varieties (González-Aguilar et al., 2001). However, the analysis of specific phytoalexins induced as a response to UV-C treatment in mango is needed to elucidate the possible mode of action of this treatment. The induction of the plant defense system can also trigger the accumulation of these compounds which exhibit antioxidant potential, improving the nutritional status of the fruit (Gonzalez-Aguilar et al., 2007). On the other hand, the phenolic content of fresh-cut mangoes treated with UV-C irradiation increased, but significant losses of vitamin C were observed. These treatments could stimulate or inhibit the synthesis of bioactive compounds that contribute differentially to the antioxidant capacity of fruits (González-Aguilar et al., 2007). Alothman et al. (2009) found an increase in phenols and flavonoids in guava and banana after 30 minutes exposure to UV-C light, contrary to the decrease found in pineapple and reduction in vitamin C in mango fruit (González-Aguilar et al., 2007). Jiang et al. (2010) applied a dose of 4 kJ m−2 for 10 minutes and showed an increase in the antioxidant enzyme activity of CAT, SOD, APX and glutathione reductase (GR). Therefore, the accumulation of antioxidant compounds and nutraceutical quality of fruits treated by UV-C irradiation depends on the doses applied. The biosynthesis of phenolic compounds is affected by gamma and ultraviolet irradiation due to effects on activity of PAL, an effect which was found in several fruits and vegetables such as citrus (Oufedjikh et al., 2000). The increased PAL activity promotes the biosynthesis of phenolic compounds such as flavanones in citrus (Oufedjikh et al., 2000). In addition to PAL induction, ultraviolet irradiation increases the activity of other enzymes involved in flavonoid synthesis, such as

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chalcone synthase, chalcone isomerase and dihydroflavonol-4-reductase (TomasBarberan and Espin, 2001). Flavonoids have various physiological functions such as antioxidative or antitumor activity as well as a UV protective effect (Higashio et al., 2001). In previous work it was reported that UV-C irradiation processing of fresh-cut honey pineapple, banana ‘Pisang mas’, and guavas leads to an increase in antioxidants, polyphenols, and flavonoids. Hence, apart from the application of UV for microbial safety at industrial levels, this novel technology can also be exploited for enhancement of health promoting compounds. However, the responsiveness of harvested horticultural produce to UV-C treatment declines with increasing fruit ripening, and thus depends on the harvest time (Terry and Joyce, 2004). Similar results were reported for grapefruits treated with gamma irradiation (Patil et al., 2004). Low doses (≤200 Gy) of irradiation are recommended for enhancing health-promoting compounds (e.g., flavanones, β-carotene, lycopene and ascorbic acid content) in early season grapefruit, while higher doses (400–700 Gy) showed detrimental effects. Gamma irradiation can cause changes to both macro and micronutrients in foods, depending on the irradiation dose. The available research indicates, however, that carbohydrates, proteins, fatty acids, minerals and trace elements in tropical fruits undergo very minimal alteration during irradiation (www. foodstandards.gov.au). The safety of irradiating tropical fruits has been examined, and available studies on fruits indicate that there are no safety concerns (www. foodstandards.gov.au). There are no changes to the composition of the fruits following irradiation that are likely to cause public health and safety concerns. Irradiation of tropical fruits up to a maximum of 1 kGy (kiloGrey) and employing Good Manufacturing/Irradiation Practices is considered safe for Australian and New Zealand consumers (www.foodstandards.gov.au). Irradiation with 2 kGy had no significant effect on total vitamin C and total carotenoid content of pineapple samples. During the storage, however, vitamin C showed a significant decrease in both control and irradiated samples. Total carotenoids were stable to irradiation and did not show any decrease during the storage period of 12 days. 2.7.7 Effects of processing Interest and demand for tropical fruits and vegetables is increasing worldwide, and therefore as a result, the tropical fruit industry continues searching for new processing methods to increase the diversity of available products. The emphasis of this industry is on the fresh market, which is currently much more profitable than the processing market. However, the fresh-cut industry for tropical fruits is increasing and demanded by different international markets. Also, a significant percentage of several important tropical fruit crops are unsuitable for fresh market sales, primarily due to various appearance defects and short postharvest life, and therefore different processed products are excellent alternatives. Several tropical fruits are processed as many different products. The use of ‘nonthermal sterilization techniques,’ which include high-intensity pulsed electric fields (PEF), high hydrostatic pressures (HPP), and ionizing

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(gamma) radiation (IR), has increased lately. Significant information is available on the modes of action of the different techniques against spoilage and pathogenic microorganisms or on their effectiveness on the microbial load reduction in model and real systems (Corbo et al., 2009). However, studies assessing the effect of these emerging technologies on degradation of nutrients and bioactive compounds of food products are still not enough. González Aguilar et al. (2010) reported the most recent studies on this topic with emphasis on the effect on the most important bioactive compounds. In general, non-thermal treatments induce a slight loss of bioactive compounds in plant foods and may even enhance their recovery and retention throughout storage. Emerging technologies have different effects on the bioactive compounds. In processed juices, phenolic compounds were far more stable than vitamin C, showing retention/recovery values of 86–140%, anthocyanins showed the lowest recovery rates while carotenoids showed good retention rates (86–100%). Fermentation of noni fruit (Morinda citrifolia L.) for three months resulted in a loss of more than 90% free-radical-scavenging activity (RSA) while dehydration at 50°C reduced this variable by 20% (Yang et al., 2007). Storage of noni juice or powder at −18°C and 4°C for three months decreased RSA by 10–55%. The reduction of RSA of noni juice or purée during heat treatment or dehydration was much greater than the reduction of total phenols (Yang et al., 2007). The processed products (ready-to-drink juice, concentrated juice, frozen pulp) of acerola, cashew-apple and pitanga had appreciably lower flavonol levels than the unprocessed fruit, indicating losses during processing (Hoffmann-Ribani et al., 2009). Antioxidant activity and vitamin C concentrations in melon were decreased by HPP and these losses were cultivar-dependent for vitamin C. Levels of β-carotene were significantly increased (Wolbang et al., 2008). Carotenoids and anthocyanins decreased progressively in pineapple and papaya as the blanching temperature and time increased. Pretreatment with sodium metabisulphite prevented carotenoids from oxidation but caused bleaching of anthocyanins (Sian and Ishak, 1991). Kaya et al. (2010) studied the effect of drying temperature and moisture on vitamin C content in kiwifruit. They demonstrated that increasing drying temperature decreased vitamin C, its retention was improved by increasing moisture levels of drying air. Pasterurization of mango puree induced changes of trans to cis isomerisation of β-carotene, but vitamin A losses did not exceed 15.4% (Vásquez-Caicedo et al., 2007). There has been little research on the impact of HHP on the nutritional and health promoting properties of foods (McInerney et al., 2007). It has been generally known that high pressure has very little effect on low molecular weight compounds such as flavour compounds, vitamins and pigments compared to thermal processes. This effect is particularly important in salads, as most vegetables are rich sources of antioxidant compounds, pigments and vitamins. Butz et al. (2002) studied the effect of 600 MPa pressure in combination with elevated temperatures on the pigment and vitamin content of three vegetables. Extractable carotenoids and lycopene contents were improved in pressurized citrus and tomato juice (500 MPa, 10 minutes) as compared with fresh juice, and they also retained more vitamin C content than was the case following thermal

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processing (Polydera et al., 2003). Model multivitamin systems containing varied levels of water-soluble vitamins such as ascorbic acid, thiamin and vitamin B6 (pyridoxal), and food systems containing naturally occurring levels of vitamin C were subjected to pressures ranging between 200 and 600 MPa for 30 minutes to determine the effect on vitamin retention. In the model systems observed, ascorbic acid losses were close to 12% while in food material, these losses were insignificant. Compared to conventional sterilization processes, high-pressure treatments retained the vitamins better. Thiamin and pyridoxal in the model system were unaffected by high-pressure processing (Sancho et al., 1999). These findings confirm the fact that high pressure has minimal effect on nutrients in foods. High-pressure processed products are commercially available in the United States, European, and Japanese retail markets. Examples of high-pressure processed products commercially available in the United States include fruit smoothies, guacamole, ready meals with vegetables, fruit juices, among others. The case of guacamole has been a successful application, and volume of this product in the US market has been significantly increased in the past five years. However, more studies involving HHP treatments of tropical fruits will be necessary in order to develop an effective use of this technology, reducing waste, especially in developing countries, and maintaining original fruit characteristics. The use of byproducts of tropical fruits for different purposes has increased considerably, and it is very important to bear in mind that some parts of the fruit may contain compounds that can cause different disorders in consumers. Mango allergens were shown to be very stable during technological processing. Irrespective of enzymatic matrix decomposition, mechanical tissue disintegration and heating during peeling, mash treatment, and pasteurization, significant loss of allergenicity could not be observed in the extracts of mango purees and nectars (Dube et al., 2004).

2.8

Enhancement of nutritional and health components in tropical and subtropical fruits

In addition to increasing the consumption of tropical and subtropical fruits, the enhancement of their nutritional and health quality is an important goal in the effort to improve global health and nutrition. Erbersdobler (2003) and Boeing et al. (2004) advocated the intake of functional foods that are enriched with phytochemicals. Several crop production techniques have been reported to enhance phytochemical content in several fruits (Schreiner, 2005), and some postharvest practices and techniques can also affect the phytochemicals contents (Beuscher et al., 1999; Goldmann et al., 1999; Huyskens-Keil and Schreiner, 2004). Genetic engineering can make a substantial contribution to improved nutrition in tropical and subtropical fruits (Fernie et al., 2006). Biotechnology has been applied to improve the nutritional quality of a range of crops (Dalal et al., 2006),

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targeting protein quality and quantity, desirable fatty acids, vitamins and minerals and antioxidants. Plants, including fruits, naturally contain a large array of antioxidants, including carotenoids, vitamins C and E, and flavonoids, and efforts to increase their content have taken both breeding-based and transgenic approaches. Naturally occurring germplasm can provide a rich source of genetic variation and it is likely that new strategies for improving the nutritional value of tropical and subtropical fruits will result from screening for variation in nutritional and health composition in wild crops and the broadest possible spectrum of existing cultivars. Vast variation in the amounts of phenolic antioxidants available via diet (Shetty et al., 2003) coupled with reduced bioavailability and functionality has led to an urgent need to develop innovative strategies to enrich diets with phenolics and specifically phenolic antioxidants with consistent phytochemical profile for enhanced health functionality. Of the many strategies, two are important to enrich phenolic antioxidants. The first is genetic modification of cultivars to produce plants that will yield fruits with higher phenolic concentration. Currently, in terms of genetic improvement, breeding strategy coupled with micropropagation using tissue culture is being developed (McCue and Shetty, 2004). These strategies, along with genetic modification, could be directed toward phytochemical enrichment and quality improvement. However, this method presents important issues, such as regulation of key metabolites by multiple genes and biochemical pathways, acceptance of genetically modified foods, and the relative time and economic considerations involved (Kishida et al., 2000). Another exciting strategy that can be used is the bioprocessing of botanicals using solid-state bioprocessing and synergies to generate phytochemical profiles with enhanced health functionality. This strategy can be used for juice and pulp as well as pomace that remain after the juice is extracted from the fruit. Fermentation of fruit juices, such as grape juice to wine, has already been shown to improve nutritive and health-promoting activities (McCue and Shetty, 2003; Randhir and Shetty, 2004). Solid-state bioprocessing done on the pulps using food grade fungi can result in enrichment of the pulp with phenolic antioxidants and functionally important phenolic phytochemicals, and also improve phytochemical profile consistency. To date, the effectiveness of postharvest treatments has been assessed mainly by the quality maintenance of harvested fruit and vegetables. However, with rising consumer interest in foods that promote health, attention has shifted from quality maintenance to quality assurance with particular emphasis on the enhancement of health-promoting phytochemicals. Therefore, to obtain tropical fruit enriched with phytochemicals, postharvest treatments may be used either singularly or in combination to elicit the desired effect. To ensure an efficient and consumer- oriented supply chain, these postharvest treatments should be combined with crop management strategies. Such phytochemical-enriched fruit could be served as fresh products or used as raw material for functional foods and supplements and would act as a complementary or synergistic strategy to human nutrition programs and nutrition policy for enhancing the consumption of

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phytochemicals. However, investigation of the beneficial effects of physical and chemical postharvest treatments on health promoting phytochemicals in fruit and vegetables needs to be extended.

2.9

Conclusions

Fruit consumption definitively has health-promoting properties. Tropical and subtropical fruits are rich sources of diverse nutritional and health components, and therefore their consumption is important for health. However, there are still needs for research on the characterization of the nutritional and health components of many tropical and subtropical fruits. In addition, there is a need for controlled, clinical intervention trials in order to investigate and to confirm the effect of the consumption of tropical and subtropical fruits on the different diseases, as well as studies to reveal the mechanisms behind the effect of the different phytochemical components in these fruits.

2.10

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Stintzing FC, Schieber A and Carle R (2002), Identification of betalains from yellowbeet (Beta Vulgaris L.) and cactus pear (Opuntia ficus indica L. Mill.) by high performance liquid chromatography-electrospray ionization mass spectroscopy, J Agric Food Chem, 50, 2302–2307. Strack D, Vogt T and Schliemann W (2003), Recent advances in betalain research, Phytochemistry, 62, 247–269. Sun J, Chu Y-F, Wu X and Lui RH (2002), Antioxidant and antiproliferative activities of common fruits, J Agric Food Chem, 50, 6910–6916. Suzuki S, Takada T, Sugawara Y, Muto T and Kominami R (1991), Quercetin induces recombinational mutations in cultured cells as detected by DNA fingerprinting, Jap J Cancer Res, 82 (10), 1061–1064. Swisher HE (1984), Avocado oil, J Am Oil Chem Soc, 65, 1704–1706. Talcott ST, Moore JP, Lounds-Singleton AJ and Percival SS (2005), Ripening associated phytochemical changes in Mangos (Mangifera indica) following thermal quarantine and low-temperature storage, J Food Sci, 70(5), C337–C341. Tango JS, Dacosta ST, Antunes AJ and Figueriedo IB (1972), Composition of fruits oil of different varieties of avocados grown in Sao Paulo, Fruits, 27, 143–146. Temple NJ and Gladwin KK (2003), Fruit, vegetables, and the prevention of cancer: Research challenges, Nutrition, 19, 467–470. Terry LA and Joyce DC (2004), Elicitors of induced disease resistance in postharvest horticultural crops: a brief review, Postharv Biol and Technol, 32, 1–13. Tesoriere L, Butera D, Pintaudi AM, Allegra M and Livrea MA (2004), Supplementation with cactus pear (Opuntia ficus-indica) fruit decreases oxidative stress in healthy humans: a comparative study with vitamin C, Am J Clin Nutr, 80, 391–395. Thomas P (1975), Effect of postharvest temperatures on quality, carotenoids and ascorbic acid contents in Alphonso mangos on ripening, J Food Sci, 40, 704–706. Tian S, Xu Y, Jiang A and Gong Q (2002), Physiological and quality responses of longan fruit to high O2 or high CO2 atmospheres in storage, Postharvest Biol Technol, 24, 335–340. Tomás-Barberán FA and Espín CJ (2001), Effect of wounding on phenolic enzymes in six minimally processed lettuce cultivars upon storage J Agric Food Chem, 49(1), 322–30. Traber MG (2007), Vitamin E. In: Handbook of vitamins, Boca Raton, FL, USA, Zempleni j, Rucker EB, McCormick DB, Suttie JW. Tripathi P and Dubey NK (2004), Exploitation of natural products as an alternative strategy to control postharvest fungal rotting of fruit and vegetables, Postharvest Biol and Technol, 32(3), 235–245. Turner JG, Ellis G and Devoto A (2002), The Jasmonate Signal Pathway, The Plant Cell J, 14, S153–S164. Tussedre PL, Frankel EN, Waterhouse AL, Peleg H and German JB (1996), Inhibition of in vitro human LDL oxidation by phenolic antioxidants from grapes and wines, J Sci Food Agric, 70, 55–61. USDA, (2005), U.S. Department of Agriculture, Agricultural Research Service. 2005. USDA National Nutrient Database for Standard Reference, Release 18. Nutrient Data Laboratory Home Page, http://www.nal.usda.gov/fnic/foodcomp van den Berg H, Faulks R, Granado H F, Hirschberg J, Olmedilla B et al. (2000), The potential for the improvement of carotenoid levels in foods and the likely systemic effects, J Sci Food Agric, 80, 880–912. Vareed SK, Reddy MK, Schutzki RE and Nair MG (2006), Anthocyanins in Cornus alternifolia, Cornus controversa, Cornus kousa and Cornus florida fruits with health benefits, Life Sci, 78, 777–784. Vareed SK, Schutzki RE and Nair MG (2007), Lipid peroxidation, cyclooxygenase enzyme and tumor cell proliferation inhibitory compounds in Cornus kousa fruits, Phytomedicine, 14, 706–709.

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Varoquaux P and Mazollier J (2002), Overview of the European fresh-cut produce industry, In O. Lamikanra, (Ed.), Fresh-cut fruits and vegetables: Science, Technology, and market (p. 21). Boca Raton: CRC Press. Vásquez-Caicedo AL, Schilling S, Carle R and Neidhart S (2007), Effects of thermal processing and fruit matrix on β-carotene stability and enzyme inactivation during transformation of mangoes into purée and nectar, Food Chem, 102, 1172–1186. Vazquez-Salinas CS and Laksminariyana S (1985), Compositional Changes in mango fruit during ripening at different storage temperatures, J Food Science, 50:1646–1648. Vigneault C and Artes-Hernandez F (2007), Gas treatment for increasing the phytochemical content of fruits and vegetables, Stewart Postharvest Rev, 3:8 www.stewartpostharvest. com. Wang H, Cao G and Prior RL (1996), Total antioxidant capacity of fruits, J Agric Food Chem, 44, 701–705. Wattenberg LW and Coccia JB (1991), Inhibition of 4-(methylnitrosamino)–1-(3-pyridyl)butanone carcinogenesis in mice by d-limonene and citrus fruit oil, Carcinogenesis, 12, 115–117. West CE and Castenmiller JJM (1998), Quantification of the ‘SLAMENGHI’ factor for carotenoid bioavailability and bioconversion, Int J Vit Nutr, 68, 371–377. Whiley AW and Schaffer B (2006), Avocado: Botany, Production and Uses, CABI Publishing, CAB International, Wallingford OXON O10 8DE UK. Willett WC (2000), Diet and cancer, Oncologist, 5, 393–404. William R, Spencer J and Rice-Evans C (2004), Flavonoids: antioxidants or signaling or signally molecule?, Free Radic Biol Med, 36, 838–849. Wilson BS, Deanin GG and Oliver JM (1991), Regulation of IgE receptor-mediated secretion from RBL–2H3 mast cells by GTP binding proteins and calcium, Biochem Biophys Res Commun, 174, 1064–1069. Wolbang CM, Fitos JL and Treeby MT (2008), The effect of high pressure processing on nutritional value and quality attributes of Cucumis melo L, Inn Food Sci Emerg Technol, 9, 196–200. Wolf G (1984), Multiple functions of vitamin A, Physiol Rev, 64, 873–937. Wu X, Beecher GR, Holden JM, Haytowitz DB, Gebhardt SE and Prior RL (2004), Lipophilic and hydrophilic antioxidant capacities of common foods in the United States, J Agric Food Chem, 52, 4026–4037. Yaacob O and Tindall HD (1995), Mangosteen Cultivation, FAO Plant production and protection paper 129, FAO, Rome. Yahia EM (2010), The contribution of fruit and vegetable consumption to human health, In: Phytochemicals: Chemistry, Nutricional and Stability, Wiley-Blackwell, Chapter 1, pp. 3–51. Yahia EM (2006), Handling Tropical Fruits, In: Scientists Speaks, p. 5–9, World Foods Logistics Organization, Alexandria, VA. Yahia EM (2011a), Avocado, Chapter 8. In: Crop Postharvest: Science and Technology, Volume 3, edited by Rees D, Farrell G and Orchard JE, Wiley-Blackwell, Oxford, in press. Yahia EM (2011b), Prickly Pear, Chapter 13. In: Crop Postharvest: Science and Technology, Volume 3, edited by Rees D, Farrell G, and Orchard JE, Wiley-Blackwell, Oxford, UK, in press. Yahia EM (2008). Modified and controlled atmospheres for storage, transportation and packaging of horticultural commodities. CRC Press (Taylor & Francis). Yahia EM and Ornelas-Paz JdeJ (2010), Chemistry, stability and biological actions of carotenoids. In: Fruit and vegetable phytochemicals: Chemistry, nutritional value and stability, edited by De la Rosa LA, Alvarez-Parrilla E, Gonzalez-Aguilar GA. Wiley-Blackwell, A John Wiley & Sons, Inc., USA. Yahia EM, Ornelas-Paz JdeJ and Gardea AA (2006), Extraction, separation and partial identification of ‘Ataulfo’ mango fruit carotenoids, Acta Hortic, 712, 333–338.

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3 Postharvest biology of tropical and subtropical fruits A. A. Kader, University of California, Davis, USA and E. M. Yahia, Autonomous University of Queretaro, Mexico

Abstract: Postharvest losses in quantity and quality of tropical and subtropical fruits are commonly very high, especially as many of these fruits are produced in developing countries and transported long distance to markets in developing and developed countries. Biological factors involved in deterioration of fresh fruit quality include the rates of respiration, ethylene production and transpiration and fruit sensitivity to ethylene and also compositional changes that affect color, texture, flavor (taste and aroma) and nutritional quality. Several physiological disorders also reduce fruit quality postharvest. These are the result of products’ responses to various environmental and physical stresses, including temperature (the most significant factor), relative humidity, ethylene, atmospheric composition (concentrations of oxygen, carbon dioxide and other gases), and light. Lastly, other biological factors such as disease and insect infestation can reduce fruit quality. There are many opportunities to reduce quality deterioration associated with biological factors by selecting genotypes that have lower respiration and ethylene production rates, less sensitivity to ethylene, slower softening rate, improved flavor quality, enhanced nutritional quality (vitamins, minerals, dietary fiber, and phytonutrients including carotenoids and phenolic compounds), reduced browning potential, decreased susceptibility to chilling injury, and/or increased resistance to postharvest decay-causing pathogens. This chapter describes some of the important biological and environmental factors that influence deterioration rates, therefore causing losses of tropical and subtropical fruits. The potential uses of biotechnological approaches for improving quality and postharvest life are also briefly discussed. Key words: biotechnology, composition, deterioration, ethylene, pathological breakdown, physiological disorders, respiration, ripening, senescence.

3.1

Introduction

Subtropical fruits include avocado, carob, cherimoya, citrus fruits (which are most important in international commerce), dates, figs, jujubes, kiwifruit, loquat,

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litchi, olive, persimmon and pomegranate; some of these fruits are also grown in tropical areas. Tropical fruits include acerola, banana, breadfruit, carambola, durian, guava, jackfruit, longan, mamey sapote, mango, mangosteen, papaya, passion fruit, pineapple, prickly pear, rambutan, sapodilla, soursop and sweetsop; a few of these fruits are also grown in subtropical regions. Only four of these fruits, i.e., banana, mango, papaya and pineapple, are important in international commerce at this time, but it is possible that other tropical fruits will be added to this group in the future. Tropical and subtropical fruits are very diverse in their morphological, compositional and physiological characteristics and therefore they can be classified into groups requiring different treatment to maintain their quality and extend their postharvest shelf life. However, all these fruits are characterized by high water content and potential for water loss resulting in shriveling, susceptibility to mechanical injury and susceptibility to attacks by microorganisms (bacteria, fungi) and insect infestation. Fresh tropical and subtropical fruits are living organs subject to continuous changes after harvest, and therefore attention to detail is required throughout the handling system between the sites of production and consumption. Some of the changes that occur after harvest in these fruits are desirable, and may require specific treatments and techniques to promote them, while many other changes are undesirable and require treatments and techniques to delay and minimize their incidence and severity. Although none of the changes in fresh fruits can be stopped, many can be retarded. Ripening and senescence, the last stages in the development of fresh tropical and subtropical fruits, are characterized by some irreversible processes that lead to breakdown and death of the fruit. Understanding the biological and environmental factors affecting postharvest deterioration rate is essential to developing treatments for maintaining quality and extending postharvest life. Several books on postharvest biology and technology of horticultural perishables including fruits have been published during the past two decades (Ben-Yehoshua, 2005; Chakraverty et al., 2003; Florkowski et al., 2009; Gross et al., 2002; Kader, 2002a; Kays and Paull, 2004; Knee, 2002; Lamikanra et al., 2005; Nunes, 2008; Paliyath et al., 2008; Salunkhe and Kadam, 1995; Seymour et al., 1993; Thompson, 2003; Wills et al., 2007), but only one has focused on subtropical and tropical fruits (Mitra, 1997).

3.2

Diversity in fruit characteristics

Tropical and subtropical fruits are diverse in their morphological and compositional characteristics, in their postharvest physiology, and in their optimum postharvest requirements and recommendations. Subtropical fruit, for example, can be grouped into three subgroups, according to their relative perishability, as follows: (1) highly perishable such as fresh figs, loquat, litchi; (2) moderately perishable such as cherimoya, olive, persimmon; and (3) less perishable such as citrus fruits,

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carob (dry), dried figs, date, jujube (Chinese date), kiwifruit, pomegranate (Kader and Arpaia, 2002). Both tropical and subtropical fruits are also of diverse sizes, shapes, and botanical structures (drupes, berries, aggregate fruits). Avocados are one-seeded berries which vary in size among cultivars and are usually pearshaped, but can be round or oval in shape, while all citrus fruits are berry-like fruits classified as hesperidia, which have a separable rind. The pigmented part of the rind is called the flavedo (epidermis + several subepidermal layers), while the whitish part of the rind is called the albedo. The juicy part of the fruit consists of segments filled with juice sacs. The weight of subtropical and tropical fruit ranges from 5–7 g (acerola) to 8–20 kg (jackfruit). Many kinds of tropical fruits have large seeds, inedible skin, or tough rind, like the citrus fruits mentioned above. This contributes to a high waste index (inedible portion) relative to temperatezone fruits (2–15% waste index). For example, the waste indices for papaya, banana and pineapple are 25, 30 and 41%, respectively. Some tropical fruits, such as guava and sapote, contain sclereids with heavily lignified walls (stone cells), which influence their textural quality (Kader et al., 2002). Siriphanich (2002) concluded that many tropical fruits have peels that are physiologically distinct from the pulp and require special attention after harvest to satisfy consumers; an important requirement is to synchronize changes in the peel with those in the pulp.

3.3

Maturation and ripening

Maturity at harvest is the most important factor that determines storage life and final fruit quality. Immature fruits are more subject to shriveling and mechanical damage and are of inferior quality when ripe. Overripe fruits are likely to become soft and mealy with insipid flavor soon after harvest. Fruits picked either too early or too late in the season are more susceptible to physiological disorders and have a shorter storage life than those picked at the proper maturity. All subtropical and tropical fruits, with a few exceptions such as avocados and bananas, reach their best eating quality when allowed to ripen on the tree or plant. However, some fruits are picked mature but unripe so that they can withstand the postharvest handling system when shipped long distances. Most currently used maturity indices are based on a compromise between those indices that would ensure the best eating quality to consumers and those that provide the needed flexibility in marketing. Fruits can be divided into two groups: those that are incapable of continuing their ripening process once removed from the plant, known as non-climacteric fruits, and those that can be harvested mature and ripened off the plant, known as climacteric fruits. Citrus fruits (grapefruit, kumquat, lemon, lime, orange, mandarin and pomelo), pineapple and pomegranate are examples of those that cannot continue to ripen once picked. Example of fruits that can ripen off plant, however, include avocado, banana, cherimoya, kiwifruit, mango, papaya and

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Table 3.1 Classification of some tropical and subtropical fruits into climacteric and non-climacteric respiratory patterns (modified from Kader, 2002c) Climacteric fruit

Non-climacteric fruits

Avocado, banana, breadfruit, cherimoya, durian, feijoa, fig, guava, jackfruit, kiwifruit, mango, mangosteen, muskmelon, papaya, passion fruit, persimmon, plantain, rambutan, sapodilla, sapote, soursop, sweetsop

Carambola, cashew apple, coconut, date, grapefruit, jujube, kumquat, lemon, lime, longan, loquat, litchi, mandarin, olive, orange, pineapple, pomegranate, prickly (cactus) pear, pomelo, rose apple, star apple, tamarillo, tamarind

persimmon (see Table 3.1). Fruits of the first group produce very small quantities of ethylene and do not respond to ethylene treatment except in terms of degreening (removal of chlorophyll) in citrus fruits and pineapples. Fruits capable of offplant ripening produce much larger quantities of ethylene in association with their ripening, and exposure to ethylene treatment will result in faster and more uniform ripening (see sections 3.5.1 and 3.5.2). Maturity indices used commercially include fruit size, shape, external and/or internal color, firmness, juice content, total solids (dry matter content), and sugar/ acid ratio. Some nondestructive methods for estimating internal quality factors are available, but more research and development efforts are needed to develop portable and less expensive instruments that can be used for determining harvest time based on optimal maturity and ripeness stage.

3.4

Quality attributes

Quality is defined as ‘any of the features that make something what it is’ or ‘the degree of excellence or superiority’. Quality attributes include appearance, texture, flavor (taste and aroma), and nutritive value of fruits. Producers want their fruits to have good appearance and few visual defects, but for them a useful cultivar of a given fruit species must score high on yield, disease resistance, ease of harvest, and shipping quality. To receivers and market distributors, quality of appearance is most important; they are also keenly interested in firmness and long storage life. Consumers judge fruits as good quality if they look good, are firm, and offer good flavor and nutritive value. Although consumers buy on the basis of appearance and feel, their satisfaction and likelihood to buy that fruit again depends on their perception of good eating quality. Various quality attributes are used in commodity evaluation in relation to specifications for grades and standards, selection in breeding programs, and evaluation of responses to various environmental factors and/or postharvest treatment, including storage conditions. The relative importance of each of these quality factors depends on the commodity and its intended use (fresh or processed). Numerous defects can influence appearance quality of horticultural crops. Morphological defects include seed germination inside fruits. Physical defects include shriveling of

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all fruits; internal drying of some fruits; and mechanical damage such as punctures, cuts and deep scratches, splits and crushing, skin abrasions and scuffing, deformation (compression), and bruising. Temperature-related disorders (freezing, chilling, sunburn, sunscald) are examples of physiological defects (Kader, 2002a). Textural quality of fruits is not only important for their eating and cooking quality but also for their shipping ability. Soft fruits cannot be shipped long distances without extensive losses owing to physical injuries. This necessitates harvesting fruits at less than ideal maturity from the flavor quality standpoint in many cases. Flavor quality involves perception of the tastes and aromas of many compounds. Objective analytical determination of critical components must be coupled with subjective evaluations by a taste panel to yield useful and meaningful information about flavor quality of fresh fruits. This approach can be used to define a minimum level of acceptability. To find out consumer preferences for flavor of a given commodity, large-scale testing by a representative sample of consumers is required. Postharvest life of fruits based on flavor is generally shorter than postharvest life based on appearance and textural quality. To increase consumer satisfaction, fruits should be sold before the end of their flavor life. Fresh fruits play a very significant role in human nutrition, especially as sources of vitamins (vitamin C, vitamin A, vitamin B6, thiamin, niacin), minerals and dietary fiber. They also contain many phytochemicals (such as antioxidant phenolic compounds and carotenoids) that have been associated with reduced risk of some forms of cancer, heart disease, stroke, and other chronic diseases (Vicente et al., 2009; Yahia, 2009b; Yahia, 2010; Yahia and Ornelas-Paz, 2010). Tropical fruits have always been and are still an important source of nutrients for people in tropical areas. Bananas and breadfruits are widely used as starch sources. Acerola fruits contain the highest known ascorbic acid content among all fruits (1000– 3300 mg 100 gm−1 fresh weight). Other good sources of vitamin C include guava, litchi, papaya and passion fruit. Mango, papaya and the recently introduced yellow-flesh pineapple cultivars are good sources of vitamin A. Breadfruit and cherimoya contain relatively high amounts of niacin and thiamin. Most tropical fruits are good sources of minerals, especially potassium and iron. Citrus fruits are very good sources of vitamin C and rank as number 1 in their contribution of vitamin C to human nutrition in the US. Safety factors include levels of naturally occurring toxicants in certain crops that vary according to genotypes and are routinely monitored by plant breeders to ensure that they do not exceed their safe levels in new cultivars. Contaminants, such as chemical residues and heavy metals in fresh fruits are also monitored by various agencies to ensure compliance with established maximum residue tolerance levels. Sanitation procedures throughout the harvesting and postharvest handling operations are essential to minimizing microbial contamination. Proper preharvest and postharvest handling procedures must be enforced to reduce the potential for growth and development of mycotoxin-producing fungi. Successful postharvest handling depends on preharvest factors (Arpaia, 1994) that influence the initial quality of the crop at harvest, including the degree of maturity, and on careful handling to minimize mechanical damage, ensure proper management

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of the environmental conditions, and good sanitation. Applying adequate postharvest techniques and treatments is important to maintain quality in terms of appearance, texture, flavor and nutritive value, to maintain food safety and to reduce losses along the supply chain between harvest and consumption and to prolong postharvest life.

3.5

Biological factors affecting deterioration

The tropics possess an astonishingly vast and diverse number of species of edible fruits, but the climatic conditions also tend to hasten spoilage. Most tropical and subtropical fruits have a limited postharvest life due to their high perishability, sensitivity to low (chilling) temperatures and to several decay organisms. The following biological factors affect fresh tropical and subtropical fruits and therefore influence their postharvest life and quality. 3.5.1 Respiration Aerobic respiration is the process by which stored organic materials (carbohydrates, proteins, fats) are broken down into simple end products with the release of energy. Oxygen (O2) is used in this process, and carbon dioxide (CO2) is produced (Fig. 3.1).

Fig. 3.1

Phases of the respiratory climacteric in a ripening climacteric fruit.

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The loss of stored food reserves in the commodity during respiration hastens senescence as the reserves that provide energy to maintain the commodity’s living status are exhausted. This reduces the food value (energy value) for the consumer, causes loss of flavor quality, especially sweetness, and causes loss of salable dry weight (especially important for commodities destined for dehydration). The energy released as heat, known as vital heat, affects postharvest technology considerations such as estimations of refrigeration and ventilation requirement (Kader, 2002c). Saltveit (2002) provides a clear description of aerobic respiration: Maintaining a supply of high-energy compounds like adenosine triphosphate (ATP), nicotinamide adenine dinucleotide (NADH) and pyrophosphate (PPi) is a primary function of respiration. The overall process of aerobic respiration involves regeneration of ATP from ADP (adenosine diphosphate) and Pi (inorganic phosphate) with release of CO2 and H2O. If glucose is used as substrate, the overall equation for respiration can be written as follows:

C6H12O6 + 6O2 → 6CO2 + 6 H2O + 686 kcal mole−1 The components of this reaction have various sources and destinations. The one mole of glucose (180 g) can come from stored simple sugars like glucose and sucrose or complex polysaccharides like starch. Fats and proteins can also provide substrates for respiration, but their derivatives, i.e., fatty acids, glycerol and amino acids, enter at later stages in the overall process and as smaller, partially metabolized molecules (Fig. 3.2). The 192 g of O2 (6 moles × 32 g mol−1) used to oxidize the

Fig. 3.2 A schematic of compositional changes associated with fruit ripening.

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Postharvest biology and technology of tropical and subtropical fruits 1 mole of glucose diffuses into the tissue from the surrounding atmosphere, while the 6 moles of CO2 (264 g) diffuses out of the tissue. The 6 moles of H2O (108 g) that are produced are simply incorporated into the aqueous solution of the cell. Aerobic respiration involves a series of three complex reactions, each of which is catalyzed by a number of specific enzymes which either: (1) add an energy containing phosphate group to the substrate molecule; (2) rearrange the molecule; or (3) breakdown the molecule to a simpler one. The three interconnected metabolic pathways are glycolysis, the tricarboxylic acid (TCA) cycle, and the electron transport system. 1. Glycolysis, i.e., the breakdown or lyse of glucose, occurs in the cytoplasm of the cell. It involves the production of two molecules of pyruvate from each molecule of glucose. Each of the ten distinct, sequential reactions in glycolysis is catalyzed by one enzyme. Two key enzymes in glycolysis are phosphofructokinase (PFK) and pyruvate kinase (PK). Cells can control their rate of energy production by altering the rate of glycolysis, primarily through controlling PFK and PK activity. One of the products of respiration, ATP, is used as a negative feed-back inhibitor to control the activity of PFK. Glycolysis produces two molecules of ATP and two molecules of NADH from the breakdown of each molecule of glucose. 2. Tricarboxylic acid (TCA) cycle, which occurs in the mitochondrial matrix, involves the breakdown of pyruvate into CO2 in nine sequential, enzymatic reactions. Pyruvate is decarboxylated (loses CO2) to form acetate that condenses with a co-enzyme to form acetyl CoA. This compound then enters the cycle by condensation with oxaloacetate to form citric acid. Citric acid has three carboxy groups from which the cycle derives its name. Through a series of seven successive rearrangements, oxidations and decarboxylations, citric acid is converted back into oxaloacetate that is then ready to accept another acetyl CoA molecule. Besides producing the many small molecules that are used in the synthetic reactions of the cell, the TCA cycle also produces one molecule of flavin adenine dinucleotide (FADH2) and four molecules of NADH for each molecule of pyruvate metabolized. 3. Electron transport system, which occurs on membranes in the mitochondria, involves the production of ATP from the high energy intermediates FADH2 and NADH. The energy contained in a molecule of NADH or FADH2 is more than is needed for most cellular processes. In a series of reactions, one NADH molecule produces three ATP molecules, while one FADH molecule produces two ATP molecules. The production of ATP is not only dependent on the energy contained in NADH and FADH2, but also on the chemical environment (i.e., pH and ion concentrations) within the cell and mitochondria (Saltveit, 2002).

Fermentation, or anaerobic respiration, occurs when the O2 concentration in the fruit falls below a certain level and can reduce fruit quality. Saltveit (2002) describes the process as follows: fermentation, or anaerobic respiration involves the conversion of hexose sugars into alcohol and CO2 in the absence of O2. Pyruvate produced through glycolysis via a series of reactions that do not require O2 can be converted to lactic acid, malic acid, acetyl-CoA, or acetaldehyde. The pathway chosen depends on cellular pH, prior stresses, and the current metabolic needs of the cell. Acidification of the cytoplasm

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enhances the activity of pyruvic decarboxylase that then shunts pyruvate to form CO2 and acetaldehyde. The acetaldehyde is converted by the enzyme alcohol dehydrogenase to ethanol with the regeneration of NAD+. Two molecules of ATP and 21 kcal of heat energy are produced in anaerobic respiration (alcoholic fermentation) from each molecule of glucose.

For more details about the biochemistry of respiratory metabolism, see the book by Kays and Paull (2004), among several others. As mentioned in section 3.3, tropical and subtropical fruits are commonly classified according to their respiration patterns into ‘climacteric’ and ‘nonclimacteric’ fruits (Table 3.1). Climacteric fruits are those that show a sudden increase in aerobic respiration, coincident with their maturation and ripening, while non-climacteric fruits do not show such a pattern in their respiration and ethylene production rates. Deterioration rates are inversely related to aerobic respiration rates of subtropical and tropical fruits (Table 3.2). Both respiration and deterioration rates are accelerated by an increase in temperature, decrease in relative humidity, exposure to ethylene, wounding and other mechanical injuries and exposure to other abiotic and biotic stresses. The oxygen concentration at which a shift from predominantly aerobic to predominantly anaerobic respiration occurs is known as the extinction point, the anaerobic compensation point, or the fermentative threshold (Saltveit, 2002). The shift from aerobic to anaerobic respiration depends on fruit maturity and ripeness stage (gas diffusion characteristics), temperature, and duration of exposure to stress-inducing concentrations of O2 and/or CO2 (Kader, 1986a). Since the oxygen concentration at any point in a fruit varies due to rates of gas diffusion and respiration, some parts of the commodity may also become anaerobic while others remain aerobic (Saltveit, 2002). Elevated carbon dioxide concentrations are highly effective in altering primary and secondary metabolism of harvested fruits and may have a marked impact on many biochemical processes, thus affecting quality parameters. The response to Table 3.2 Classification of some tropical and subtropical fruits according to their rate of respiration (modified from Kader, 2002c) Class

Respiration rate (mg CO2 kg−1 hr−1 at 20°C)

Fruit

Very low Low

< 35 35–70

Moderate

70–150

High Very high

150–300 >300

Dates, dried tropical and subtropical fruits Avocado (mature), banana (mature-green), carambola, citrus fruits, jackfruit, kiwifruit, litchi, longan, mangosteen, papaya, pineapple, pomegranate Durian, fig, guava, lanzone, mango, olive, rambutan Avocado (ripe), banana (ripe) Cherimoya, passion fruit, sapote, soursop

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high carbon dioxide concentrations may be beneficial or detrimental depending upon the nature of the product, the concentration of carbon dioxide outside and inside the tissue, the duration of exposure and the concentration of oxygen (Kader, 1986a). Since carbon dioxide is toxic, many tissues undergo damage following exposure to high carbon dioxide concentrations, and high variability is present among and within species in terms of susceptibility to carbon dioxide injury, resulting in internal and external physiological disorders and the appearance of offflavors often related to the products of fermentation (Kanellis et al., 2009). Severe atmospheric stress (very low O2 and/or very high CO2 atmospheres) conditions decrease cytoplasmic pH and ATP levels, and reduce pyruvate dehydrogenase activity. Alcohol dehydrogenase, lactate dehydrogenase, cytosolic glyceraldehyde dehydrogenase, aldolase, glucose phosphate isomerase, pyruvate decarboxylase, sucrose synthase, and alanine aminotransferase are induced or activated by anaerobiosis (Kanellis et al., 2009), causing accumulation of acetaldehyde, ethanol, ethyl acetate, and/or lacate, which may be detrimental to the commodities if they are exposed to atmospheric stress conditions beyond their tolerance limits (Kanellis et al., 2009). Gene expression is strongly altered by anoxia, and protein synthesis is redirected to the production of a new set of anaerobic polypeptides (ANP); several ANPs have been identified, and have been shown to be enzymes engaged with the glycolytic and fermentative pathway (Kanellis et al., 2009). Limits of tolerance to low O2 concentration and elevated CO2 concentrations may vary depending on storage temperature and duration of exposure. The duration for which a commodity is tolerant to low O2 levels becomes shorter as storage temperature rises, because a tissue’s O2 requirements for aerobic respiration increase with higher temperatures (Kader, 1986a; Beaudry, 2000). Depending on the commodity, damage associated with CO2 may increase or decrease with an increase in temperature. A rise in temperature may cause an increase or decrease of CO2 in the tissue and, furthermore, the physiological effect of CO2 can be temperature dependent. Tolerance limits to elevated CO2 decrease with a reduction in O2 level, and similarly the tolerance limits to reduced O2 increase with the increase in CO2 level. Up to a point, fruits are able to recover from the detrimental effects of low O2 and/or high CO2 stresses (fermentative metabolism) and resume normal respiratory metabolism. Plant tissues have the capacity for recovery from the stresses caused by brief exposures to fungistatic atmospheres (>10 kPa CO2) or insecticidal atmospheres (40 to 80 kPa CO2). Postclimacteric fruits are less tolerant to atmospheric stress and have a lower capacity for recovery following exposure to reduced O2 and/or elevated CO2 levels than preclimacteric fruits. The speed and extent of recovery depend upon duration and levels of stresses, and underlying, metabolically driven cellular repair (Kader, 1986a). 3.5.2 Ethylene production and response Ethylene, the simplest of the organic compounds affecting the physiological processes of plants, is a natural product of plant metabolism and is produced by all tissues of higher plants and by some microorganisms. As a plant hormone,

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ethylene regulates many aspects of growth, development and senescence and is physiologically active in trace amounts (less than 0.1 ppm) (Abeles et al., 1992). Ethylene induces fruit abscission, softening and some physiological disorders (Abeles et al., 1992). Ethylene may increase decay development of some fruits by accelerating their senescence and softening, and by inhibiting the formation of antifungal compounds in the host tissue (Kader, 1985). The detrimental effects of ethylene on quality center on altering or accelerating the natural processes of development, ripening and senescence, while the beneficial effects of ethylene on quality center on roughly the same attributes as the detrimental effects, but differ in both degree and direction (Saltveit, 1999). Low temperatures, controlled or modified atmospheres (CA or MA), and ethylene avoidance and/or scrubbing techniques are used to reduce ethylene damage. Several factors affect ethylene production rates, including species (Table 3.3), cultivar, maturity and ripening (generally increases due to maturity and ripening, especially in climacteric fruits), temperatures (increases at temperatures of up to 30°C), physical/mechanical injury, different types of stress such as water stress and microbial attack. Other factors governing plant responses to ethylene exposure include ethylene concentration (linear response with logarithmic increases in ethylene concentration), atmospheric composition (more than 10% oxygen and less than 1% carbon dioxide), and duration of exposure (Saltveit, 1999). Generally, ethylene production rates increase with maturity at harvest, physical injures, disease incidence, increased temperatures up to 30°C, and water stress. On the other hand, ethylene production rates by fresh fruits are reduced by storage at low temperature, and by reduced O2 (less than 8%) and/or elevated CO2 (above 1%) levels around the commodity (Kader, 2002c). Elevated-CO2 atmospheres inhibit activity of ACC synthase (key regulatory site of ethylene biosynthesis), while ACC oxidase activity is stimulated at low CO2 and inhibited at high CO2 concentrations and/or low O2 levels. Ethylene action is inhibited by elevated-CO2 atmospheres. These interactions among ethylene, O2, and CO2 provide the Table 3.3 Classification of some tropical and subtropical fruits according to their ethylene production rate (modified from Kader, 2002c) Class

Ethylene production rate (μL C2H4 kg−1 hr−1) at 20°C

Fruits

Very low Low

Less than 0.1 ppm 0.1–1.0

Moderate

1.0–10.0

High

10.0–100.0

Very high

> 100.0

Citrus fruits, jujube, pomegranate Carambola, olive, persimmon, pineapple, tamarillo Banana, breadfruit, durian, fig, guava, litchi, mango, mangosteen, plantain, rambutan Avocado (ripe), feijoa, kiwifruit (ripe), papaya Cherimoya, mamey apple, passion fruit, sapote, soursop

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Fig. 3.3 An overview of factors affecting ethylene biosynthesis and action.

biological basis of modified (MA) and controlled atmospheres (CA) effects on delaying ripening and senescence of fruits (Yahia, 2009a). Ethylene is synthesized from the amino acid methionine which is converted to S-adenosylmethionine (AdoMet = SAM) by the enzyme S-AdoMet synthase (ADS) (Fig. 3.3). AdoMet is converted by the enzyme 1-aminocyclopropane-1-carboxylate synthase (ACC synthase = ACS) to 5-methylthioadenosine (MTA), which is converted back to methionine via the Yang-cycle and to 1-aminocyclopropane-1carboxylic acid (ACC), the precursor of ethylene in the presence of O2. ACC is finally oxidized by ACC oxidase (ACO) to form ethylene, cyanide and carbon dioxide. The conversion of AdoMet to ACC by ACS is the first committed and generally considered as the rate-limiting step in ethylene biosynthesis (Yang and Hoffman, 1984; Kende, 1993; Kays and Paull, 2004; Broekaert et al., 2006). Saltveit et al. (1998) reviewed the history of the discovery of ethylene as a plant growth substance and concluded that ‘while great advances had been made with the traditional techniques of physiology and biochemistry, further elucidation of ethylene biosynthesis and action hinged on using the modern techniques of molecular biology and genetic engineering’. Breakthroughs in understanding ethylene signal transduction came from pursuing a genetic approach in Arabidopsis thaliana (Bleeker, 1999). A family of ETR1-like receptors interact with CTR1 to express ethylene response pathways while ethylene binding inhibits this activity. Ethylene signaling exists in climacteric and non-climacteric fruits. Molecular and genetic analysis of fruit development, and especially ripening of fleshy fruits, has resulted in significant gains in knowledge over recent years

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about ethylene biosynthesis and response, cell wall metabolism, and environmental factors that impact ripening (Seymour et al., 1993; Giovannoni, 2001). The isolation of fruit ripening-related genes has resulted not only in tools for studying the direct effects of specific gene products on ripening but also in opportunities to isolate and study gene regulatory elements that may illuminate regulatory mechanisms (Giovannoni, 2001; Klee and Clark, 2002). Biotechnology is a tool that can be utilized, in an interdisciplinary approach, to address some of the concerns about quality attributes and the biological causes of deterioration of harvested produce (King and O’Donoghue, 1995; Baldwin, 2002; Klee and Clark, 2002; Pech et al., 2005). 3.5.3 Compositional changes Tropical and subtropical fruits contain all classes of pigments (chlorophylls, carotenoids, flavonoids, betalaines), and these are important in diverse processes that contribute to color, flavor, resistance to microbial and pests attack, human nutrition and health, among others (Yahia and Ornelas, 2010). Many changes in pigments take place during development and maturation of the fruit on the plant. Some may continue after harvest and can be desirable or undesirable. Loss of chlorophyll (green color) is desirable in fruits. Development of carotenoids (yellow and orange colors) is desirable in fruits such as citrus and papaya. The desired red color development in blood oranges is due to anthocyanins and in pink grapefruit it is due to a specific carotenoid (lycopene). Beta-carotene is provitamin A and is important in nutritional quality. Development of anthocyanins (red and blue colors) is desirable in fruits such as pomegranates, litchi, and rambutan; these water-soluble pigments are much less stable than carotenoids. Changes in anthocyanins and other phenolic compounds, however, are undesirable because they may result in tissue browning (Kader, 2002c). Changes in carbohydrates include starch-to-sugar conversion (desirable in banana, kiwifruit, mango, and other fruits), sugar-to-starch conversion and conversion of starch and sugars to CO2 and water through respiration. Breakdown of pectins and other polysaccharides results in softening of fruits and a consequent increase in susceptibility to mechanical injures. Changes in organic acids, proteins, amino acids, and lipids can influence flavor quality of the fruit. Loss in vitamin content, especially ascorbic acid (vitamin C), is detrimental to nutritional quality. Production of flavor volatiles associated with ripening of fruits is very important to their eating quality. Postharvest losses in nutritional quality, particularly vitamin C content, can be substantial and are enhanced by physical damage, extended storage, higher temperature, low relative humidity, and chilling injury of chillingsensitive commodities (Kader, 2002c). 3.5.4 Growth and development Some growth and developmental changes may continue to take place after harvest, such as periderm formation associated with wound healing (a desirable change)

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and seed germination inside fruits such as tomatoes, peppers and lemons (an undesirable change). 3.5.5 Transpiration and water loss All fresh horticultural commodities, including tropical and subtropical fruits, are characterized by high water content (up to 90–95% in some fruits), which is readily lost. Water loss is a main cause of deterioration because it results not only in direct quantitative losses (loss of salable weight) but also in losses in appearance (wilting and shriveling), textural quality (softening, flaccidity, limpness, loss of crispness and juiciness), and nutritional quality. The dermal system (outer protective coverings) governs the regulation of water loss by the commodity. It includes the cuticle, epidermal cells, stomata, lenticels, and trichomes (hairs). The cuticle is composed of surface waxes, cutin embedded in wax, and a layer of mixtures of cutin, wax, and carbohydrate polymers. The thickness, structure and chemical composition of the cuticle vary greatly among commodities and among developmental stages of a given commodity (Kader, 2002c). The rate of transpiration (evaporation of water from the plant tissues) is influenced by internal or commodity factors (morphological and anatomical characteristics, surface-to-volume ratio, surface injuries, and maturity stage) and external or environmental factors (temperature, relative humidity, air movement, and atmospheric pressure). High temperatures, low RH and high air velocity promote high water loss, for example. Transpiration is a physical process that can be controlled by applying treatments to the commodity (e.g., waxes and other surface coatings and wrapping with plastic films) or by manipulating the environment (e.g., refrigeration, maintenance of high relative humidity and control of air circulation) (Kader, 2002c).

3.6

Environmental factors affecting deterioration

Several external environmental and physical factors affect the rate of deterioration and postharvest life of tropical and subtropical fruits via their effects on the internal, biological factors listed in the previous section. Stresses related to environmental factors such as excessive heat, cold, or improper mixtures of environmental gases, such as oxygen, carbon dioxide, and ethylene, can also cause certain physiological disorders, which negatively affect fruit quality and reduce its postharvest life. Several of these disorders can be initiated before harvest and expressed either before or after harvest. Some disorders may also be caused by mechanical damage. All of these disorders are abiotic in origin (i.e. not caused by disease organisms); however, abiotic disorders often weaken the natural defenses of fresh produce, making it more susceptible to biotic diseases that are caused by disease organisms. Furthermore, in many cases injuries caused by chilling, bruising, sunburn, senescence, poor nutrition and other factors can mimic

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biotic diseases. The effects of external factors are cumulative during the time between harvest and consumption. The different environmental and physical factors affecting fruit quality and the physiological disorders they cause are described below. 3.6.1 Temperature Temperature is the single most important environmental factor that affects tropical and subtropical fruit deterioration (Fig. 3.4). Low temperatures (above those that cause chilling injury) decrease metabolic activity, reduce the incidence of postharvest disease and slow its development, reduce insect activity and lessen water loss, while high temperatures (up to a certain limit) accelerate all these deterioration factors. For each increase of 10°C above optimum, the rate of deterioration increases twofold to fourfold. Temperature also influences the effects of ethylene and MA/CA storage. Spore germination and growth rate of pathogens are greatly influenced by temperature; for instance, cooling commodities below 5°C immediately after harvest can greatly reduce the incidence of Rhizopus rot (Kader, 2002c; Sommer et al., 2002). The best environmental conditions for ripening are 20–24°C, and 90–95% relative humidity. Temperatures above 27°C accelerate softening and may cause tissue discoloration, excessive decay, and

Fig. 3.4

Effect of temperature on postharvest quality of fruits.

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off-flavors.Temperatures above 35°C inhibit ethylene production and action and, consequently, inhibit ripening. The ripening rate can be manipulated by temperature management between 14 and 24°C. Exposure to undesirable temperatures results in many physiological disorders, which are reviewed in the following sections. Chilling injury Chilling injury (CI) occurs in most fruits of tropical and subtropical origin if held at temperatures above their freezing point and below 5° to 15°C, depending on the commodity (Table 3.4). This physiological disorder is the most important obstacle to the expansion of trade in tropical fruits in the world market (Siriphanich, 2002) and is the major cause of their typically short postharvest life (7–40 days). CI symptoms become more noticeable upon transfer to higher (non-chilling) temperatures. The most common symptoms are surface and internal discoloration (browning), pitting, water soaked areas, uneven ripening or failure to ripen, offflavor development, and accelerated incidence of surface molds and decay (especially organisms not usually found growing on healthy tissue) (Table 3.5). Ripening is also impaired as a result of exposure to temperatures that cause CI. The ideal control of CI is avoidance of exposure at chilling temperature. Approaches to lessen chilling injury incidence and severity include temperature conditioning, intermittent warming, CA storage, chemical treatments, and growth regulator application (Wang, 1994). These techniques reduce CI by either increasing the tolerance of commodities to chilling temperature or retarding the development of CI symptoms. Subtropical fruits vary in their relative susceptibility to chilling injury among species and cultivars within a species. For example, grapefruit, lemon, lime and pomelo are much more susceptible to chilling injury than orange, kumquat and mandarin. Dates, figs, kiwifruits and ‘Hachiya’ persimmons are not sensitive to chilling injury. ‘Fuyu’ persimmons and other subtropical fruits are chillingsensitive. Some tropical fruit are highly sensitive such as banana, breadfruit, jackfruit, mamey, mango, mangosteen, papaya, pineapple, rambutan and soursop, and others are moderately sensitive such as carambola, durian, guava, sugar apples and tamarillo (see Table 3.4). Table 3.4

Some chilling sensitive and non-sensitive tropical and subtropical fruits

Chilling sensitive fruits

Non-chilling sensitive fruits

Avocado, banana, breadfruit, carambola, cherimoya, citrus fruits, durian, feijoa, guava, jackfruit, jujube, lanzone, longan, litchi, mango, mangosteen, olive, papaya, passion fruit, pepino, pineapple, plantain, persimmon (Fuyu), pomegranate, prickly (cactus) pear, rambutan, sapodilla, sapote, tamarillo

Date, fig, kiwifruit, loquat, persimmon (Hachiya)

Source: Modified from Kader, 2002c

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Postharvest biology of tropical and subtropical fruits Table 3.5 Fruit

Chilling injury symptoms of selected subtropical and tropical fruits Minimum1 safe temperature°C

Avocado

5–10

Banana

13–15

Grapefruit Lemon Lime Mango

10–13 10–13 10–13 10–12

Olive Orange Papaya

5–8 3–5 10–12

Pineapple

95

8–10

Symptoms Grayish brown discoloration of flesh, softening, pitting, development of off-flavors Surface discoloration, dull color, failure to ripen, browning of flesh Pitting, scald, watery breakdown Pitting, membranous stain, red blotch Pitting, skin browning, accelerated decay Grayish scald-like discoloration of skin, uneven ripening, poor flavor, increased decay Internal browning, pitting Pitting, brown stain Pitting, failure to ripen, off-flavor development, accelerated decay (especially Alternaria Spp.) Uneven ripening, dull color, water-soaked flesh, off-flavor, increased acidity, loss in ascorbic acid content, wilting of crown leaves, endogenous brown spot

Note: 1 Varies with cultivar, maturity stage, and duration of exposure

Freezing injury Just like all other horticulture commodities, fresh tropical and subtropical fruits are injured at temperatures below their freezing point (about – 2°C) (Fig. 3.4). The tissues of frozen fruit break down immediately upon thawing. Freezing is usually the result of inadequate refrigerator design or poor setting or failure of thermostats. In winter conditions, freezing can occur if produce is allowed to remain for even short periods of time on unprotected transportation docks. Heat injury High temperatures, either before or after harvest, can result in injuries to several tropical and subtropical fruits. This injury can be induced by exposure to direct sunlight or excessive high temperatures, such as during the use of heat (hot air or hot water) treatments. Preharvest exposure to the sun can result in sunburn (such as in figs) and sunscald (such as in pomegranates). Transpiration in growing plants maintains temperatures in the optimal range, but once removed from the plant, fruits lack the protective effects of transpiration, and direct sources of heat such as full sunlight can rapidly heat tissues to above the thermal death point of their cells. Heat injury is usually expressed as bleaching, scalding, uneven ripening, excessive softening, and desiccation. Tropical and subtropical fruits vary significantly in their tolerance to heat injury (Paull, 1994). Temperatures above 25°C cause uneven softening, skin discoloration, flesh darkening, and off-flavors development in some

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fruits, such as avocados. Impaired ripening of other fruits occurs at temperatures above 35°C (reduced ethylene production and action). Heat treatments (hot water or hot air) have been commercially applied to some tolerant fruits such as mango, papaya and citrus, especially for the control of decay and insects (Lurie, 1998). 3.6.2 Relative humidity (RH) As discussed in section 3.5.5, water loss from fruits is affected by both commodity factors (e.g. morphological and anatomical characteristics) and external or environmental factors. Focussing on the environmental factors, the rate of water loss depends on the vapor pressure deficit (VPD) between the fruit and the surrounding ambient air, which is influenced by temperature and relative humidity (RH). At a given temperature and rate of air movement, the rate of water loss from the fruit depends on the RH. At a given relative humidity, water loss increases with the increase in temperature (Kader, 2002c). The optimum RH during storage ranges from 85 to 95% for subtropical and tropical fruits. Lower RH (55 to 65%) is recommended for tree nuts and dried fruits. Very high RH (above 95%) and water condensation on the fruits can accelerate pathogen attack and decay development. 3.6.3 Ethylene As discussed in section 3.5.2, ethylene plays a vital role in the postharvest life of many horticultural crops. This section describes how the quantity of ethylene in the environment surrounding a commodity can be adjusted to achieve the desired effect. The effect of the exposure of fruits to ethylene can be either desirable (such as in the case of the acceleration of uniform ripening and color development) or undesirable (acceleration of ripening, undesirable breakdown of colors, several physiological disorders), and depend on the type of product, physiological age, ethylene concentration, and temperature (Kader, 1985; Saltveit, 1999). The stage of maturity at harvest influences ripening rate and storage life. Picking bananas and mangos at the mature-green stage hastens their ripening by lowering their response threshold to endogenous ethylene concentration. Bananas take 1–2 weeks vs. 6–7 weeks to ripen off vs. on the plant, respectively. Avocados do not ripen on the tree. Factors which prevent avocado ripening on the tree continue to exert their effects for about 24 hours after harvest. Ripening of avocados can be hastened by exposure to 10 ppm C2H4 at 15–17°C for two days. CO2 produced by ripening avocados must be removed to prevent its accumulation to a level that negates C2H4 effects. Cold nights followed by warm days are necessary for green color (chlorophyll) loss and yellow or orange color (carotenoids) development in citrus fruits. This is the reason citrus fruits remain green after attaining full maturity and good eating quality in tropical areas. Some regreening of Valencia oranges may occur after the fruit has reached full orange color (Kader and Arpaia, 2002). The optimum temperature range for ripening is 15° to 25°C (Fig. 3.4); the higher the temperature the faster the ripening. The optimum relative humidity range is 90–95%. Ethylene can be added to the atmosphere surrounding certain

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fruits to promote their ripening. Ethylene at 100 ppm is more than adequate and can be supplied in a continuous flow system using a compressed cylinder of ethylene diluted with an inert gas such as nitrogen. An alternative is to use ethylene generators where ethylene is produced by heating ethanol plus a catalyst. To ensure uniform distribution of ethylene within the room, the air containing ethylene can be forced through the pallets containing the commodity. Carbon dioxide accumulation should be avoided (via introduction of fresh air) or corrected (by use of CO2 absorbers such as hydrated lime or a molecular sieve) if needed. The presence of ethylene, however, may also promote undesired accelerated softening and ripening of fruits during transport and storage, resulting in shorter postharvest life and faster deterioration. For example, the presence of ethylene in cold storage facilities of kiwifruits and avocados kept in air or in a CA can significantly hasten softening and reduce storage life of these fruits. The incidence and severity of ethylene damage depend on its concentration, duration of exposure, and storage temperature. Ethylene may be excluded from storage rooms and transport vehicles by using electric fork-lifts and by avoiding mixing ethyleneproducing commodities with those sensitive to ethylene. Ethylene may be removed from storage rooms and transport vehicles by using adequate air exchange (ventilation) (e.g. one air change per hour provided that outside air is not polluted with ethylene) and by using ethylene absorbers such as potassium permanganate. The air within the room or transit vehicle must be circulated past the absorber for effective ethylene removal. It is also very important to replace the used absorbing material with a fresh supply as needed. Catalytic combustion of ethylene on a catalyst at high temperatures (greater than 200°C) and use of ultraviolet radiation can also be used to remove ethylene (Reid, 2002). Ethylene damage can also be greatly reduced by holding the commodity at its lowest safe temperature and by keeping it under MA or CA (reduced oxygen and/or elevated carbon dioxide: 2–5 kPa O2 and/or 5–10 kPa CO2 is recommended) or in hypobaric storage. Under such conditions, both ethylene production by the commodity and ethylene action on the commodity are significantly reduced. Gamma irradiation has been shown to delay ripening by reducing ethylene production and its effects in several tropical fruits, but its potential detrimental effects on the fruits (at doses above those needed for insect control) exceed the benefits (Kader, 1986b). The discovery of the ethylene action inhibitor, 1-methylcyclopropene (1-MCP), in the early 1990s was a major breakthrough. In July 2002, 1-MCP (under the trade name ‘SmartFresh’), at concentrations up to 1ppm was approved by the US Environmental Protection Agency for use on apples, apricots, avocados, kiwifruit, mangoes, nectarines, papayas, peaches, pears, persimmons, plums and tomatoes. The first commercial application has been on apples to retard their softening and scald development and extend their postharvest life. As more research is completed, the use of 1-MCP will no doubt be extended to several other commodities in the future (Blankenship and Dole, 2003; Watkins, 2006; Sozzi and Beaudry, 2007; Watkins, 2008). Also, 1-MCP has been used and continues to be used to differentiate between ethylene-dependent and ethylene-independent processes in plant tissues (Defilippi et al., 2005; Pech et al., 2005; Huber, 2008).

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3.6.4 Atmospheric gases As already described in section 3.5.1, reduction of oxygen and elevation of carbon dioxide, whether intentional through MA or CA, or unintentional (restricted ventilation within a shipping container, a transport vehicle, or both), can either delay or accelerate deterioration of fresh fruits (Yahia, 2009a). Very low oxygen (less than 1%) and high carbon dioxide (greater than 20%) atmospheres can cause physiological breakdown (fermentative metabolism) in most fresh horticultural commodities (Figs. 3.5 and 3.6). The interactions between O2, CO2, and ethylene concentrations, temperature and duration of storage influence the incidence and

Fig. 3.5

Fig. 3.6

Effect of O2 level on respiration rate.

Effect of CO2 level on respiration rate.

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severity of physiological disorders related to atmospheric composition (Kader, 1986a; Singh et al., 2009; Yahia and Singh, 2009). The magnitude of these effects also depend on the species, cultivar and physiological age (Kader, 1986a; Yahia, 1998; Yahia, 2009a). During the past 50 years, the use of CAs and MAs to supplement temperature management has increased steadily and has helped to extend the postharvest life and maintain the quality of several subtropical (Singh et al., 2009) and tropical (Yahia and Singh, 2009; Yahia, 1998) fruits. However, the overall extent of commercial use of CA and MA on subtropical and tropical fruits is still limited (Kader, 2003b; Yahia, 2009a). Applications of these technologies are expected to increase as international market demand for year-round availability of various commodities grows and as technological advances are made in attaining and maintaining CA and MA during transport, storage and marketing. The use on nuts and dried fruits (for insect control and quality maintenance including prevention of rancidity) is increasing and will likely continue to increase because it is an excellent alternative to chemical fumigants (such as methyl bromide) used for insect control. Several refinements in CA storage have been made in recent years to improve quality maintenance; these include low O2 (1.0–1.5%) storage, low ethylene CA storage, rapid CA (rapid establishment of the optimum levels of O2 and CO2), and programmed (or sequential) CA storage (e.g., storage in 1 kPa O2 for two to six weeks followed by storage in 2–3 kPa O2 for the remainder of the storage period). Other developments, which may expand use of MA during transport and distribution, include using edible coatings or polymeric films to create a desired MA within the commodity (Yahia, 2009a). The use of polymeric films for packaging produce and their application in modified atmosphere packaging (MAP) systems at the pallet, shipping container (plastic liner), and consumer package levels continues to increase (Yahia, 2009a). MAP (usually to maintain 2–4 kPa O2 and 8–12 kPa CO2) is widely used in extending the shelf life of fresh-cut fruit products. Use of absorbers of ethylene, carbon dioxide, oxygen, and/or water vapor as part of MAP is increasing. Although much research has been done on the use of surface coatings to modify the internal atmosphere within the commodity, commercial applications are still very limited due to the inherent biological variability of the commodity. Potential benefits of MA and CA for subtropical and tropical fruits are species specific (Singh et al., 2009; Yahia and Singh, 2009). The extension of storage life in avocado, litchi, guava, kiwifruit, loquat, longan, persimmon, pomegranate and rambutan has been achieved through CA/MA application (Kader, 2003b; Singh et al., 2009). Most research conducted on MA/CA of tropical crops has been on banana, mango and papaya, some research on cherimoya, durian and pineapple, and little research on feijoa, lanzone, mangosteen, passion fruit, sapodilla, sugar apples and wax apples (Yahia, 1998; Yahia and Singh, 2009). Adequate handling systems, including temperature management, humidity control, avoidance of mechanical damage, sanitation, and ethylene removal treatment (for some crops), is essential for the successful application of MA/CA (Yahia and Singh, 2009).

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3.6.5 Light The effects of light conditions in storage facilities on tropical and subtropical fruit quality should also be considered. Radiant heat from high-intensity light sources can raise commodity temperatures. Exposure of some commodities to light might result in some changes, especially in the development of pigments. 3.6.6 Nutrition Certain types of physiological disorders originate from preharvest nutritional imbalances. For example, soft nose of mangoes results from calcium deficiency. Increasing calcium content via preharvest or postharvest treatments can reduce the susceptibility to physiological disorders. The calcium content also influences the textural quality and senescence rate of fruits and vegetables: increased calcium content has been associated with improved firmness retention, reduced CO2 and ethylene production rates, and decreased decay incidence. 3.6.7 Mechanical damage Fresh tropical and subtropical fruits are very prone to mechanical damage throughout the postharvest chain, e.g. during harvest, packing, packaging, transport, marketing, and even at home. These injuries are very common, are major contributors to deterioration and can cause major qualitative and quantitative losses. Types of physical damage include surface injuries, impact bruising, vibration bruising and cuts. Browning of damaged tissues results from membrane disruption, which exposes phenolic compounds to the polyphenol oxidase enzyme. Mechanical injuries not only are unsightly but also accelerate water loss, provide sites for fungal infection, and stimulate CO2 and ethylene production by the commodity (Kader, 2002c).

3.7

Pathological disorders and insect infestation

Other biological factors such as disease and insect infestation can reduce fruit quality. These are summarised below. Futher information on the control of postharvest decay caused by fungi can be found in Chapter 6. The control of quarantine pests is reviewed in detail in Chapter 7. 3.7.1 Pathological disorders Some of the most common and obvious symptoms of deterioration result from the activity of bacteria and fungi (Snowden, 1990; Sommer et al., 2002) and diseases are, in fact, the major cause of postharvest losses in tropical and subtropical fruits. Fungi are more common than bacteria in fruits. Viruses seldom cause postharvest diseases, although they, like postharvest disorders, may weaken the produce. Disease can be initiated either before or after harvest, but attack by most organisms follows physical injury or physiological breakdown of the commodity. In a few

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cases, pathogens can infect apparently healthy tissues and become the primary cause of deterioration. In general, fruits exhibit considerable resistance to potential pathogens during most of their postharvest life. The onset of ripening in fruits, and senescence in all commodities, renders them susceptible to infection by pathogens (Sommer et al., 2002). This is due to several factors including the fact that maturing and ripening fruit is usually softer, contains more sugar, and has less acidity and phenolic compounds. Many factors preharvest and postharvest affect the severity of pathogen attack and the development of decay, such as temperature, relative humidity, free water and ethylene (Sommer et al., 2002; Broekaert et al., 2006). Stresses such as mechanical injuries, chilling, and sunscald lower the resistance to pathogens (Kader, 2002c). The most important decay-causing organisms are Colletotrichum gloeosprioides (causing anthracnosis), Diplodia natalensis (causing stem end rot), Ceratocystis paradoxa (causing black rot in banana and pineapple), and Penicillium and Fusarium (causing brown rot on pineapple). The disease anthracnosis is particularly noteworthy as it is the major postharvest problem in several tropical fruits, and latent infection occurs in green fruit before harvest. Preharvest treatments and methods of disease control include the use of healthy seedlings, as well as proper field sanitation practices (Korsten, 2006). Pesticides are still used to control decay before and after harvest, but postharvest heat treatments are effective and safer for consumers. The control of biotic postharvest diseases depends on understanding the nature of disease organisms, the conditions that promote their occurrence, and the factors that affect their capacity to cause losses. Treatments with sulfur dioxide, fungicides and antioxidants help to reduce losses from postharvest diseases, as does careful attention to humidity and temperature. Hot water treatments (48–55°C for 5–15 minutes) can be used for mango and papaya. Most important, however, is careful handling to minimize injuries. Bruised fruit, or fruit with a damaged skin, is more vulnerable to diseases, spoils more quickly and sells more slowly. Biological control of postharvest diseases is emerging as an effective alternative to chemical methods of control. Antagonists to wound-invading necrotrophic pathogens can be applied directly to fruit wounds. They are applied using delivery systems such as drenches, line sprayers and on-line dips, and a single use can significantly reduce fruit decay. BioSave® is one such pioneering product that was registered by EPA in 1995 for biocontrol of postharvest rots of pome fruit, respectively, and is commercially available. The effectiveness of biocontrol products has some limitations, but their effectiveness can be improved through the control of their formulation and the environment in which they are used or physiological and genetic enhancement of the biocontrol mechanisms. The use of mixtures of beneficial organisms, and the integration of biocontrol with other alternative methods that alone do not provide adequate protection but in combination with biocontrol provide additive or synergistic effects, are other options (Droby et al., 2009). Anthracnose is the most serious postharvest disease of tropical fruits and several subtropical fruits. There are no sure methods for its control, but the

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following procedures can help greatly to reduce its development: (1) an effective preharvest disease control program; (2) careful handling to minimize mechanical injury; (3) avoiding chilling injury and exposure to high temperatures; (4) postharvest treatment with vapor heat or hot water, or hot air for 20 minutes or longer, depending on the temperature; and (5) a five-minute hot water (51.5°C) dip that may be combined with a fungicide (Sommer et al., 2002; Korsten, 2006). 3.7.2 Insect infestation A large number of insects can be carried by fresh fruits during postharvest handling. Many of these insect species, especially the fruit flies of the family Tephritidae (e.g. Mediterranean fruit fly, Oriental fruit fly, Mexican fruit fly, Caribbean fruit fly), can seriously disrupt trade among countries. Continuing globalization of the fresh produce market will be facilitated by use of acceptable disinfestation treatments. Selection of the best treatment for each commodity will depend upon the comparative cost and the efficacy of that treatment against the insects of concern with the least potential for damaging the host (Paull, 1994; Paull and Armstrong, 1994). Much of the research during the past 20 years has been focused on finding alternatives to methyl bromide fumigation (Yahia, 2006). For example, new fumigants such as carbonyl sulfide, methyl iodide and sulfuryl fluoride, insecticidal atmospheres ( 700 g were not allowed into the USA from Mexico for lack of a quarantine treatment against fruit flies, and therefore immersion in water at 46.1°C for 110 minutes was suggested to provide Probit 9 level quarantine security against Mexican fruit fly for fruit weighing more than 700 g and up to 900 g without adversely affecting fruit market quality (Shellie and Mangan, 2002b). The treatment is currently used commercially. Guava fruit infested with third instars of the Caribbean fruit fly immersed in hot water at 46.1°C for 35 minutes and hydro-cooled until fruit center temperatures returned to 24°C had only slight reduction in quality of fruit held at 10°C (Gould and Sharp, 1992). The fruit quality and ripening response of ‘Brazilian’ bananas (Musa sp., group AAB) were determined following hot water immersion treatments for surface disinfestations (Wall, 2004). Summer-harvested fruit were exposed to 47, 49, or 51°C water for 10, 15, and 20 minutes and ripened at 20°C, and winter-harvested fruit were immersed in 48, 49, or 50°C water for 5, 10, and 15 minutes, stored for 12 days at 14°C, and ripened at 22°C. The hot water exposure time had a greater effect than the water temperature on banana fruit ripening. Non-treated bananas ripened after 13 to 15 days, and ripening was delayed by two to seven days when fruit was exposed for 15 or 20 minutes to hot water. Hot water treatments did not inhibit pulp softening, but peels tended to be firmer for bananas immersed in 49 to 51°C water than control fruit. Heat-treated bananas were no different from control fruit in soluble solids content or titratable acidity; however, the conversion of starch to sugars was reduced at higher temperatures and exposure times. Bananas exposed for 20 minutes to hot water had delayed respiratory peaks and ethylene production, especially at 51°C. Mild peel injury was observed on fruit exposed to higher temperatures (49 to 51°C) for longer durations (15 or 20 minutes). Fruit damage using hot air treatments have also been evaluated. Early, mid-, and late-season grapefruits were treated with hot air at 46, 48, and 50°C for three, five, or seven hours to determine the effects of time and temperature on market quality. Early and late-season fruit were more easily damaged by the higher temperatures than midseason fruit (McGuire and Reeder, 1992). Increased times at the lower temperatures had less of a deleterious effect on weight loss, loss of

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firmness and color, and susceptibility to scalding injury and fungal decay than did shorter times at the higher temperatures. Their regression equations predicted that three hours at 48°C or two hours at 49°C would not adversely affect market quality of early and midseason fruit. However, the authors have suggested that it may not be possible to raise the treatment temperature for late-season fruit above 47.5°C without damaging the quality of juice from these fruit based on taste testing. Vapor heat at 43.5°C and 100% RH for 5 h reduced peel pitting five-fold compared to control fruit after five weeks of storage (four weeks at 10°C + one week at 21°C) in freshly harvested Florida grapefruit and did not cause peel discoloration or rind breakdown (Miller et al., 1991b). There was no difference in volume between treated and non-treated fruit after 1 week of storage or in weight loss, peel color, total soluble solids content, acidity, and pH after five weeks, and fruit were slightly less firm after VH treatment and remained less firm throughout storage, compared with control fruit. This study suggested that vapor heat is a potentially viable alternative quarantine treatment for control of the Caribbean fruit fly (A. suspensa) because it is not phytotoxic to grapefruit and has been reported effective for disinfestation of this pest in grapefruit. In a later work, Miller and McDonald (1992) demonstrated that de-greened ‘Marsh’ and ‘Ruby Red’ grapefruit, exposed to vapor heat treatment (43.5°C for 240 minutes), had 45% reduced incidence of aging after four weeks at 16°C plus one week at 21°C, had little effect on change in peel color during treatment or subsequent storage, and no effect on total soluble solids, titratable acidity, and pH. Early season de-greened ‘Dancy’ tangerines subjected to high-temperature, moist, forced-air (HTMFA) treatments using air at 45, 46, or 48°C for 0, 1, 2, 3, or 4 hours, and evaluated immediately after treatment and weekly during three weeks at 4°C had phytotoxic symptoms, such as inferior flavor and darkened flavedo tissue in fruit treated at 46 or 48°C, while fruit heated with 45°C forced moist air had flavedo color, percent juice yield, soluble solids concentration, and flavor ratings similar to those for control fruit (Shellie et al., 1993). Damage factors have also been evaluated with forced air treatments. ‘MacFadyen’ grapefruit infested artificially with late third instars of Mexican fruit fly and treated with forced hot air until the fruit-center temperature was 48°C with an incremental air-temperature increase, with humidity controlled to maintain a dew point that was 2°C lower than the fruit surface temperature, had no fruit damage resulting from scald by condensation and by desiccation (Mangan and Ingle, 1994). The treatment did not significantly affect fruit appearance or flavor quality ratings, although ratings for flavor and overall preference were lower for treated late-season, commercially stored fruit. The flavor of ‘Valencia’ oranges exposed to moist-forced air (MFA) at 47 or 50°C was rated significantly inferior to those exposed to 46°C for 1, 2, 3, or 4 hours (Shellie and Mangan, 1994). The degree minutes that accumulated in the center of the fruit between two and four hours and the maximum fruit center temperature during the heat treatment were associated with inferior fruit flavor. Oranges exposed to the moist-forced air at 46°C for up to four hours could not be distinguished from the non-heated fruit, and therefore these authors have suggested that 46°C is a promising quarantine treatment for ‘Valencia’ oranges. A number of

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volatile compounds that contribute to orange flavor were quantified following hightemperature forced-air treatment to determine if a relationship exists between the flavor loss that is observed following this treatment and the volatile composition of the juice (Obenland et al., 1999). α-pinene, β-myrcene, and limonene were reduced in amount by 60%, 58%, and 34%, respectively, over the course of the five-hours treatment, but the influence of heat on the amount of decanal was less clear, although in one of the two fruit lots there was little change. Ethanol content was reduced by 70% after the initial hour of treatment and then steadily increased to exceed the initial amount during the remaining four hours of treatment. Taste evaluations of the fruit showed a reduction of flavor quality following four hours or more of treatment. Acidity and soluble solids content were nearly unchanged by treatment. Therefore, this work has suggested that alterations in the volatile constituents of oranges by high temperature forced-air treatment may be an important reason behind the negative impact of this treatment on flavor quality. Freshly harvested mangoes treated with forced air at 51.5°C for 125 minutes then stored for one, two, or three weeks at 12°C, followed by 21°C until soft-ripe, lost one per cent more fresh weight than non-treated fruit and developed trace amounts of peel pitting, but had no different total soluble solids content than non-treated fruit, and peel color at the soft-ripe stage was similar (Miller et al., 1991a). Treated fruit generally reached the soft-ripe stage about one day earlier than non-treated fruit regardless of storage duration and had a lower incidence and severity of stem-end rot and anthracnose. The authors have suggested that the trace of pitting on treated fruit likely will not influence consumer acceptance. Studies have been conducted to compare the effect of different heat treatments. The market quality and condition of grapefruit was compared after three heat treatments for quarantine control of Caribbean fruit flies (McGuire, 1991b). Treatment by forced air at 48°C for three hours was compared with immersions in water at either a constant 48°C for two hours or with a gradual increase to 48°C lasting three hours. The immersion at a constant 48°C significantly increased weight loss and promoted injury and decay while reducing firmness and color intensity after four weeks of storage. By more slowly heating fruit in the gradient water immersion, weight, firmness, and natural color were retained, and injury was substantially reduced, but the incidence of decay remained high. No loss in quality resulted from treatment by forced hot air. These heat treatments had little effect on juice characteristics, although acidity was slightly reduced by each method of application. In taste tests, juice from fruit treated in water that was gradually raised to 48°C was preferred over that of fruit treated at a constant 48°C. Four heat treatments for quarantine control of Caribbean fruit flies in mango did not affect fruit quality but variably controlled two postharvest diseases (McGuire, 1991a). Immersion of fruit in water at a constant temperature of 46°C for 90– 115 minutes significantly reduced anthracnose (Collectrichum gloeosporioides) on three cultivars by 60–87%, stem-end rot (Diplodia natalensis) by 61–88%, and treatment by forced air at 46°C for 195 minutes or at 48°C for 150 minutes reduced anthracnose on two cultivars, but an immersion for 150 minutes in which the water temperature gradually rose to 48°C, following a gradient identical to that created by forced air treatment, had no effect on disease severity. Although all heat

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treatments led to increased weight loss during two weeks of storage, fruit treated by gradient hot water immersion were least affected. Hot air treatment and gradient hot water immersion slightly accelerated the softening of fruit, and all heat treatments hastened the development of yellow pigmentation. Therefore, the author has recommended the immersion in water at a constant temperature of 46°C for the disinfestation of mangoes because it controls disease without reducing market quality, and has indicated that forced air treatment at 48°C is tolerated by the fruit and is more effective than forced air at 46°C for disease control. The effect of postharvest hot water treatments (HWT) as an alternative to vapor-heat insect disinfestation of ‘Kensington’ mango on fruit quality was studied by Jacobi et al. (1995). Fruit were given 46°C HWT for 30 minutes at a fruit core temperature of 45°C either 24 hours after harvest or after various conditioning treatments of 4 to 24 hours at 39.1°C in air, and fruit were compared to non-treated fruit after a subsequent seven days at 22°C. The HWT increased fruit softening and reduced chlorophyll fluorescence and disease incidence. The longer conditioning times produced softer fruit. Conditioning reduced damage to the fruit caused by HWT, and preconditioning for eight hours or longer resulted in < 1% of fruit being damaged as shown by cavities, skin scald, and starch layer formation. The quantitatively measured higher mesocarp starch content paralleled the visible starch layer injury. Skin yellowing increased in response to HWTs that were not damaging to the fruit. Several treatments have been developed to reduce or eliminate heat injury. Conditioning fruit at 40°C for up to 16 hours before hot water treatment accelerated fruit ripening, as reflected in higher total soluble solids and lower titratable acidity levels (Jacobi et al., 2001). As fruit maturity increased, the tolerance to hot water treatment-induced skin scalding and the retention of starch layers and starch spots increased and susceptibility to lenticel spotting decreased. A conditioning treatment of either 22 or 40°C before hot water treatment could prevent the appearance of cavities at all maturity levels. The 40°C conditioning temperature was found to be more effective in increasing fruit heat tolerance than the 22°C treatment; the longer the time of conditioning at 40°C, the more effective the treatment. Therefore, for maximum fruit quality, it was recommended that mature fruit are selected and conditioned before hot water treatment to reduce the risk of heat damage. It is proposed that increased sugar concentration in the mesocarp increased the level of fruit heat tolerance (Jacobi et al., 2002). Changes in carbohydrate metabolism of ‘Kensington’ mango fruit from two major production regions in Queensland, Australia, were measured after conditioning fruit with hot air at 40°C for 0, 2, 4, 8, and 16 h or at 22°C for 16 hours (control) followed by hot-water treatment at either 45°C fruit-core temperature for 30 minutes or 47°C fruit-core temperature held for 15 minutes. Advancing physiological maturity of ‘Kensington’ mango fruit was correlated with increased starch concentration within the mesocarp. An α-amylase inhibitor was present in unripe ‘Kensington’ mesocarp. α-Amylase activity was promoted by conditioning fruit at 40°C for eight hours, and this enhanced enzyme activity persisted until the fruit was ripe. Consequently, starch degradation was accelerated and the concentration of total soluble solids was higher in fruit

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conditioned at 40°C for eight hours than in fruit left at the lower temperature of 22°C for 16 hours or not conditioned. Immediately on removal of fruit from hotwater treatment, activities of α-amylase and phosphorylase were inhibited. This inhibition was correlated with higher starch concentration and starch layer and starch spot injuries in these fruit. A positive correlation was also found between increased sucrose concentration and greater starch loss in 40°C conditioned ‘Kensington’ fruit. Immersion of guavas for 35 minutes in water at 46.1°C slowed softening, sweetening, and color development of fruit, delayed ripening by two days, increased susceptibility to chilling injury, decay, and weight loss in storage, but overall loss of quality was minimal (McGuire, 1997a). Waxing fruit within 90 minutes of heat treatment exacerbated chilling injury, further delayed ripening with a concomitant increase in the percentage of fruit not ripening, and caused fruit to remain greener. Waxed fruit had a lower acidity and soluble solids content and did not appear to ripen normally. Although heating did not appreciably affect the percentage of fruit that failed to ripen, the combination of heating and nearly immediate waxing increased the proportion of not ripened fruit to 45%. Heat and wax treatments, alone or in combination, caused CO2 levels to increase significantly before the initiation of ripening, but waxing also reduced the O2 content of fruit at this time. Before ripening, O2 levels were inversely correlated with injury, firmness, date and percentage of fruit ripening, and pH, and directly correlated with peel color and the concentration of acids and sugars in the pulp. Therefore, delaying the waxing of heat-treated guavas or reconditioning them for 24 hours at 20°C before cold storage promoted normal ripening and helped to maintain the quality of heat-treated fruit. Various cooling methods following heat treatment were investigated to reduce injury to carambola fruit caused by heat stress (Miller and McDonald, 2000). Cooling fruit with ice water (IW) caused more severe degradation to carambola quality compared with ambient air (AA), ambient water (AW) or refrigerated air (RA). Cooling fruit after heat treatment with RA at the targeted storage temperature (10°C) resulted in the least damage to carambola. RA, AA, and AW caused similar degradation such as peel pitting, bronzing, decay and weight loss, but AA cooled fruit were the least firm, and AW cooled fruit had the least preferred flavor. At the end of seven days of storage, fruit heated with hot water (HW) were less yellow than vapor heat (VH)-treated fruit, and fruit cooled by AA were more yellow than those cooled by other methods. There was no difference in peel color, total soluble solids, titratable acidity, pH, or mastication texture of pulp among treatment combinations. Therefore, carambolas cooled with refrigerated air had the least injury compared with other cooling methods evaluated. The tolerance of six nectarine cultivars to hot water treatment was evaluated and the effect of addition of NaCl to the treatment solution was tested as a means of reducing treatment damage (Obenland and Aung, 1997). Hot water immersion was extremely damaging to all cultivars tested, although differences in tolerance existed. Treatment at 50°C for 25 minutes, a treatment for fruit fly disinfestation, rendered the fruit of all cultivars unmarketable. NaCl at a concentration of 200 mM reduced the injury rating in all six cultivars tested from severe damage to slight damage, although the latter was still too severe for the fruit

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to be marketable. At the less injurious temperature of 46°C, the slight amount of injury caused by hot water treatment was eliminated in the presence of NaCl. Flesh firmness was not altered by NaCl in the treatment solution, but firmness was slightly greater in fruit treated at 50°C as compared with 46°C. This study concluded that NaCl reduced damage by effectively reducing the amount of water entering the fruit during treatment and may be useful in reducing the damage from hot water immersion treatments used for surface disinfestation. Chilling injury symptoms were reduced when ‘Sharwil’ avocados were held at 37 to 38°C for 17 to 18 hours and then air-cooled at 20°C for four hours before storage at 1.1°C for 14 days or more, but non-heated fruit developed severe surface discoloration and pitting (Sanxter et al., 1994). Chilling injury symptoms were reduced further when the heated fruit were stored in perforated polyethylene bags during storage at 1.1°C, and no treatment equaled or surpassed the quality of fruit in non-treated controls. Hot water (HW) has been shown to cause severe injury to grapefruit. Grapefruit preharvest-treated with gibberellic acid (GA) or not treated, were postharvesttreated with vapor heat or HW such that the surfaces of fruit were exposed to the same rate of temperature increases and treatment durations, and quality attributes were then compared with ambient air (AA) and ambient water (AW) controls after storage (Miller and McDonald, 1997). After four weeks’ storage at 10°C plus one week at 20°C, scald affected 5% of HW and 20% of VH-treated fruit. No scald developed on control fruit, and at the end of storage, mass loss for HW and VH fruit was approximately 5%. HW-treated fruit had a five times higher incidence of aging than VH fruit; however, control fruit showed significantly more aging than all heat-treated fruit. Gibberellic acid and the heat treatments reduced decay relative to the control, and GA-treated fruit remained greener during storage than control fruit. These findings indicate that VH and HW treatments at the temperatures and durations sufficient to control the Caribbean fruit fly will likely cause peel injury to ‘Marsh’ grapefruit produced in Florida, regardless of treatment with GA. Although pre-treatment conditioning and post-treatment cooling can reduce damage to the commodity, it also reduces mortality of the target pest. Hence such treatments cannot be applied in combination with quarantine schedules that have been designed to kill pests with heat. For example, live Anastrepha larvae were found in mangoes imported from Mexico (Scruton 2000). As a consequence, the post-treatment cooling application was prohibited (Heather and Hallman, 2008). Similarly, gradual heating to reach the target core temperature results in much higher survival rates of the pest (Yin et al., 2006) compared to the short ramp-up times used in the development of treatment schedules. Thus conditioning treatments should not be applied until their effect on the target pest has been thoroughly tested. 7.9.4 Modified (MA) and controlled (CA) atmospheres Some commodities are capable of anaerobic metabolism, but insects generally have a lesser capacity, and this can be used to control these insects (Table 7.3). Modified or controlled atmospheres (insecticidal atmospheres with very low O2

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In vitro Walnut Grape Grapes Grapes

Eggs & larvae

Larvae

All

All

All

Anastrepha suspensa

Platynota stultana

Frankliniella occidentalis

Tetranychus pacificus

Citrus

5 d larvae

Anastrepha suspensa

Cydia pomonella

Commodity

Stage

Fruit flies

Table 7.3 Atmospheric conditions used to control various fruit flies

Var/45

Var/45

Var/45

Var/98

10–50/20–80

0/0

O2/CO2 kPa

0

0

0

39–45

10 & 15.6

22–23

Temperature °C

8.1 d

5.8

4.1 d

33–48 h

7d

60 h

Duration

Mitcham et al. (1997)

Mitcham et al. (1997)

Mitcham et al. (1997)

Gaunce et al. (1982)

Benschoter (1987)

Benschoter et al. (1981)

Reference

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Postharvest biology and technology of tropical and subtropical fruits

and/or very high CO2 pressures, with or without the addition of other gases (such as CO) have been tested as quarantine systems (Yahia, 1998; 2008). Insecticidal atmospheres have been used successfully as quarantine systems for some dried horticultural commodities such as raisins and nuts (Yahia, 2008), but do not seem to be tolerated by many fresh horticultural crops (Yahia, 1997a;b;c; 1998; 2006; 2008; Yahia and Vazquez, 1993) (Table 7.4). ‘Sunrise’ papaya fruit exposed to a continuous flow of an atmosphere containing < 0.4% O2 (balance N2) for 0 to 5 d at 20°C had decay and some fruit had developed off-flavors after three days in low O2 plus three days in air at 20°C (Yahia et al., 1992). The intolerance of the fruit to low O2 correlates with an increase in the activity of pyruvate decarboxylase and lactate dehydrogenase but not with the activity of alcohol dehydrogenase. Therefore, the authors suggested that insecticidal O2 (< 0.4%) atmospheres can be used as a quarantine insect Table 7.4 Tolerance of some horticultural commodities to different atmospheres intended to control quarantined pests Commodity Temperature, Atmosphere, kPa °C O2 CO2

Tolerance, Reference days

Avocado

3

Dates Grapes

20

0.25

80

20

0.1–0.4

50–75 1

Yahia and Carrillo-López (1993)

22–28

4–7

60–85 145

Navarro et al. (1998)

Ke et al. (1995)

5

0.5

35–45 6

Ahumada et al. (1996)

10

0.05

0

21

Shellie et al. (1997a)

46

1

20

0.13

Shellie et al. (1997b)

Kiwifruit

40

0.4

20

0.3

Lay-Yee and Whiting (1996)

Mango

20

0.2–0.3

50

5

Yahia (1993; 1994)

20

2

70–80 5

Yahia et al. (1989)

20

0.5

43

0

48 12

Grapefruit

Orange

Yahia and TiznadoHernandez (1993)

50

160 min

Yahia and Ortega-Zaleta (1999)

0.8

67

160 min

Yahia et al. (1997)

1

30–50 3

Leon et al. (1997)

5

0.02

16

Ke and Kader (1989 1990)

5

0.25

23

Ke and Kader (1989; 1990)

10

0.02

15

Ke and Kader (1989; 1990)

5 Papaya

4

20

8.4 0.2–0.4

60

5

Ke and Kader (1989; 1990)

2–3

Yahia (1995) Yahia et al. (1989; 1992)

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control treatment in papaya for periods less than three days at 20°C without the risk of significant fruit injury. Avocado and guava have been shown to be very sensitive to these atmospheres (Yahia, 1997a;b; 1998; 2006; 2008), and mango is very tolerant (Yahia, 1997c; 1998; 2006; 2008; Yahia and Vazquez, 1993). Non SO2-fumigated ‘Thompson Seedless’ table grapes were stored at 5 or 20°C for 6 and 4.5 days, respectively, in air or one of four controlled atmospheres (CA) ; 0.5% O2 + 35% CO2; 0.5% O2 + 45% CO2; 0.5% O2 + 55% CO2; or 100% CO2, and fruit were evaluated for weight loss, berry firmness, soluble solids concentration (SSC), titratable acidity, berry shattering, rachis browning, berry browning, and anaerobic volatiles (Ahumada et al., 1996). Fruit quality was not affected at 5°C with the exception of greater rachis browning in fruit treated with 0.5% O2 + 45% CO2. At 20°C, CA treatments maintained greener rachis compared to the air control; however, SSC was reduced in the fruit treated with 55% and 100% CO2. At both temperatures, CA induced the production of high levels of acetaldehyde and ethanol. Ethanol concentrations were two-thirds lower at 5°C than at 20°C. Consumer preference was negatively affected by some CA treatments for grapes kept at 20°C, but not by any of the treatments at 5°C. 7.9.5 Irradiation Food irradiation is a process by which products are exposed to ionizing radiation to sterilize or kill insects. In 1986, the US Food and Drug Administration (FDA) approved the use of radiation treatments of up to 1 kGy (100 krad) on fruits and vegetables. Radiation may be provided by gamma rays from cobalt-60 or cesium-137 sources, electrons generated from machine sources (e-beam), or by X-rays. Absorbed dose is measured as the quantity of radiation imparted per unit of mass of specified materials. The unit of absorbed dose is the gray (Gy) where 1 gray is equivalent to 1 joule per kilogram. It has been known for several decades that irradiation is effective at killing, sterilizing or preventing further development of a wide variety of insect pests of quarantine importance on perishable fruits and vegetables. Research has shown that the dose required for sterilization of most insects is below 0.50 kGy. Until relatively recently, the only irradiation treatment approved for quarantine use for the US market was for the movement of papaya fruit from Hawaii to the mainland US. The protocol required the papayas be treated in Hawaii with 150 Grays of ionizing radiation for control of fruit fly pests. However, this protocol, which was approved in 1989, was not used until 1995, when two Cobalt-60 irradiation facilities were built. Subsequently, an X-ray facility was opened at Keaau in 2000 and at one point 50% of all papayas exported from Hawaii were irradiated. But because of maintenance problems those numbers have fallen to around 10–15% (Heather and Hallman, 2008), which highlights one of the potential challenges to irradiation treatment. In May of 1996, the USDA APHIS published a policy statement in the Federal Register regarding their position concerning the use of irradiation as a treatment for quarantine pests in plants. Generic dosages were proposed and later accepted

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for various fruit fly species as shown in Table 7.4. The dosages were generic in the sense that the prescribed dose was deemed appropriate regardless of the commodity. Where more than one fruit fly species is present, the dose would be that for the most tolerant species. This generic approach was a departure from traditional quarantine treatment protocols approved by USDA which have been both insect species and commodity specific. Irradiation doses that are needed to kill the insect are higher than those tolerated by fruits, and therefore the other unique feature of irradiation treatments is that they are generally designed to cause sterility or developmental incompetence in insects, not to kill them outright. In the case of fruit flies, APHIS has established the criterion for a successful dose as the non-emergence of adults to prevent such adults from triggering control strategies if detected in traps within areas free of established fruit fly populations. Additional research may support changes to these minimum doses in the future (Torres-Rivera and Hallman, 2007). USDA-APHIS approved the use of irradiation to treat fruit for importation into the United States in 2002, but it was only in 2007 that India began shipping irradiated fruit to the US. Currently, Mexico is shipping irradiated guava and mango to the US (Figs. 7.5 and 7.6). Several countries are developing Work Plans with APHIS to initiate bilateral trade in products irradiated for phytosanitary purposes (Follett and Griffin, 2006). Irradiation has been used since 2004 to disinfest mangoes shipped from Australia to New Zealand of fruit flies without insurmountable incident (Torres-Rivera and Hallman, 2007). According to APHIS, live stages of pests found in a commodity following a Plant Protection and Quarantine (PPQ) prescribed and approved irradiation

Fig. 7.5

Control unit of irradiated plant in Mexico (courtesy of Mr Cesar Moreno, Sterigenics Gamma México).

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Fig. 7.6

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Irradiated guava in Mexico (courtesy of Mr Cesar Moreno, Sterigenics Gamma México).

treatment will be presumed by PPQ to have been effectively treated unless evidence exists to indicate that the integrity of the treatment was inadequate. This means that when irradiation is used as a quarantine treatment, there must be a good degree of trust between the trading partners. Although gamma rays, high energy electrons, and X-rays all have similar effects, gamma rays are most commonly used in food irradiation because of their ability to deeply penetrate pallet loads of food. Gamma irradiation equipment irradiates packaged or bulk commodities by exposing the product to gamma energy from cobalt-60 in closed chambers, which range in size from single modular pallet irradiators to large contract irradiation facilities. The actual cost of food irradiation is influenced by dose requirements, the food’s tolerance of radiation, handling conditions (packaging and stacking requirements), construction costs, financing arrangements, and other variables particular to the situation (Forsythe and Evangelou, 1993). Irradiation is a capital-intensive technology requiring a substantial initial investment, ranging from US$1 million to US$3 million. A major capital cost includes the radiation source (cobalt-60), hardware (irradiator, totes, conveyors, control systems), land (0.2–0.5 Ha), radiation shields, and warehouse (preferably with cold storage). Operating costs include salaries (for fixed and variable labor, must be well trained), utilities, maintenance, taxes/insurance, cobalt-60 replenishment, etc. Radiation plants are costly and would be more economical if used essentially year-round. However, fresh fruit and vegetable production is seasonal, which would require facilities to be, at a minimum, shared among commodities with somewhat different harvest schedules.

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Certain policies are required to ensure system integrity in the application of irradiation as a phytosanitary treatment. These policies focus on pretreatment, treatment and post-treatment conditions as well as required documentation and monitoring. Before treatment, packers and treatment facilities must maintain records concerning the sources of commodities; how untreated commodities are stored and handled in the irradiation facility and packaging requirements. During treatment, the absorbed dose must be measured and monitored, including dose mapping of the minimum and maximum dose utilizing calibrated dosimeters. After treatment, pests may continue to live and develop. Therefore, confidence in the adequacy of irradiation treatments rests with the assurance that the treatment is efficacious against the pest under specific conditions and has been properly conducted and the commodity safeguarded. This requires strict treatment procedures and well designed and closely monitored systems for treatment delivery and safeguards that assure system integrity. Following treatment, packages must be marked and labeled with treatment lot numbers to allow trace back if needed. Consumption of foods irradiated at doses up to 10 kG has been considered safe by the World Health Organization (WHO), the Food and Agriculture Organization (FAO), and the International Atomic Energy Agency. While consumers have concerns associated with the safety of irradiation technology and its effects on food, research indicates that properly irradiated food does not pose a risk to consumers (Thorne, 1983, OTA, 1985). Studies have shown that consumer acceptance of irradiated produce in the US is increasing (Morrison, 1992), but serious social and public policy issues remain. Some produce companies have shied away from irradiation because they fear a backlash from consumers, but attitudes appear to be shifting. Fruits differ in their tolerance to irradiation (Table 7.5). For example, the tolerance of mango and guava fruits is generally good, but there are differences between varieties and stages of maturity. The greater the dose that can be tolerated by the fruit, the less expensive the treatment process. If the commodity is treated in a palletized form or in totes (a packing arrangement feasible with cobalt-60 or cesium-137 irradiation sources) in order for the fruit in the center of the load to receive 150 Grays, the product on the outside may receive two to six times higher dosage (300 to 900 Grays), causing damage to some fruits. The higher the dosimetry ratio (lowest to highest dose administered to a batch of fruit), the more flexibility the operator has, resulting in potentially lower costs to the shipper. By disassembling the pallet and treating product in boxes, the range of doses received by the product can be much smaller, but the cost of treatment is higher as compared to a pallet irradiator due to the additional labor involved. This is also the case for a tote irradiator since these boxes must also be de-palletized. Fruit damage by irradiation is a function of cultivar, irradiation dose and fruit maturity/ripeness at the time of treatment (Boag et al., 1990; Singh, 1990). Symptoms of irradiation stress on fruits include accelerated softening, uneven ripening, and surface damage. Irradiation stress is additive to other stresses

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Table 7.5 Approved irradiation doses for the control of some quarantined pests Scientific name

Common name

Dose (Gray)

Anastrepha ludens

Mexican fruit fly

70

Anastrepha obliqua

West Indian fruit fly

70

Anastrepha serpentina

Sapote fruit fly

Anastrepha suspensa

Caribbean fruit fly

100

Aspidiotus destructor

Coconut scale

150

Bactrocera jarvisi

Jarvis fruit fly

100

Bactrocera tryoni

Queensland fruit fly

100

Brevipalpus chilensis

False red spider mite

300

Conotrachelus nenuphar

Plum curculio

Copitarsia decolora

No common name

100

Croptophlebia ombrodelta

Litchi fruit moth

250

Cryptophlebia illepida

Koa seedworm

250

Cylas formicarius elegantulus

Sweetpotato weevil

150

Cydia pomonella

Codling moth

200

Euscepes postfasciatus

West Indian sweetpotato weevil

150

Grapholita molesta

Oriental fruit moth

200

Omphisa anastomosalis

Sweetpotato vine borer

150

Pseudaulacaspis pentagona

White peach scale

150

Rhagoletis pomonella

Apple maggot

Sternochetus mangiferae (Fabricus)

Mango seed weevil

70

92

60 300

Fruit flies of the family Tephritidae not listed above

150

Plant pests of the class Insecta not listed above, except pupae and adults of the order Lepidoptera

400

(physical, chilling, water), which should be avoided to minimize the negative effects of ionizing radiation. Mango fruit softening was not produced as a result of irradiation in the range of 0.1 to 1.2 kGy (Boag et al., 1990). Fruit which were partially ripe and in their climacteric were largely unaffected by irradiation; that were 25% to 50% ripe Haden mangoes showed no change in the rate of ripening when treated at 250 Grays (Akamine and Goo, 1979). Because utilizing a higher upper limit of dose results in easier logistics and lower cost to the grower, there is a danger that fruit might be exposed to higher doses than they can tolerate while still meeting the minimum phytosanitary dose. This could result in quality issues if practiced. It will depend on the tolerance of mango fruit cultivars to irradiation.

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Several irradiation facilities treat large quantities of fruit and are important in global quarantine programs. In Hawaii, an irradiation facility is available with an electron beam/X-ray source which has similar penetration to gamma sources. Product is stacked three boxes deep on a metal carrier and moved through the facility making two passes by the source. This keeps the max/min dose received down to 1.5 for most products. The facility is currently only used at 30% to 50% capacity. Another older irradiation facility in Palo Alto still operates near Mexico City. Many tests were conducted at this facility in collaboration with USDA and FAO over a long period of time with several fruits, including mango and citrus, but this facility is not currently irradiating fruit for commercial purposes. A relatively new facility has been established, the Sterigenics facility, in the state of Hidalgo, near Mexico City. Sterigenics Inc. is treating guava fruit (Figs. 7.5 and 7.6) and planning to treat other fruits including mangoes. The Sterigenics facility in Mexico has the capacity to treat approximately ten tons of fruit per hour when the entire product is treated at the same settings. The fruit in this system are loaded into totes for movement past the radioactive source. The aluminum totes are 59 cm × 92 cm × 142 cm high. Each tote has a false floor that allows the product to be easily loaded into the top of the tote. The floor is lowered as more and more product is added. The false floor is stainless steel and is raised and lowered by pistons. Forty-five totes are exposed to irradiation at one time and they rotate in a serpentine fashion through the maze so that each side of the tote is treated equally. The shortest cycle time through the irradiator is 1.5 min per position (1.5 × 45 positions = 90 min) for a total treatment time of 90 min minimum. A joint study in 1997 by the International Atomic Energy Agency, the World Health Organization and the Food and Agriculture Organization of the United Nations concluded that there is no safety basis for limiting the amount of irradiation that can be applied to food for human consumption (Hallman, 2000). The use of irradiation with doses of up to 1.0 kilogray (KGy) has been approved by the Food and Drug Administration. Irradiation doses that can kill insects, often in excess of 1KGy, may also damage the commodity, and therefore quarantine treatments have been proposed using sublethal doses that eliminate viability of the insects rather than killing them outright. However, this does result in regulatory problems in that it requires inspectors to accept shipments infested with living pests. Although consumer acceptance of the use of irradiation in foods has slightly improved, its economic feasibility is still one of the major problems facing its commercial application, especially in developing countries. One of the more feasible and potentially useful applications of irradiation in fruits and vegetables is probably for disinfestation as a quarantine treatment. Moy (1993) has reported that all immature stages of a fruit fly will become effectively unviable upon being irradiated at a minimum dose of 150 Gy, the dose level approved by the USDA in January 1989 for treating Hawaiian papayas as a quarantine procedure. This is also well below the dose level approved in April 1986 by the US Food and Drug Administration for irradiating fresh foods for disinfestation and delaying maturation. Low doses (0.15 to 1.0 KGy) of gamma irradiation have been reported to disinfest fruit flies from several fruits such as

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mangoes, papayas, bananas, litchis, and also other insects such as mango seed weevils. Irradiation is an accepted treatment to control quarantine pests in ten fruits and five vegetables for export from Hawaii to the US mainland (Follet, 2004). A generic dose of 150 Gy has been proposed for tephritid fruit flies. Contrary to the 150 Gy dose, approved irradiation quarantine treatment doses for Med fly, melon fly, and oriental fruit fly in Hawaii are 210–250 Gy (Follet, 2004). Work by Follet (2004) showed that 250–300 Gy can control Hawaii’s sweet potato pests. Approved irradiation quarantine treatment doses for Bactrocera cucurbitae (Coquillet), melon fly; Ceratitis capitata (Wiedemann), Medfly; and Bactrocera dorsalis (Hendel), oriental fruit fly, infesting fruits and vegetables for export from Hawaii to the continental United States are 210, 225 and 250 Gy, respectively (Follett and Armstrong, 2004). Irradiation at 250 Gy, as a minimum dose, has been approved as a quarantine treatment for the export of tropical fruits grown in Hawaii (Boylston et al., 2002). In early 1995, the Hawaii Department of Agriculture was granted a special permit from USDA-APHIS allowing untreated Hawaiian fruits to be irradiated in the US mainland (Moy and Wong, 2002). In April 1995, the first shipment of Hawaiian fruit was irradiated at a minimum quarantine dose of 250 Gy in an Isomedix plant near Chicago, and then distributed to supermarkets in Illinois and Ohio (Moy and Wong, 2002). A commercial e-beam/converted X-ray facility was installed by Titan Corp in Hawaii and was operational by late July 2000, making Hawaii the first place in the world to use irradiation as a quarantine treatment of fruits (Moy and Wong, 2002). Ten citrus cultivars grown in Florida, including the orange (Ambersweet, Hamlin, Navel, Pineapple, and Valencia), and five mandarin hybrids (Fallglo, Minneola, Murcott, Sunburst, and Temple), were exposed to irradiation at 0, 150, 300 and 450 Gy, and stored for 14 days at 1°C or 5°C plus three days at 20°C, to determine dose tolerance based on fruit injury (Miller et al., 2000). Softening of ‘Valencia’, ‘Minneola’, ‘Murcott’, and ‘Temple’ was dose-dependent, but that of other cultivars was unaffected. Only ‘Ambersweet’, ‘Valencia’, ‘Minneola’, and ‘Murcott’ did not develop peel pitting at 150 Gy or higher. Total soluble solids of ‘Ambersweet’ and ‘Sunburst’ declined slightly with increasing dose. Titratable acidity of oranges was not affected, but that of ‘Sunburst’ and ‘Temple’ juice was slightly reduced by irradiation at 450 Gy. Juice flavor of ‘Hamlin’, ‘Navel’, ‘Valencia’, and ‘Minneola’, and pulp flavor of ‘Hamlin’, ‘Valencia’, ‘Fallglo’, ‘Minneola’, and ‘Murcott’ was less acceptable after irradiation at 300 or 450 Gy. The appearance of all cultivars was negatively affected by the loss of glossiness with the 450 Gy dose. Less than 1% of fruit decayed and irradiation treatment had no effect on decay. Therefore, this study indicates that the effects of irradiation on citrus fruits are highly variable and both cultivar-dependent and dose-dependent. Grapefruit harvested from gibberellic acid (GA) treated trees were irradiated at 300 or 600 Gy, and evaluated for quality after treatment and simulated commercial storage (Miller and McDonald, 1996). A condition, not observed before with grapefruit, was described by these authors and termed ‘spongy fruit’, which increased as irradiation dosage increased, consisted in peel pitting after five weeks’ storage, which increased from < 2% to 11% and 25% as irradiation

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dose increased from 0 to 300 and 600 Gy. The majority of pitting at 300 Gy was slight, and incidence of decay (mostly green mold) was reduced with thiabendazole (TBZ), and mean decay among all treatments was 21°C) are effective in decreasing fumigant concentration and treatment duration periods because of increased penetration and insecticidal

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activity. In addition, increased fumigant temperature increases the metabolic activity of the pest organism, increasing the rate of fumigant uptake and thus resulting in shorter treatment duration. MA and CA at high temperatures This treatment combines the stress of heat with that of atmospheric stress due to reduced oxygen and/or elevated carbon dioxide concentrations (Neven and Mitcham, 1996; Yahia, 1998; 2008). Reduced oxygen and elevated carbon dioxide atmospheres have been known to be effective in killing various insect pests for many years, but were generally applied at ambient or lower temperatures (Yahia, 1998; 2009). Killing time is faster at elevated temperatures. Along with the forced hot-air, nitrogen is used to replace oxygen, and carbon dioxide is added. The mechanism of control is to increase the respiratory demand of the insects with the heat treatment while at the same time modifying the atmosphere, both of which contribute to the death of the insect. Treatment times with CA at high temperatures can be one-half those with heat treatments alone. This effectiveness is the result of reducing the availability of O2 during a heating stress that hinders the insects’ ability to support elevated metabolic demands due to the heat load. There is also evidence that a heat treatment under anoxic conditions reduces the production of heat shock proteins in insects (Thomas and Shellie, 2000), and elevated CO2 atmospheres may interfere with the insects’ ability to produce ATP (Friedlander, 1993; Zhou et al., 2000; 2001). Heat treatments combined with an anoxic environment can provide quarantine security more rapidly than a heat treatment or an MA/CA treatment alone (Lay-Yee and Whiting, 1996; Moss and Jang, 1991; Neven and Mitcham, 1996; Sonderstrom et al., 1992; Whiting et al., 1991; 1992; 1995; 1996;Whtitng and Hoy, 1997; Yocum and Denlinger, 1994). Several treatments combining MA or CA with heat (Ortega and Yahia, 2000; Yahia and Ortega, 2000, Neven and Mitcham, 1996) have been studied for different crops. Treatments with CA in combination with forced hot air have been tested for control of Mexican fruit fly and West Indian fruit fly in ‘Manila’ mangoes (Yahia and Ortega, 2000; Ortega-Zaleta and Yahia, 2000). ‘Manila’ mangoes tolerated treatment with 0% O2 and 50% CO2 at 3 ppm on produce surfaces (Sapers, 2009). Acidified sodium chlorite (ASC) can be used on produce at concentrations from 500–1200 ppm and followed by a potable water rinse (Sapers, 2009). Hydrogen peroxide, aqueous (liquid) ozone and peroxyacetic acid have all been effective sanitizers for produce with varying results based on times of exposure, concentration, and fruit commodity being evaluated (Sapers, 2009). 8.5.1

Chemical interventions to reduce microbial contamination of mangoes and coconuts The addition of sodium hypochlorite and copper to water in which mangoes are hydrocooled reduced populations of S. Typhimurium and eliminated the potential for internalization of Salmonella into mangoes (Soto et al., 2007). The addition of

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5 mg L−1 hypochlorite and 8 mg L−1 copper ions reduced populations of Salmonella at 6 log CFU ml−1 in simulated 19-L hydrocooling tank (at 23°C) to a level where internalization of the pathogen into the mangoes was not observed (Soto et al., 2007). Four mangoes in each trial were evaluated. In comparison, Salmonella present in the water without the antimicrobial treatment were able to infiltrate into mango pulp, with 2.5 log CFU g−1 recovered from the mango pulp. The number of fruit evaluated in this study was small, and the organic material from additional mangoes may affect the efficacy of the hypochlorite in these dump tanks, but this study shows that chlorination of water can limit the infiltration of Salmonella into mangoes. Washing with hot water and 100 ppm chlorine reduced the levels of microorganisms on the surface and stem scars of mangoes, but did not totally eliminate contamination that could be introduced into the fruit when sliced (Ngarmsak et al., 2006). Chemical sanitizers were also effective in reducing Listeria monocytogenes populations on green coconuts (Walter et al., 2009). Immersion of green coconuts in 200 ppm sodium hypochlorite and 80 ppm peroxyacetic acid reduced L. monocytogenes by 2.7 and 4.7 log CFU/coconut, respectively. 8.5.2

Chemical interventions to reduce microbial contamination on the surface of citrus fruit The use of waxes on oranges reduced the number of microorganisms on the surface of oranges. Alkaline citrus waxes are used for a variety of reasons: to reduce water vapor loss, to enhance surface shine, or to transmit or carry an antimicrobial agent (Pao et al., 1999). Waxes are usually applied by spraying but dips, drips and foams are also less commonly used. Application of waxes (pH 10) to oranges at 50°C for four minutes reduced E. coli counts by 4.7 log CFU cm−2 in mid-section areas, but only by 1 log CFU cm−2 around the stem scar area (Pao et al., 1999). Similar results were observed when wax at pH 11 was applied for two minutes at the same temperature. Chemical treatments have proven less effective on the surface of oranges than physical ones. Immersion of oranges in 100 ppm chlorine dioxide solutions reduced E. coli populations by 3.1 log CFU cm−2 in non-stem scar areas, but only by 1 log CFU cm−2 in stem scar areas (Pao and Davis, 1999). Chlorine dioxide at 100 ppm was more effective than the other antimicrobial solutions tested: 100 ppm chlorine, 200 ppm anionic sanitizer, 80 ppm peroxyacetic sanitizer, and 2% trisodium phosphate. The efficacy of these sanitizers may be limited by their ability to penetrate the surface of the oranges. An alkaline compound, sodium orthophenylphenate (SOPP) at pH 11.8, reduced E. coli counts between 2.9–3.5 log CFU cm−2, regardless of any pre-wetting treatment (Pao et al., 2000). The antimicrobial activity of SOPP may be attributed to the damage to Gram negative bacterial cell walls caused by alkalinity (Mendonca et al., 1994). 8.5.3 Chemical interventions to reduce microbial contamination of melons As with citrus fruits, chemical methods have proven to be less effective on melons than physical ones. A survey of four packinghouses in Texas revealed that melons

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entering packinghouses had significantly higher counts of total aerobic bacteria, total and fecal coliforms and fungi than cantaloupes which were washed and then packed (Materon, 2003), indicating that washing with chlorinated water decreases microbial populations on cantaloupe rinds. Washing inoculated cantaloupes in 1000 ppm sodium hypohchlorite solutions or 5% hydrogen peroxide reduced Salmonella Stanley populations by 3.4 and 3.2 log CFU cm−2, respectively (Ukuku and Sapers, 2001). However, these treatments were increasingly less effective three, five, and six days after inoculation, regardless of whether the inoculated melons were stored at 4 or 20°C. Similarly, S. Stanley was not transferred from rind to flesh of melons treated with hypochlorite or hydrogen peroxide on days 1 or 3 after inoculation and washing, but could be transferred three and five days after washing. In this same study, S. Stanley from melons washed in tap water only was transferred from rind to flesh on all days. These data indicate that chemical sanitizers can be effective in reducing attached Salmonella counts on melon rinds, but surviving cells potentially become more protected by biofilms in the rinds and netting of cantaloupes and more resistant to chemical disinfection the longer they are stored at refrigerated temperatures. Commercial preparations of acidified sodium chlorite (Sanova), at 850 and 1200 ppm, and a peracetic acid (PAA)-based sanitizer (Tsunami 200), at 20 and 40 ppm, reduced S. Poona counts on the surface of cantaloupes by 1.60–2.47 log CFU and 2.21–2.50 log CFU, respectively (Caldwell et al., 2003). Comparatively, sodium hypochlorite solutions at 50 and 200 ppm only affected reductions of 0.35–0.70 log CFU S. Poona, indicating that acidified sodium chlorite and PAA sanitizers are more effective than chlorine solutions in reducing Salmonella populations on cantaloupe rinds (Caldwell et al., 2003). Other researchers have supported the findings that acidified sodium chlorite (Sanova) at 1200 ppm was more effective than 180 ppm sodium hypochlorite and 80 ppm Tsunami (Fan et al., 2009) in reducing S. Poona on cantaloupe rinds. This same study also showed that ASC was more effective than PAA or sodium hypochlorite in reducing total aerobic populations on cantaloupe rinds. Regulations for use of chemical disinfectants in wash water may differ from country to country, and attention should be paid to complying with these rules. 8.5.4 Limitations of chemical disinfectants Chemical disinfectants are most effective when their concentration is monitored and maintained during postharvest fruit processing. Planktonic bacterial cells, those not attached to produce surfaces, are much more susceptible to the bactericidal effects of chemical sanitizers than bacteria which are protected in biofilms or in aggregates on produce surfaces (Solomon and Sharma, 2009). Exopolysaccharide (EPS) produced by bacterial biofilms on fruit surfaces, or organic material released by cut surfaces of fruits, may also serve to inactivate the disinfecting potential of chemical sanitizers. The ability of Salmonella cells to colonize surfaces in the same manner as non-pathogenic epiphytic bacteria (Beattie and Lindow, 1999) may also reduce the ability of chemical disinfectants to kill cells in these protected niches. Chemical disinfectants, including sodium or

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calcium hypochlorite, are most effective in killing bacterial cells when the pH of solution is 4–7, when hypochlorous acid (HOCl) is the predominant chemical species (Marriott, 1999). Hypochlorite solutions are common as sanitizing agents because they are cost-efficient, have a broad spectrum of activity (gram positive and gram negative bacteria), and the concentration (free chlorine) is relatively easy to measure. As pH increases, the ratio of hypochlorite ion (OCl−) to hypochlorous acid increases, decreasing the efficacy of the sanitizer (Marriott, 1999). The main limitation of hypochlorite solutions and similar compounds is that they are rapidly inactivated in the presence of organic matter, and they are corrosive to stainless steel and other metals. Chlorine dioxide (ClO2) is more stable in the presence of organic matter and at higher pH values (up to 8.5) than hypochlorite over a shorter period of time. Overall, the use of chemical disinfectants in improving the safety of tropical fruits is most effective when integrated into an overall food safety management plan that emphasizes good agricultural practices, good manufacturing practices, and standard operating procedures that are designed to emphasize food safety and minimize the risk of contamination. 8.5.5

Physical and biological interventions to reduce contamination of tropical fruits Other physical and biological treatments have been evaluated for their ability to reduce foodborne pathogens on whole and fresh-cut melons. Low dose gamma irradiation of fresh-cut cantaloupe, following immersion in 20°C water, reduced total microbial populations by 2.1 log CFU g−1 (Fan et al., 2006). Surface pasteurization, the immersion of cantaloupes in 76°C water for three min in a commercial washing apparatus, has proven to be an effective treatment to kill Salmonella on the rinds and in the netting of the fruit (Annous et al., 2004). Surface pasteurization reduced total aerobic populations and yeasts and molds on the surface of the cantaloupes stored for up to 20 days after treatment (Fan et al., 2008). Surface pasteurization also resulted in reductions of more than 5 log CFU cm−2 Salmonella Poona on cantaloupes. Similar reductions in E. coli counts were observed during commercial surface pasteurization treatment. These treatments also reduced fungal spoilage in cantaloupes as compared to untreated cantaloupes, while maintaining firmness in cantaloupes. Combination of surface pasteurization with low-dose gamma irradiation (0.5 kGy) reduced microbial populations by 3.3 log CFU cm−2 (Fan et al., 2006). Surface pasteurization treatments using a higher temperature of water (85°C) for 90 seconds resulted in a reduction in Salmonella populations of 4.7 log CFU cm−2 in another type of commercial pasteurization system, but also resulted in increased softness of the rind compared to treatments for 60 s (Solomon et al., 2006). Temperature profiles conducted in this experiment showed a 40°C difference between the temperature at the rind versus the temperature in the flesh. Surface pasteurization of cantaloupes has proven to be more effective than chemical disinfection in reducing pathogenic microbial contamination of these fruits. Care must be taken to preserve the quality of the fruit during these treatments, and proper temperature controls must be used to

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ensure that appropriate microbial reductions are observed. Currently this technology is being evaluated in field trials. For oranges destined for juice production, immersion in water at 70°C for two minutes or 80°C for one minute achieved a 5 log CFU cm−2 of E. coli in nonstem scar areas (Pao and Davis, 1999) without affecting the flavor of the resulting juice. A 5 log CFU cm−2 reduction at stem scar areas on oranges was achieved by immersing fruit in water at 70°C for four minutes or 80°C for two minutes, but these conditions adversely affected the flavor of the resulting juice. Irradiation treatment has also been shown to reduce pathogen contamination on fresh-cut pineapples (Shasidahar, 2007). The use of high pressure processing technologies has been successfully applied to the processing of unpasteurized juices of tropical fruits, fresh-cut fruit, and homogenized products such as guacamole (Aleman et al., 1994; Linton et al., 1999a, 1999b; Bayindirli et al., 2006) Biological treatments, including bacteriophages, have been effective in reducing inoculated pathogens on fresh-cut melons. Bacteriophages are viruses that infect and lyse (kill) bacteria. They are naturally present in foods, and are not harmful or toxigenic to humans. A cocktail of bacteriophages specific for Salmonella Enteritidis applied to inoculated fresh-cut honeydew melons reduced Salmonella by approximately 3.5 log CFU when stored at 5 and 10°C after three days but were less effective when stored at 20°C (Leverentz et al., 2001). Moreover, this work showed that the antimicrobial activity of bacteriophages takes place almost immediately once applied to inoculated melons. Bacteriophages specific for Listeria monocytogenes reduced populations of the pathogen by 2.0–4.6 log CFU/sample on inoculated honeydew melon slices compared to samples not treated with bacteriophages (Leverentz et al., 2003). Bacteriophages applied to fresh-cut cantaloupes inoculated with E. coli O157:H7 stored at 4°C reduced the pathogen by 2.5 log CFU ml−1 compared to untreated controls (Sharma et al., 2009). Bacteriophages are odorless and colorless, so their addition to food should provide a minimal impact to sensory and quality changes.

8.6

Food safety programs used to minimize microbial contamination of fruits

Interventions designed to improve the safety and quality of fruits are not the only method to limit pathogenic contamination on tropical fruits. Good Agricultural Practices (GAPs), Sanitation Standard Operating Procedures (SSOPs), and Good Manufacturing Practices (GMPs) must be implemented and monitored along with the Hazard Analysis and Critical Control Points (HACCP)-based food safety programs to minimize contamination associated with these commodities. These procedures and practices, when implemented properly with oversight and worker training, can help limit pathogenic contamination in harvesting and handling of fruits. GAPs are outlined in the USFDA Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables (1998) which identifies eight principles

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of food safety that must be considered in produce growing and harvesting operations (Gorny and Zagory, 2010). 1. Prevention of pathogen contamination is critical to ensure produce safety. 2. GAP should be implemented in areas in which produce growers and packers have a degree of control; while avoiding negatively impacting other areas of the food supply and/or environment. 3. Fresh produce can be easily contaminated. Human or animal feces can be a significant source of pathogen contamination. 4. The source and quality of water used in field application can have a major impact on produce contamination. 5. It is important to minimize the potential for pathogen contamination as much as possible, especially through careful management and application of manure or municipal biosolid wastes. 6. In order to minimize contamination on fresh produce, it is critical that workers be vigilant in their hygiene and sanitation practices during production, harvesting, sorting, packing and transport. 7. Concurrent to implementing GAP measures, it is critical that producers follow all applicable agricultural practice regulations and laws at the local, state, federal, and international levels, as mandated by the situation and regulations, or corresponding or similar laws, regulations or standards for operators outside the U.S. for agricultural practices. 8. Accountability at all levels of the agricultural environment is important to ensure food safety programs, like GAP, are rigorously and successfully followed. In accordance with these eight principles, there are several practices at the preharvest and postharvest stages that can decrease the risks of contamination. Most tropical and subtropical fruits are perishable with short shelf life. Quality and safety of these fresh fruits can be strongly affected by harvesting and postharvesting practices. Harvesting fruits at their proper maturity is critical since after their separation from the parent plant they receive no more nutritional gains and their physiology changes from primarily growing to aging. Harvesting is labor-intensive and involves much handling, rendering the process susceptible to pathogen transfer via infected harvesting crew members. Workers should follow hygienic practices at all times, and those with transmissible diseases should not handle produce. Sanitary facilities must be provided for all field workers and visitors during harvesting. Tropical and subtropical fruits, such as mangoes, papayas, watermelons, are susceptible to chilling injury at temperatures below 10°C. Therefore, cold storage is not advised in general for the intact fruits in order to maintain quality. However, for fresh-cut fruits, maintaining cold-chain integrity is critical to reducing food safety risks, since bacterial pathogens grow at a rapid, temperature-dependent rate despite the presence of large populations of native microorganisms and the lack of overt signs of quality deterioration. GMPs provide a preventative food safety program designed to ensure food products are prepared, packaged, and stored under sanitary conditions, and are safe

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for human consumption. In the USA, implementation of GMPs is required by law for processing food products including ready to eat fresh-cut products (USFDA, 2008). Although not mandatory for whole produce handling, following GMP guidelines can improve working conditions and produce safety. GMPs cover general provisions, employee hygiene, buildings, facilities and equipment, production and process controls, and describe defect action levels, as well as levels of natural or unavoidable defects in foods that present no health hazards for humans. Personnel GMPs address the issue that food handlers can be a significant source of contamination. This includes all personnel that come in contact with food products or processing surfaces. Processing plant management train and supervise all personnel on how to properly handle foods and comply with GMP standards. Cleaning and sanitation are some of the most important programs in any food processing plant or packing shed. Building, fixtures, and other physical facilities of the plant should be rigorously maintained in order to ensure sanitary conditions and prevent food adulteration. In order to protect against contamination, all foodcontact surfaces must be cleaned frequently. Furthermore, regularly scheduled equipment cleaning and sanitizing assures food products are being processed under hygienic conditions. These should all be components of SSOPs. 8.6.1 Hazard Analysis and Critical Control Points (HACCP) HACCP is a science-based, objective method used to improve food safety by concentrating on identifying hazards and controlling them at their source (Hurst, 2006). The first step in this process is to identify the scope of the problem, followed by composing a team to perform the HACCP analysis, and then describing the product for which the analysis is needed. A flow chart of the operation is then formulated. With fresh fruits, this product flow may consider the preharvest factors that may affect the chance of contamination. Implementing a HACCP program in processing fresh-cut, minimally processed, tropical fruits provides issues and challenges different from processed foods. The lack of a ‘kill step’ in minimally processed tropical fruits makes establishing critical control points (CCPs) more challenging (Hurst, 2006). The lack of a kill step places emphasis on establishing and maintaining microbiologically sound preharvest factors (GAPs), processing standards (SOPs and GMPs), and a sanitation regime (SSOPs) to ensure that critical control points are appropriate and realistic. Implementing these practices must take into account the local and regional context and realities where fruits are being harvested, processed and/or stored. Understanding these cultural factors will enhance the successful implementation of these practices (Piniero and Diaz, 2007).

8.7

Conclusions

The year-round availability of fresh and fresh-cut tropical fruits to consumers worldwide has increased the importance of ensuring their safety. There have been

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numerous documented outbreaks with a variety of fruits and different pathogens. Fruits can become contaminated during field operations or fresh-cut processing through a variety of routes (washes, reptile intrusions, worker handling). Rough and uneven surfaces of fruits provide numerous colonization niches for foodborne pathogens. Chemical interventions are effective in reducing some but not all microbial contamination on the surface of fruits. Some physical methods may have the potential to improve the microbial safety of tropical fruits. Attention should be paid to using hygienic practices throughout the growing, handling, transportation and preparing of these commodities. An integrated approach to understanding the routes of contamination and practices to minimize this risk will benefit all growers, distributors and consumers of tropical and subtropical fruits.

8.8

References

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9 Biotechnology and molecular biology of tropical and subtropical fruits M. A. Islas-Osuna and M. E. Tiznado-Hernández, Research Center for Food and Development, Mexico

Abstract: This chapter discusses the current position on genetic transformation of tropical and subtropical fruits. Many of these plants are non-model systems, and research is driven mainly by their economic importance and the possibility of genetic improvement. The advances in the area of molecular biology are reviewed from the study of individual genes involved in specific biosynthetic pathways, massive sequencing of mRNA as ESTs (expressed sequence tags), to formal transcriptomic and whole genome sequencing projects. To a great extent, the genetic improvement of tropical and subtropical fruits will be determined by the advances in cell biology protocols for transformation and cell culture, and the knowledge of the genes involved. Key words: genetic transformation, quality traits, transcriptome, genome sequencing.

9.1

Introduction

The improvement in the quality characteristics of tropical and subtropical fruits has been difficult to carry out by traditional breeding techniques due to the lack of germoplasm collections and the long life cycle of these species. In consequence, there are not many varieties for almost all the tropical and subtropical fruits, and genetic engineering has been suggested as an alternative for breeding. These techniques allow the introduction of specific genes conferring desirable characteristics to improve quality. Most importantly, these techniques do not have the limitation of the traditional breeding which can only utilize genetic material of related species to improve specific traits. Therefore, the cultivars already available

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are an important source of genetic material. However, genetic engineering can be utilized after tissue culture techniques are developed, the role of specific genes is known, and the plant genomes are available. Tissue culture techniques require knowledge of the organogenesis or induction of a whole plant from plant tissue and the embryogenesis, which is the induction of viable embryos from embryogenic tissues. Fortunately, for many of the tropical and subtropical fruit species analyzed in this chapter, protocols are available for both embryogenesis and organogenesis. In addition, the genomes of some tropical and subtropical fruits are available for fruit improvement, and may allow transcriptional, biochemical and genetic studies. Besides complete genomes, several expression libraries providing EST collections from some fruits have been obtained and compared with those of model plants. These transcriptomes represent the genes that are being actively expressed at particular conditions in a specific type of cell or tissue, since it is comprised of the reverse-transcribed mRNA isolated at a particular time point. Therefore, fruit transcriptome represents the set of mRNAs expressed in specific tissues of the fruit. The transcriptome is different to the genome since some genes generate multiple mRNAs by post-transcriptional processing, and only a subset of genes is expressed in a particular tissue. Therefore, in the absence of genomic information, transcriptome projects are very useful to obtain sequences related to flavor, color and fruit ripening, but also in human health since the biosynthetic pathways for vitamins, fatty acids, antioxidants and bioactive compounds are being revealed. The ESTs produced during transcriptomic analysis represent the most abundant nucleotide sequence source from plant genomes. The information provided by ESTs can be exploited for gene discovery, genome annotation and comparative genomics. Some EST collections are currently available for several crop and model plant species; in this chapter those corresponding to tropical and subtropical fruits will be reviewed. Coding regions of genes as well as transcription factors involved in several quality characteristics, and postharvest shelf life, will also be considered. Among the genes isolated and studied, there are those related to flavor, aroma, fruit color, softening and ripening. Furthermore, many genes are known to play a key role in the fruit response to biotic stress including fungi infection, bacterial infection and virus attack as well as to abiotic stresses including cold stress, which is the most common abiotic stress in these fruits, and to wounding, temperature, drought and salinity stresses. Tissue culture techniques, knowledge about the molecular mechanisms underlying fruit quality traits, genes and transcriptomes available are all critical tools to improve quality characteristics of tropical and subtropical fruits. In this chapter these tools are analyzed and we shall see in the near future efforts to improve the quality characteristics of many tropical and subtropical fruits with the utilization of techniques derived from genetic engineering.

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Biotechnology and molecular biology

9.2

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Genetic transformation, transcriptome sequencing, genome mapping and sequencing of fruits

Two reviews have been published, to the best of our knowledge, about the transformation of tropical fruits (Gomez-Lim and Litz, 2004; Petri and Burgos, 2005) as well as two edited volumes including chapters describing advances in the genetic engineering of banana, citrus, mango, papaya, pineapple, watermelon, avocado, grape and melon (Hui et al., 2002; Pua and Davey, 2007). Another important reference reports advances in biotechnological protocols including somatic embryogenesis, organogenesis and development of transgenic plants in kiwifruit, cashew, mango, pistachio, coconut, date, atemoya, cherimoya, sugar apple, soursop, pineapple, papaya, mangosteen, avocado, fig, banana, guava, olive, carambola, passion fruit, grapefruit, lemon, lime, orange, longan, cacao and grape (Litz, 2005). In this chapter we will try to address the latest developments in tropical fruit genetic transformation although some of the earlier work will also be included (see Table 9.1). Transcriptomics and genomics will also be reviewed.

9.3 Acerola (Malpighia emarginata DC.) Acerola fruits are known to contain a very large amount of ascorbic acid. Mezadri et al. (2006) reported 695 to 4827 mg 100 g−1 ascorbic acid in acerola. Ascorbic acid synthesis is performed through the Smirnoff–Wheeler pathway (Wheeler et al., 1998). The pathway starts from glucose and includes the intermediates GDP-D-mannose, L-galactose, and L-galactono-1, 4-lactone, among others (Smirnoff et al., 2001). Since the GDP-D-mannose pyrophosphorylase (GMP) (EC 2.7.7.13) catalyzes the interconversion of GDP-d-mannose from GTP and α-d-mannose-1-P (Smirnoff et al., 2001), the MgGMP cDNA (GenBank DQ229168) was cloned and sequenced (Badejo et al., 2007) as well as the complete gene (GenBank EU180071) (Badejo et al., 2008). MgGMP mRNA was accumulated at high levels at the beginning of the ripening process, and decreased in mature fruits (Badejo et al., 2007). Furthermore, the amount of ascorbic acid in the fruit correlated with MgGMP mRNA levels during the ripening process. The MgGMP gene promoter was used to create transgenic tobacco plants expressing the β-glucuronidase (uidA) reporter gene and to compare its activity to the cauliflower mosaic 35S virus promoter (CaMV35S) activity. Transient expression of uidA was evaluated in tobacco protoplasts and the MgGMP promoter had higher activity than the CaMV35S promoter. Furthermore, tobacco transgenic plants expressing the MgGMP gene including its promoter showed levels of ascorbic acid that were twice as high as the tobacco isogenic line (Badejo et al., 2008). These results clearly show that the amount of ascorbic acid in acerola is due to the higher level of activity of the MgGMP gene promoter. A study done with other gene of the Smirnoff–Wheeler pathway, MgPMM (GenBank FJ380046), encoding phosphomannomutase (PMM) (EC 5.4.2.8) was reported (Badejo et al., 2009). PMM catalyzes the interconversion of mannose-6-

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Transgene integrated

Banana

Agrobacterium tumefaciens Agrobacterium tumefaciens

Agrobacterium tumefaciens

Agrobacterium Tumefaciens

Agrobacterium Tumefaciens

Agrobacterium tumefaciens

Particle bombardment

Agrobacterium tumefaciens

Cellulase promoter:samK

CaMV35SːːnptII CaMV35SːːuidA

CaMV35SːːnptII CaMV35SːːuidA

Rd29AːːTPS-TPP

UBQ3ːːMSI-99

CaMV35Sːː Antimicrobial peptides

UBQ3ːːOcIΔD86

Gelvin promoterːːuidA Gelvin promoterːːALS

Agrobacterium tumefaciens

Agrobacterium tumefaciens

Transformation protocol

CaMV35SːːPDF1.2

Avocado CaMV35SːːnptII CaMV35SːːuidA

Fruit

Santamaria et al., 2009

Meristematic banana tissues Tolerance to salinity stress

Embryogenic cells

Embryogenic cells

Resistance to nematode Radopholus similes

Atkinson et al., 2004

Resistance against preharvest Sági et al., 1995 and postharvest diseases Verticillium theobromae or Trachysphaera fructigena

Resistance to Fusarium Chakrabarti et al., 2003 oxysporum f.sp. cubense and Mycosphaerella musicola

Ghosh et al., 2009

Embyogenic cell suspension None from immature male flowers

Wounded meristems

Huang et al., 2007

None

Efendi, 2003 Litz et al., 2007 Ganapathi et al., 2001

Raharjo et al., 2008

Cruz-Hernández et al., 1998

Reference

Male flower derived None embryogenic cell suspension culture

Suspension culture cells derived from shoot-tip

Longer postharvest life

Resistance to fungi attack

Embryogenic avocado cultures from Protoplast Embryogenic cultures

None

Engineered genetic trait

Proembryogenic Masses

Plant tissue utilized

Table 9.1 Different strategies to develop transgenic tropical and subtropical plants to improve fruit quality characteristics by the introduction of specific transgenes

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Embryogenic cell cultures obtained from anthers or ovaries Cell suspensions developed from anthers

Particle bombardment

Particle bombardment

Agrobacterium tumefaciens

Agrobacterium tumefaciens

Agrobacterium tumefaciens

Agrobacterium tumefaciens

pUBQ3ːːSP pUBQ3ːːMSI99 pUBQ3ːːMAG2

pUBQ3ːːMSI99

CaMV35SCaMV35Sːːegfp-nptII

CaMV35SːːuidA

CaMV35S ːːVvWRKY2

CaMV35S ΩːːPGIP CaMV35S ːːuidA CaMV35S ːːnptII

Resistance to the attack of bacteria and fungi

Resistance to the attack of bacteria and fungi

None

None Resistance to the attack of Botrytis cinerea, Pythium spp. and Alternaria tenuis Resistance to the attack of Xylella fastidiosa and Botrytis cinerea

Leaves Leaves

Pre-embryogenic calli

Somatic embryos developed None from young leaves

Leaf

Grape

Agrobacterium tumefaciens

CaMV35SːːuidA

None

Reduce bitter taste in the fruit and fruit juice

Epicotyl segments Embryogenic calli

Color in the fruit and in the juice

Epicotyl from etiolated seedlings

Fig

Agrobacterium tumefaciens

CaMV35SːːCHS-AS* CaMV35SːːCHI-AS*

Particle bombardment

Agrobacterium tumefaciens

CaMV35SːːCitPSY FMV34SːːCitPDS CaMV35SːːCitLCY-B

Segments cut from seedlings None

CaMV35SːːuidA Act1-DːːuidA

Agrobacterium tumefaciens

CaMV35Sːːegfp-nptII

Date

Citrus

(Continued overleaf)

Aguero et al., 2005

Mzid et al., 2007

Das et al., 2002

Li et al., 2008

Vidal et al., 2006a

Vidal et al., 2003.

Yancheva et al., 2005

Mousavi et al., 2009

Koca et al., 2009

Costa et al., 2002

Dutt and Grosser, 2009

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Agrobacterium tumefaciens

CaMV35SːːRIP CaMV35SːːRCC2

Akasaka-Kennedy et al., 2004

None

Somatic embryos

CaMV35SːːuidA

Agrobacterium tumefaciens

Longer postharvest shelf life Nunez-Palenius et al., 2007b

Leaf from 10 days old seedlings

CaMV35SːːCMACCO-AS Agrobacterium tumefaciens

Longer postharvest shelf life Cruz-Hernández et al., 1997.

Somatic proembryos of mango

Dong et al., 1991

None

Mathews et al., 1992

Puchooa, 2004

Kobayashi et al., 2000

Koshita et al., 2008

Somatic embryos

None

Resistance to fungi attack

Leaf and petioles

Leaf

Improved color

Leaf and petioles

Biswas et al., 2007

Bornhoff et al., 2005

Yamamoto et al., 2000

Reference

None

Agrobacterium tumefaciens

Resistance to the attack of Uncinula necator and Plasmopara viticola

Leaves

None

Higher resistance to the attack of Uncinula necator

Somatic embryos

Somatic embryos

Engineered genetic trait

Plant tissue utilized

Cotyledon explants

CaMV35SːːuidA CaMV35SːːDHFR

Agrobacterium tumefaciens

CaMV35SːːACCS-AS CaMV35SːːACCO-AS

Melon

Agrobacterium tumefaciens

CaMV35SːːuidA

Mango

Agrobacterium tumefaciens

CaMV35SːːGFP4

Agrobacterium tumefaciens

Litchi

CaMV35SːːSSBIN CaMV35SːːSSLAB CaMV35SːːSSRIP

Agrobacterium tumefaciens

Agrobacterium tumefaciens

Agrobacterium tumefaciens

CaMV35S ΩːːRCC2

CaMV35SːːuidA

Transformation protocol

Transgene integrated

Continued

Kiwifruit CaMV35SːːVlmybA1-2

Guava

Fruit

Table 9.1

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Papaya

Olive

Embryogenic calli Somatic embryogenic cultures from seedling hypocotyls Papaya embryogenic calli at the globular stage Somatic embryos

Particle bombardment

Particle bombardment

Particle bombardment

Particle bombardment

Ubq3ːːpmi

CaMV35SːːDmAMP1

CaMV35SːːCPACCO-1

CaMV35Sːː PRSVCP

Zhu et al., 2007

Zhu et al., 2005

Dhekney et al., 2007

Chen et al., 2001

D’Angeli and Altamura, 2007

Torreblanca et al., 2009

Perez-Barranco et al., 2009

Lambardi et al., 1999

(Continued overleaf)

Resistance to ringspot virus Lines et al., 2002

Longer postharvest shelf life Lopez-Gomez et al., 2009

Resistance to Phytophthora palmivora

None

Improved resistance to cold stress

Embryogenic cultures from hypocotyl segments

Agrobacterium tumefaciens

CaMV35SːːCBF1 CaMV35SːːCBF3

Resistance to the papaya ringspot virus

Agrobacterium tumefaciens

CaMV35SːːRP

Embryogenic calli

Resistance to fungi attack

Agrobacterium tumefaciens

CaMV35SːːOSM

Somatic embryos

Agrobacterium tumefaciens

pUBQːːuidA

None None

Somatic embryos

Particle bombardment

pUBQːːuidA

None

Embryogenic cultures

Somatic embryos

Particle bombardment

CaMV35SːːuidA

Nunez-Palenius et al., 2007a

None

Cotyledons, hypocotyls and non-expanded true leaves

CaMV35SːːuidA

Agrobacterium tumefaciens

Longer postharvest shelf life Guis et al., 2000

Leaf explants

CaMV35SːːCMACCO-AS Agrobacterium tumefaciens

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Somatic embryos

Particle bombardment

Agrobacterium tumefaciens

CaMV35SːːVST 1

CaMV35Sːː PRSVCP

CaMV35Sːː PRSVCP

Note: *AS means antisense direction

CaMV35SːːKETc1.6His Particle CaMV35SːːKETc12.6His bombardment CaMV35Sːː KETc7 CaMV35SːːuidA- mgfp5 Particle bombardment Pineapple Ubi 1ːːbar Agrobacterium OCS-35S CaMV-rice tumefaciens actin I ːːChitinase CaMV35Sːː ap24 CaMV35Sːː ACACS2 Agrobacterium tumefaciens Particle CaMV35Sːː PINPPO1 CaMV35Sːː PINPPO1-AS bombardment Particle Ubi 1ːːPAT bombardment MasːːuidA Agrobacterium tumefaciens CaMV35Sːː MSI-99 Agrobacterium tumefaciens

Somatic embryogenic cultures

Particle bombardment

Transgene integrated

Fruit

Resistance to papaya ringspot virus

Resistance to Phytophthora palmivora

Engineered genetic trait

Phytophthora nicotianae var. parasitica

Longer postharvest shelf life Trusov and Botella, 2006

Embryogenic calli

Friable embryogenic cell cultures Embryogenic calli

Leaves from plant seedlings Resistance to the herbicide bialaphos Friable tissues containing cell None clusters Leaf bases from shoots Resistance to fungi attack growing in vitro

Reduction of blackheart

None

Embryogenic calli

Mhatre et al., 2009

Firoozabady et al., 2006

Sripaoraya et al., 2001

Ko et al., 2006

Yabor et al., 2006

Zhu et al., 2004a

Immunity against cysticer cosis in humans

Hernández et al., 2007

Bau et al., 2003

Tennant et al., 2002

Zhu et al., 2004b

Reference

Embryogenic papaya cells line at globular stage

Embryogenic tissues derived Resistance to papaya from immature zygotic ringspot virus embryos of papaya

Plant tissue utilized

Transformation protocol

Continued

Table 9.1

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phosphate to mannose-1-phosphate and MgPMM mRNA levels correlated with the amount of ascorbic acid in acerola fruits and leaves (Badejo et al., 2009). Accordingly, transgenic tobacco plants over expressing PMM showed levels of ascorbic acid that were twice as high as the isogenic line. These studies show that the particular concentration of ascorbic acid in acerola is due to the genetic expression of the genes encoding some of the Smirnoff–Wheeler pathway enzymes.

9.4 Avocado (Persea americana Mill.) Avocado somatic embryogenesis has been successfully carried out (Pliego-Alfaro and Murashige, 1988; Witjaksono and Litz, 1999). A protocol to regenerate avocado plants in vitro including transient expression of the uidA gene has also been published (Ahmed et al., 1998). In other studies, the introduction of the gene nptII conferring resistance to the kanamycin antibiotic and uidA, in proembryonic tissue of ‘Thomas’ avocado to create transgenic somatic embryos by Agrobacterium infection has been reported (Cruz-Hernández et al., 1998). From these embryos, transformed plants expressing both cDNAs were obtained. Thus, the utilization of the mentioned protocols to improve fruit quality by the introduction of cDNAs conferring resistance to abiotic stress by genetic transformation was demonstrated (Litz and Litz, 2002). Fungal infection in fruit reduces postharvest quality and increases losses. With the aim to improve the biotic resistance of avocado fruit, a construct containing a cDNA encoding the Arabidopsis antifungal plant defensin gene PDF1.2 (GenBank NM123809) was introduced into embryogenic avocado cultures derived from ‘Hass’ protoplasts under the control of the CaMV35S promoter. The grafting technique of transgenic shoots into in vitro grown seedlings was used to obtain fully developed transgenic plants. Overexpression of this gene in avocado may provide a defense against anthracnose and other fungal pathogens (Raharjo et al., 2008). In order to manipulate the synthesis of ethylene in avocado, a construct containing the SAMK cDNA (GenBank NP523296) encoding S-adenosyl-L-methionine hydrolase (SAMK) (EC 3.3.1.2) originated from bacteriophage T3 and a fruit specific cellulase promoter was transformed into avocado somatic embryos. SAMK catalyzes the conversion of the S-adenosyl methionine metabolite, a precursor of 1-aminocyclopropane-1-carboxylic acid, into methylthioadenosine and homoserine (Good et al., 1994). In this way, ethylene biosynthesis could be reduced and ripening could be delayed. Although the transformation was successfully carried out, the induction of plantlets from the transgenic somatic embryos was not possible. Therefore, the effects of the introduced SAMK into the avocado fruit ripening phenomena were more complex (Efendi, 2003). Other studies involving fully transgenic avocado plants expressing SAMK have been made by grafting the in vitro derived transgenic shoots onto three-week-old seedlings (Litz et al., 2007). Much of the avocado transcriptome sequencing has been derived mainly from the floral genome project (FGP) (http://fgp.huck.psu.edu) (Albert et al., 2005; Wall et al., 2009). Nearly 100 000 EST sequences from early development of

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avocado flowers have been collected by the FGP (Albert et al., 2005) and more are currently being developed. These sequences constitute a valuable resource of genes for specific biochemical pathways related to quality characteristics of fruits. In all, 16 558 avocado ESTs are deposited at the dbEST (EST database) release 052110 from NCBI (see Table 9.2). The avocado haploid genome size has been estimated to be 883 Mb and contains 12 chromosomes (Arumuganathan and Early, 1991). A composite genetic map for avocado has recently been reported (Borrone et al., 2009). Twelve linkage groups were generated from an F1 population of 715 individuals derived from reciprocal crosses of two Florida cultivars ‘Tonnage’ and ‘Simmonds’ and 163 molecular markers. ‘Tonnage’ was heterozygous for 152 (93%) loci and ‘Simmonds’ for 64 (39%). The genetic map will enable the detection of quantitative trait loci (QTLs) affecting traits of economic importance in this fruit.

9.5

Banana (Musa acuminata)

Banana fruit genome manipulation to create polyploid organisms has been carried out using different techniques (Arvanitoyannis et al., 2008). As in avocado, banana transgenic plants have been obtained by introducing genes into somatic banana embryos. Furthermore, stable integration of genes into the banana genome has been done by protoplast electroporation of new embryogenic cell suspensions (Sági et al., 1998), particle bombardment of embryogenic cells (Sági et al., 1995; Becker et al., 2000), co-cultivation of wounded meristems with Agrobacterium Table 9.2 Numbers of ESTs for tropical and subtropical fruits (June 25, 2010) Fruit

No. of ESTs (dbEST)

Avocado Banana Duncan grapefruit Orange Lemon Coconut Date Grape Kiwifruit Longan fruit Loquat Mango Mangosteen Melon Pistachio Olive Papaya Pineapple

16 558 5524 8039 208 909 1505 6 78 361 433 57 751 66 4 68 149 35 547 1299 4860 77 393 5659

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(May et al., 1995), and co-cultivation of embryogenic cell suspension culture developed from different banana cultivars with Agrobacterium (Ganapathi et al., 2001 Huang et al., 2007; Ghosh et al., 2009). Thus, it has been possible to develop a banana plant expressing two genes from Saccharomyces cerevisiae, TPS1 and TPP that encode enzymes for the biosynthesis of trehalose (trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase, respectively) under a droughtstress inducible promoter. The main goal was to develop a plant resistant to saline stress and it was found that salinity induced levels of trehalose in the transgenic plants that were twice as high compared with the isogenic lines. Furthermore, the transgenic plants showed better resistance to saline stress as measured by the effect on photosynthesis (Santamaria et al., 2009). Antimicrobial peptides have been used to increase the resistance of banana against fungi and bacteria. Transgenic banana plants resistant to Fusarium oxysporum f. sp. cubense and Mycosphaerella musicola have been developed by introducing a magainin analog, MSI-99 (a class of antimicrobial peptides isolated for the first time from Xenopus laevis skin) into the banana genome (Chakrabarti et al., 2003). Also, transgenic plants resistant to F. oxysporum f. sp. cubense and Mycospaerella fijiensis, and fruits resistant to preharvest and postharvest diseases developed by Verticillium theobromae or Trachysphaera fructigena have been obtained (Sági et al., 1998). Moreover, banana transgenic plants resistant to the nematode Radopholus similis have been obtained using the constitutive promoter of the ubiquitin maize gene. These plants express an altered rice protein cystatin (OcIΔD86), a cysteine protease inhibitor (Atkinson et al., 2004). Also, transgenic banana plants resistant to the attack of Xanthomonas spp, the causal agent of bacterial wilt have been produced, by expressing synthetic cercosporins (Rajasekaran et al., 2001), and plants resistant to F. oxysporum produced by expressing a human lysozyme gene (Pei et al., 2005). In addition, transgenic banana plants have been created to be a vehicle of vaccines for humans. In this context, there are transgenic banana expressing the ‘s’ gene of hepatitis B surface antigen (HBsAg) under the promoter of the ACC oxidase (Kumar et al., 2005). On the other hand, some banana genes encoding enzymes related to quality attributes of the fruit have been analyzed. The xyloglucan endotransglycosylase is a fruit ripening and softening-related enzyme and XET1 mRNA (GenBank EF103136) was found to increase in pulp and peel of ripe banana fruit (Lu et al., 2004). A second xyloglucan endotransglycosylase encoding cDNA, XET2 (GenBank EF103137) was reported. The expression of three pectin methyl esterases, seven xyloglucan endotransglycosylase/hydrolase, a polygalacturonase, an expansin and pectate lyase genes were evaluated during banana ripening, where polygalacturonase gene and a pectin methylesterase were clearly up-regulated (Mbeguie-A-Mbeguie et al., 2009). The α-amylase is an enzyme involved in starch degradation by depolymerizing the α-glucan chains released by the endo-hydrolytic enzymes. The expression levels of its transcript were induced by ethylene and that expression correlated with the decrease in starch content (do Nascimento et al., 2006). The expression of the gene SPS, encoding a sucrose phosphate synthase, involved in sucrose formation, was found to be increased

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Postharvest biology and technology of tropical and subtropical fruits

dramatically during ripening and to be induced strongly by ethylene. In the promoter region of the SPS gene, several responsive elements were identified such as ethylene responsive, auxin responsive, low temperature responsive and light responsive elements (Choudhury et al., 2008). The isolation of 84 up-regulated unigenes during the late ripening stage of banana will allow us to have a better picture of the genes involved in the quality characteristics development of the fruit and to choose the best of them in order to improve the fruit quality by the DNA recombinant technology (Manrique-Trujillo, et al., 2007). Other reports on transcriptomic analysis in Musa leaves are related to drought stress. In Coemans et al. (2005), 10 196 tags were generated from leaf tissue by super-serial analysis of gene expression (SuperSAGE) to characterize global expression in this plant under drought stress. A total of 5292 unigenes were produced using this technology and the top 100 transcripts were annotated, being the most abundant a type 3-metallothionein, representing nearly 3% of total transcripts analyzed. The main discovery was the recovery of a full gene sequence of a novel NADPH: photochlorophyllide oxidoreductase, the key enzyme in chlorophyll biosynthesis (Coemans et al., 2005). This technique could be useful to perform transcriptomics of banana fruits to uncover genes related to quality parameters desirable in postharvest. There is another report (Davey et al., 2009) to profile the response of banana leaf transcriptome to drought stress using genomic DNA-based probe-selection to improve the efficiency of detection of differentially expressed Musa transcripts. With the use of cross-hybridization to Affymetrix oligonucleotide Rice GeneChip® microarrays a total of 2910 banana gene homologues with a >2-fold difference in expression levels were identified. The differentially expressed genes included many functional classes related to biotic and abiotic stress responses. The results obtained highlight another strategy for gene discovery in non-model species. At the dbEST there are 5524 banana ESTs deposited to date.

9.6

Cherimoya (Annona cherimola Mill.)

No cherimoya transgenic plants have been created yet; however, there is a report (Prieto et al., 2007) where the cDNA AcPPO (GenBank DQ990911) encoding polyphenol oxidase, an enzyme responsible for the marked susceptibility to browning of this fruit, has been cloned and studied. A strong induction of the AcPPO mRNA levels was reported for cherimoya after wounding, supporting the function of the gene in the fruit browning phenomena. At the GenBank there are some cDNAs reported to be differentially expressed under cold storage that were identified in cherimoya cv. ‘Concha lisa’. These are the enolase cDNA (GenBank FJ664264) encoding an enzyme of the glycolitic and gluconeogenesis pathways; the AcDPE2 gene (GenBank FJ664262) encoding a transglucosidase essential for the cytosolic metabolism of maltose in plant leaves at night and AcPE gene (GenBank FJ664260) encoding pectinesterase.

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327

Citrus

In the case of the species belonging to the genus Citrus, several protocols to develop transgenic plants have been reported; the first one was published about 18 years ago (Moore et al., 1992) and from there, many protocols utilizing Agrobacterium-mediated transformation have been published for different citrus species (Kaneyoshi et al., 1994; Peña et al., 1995a, Peña et al., 1995b, Peña et al., 1997, Peña et al., 2001; Gutiérrez-E et al., 1997; Bond and Roose, 1998; Cervera et al., 1998; Cervera et al., 2000; Pérez-Molphe-Balch and Ochoa-Alejo, 1998; Luth and Moore, 1999; Domínguez et al., 2000; Yang et al., 2000; Ghorbel et al., 2001). However, the transformation of citrus plants is still inefficient and improved protocols to create transgenic plants in this genus are currently being developed. A more versatile protocol was published (Kayim and Koc, 2005) in which transgenic plants were created from eight different citrus species: ‘Milam’ rough lemon (Citrus jambhiri Lush), ‘Volkamer’ lemon (Citrus volkameriana L.), ‘Rangpur’ lime (Citrus limonia L.), ‘Hamlin’ sweet orange (Citrus sinensis Osbeck), ‘Duncan’ grapefruit (Citrus paradisi Macf.), ‘Sour’ orange (Citrus aurantium L.), ‘Cleopatra’ mandarin (Citrus reticulata Blanco) and ‘Carrizo’ citrange (Citrus sinensis Osbeck × Poncirus trifoliata Raf.) by inducing plasmolysis in the tissue before Agrobacterium infection. The transformation efficiencies depended upon the citrus species; however, they were the highest reported for citrus to date. There is a recent and improved protocol for genetic transformation of juvenile explants of ‘Carrizo’ (Citrus sinensis Osb. × Poncirus trifoliata Raf.), ‘Duncan’ (Citrus paradisi Macf.), ‘Hamlin’ (Citrus sinensis Osbeck) and ‘Mexican Lime’ (Citrus aurantifolia Swingle). This transformation by Agrobacterium includes a preincubation step with hormones and the use of acetosyringone in the media where Agrobacterium was cultured before infection (Dutt and Grosser, 2009).

9.7.1 Duncan grapefruit (Citrus paradisi Macf.) A specific Agrobacterium transformation protocol has been developed for ‘Duncan’ grapefruit. The media composition in which the explants were cultured before transformation and the co-cultivation media, were the most important factors affecting the transformation efficiency (Costa et al., 2002). The color in ‘Duncan’ grapefruit is due to the presence of carotenoids in the juice. Transgenic fruits under the CaMV35S or the figwort mosaic virus 34S (FMV34S) were created to express the genes encoding phytoene synthase, phytoene desaturase, or lycopene-β-cyclase that play a role in the carotenoid biosynthetic pathway. Although no analysis was carried out in fruits, the leaves of several transgenic plants showed an increased pigmentation (Costa et al., 2002). To obtain grapefruit with reduced naringin bitter taste, transgenic plants were produced. In these plants reduced levels of chalcone synthase and chalcone isomerase were obtained to inhibit two steps of the biosynthetic pathway of flavonoids. The approach was done by introducing constructs that expressed

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Postharvest biology and technology of tropical and subtropical fruits

chalcone synthase (CHS) and chalcone isomerase (CHI) cDNA in sense and antisense. Although the analysis were not carried out in fruits, at least one transgenic plant showed very low levels of naringin as compared with the controls. In general, the flavonoid profiles and composition percentages were similar in control and transgenic plants (Koca et al., 2009). There are 8039 ESTs deposited at the dbEST release 052120 for Citrus × paradisi.

9.7.2 Orange (Citrus sinensis L.) The cloning and characterization of genes CsMYC2 (GenBank EF645810) and CsMYB8 (GenBank EF537877) encoding transcription factors that regulate expression of genes for the enzymes of pathways for color development of orange was reported (Cultrone et al., 2009). The expression of CsMYC2 mRNA correlated with the expression of genes encoding enzymes of the anthocyanin biosynthetic pathway. Genes of this pathway are CsCHS (GenBank EU410483) encoding chalcone synthase, CsANS (GenBank AY581048) encoding anthocyanidin synthase and CsUFGT (GenBank CF972319) encoding UDP-glucose-flavonoid 3-O-glucosyltransferase. Therefore, manipulation of color in C. sinensis is possible by altering the temporal and spatial expression of CsMYC2 (Cultrone et al., 2009). Another work reported the relationship between carotenoid accumulation and the expression of genes encoding enzymes for the biosynthesis of carotenoids during fruit maturation in three citrus varieties (Kato et al., 2004). Carotenoids provide bright yellow, orange and red colors to flowers and fruits. Partial cDNA clones whose expression was evaluated are CitPSY (GenBank AB114656) encoding phytoene synthase, CitPDS (GenBank AB114657) encoding phytoene desaturase, CitZDS (GenBank AB114658) encoding xi-carotene desaturase, CitCRTISO (GenBank AB114659) encoding carotenoid isomerase, CitLCYb (GenBank AB114660) encoding lycopene beta-cyclase, CitHYb (GenBank AB114661) encoding beta-ring hydroxylase, CitZEP (GenBank AB114662) encoding zeaxanthin (zea) epoxidase, and CitLCYe (GenBank AB114663) encoding lycopene E-cyclase. A simultaneous increase in the expression of genes CitPSY, CitPDS, CitZDS, CitLCYb, CitHYb and CitZEP coincided with accumulation of β,β-xanthophyll in flavedo of Valencia orange. This work showed that carotenoid accumulation during citrus fruit maturation was highly regulated by the coordination among the expression of the carotenoid biosynthetic genes. The orange (Citrus sinensis L. Osbeck var ‘Ridge Pineapple’) chloroplast genome (GenBank DQ864733) was sequenced to facilitate genetic improvement of this crop. Its length is 160 129 bp and it contains 140 genes, of which 87 are protein coding and 53 are structural RNAs (Bausher et al., 2006). On the other hand, there are 208 909 ESTs deposited at the dbEST from NCBI. 9.7.3 Lemon (Citrus limon) Lemon fruit is known to have a large variety of monoterpenoids in the glands of the fruit flavedo that together with other compounds are components of the lemon

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essential oil. Monoterpenes play different roles in the defense of the fruit against the attack of insects and plant pathogens as well as pollinator attracters. In this regard, the manipulation of the amount of these compounds could improve the resistance of the fruit against biotic stress during postharvest. An important step towards this goal was the cloning of four cDNAs, ClLIMS1 (GenBank AF514287) encoding d-limonene synthase 1, ClLIMS1 (GenBank AF514289) d-limonene synthase 2, ClTS (GenBank AF514286) encoding gamma-terpinene synthase, and ClPINS (GenBank AF514288) encoding beta-pinene synthase. These enzymes are involved in the biosynthesis of monoterpenoids and they were expressed in E. coli and characterized. The recombinant enzymes were found to produce 10 out of 17 monoterpene skeletons present in lemon peel oil (Lücker et al., 2002). There are 1505 ESTs deposited at the dbEST release 052110 for lemon.

9.8

Coconut (Cocos nucifera L.)

No transgenic coconut plants have been reported and in fact this plant is one of the most recalcitrant species for in vitro regeneration (Cueto et al., 1997). Therefore, somatic embryogenesis has been used to regenerate embryos expressing transgenic. Analysis of the genes playing a role in somatic embryogenesis could be helpful to develop in vitro regeneration protocols. There is a report of the isolation of an orthologous locus of the somatic embryogenesis receptor-like kinase (SERK) named CnSERK (GenBank AY791293). SERK is a protein that plays a role in the first steps of somatic embryogenesis in several plants (Santos et al., 2005; Yang and Zhang, 2010). CnSERK was expressed in embryogenic tissues before full embryo development, whereas there was no expression of CnSERK in non-embryogenic tissues. This gene could be used as a molecular maker to aid the development of protocols including somatic embryogenesis of coconut (Perez-Nunez et al., 2009). An important factor leading to postharvest losses is the biotic stress. In this regard, it is important to know that plants express defense proteins for fruit defense. Until now, there has been no suitable model to study coconut molecular responses to the attack of pathogens. Therefore, the defense response in coconut calli was induced with chitosan, a polymer known to induce defense responses in plants (Ebel and Mithöfer, 1998). Accumulation of hydrogen peroxide, induction of β-1,3-glucanase activity and activation of a 46 kDa MAPK (mitogen activated protein kinase) were reported (Lizama-Uc et al., 2007). MAPKs are known to function in plant responses to different biotic and abiotic stresses, including wounding, pathogen infection, temperature stress, drought and salinity stress (Zhang et al., 2006). Besides the above, in the chitosan treated coconut calli, expression of genes CnLI (GenBank AM076489) encoding a receptor-like kinase, CnACT (GenBank AM689520) encoding actin, and CnCLM (GenBank AM167527) encoding a mitochondrial alternative oxidase, was induced. The system utilized is a good experimental approach helpful to uncover the molecular basis of the coconut defense response (Lizama-Uc et al., 2007).

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9.9

Date (Phoenix dactylifera L.)

In the case of dates, transient expression of the β-glucuronidase (uidA) reporter gene by particle bombardment has been reported (Mousavi et al., 2009). The protocol included the utilization of embryogenic callus, somatic embryos as well as leaf and root tissues derived from tissue culture plantlets. The best uidA expression was obtained with the rice actin promoter in all tissues except in roots. The highest frequency of expression was obtained in embryogenic callus. Although no transgenic plants were obtained, this effort undoubtedly will allow in the future the use of the DNA recombinant technology to develop transgenic date fruit with improved quality. The chloroplast complete genome of Phoenix dactylifera (GenBank GU811709) has been completed recently. With a length of 158 455 bp, it contains 139 genes, of which 89 are protein coding and 48 encode structural RNAs. The chloroplast whole genome information is valuable for chloroplast genetic engineering.

9.10

Fig (Ficus carica L.)

In figs, the production of transgenic plants by Agrobacterium-mediated transformation from the common fig ‘Brown Turkey’ (fresh consumption) and ‘Smyrna’ (dry consumption) was reported (Yancheva et al., 2005). The protocol included the introduction of a construct containing the uidA gene and the nptII gene conferring resistance to kanamycin in leaf by using the disarmed strain of Agrobacterium tumefaciens EHA105. Complete transgenic plants were regenerated from the explants. The transgene was detected in the fig genome by PCR, Southern blot or histochemical localization of β-glucuronidase (GUS) reporter activity in plant tissues. No reports, to our knowledge, are available in which the protocol described above has been used to develop fig with improved quality characteristics. Fig maturation is usually not uniform and this is an important parameter to take into consideration to obtain good fruit quality. In order to reduce the maturation differences, olive oil, ethrel/ethephon or auxin are commonly applied to figs. To understand the molecular basis behind these treatments, four cDNAs FcACS1 (GenBank DQ269492), FcACS2 (GenBank DQ269493), FcACS3 (GenBank DQ269494) and Fc-ACO1 (GenBank DQ269495) encoding ACC synthases and ACC oxidase were cloned (Owino et al., 2006). The effect of oil, propylene or auxin treatment on the steady state levels of the four mRNAs was tested. Some of the genes were either positively (FcACS1 and FcACO1) or negatively (Fc-ACS2) regulated by ethylene. Other genes showed a more complex regulation, being activated by auxin and inhibited by ethylene (FcACS3). The knowledge gained in this study could be helpful in the designing of protocols to manipulate ethylene in the fruit and to improve fig maturation. Fig fruit presents a fast softening phenomena during ripening, suggesting the activation of several cell wall enzymes during this stage of development. Genes FcPG1 (GenBank AY487304) and FcPG2 (GenBank AY487305) encoding

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endo-polygalacturonases, FcCEL1 (GenBank AY487304) encoding cellulase, FcENG (GenBank AY487306) encoding endo-glucanase, FcGAL1 (GenBank AY487308) and FcGAL2 (GenBank AY487309) encoding β-galactosidases, FcXTH1 (GenBank AY487310), FcXTH2 (GenBank AY487311) and FcXTH3 (GenBank AY487312) encoding xyloglucan endotransglycosylases, FcARABF1 (GenBank AY487314) encoding α-arabinofuranosidase and FcEXP (GenBank AY487313) encoding expansin were cloned and their expression evaluated during ripening of the fig (Owino et al., 2004). Steady state levels of these 11 mRNAs showed that FcEXP, FcGAL1, FcXTH1, FcXTH2 and FcARABF1 are expressed in the immature stages, and FcPG1, FcPG2, FcGAL2 and FcCEL1 from the beginning of ripening until the overripe stage, whereas FcXTH3 was found active only at the overripe stage. Studies of the regulation of these 11 genes could be helpful to design strategies to control the softening phenomena by developing transgenic fig with modified levels of some genes encoding cell wall enzymes, that will be useful to improve this species.

9.11

Grape (Vitis vinifera L.)

Grape has been extensively studied using molecular biology-derived tools (Roubelakis-Angelakis, 2009). The first attempt to create transgenic plants in V. vinifera was made using petiole explants. In this experiment, only transgenic buds were obtained (Mullins et al., 1990). The selection markers kanamycin and hygromycin were identified using 32 V. vinifera cultivars and intraspecific hybrids (Peros et al., 1998). Later on, the successful creation of transgenic grape by Agrobacterium infection of somatic embryos induced from anther tissue was published (Mozsar et al., 1998). Likewise, the successful creation of transgenic plants in V. vinifera was done with somatic embryos developed from another culture and Agrobacterium (Harst et al., 2000). After that, the protocol was tested successfully in seven major cultivars for wine production, namely: ‘Cabernet Sauvignon’, ‘Shiraz’, ‘Chardonnay’, ‘Riesling’, ‘Sauvignon Blanc’, ‘Chenin Blanc’ and ‘Muscat Gordo Blanco’ (Iocco et al., 2001). However, some of the cultivars were resistant to transformation and experiments to optimize the protocol by changing media composition and Agrobacterium strains were carried out (Torregrosa, et al., 2002). The development of protocols to create transgenic plants in V. vinifera from different tissues such as embryos developed from leaf disks (Das et al., 2002), cryopreserved cell suspension cultures (Wang et al., 2005) and shoot apical meristems (Dutt et al., 2007) was reported. An important advance was made with the successful transformation in planta using dormant buds. This protocol avoids the need to regenerate the plant which sometimes induces somatic mutations, and it also has the advantage of greatly reducing the time needed to obtain a fully developed plant because of the normal reproductive cycle of the grapevine (Fujita et al., 2009). Besides the utilization of Agrobacterium, other protocols used particle bombardment of embryogenic cell cultures of the cultivar ‘Chardonnay’ (Vidal et al., 2003; Vidal et al., 2006a).

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Other improvements made in transgenic plant protocols are the creation of marker-free transgenic plants to eliminate the presence of the antibiotic resistance gene in the plant genome (Dutt et al., 2008), and the utilization of promoters with duplicated enhancers to increase the level of transcription of the gene placed downstream (Li et al., 2004). Transgenic plants of several cultivars of table grape have been created, including ‘Sugraone’ and ‘Crimson Seedless’ (Lopez-Perez et al., 2008), ‘Thompson Seedless’ (Dutt et al., 2007) and ‘Chardonnay’ (Vidal et al., 2003). There are still opportunities to improve the methodology for transgenic plants, creating an active area of research and studies to improve the utilization of Agrobacterium infection (Li et al., 2006; Li et al., 2008; Dhekney et al., 2009a), as well as studies to improve the utilization of particle bombardment (Vidal et al., 2003), and the development and maintenance of Vitis embryogenic cultures of several varieties and species (Dhekney et al., 2008, 2009b). The grapevine transgenic plants created by using a cold inducible transcription factor from Arabidopsis (AtDREB1b) have improved resistance to cold stress. Although the berries have not been tested, they could be resistant to cold stress and this is very important because grapes need to be stored at low temperatures after harvest (Jin et al., 2009). With regard to biotic stress, research has been done to improve grape resistance to phytopathogenic fungi. The induction of genes by the infection of both leaves and berries with Uncinula necator which causes the grapevine powdery mildew has been studied (Jacobs et al., 1999). The induction of several pathogen related proteins encoding extracellular proteins such as acidic class III chitinase, a basic class I glucanase, a thaumatin-like protein and a basic class I chitinase was recorded. Leaves of V. vinifera L. cv. ‘Chardonnay’ were infected with Botrytis cinerea to analyze the type of gene induced in the defense response, and a strong induction of the mRNA levels of a gene encoding a β-1,3-glucanase enzyme after five days of infection was found (Renault et al., 2000). The induction of different chitinases in response to fungi infection was carried out, and it was found that the type of chitinase depends upon the infecting pathogen. Indeed, mRNA of class III chitinases accumulates in unripe berries infected with Plasmopara viticola, but it was not found in berries at later developmental stages infected with Uncinula necator or B. cinerea. In leaves, accumulation of the chitinase class III mRNA was found only with B. cinerea (Robert et al., 2002). Another study was done infecting leaves and berries with B. cinerea. In leaves, the expression of genes encoding phenylalanine ammonia-lyase (PAL), stilbene synthase, an acidic chitinase, a basic chitinase and a polygalacturonase inhibitor protein was induced. On the other hand, in grape berries the expression of the same genes was observed with the exception of the acidic chitinase (Bezier et al., 2002). Studies to understand the defense response of grapevine against bacterial infection have also been carried out. Genes for chitinase class I putatively located in the vacuole and a chitinase class III were induced by the infection of grapevine leaves with Pseudomonas syringae pv. pisi (Robert et al., 2002). The polygalacturonase inhibitor protein (PGIP) is an important defense for the plant against the attack of fungi. Transgenic plants of the cultivars ‘Chardonnay’

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and ‘Thompson Seedless’ expressing pear PGIP were created (Aguero et al., 2006). The development of B. cinerea infection rate in leaves of the transgenic plants was lower as compared with the control plants (Aguero et al., 2005). Transgenic plants of tobacco overexpressing the cDNA encoding VvPGIP1 (GenBank AF499451) were created, and showed up to 69% reduction in the susceptibility to the attack by B. cinerea. Furthermore, the Vitis enzyme PGIP1 isolated from the transgenic tobacco plants inhibited the in vitro activity of polygalacturonase from Aspergillus niger and B. cinerea (Joubert et al., 2006). Transgenic plants of grape expressing the class I chitinase gene from rice, OsRCC2 (GenBank X56787), showed enhanced resistance against the attack of Uncinula necator which causes powdery mildew and a mild resistance to Elisinoe ampelina which causes anthracnose (Yamamoto et al., 2000). In contrast, an experiment with transgenic grape plants expressing cDNAs encoding chitinase and a ribosome inactivating protein have not shown a higher resistance of the plants under field conditions against U. necator and P. viticola, a heterothallic oomycete which causes grapevine downy mildew (Bornhoff et al., 2005). Bacterial infection is also a potential biotic stress for grape berries. Because of this, transgenic plants have also been created with the goal to increase the resistance against the attack of bacteria. In this context, transgenic grape plants expressing a pear PGIP were found to delay the development of infection in leaves infected with Xylella fastidiosa, the causal agent of Pierce’s disease. Furthermore, these plants were found to have lower bacterial titers and better recovery after pruning as compared with the control plants (Aguero et al., 2005). Magainin peptides were isolated from Xenopus skin and have been shown to have antimicrobial broad spectra of activity (Matsuzaki et al., 1997). Thus, transgenic plants of V. vinifera ‘Chardonnay’ were obtained by particle bombardment of a construct expressing a natural magainin-2 or a synthetic derivative. Transgenic plants growing in the greenhouse were infected with either A. tumefaciens vitis strain or U. necator. The transgenic plants showed a great resistance to the infection by Agrobacterium but a rather mild resistance against U. necator. The authors concluded that magainin confer better resistance against bacteria than fungi (Vidal et al., 2006b). Not all the experiments mentioned above were on grape berries; however, the biotechnological potential of these genes to increase berry resistance to biotic stress imposed by fungi and bacteria challenge is clear. The analysis of a transcription factor isolated from a V. vinifera L. cv. ‘Cabernet Sauvignon’ grape berry expression library, called VvWRKY2 (GenBank AY596466) was reported. VvWRKY2 was found to be active in berries and leaves and induced by signals playing a role in plant defense including salicylic acid and hydrogen peroxide (Marchive et al., 2007). Although transgenic grape plants were not created, transgenic tobacco plants overexpressing the mentioned transcription factor were found to be more resistant to the attack of B. cinerea in leaves, Alternaria tenuis in seeds and Phytium spp in roots (Mzid et al., 2007). Considering that this is a gene active in grape berries and that B. cinerea is an important pathogen for grapes, transgenic berries overexpressing this gene most likely will be more

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resistant to the attack of B. cinerea. The partial sequence of a V. vinifera lipid transfer protein 1 called VvLTP1 (GenBank DQ136029) was isolated. Analysis of the promoter sequence found several cis-acting regulatory elements involved in the defense response. Moreover, the promoter was induced by a non-specific fungal elicitor in transgenic cell suspension cultures of V. vinifera and VvLTP1 mRNA in grape plantlets that also showed higher resistance to B. cinerea due to the gene induction (Laquitaine et al., 2006). Although no transgenic grape plants were created, VvLTP1 constitutes a good opportunity for future use with the aim of enhancing the resistance of grape berries to pathogen attack. Besides biotic stress resistance, genes involved in fruit quality characteristics have also been studied. Although transgenic plants were not usually created to improve fruit quality characteristics, the genes to be described are good candidates for future use to manipulate grape berries’ quality. The expression of genes VvPME (GenBank AY043232) encoding pectinmethyl esterase, VvPG1 (GenBank AY043233) and VvPG2 (GenBank EU078975) encoding polygalacturonases was evaluated in grape skin during ripening to define their function in skin ripening. High levels of VvPME mRNA were found throughout berry development until the end of color change. VvPG1 mRNA levels increased during color change correlating with softening of the fruit, whereas expression of VvPG2 began before veraison and was low during skin ripening. There was a clear relationship between the initiation of fruit ripening and fruit softening with the induction of the VvPG2 and VvPG1, respectively (Deytieux-Belleau et al., 2008). Berry sugar content is an important quality component in grapes. An experiment was carried out to study the expression of VvHT1 (GenBank AJ001061) encoding a hexose transport protein, which seems to be specific for sink tissues such as berries. Transgenic tobacco plants were created and there was an induction of the hexose transport by sugar, sucrose and the sucrose isomer palatinose. It was found that VvHT1 helps in the intake of sugar into grape berries and importing leaves of grape, suggesting that perhaps the manipulation of its expression can help to increase the levels of sugars needed in grape berries to improve fruit quality (Atanassova et al., 2003). Ripening of V. vinifera berries does not depend on ethylene, because it is not a climacteric fruit. However, it has been found that brassinosteroids are hormones playing a role in the ripening phenomena of this fruit. A study was reported in which the expression of the cDNAs encoding brassinosteroid-6-oxidase and the brassinosteroid insensitive gene was studied during grape berry development (Symons et al., 2006). The results clearly showed that there was an increase in the amount of brassinosteroids at the beginning of grape berry ripening. Furthermore, the application of external brassinosteroids induced ripening, whereas the use of biosynthetic inhibitors delayed the development of grape ripening. Therefore, there is a biotechnological potential of those genes in the manipulation of grape berry development. Color is also an important quality characteristic of grape berries, and therefore several studies have been carried out to analyze the changes in the activity of genes related to the anthocyanin biosynthesis. Transgenic grape plants were

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created with a construct containing the transcription factor VvMYBA1 that control the gene encoding the enzyme UDP-glucose: flavonoid-3-O-glucosyltransferase, which is critical for anthocyanin biosynthesis and it was cloned from V. vinifera (Ford et al., 1998). In grape, this gene has been found to be active specifically in red skin grapes (Kobayashi et al., 2001; Castellarin and Di Gaspero, 2007). Although grape berries were not analyzed, all the transgenic tissues showed a very intense red coloration indicating the activation of the anthocyanin pathway. Moreover, the activation of a gene encoding an enzyme putatively playing a role in the vacuolar transport of anthocyanin was also recorded (Cutanda-Perez et al., 2009). The expression of a transcription factor MYB12 was shown to activate several genes encoding proteins playing a role in the anthocyanins biosynthetic pathway in response to different environmental stimuli like light or shading (Matus et al., 2009). A cDNA was isolated from a ‘Cabernet Sauvignon’ berry library and called VvMYB5b, and was found to encode a protein belonging to the R2R3-MYB family of transcription factors (Deluc et al., 2008). Based on its similarity to other transcription factor regulating anthocyanin biosynthesis, it was tested whether this gene is able to play a similar role. Transient expression in cells found that this gene product could activate genes encoding enzymes of the flavonoid pathway. Furthermore, tobacco transgenic plants overexpressing the VvMYB5b in tobacco were found to accumulate anthocyanin. It is quite likely that the manipulation of these transcription factors could lead to grapes with a better color. Besides the studies of transcription factors, specific genes encoding enzymes of the anthocyanin biosynthetic pathway have also been analyzed. In this context, the expression of the dihydroflavonol reductase gene was studied by creating transgenic plants expressing a construct in which the uidA gene encoding β-glucuronidase was controlled by the promoter of the mentioned gene (Gollop et al., 2002). Expression of the reporter gene was found in roots, leaves and stems. Although the expression was not tested directly in fruits, cell suspension from fruits also showed expression of the reporter gene. Furthermore, deletion of the promoter region showed that there is a specific responsive element in the promoter playing a function in the expression of the gene in the fruit (Gollop et al., 2002). The synthesis of anthocyanins is derived from metabolites of the phenylpropanoid pathway. Genes encoding the enzymes flavonoid 3′-hydroxylase and flavonoid 3′, 5′-hydroxylase were isolated and studied from this pathway. These genes were found to be active in all tissues of grape that accumulate flavonoids and in the skin of ripening red berries that synthesize mostly anthocyanins (Castellarin et al., 2006). Other studies also analyzed the activity of the mentioned genes, finding that flavonoid 3′,5′-hydroxylase gene was active in the berry skin at the harvest stages in which there is a large accumulation of delphinidin-based anthocyanins (Jeong et al., 2006). Another study, also analyzing the genes involved in the flavonol biosynthesis in grape, found that two genes encoding flavonol synthases showed different expression. Moreover, one of them was expressed at very high levels during ripening of grape berries correlating with flavonol content increase in the berries (Downey et al., 2003). The transcription factor VvMYBF1 responsible for the activation of the flavonol synthase

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gene was already cloned and shown to be active specifically in the skin of grape berries during ripening (Czemmel et al., 2009). Anthocyanins are stored in the vacuoles after synthesis, which is important for color development. Two genes encoding anthocyanin transporters were isolated and shown to be very active during the accumulation of anthocyanin in grape berry ripening. Constructs with green fluorescent protein (GFP) showed that these genes are located in the tonoplast, strongly suggesting their role in the transport of anthocyanin to the vacuole (Gomez et al., 2009). In support of the study just mentioned, two glutathione-S-transferases shown to play a role in the formation of the ligand anthocyanin-glutathione before transport to the vacuole, were cloned and studied (Conn et al., 2008). Recently, phytochemicals have been the subject of an intense research mainly due to their positive effects on human health. Grapes have high concentrations of proanthocyanidins, which are known to have beneficial effects on human health (Yahia, 2010). The increase in these compounds can improve the quality of the grape berry because of the additional health benefit related to the fruit consumption. Some studies have been done with the genes involved in the biosynthesis of proanthocyanidins in grapes. The cloning of a transcription factor called VvMYBPA1 was reported (Gagne et al., 2009). VvMYBPA1 was found to induce the activity of the genes encoding the enzymes leucoanthocyanidin reductase and anthocyanidin reductase. Both enzymes have been found to play an important role in the proanthocyanidins biosynthesis (total tannin, catechin and epicatechin) at the beginning of berry growth as well as during the change in color of grape berry skin (Gagne et al., 2009). Furthermore, it was found that VvMYBPA1 does not induce transcription of the gene VvUFGT (GenBank AB047099) encoding the enzyme UDP-glucose: flavonoid-3-O-glucosyltransferase which is critical for anthocyanin biosynthesis (Bogs et al., 2007). Some of the most helpful genetic components during the design of transgenic plants are the promoter sequences because they direct the gene expression of the gene downstream in specific tissues and during a specific stage of development. From here the importance of work in which the cloning and study of three genes with a very large activity during different stages of berry development was described. One of them, VvAdh1, was found to be active during the early stages of berry development whereas the other two, VvAdh2 and VvGrip4, were active during grape berry ripening (Tesniere et al., 2006). An interesting work has recently been published in which a protein induced by a virus infection, VIGG, was found to correlate with changes in the composition of organic acids and phenols content. Transgenic plants were not created, and VIGG induction by the virus did not bring the same response in the composition of the fruit (Katoh et al., 2009). It would be worthwhile to study the mode of action of this protein in order to be able to improve fruit quality of grape berries by DNA recombinant technology tools in the future. Grape berries with reported transcriptomes are the result of the great interest in manipulating berry development and quality for both economic and health reasons. However, the knowledge of grape berry development and the regulation of ripening

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are scarce. Before 2003 there were just over 400 sequences deposited in GenBank; however, 146 075 sequences were deposited in NCBI for several Vitis species in September 2003. A total of 135 541 ESTs from 58 cDNA libraries representing cv. ‘Cabernet Sauvignon’, ‘Chardonnay’, ‘Pinot Noir’, ‘Shiraz’, ‘Regent’, ‘Ugni Blanc’ and ‘Chasselas’ were taken from different plant organs including berry, leaf, flower, roots, compound bud, berry without seeds, stem, petiole, berry pedicle, shoot tip, seeds and berry skin. Of these ESTs, 48 806 (25.6%) are from berries. Deluc et al. (2007) reported an mRNA expression profiling of grape berries to investigate the transcriptional network responsible for controlling berry development. The mRNA expression patterns of transcription factors, abscisic acid (ABA) biosynthesis and calcium signaling genes, identified candidate factors likely to participate in the progression of key developmental events such as veraison, as well as candidate genes associated with such processes as auxin partitioning within berry cells and aroma compound production. The dbEST had 361 433 ESTs for Vitis vinifera at its release on May 21, 2010 and it represents the tropical specie with more EST deposited. Moreover, the grape genome was sequenced and its length is 487 Mb in 19 chromosomes (Jaillon et al., 2007) (see Table 9.3).

9.12

Guava (Psidium guajava L.)

There is a recently published review of available protocols for organogenesis, somatic embryogenesis and the first attempts to create guava transgenic plants (Rai et al., 2010). Protocols for guava organogenesis were developed more than 20 years ago where whole plants were induced from nodal explants excised from field grown trees and also from explants of in vitro growing seedlings (Amin and Jaiswal, 1987). These protocols were improved by including the establishment of nodal explants cultures before shoot induction (Amin and Jaiswal, 1988). Further research in this area gave rise to protocols in which organogenesis was induced from shoot tips of growth chamber growing seedlings (Papadatou et al., 1990), from in vitro germinated seedlings hypocotyls (Singh et al., 2002) and from nodes excised of plants growing in the greenhouse as well as axillary buds from in vitro growing seedlings (Ali, et al., 2003). Besides organogenesis, somatic embryogenesis has been successfully carried out from ten-week-old zygotic embryos (Rai et al., 2007) and from mesocarp (Chandra et al., 2004). Although regenerating protocols for guava have been available for some time, the first efforts to create transgenic plants have been carried out only very recently. Indeed, successful introduction of cDNAs encoding β-glucuronidase (uidA) and Table 9.3 Tropical and subtropical plant genomes sequenced Fruit

Latin name

References

Type of project

Grape Vitis vinifera L. Jaillon et al., 2007 Complete large-scale Papaya Carica papaya L. Ming et al., 2008 Complete large-scale

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neomycin phosphotransferase (nptII) under the control of the CaMV35S promoter was done by infection of guava plants with Agrobacterium tumefaciens strain LB4404 (Biswas et al., 2007). There is also a report where it was attempted to improve the resistance of the guava fruit to low temperature injury by the introduction of the transcription factors CB1, CB2 and CB3 (which stands for C-repeats binding factors), known to be induced by a low temperatures gene (Gilmour et al., 2004). However, the regeneration of the complete transgenic plants was not possible (Rai et al., 2010). The aroma of guava fruit is an important quality characteristic. The isolation and study of a cDNA encoding a fatty acid 13-hydroperoxide lyase from guava (CYP74B5) has been reported. Expression of the cDNA in E. coli showed that this enzyme is able to convert the 13(S)-hydroperoxylinolenic acid into 12-oxododec-9 (Z)-enoic acid and 3 (Z)-hexenal, clearly demonstrating the nature of the enzyme encoded by the isolated cDNA (Tijet et al., 2000). This cDNA will be available to be used in the improvement of guava fruit quality once more efficient protocols for guava genetic transformation have been developed.

9.13

Kiwifruit (Actinidia deliciosa)

The creation of transgenic kiwifruit plants by Agrobacterium infection has been carried out successfully (Janssen and Gardner, 1993), although the first efforts were initiated a long time ago (Candy, 1987). The isolation of promoters with activity in fruit tissue is very important in the application of DNA recombinant technology to improve fruit quality. In this context, cysteine protease enzymatic activity was assayed and found to be present from the stage of development in which the fruit weighed about half of the maximum until harvest when the activity was very high. The promoter of the gene encoding this enzyme was identified and cloned fused to the β-glucuronidase reporter gene and found to be active (Ershen et al., 1993). Stilbene synthase is an enzyme involved in the synthesis of the phytoalexin trans-resveratrol that is proposed to play a role in plant protection against fungal pathogens (Dercks and Creasy, 1989) since it inhibited conidia germination of B. cinerea under in vitro conditions (Adrian et al., 1997). In order to increase the resistance of kiwifruit to fungal pathogens, transgenic plants that overexpressed pSV25 encoding the stilbene synthase from three Vitis species (V. vinifera, V. labrusca and V. riparia) were created with the CaMV35S promoter (Kobayashi et al., 2000). Instead of resveratrol, the transgenic plants accumulated a glucosil derivative piceid that was inactive against fungi according to the results. When transgenic plants producing the highest amount of piceid in leaves were infected with spores of B. cinerea, no reduction in fungi infection was found. Although resistance was not found in these kiwifruit transgenic plants, they could be healthier for the consumer due to the presence of the piceid molecule that undoubtedly improves fruit quality. Several cultivars of kiwifruit develop a physiological disorder known as low temperature breakdown that reduces the quality of the fruit (Lallu, 1997; Burdon et al., 2007). Knowing the molecular fruit responses to low temperature stress

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can allow the design of kiwifruit with better resistance to this physiological breakdown. Several genes related to the ethylene pathway were isolated from an Actinidia EST database, including ethylene receptors AdETR1 (GenBank EU170628), AdETR2 (GenBank EU170629), AdETR3 (GenBank EU170630) and AdERS1a (GenBank EU170626); AdCTR1-like (Raf-like protein kinase; GenBank EU170631) and EIN3-like (transcription factor) genes AdEIL1 (GenBank EU170633), AdEIL2 (GenBank EU887511), AdEIL3 (GenBank EU887512) and AdEIL4 (GenBank EU887513). The expression of four tested genes encoding ethylene receptors (AdERS1a, AdETR2 and AdETR3), one of the Raf-like protein kinase (AdCTR1) and the four EIN3-like genes, were up-regulated in response to low temperatures (Yin et al., 2009). It has been found in plants that EIN genes can control the activation of ethylene-responsive element binding factors in response to several abiotic stresses such as wounding, cold, high salinity, or drought (Fujimoto et al., 2000). Therefore, the four EIN3-like genes found to be induced during cold stress could be playing a role in the kiwifruit molecular responses to low temperature, perhaps by activating low temperature induced genes. Therefore, they have a potential biotechnological application in improving the resistance of kiwifruit to low temperature breakdown. Kiwifruit is a very important source of vitamin C and several studies have been made to analyze the expression of the enzymes involved in its biosynthesis pathway. The gene AdGDH (GenBank EU525847) encoding the L-galactose dehydrogenase (GDH) was cloned (Laing et al., 2004). GDH catalyzes the last step in vitamin C biosynthesis (Giovannoni, 2007) and it has been useful to study the effects of the environment in its activity as well as in the amount of vitamin C in kiwifruit. The effects of growing kiwifruit at high temperature were evaluated; kiwifruit heated during either cell division or starch accumulation resulted in a reduction of 60% in vitamin C content. Moreover, AdGDH mRNA levels were reduced in the kiwifruit, suggesting the importance of this gene in the ascorbate biosynthesis (Richardson et al., 2004). Expression analysis of the genes AdGME (GenBank GU339037) encoding GTPmannose-3′,5′-epimerase and AdGGT encoding GTP-L-galactose guanyltransferase was done in A. eriantha, A. chinensis and A. deliciosa. These Actinidia species accumulate different amounts of vitamin C. Both enzymes are located in earlier steps of the biosynthesis pathway of vitamin C (Giovannoni, 2007). A strong correlation was found between expression levels of AdGME and AdGGT and the amount of vitamin C in A. eriantha, which can accumulate an amount of vitamin C up to 16 times higher as compared with the other two species. These results suggest that GME and GGT enzymes are important control points in the biosynthetic pathway of vitamin C. Confirmation of this finding was carried out by creating Arabidopsis transgenic plants overexpressing either AdGGT or both AdGME and AdGGT genes. Transgenic plants expressing both genes accumulated a higher amount of vitamin C than control plants (Bulley et al., 2009). The regulatory function uncovered for GME and GGT can be helpful to design protocols to increase the amount of vitamin C in kiwifruit or other fruits and in this way improve the overall fruit quality.

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A transgenic kiwifruit was created expressing a construct in which a transcription factor of V. vinifera, VvmybA1-2 was controlled by the CaMV35S promoter. MybA1-2 transcription factor regulates the expression of genes encoding enzymes for the biosynthesis of anthocyanins. The transgenic kiwifruit plantlets showed a reddish-purple color due to the accumulation of cyanidin. Although fruits were not analyzed, this is a clear example of the potential of the DNA recombinant technology to improve the color in fruits by the introduction of specific genes (Koshita et al., 2008). Lipoxygenase (LOX) is an important enzyme playing a role in the developing of the characteristic flavor (Chen et al., 2004) and aroma (Perez et al., 1999) in some fruits. Six genes AdLOX1 (GenBank DQ497792), AdLOX2 (GenBank DQ497797), AdLOX3 (GenBank DQ497795), AdLOX4 (GenBank DQ497793), AdLOX5 (GenBank DQ497796) and AdLOX6 (GenBank DQ497794) encoding lipoxygenases were cloned from the kiwifruit EST database (Zhang et al., 2006). The expression of the AdLOX genes was evaluated during kiwifruit ripening. AdLOX1 and AdLOX5 were highly expressed during ripening and their expression was inhibited by 1-MCP treatment, whereas AdLOX2, AdLOX3, AdLOX4, and AdLOX6 were down-regulated during fruit ripening. LOX1 and LOX5 are important for the development of the characteristic aroma in kiwifruit. Although no transgenic plants were created, there is a clear biotechnological potential of the LOX genes studied to improve the aroma in kiwifruit (Zhang et al., 2009). Fruit softening is very important in the final quality of the fruit. In order to understand this phenomenon in kiwifruit the isolation and expression of six cDNA clones AdXET1, AdXET2, AdXET3, AdXET4, AdXET5 and AdXET6 encoding xyloglucan endotransglycosylases (XET) from ripe kiwifruit was reported (Schroder et al., 1998). Northern analysis indicated that AdXETs expression was induced in ripening kiwifruit, when endogenous ethylene could be first detected and the highest expression of AdXET genes was in climateric samples when kiwifruit were soft. XET enzymes depolimerize xyloglucan from cell walls. Moreover, genes AeXTH1 (GenBank EU494946), AsXTH2 (GenBank EU494947), AeXTH3 (GenBank EU494948), AdXTH4 (GenBank EU494949), AdXTH5 (GenBank EU494950), AdXTH6 (GenBank EU494951), AdXTH7 (GenBank EU494952), AdXTH8 (GenBank EU494953), AhXTH9 (GenBank EU494954), AdXTH10 (GenBank EU494955), AcXTH11 (GenBank EU494956), AeXTH12 (GenBank EU494957), AdXTH13 (GenBank EU494958) and AdXTH14 (GenBank EU494959) encoding xyloglucan endotransglucosylase/hydrolase (XTH) were isolated and characterized (Atkinson et al., 2009). XTH enzymes disassemble xyloglucan loosening the plant cell walls. The XTHs contained the two conserved glutamic acid residues at the active site of XTH. XTH5, XTH7 and XTH14 were overexpressed in E. coli and recombinant proteins had XTH activity. Quantitative RT-PCR was done to identify XTH transcripts in different tissues and ripe fruit. AdXTH4, AdXTH5 and AdXTH7 were much more expressed in ripe kiwifruit; AdXTH7 was highly expressed in outer pericarp and its levels decreased during the rapid softening phase of the fruit. This work is the first to investigate the role of XTH in fruit ripening.

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Crowhurst et al. (2008) produced ETS from kiwifruit (Actinidia spp.) to discover genes related to fruit quality and health. The ESTs were obtained from A. chinensis, A. deliciosa, A. arguta and A. eriantha. From a total of 132 577 ESTs, 41 858 resulted in unigenes. Within the flavor-related gene family, acyltransferases were identified, and in the fragrance-related gene family, carboxylesterases that are involved in the terpenoid biosynthesis pathway were identified. Also ESTs were identified for genes of color pathways controlling chlorophyll degradation and carotenoid biosynthesis. ESTs related to health are from genes involved in ascorbic and quinic acid biosynthesis. These large collections of ESTs will allow the researchers to undertake the challenge of investigating the molecular basis of genetic diversity in this fruit.

9.14

Litchi (Litchi chinensis Sonn.)

In litchi, there are no protocols for the creation of transgenic plants. However, the introduction of a construct containing the green fluorescent protein (GFP) transcriptionally controlled by the CaMV35S promoter was attempted by Agrobacterium infection. The expression of GFP in regenerated leaves and callus after four weeks of infection was reported, although no transgenic plantlets were obtained (Puchooa, 2004). Somatic embryogenesis and plant regeneration of litchi from protoplasts (Yu et al., 2000) and leaves (Raharjo and Litz, 2007) have been reported, since these are important steps in the developing of transgenic plants; indeed, in the near future litchi transgenic plants will be produced. Fruit cracking is a problem in some cultivars of litchi, leading to a reduction in fruit quality. Advances in the understanding of the molecular basis of this phenomenon were made in a work in which the expression of two cDNAs LcEXP (GenBank EF446292) and LcEXP2 (GenBank EF446293) encoding expansins (EXP) were studied at different stages of development in the pericarp and aril of the cracking susceptible cultivar ‘Nuomici’ and of the cracking resistant cultivar ‘Huaizhi’. Differences in the expression of the two genes during the different stages of fruit development as well as in the different tissues of the fruit were reported. It was concluded that these genes play a role during fruit growth and perhaps in the fruit cracking phenomena (Yong et al., 2006).

9.15

Longan (Dimocarpus longan Lour.)

For longan fruit there are no protocols available to create transgenic plants; however, somatic embryogenesis and establishment of plantlets have been carried out successfully from longan calli cryopreserved (Matsumoto et al., 2004). Therefore, longan transgenic plants may be available in the near future. Aril breakdown is a very important problem reducing fruit quality during postharvest shelf life of longan fruit. With the goal of understanding the molecular mechanism underlying this phenomena, the expression of three genes DlEXP1

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(GenBank EU416313), DlEXP2 (GenBank EU416314) and DlEXP3 (GenBank EU416315) encoding expansins and three genes DlXET1, DlXET2 and DlXET3 encoding xyloglucan endotransglucosylases was studied during fruit storage at 25°C or 4°C (Zhong et al., 2008). The expression of these genes correlated well with either early (DlXET3) or late aril breakdown (DlEXP3 and DlXET1 and DlXET2) during storage at the different temperatures. Furthermore, one of the expansin genes expression (DlEXP2) was found to be induced within 12 hours after the fruit transference from low temperature to room temperature (Zhong et al., 2008). Three endo-1, 4-beta-glucanase genes DlEG1 (GenBank GQ261871), DlEG2 (GenBank GQ261872) and DlEG3 (GenBank GQ261873) were characterized during longan fruit growth and development. These DlEGs presented different expression patterns in different tissues and only DlEG3 showed fruit-specific expression (Chen et al., 2009).

9.16

Loquat (Eriobotrya japonica L.)

In loquat fruit there are no transgenic plants created; however, a protocol has recently been published to develop plantlets in three cultivars of this species from cultured anthers (Li et al., 2008). Perhaps this new development will help in the near future in the development of transgenic plants. Chilling injury (CI) can reduce the postharvest quality of some cultivars of loquat fruit (Cai et al., 2006). With the aim of understanding the involvement of ethylene in this physiological disorder, expression of some genes involved in the ethylene signal transduction pathway was studied in two loquat cultivars differing in their susceptibility to develop CI. Changes in expression of three ethylene receptor genes EjETR1 (GenBank FJ624867), EjERS1a (GenBank FJ624871), EjERS1b (GenBank FJ624870), one CTR1-like (GenBank FJ624869) gene, and one EIN3-like EIL1 (GenBank FJ624868) were isolated and characterized in ripening fruit (Wang et al., 2010). These genes were differentially expressed within and between fruit of these two cultivars during low temperature storage of the CI susceptible cultivar ‘Luoyangqing’ and of the CI resistant cultivar ‘Baisha’. Although the main differences were in the transcript expression levels rather than in the type of pattern, an interesting finding was that the expression of EjETR1 and EjEIL1 was highly correlated during the CI development symptoms in the loquat cultivar ‘Luoyangqing’. The firmness of fruit is an important quality characteristic during postharvest shelf life. A study aiming to explain the genes involved in loquat fruit softening analyzed the expression of four genes EjEXPA1 (GenBank EU123919), EjEXPA2 (GenBank EU123920), EjEXPA3 (GenBank EU123921) and EjEXPA4 (GenBank EU123922) encoding expansins in the loquat cultivars ‘Luoyangqing’ and ‘Baisha’ and found a close correlation between the increase in expression of the EjEXPA1 and lignification development in the ‘Luoyangqing’ cultivar during storage at 0°C. Softening of the ‘Baisha’ cultivar was correlated with the increased

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expression of EjEXPA1 and EjEXPA4 isozymes. It was concluded that EjEXPA1 may have a role in lignification development and EjEXPA1 and EjEXPA4 isozymes may be active in fruit softening during development (Yang et al., 2008). Another study also related to fruit firmness was conducted to identify genes playing a role in the lignification of some loquat cultivars, which is an important phenomena reducing the quality of the fruit. Six cDNAs encoding enzymes with a role in lignin biosynthesis were isolated from ‘Luoyangqing’, a cultivar with the tendency to develop lignin during development, namely: EjPAL1, EjPAL2 encoding phenylalanine ammonia lyase (PAL), Ej4CL encoding 4-coumarate: coenzyme A ligase (4CL), EjCAD1 and EjCAD2 encoding isozymes of cinnamyl alcohol dehydrogenase (CAD), as well as EjPOD encoding a peroxidase enzyme (POD). The expression of the genes was compared between a cultivar with a tendency to develop lignin, ‘Luoyangqing’, and a cultivar not developing lignin, ‘Baisha’. It was found that the gene expression of EjCAD1 and EjPOD correlates more with lignification of loquat flesh tissue. Also, the EjCAD1 was highly expressed in loquat fruit developing chilling injury at low temperatures, and so perhaps may play a role in lignification of flesh tissue, one of the symptoms of the chilling injury physiological disorder in loquat (Shan et al., 2008).

9.17

Mango (Mangifera indica L.)

In mango fruit the induction of embryos from nucellar tissues has been carried out successfully from either polyembryonic cultivars (Litz et al., 1982; RiveraDomínguez et al., 2004) or monembryonic ones (Litz, 1984). Now, it is possible to get a complete plant from nucellar tissue as follows: induction of embryogenic culture from nucellus, maintenance of embryogenic culture, development of morphologically normal embryos and germination of somatic embryos into welldeveloped plantlets (Krishna and Singh, 2007). Transgenic mango plants were developed using Agrobacterium infection in somatic embryos and introducing the gene encoding β-glucuronidase reporter gene. Stable integration of this construct was probed by Southern blot analysis (Mathews et al., 1992). Ethylene triggers the initiation of mango fruit ripening and because of that, any delay in the initiation of its synthesis could allow the manipulation of the postharvest shelf life of this fleshy fruit (Bapat et al., 2010). An attempt to reduce the expression of two enzymes from the ethylene biosynthetic pathway was made by introducing in antisense orientation the genes encoding the ACC oxidase and the ACC synthase in mango somatic embryos (Cruz-Hernández et al., 1997). The presence of the nptII gene encoding the neomycin phosphotransferase enzyme in the mango genome was confirmed by PCR and Southern blot. Furthermore, the researchers were able to create mature transformed embryos and it is expected that the transgenic mango will show the effects of either very low levels or the complete absence of ethylene in the plant and fruit. In order to understand the genes playing a role in the ethylene mode of action, the expression of MiETR1 encoding an ethylene receptor from mango was

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evaluated (Martínez et al., 2001). MiETR1 (GenBank AF227742) is expressed in the mesocarp during ripening and in response to wounding. It was interesting to find that this gene was induced both by wounding and by ripening. Another study reported the isolation from ripe mango fruit of MiPEL1 (GenBank AY987389), encoding the cell wall enzyme pectate lyase (Chourasia et al., 2006). MiPEL1 was highly expressed during fruit ripening and it was reduced in 1-MCP treated fruits, suggesting the role of ethylene in its induction. Furthermore, MiPEL1 gene expression was correlated with the increase in pectin solubilization. The authors of the work suggested that this is a gene playing an important role in fruit softening. A gene MiCEL1 (GenBank EF608067) encoding an endo-β-1,4-glucanase (hydrolysis of cellulose) was also cloned and characterized (Chourasia et al., 2008). Analysis of the gene product allowed the identification of a cellulose binding domain as well as a signal peptide characteristic of enzymes targeted to the cell wall. Furthermore, MiCEL1 was expressed only in fruits and CEL1 enzyme activity during fruit ripening correlates with a reduction in the amount of the cellulose of the fruit cell wall suggesting a role for this enzyme in fruit softening. An important characteristic of fruit quality is the texture of the flesh, and in mango the development of uneven flesh softening is a frequent physiological disorder (Chaplin et al., 1990). PCR based subtractive hybridization was carried out from healthy and spongy tissue affected mango fruit to investigate the molecular basis of that disorder and the expression of selected genes was analyzed. Expression of two ESTs (GenBank CD002004 and CD002000) related to catalase, an EST (GenBank CD002005) related to alcohol dehydrogenase and one EST (GenBank CB933771) related to keratin-associated protein were induced in the spongy tissue of mango fruit. Expression of one EST (GenBank CB933774) related to a ribosomal protein, one EST (GenBank CB933772) related to fructose-bisphosphate aldolase and (GenBank CB933775) related to cysthathionine gamma synthase was reduced in spongy tissue. This study will help to design a strategy to control the spongy tissue physiological disorder (Vasanthaiah et al., 2006). Several studies dealing with the analysis of genes putatively playing a role in flesh softening in mango have been published. The cloning and characterization of MiEXPA1 (GenBank AY600964) encoding an alpha expansin enzyme was reported. MiEXPA1 was active during fruit softening and induced by ethylene. Moreover, treatment of the mango fruit with 1-MCP inhibited the transcription of MiEXPA1 as well as fruit softening, strongly suggesting the role of this expansin in mango fruit softening (Sane et al., 2005). In a recent work (Pandit et al., 2010), 18 cDNAs related to the physiology and biochemistry of mango fruit cv. ‘Alphonso’ were isolated and their expression was evaluated. The 18 identified were: MiIPPI (GenBank EU513264) encoding isopentenyl pyrophosphate isomerase, MiGPPS (GenBank EU513265) encoding geranyl pyrophosphate synthase, MiMTPS (GenBank EU513266) encoding monoterpene synthase, MiGGPPS (GenBank EU513267) encoding geranylgeranyl pyrophosphate synthase, MiFPPS (GenBank EU513268) encoding farnesyl pyrophosphate synthase, MiSqTPS (GenBank EU513269) encoding sesquiterpene synthase, MiIsoCH (GenBank EU513270) encoding isochorismate hydrolase, MiGT

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(GenBank EU513271) encoding glucosyl transferase, MiLOX (GenBank EU513272) encoding lipoxygenase, MiMDHAR (GenBank EU513274) encoding monohydrogenase ascorbate reductase, Mi14-3-3 (GenBank EU513275) encoding a 14-3-3 protein, MiMT (GenBank EU513276) encoding a metallothionein, MiMeTr (GenBank EU513277) encoding a methyltransferase, MisHSP (GenBank EU513278) encoding a small heat shock protein, MiCHIT (GenBank EU513279) encoding a chitinase, MiCysPI (GenBank EU513280) encoding a cysteine proteinase inhibitor, MiERF (GenBank EU513281) encoding an ethylene response factor, MiUbqPL (GenBank EU513282) encoding ubiquitin-protein ligase and MiEF1 (GenBank EU513283) encoding elongation factor 1-alpha. There are 68 mango ESTs deposited in the dbEST release 052110, as well as one ETR (GenBank AY685130) and one EST for PAL (GenBank GU266281). This is an area of opportunity to produce more ESTs since mango has economic value.

9.18

Mangosteen (Garcinia mangostana L.)

In the case of mangosteen, there are no protocols available to create transgenic plants; however, somatic embryogenesis has been carried out successfully from seeds (Van Minh, 2005) and organogenesis has been induced from seeds (Normah et al., 1992), leaves (Goh et al., 1990; Te-chato and Lim, 1999) and cotyledons (Goh et al., 1988). Therefore, the protocols to utilize the tools from the DNA recombinant technology are already developed and perhaps in the near future we will see the first efforts in this direction. The color development is an important quality characteristic in mangosteen fruits. In this regard, three type MYB transcription factors GmMYB1 (GenBank FJ197135), GmMYB7 (GenBank FJ197136) and GmMYB10 (GenBank FJ197137) were cloned and found to regulate anthocyanin biosynthesis during mangosteen ripening. Genes GmPAL (GenBank FJ197127) encoding the enzyme PAL, GmCHS (GenBank FJ197128) encoding the enzyme chalcone synthase, GmCHI (GenBank FJ197129) encoding the enzyme chalcone isomerase, GmF3H (GenBank FJ197131) encoding the enzyme flavanone-3-hydroxylase, GmF3′H (GenBank FJ197132) encoding the enzyme flavonoid 3′-hydroxylase, GmDFR (GenBank FJ197130) encoding the enzyme dihydroflavonol-4-reductase, GmLDOX (GenBank FJ197133) encoding the enzyme leucoanthocyanidin dioxygenase and GmUFGT (GenBank FJ197134) encoding the enzyme UDP-glucose:Xavonoid 3-O-glucosyltransferase were also cloned. GmMYB10 mRNA and GmUFGT mRNA levels were highly abundant with onset of pigmentation and during red coloration. The results suggest that GmMYB10 is important for the regulation of anthocyanine biosynthesis and GmUFGT is a key biosynthesis gene in mangosteen pigmentation. In fruits treated with 1-MCP the color development was delayed, suggesting the role of ethylene in the induction of GmMYB10 expression. The data generated in this work clearly suggest the importance of the transcription factor MYB and the enzyme UFGT in the color development of mangosteen fruit (Palapol et al., 2009).

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9.19

Postharvest biology and technology of tropical and subtropical fruits

Melon (Cucumis melo L.)

In melon somatic embryogenesis from cell suspension cultures was reported long ago (Oridate and Oosawa, 1986). Since then, the successful induction of somatic embryos has been carried out from cotyledons of mature seeds, hypocotyls of seedlings as well as leaves and petioles of young plantlets (Tabei et al., 1991). By then, the creation of transgenic plants expressing the enzymes β-glucuronidase, dihydrofolate reductase and neomycin phosphotransferase under the CaMV35S promoter had already been reported (Dong et al., 1991). Later, other protocols have been developed to create transgenic melon (Guis et al., 2000). Moreover, the finding of a genotype with optimal characteristics for manipulation and transformation was reported (Galperin et al., 2003) and a more efficient Agrobacterium mediated creation of transgenic melon that includes embryogenesis from cotyledon and hypotocyls explants was also obtained (Akasaka-Kennedy et al., 2004). The development of protocols to create transgenic melon plants is still an active line of research and the utilization of cotyledon, hypocotyl and true-leaf explants from both female and male parental lines of Galia melon has been reported (Nunez-Palenius et al., 2007a). However, the manipulation of melon in vitro is still not easy and, for unknown reasons, the organogenesis and somatic embryogenesis cannot be applied to all melon genotypes; thus, it has to be done for every genotype on an individual basis. Therefore, the utilization of DNA recombinant technology is considered a good choice to improve the melon fruit characteristics (Nunez-Palenius et al., 2008). There are two reviews on the subject of manipulation in vitro of melon explants and protocols to create transgenic melon plants (Li et al., 2006; Nunez-Palenius et al., 2008). Fruit firmness is an important quality characteristic; however, in melon fruit controversy exists as to whether the PG enzyme plays an important role in this parameter. In this context, three cDNAs with significant homology to other genes encoding polygalacturonases were cloned from melon fruit ripening, MPG1 (GenBank AF062465), MPG2 (GenBank AF062466) and MPG3 (GenBank AF062467). The expression levels of three polygalacturonase genes were high during fruit ripening. MPG1 mRNA was accumulated at higher levels and for a longer period of time during fruit ripening (Hadfield et al., 1998). Carbohydrate composition in fruits is important to define their final quality in the market. Although melon fruit has not been found to accumulate large amounts of starch (Hubbard et al., 1989), expression analysis of three cDNAs encoding one small subunit and two large subunits of ADP-glucose pyrophosphorylase, an enzyme playing a role in starch biosynthesis, were found to be highly active at the beginning of the melon fruit ripening (Park et al., 1998). This finding must be related to the small amount of starch present at the beginning of ripening in some cultivars of melon fruit (Hubard et al., 1989). Melon fruit during ripening accumulate stachyose and raffinose that are galactosyl-sucrose containing oligosaccharides (Gao et al., 2002). The enzyme α-galactosidase initiates the degradation of the oligosaccharides mentioned by removing the terminal α-galactosyl residue. Two cDNAs CmAGA1 and CmAGA2 were cloned from

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ripening melon fruit with high homology with genes encoding α-galactosidase enzymes. Expression of the proteins encoded in CmAGA1 and CmAGA2 was carried out in E. coli and allowed confirmation of their identity using several substrates in which various monosaccharides are covalently joined to the p-nitrophenyl (Carmi et al., 2003). Fruit softening is an important quality characteristic for melon fruits; however, there are some cultivars that soften quickly, reducing the postharvest shelf life of the fruit. It has been found that softening in melon fruits is ethylene dependent (Nishiyama et al., 2007). Because of that, attempts have been made to reduce the rate of softening in melon by reducing ethylene biosynthesis. Melon cultivar ‘Galia’ was transformed with the gene CmACO1 encoding 1-aminocyclopropane1-carboxylate oxidase (ACC) in antisense orientation. The transgenic melons showed firmness levels about twice those of the wild type and a delay in the softening advance (Nunez-Palenius et al., 2007b). Besides the reduction in the ethylene biosynthesis, the researchers also found a reduction in the general advance of fruit ripening and an increase in the polyamine putrescine and abscisic acid in a transgenic melon cultivar ‘Vedrantais’ expressing CmACO1 in antisense direction. The increase in polyamines was eliminated by ethylene treatments (Martinez-Madrid et al., 2002). Promoter analysis of the melon CmACO1 gene in transgenic tobacco has revealed the presence of an ethylene responsive element (Bouquin et al., 1997). Analysis of gene expression during ripening of transgenic melon fruit expressing CmACO1 in antisense has identified genes responsive and genes not responsive to ethylene, and also genes regulated by other developmental factors suggesting that ethylene is not the only factor controlling melon fruit ripening (Hadfield et al., 2000). Two ethylene receptor genes were isolated and are similar to the Arabidopsis ethylene receptors ETR1 and ERS1; they were named CmETR1 (GenBank AB052228) and CmERS1 (GenBank AB049128). Expression analysis of both transcripts during fruit development was carried out and CmERS1 was slightly active in the pericarp before the large expression of CmETR1 in response to ethylene production, suggesting that the two receptors play a different role in two different stages of fruit development (Sato-Nara et al., 1999). The aroma in fruits is a very important quality characteristic and in melon some of the genes playing a role in aroma have been cloned and studied. Four genes encoding enzymes with activity of alcohol acyl transferase, important in aroma development, were cloned from melon. Although no transgenic plants were created, the four genes CmAAT1 (GenBank AB075227), CmAAT2 (GenBank AB104414), CmAAT3 (GenBank AB109053) and CmAAT4 (GenBank AY859054) were expressed in yeast and studied. The gene products with the exception of AAT2 did not show activity. Furthermore, AAT1 generated a range of short- and long-chain acyl esters although with a tendency to produce E-2-hexenyl acetate and hexyl hexanoate. Moreover, AAT3 notably produced benzyl acetate whereas AAT4 showed a strong tendency to generate cinnamoyl acetate (El-Sharkawy et al., 2005). The products of carotenoids hydrolysis have been found to be part of

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the melon fruit aroma. In this regard, the gene encoding a dioxygenase able to hydrolyze the β-carotene in the position 9,10 producing β-ionone was cloned, expressed in E. coli and analyzed. The recombinant dioxygenase produced geranylacetone from phytoene, alpha-ionone and pseudoionone from deltacarotene, pseudoionone from lycopene and beta-ionone from beta-carotene. The gene was expressed during fruit development (Ibdah et al., 2006). The aroma of melon fruit also includes products derived from the catabolism of amino acids and transamination reactions. Two clones CmARAT and CmBCAT1 were identified in the melon EST database (http://www.icugi.org/) and the encoded proteins were produced in E. coli. Analysis of the enzymatic activity of the recombinant proteins showed that they were able to convert L-isoleucine, L-leucine, L-valine, L-methionine or L-phenylalanine into their respective α-keto acids, using the alphaketoglutarate as the amine acceptor. Both genes were highly expressed in ripening fruit showing their role in melon fruit aroma development (Gonda et al., 2010). Besides the above mentioned, alcohol dehydrogenases also play a role in aroma development by synthesizing substrates to be used in the synthesis of ester molecules. Two cDNAs CmADH1 (GenBank DQ288986) and CmADH2 (GenBank DQ288987) encoding alcohol dehydrogenases from melon fruit var. ‘Cantalupensis’ were cloned, and expression analysis showed that both genes are up-regulated during melon fruit ripening. ADH1 and ADH2 were overexpressed in yeast and recombinant proteins were shown to have alcohol dehydrogenase activity (Manriquez et al., 2006). In agreement with this, it has been demonstrated that ethylene plays an important role in the biosynthesis of some of the aroma volatiles in melon fruit (Flores et al., 2002). In the future, the knowledge of the genes playing a role in melon aroma development will allow the improvement of this important quality characteristic. The dbEST has deposited 6921 ESTs from C. melo subsp. Agrestis and 5943 ESTs from C. melo muskmelon by release 052110.

9.20

Nuts

9.20.1 Brazil nut (Bertholletia excelsa HBK, Lecythidaceae) In the case of the brazil nut, to our knowledge neither transgenic plants nor successful protocols for somatic embryogenesis have been reported until now. However, several efforts have been made to improve the nutritional quality of legume proteins by the introduction of cDNAs encoding rich methionine proteins of brazil nut. Indeed, there have been reports of the introduction of the cDNA pBN2S1 encoding the 2S albumin protein in Brassica napus (Guerche et al., 1990), canola (Altenbach et al., 1992), the tropical forage legume Stylosanthes guianensis (Quecini et al., 2006), in the bean Phaseolus vulgaris (Aragão et al., 1992; Aragão et al., 1996; Aragão et al., 1999), potato (Tu et al., 1998), in the grain legume Vicia narbonensis (Pickardt et al., 1995; Saalbach et al., 1995), and in Nicotiana tabacum (Saalbach et al., 1994). Also, in an effort to increase the amount of methionine in legumes, a chimeric gene was designed by ligation of part of the sequence of the Arabidopsis 2S albumin gene 1 (At2S1) at different places into a brazil nut 2S

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albumin cDNA clone sequence pBN2S1. The chimeric gene was introduced in Arabidopsis, tobacco (Nicotiana tabacum) and Brassica napus (De Clercq et al., 1990). Although it was possible to increase the amount of the amino acid methionine in legumes and to increase the quality of the legume protein as a consequence, unfortunately, the 2S albumin protein was shown to have the potential to be allergenic (Teuber et al., 1998). Therefore, this approach created a food with probable negative consequences for human health and that suggested the necessity to test the possible allergenic effects as one of the important side effects of the consumption of genetically modified foods (Lack, 2002). 9.20.2

Cashew apple and nut (Anacardim occidentale L., syn. Anacardium curatellifolium A. st. Hil) In the case of cashew apple and nut there are no available protocols to create transgenic plants; however, organogenesis and embryogenesis protocols have been developed in this specie. In the case of organogenesis, shoot induction was carried out using as explants, axillary bud sections of plants with an age between six months and one year. It was found that the combination of fructose and maltose was the best treatment recording the largest percentage of shoots with the greatest shoot length (Gemas and Bessa, 2006). Shoot induction was also carried out from cotyledons explants excised from Anacardim occidentale L. mature embryos (Ananthakrishnan et al., 2002). On the other hand, somatic embryogenesis has been successfully carried out from callus induced from nucellar tissue (Ananthakrishnan et al., 1999; Gogte and Nadgauda, 2000; Cardoza and D’Souza, 2002). Furthermore, this protocol has been tested successfully in several cultivars, including ‘Goa 11/6’, ‘Kanaka’ and ‘Ulla1-3’ (Anil and Thimmappaiah, 2005). Besides nucellar tissue, somatic embryogenesis has also been induced from seed coat explants (Martin, 2003) and immature zygotic embryos (Gogate and Nadgauda, 2003). From the above, it seems that the stage is set for the first attempt to introduce specific genes in this specie to improve the postharvest fruit quality. 9.20.3 Macadamia (Macadamia integrifolia, macadamia tetraphylla) In macadamia there are no reports of the creation of transgenic plants or somatic embryogenesis. However, protocols for organogenesis have been developed in both species. In the case of M. tetraphylla, the induction of shoot regeneration from immature cotyledon explants has been reported (Mulwa and Bhalla, 2006), as well as from node segments excised from plants two years old and from four month old seedlings (Mulwa and Bhalla, 2000). However, the induction of roots from macadamia shoots has been difficult and a protocol to obtain a whole plant is not yet available (Gitonga et al., 2008). Macadamia contains an unusually large amount of monounsaturated fatty acids of relatively low molecular weight (Kaijser et al., 2000) and the consumption of this nut has been found to have positive effects on the plasma lipid profile in persons with high levels of cholesterol in the blood (Garg et al., 2003) and to reduce the risk of coronary artery disease (Garg

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et al., 2007) which is an important quality characteristic of this fruit. Because of this, a study was undertaken to isolate the cDNAs encoding the acyl–acyl carrier protein desaturase playing a putative role in the biosynthesis of monounsaturated fatty acids (Gummeson et al., 2000). Several cDNAs were isolated from developing nut seeds and one of them was expressed in E. coli. Unfortunately, analysis of the desaturase showed a preferential activity for fatty acids with 18 carbons and not 16 carbons, suggesting that this enzyme is not the one responsible for the large amount of monounsaturated fatty acids with 16 carbons characteristics of macadamia oil. It will be interesting to isolate and study the desaturases playing a role in the biosynthesis of the low molecular monounsaturated fatty acids in macadamia to use in the quality improvement of other tropical fruits. A low molecular weight antimicrobial peptide AMP1, encoded in MiAMP1, was originally isolated from the kernel of M. integrifolia and was also found to be present in other plant species (Manners, 2009). MiAMP1 was cloned and expressed in E. coli (Harrison et al., 1999) and the recombinant AMP1 inhibited 14 phytopathogenic fungi such as A. helianthi, B. cinerea, C. paradoxa, C. falcatum, C. gloeosporioides, F. oxysporum, L. maculans, M. phaseolina, P. cryptogea, P. graminicola, S. sclerotiorum, S. rolfsii, V. dahliae and A. fumigatus in vitro. AMP1 also inhibited the growth of phytopathogenic bacteria C. michiganensis and P. rubrilineans (Marcus et al., 1997). Because of this, the potential utilization of AMP1 to increase the resistance of many transgenic crops has already been proposed (Kazan et al., 2002a). The construct including the MiAMP1 cDNA under the control of the CaMV35S was introduced in tobacco and canola (Brassica napus L.). The AMP1 protein obtained from the leaves of the transgenic plants was able to inhibit several phytopathogenic fungi in vitro. Furthermore, cotyledons from seven independently transformed canola plants inoculated with Leptosphaeria maculans, the causal agent of blackleg disease, showed a lower lesion development as compared with the isogenic lines and an azygous plant, from the segregating progeny of a transgenic canola plant (Kazan, et al., 2002b). Clearly, the antimicrobial macadamia peptide deserves further research to explore the possibility of increasing the biotic stress resistance of many highly susceptible tropical fruits. 9.20.4 Pistachio (Pistacia vera L.) In pistachio the improvement of the existing cultivars has been very difficult because of the large degree of heterozygosity and low amount of regenerated good quality plant material (Onay, 2005), as well as the genetic erosion of the Pistacia germplasm (Ozden-Tokatli et al., 2010). In this context, plant biotechnology has to be utilized and in fact it seems to be the only option. Although there are no protocols to create pistachio transgenic plants, successful organogenesis and somatic embryogenesis have been reported for this specie. Indeed, somatic embryogenic has been carried out from kernels derived from immature fruit (Onay et al., 1995) and a protocol to store these embryos for a short time using calcium alginate gel has been reported (Onay et al., 1996). In this work, it was found that embryos could be recovered after 60 days of storage at 4°C. Furthermore, the same protocol

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has been tested successfully in several pistachio cultivars already (Onay et al., 2007a). Besides that, somatic embryogenesis has been also successfully done with callus tissue derived from mature zygotic embryos of pistachio (Onay et al., 2007b) and from female flower buds with a size between 5 and 8 mm harvested two weeks before pollination (Onay et al., 2004). Besides somatic embryogenesis, an efficient protocol for Pistachio organogenesis using in vitro regenerated leaves explants developed from mature shoot tips obtained from a 30 year old tree was also reported (Tilkat and Onay, 2009). As can be seen, the first step toward the utilization of tools derived from the DNA recombinant technology has been taken in this specie. Therefore, we will see in the near future efforts to create transgenic plants harboring specific genes for quality improvement in this specie; up to now there are 1299 ESTs deposited at the dbEST release 052110.

9.21

Olive (Olea europaea L.)

In olive protocols for organogenesis, somatic embryogenesis and creation of transgenic plants have already been developed. In fact, there are several published works reviewing these biotechnological tools (Rugini et al., 2005; Rugini and Pesce, 2006; Fabbri et al., 2009). Olive organogenesis has been carried out from petioles (Mencuccini and Rugini, 1993), from shoot apical bud excised of an olive tree growing in the field (Zacchini and De Agazio, 2004), from nodes located at different places in olive plants growing in the greenhouse (Otero and Docampo, 1998) or in the field (Cozza et al., 1997). On the other hand, somatic embryogenesis has been carried out from several explants, such as immature zygotic embryos at different stages of development (Rugini, 1988), petiole tissue or callus induced from petiole tissue (Rugini and Caricato, 1995), callus tissue induced from cotyledon fragments (Trabelsi et al., 2003; Brhadda et al., 2008) and leaf tissue explants (Lopes et al., 2009). It is important to mention that in olive, secondary embryogenesis is not yet completely developed to obtain healthy plants (Rugini et al., 2005). The first attempts to create transgenic plants in olive were made in 1984 using A. tumefaciens mediated transformation. There is a reported attempt to introduce the genes rolA, rolB and rolC of A. rhizogenes with the aim of increasing the capacity of the explants to produce adventitious roots. Although most of the roots produced were not transformed, an increase in root number was observed (Fabbri et al., 2009). Utilization of microprojectile bombardment in somatic embryos was able to get transient expression of the β-glucuronidase gene under the control of the CaMV35S promoter (Lambardi et al., 1999). An improvement in the microprojectile bombardment protocol was made by the utilization of a construct in which the β-glucuronidase gene was under the control of the ubiquitin promoter from sunflower. In this case, a much higher frequency of gus expression sites per bombarded tissue was recorded (Perez-Barranco et al., 2009). On the other hand, Agrobacterium infection of olive somatic tissues was able to introduce in the olive genome the genes rolA, rolB and rolC from Agrobacterium rhizogenes as shown by Southern blot (Mencuccini et al., 1999). Later, a protocol for developing transgenic plants using

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Agrobacterium infection of somatic embryos was able to develop transgenic olive plants expressing the β-glucuronidase gene (Torreblanca et al., 2009). A transgenic olive plant was created expressing the osmotin gene from tobacco (Nicotiana tabacum) under the control of the CaMV35S promoter. Although it was not the objective of the experiment, it is quite possible that overexpression of osmotin would increase the resistance of the fruit to attack by fungi (D’Angeli and Altamura, 2007). Although analysis was not made in fruit, an increased resistance of the transgenic olive plant to the olive leaf spot caused by Phytophthora crown was observed (Fabbri et al., 2009). Moreover, in order to facilitate the harvest of olive fruit, it has been suggested that it may be possible to create a transgenic olive plant expressing a construct in which the ACC synthase gene is under the control of the promoter from chalcone synthase, anthocyanidin synthase and expansin genes from olive. This is because these genes showed the highest activity during the latest stage of olive fruit development (Ferrante et al., 2004). However, still more experimental work is needed in this direction. Olive oil is an important quality characteristic of olive fruit and its consumption has been shown to bring positive benefits to human health (La Lastra et al., 2001). Several genes related to the biosynthesis of the different components of the olive oil have been cloned and studied. Two cDNAs, OeFAD2 (GenBank AY733076) and OeFAD6 (GenBank AY733075), that encode omega-6 fatty acid desaturases, responsible for synthesizing linoleic from oleic acid were isolated. Analysis of gene expression showed that OeFAD2 presents the maximum expression in mesocarp of the olive fruit, suggesting an important role in lipid storage (Banilas et al., 2005). Further research in those genes showed that most likely FAD2 is the enzyme responsible for the linoleic acid content in olive fruit mesocarp tissue (Hernandez et al., 2009). In a related work, two oleate desaturases encoded in OeFAD2-1 and OepFAD2-2 (GenBank AY733076) were isolated and studied. Analysis of their expression showed that OeFAD2-2 was present during the development of seeds and during the ripening of the mesocarp, suggesting an important role for the encoded enzyme in the storage of oil in the mesocarp of the mature fruit (Hernandez et al., 2005). Desaturases need the presence of an electron donor to carry out their activity. In this context, two cDNAs, OeCYTB5-1 (GenBank AJ001369) and OeCYTB5-2 (GenBank AJ001370), encoding cytochromes b5 were cloned and studied. These cytochromes seem to be involved, among other things, in providing redox potential to desaturases enzymes (Martsinkovskaya et al., 1999). The aroma of olive oil is an important quality characteristic and it is known that lipoxygenase is an enzyme involved in aroma development. Two cDNAs, OeLOX2-1 (GenBank EU513352) and OepLOX2-2 (GenBank EU513353), encoding lipoxygenases were cloned and overexpressed (Padilla et al., 2009). The recombinant enzymes LOX2-1 and LOX2-2 were able to synthesize 13-hydroperoxides from linoleic and linolenic acids. Furthermore, both enzymes were expressed in mesocarp and seed during development and ripening of olive fruit. Altogether, biochemical and gene expression data suggested that both enzymes are involved in the development of the characteristic aroma of olive oil. In a related work, a cDNA OeLOX1 (GenBank EU678670) encoding a

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lipoxygenase able to synthesize 9 and 13-hydroperoxides from linoleic acid was isolated and studied. Gene OeLOX1 was expressed mainly during the late stages of olive fruit development. Although it was suggested that this enzyme plays a role in ripening and senescence of olive fruit, its putative role in aroma development deserves further research (Palmieri-Thiers et al., 2009). Olive transcriptomes have been reported in the past years in an effort to gain insights into the genetic and molecular aspects controlling fruit development and ripening. A recent study reported the construction of suppression substractive hybridization libraries from three developmental stages of olive fruit: initial fruit set (30 days after flowering, DAF), complete pir hardening (90 DAF) and veraison (130 DAF) (Galla et al., 2009). The objective was to identify differentially expressed genes during the ontogeny of olive cv. ‘Leccino’, a widespread Italian variety showing a short fruit developmental cycle and a high degree of synchronization of processes defining ripening. A total of 1132 differentially expressed genes were identified and classified according to cellular compartment, molecular function and biological process. The most represented genes were for nucleotide binding proteins, followed by transport proteins, kinases and other enzymatic activities. The most represented genes according to cellular compartments were from plastids and mitochondria, followed by cytosol, plasma membrane, endoplasmic reticulum and nucleoplasm. With regard to biological processes, carbohydrate metabolism, response to biotic and environmental stresses, generation of precursors, metabolites and energy were the most represented genes. The less represented were genes related to the secondary metabolites, metabolism of lipids, synthesis of amino acids and derivatives, metabolites and their precursors, and protein modification process. The deposited sequences contributed to the public olive EST repertory. From the 1132 ESTs, 642 are unique sequences. Among these, 89 (14%) corresponded to 61 different key genes, and their expression was investigated. Quantitative realtime PCR experiments were done to evaluate the expression patterns of a subset of 61 different genes from the libraries (Galla et al., 2009). Genes involved in carbohydrate metabolism were modulated in their expression, genes related to starch metabolism were coherent with a temporary role of starch as a storage compound during early fruit development. Sequences of enzymes related to pentose pathway, glycolysis and gluconeogenesis as well as starch and sucrose metabolism were up-regulated. Genes involved in fatty acid biosynthesis are up-regulated throughout development; however, specific enzymes accumulate at a different extent depending on the developmental stage. Genes related to the phenylpropanoid and alkaloid biosynthesis and caffeine, limonene and pinene metabolism appeared to be differentially expressed throughout fruit development. Four enzymes controlling flavone and flavonol as well as anthocyanin biosynthesis were up-regulated from 90 to 130 DAF, therefore suggesting an increased accumulation of the related metabolites during late development. Genes for chalcone synthase, flavanone 3-hydroxylase, dihydroflavonol reductase and anthocyanidin synthase were up-regulated at veraison stage (Galla et al., 2009). The first large scale information about structural and putative function of gene transcripts during olive development was also reported in 2009 (Alagna et al.,

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2009). The objective of that work was to identify EST involved in phenolic and lipid metabolism during fruit development. The technique 454 pyrosequencing was used to sequence four cDNA libraries from olive (Olea europea) cv. ‘Coratina’ (a high phenolic content) and ‘Tendellone’ (a natural variant lacking oleurepein), and obtained a set of 261 485 ESTs to identify genes involved in expression of fruit quality traits, fruit metabolism and phenolic content during ripening. A comparative EST analysis was performed and provided more than 102 000 unigenes, after clustering consisting in 26 576 consensus sequences from clusters (TCs) or contigs and 75 570 singletons from the four libraries (Alagna et al., 2009). The authors discussed a possible overestimate of the unigene set of Olea since short reads are obtained by the 454 pyrosequencing technology. The short reads result in unassembled segments of TCs and EST pertaining to the same transcript unit. Expression differences between the fruit developmental stages were found. For example, TCs predicted to be related to photosynthesis (photoreception, Calvin cycle and oxidative phosporylation) were more represented at 45 DAF. On the other hand, transcripts associated with carbohydrate metabolism (glycolisis/ gluconeogenesis, citrate cycle, fructose, mannose and galactose metabolism) were more represented at 135 DAF (Alagna et al., 2009). The EST database was also compared between the C and T genotypes. There were TCs specific for cv. ‘Coratina’ and some specific for cv. ‘Tendellone’. These TCs encode proteins involved in hormone catabolism and regulation, abiotic and biotic stress, cell wall metabolism, lipid metabolism, steroid metabolism and phenylpropanoid metabolism. Several transcripts involved in the biosynthesis of steroids with nutritional and health benefits were reported exclusively in ‘Coratina’. Two TCs specific to ‘Coratina’, encode R-limonene synthase 1 and 1,8-cineole synthase, which are related to the biosynthesis of important flavor compounds such as (+)-R-limonene, a monocyclic monoterpene and 1,8-cineole or eucalyptol, a monoterpenic oxide present in many essential oils (Alagna et al., 2009).

9.22

Papaya (Carica papaya L.)

Transgenic papaya plants were first produced by microprojectile bombardment transformation of three different tissues: immature zygotic embryos, hypocotyl sections immediately after being dissected and mature somatic embryos. The introduced genes were nptII (conferring resistance to kanamycin) and uidA (encoding β-glucuronidase) (Fitch et al., 1990). It seems that the event in 1992, when the papaya ringspot virus nearly destroyed all of the papaya fields in the Puna district of Hawaii (Ferreira et al., 2002) and the lack of a natural resistance trait in the commercial papaya cultivars, induced an intensive research to develop efficient techniques to create transgenic plants. Also, efficient protocols for papaya somatic embryogenesis from immature zygotic embryos were already available (Fitch and Manshardt, 1990). Indeed, in 1992 the creation was reported of transgenic papaya plants by microprojectile bombardment expressing the papaya ringspot virus coat protein as well as the nptII and uidA genes. It was reported that

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at least one transgenic line created was completely resistant to virus infection (Fitch et al., 1992). After that, the successful creation of transgenic plants expressing the same construct just mentioned by Agrobacterium mediated transformation of somatic embryos was reported (Fitch et al., 1993). Innovation of the Agrobacterium protocol was made by using as explants petioles from shoots micropropagated in vitro (Yang et al., 1996), and wounding of somatic embryos with carborundum prior to Agrobacterium infection (Cheng et al., 1996). On the other hand, several innovations in the microprojectile bombardment protocol were made by the utilization of a thin layer of somatic tissue developed from immature somatic embryos (Cai et al., 1999). Utilization of the gene PMI encoding the enzyme phosphomannose isomerase (Zhu et al., 2005) and the green fluorescent protein (Zhu et al., 2004a) instead of antibiotics to select for transgenic tissues was a good effort to avoid the concerns related to the presence of antibiotic resistance genes in the genome of transgenic plants (Kuiper et al., 2001). The strategy of introducing the gene encoding a coat protein of the ring spot virus mentioned above could induce complete resistance to papaya according to evaluations carried out in Hawaii (Tripathi et al., 2008), Jamaica (Tennant et al., 2002; Tennant et al., 2005), Taiwan (Bau et al., 2003), Australia (Lines et al., 2002) and Venezuela (Fermin et al., 2004). Analysis of the molecular basis of the resistance has found that virus suppression takes place by post-transcriptional gene silencing and mRNA degradation (Lines et al., 2002), although the virus is able to overcome the defense mechanism after a few generations (Ruanjan et al., 2007). The phenomenon of post-transcriptional gene silencing requires homology between the transgene RNA and viral RNA (Baulcombe, 1996). Furthermore, it has been found that the differences between the sequence of the transgene being expressed by the papaya fruit and the sequence of the infecting virus can affect the level of resistance of the transgenic papaya fruit (Souza and Gonsalves, 2005). As a consequence of this, the creation of transgenic papaya expressing local varieties of ring spot virus showed higher levels of resistance as compared to the utilization of genes expressing the coat protein from virus isolated in other parts of the world (Fermin et al., 2004). Besides the utilization of the gene encoding the coat protein of the virus, another approach was made by introducing a 3 ‘truncated and 5’ fragment of the gene RP encoding the enzyme replicase from the papaya ringspot virus under the control of the CaMV35S. A good level of resistance was found in several lines of transgenic papaya plants (Chen et al., 2001). The ripening phenomena of fruits initiated by ethylene affects the postharvest shelf life in optimal conditions. In papaya, the cDNAs for key enzymes of the biosynthetic pathway of ethylene, ACC synthase (Hidalgo et al., 2005) and ACC oxidase were cloned (Chen et al., 2003). The nucleotide sequence of one of these cDNAs was used to design transgenic papaya fruits that produce reduced levels of ethylene. A chimeric construct containing a truncated piece of the gene encoding the ACC oxidase enzyme under the control of the CaMV35S promoter was introduced into papaya by particle bombardment. Analysis of the transgenic fruits revealed a large reduction in ethylene production and respiration rate, and a delay in the ripening rate of papaya fruits was

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also observed. It seems that the utilization of this approach has a good potential to increase the postharvest shelf life of papaya fruit (Lopez-Gomez et al., 2009). Papaya is a tropical fruit and therefore it is susceptible to chilling injury which causes postharvest papaya losses (Chen and Paull, 1986). To increase the resistance of papaya fruit to low temperatures, two genes (CBF1 and CBF3) encoding one of the C-repeat binding factors, known to induce genes for cold acclimatizing, were introduced into papaya. Transgenic plants were shown to have the transgene by Southern blot. Although the response of the fruit to low temperatures was not tested, it was a good approach to reduce the postharvest papaya losses by low temperature stress (Dhekney et al., 2007). Attack by fungi is one of the most important biotic stresses of postharvest fruit losses in the world. In the case of papaya, Phytophthora palmivora can infect both plant and fruit tissues. In order to increase the resistance of papaya to P. palmivora attack, a construct containing the gene DmAMP1 (GenBank A26963) encoding a defensin from Dahlia merckii was introduced into the papaya genome. A leaf extract of the transgenic papaya was able to inhibit the growth of P. palmivora in vitro. Also, plants infected by P. palmivora were better able to suppress the hyphae growth and to reduce the infection advance (Zhu et al., 2007). Another approach to increase the resistance of papaya to P. palmivora was to introduce into the papaya genome a construct designed to express the cDNA VvVST1 (GenBank XM002263926) encoding the enzyme stilbene synthase, which catalyzes the synthesis of the phytoalexin resveratrol that has been found to inhibit the fungi growth in vitro. The expression of the transgene was found in response to the fungi infection as expected. Also, the resistance of the fruit was not tested; however, an increased resistance to the fungi infection in several transgenic lines was reported (Zhou et al., 2004b). Color is an important quality characteristic in fruits. In papaya, there are some cultivars with red and yellow pulp. Two genes encoding the lycopene β-cyclase enzymes that catalyze the transformation of lycopene into β-carotene from the red cultivar ‘Tainung’ and the yellow cultivar ‘Hybrid 1B’ were cloned and designated lcy-beta1 and lcy-beta2. Analysis of the nucleotide sequences of lcy-beta1 and lcy-beta2 revealed a mutation consisting of a TT insertion at position 881 that induces a premature stop codon in the lcy-beta2 gene. Therefore, there is no conversion of lycopene into β-carotene, and the color of the papaya flesh is red. The analysis of gene lcy-beta2 in several cultivars with red flesh also showed the presence of the same mutation (Devitt et al., 2010). Due to the fact that there is one gene related to the phenotype of flesh color in papaya fruit, it will be relatively easy to design a strategy to create transgenic papaya fruit with a specific color. The potential utilization of papaya to develop fruit based vaccine was shown by the creation of a transgenic papaya expressing synthetic epitopes designed to induce an immunogenic response against the porcine Taenia solium cysticercosis. The soluble extracts of clones were shown to induce immunity against cysticercosis in 90% of the fed mice tested (Hernández et al., 2007). This is a good approach to improve the quality of the fruit by having a positive effect on the consumer. The first commercial virus-resistant transgenic fruit tree to be sequenced is the ‘SunUp’ papaya. With a size of 372 Mb, it is three times the size of the Arabidopsis

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genome; however, it contains fewer genes including significantly fewer diseaseresistance gene analogues. This genome sequence gives an opportunity to reveal the basis of Carica’s distinguishing morpho-physiological, medicinal and nutritional properties (Ming et al., 2008). A study of papaya ESTs associated with fruit ripening was reported in 2006 (Devitt et al., 2006). A total of 1171 ESTs were generated from two cDNA libraries made from yellow- and red-flesh fruit varieties. The ESTs produced 117 contigs and 710 singletons. The EST sequences encode genes involved in fruit softening such as cell wall hydrolases, pectinmethyl esterase, beta-1, 3-glucanase, polygalacturonase-like protein, beta-glucosidase, polygalacturonase and betagalactosidase precursor that had not been reported from papaya (Devitt et al., 2006). Softening in papaya is a major issue because it is very rapid and affects shelf life, and therefore the availability of sequences of enzymes related to this parameter will be useful for future work aiming to maintain firm fruits. Sequences showing similarity to enzymes associated with fruit volatile biosynthesis were uncovered also. Between them the genes of the isoprenoid biosynthesis, shikimic acid pathway such as the cinnamate-4-hydrolase (C4H) were identified. Fatty acid derived volatiles are contributors to aroma and enzymes related to acyl lipid catabolism pathway. Two ESTs related to putative enzymes of peroxisomal fatty acid betaoxidation were identified and encode the final two steps of fatty acid degradation to acetyl-coenzyme A, AIM1 and 3-ketoacyl-CoA thiolase (Devitt et al., 2006).

9.23

Passion fruit (Passiflora edulis Sim)

There are no protocols available for the creation of transgenic passion fruit plants. Although no protocols for somatic embryogenesis have been reported, protocols for organogenesis have been published (Vaz et al., 1993; Pinto et al., 2010). Also, there is a review of biotechnological aspects of several species belonging to the genus Passiflora (Vieira and Carneiro, 2005). Analysis of the expression of three cDNAs, PeETR1 (GenBank AB015496), PeERS1 (GenBank AB015497) and PeERS2 (GenBank AB070652) encoding ethylene receptors in passion fruit showed differential expression. Only PeERS2 was induced by ethylene during fruit ripening. Treatment with norboradiene, a reversible inhibitor of ethylene action, induced a reduction in PeERS2 mRNA levels in the aril of the fruit; however, ethylene treatment eliminates this effect, suggesting the importance of PeERS2 in controlling fruit ripening (Mita et al., 2002). In a related work (Mita et al., 1998), the expression of two ACC synthase encoding genes, PeACS1 (GenBank AB015494) and PeACS2 (GenBank AB015495), one ACC oxidase encoding gene, PeACO1 (GenBank AB015493) and two ethylene receptors PeETR1 and PeERS1 were studied. Higher levels of PeACS1 mRNA and PeACO1 mRNA were detected in arils compared to the levels accumulated in seeds and these results agree with the larger production of ethylene that has been observed in the plant. PeETR1 and PeERS1 mRNA levels did not change during the course of ripening. This data strongly suggests the importance of

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the genes PeACS1 and PeACO1 to carry out the biosynthesis of ethylene during passion fruit ripening. In addition, these results clearly suggest the procedure to follow in order to create transgenic passion fruit with low levels of ethylene by inhibition of the enzymes playing a role in the ethylene biosynthetic pathway.

9.24 Pineapple (Ananas comosus L. Merr) In pineapple, creation of plantlets by organogenesis has been available for quite some time (Mathews and Rangan, 1979). Also, protocols for pineapple embryogenesis have been published (Sripaoraya et al., 2003; Firoozabady and Moy, 2004). Efficient protocols for the creation of pineapple transgenic plants by microprojectile bombardment (Sripaoraya et al., 2001; Sripaoraya et al., 2006) and Agrobacterium infection using different explants are also available (Firoozabady et al., 2006; Wang et al., 2009). Pineapple fruit is also susceptible to fungi infection (Rohrbach and Pfeiffer, 1976); therefore, transgenic plants resistant to fungi are desirable. On the other hand, magainin peptides have been shown to have broad spectra of antimicrobial activity in fruits (Matsuzaki et al., 1997). Transgenic pineapple plants were created by introducing the magainin analog, MSI99, in order to increase the resistance of pineapple fruit to fungi attack (Mhatre et al., 2009). Although pineapple fruits from the transgenic plants were not analyzed, the possibility that these fruits will have higher resistance to fungi attack is not discarded. In a related work (Yabor et al., 2006), transgenic plants expressing the Phaseolus vulgaris chitinase class-I gene under the control of the chimeric promoter OCS-35S CaMV-rice actin I and the tobacco (Nicotiana tabacum) AP24 gene, encoding a wide spectrum antifungal protein, were created to increase the resistance of pineapple to Phytophthora nicotianae var. parasitica attack. A construct in which the bar gene is under the control of the maize ubiquitin 1 promoter was also introduced. The bar gene encodes the protein phosphinotricin acetyltransferase conferring resistance to the herbicide phosphinotricin. In the transgenic plants analysis of the biochemical changes due to the transformation was carried out (Yabor et al., 2006). Furthermore, biochemical effects of the herbicide treatment (Yabor et al., 2008) as well as changes in phenotype and enzymatic activity in the herbicide treated transgenic plants growing in the field were analyzed (Yabor et al., 2010). Although the resistance to the fungi attack during the postharvest shelf life of the transgenic pineapple fruit was not evaluated, the experimental approach clearly showed the current state of the art of the biotechnological tools to improve the resistance to biotic stress in pineapple fruit. Blackheart is a physiological disorder that reduces the quality of pineapple fruit and increases the postharvest fruit losses (Smith and Glennie, 1987). This disorder is thought to be induced by low temperature storage (Nanayakkara et al., 2005) and polyphenol oxidase activity (Stewart et al., 2001; Zhou et al., 2003a). Two genes AcPPO1 (GenBank AY149880) and AcPPO2 (GenBank AY149881) encoding polyphenol oxidase enzymes were isolated from pineapple (Zhou et al., 2003b).

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Analysis of the expression of a construct in which the promoter from AcPPO1was driving the expression of β-glucuronidase showed that this promoter is wound and cold inducible, in agreement with the conditions known to induce the blackheart physiological disorder. Furthermore, giberellin responsive elements were found in the promoter and indeed, the mutation of the elements induced a delay in the promoter response to the giberellic treatment. Treatment with giberellic acid also induces the blackheart disorder in the absence of low temperatures stress, further suggesting the role of polyphenol oxidase enzyme in blackheart disorder development. In a related work (Ko et al., 2006), a transgenic pineapple was created in which AcPPO1 was introduced in sense and antisense direction under the CaMV35S and maize ubiquitin-1 promoter. The integration of the transgene was probed by Southern blot and it is possible that the pineapple transgenic fruit will show a low incidence of the blackheart, even though the effects of the transgene in either AcPPO1 mRNA levels or polyphenol oxidase activity were not analyzed. The postharvest shelf life of fruits in optimal conditions is important during their exportation. The potential has already been shown of the alterations in the genes encoding the two key enzymes of ethylene biosynthesis: ACC synthase and ACC oxidase. Although pineapple is a non-climacteric fruit, the genes encoding the ACC synthase (AcACS1) and ACC oxidase (AcACO1, GenBank AY049052) were cloned. AcACS1 mRNA levels increased 16-fold in ripe tissue, compared with green tissue, while low levels of AcACO1 mRNA accumulated in ripening fruit tissue (Cazzonelli et al., 1998). The data generated in this work suggest that manipulation of the ethylene biosynthetic genes can be a good strategy to control the pineapple ripening phenomena. To our knowledge, there is only one report about reduced levels of AcACS2 (GenBank CS326585) in pineapple by co-suppression (Trusov and Botella, 2006). A delay in the flowering time of the transgenic pineapple plants was reported, but no analysis of the effect on pineapple fruit ripening was reported. However, careful analysis of the pineapple fruit ripening phenomena suggested that there were no effects on pineapple fruit ripening due to the gene silencing (José Ramón Botella, personal communication). A pineapple EST project was carried out during fruit ripening to develop a valuable molecular resource for pineapple technology (Moyle et al., 2005). Differential expression was determined between green unripe tissue and yellow ripe fruit tissue. A total of 480 unripe green pineapple and 1536 ripe yellow pineapple clones were sequenced. After raw sequences were edited and sequences of less than 150 bp were discarded, 408 green unripe and 1140 yellow ripe pineapple EST sequences with an average length of 785 bp were deposited in the GenBank dbEST. All edited sequences were clustered into 634 contigs. A metallothionein clone was the most abundant transcript in the amplified fruit cDNA pools and its expression was assessed by QRT-PCR; the expression of the metallothionein increased during fruit development and was highest in mature fruit. A second metallothionein gene was also discovered in the yellow fruit library and it is 80% identical to the other metallothionenin gene discovered in both libraries. Northern analysis was performed to validate the expression patterns of the most abundant EST species isolated in fruit

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tissue at different developmental stages. Both metallothionenin genes exhibited similar expression patterns across the range of pineapple fruits sampled and are similarly up-regulated in older leaves. Metallothionenins are small, cysteinrich proteins required for heavy metal tolerance in animals, fungi and plants. It is not yet clear why metallothioneins are up-regulated during fruit development, or how they function in plants (Moyle et al., 2005). Functional classification analysis of the rest of the clones was performed and ten per cent of unripe green and six per cent of ripe yellow clones encode proteins falling within cell rescue, defense and virulence major class. Unripe green and yellow pineapple fruits expressed a high proportion of oxidative stress-related proteins, supporting the view that ripening is an oxidative phenomenon requiring a balance between the production of ROS and their removal by antioxidant systems. Major differences between the genes expressed in unripe green and ripe yellow pineapple fruits and Northern analysis revealed that fruit bromelain and bromelain inhibitor gene found to be abundant in the green fruit library are downregulated during fruit ripening. Cinnamyl alcohol dehydrogenase (CAD) clones were isolated from both green and yellow fruit libraries, although they were more abundant in the green than in the yellow fruit. It has been suggested that CAD up-regulation plays a role in the interconversion of aldehydes and alcohols implicated in flavor as well as the lignification of vascular elements. A MADS box transcription factor homologue was the most abundant clone type in the yellow fruit library, while in the green fruit library putative PHD transcription factor clones were isolated. Northern analysis of the MADS box gene in developing pineapple fruit confirmed its increase during ripening and its abundance in yellow fruit. Many candidate genes for future analysis are available to build microarrays for the large-scale examination of gene expression over a range of fruit development (Moyle et al., 2005). The ESTs reported here are a valuable tool for future studies of ripening pineapple. Up to now there are 5659 ESTs deposited at the dbEST.

9.25

Sapodilla (Manilkara zapota)

In the case of the fruit sapodilla, no protocols for organogenesis, somatic embryogenesis or transgenic plants have been published. However, due to the fact that this fruit softens very quickly after harvesting (Qiuping et al., 2006), the possible role of expansin genes in the softening has been studied. The cDNAs for MzEXP1 (GenBank EU139436) and MzEXP2 (GenBank EU251387) encoding expansins were cloned and their expression was studied in the cultivars ‘Makok-Yai’ and ‘Kra-Suay’ (Kunyamee et al., 2008). The gene MzEXP1 was expressed during the early stages of fruit development, whereas MzEXP2 was present by the end of fruit development and a few days after harvesting in both cultivars. Treatment with ethylene reduced MzEXP2 mRNA levels, whereas treatment with 1-MCP induced its expression. This data suggest that ethylene negatively regulates MzEXP2 mRNA levels suggesting that both genes act at different stages of development inducing fruit softening.

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Other work reported the cloning of cDNAs for MzEG (EU819555) encoding endo-beta-1,4-glucanase, MzPL (EU819554) encoding pectate lyase and MzPG (EU139437) encoding polygalacturonase from sapodilla (Kunyamee et al., 2010). Expression levels of MzEG correlated with fruit growth and not with loss of fruit firmness after harvest. MzPL and MzPG accumulated during postharvest ripening. Levels of MzPG mRNA correlated with PG activity and decrease of fruit firmness; thus, PG has an important role in the rapid softening of sapodilla fruits.

9.26

Conclusions

Overall, the knowledge of the genetic and molecular basis of ripening, senescence, biosynthesis of bioactive compounds and the biochemical processes that occur in the fruit will result in benefits for the consumer and the producer. Consumer perceptions of modified fruits as (genetically modified organism) GMO may change upon the commercialization of fruits expressing vaccines or antigens. Those are the benefits that plant biotechnology must emphasize to interest groups. Also, the understanding of the recombination process in plants may lead to better and more precise transformation methods, that do not depend on illegitimate recombination, where it is possible that the plant has unknown effects, such as those claimed in transgenic soy with Bt toxin. Other basic biology processes such as DNA repair in plants (Liu et al., 2000) are less well known but are no less important, for example, if irradiation techniques are used to sterilize foods, or if UV-C is used to induce physiological responses. In all cases, investment in basic science will lead to advances that in the medium to long term, will benefit market and consumers.

9.27

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10 Fresh-cut tropical and subtropical fruit products G. A. Gonzalez-Aguilar, Research Center for Food and Development, Mexico, A. A. Kader, University of California, Davis, USA, J. K. Brecht, University of Florida, USA, and P. M. A. Toivonen, Agriculture and Agri-Food Canada, Canada

Abstract: Fresh-cut (FC) produce is one of the major growing segments in food retail establishments. However, FC tropical and subtropical fruits are still under study because of the difficulties in preserving their fresh-like quality for longer periods. This chapter covers different aspects of the FC industry which includes biochemical, physiological, microbiological, nutritional and quality changes in FC processing and storage and distinct equipment design, packaging requirements, production economics, marketing considerations and new trends for FC products. Aspects concerning specific conditions suggested for FC tropical and subtropical fruits in each one of the processing steps such as washing, sanitation, cutting, and dipping treatments, use of edible coatings alone or in conjunction with antioxidants and antimicrobials, and/or preservation under modified atmospheres, are thoroughly discussed. The chapter covers the most frequent causes of quality loss of FC tropical and subtropical products such as browning and other discolourations, softening, surface dehydration, water loss, translucency, off-flavour and off-odour development, as well as microbial spoilage and the techniques used to prevent or reduce these problems. Special attention is devoted to the new development of edible coatings that can be used as a complement or alternative to modified atmosphere packaging (MAP) or as carriers of controlled release systems that contain natural antioxidants and antimicrobials. Key words: fresh-cut produce, tropical fruit, subtropical fruit, quality, preservation, safety.

10.1

Fresh-cut produce industry worldwide

Fresh-cut (FC) fruit products are those that have been cleaned, peeled, sliced, cubed or otherwise prepared for convenient consumption, but which remain in a

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living, respiring physiological condition (Brecht et al., 2004). This is as opposed to minimally processed or lightly processed products, which are usually products that are retained in a ‘fresh-like’ (non-living) state by mild processing techniques that may include blanching, ultra-high-pressure treatment, or osmotic dehydration. The attractiveness and convenience of FC fruits and vegetables has led to increased sales and consumption of the available products, which in turn has led to attempts to develop and optimize the production of new FC products such as those made from subtropical and tropical fruits. Commercial FC vegetable products are more commonly produced and consumed than FC fruits due to seasonal and inconsistent supplies, shorter post cutting life, and higher cost of the latter. FC subtropical and tropical fruits make up a small (probably less than 10%) share of the total FC produce market. Nevertheless, wherever subtropical and tropical fruit crops are grown throughout Asia, Africa, Pacifica and the Americas, vendors at roadside stands, produce markets, grocery stores and supermarkets prepare local fruits for immediate sale as FC fruit products such as green coconuts ready to drink, sliced pineapples, mango and papaya slices and chunks, jackfruit and durian arils, de-spined and peeled Opuntia cactus fruit, and citrus fruit segments. A few countries in subtropical and tropical fruit producing regions, such as Thailand, also have specialized commercial FC processing companies that sell FC fruit products domestically and internationally. In the US and EU, subtropical and tropical fruits imported from the producing countries as well as some domestically produced subtropical fruits are processed into FC products by specialized FC companies as well as on site at supermarkets. It is not possible to estimate the amount of subtropical and tropical FC fruit products sold compared to temperate FC fruit products, but according to the United Fresh Research & Education Foundation and the Perishables Group (UFREF, 2009) annual retail sales of all FC and other value-added fruit products in the US were approximately $3.33 billion, or about 15% of total fresh fruit sales. The most important subtropical and tropical FC fruit products in the US and EU are pineapple, mango and kiwifruit slices and chunks, watermelon and muskmelon chunks, loose grape berries, pomegranate arils, and citrus fruit segments.

10.2

Handling and conditioning of raw materials for processing

Non-climacteric fruits, such as citrus fruits and pineapples, must be harvested when fully ripe to assure good flavour quality. Climacteric fruits can continue to ripen after harvest and may be picked mature-green or partially ripe. In such cases, these fruits should be ripened to the optimal ripeness stage for cutting and to assure consumer satisfaction with their flavour. Since FC products of climacteric fruits continue to ripen, it is possible to cut the fruit before full ripeness when there is enough time between cutting and sale to allow for completion of the ripening processes. Optimal ripening temperatures range between 15 and 25°C

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(the higher the temperature within this range, the faster the ripening). Relative humidity should be kept between 85 and 95% to reduce water loss and associated fruit shrivelling. Addition of ethylene gas at 100 to 150 ppm for one to two days to the ripening room promotes faster and more uniform ripening. Carbon dioxide concentration within the ripening rooms should be kept below one per cent by introduction of fresh air since higher concentrations reduce the efficacy of ethylene. Application of 1-methylcyclopropene (1-MCP) can be used to delay ripening of partially ripe fruit (see section 10.5). Heat treatments of intact fruit prior to cutting have been evaluated for their effects on post-cutting rates of browning and softening, but there is currently no commercial application except in the use of warm water for cleaning and sanitizing some intact fruit before processing. Fruit destined for FC processing should be cleaned with chlorinated (100–150 ppm) or otherwise disinfected water to remove contaminants and reduce microbial load before moving the fruit to the processing area.

10.3

Sanitation of whole and fresh-cut fruits

In order to achieve FC fruits with fresh-like quality, safety, and high nutritional value, the industry needs to implement improved strategies by introducing or combining sustainable techniques, especially standard procedures for sanitation. The key elements for the production of safe FC fruits include screening materials entering the processing chain, suppressing microbial growth, reducing the microbial load during processing, and preventing post-processing contamination (Artés and Allende, 2005). Over the past two decades, the FC industry has grown tremendously. However, the growth of FC tropical and subtropical fruit sales, with the exception of pineapple and mango, is much lower than other fruits such as cantaloupes, watermelon and apples. Sanitary practices have also changed and are now more complex. Food processing and preparation depend on more mechanized and large-volume processes. The foods produced by these processors and retailers are eaten by millions of people each day. Therefore, it is more and more important for workers to understand sanitary food-handling principles and food hygiene. Workers who understand why food sanitation is so important are more likely to use safe practices. Therefore, proper personal hygiene and proper sanitation of equipment and whole produce are the most important keys in the handling chain of fruit processing, especially when tropical and subtropical fruits are transformed into FC products, because no mechanical equipment or atomizing systems have been developed yet. The FC fruit industry needs appropriate sanitation procedures and new strategies for reducing microbial load of whole and FC produce to assure high quality and safe commodities. The removal of soil and microorganisms is the most important target for keeping overall quality of FC fruits. In order to avoid fruit contamination that affects the final quality of the product, every step in the

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production chain must to be considered. The sanitation of the raw material and the FC fruit is the principal step that reduces microbial load throughout the production chain. This, in combination with proper postharvest handling and optimal sanitation techniques, enhances maintenance of fruit quality. Among the different techniques used for fruit sanitation, chlorine treatment (applied as sodium or calcium hypochlorite) is the most widely used worldwide. However, chlorine presents a major disadvantage: the risk of the formation of undesirable by-products upon reaction with organic matter, which may lead to new regulatory restrictions in the future. Moreover, its efficacy has been demonstrated to be low for some products. Consequently the FC processing industry demands safer and natural alternatives. Artés-Calero et al. (2009) reported that antimicrobial washing solutions, O3, UV-C radiation, intense light pulses, super high O2, N2O and noble gases, alone or in combination, are the most promising sanitization treatments. However, it is well known that the use of conventional or new sanitizers, especially those of natural origin, requires knowledge of the benefits, and the possible negative effects of the treatments on the quality attributes of the treated produce that limit consumer acceptance. González et al. (2009a) described the different emerging technologies such as ultraviolet irradiation (UV-C), edible coatings, active packaging and natural additives, to preserve the quality of FC fruits; highlighting the areas in which information is still lacking, and commenting on future trends. 10.3.1 Sanitation in the processing plant An effective sanitation programme for FC fruit and vegetable processing facilities requires the same basic components needed in other food operations: appropriate cleaning compounds and sanitizers, effective cleaning procedures, and effective administration of the sanitation programme. The ultimate goal is to provide a finished safe product with a proper shelf life for marketing. The sanitation programme for fruit and vegetable processing facilities requires hygienic design of facilities and equipment, training of sanitation personnel, use of appropriate cleaning compounds and sanitizers, adoption of effective cleaning procedures, and effective administration of the sanitation programme – including evaluation of it through visual inspection and laboratory tests. Effective sanitation starts with reduced contamination of raw materials, water, air and supplies. If the facility and equipment are hygienically designed, cleaning is easier and risk of fruit contamination is reduced. Effective preservation of fruits and vegetables depends on the prevention of contamination by spoilage-causing and pathogenic microorganisms during production, processing, storage and distribution. Raw materials are potential sources for food spoilage microorganisms and contribute to bacterial pools within a processing plant. During harvest and handling, fruit are exposed to many unclean environments and can provide additional contamination in the receiving, raw material storage, and processing areas. The incoming materials may contain hazardous chemicals

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such as pesticide residues, and water could be contaminated with heavy metals and chemical residues. A good sanitation programme must be established in order to minimize the risk of contamination. Furthermore, the intermediate products may become contaminated in the processing steps from cleaning compound residues due to improper rinsing or inappropriate handling of produce. Also, raw material and packages may be contaminated with hazardous extraneous material such as metal, plastic, glass fragments and wood slivers. Different sanitizers are being used in the FC industry and new sanitizers are in the process of approval. Proper concentration and contact time differ depending upon the treated produce. Table 10.1 provides information about chemicals appropriate to use for sanitizing fresh produce and handling facilities. 10.3.2 Equipment sanitation Equipment needs to be cleaned and sanitized after FC fruit processing. Small fruit pieces and juice remain in the different parts of the machinery (cutting, peeling, Table 10.1

Chemicals used for sanitation in food handling facilities

Class

Other name/ Optimum Example pH

Optimum use Advantage temperature

Chlorine

Sodium Neutral to Room hypochlorite slightly temperature acidic

Disadvantage

Kills broad Corrosive if not spectrum of used correctly, microorganism short shelf life, organic matter reduces activity

Iodine Based Iodophor

Acidic

Room temperature (100 –

Contribution (%) per serving

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100 g DM 0.309 0.147 0.178 0.990 0.076 1.730 1.584 2.059 1.321 32.300 1.376 0.203 0.531 0.046 0.408 4.466

Minerals Ca (g) P (g) Mg (g) K (g) Na (g) Zn (mg) B (mg) Fe (mg) Se (mg)* Mn (mg) Cu (mg) Ni (mg) Cr (mg) Cd (mg)** Pb (mg)** Sr (mg)

200 g juice (1 serving) 0.074 0.035 0.043 0.238 0.018 0.415 0.380 0.494 0.317 7.752 0.330 0.049 0.127 0.011 0.098 1.072

115.26 82.33 115.26 65.86 181.13 167.95 107.03

– – – – – – – – Daily recommendations 1.000e 0.700e 0.280e 4.700f 1.500f 8.0–11.0g 20.00g 14–29g 0.055h 1.8–2.3g 0.900g 0.350g 0.035g 0.070i 0.250i –

– – – – – – – – Contribution (%) per serving 7.42 5.04 15.26 5.06 1.22 4.0–5.2 1.90 1.70–3.52 >100 >100 36.69 13.92 >100 15.77 39.18 –

Notes * Total mineral selenium (not only aminoacid-Se). ** TTDI: Total tolerable daily intake. CAE: Citric acid equivalent.

Sources: Rogez (2000). aRDA (2002); bFiguerola et al. (2005); cFAO/WHO (2001); dFAO/WHO/UNU (2007); eRDA (1997); fRDA (2004); gRDA (2000a); hRDA (2000b); iSalgado (2003).

480.26 343.04 480.26 274.43 754.69 699.80 445.95

Proline Tyrosine Serine Cysteine Asparagine + aspartic acid Glutamine + glutamic acid Arginine

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daily intake in only one serving. Therefore, it can be considered as a good source of dietary fiber. The total amount of α-tocopherol found in açai is high, ranging from 37 to 52 mg 100 g−1 DM, which makes the juice of this fruit an excellent source of this form of vitamin E. Each serving of açai provides more than 100% of the intake recommended by FAO/WHO (2001) for adult men and women. Açai also has a good fatty acid profile (49.72% oleic acid, 25.31% palmitic acid, and 13.51% linoleic acid as a proportion of total fatty acids: Table 1.2), but its content of omega-3 fatty acids is poor (approximately 1%), in contrast to the information presented on many websites. 1.1.6 Phenolic compounds of açai fruit The violet color of the açai drink is due to the high concentration of anthocyanins: antioxidant compounds that are also natural pigments. Anthocyanins belong to the flavonoid family, and include cyanidin-3-glucoside (C3G), and cyanidin3-rutinoside (C3R). These two pigments are the major phenolic compounds in açai. Anthocyanins are predominantly present close to the açai fruit’s epidermis. Pompeu et al. (2009a) found levels of anthocyanins of approximately 2890 mg Kg−1 fruit when they studied different solvents to optimize the extraction of phenolic compounds from açai fruit. Our research team found an average total content of anthocyanins of 1,441 mg 100 g−1 (dry matter) DM in açai pulp (1841 mg Kg−1 fruits), accounting for 37% of the total phenolic content, with 79.2% C-3-R, and 20.8% C-3-G. We found a

Table 1.2

Fatty acid profile of açai oil

Fatty acids (g 100 g−1 total fatty acids analyzed) Palmitic acid (C16:0) Palmitoleic acid (C16:1) Estearic acid (C18:0) Oleic acid (C18:1) Linoleic acid (C18:2) α-Linolenic acid (C18:3) Vacenic acid (C18:1 cis 11) SFA/UFA MUFA/PUFA ω6:ω3

25.3 1.5 4.46 49.7 13.5 1.16 4.37 0.42 3.790 11.65:1

Daily recommendations

Contribution (%) per serving

– – – – 12.0–17.0a 1.1–1.6a – 0.05). Low-density lipoprotein (LDL) TBARS was expressed in mmol MDA g−1 LDL. This method evaluates the formation of malondialdehyde (MDA), which is an important biomarker for the evaluation of oxidative stress. On day 28, the LDL-TBARS had decreased significantly, especially in subjects observed to have high initial values. The average initial and final values for thirteen volunteers were 4.12 ± 1.99, and 1.81 ± 0.86 mmol MDA g−1 LDL, respectively. These results demonstrate that daily intake of açai juice, which is rich in phenolic compounds, has a positive impact on the reduction of LDL oxidability and has a tendency to increase plasma antioxidant capacity, suggesting a protective effect against cardiovascular disease. Jensen et al. (2008) investigated the antioxidant and anti-inflammatory properties of a juice blend (JB), containing a mixture of fruits with known antioxidant activity, including açai as the predominant ingredient. A treatment with 12 healthy subjects examined the JB’s antioxidant activity in vivo. Blood samples at baseline, 1 h, and 2 h following consumption of the JB or placebo were tested for antioxidant capacity using several antioxidant assays and the TBARS assay. A within subject comparison showed an increase in serum antioxidants at 1 h (p < 0.03) and 2 h (p < 0.015), as well as inhibition of lipid peroxidation at 2 h (p < 0.01) postconsumption.

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Fruit ripening, seasonality and accumulation of anthocyanins

1.2.1 Fruit ripening Like other fruits rich in anthocyanins (e.g. raspberries, strawberries, mulberries, grapes, and cherries), the açai fruit is not climacteric. Therefore, if the fruit bunches are picked before they are ripe, the pigmentation will not change subsequently and the fruits will shrivel up and detach from the spadices. The color of the açai fruit changes during the ripening process. For the black variety, which represents more than 95% of commercially produced fruit, farmers exclusively use the external color to determine the level of maturity. Based on field data, we can distinguish five stages of ripening for the black variety, and for each bunch:

• • • • •

Green fruits are at least half green in color. Slightly mature or Vitrin fruits are those in which the majority of the fruit is black, and a smaller portion is green. At this stage, the fruit can be sold commercially, but pulp production is low because the fruit is not yet ripe. Black fruits are black in color with a shiny surface. The fruit and its juice are of good quality, however, this is not considered the ideal phase for harvesting. Tuira fruits are black, but are covered by a thin layer of wax, which gives them a white appearance. The quality of the pulp and juice is considered to be very good. Over-ripe fruits are covered by the same layer of wax as Tuira fruits but are a little bit drier, and flatter. Typically, bunches picked at this stage have been picked too late.

1.2.2 Seasonality Açai palms collectively produce fruit between March and June (the low season or rainy season) and between August and December (the high season), with individual, açai palms bearing fruit for four to six months of the year. Seventy percent of the annual production occurs during the high season. During the low season, the fruits are traded at different stages of maturity, whereas they are more uniformly ripe during the high season. This variable affects both the growth of micro-organisms in these fruits, and the concentration of anthocyanins. Despite the lower quality, the price of açai fruits is between two and eight times higher during the low season, as fruit supply is four times lower during this season than during the high season. 1.2.3 Accumulation of anthocyanins Because the anthocyanin content of açai is of great interest, it is important to verify certain parameters at harvest to ensure that the fruit is picked when the anthocyanin level is adequate. The stage of maturity at the time of harvest is the main factor that affects the concentration of anthocyanins. The kinetics of anthocyanin accumulation in plants is poorly documented. Some studies report

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changes in anthocyanin content with time or with the maturity stage, but they do not define the kinetics of this phenomenon. Therefore, our research team evaluated anthocyanin accumulation in açai fruits during the ripening process, and verified some important parameters using a sigmoid kinetic model. The variables assessed included the following:

• • •

The maximum accumulation per day (dy); The maximum concentration in fruits (Cmax); The corresponding stage of maturity (S).

The average accumulation rate was 35.63 mg kg−1 fruit/day, and the total concentration was 1443 mg kg−1 fruit. The time required to reach Cmax, the optimal degree of ripeness, was very long for açai fruits: 69 to 94 days were required to reach ripeness after the appearance of the first black spots. As anthocyanins are of great benefit to health, it is not recommended that the fruits are harvested when the concentration of anthocyanins is less than half of Cmax, or while the external appearance of the fruits is black. Açai fruits should be collected when the concentration of anthocyanins is at 85% of Cmax or higher, which corresponds to approximately 62 days after the appearance of the first black spots. Indeed, the rate of accumulation decreases progressively when the anthocyanin concentration approaches Cmax. Furthermore, structural and microbiological disorders may appear with time. Producers usually evaluate the maturity of anthocyanin-rich fruits by looking at their external color instead of counting the time after the beginning of the ripening process (the first black spots). Therefore, each time fruit samples were collected in this study, the stage of ripeness of the fruits was determined based on their color. A preliminary assessment of the degree of ripeness of the fruits was conducted by visual observation. Then, a precise determination of the maturity stage was obtained based on the percentage of black coloration, and the presence of wax cuticles. The stage of maturity of the fruits was estimated according to the following scale: stages 1 to 6, green fruits that were at least 0, 20, 40, 60, 80 and 100% black, respectively; and stages 7 to 11, black fruits with a minimum of 20, 40, 60, 80 and 100% wax cuticle covering, respectively. When the anthocyanin concentration was plotted against the stage of ripening, it was possible to fit sigmoid curves to the data (Fig. 1.1). At a maturity stage of 8.5, the anthocyanin concentration was 85% of Cmax. As maturity class 9 is defined as the stage when a minimum of 60% of black fruits are covered with a wax cuticle on their surface, producers should be encouraged to wait at least until this stage is reached before the fruits are picked.

1.3

Maturity and quality components and indices

During the production of a crop of açai, the average composition of any of the macronutrients presented in Table 1.1 does not change significantly because the standard deviation is relatively large; however, there is evidence of significant

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Fig. 1.1 Kinetics of anthocyanin accumulation in the açai fruit according to fruit weight and ripening time.

changes in mineral content, particularly in the levels of iron and manganese, which increase gradually throughout the high season (Rogez, 2000). Because soluble sugars represent a particularly low proportion of the pulp (see point 1.1.6), Brix cannot be used to evaluate the maturity stage of the fruits. As already mentioned, it seems that the anthocyanin content is the best criterion to confirm the full maturity of the fruits. Quantification of the anthocyanin content can be very quick for the manufacturer, requiring a simple extraction with alcohol and HCl and a simple photometer in the visible spectrum at approximately 515 nm. As discussed above, anthocyanin accumulation is mainly influenced by the ripening time, and the wax cuticle covering the fruits may be used as an indicator to achieve a maximum concentration of these phenolic compounds. Rogez (2000) also found that the smallest fruits contain more anthocyanins than the largest fruits in terms of content per kilo of fruit (Fig. 1.1). In fact, a significant and negative correlation could be observed between the anthocyanin content and the weight of the fruits. As these pigments are mainly present in the first cellular layers and smaller fruits have a higher surface to volume ratio, a higher proportion of cells are exposed to light, and produce anthocyanins.

1.4

Preharvest factors affecting fruit quality

1.4.1 Genetic factors of variation For an allogamous species (i.e. a species that reproduces by mating), the açai palm presents a high degree of variation in many parameters of interest, such as the earliness of fruit production, fruit productivity, pulp output, and production time. Different kinds of açai palm were defined according to their inflorescence forms

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and bunches, the numbers of fruits per rachillae, and the diameters of the trees. Based on these different agronomic varieties, Bovi (1998) concluded that the genetic variability within a population is, for the most part, greater than the variation between different populations. Rogez (2000) found similar results when analyzing pulp composition (see section 1.1.6). Based on these results, one can conclude that no single sample can be considered as representative of a population. The absence or presence of springs, the speed of palm growth and the morphological characteristics of the leaves are the main vegetation features that allow us to distinguish between different populations. Nevertheless, Bovi (1998) also observed significant differences between populations in terms of the length of the sheath and spadicea, as well as in the number and length of leaflets. Rogez (2000) also observed that the average weight of the fruit varies between plants (shrubs). Some plants produce larger fruits than others in the same population. 1.4.2 The soil factor: solid ground versus floodplains The açai palm grows mainly in floodplains or in areas near tributaries of rivers with running water. Productivity typically varies between 7 and 9.3 kg of fruit per stem. It is preferable to grow açai palms in areas with medium humidity of soil, such as in medium and high floodplains. It can grow in highly humid soils (e.g. areas that flood twice a day at high tide), although its productivity is reduced by approximately one-half. The average number of bunches per plant in less humid soil is five, whereas it is only three in more humid areas. Rogez (2000) found that the most productive variety was the black variety when planted in less humid soils.

1.5

Postharvest handling factors that affect quality

The amount of time that elapses between harvest and consumption affects açai quality. It influences direct variables, such as the loss of water, as well as indirect variables such as the loss of aroma and nutritional quality. 1.5.1 Temperature and relative humidity management The ideal temperature for the transportation and storage of açai fruit is between 10 and 15°C. If the temperature increases by 10°C, the rate of deterioration increases by a factor of two or three. According to Pompeu et al. (2009b), the temperature of açai fruit in the harvesting baskets increases significantly (p < 0.001) – by approximately 4°C – in the first few hours after picking. Because the açai fruit is non-climacteric, the elevation of temperature that occurs after picking may be due to the impacts suffered by the fruit during harvest and the compression that occurs during transportation and storage. In spite of low levels of available sugars, açai fruits present an intensive respiration just after picking, leading to a rapid decrease

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in oxygen levels in the baskets, and prefiguring optimal conditions for a subsequent fermentation (Aguiar, 2010). The temperature increase is not desirable, as it significantly reduces the fruit’s shelf life.

1.5.2 Physical damage Lesions are the main cause of açai fruit quality deterioration. They allow microorganisms to access the fruit and oxygen to directly access the oxidizable substances contained in the fruit. They also accelerate water loss and rotting. Just after picking the bunches, açai fruits are immediately separated from the spadices; thus, it is likely that lesions in the apex of each fruit can cause rapid deterioration. Every surface that is in contact with the fruit after harvest is a potential source of infection and all surfaces must, therefore, be extremely hygienic. In the case of açai fruit, the three most significant contaminating surfaces are:

• • •

The baskets used by growers to transport the fruits to the cities. They are made of plant material that cannot be cleaned, and are used for 4 to 6 months. The wooden surfaces of the boats used for transportation, which may come into direct contact with the fruits through the baskets. The ground that can come into contact with the baskets (e.g. the floor of the market or harbor, etc.).

1.5.3 Atmosphere Açai fruit are transported in boat cargo to processing centers, with journey times varying from eight to 35 hours. It is thought that during the transportation of açai fruits in boat cargo holds, the fruits respire for hours, air circulation is low, and they begin to ferment. Fermentation is facilitated by high microbial levels, substrate availability, high temperature, and high humidity. Conditions are anaerobic, generating volatile compounds such as lactic acid, acetic acid and short-chain fatty acids (Aguiar, 2010). Bacterial multiplication in açai fruits reaches the first logarithmic order only 12 hours after harvest, and reaches the second order after 32 hours. The abundance of fungi increases 10- and 100-fold after 20 and 60 hours, respectively. Such fast growth of micro-organisms is exceptional for a fruit (Rogez, 2000). In non-acidic products, fungi multiply very slowly in comparison to bacteria, whereas in açai fruit, fungi multiply much faster than bacteria. This indicates that the fruit has become more acidic and suggests that a fermentation process could be occurring.

1.6

Microbiological and physiological disorders

1.6.1 Microbiological contamination and quality deterioration The açai fruit has a high basal level of mesophylic bacteria, fungi, and total coliforms (Rogez, 2000). In 48 hours of storage at the ambient temperature of the

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region (approximately 30°C), mesophylic bacteria, fungi and total coliforms increase logarithmically (section 1.5.3), which affects the quality of the açai. Forty percent of the anthocyanins present in the fruit are oxidized during this time (an average of 660 mg of anthocyanins kg−1 of fresh fruit decreases by 380 mg kg−1 of fruits after 48 hours). The fruit also shrivels and the pulp sticks to the core, reducing pulp yield during the depulping process (Pompeu et al., 2009b).

1.6.2 Physiological disorders Rogez (2000) found that two enzymes of great importance are abundant in the açai fruit: peroxidase (POD), and polyphenoloxidase (PPO), which are vegetal tissue enzymes that belong to the oxidoreductase group. In the cases of açai fruits and fresh açai juice, the color change in the presence of oxygen – from red/purple to brown – is directly associated with the activity of PPO on the anthocyanins as well as changes in its sensorial and nutritional properties. In fact, it is well known that PPO oxidizes monophenolics, leading to the formation of o-diphenol compounds and to the oxidation of o-dihydroxy compounds to quinones. The quinones subsequently undergo polymerization, producing characteristic yellow to brown colors in the product (Nunes et al., 2005). POD is distinctive because it is a thermo-resistant enzyme that is used by the agro-industry as an indicator of efficiency in thermal treatments. Rogez (2000) determined high levels of POD and PPO activities in fresh açai juice. POD activity has also been found to increase significantly with postharvest time, especially more than 24 hours postharvest, whereas PPO activity was notably constant in the three days postharvest when the study was conducted.

1.7

Pathological disorders, insect pests and their control

Insect prevalence is an important factor compromising the production of açai palm. Between 2000 and 2010, areas under cultivation have expanded significantly, and practices have become less sustainable in terms of their impact on biodiversity (there has been açai palm plantation as monoculture that involves the destruction of other species). As a result of monoculture, blights have appeared more frequently, which is a cause for concern considering the potential damage to the crop. Several insects can attack the açai palm, from the seed phase to the adult plant. Blights remain little understood, which is why we highlight them herein.

1.7.1

Main pests according to Homma et al. (2005)

Cerataphis lataniae (Heteroptera: Aphididae), or the palm aphid, mounts intense attacks on the açai palm at the nursery during the first three years of life, as well as in the field.

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Symptoms: This insect retards the development of açai palm seedlings, making them weak, and turning the leaves yellow, because both immature and adult aphids feed on the sap. Control: Control in the nursery is established by separating the infected plants from the healthy ones, and by removing the insects. The damaged plants are isolated from the nursery, and observed until confirmation that the blight has been completely eliminated. There is no known method of controlling this blight in the field, and therefore, care must be taken not to introduce damaged plants in the final plantation. Rhynchophorus palmarum (Coleóptera: Curculionidae), or the palm weevil, attacks the açai palm in the field, from 3 years old onward, when the plant’s stem is sufficiently developed. Symptoms: The damaged açai palm decreases in size. It has yellow leaves with tanned petioles, a smaller number of leaves or an absence of bunches, aborted inflorescences, and a stipe with black holes in the wreath. Control: The use of traps is the safest way to control this parasite. Mytilococcus (Lepidosaphis) bechkii (Heteroptera: Diaspididae), or comma scale, attacks the açai palm at the nursery and in the first years of life in field. Symptoms: This organism becomes fixed along the main nerve, in the ventral part of the leaflets. Due to the insects’ constant sucking of the sap, the plant displays yellow leaves. Its development and fruit production are also delayed. Control: As there is no registered insecticide that can control this blight in açai palm, control relies on preventive measures. Aleurothrixus floccosus (Heteroptera: Aleyrodiae), or wooly whiteflies, attack the açai palm at the nursery, and young plants in the field. Symptoms: Due to depletion of the sap, the leaflets turn yellow, after which the plant becomes weak, and exhibits delayed development, and production. Control: As there is no registered insecticide that can control this blight in açai palm, certain preventive measures can be adopted. Eutropidacris cristata (Orthoptera: Acridiae), or the coconut tree grasshopper, attacks the açai palm at the nursery, and young plants in the field.

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Symptoms: This organism impedes the development of the plant and, consequently, delays the initiation of the productive phase due to the voracity with which young, and adult insects feed on the plants. Control: Control requires the use of bait placed in the vegetation among the palms. Synale hylaspes (Lepidoptera: Hesperidae), or simply Synale, damages the açai palm at the nursery, and in the first years of life. Symptoms: The caterpillar eats the leaf blades, tearing them, and making them dry and brown. Control: There is no method yet available to control this blight in the field. It is important to remember that the açai product produced in the Amazon Region, commercialized and exported to other states and countries is considered ‘organic’ because, as outlined in this section, no pesticides are used in its production. 1.7.2 ‘Trypanosoma cruzi’ One of the big problems of concern to Amazonian authorities is infection by Trypanosoma cruzi, a protozoan that causes Chagas disease, and is transmitted by insects of the Triatominae sub-family (intermediate hosts). In the Amazon region, the triatominae do not live inside houses but in the canopies of palms, and in trees; only the females can fly, and enter houses, drawn by light (IEC, 2007). Once inside a house, they are further drawn by the CO2 exhaled by humans, and domestic animals. As infection of several groups has occurred in the region, it cannot be justified by triatomine bites alone. Thus, in the 1990s, there was increasing suspicion that transmission was not only due to direct contact of triatomines with humans. Progressively, the oral route was shown to be a major mode of transmission for Chagas disease, with infection occurring by the ingestion of crushed infected insects or their stool (Barghini, 2008).

1.8

Postharvest handling practices

1.8.1 Harvest operations After the fruit that is to be picked has been selected, the reapers climb to the top of the stems to remove the bunches of fruit. That tiring physical activity is performed with the help of a ‘peconha’, which is a sort of handicraft belt that is wrapped around the feet to provide support when climbing, allowing the reapers to use their arms around the stems to maintain balance. After climbing to the top of the tree, the reapers cut the bunch at its base using a butcher’s knife, and then

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pull out the stem. If a second bunch on the same plant is mature enough, the reaper goes directly from one stem to another, without going down. The bunches are brought to the ground by hand, and then laid on the ground or on a plastic sheet in order to avoid direct contact with the soil. The harvest time begins in the morning (frequently between 6 and 10 am due to the low temperatures) or after 3 pm, according to business requirements, but it rarely occurs at high temperatures. Separating the seeds This phase consists of passing the fingers through the bunches and pressing to force the fruit to fall down. It is performed right after the harvest, generally at the same place, and the fruits are then placed in baskets. Full baskets are brought home, and are later taken to the port storage facility for trading. The duration of transport on foot may be 1 hour. In some cases, the growers put leaves at the bottom, and on top of the baskets to preserve the fruit. Rogez (2000) evaluated the evolution of temperature in the center of seven baskets of fruit during the postharvest period. The temperature increased significantly (p < 0.001) in all of the lots of fruit that were evaluated, especially during the first 15 hours, when it increased from 26 to 31°C. Transportation The means of transportation most frequently used in the Amazon estuary is boats. The açai palm grows mainly in floodplains, and therefore, 90% of the crop is transported by boat for commercialization. Distribution The main commercial centers where the fruits are transported are in Belém city, where the majority of the crop is traded among street market vendors or small businessmen, who extract the pulp from the fruit using traditional machines. 1.8.2 Recommended storage and shipping conditions The conditions between harvesting and obtaining the final product are very important because they play a role in the loss of water, aroma, and bioactive compounds. Pompeu et al. (2009b) evaluated the effects of refrigeration during storage of the fruit. Refrigerated fruit presented little loss of mass, a minor proliferation of mesophilic bacteria, and fungi, and a slight degradation of anthocyanins, even when stored at only 15°C (Fig. 1.2). A mass loss of 3 to 6% may negatively impact the nutritional, and sensorial properties of fruit in general. In açai, the problem is even more significant because the edible portion of this fruit consists of the external thin surface of epicarp and the mesocarp, which accounts, on average, for only 12% of the fruit’s weight. This loss of mass is due to the elimination of water and CO2 during the metabolic process of respiration. In environments with low temperatures, there is a reduction of metabolism in the fruit and, consequently, little mass loss.

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Fig. 1.2 Mass loss (a), evolution of total mesophilic bacteria (b), and evolution of anthocyanin concentration (c) in açai fruit as affected by duration and temperature of storage.

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Fig. 1.2 Continued.

1.9

Processing practices

As açai has a high level of microbial contamination, it has a short shelf life, which limits its value and hinders its commercialization. To reduce levels of microbial contamination, it is necessary to improve harvesting, packaging, and transportation practices, and reduce the time taken for the harvested fruit to reach the market. This would improve the quality of the fresh fruit raw material without the use of chemical agents or technology, ensuring lower production costs. 1.9.1 Fruit reception Açai fruits are transported to processing units packaged in baskets or plastic boxes, which are weighed before the selection process. 1.9.2 Selection Manual selection of the fruits is conducted on stainless steel tables, using baskets that retain the fruit, but allow small contaminating elements, such as sepal and rachillae fragments, soil, and shrunken fruit, to pass through. At this phase, the

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green fruits that are in a dubious phytosanitary state, or that have other types of problems that make them unsuitable for processing, are removed from the lot. 1.9.3 Washing The fruits are immersed in water to remove contaminating elements. The cleaning process is repeated three times, with chlorinated water used for the second wash. 1.9.4 Blanching Açai blanching is optional, and is only performed when the juice production process does not include a pasteurization stage. Blanching can be done by plunging the fruit into hot water (~80°C) for 10 seconds; these conditions reduce the microbial content of the fruit, and eliminate the majority of air present in the fruit, without fully denaturing the PPO, and POD enzymes. High temperatures of 80°C for more than 10 seconds alter the juice emulsion, and cause partial separation of the lipids. 1.9.5 Softening The fruits are immersed in lukewarm water to soften the epicarp and mesocarp, which facilitates the crushing of the pulp. The variables affecting the softening process include water temperature, and immersion time, which are altered by the processors according to the fruit’s provenance, and its level of maturity. The water used in this process is generally at room temperature or at an average of 40 to 45°C. The softening time is varied from 10 to 60 minutes: the greater the degree of maturation, the shorter the time of fruit immersion. 1.9.6 Depulping At this stage, traditional machines commonly known as beaters are used. Açai juice is prepared in vertical stainless steel models that crush the açai fruit while adding water. The process of depulping of the fruit begins with the blade action; the movement of the blades promotes rubbing of the fruit, which is followed by progressive addition of water. The processed product goes down the machine, passing through a filter, and it is then stored in stainless steel bowls. 1.9.7 Clarification Pulp clarification is a method used to improve the aesthetic properties, and market acceptability of the fruit by eliminating most of the lipids and fibers. PachecoPalencia et al. (2007) evaluated the effects of clarifying the açai pulp, and observed that the use of diatomaceous earth had a detrimental effect on the quantity of anthocyanins and other phenolic compounds, and reduced the antioxidant capacity

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of the fruit. However, this process was efficient in removing polymeric compounds, resulting in pulp with a low level of insoluble solids, and a bright purple color. 1.9.8 Pasteurization Pasteurizing natural açai juice allows it to be conserved at +4°C for ten days. Treatment at 90°C for ten minutes completely eliminates molds, and yeasts, guaranteeing adherence to official quality standards (BRASIL, 2000), and also causes total denaturation of PPO and POD. However, this treatment also causes considerable loss of anthocyanins. To conserve açai at −20°C for several months, industrial producers use temperatures of approximately 80 to 85°C, for 10 to 30 seconds. The residual activity of POD is an indicator of pasteurization success. It is important to remember that treatments at temperatures of greater than 80°C or durations of longer than ten seconds provoke the separation of fatty matter. A green-colored oil layer forms at the surface, because the emulsion has not formed correctly. The addition of the citric acid to decrease the pH of açai is permitted up to a concentration of 5%. This causes the destruction of bacteria and enzymes during the pasteurization process, and helps to conserve particularly the phenolic compounds in the product.

Fig. 1.3 Quadratic evolution of residual anthocyanins (percent) as a function of temperature of pasteurization and pH of the açai (constant time of 60 s).

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Fig. 1.4

Quadratic evolution of the residual activity (percent) of peroxidase according to the pasteurization temperature and pH of the açai (constant time of 60s).

1.9.9 Dehydration The technology most commonly used to obtain dried açai is atomization (spray drying). This produces açai powder with high anthocyanin content. In this process, the drying time is short (between 1 and 10 seconds). When using a spray dryer (Mobile Minor Unit AS0340D model) to obtain the açai powder, the following operational conditions may be applied: an entering air temperature of 135 to 140°C; an exiting air temperature of 85 to 90°C; and a pressure of 4.9 to 6.2 kg cm−2. The açai powder, once obtained, has a longer shelf life when packaged in aluminum and plastic (Melo et al., 1988). Silva et al. (2008) evaluated the adsorption and desorption isotherm of açai powder. They concluded that açai presents a typical type-III adsorption isotherm. As the variation in desorption heat is low, the product is not very hygroscopic, with the final product presenting a monolayer value of 7.1 g H2O per 100 g DM. Tonon et al. (2010) evaluated the anthocyanin stability and antioxidant activity of spray-dried açai juice produced with different carrier agents for 120 days, and concluded that anthocyanin degradation exhibited two phases of first-order kinetics: the first, with a higher reaction rate, occurring in the first 45 to 60 days of storage, and the second, with a slower reaction rate, occurring after 60 days. An increase in water activity also resulted in higher anthocyanin degradation, due to the greater molecular

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mobility, which allows for greater oxygen diffusion, thus accelerating oxidation reactions. 1.9.10 Extraction of anthocyanin from açai fruits An important technique nowadays is the extraction of anthocyanins from several different fruits using organic solvents; this anthocyanin can be used in natural dyes and natural supplements. Studies on the extraction of phenolic compounds from açai fruits are minimal; there is one report on the effect of methanol and ethanol on the phenolic extraction (Rodrigues et al. 2006), and this study did not investigate any other factors. To expand upon these studies, Pompeu et al. (2009a) studied the optimization of the extraction of antioxidant compounds using the proportion of ethanol, the concentration of hydrochloric acid, and the temperature of the process as variables. The optimized conditions that maximized the yields of phenolic compounds were as follows: an ethanol proportion between 70% and 80%; a hydrochloric acid concentration between 0.065 and 0.074 mol L−1; and a temperature of 58°C. The three variables investigated in the present study could be ranked as follows in terms of their impact on extraction performance: temperature > ethanol proportion >> hydrochloric acid concentration.

1.10

Conclusions

Several studies have been conducted to elucidate the benefits of açai for human health. The biggest problems observed in açai production today are related to the conditions used to obtain açai, which still need improvement. Handling, harvesting, and transportation methods are still very rustic, and are undertaken without the necessary care, and hygienic precautions that these practices demand. Açai growers are resistant to new technologies or even to the application of basic knowledge, such as good manufacturing practices. Because it is a potential source of phenolic compounds, particularly anthocyanins, açai should be further examined in future research. This research should aim to apply, develop and optimize technologies for the extraction and purification of phenolic compounds. However, few studies regarding the stability of these compounds when used in the nutrition, pharmaceutical or cosmetic industries have been conducted to date.

1.11

References

Aguiar F. S. (2010), Avaliação da fermentação espontânea dos frutos de Euterpe oleracea durante o período pós-colheita e suas possíveis implicações sobre a atração de triatomíneos. Master D. Universidade Federal do Pará, Belém, Pará, Brazil. Associação Brasileira das Indústrias da Alimentação – ABIA (2005), Mercado Brasileiro dos alimentos industrializados. Available from http://www.anuarioabia.com.br/ editorial_05.htm [accessed 10 June 2008].

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Barghini A. (2008), Influência da Iluminação Artificial sobre a Vida Silvestre: técnicas para minimizar os impactos, com especial enfoque sobre os insetos. Ph.D Tesis – Universidade de São Paulo, São Paulo, Brazil. Bastos C. T. R. M., Souza J. N. S., Larondelle Y. and Rogez H. (2007), ‘Excretion of açai (Euterpe oleracea) anthocyanins in human urine’, in ICPH2007 – 3rd International Conference on Polyphenols and Health, Kyoto, Japan. Bovi M. L. A. (1998), ‘Resultados de pesquisas referentes à exploração, manejo e cultivo do açaizeiro’, in Mourão L., Jardim M. A. G. and Grossmann M., Açai: possibilidades e limites em processos de desenvolvimento sustentável no estuário amazônico, Edn CEJUP-PA, Belém, PA, Brazil. BRASIL (2000) ‘Padrões de identidade e qualidade mínima para polpa de açaí’, Instrução Normativa n° 1, Ministério da Agricultura, Diário Oficial da União de 10/01/2000, Seção 1, 54. Castro A. (1992), O extrativismo do açai no Amazonas – Relatório de resultados, convênio INPA-CNPq/ORSTOM. Cavalcante P. B. (1976), Frutos comestíveis da Amazônia, 2nd edn Falângola, Belém, PA, Brasil. Cavalcante P. B. and Johnson D. (1977) Edible Palm Fruits of the Brazilian Amazon, Principles, 21, 91–102. Coisson J. D., Travaglia F., Piana G., Capasso M. and Arlorio M. (2005) ‘Euterpe oleracea juice as a functional pigment for yogurt’, Food Res Int, 38, 893–897. Evani S. (2009), ‘Trends in the US Functional Foods, Beverages and Ingredients Market, Canada, Agriculture and Agri-Food Canada’. Available from: http://www.ats.agr.gc.ca/ eve/5289-eng.htm [accessed 19 October 2010]. FAO/WHO (2001) Human Vitamin and Mineral Requirements, Food and Nutrition Division. FAO/WHO/UNU (2007) Protein and amino acid requirements in human nutrition, WHO technical report series. Gallori S., Bilia A. R., Bergonzi M. C., Barbosa W. L. R. and Vincieri F. F. (2004), ‘Polyphenolic constituents of fruit pulp of Euterpe oleracea Mart. (açai palm)’ Chromatogr, 59, 739–743. Figuerola F., Hurtado M. L., Estévez A. M., Chiffelle I., Asenjo F. (2005), ‘Fibre concentrates from apple pomace and citrus peel as potential fibre sources for food enrichment’, Food Chem, 91, 395–401. Hogan S., Chung H., Zhang L., Li J., Lee Y. et al. (2010), ‘Antiproliferative and antioxidant properties of anthocyanin-rich extract from açaí’, Food Chem, 118, 208–214. Homma A. K., Muller A. A., Muller C. H., Ferreira C. A. P., Figueiredo F. J. C. et al. (2005), in Nogueira O. L., Figueirêdo F. J. C. and Muller A. A., Açai, Embrapa Amazônia Oriental, Belém, Brazil, 137 pp. (Sistemas de Produção, 4). IEC (Instituto Evandro Chagas) (2007), Boletim informativo sobre vigilância epidemiológica da doença de Chagas na Amazônia brasileira, Belém, Brazil. Jensen G. S., Wu X., Patterson, K. M., Arnes J., Carter S. G. et al. (2008), ‘In vitro and in vivo antioxidant and anti-inflammatory capacities of an antioxidant-rich fruit and berry juice blend results of a pilot and randomized, double-blinded, placebo-controlled, crossover study’ J Agric Food Chem, 56, 8,326–8,333. Kang J., Li Z., Wu T., Jensen G. S., Schauss A. G. et al. (2010), ‘Antioxidant capacities of flavonoid compounds isolated from Açai pulp (Euterpe oleracea Mart.)’ Food Chem, 122, 610–617. Lagiou P., Samoli E., Lagiou A., Tzonou A., Kalandidi A. et al. (2004), ‘Intake of specific flavonoid classes and coronary heart disease – a case-control study in Greece’, Eur J Clin Nut, 58, 1,643–1,648. Lapointe A., Couillard C. and Lemieux S. (2006), ‘Effects of dietary factors on oxidation of low-density lipoprotein particles’, J Nut Bioch, 17, 645–658.

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Lichtenthaler R., Rodrigues R. B., Maia J. G. S., Papagiannopoulos M., Fabricius H. et al. (2005), ‘Total oxidant scavenging capacities of Euterpe oleracea Mart. (Açai) fruits’, J Food Sci Nutr Int, 56, 53–64. Martin C. A., Almeida V. V., Ruiz M. R., Visentainer J. E. L., Matshushita M. et al. (2006), ‘Ácidos graxos poliinsaturados ômega-3 e ômega-6: importância e ocorrência em alimentos’, Revista de Nutrição, 19, 761–770. Melo C. F. M., Barbosa W. C. and Alves S. M. (1988), Obtenção de açai desidratado, Embrapa-CPATU. 92, Belém, Brazil. Mertens-Talcott S., Rios J., Jilma-Stohlawetz P., Pacheco-Palencia L. A., Meibohm B. et al. (2008) ‘Pharmacokinetics of anthocyanins and antioxidant effects after the consumption of anthocyanin-rich açai juice and pulp (Euterpe oleracea Mart.) in human healthy volunteers’, J Agric Food Chem, 56, 7,796–7,802. Moore H. E. (1973), ‘The major groups of palms and their distribution’, Gentes Herb, 11, 27–141. Nascimento R. J. S., Couri S., Antoniassi R. and Freitas S. P. (2008) ‘Composição em Ácidos Graxos do Óleo da Polpa de Açaí Extraído com Enzimas e com Hexano’, Rev Bras Frutic, 30, 498–502. Nunes M. C. N., Brecht J. K., Morais A. M. M. B. and Sargent S. A. (2005) ‘Possible influences of water loss and polyphenol oxidase activity on anthocyanin content and discoloration in fresh ripe strawberry (cv. oso grande) during storage at 1°C’, J Food Sci, 70, 79–84. Pacheco-Palencia L. A., Hawken P. and Talcott S. T. (2007), ‘Phytochemical, antioxidant and pigment stability of açai (Euterpe oleracea Mart.) as affected by clarification, ascorbic acid fortification and storage’, Food Res Int, 40, 620–628. Pacheco-Palencia L. A., Talcott S. T., Safe S. and Mertens-Talcott S. (2008) ‘Absorption and biological activity of phytochemical-rich extracts from açai (Euterpe oleracea Mart.) pulp and oil in vitro’, J Agric Food Chem, 56, 3,593–3,600. Pires J. M. (1973), Tipos de vegetação da Amazônia, Publicação avulsa do Museu Paraense Emílio Goeldi, Belém, PA, Brazil, 20, 179–202. Pompeu D. R., Silva E. M. and Rogez H. (2009a), ‘Optimisation of the solvent extraction of phenolic antioxidants from fruits of Euterpe oleracea using response surface methodology’, Bioresour Technol, 6,076–6,082. Pompeu D. R. P., Barata V. C. P. and Rogez H (2009b), ‘Impacto da refrigeração sobre variáveis de qualidade dos frutos do açaizeiro (Euterpe oleracea)’ Alim Nutr, Araraquara, 20, 141–148. Pozo-Insfran D. D., Brenes C. H. and Talcott S. T. (2004), ‘Phytochemical composition and pigment stability of açai (Euterpe oleracea Mart.)’, J Agric Food Chem, 52, 1,539–1,545. RDA (Recommended Dietary Allowances) (1997), in Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride, Washington, D.C.: National Academy of Science. RDA (Recommended Dietary Allowances) (2000a), in Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc, Washington, D.C.: National Academy of Science. RDA (Recommended Dietary Allowances) (2000b), in Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids, Washington, D.C.: National Academy of Science. RDA (Recommended Dietary Allowances) (2002), in Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients), Washington, D.C.: National Academy of Science. RDA (Recommended Dietary Allowances) (2004), in Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate, Washington, D.C.: National Academy of Science. Rodrigues R. B., Lichtenthaler R., Zimmermann B. F., Papagiannopoulos M., Fabricius H. et al. (2006), ‘Total oxidant scavenging capacity of Euterpe oleracea Mart. (Açai) seeds

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and identification of their polyphenolic compounds’, J Agric Food Chem, 54, 4,162– 4,167. Rogez H. (2000), Açai: Preparo, Composição e Melhoramento da Conservação. 1st edn, Edufpa, Belém, Brazil. Salgado P. E. T. (2003), in Oga, Seizi (ed.), Fundamentos de Toxicologia Atheneu, São Paulo, Brazil. Sampaio P. B., Rogez H., Souza J. N. S., Rees J. F. and Larondelle Y. (2006), ‘Antioxidant properties of açai (Euterpe oleracea) in human plasma’, in Rogez H. and Pena R. S. (ed.), Olhares Cruzados sobre o Açai, Edufpa, Belém, Brazil, in press. Santana A. C. and Costa F. A. (2009), ‘Mercado do açaí no estado do Pará’ in Rogez H. and Pena R. S. (ed.) Olhares Cruzados sobre o Açai, Edufpa, Belém, Brazil, in press. Schauss A. G., Wu X. L., Prior R. L., Ou B. X., Patel D. et al. (2006a), ‘Phytochemical and nutrient composition of the freeze-dried amazonian palm berry, Euterpe oleraceae Mart. (Açai)’, J Agric Food Chem, 54, 8,598–8,603. Schauss A. G., Wu X. L., Prior R. L., Ou B. X., Huang D. J. et al. (2006b), ‘Antioxidant capacity and other bioactivities of the freeze-dried amazonian palm berry, Euterpe oleraceae Mart. (Açai)’, J Agric Food Chem, 54, 8,604–8,610. Silva A. E., Silva L. H. M. and Pena R. S. (2008) ‘Comportamento higroscópico do açaí e cupuaçu em pó’, Braz J Food Tecnol, 28, 895–901. Tonon R. V., Brabet C. and Hubinger M. D. (2010), ‘Anthocyanin stability and antioxidant activity of spray-dried açai (Euterpe oleracea Mart.) juice produced with different carrier agents’, Food Res Int, doi: 10.1016/j.foodres.2009.12.013. Uhl C. and Dransfield J. (1991) Genera Palmarum: a classification of palms based on the work of Harold E. Moore Jr., Allen Press, Kansas, USA, 354–357. Wolfe K. L., Kang X., He X., Dong M., Zhang Q. et al. (2008), Food Chem, 56, 8,418–8,426.

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2 Acerola (Malpighia emarginata DC.) M. Mohammed, University of the West Indies St Augustine Campus, Trinidad

Abstract: The Acerola, or West Indian cherry, which belongs to the Malpighiaceae family, is native to the West Indies and tropical South America. Fully ripe fruits have the highest vitamin C content of all fruits, ranging from 1,000 to 2,000 mg 100g−1. Processing the fruit into juice results in little loss of vitamin C; consequently, the juice is used to improve the ascorbic acid content of other fruit juices. Fruits are ready for harvesting when they turn pink or red. They should not be allowed to ripen fully on the trees because they deteriorate rapidly. The fruits are highly perishable after harvest. Postharvest losses are mainly due to physical injuries arising from abrasion, puncture and compression. Shelf life is also limited owing to pests and diseases. The fruits have a very thin skin and lose moisture very rapidly when stored at high temperatures and low relative humidity. Fruits are also susceptible to chilling injury during low temperature storage. Key words: Malpighia emarginata, acerola, Barbados cherry, processing, postharvest.

2.1

Introduction

2.1.1 Origin, botany, morphology and structure The acerola, which is also called ‘Barbados cherry’, ‘West Indian cherry’, ‘cereza’, ‘cerise des Antilles’ and ‘sweet kersie’ belongs to the genus Malpighia. In the past, according to Carrington and King (2002), the plant was known by the synonyms Malpighia glabra L. and Malpighia punicifolia L., but recent taxonomic work has resulted in the acceptance of Malpighia emarginata DC. as its scientific name. It is native to the West Indies and tropical America, but is now cultivated throughout the tropics and in subtropical areas such as Florida, Australia and Israel. Acerola can be found from South Texas, through Mexico and Central America and more recently, it has been introduced in subtropical areas throughout the world such as parts of Asia, India and South America. Some of the largest plantations are in Brazil, particularly in the Northern region of the country, and currently, Brazil is the largest producer of acerola in the world (de Assis et al., 2008).

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The plant is either a large, bushy shrub or a small tree that can attain an average height of 3 to 5 m. It has a short, slender trunk that is 0.5 to 1 m high and 7 to 10 cm in diameter. The branches are erect to spreading, forming a dense canopy, and the bark of the tree is slightly rough and grey-brown in colour. The evergreen leaves are hairless, glossy and dark green when mature and are generally small: 2 to 7 cm long and 9.5 to 40 cm wide. The flowers are borne in inflorescences that are sessile or have short peduncles, and are pink with five-fringed petals. It is a hardy plant capable of growing in both tropical and subtropical climates. It can resist temperatures close to 0°C (Neto and Soares, 1994) but is well adapted to temperatures around 26°C. It grows and produces well when rainfall is between 1200 and 1600 mm per year. Irrigation is required in areas with little rainfall. Plants can be grown in sandy soils as well as clay soils: a soil with average fertility composed of a mixture of sand and clay seems to be optimal for its cultivation. Flowering and concomitant fruiting can occur throughout the year, but typically occur in cycles associated with rainfall. Usually, they take place in 25-day cycles, up to eight times per year. Plants grown in dry areas with an annual rainfall around 1480 mm in irrigated fields produce between 2.01 and 27.11 kg per tree in four crops in a year. The plant has also been cultivated as an ornamental in subtropical areas where it flowers from April to November (Johnson, 2003). The fruit is a thin-skinned, three-lobed drupe, globose, up to 2.5 cm in diameter and weighing 2 to 10 g. It ripens to a bright red colour and the pulp is orange, very juicy and acid to sub-acid in flavour. The three small seeds bear wings that give them a triangular shape. 2.1.2 Worldwide importance and culinary uses The West Indian cherry is consumed fresh as a dessert, either whole or cut into halves and either served by itself or in combination with other fresh-cut fruits as a fruit salad. It adds colour and flavour to fruit salads and also prevents discolouration in other fruits such as bananas, due to its high vitamin C content. Fruits at the ripe and full-ripe stages of maturity can also be deseeded and eaten sprinkled with sugar or salt to modify the acidity of the particular cultivar available. Due to its highly perishable nature it is also processed into a range of value-added products such as juice (integral, concentrated and lyophilized), juice blends, fruit punches, nectars, soft drinks and fruit conserves (although the pasteurized canned juices do not keep well, are unattractive and rapidly lose their nutritional value). It is also used as an ingredient in yoghurts, sodas, jellies, icecream and bakery products, sold as a nutraceutical and consumed for medicinal purposes (Mezadri et al., 2006). Owing to the wide range of uses identified above, demand for the fruit outstrips supply. Demand for the pulp in Caribbean and Western European markets is particularly promising. Acerola is attractive to customers who prefer natural products over synthetic ones (for example it is a popular natural source of vitamin C). As it can be sold in both fresh and processed forms, the fruit is an excellent source of income to producers and agro-processors. The fruit is also a perennial, producing all year

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long when cultivated in irrigated fields. Harvesting and marketing of the fruit provide employment as well as continuous income throughout the year. 2.1.3 Composition, nutritional value and health benefits The West Indian cherry is rich in vitamin C, pectin and pectolytic enzymes, carotenoids and fibre, and contains small amounts of vitamins and several bioactive substances, such as thiamin, riboflavin, niacin, proteins and mineral salts, mainly iron, calcium and phosphorus according to de Assis et al. (2008), as shown in Table 2.1. Porcu and Rodriguez-Amaya (2006) investigated the variation in the carotenoid composition of acerola fruits and found that neoxanthin, violaxanthin, lutein, β-cryptoxanthin, α-carotene and β-carotene were present. When fully ripe the ascorbic acid content of the fruit ranges from 1000 to 2000 mg 100g−1 and the pulp of partially ripe fruit can have values as high as 4500 mg 100g−1 (de Assis et al. 1998). Therefore, this fruit is recognized as the best natural source of vitamin C. In comparison with synthetic ascorbic acid, the vitamin C produced by this fruit is better absorbed by the human body. In fact, humans can only absorb 50% of synthetic vitamin intake compared to that of natural vitamins (Byrne, 1993). The high vitamin C content of acerola fruits enables it to be used for the production of vitamin C concentrate for pharmaceutical purposes or enrichment of industrialized foods. Vitamin C plays a key role in the biosynthesis of collagen, carnitine, neurotransmitters, corticoids and catecholamines as well as in the synthesis and maintenance of tissues including the formation of bones, teeth and muscles (Araujo and Minami, 1994; Naidu, 2003). In a study reported by Johnson (2003), it was found that infants consuming apple juice supplemented with acerola showed average or above average growth and development for their age and weight. Vitamin C levels in the blood were

Table 2.1 Food value of acerola fruit Proximate composition (g 100 g−1)

Fruit Juice

Energy

Water

Protein

Total lipid

Ash

Carbohydrate

32 23

91.41 94.30

0.40 0.40

0.30 0.30

0.20 0.20

7.69 4.80

Total dietary fibre 1.1 0.3

Total sugars – 4.50

Minerals (mg 100 g−1) Fruit Juice

Calcium Iron Magnesium Phosphorus Potassium Sodium Zinc 12 0.20 18 11 146 7 0.10 10 0.50 12 9 97 3 0.10

Copper Selenium 0.086 0.6 0.086 0.1

Vitamins (mg 100 g−1) Fruit Juice

Thiamin 0.020 0.020

Riboflavin 0.060 0.060

Niacin 0.400 0.400

Pantothenic acid 0.309 0.205

Vit. B-6 0.009 0.004

Source: de Freitas et al., (2006).

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Folate 14 14

Vit. A 767 509

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higher for all infants after the acerola/apple juice was introduced in the diet. No allergic reactions occurred, suggesting that acerola mixed with apple juice is an acceptable alternative to orange juice for obtaining vitamin C from the diet. Acerola is a remarkable functional food resource. Santini and Huyke (1956), in their pioneering study, identified polyphenols as a colour-changing agent in acerola juice. According to Hanamura et al. (2008), though, it is only recently that the physiological effects of polyphenols and other functional constituents of acerola have become the subject of investigation by the scientific community. Hanamura et al. isolated three polyphenols from acerola fruits: cyaniding-3-α-οrhamnoside (C3R) and pelargonidin-3-α-ο-rhamnoside (P3R) as anthocyanin, and quercetin-3-α-ο-rhamnoside (quercitrin; Q3R). These acerola polyphenols have an antiperglycemic effect, the mechanism of which was considered to be both the suppression of intestinal glucose transport and inhibition of α-glucosidase and thus beneficial to human health. The high antioxidant content of acerola extracts has contributed to their use for the prevention of age-related diseases such as hypertension and cancer (Filgueiras et al., 2007). Filgueiras et al. (2007) evaluated the antioxidant capacity of fruits from five clones of ascerola. They stated that although the anthocyanin content measured was 2.7 to 7.8 mg 100g−1 FW (fresh weight), much lower than that of berry fruits, the phenolic content was about three times as high, that is, 3300 to 4400 mg 100g−1 FW and the vitamin C content varied from 1100 to 1400 mg 100g−1 FW. They concluded that the ORAC (oxygen radical absorbance capacity) value of acerola was 239 to 383 f.1M TE/g DW (Trolex equivalent per gram dry weight). This is significantly higher than that of strawberry and blackberry. The same authors reported that acerola extracts diluted 1:100 and 1:200 significantly inhibited the relative activity of carcinogenesis related Activator Protein-1 (AP-1) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) transcription factors induced both by tissue plasminogen activator (TPA) and Ultra Violet B type rays (UVB) (Filgueiras et al. 2007). In addition, Johnson (2003) reported that in the presence of acerola cherry extract, soy and alfalfa phytoestrogen extracts prevented the oxidation of low-density lipoproteins, thus reducing an important risk factor in coronary heart disease: an extremely beneficial outcome for the health of postmenopausal women. Acerola is also reported to have anti-fungal properties (de Assis et al., 2008).

2.2

Fruit growth and development

2.2.1 Fruit growth, and maturation Carrington and King (2002) provided a comprehensive account of growth, development and ripening of West Indian cherries. According to these authors fruit growth is biphasic: the majority of the size increase occurred during the initial 14 days post-anthesis; a second limited phase of growth followed over the subsequent ten days. This double sigmoid pattern of growth articulated by Carrington and King (2002) was confirmed by measurements of fresh weight and dry weight.

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According to Carrington and King (2002), Monselise’s (1986) theory that the biphasic growth curves obtained for blueberry and peach are indicative of resource diversion to develop a substructure (such as the endosperm or endocarp) during the transition period between the two growth phases is not relevant for acerola fruits for two reasons. First, the embryonic development 3 days after pollination in acerola fruits attained morphological maturity around the time of the transition period, and secondly, the growth of the pyrene (comprising the seed and endocarp) mirrored the growth of the whole fruit on the basis of fresh and dry weight (Carrington and King, 2002). Carrington and King (2002) also contradicted the histological study by Miyashita et al. (1964), which suggested that the pericarp in acerola grew solely by cell enlargement. Rather, Carrington and King (2002) provided evidence to show that cell division occurred in the exocarp and mesocarp, but was limited to the earliest phase of fruit development where cell numbers increased exponentially up to eight days post-anthesis, and ceased thereafter. Full-sized, green fruit turned cream at the distal end about 18 days post-anthesis (Carrington and King, 2002). According to these authors, fruits at this stage do not ripen off the tree, so this colour break is a useful index of horticultural maturity. Carrington and King (2002) further stated that by 20 days post-anthesis fruits changed to a peach colour and by 22 days fruits were orange-red. This is comparable with the 21 to 25 days development period articulated by Miyashita et al. (1964). Changes in skin colour correlate with chemical changes in the fruit. Guadarrama (1984) and Alves et al. (1992) associated the degradation of chlorophylls at the early stages of fruit maturity with a concomitant rise in carotenoids, with trans-βcarotene being the main carotenoid. Towards the later growth stage coinciding with physiological maturity, anthocyanins were dominant, and therefore the full red skin colour developed. At this stage the anthocyanins increased strongly to become the major polyphenols (Hanumura et al., 2008). Other chemical changes associated with advancing fruit maturity were investigated by Vendrami and Trugo (2000), who indicated that while titratable acidity, soluble solids and sugars increased, vitamin C and proteins decreased as fruit matures. The same authors identified the emission of volatiles at different stages of maturity. They identified 31 compounds in the mature red fruits, such as acethyl-methyl-carbinol, 2-methyl10-propyl-acetate, limonene, E-Z-octenol, ethyl hexanoate, isoprenyl butyrate and acetofenone; 23 in the intermediate yellow stage, such as methyl hexanoate, 3-octen-1-ol and hexyl butyrate; and 14 in the immature green stage, such as methyl-propyl-ketone, E-Z-hexenyl-acetate and 1-octadecanol. Despite this, fruit aroma according to Carrington and King (2002) was considered too subtle to be used as maturity indices in acerola. 2.2.2 Respiration, ethylene production and ripening Carrington and King (2002) and Alves et al. (1995) investigated the respiratory pattern of acerola fruits and confirmed its climacteric responses. Carrington and King (2002) reported that respiration rose dramatically as fruits turned orange-red and peaked around 3 days postharvest. They also indicated that ethylene evolution

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followed a similar pattern with the climacteric peak occurring two to four days postharvest. Based on carbon dioxide production acerola fruits can be said to have an extremely high respiratory rate, which is consistent with its very perishable nature. In contrast, relatively low rates of ethylene were measured (Carrington and King, 2002). Fruit ripening in acerola is accompanied by major physicochemical changes. Weight, thickness and height increased during maturation and ripening, as well as levels of carotenoids, soluble sugars and total sugars and the soluble solids/titratable acidity ratio (Table 2.2). Chlorophyll, titratable acidity and vitamin C decreased, while pH showed few changes. Hanamura et al. (2008) investigated ripening changes in five cultivars. For the purposes of the study, they classified the different stages of maturity as follows: green (under ripe), yellow (ripe), red (fully ripe) and purple (overripe). They concluded that the amounts of total polyphenols, malic acid and sugars, as well as total water-soluble solid, increased with the development of fruit ripening in cultivars ‘BOK’ and ‘NRA309’. In the latter cultivar, sugar contents significantly increased from green to purple stages of fruit maturity (total sugar contents: 6.8 g kg−1 for green immature fruits, 23.2 g kg−1 for purple overripe fruits) compared to the former cultivar, where total sugar contents were 16.0 g kg−1 for green immature fruits and 31.1 g kg−1 for fully ripe fruits. On the other hand, the rate of increase of malic acid content was more significant in cultivar ‘BOK’ (2.7g kg−1 for green fruits and 9.7g kg−1 for red fruits) than in cultivar ‘NRA 309’, which gave 4.5 g kg−1 for green fruits and 8.4g kg−1 for red fruits. Vitamin C content, on the contrary, decreased with the development of fruit ripening in both cultivars, from

Table 2.2 Average values of some physical parameters in fruit of acerola genotypes studied in Brazil Genotype

°Brix(TSS)

% Titratable acidity(TA)

TSS: TTA

vit. C mg/100 g−1

Acer-1 Acer-2 Acer-3 Acer-4 Acer-5 Acer-6 Acer-7 Acer-8 Acer-9 Acer-10 Acer-11 Acer-12 Acer-13 Acer-14 Acer-15 Acer-16

6.35de 6.65cde 6.90abcd 6.80bcd 6.40de 6.90abcd 5.80efg 5.40fg 7.55ab 7.75a 6.85bcd 5.25g 6.25def 7.35abc 6.55cde 5.80efg

0.63g 0.72efg 0.73efg 0.69fg 0.73efg 0.80def 1.05ab 0.97bc 0.75ef 0.82de 0.78ef 0.90cd 1.15a 0.37h 0.73efg 0.78ef

9.97b 9.20bc 9.46bc 9.87b 8.95bc 8.57cd 5.53e 5.59e 10.03b 9.43bc 8.76bc 5.81e 5.44e 19.39a 8.95c 7.38d

665.22de 887.61abcd 1028.95ab 772.51bcde 888.39abcd 751.44cde 1141.21a 967.59abc 758.85cde 731.54cde 800.21bcde 880.16abcd 928.57abcd 723.74cde 575.48e 1127.55a

Source: Cavalcante et al., 2007.

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25.7 to 23.5 g kg−1 for cultivar ‘BOK’, and from 26.0 to 20.0 g kg−1 for cultivar ‘NRA309’. In the same investigation, the two cultivars showed a similar pattern of change in the contents of individual polyphenolic compounds during maturation and ripening. Accordingly, the amount of anthocyanins (C3R and P3R) and Q3R increased with the development of fruit ripening in both cultivars. In particular, the amount of both anthocyanins dramatically increased from yellow to red fruits in both cultivars. In fruits of the cultivar ‘NRA309’, the amount of both anthocyanins further increased more than two times from fruits at the red stage of maturity to those at the purple stage of maturity. On the contrary, phenylpropanoids decreased with the development of fruit ripening in both cultivars from 61 to 24 mg kg−1 for ‘BOK’ and from 111 to 51 mg kg−1 for ‘NRA309’. 2.2.3 Maturity indices Physicochemical parameters are important indicators of fruit maturation and fruit internal and external quality. They are also significant for customer satisfaction. Change in skin colour is a major criterion used to assess acerola maturity. A classification of maturity and ripening stages is presented in Plate IIa (see colour section between pages 244 and 245; Mohammed, 1996). Stage 1 consists of immature fruits with a bright glossy green colour, stage 2 has 95% light yellow and 5% peach skin colour, stage 3 fruits has 85% peach and 15% shade of pink colour, stage 4 has 60% pink and 40% red skin colour, stage 5 has a uniform red skin colour and stage 6 has a darkish-red or purple skin colour. As already mentioned, full-sized, green fruit turn cream at the distal end about 18 days post-anthesis (Carrington and King, 2002). According to these authors, fruit at this stage do not ripen off the tree, so this colour break is a useful index of horticultural maturity. Although fruits are round at all stages of maturity, fruit size varied according to genetic lines, growth and environmental conditions and therefore is not a consistent and reliable maturity index. Fruits harvested at the pink stage of maturity have at least 6.5% soluble solids. Vitamin C loss during maturation can be 33% up to the pink stage and reach as much as 45% when dark red.

2.3

Preharvest factors affecting fruit quality

The genetic potential of the acerola plant along with the edaphoclimatic conditions strongly influence the productivity of the tree and characteristics of the fruit it produces. The quality of fruits prior to harvest depends on the cultivar, climatic conditions, soil type, irrigation, level of sunlight, way in which the plants are spaced and pruned and pest and disease control. Significant variation in fruit quality can be observed among different production areas. Acerola fruit fresh weight and size vary according to cultivar and location (Table 2.3). Strong evidence of this can be found in the investigations conducted by Cavalcante et al. (2007), Semensato and Pereira (2000), Nogueira et al. (2002) and Roberts-Nkrumah et al. (1994). The lowest average fruit weight observed by

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Table 2.3 Average values of some chemical parameters in fruit of acerola genotypes studied in Brazil Genotype

Width (cm)

Length (cm)

Weight (g)

Pulp (%)

Acer-1 Acer-2 Acer-3 Acer-4 Acer-5 Acer-6 Acer-7 Acer-8 Acer-9 Acer-10 Acer-11 Acer-12 Acer-13 Acer-14 Acer-15 Acer-16

1.99bcd 1.94bcde 2.07abc 1.92bcde 2.06bcd 1.99bcd 1.88cde 1.97bcde 1.81de 2.00bcd 1.73e 2.00bcd 2.32a 1.94bcde 2.17ab 2.07abc

2.34bcd 2.24d 2.35bcd 2.36bcd 2.42bcd 2.33bcd 2.32bcd 2.40bcd 2.28cd 2.53ab 1.99e 2.43bcd 2.70a 2.43bcd 2.47abc 2.50abc

6.35c 6.02c 6.82c 7.25bc 6.42c 6.29c 5.80cd 6.56c 7.12bc 8.62ab 4.24d 6.39c 9.94a 6.04c 7.08bc 7.28bc

50.02bcdef 48.42cdef 46.54defg 50.48bcdef 45.57defg 49.72bcdef 44.44efg 52.41abcde 42.26fg 42.89fg 38.58g 54.36abcd 61.21a 41.44fg 57.52abc 57.83ab

Source: Cavalcante et al., 2007.

Cavalcante et al. (2007) was 4.24 g (cv. Acer-11). This was above the 3.52 g reported by Semensato and Pereira (2000) and Roberts-Nkrumah et al. (1994), but below the 7.81 g and 6.59 g averages, respectively, for the cultivars UFRPE-7 and UFRP-8 mother plants obtained by Nogueira et al. (2002). Cavalcante et al. (2007) found significant differences in length, width and pulp percentages between 16 acerola genotypes (Table 2.3). According to this analysis, fruit length was greater than fruit width, thereby characterizing the fruit as subglobose in shape. The cultivar Acer-11 had the smallest fruits (1.99 cm in length and 1.73 cm in width) while genotype Acer-13 had the largest fruits (2.70 cm in length and 2.32 cm in width). Fruit lengths were generally greater than 1.62 to 2.07 cm, the range reported by Semensato and Pereira (2000) but compatible with the UFRPE-7 mother plant, which has a 2.3 cm average (Norueira et al., 2002). In any case, all the genotypes evaluated by Cavalcante et al. (2007) had fruit length above the minimum (1.5 cm) demanded by the industry. Genotype variations for pulp percentage are also given in Table 2.3 (Cavalcante et al., 2007). The pulp percentage ranged from 38.58% for Acer-11 to 61.21% for Acer-13 which is close to the 47.8 to 58.9% range accounted for by Gomes et al. (2000) and the 40.83 to 65.63% obtained by Semensato and Pereira (2000) but lower than the 59 to 75% shown by Arostequi and Pennock (1995) and higher than the 30% average reported by Lopes et al. (2001). The changes associated with the composition in acerola fruit in relation to cultivar, growing region and maturity were also articulated in the study reported by Hanamura et al. (2008). Thus, in terms of growing regions, cultivar ‘Vietnam’, vitamin C and polyphenol concentrations were lower in this fruit compared to

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those found in fruits from other growing regions. Noteworthy, was the amino acid composition in this cultivar, which showed an extremely high concentration of proline (858 mg kg), almost half of the total amino acid content (1,733 mg kg). Also, this fruit contained a high level of phenylpropanoids, amounting to 30% of total polyphenols. The distinct compositional profile so obtained, including high sugar and low vitamin C contents as well as exceptionally high proline content, which is associated with a sweet taste, appeared to be strongly correlated with the organoleptic characteristics of this fruit. It has been reported that the taste threshold value of proline is 3.0 g L−1 at pH 6 to 7 and 875 mg L−1 at pH 4.3 (Schoenberger et al., 2002). ‘Vietnam’ cultivar fruit contained approximately 800 mg kg−1 (edible portion) of proline whereas the pH value of acerola juice was 3.3, thereby confirming that proline contributes to the sweet taste of this fruit. High variability in fruit quality has been reported in Brazilian acerola crops, especially those propagated by seeds. Fruit size and composition quality are not only affected by lack of orchard uniformity, but also by environmental factors such as excessive rain, and by preharvest factors such as irrigation, fertilization, pest and disease control. Variations in soluble sugars in acerola fruits can vary from 5 to 12 °Brix due to excessive rain or irrigation, which could dilute cell juice thereby reducing the amount of soluble solids and vitamin C (Alves et al., 1999). Preharvest factors could also account for the variation in vitamin C in acerola fruits from 0.8 to 3.5%. A peak is reached approximately 16 to 18 days after anthesis and the concentration falls to nearly 50% of the peak amount when maturation is completed. Fruits from seed propagated plants for example have lower amounts than those from asexually propagated plants. In the shaded side of fruits there was a significant reduction in vitamin C content before harvest, whilst exposure to solar radiation for more than four hours after harvest resulted in substantial losses (Alves and Menezes, 1994; Alves et al., 1992, 1995; Nakasone et al., 1966). Fruits and flowers at different stages of development are present simultaneously on the acerola plant. Therefore there is the risk that chemicals used for pest and disease control to improve plant health and productivity increase levels of pesticide residues in fruit.

2.4

Postharvest factors affecting quality

2.4.1 Temperature management Postharvest temperature management, to minimize the rate of respiration and ripening in acerola, is very important. Maciel et al. (1999) reported that acerola fruits harvested at the pink stage of maturity stored at room temperature maintained marketable quality for two to three days when wrapped in PVC (polyvinylchloride) film. However when fruits were stored in PVC wrapping at 7 to 8°C and 80 to 90% relative humidity, shelf life advanced to a week without any losses in vitamin C (Maciel et al., 1999; Mohammed, 1996) The storage temperature should not be too low, though, as acerola fruit are susceptible to chilling injury

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when stored at temperatures below 5 to 6°C, with the damage becoming more visible when they are stored in air where the relative humidity is below 85% (see section 2.5.1). 2.4.2 Physical damage Acerola fruits have a very thin skin, which offers little resistance against most types of physical injury. Fruits are particularly susceptible to abrasion caused by the fruit rubbing against each other. Physical injuries which are significant sources of postharvest losses are: punctures caused by fingernails during harvesting and other postharvest operations and compression of fruits packed in deep containers caused by the weight of the fruit in the layers above them. If the fruit skin is damaged then the fruit pulp deteriorates rapidly. 2.4.3 Water loss When the types of physical damage outlined above occur, the level of transpiration increases. Despite the fruits having a natural gloss due to deposition of cuticular wax on the fruit skin, if fruits are stored in less than 85% relative humidity, moisture loss is high leading to shrivelling and a deterioration in appearance and therefore marketable quality. A 3-minute dip in a cassava starch suspension reduced moisture loss. The effect is more pronounced if the dipped fruits are stored at a refrigerated temperature of 7 to 8°C in an atmosphere of at least 85 to 90% relative humidity (Maciel et al., 2004). 2.4.4 Atmosphere Cerqueira et al. (2009) investigated the suitability of novel galactomannans as edible coatings for several tropical fruits including acerola. Edible coatings act by creating a modified atmosphere surrounding the commodity, similar to that achieved by controlled atmosphere or modified atmospheric storage conditions. Accordingly, the modified atmosphere created by the edible coatings protects the fruit from the moment it is applied until it reaches the final consumer. However, the effectiveness of edible coatings for fruit preservation depended on the control of the wettability of the coating in order to ensure a uniformly coated surface, permeability and mechanical properties in order to decrease the water loss in the fruit, to decrease oxygen permeability (since lower oxygen concentration prolongs the shelf life by delaying the oxidative breakdown of complex substrates) and also to reduce the production of ethylene, which is a key element of the ripening and maturation process. In their study they used coatings of galactomannans from two plant species, Adenanthera pavonina and Caesalpinia pulcherrima, both from the Leguminosae family to determine their impact on the fruit surface properties using different galactomannan solutions at 0.5, 1.0 and 1.5% respectively with glycerol at 1.0, 1.5 and 2.0% respectively to test their wettability status. For solutions with a better wettability status, films were casted and water vapour

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permeability, oxygen permeability, carbon dioxide permeability, tensile strength and elongation at break were determined. Taking into account the surface and permeability properties of the films obtained the best formulation for acerola fruits was 0.5% Adenanthera pavonina galactomannan and 1.0% glycerol. The authors (Cerqueira et al., 2009) recommended that the formulation should be applied either by immersion or sprayed on the fruits and allowed to dry at room temperature for 3 hours. Storage of acerola fruits coated with 1 and 2% cassava starch edible film at 10°C resulted in fruits with an increased shelf life of up to 15 days with acceptable quality characteristics. It was also found that fruits subjected to prestorage coating of a 1% cassava starch biofilm maintained the highest ascorbic acid content. Cassava starch, according to Maciel et al. (2004), improved the fruit’s appearance. They dipped different replicates of orange-red acerola fruits at 1, 2, 3 and 4% (w/v) in a cassava starch suspension for 3 minutes and examined quality attributes during storage at 10 and 22°C and at 85% relative humidity for up to 15 days. Their results showed that the use of cassava biofilm at 1% on acerola fruits maintained the highest ascorbic acid content and the temperature of 10°C extended storage life compared to their counterparts stored at 22°C. Fruits coated with 1 and 2% cassava biofilm had acceptable quality characteristics after 15 days at 10°C (Maciel et al., 2004). The use of PVC film to reduce transpiration and the creation of a suitable modified atmosphere at 7 to 8°C and 85 to 90% relative humidity extended shelf life of fruits more effectively than fruits stored in air. Under these conditions and packaging, acerola fruits did not experience a significant reduction in juice quality yield. Also, ascorbic acid retention is higher in a modified atmosphere, compared to ambient temperature, and this was attributed by Alves et al. (1995) to lower oxygen availability inside the package. The effect of controlling or modifying atmosphere on ascorbic acid content depended on the crop, temperature and atmospheric gas levels and, although low oxygen helped to reduce losses, high carbon dioxide inside the package could hasten losses as reported for other fruits like bananas and apples (Watada, 1987).

2.5

Physiological disorders

2.5.1 Chilling injury As already mentioned, fruits are susceptible to chilling when stored at temperatures below 5 to 6°C with symptom expression becoming more visible when stored in air where the relative humidity is below 85%. Major symptoms of chilling injury damage include pitting, surface discolorations and occurrence of secondary infections. The randomly scattered pits eventually coalesced upon prolonged storage below 7 to 8°C to form more distinct larger depressions characterized with dark brown discolorations on the fruit surface (Plates IIb, IIc: see colour section between pages 244 and 245). These symptoms were visible after 4 to 5 days at 4 to 5°C when stored in air, and become more severe when fruits were transferred

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for an additional day at 20°C. However, under similar storage conditions, fruits sealed in low-density polyethylene bags, these symptoms were not visibly apparent and this is undoubtedly related to the saturated microenvironment and modified atmosphere created within the sealed bags (Mohammed, 1996). 2.5.2 Other physiological disorders Other physiological disorders affect acerola fruits. They can become malformed due to damage by sucking insects or nutritional imbalances. They are also susceptible to heat injury, which can be caused by overly dense canopies on the trees, trees spaced too close together or inadequate pruning. Heat-injured fruit usually have poor colour development, scalds and are smaller than usual.

2.6

Pathological disorders and pests and their control

Fruits are susceptible to fungal diseases such as anthracnose caused by Collectotrichum gloeosporioides, as well as bacterial diseases such as bacterial soft rots. Leaf spotting by the fungus Cercospora bunchosiae is a major disease in Florida, Puerto Rico, and Hawaii. Green scurf, identified by the algae, Cephaleuros virescens, occurred in Puerto Rico. Sooty mould is common where the plants are not effectively spaced and pruned. A major obstacle in the cultivation of acerola is the tree’s susceptibility to the root-knot nematode, Meloidogyne incognita var. acrita, especially in sandy soils (Morton, 1987). The nematode can be controlled by soil fumigation, mulching and regular irrigation. The burrowing nematode Radopholus similis can also affect healthy trees, significantly reducing fruit yield. A number of other pests has been identified, including the wax scale insect, which attacks the foliage, and the mango scale insect, whiteflies, the leaf roller and aphids. In Guatemala, the aphid Aphis spiraecola attacks the leaves and young, tender branches. In Puerto Rico, the tree is also damaged by the blue chrysomelid of acerola, Leucocera laevicollis. Some fruits may become misshapen due to the stinkbug. The major pest in Florida is the Caribbean fruit fly, Anastrepha suspensa, which attacks more acidic fruits. In Guatemala, a fruit worm, Anthonomus florus, deposits its eggs in the floral ovary and also on the fruits. The larvae then usually feed inside the fruits causing them to become deformed. Measures taken against this predator include incineration of all fallen, infested fruits and the elimination of all related species that serve as hosts (Morton, 1987).

2.7

Postharvest handling practices

2.7.1 Harvest operations Acerola plants originating from asexual or seed propagation begin fruiting in the first and second years respectively after planting. Fruiting occurs three to four

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times a year (Alves et al., 1999). In Puerto Rico, up to seven production peaks were reported (Simao, 1971). In other places such as in North East Brazil, noted for its high light intensity and temperatures, irrigated plants are known to fruit in less than a year, to produce almost continuously throughout the year. When selecting a harvest date for acerola fruit, their intended purpose must be taken into account. When they are to be eaten as a dessert, acerola fruit should be harvested at the ripe or fully ripe stage of maturity. When they are to be processed into pulp or juice, the fruit can be harvested when they are turning from yellow to red. Red fruits are preferable since at this stage of maturation they should have reached their maximum sugar content and lowest acidity, however care needs to be taken as fruits at this red stage are more prone to physical injury and also contain less vitamin C. When fruits are to be used in the manufacture of powdered products such as pharmaceuticals or concentrates for food enrichment, for which vitamin C content is the most important characteristic, fruit should be harvested at the beginning of the period of maturation. The tree is well known for its ability to fruit continuously over prolonged periods. Therefore harvesting can be scheduled either daily, every other day or even every three days in order to minimize losses from fallen fruits. Harvesting is usually manual and is preferably carried out in the cooler parts of the day, such as in the early morning, late evening or even during the night. Contact between the fruit and the palm of the harvesters’ hands should be avoided because the heat generated from the hand may increase fruit temperature and its rate of metabolism. Fruit destined for processing can be shaken from the trees and then caught on sheets above the ground. Maintaining the cool chain to minimize the rate of respiration is of paramount importance. Direct exposure of fruit to the sun’s radiation can also result in significant losses of vitamin C (Nakasone et al., 1966) and also water loss. Fruit can be protected from the sun by placing it under the canopy of the plants or in a ventilated shed until transportation to the packinghouse. Ideally, fruits should be transported in refrigerated trucks where the temperature is set at 7 to 8°C and the relative humidity is at 90 to 95%, and later subjected to room cooling to remove field heat. In the absence of such facilities fruit should be transported in covered vehicles, preferably with a light coloured canvas with adequate free space between the cover and the fruit for ventilation. Mohammed (1996) recommended transporting the fruit within 3 hours of harvest in shallow plastic crates covered with a light coloured damp cloth to minimize water loss and vitamin C loss. Transportation of fruit filled containers in the early morning or late evening or night should be encouraged in order to take advantage of cooler ambient conditions. It should also be remembered that fruits should not be stored in refrigerated rooms or in reefer containers at temperatures below 5°C because chilling injury would occur. When mature fruits are to be sold in distant markets, they need to be packed in cartons no more than 15 cm deep, so that the weight of the upper layer does not damage the lower layers. The cartons need to be constructed with a shoulder strap so that their transfer, loading and unloading is as comfortable for the worker as

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possible so that fruit damage due to excessive handling can be avoided. Whatever type of harvesting container is used, the use of plastic foam is recommended to avoid compressing fruit against the edges of the containers. Fruit containers should be stacked so that the bottom of a container is not in contact with the fruit inside the container underneath, and the boxes or crates must be arranged so that ventilation is not impaired. 2.7.2 Packinghouse practices Upon arrival at the packinghouse, fruit should be emptied in tanks containing cold sanitized water (5 to 10 ppm of free chlorine) to remove dust, pesticides residues and debris (Mohammed, 1996). Fruits are then placed on conveyor belts and are inspected to eliminate defective fruits, such as those that are misshapen, immature, decayed or physically damaged. In the inspection procedure fruits are also graded according to uniformity in size and skin colour. Alternatively, tanks with cold water (7 to 8°C) may be used to hydrocool graded fruits. At all times the water must be chlorinated (5 to 10 ppm free chlorine) to prevent infection by fungi such as Alternaria spp., Fusarium spp., Aspergillus spp. and Penicillium spp. 2.7.3 Control of ripening and senescence In general, ripening leads to the production of an attractive, ripe, seed-bearing fruit. The ripening stage is characterized by active cell division and expression leading to the formation of a mature fruit. Koura et al. (2002) provided valuable insight on hormonal influences on fruit set and control of ripening when they investigated the effects of aminoethoxyvinylglycine (AVG), an inhibitor of ethylene biosynthesis, gibberellic acid (GA3), 4-Chloro-Phenoxy-Acetic acid (4-CPA) and 2-chlorophosphonic acid (Ethephon) on fruiting and fruit ripening of acerola fruits (Table 2.4). Their study indicated that the untreated control fruit attained a deep red colour (a* value >30) rapidly after 2 days and fruit drop was completed after 4 to 7 days. Table 2.4 Effects of 2-aminoethylvinylglycine (AVG) and 2-chloroethylphosphonic acid (Ethephon) applied at the start of coloration on the quality attributes of acerola fruit Treatment

ND*

Control 4.8 ± 0.3 Ethepon (100 ppm) 3.1 ± 0.4 AVG (100 ppm) 6.4 ± 0.6

Fruit wt (g) Juice yield/ °Brix fruit (%)

Diameter (cm)

5.86 ± 3.3

Colouring (%)

46.1 ± 3.3

7.1 ± 0.6

2.46 ± 0.05 90.0 ± 8.4

5.61 ± 0.06 39.5 ± 3.1

7.4 ± 0.6

2.19 ± 0.06 72.5 ± 6.8

5.77 ± 0.08 45.0 ± 4.4

8.3 ± 0.07

2.29 ± 0.06 97.5 ± 1.2

Note: *The number of days from treatment day to natural fruit drop day. Source: Koura et al., 2002.

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Ethephon (100 ppm) accelerated colouration and abscission: treated fruit turned a deep red colour in one to two days and abscissed completely after about three to five days. By comparison, AVG (100 ppm) delayed colour change in the fruit: treated fruit attained a deep red colour two to three days later and dropped completely after six to nine days. These results indicated that ethylene was instrumental in ripening of acerola and that AVG delayed ripening by one to two days. Furthermore, fruits treated with ethephon (100 ppm) had an ‘L’ value (brightness) that decreased rapidly while the ‘a*’ value (red) did the opposite. Accordingly, AVG (100 ppm) delayed the expression of ‘a*’ value compared to non-treated control fruits, and also decreased the ‘L’ value. Ethephon (100 ppm) in this study showed acceleration in fruit drop before ripening but increased the concentration of total vitamin C. Differences were also observed in the number of days to 50% fruit drop in relation to the degree of colouration at the time of treatment. Thus, after treatment with AVG (100 ppm) at 0 to 10% colouration, it took eight to 11 days for 50% fruit drop to occur compared to an application of 10 to 20% colouration, where six to seven days were required; and when applied at 30% colouration, four to five days passed to attain 50% fruit drop. Likewise, duration to acquire an ‘a’ value of more than 30 required two to three days when treated at 0 to 10% and one to two days when treated at 10 to 20 or 30% colouration. In addition, the number of days to bring the ‘L’ value lower than 35 was eight to nine when treated at 0 to 10% colouration, therefore, AVG treatment at an earlier stage of maturation, that is, at a lower percentage fruit colouration, also lowered the ‘L’ value. The three major conclusions from the study by Koura et al. (2002) indicated firstly, that application of AVG alone failed to achieve fruit set, and by inhibiting ethylene evolution during this period, it did not improve fruit setting nor did it prevent the formation of an abscission layer. Secondly, ethylene played an essential role in rapid fruit ripening while AVG delayed fruit ripening by one to two days. Thirdly, AVG enhanced fruit setting when combined either with 4-CPA or GA3 and addition of AVG prior to fruit harvesting at 0 to 10% colouration increased shelf life and marketability of fruits. The aforementioned discussion by Vendramini and Trugo (2000) and de Assis et al. (2001) of a decrease in vitamin C content as acerola fruits ripened, which contradicts earlier work by Davey et al. (2000), was in fact supported by Badejo et al. (2007) in their pioneering investigations at the molecular level where they examined molecular cloning and expression of GDP-D-Mannose-3”, 5”-Epimerase (GMEase) during fruit ripening in acerola fruits. The high rate of cell division during fruit ripening articulated by Carrington and King (2002) may have accounted for the transcript abundance of MgGMEase (amino acid sequences of GMEase from Malpighia glabra) in the green unripe fruits (Badejo et al., 2007). Badejo et al. (2007) argued that the substrate for GMEase, and GDP-mannose, available in the fruit during cell division, may not all be channelled to vitamin C biosynthesis because other mechanisms within the plant such as cell wall and L-fructose biosynthesis also required GDP-mannose, and this could lead to a reduction in the expression of MgGMEase and consequently a low vitamin C content in acerola fruit during ripening. They also provided evidence to prove that

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as fruit ripening progressed, MgGMEase transcript is reduced along with vitamin C content, emphasizing that vitamin C biosynthesis in acerola may indeed follow the D-Mannose/L-galactose pathway as previously hypothesized by Wheeler et al. (1998). However, it is also possible that the molecule is also synthesized through the D-galacturonic acid pathway, in view of the fact that the substrate is abundant in the cell walls of all plants (Badejo et al., 2007). 2.7.4 Recommended storage and shipping conditions As fresh acerola fruits are highly perishable, it is recommended that air shipments be undertaken under refrigerated conditions at 7 to 8°C and 90 to 95% relative humidity. Fruits should be placed in low-density polyethylene bags, then in shallow cardboard cartoons and precooled at 7 to 8°C prior to loading in refrigerated containers. Shipping containers must be properly cleaned to remove decaying fruit and vegetables from previous shipments, which would release ethylene gas, promoting ripening and senescence and shortening the fruit’s shelf life. Care must be taken not to mix acerola cherries, which have a climacteric pattern of respiration, with incompatible commodities during transport, particularly to overseas markets. They should ideally be shipped in separate units. Shipments in the same containers as climacteric fruits such as passion fruit, banana, plantain, mango and papaya should be avoided. Likewise, they should not be placed in containers with green leafy vegetables such as shado benni, parsley, spinach and thyme; and root crops should also be avoided because the volatiles produced by the cherries would accelerate senescence in these commodities (Mohammed, 1996).

2.8

Processing

2.8.1 Fresh-cut processing The thin skin of acerola, the presence of a winged-type seed and, to a lesser extent, its small size limits its use as an industrial fresh-cut commodity. Enzymatic browning does not occur once it has been sliced and deseeded due to its intrinsically high vitamin C content. Porcu and Rodriguez-Amaya (2006) found that peeling of fruit reduced the level of β-carotene. Peeling also reduced the level of violaxanthin (another carotenoid) whereas levels of other carotenoids identified, including neoxanthin, lutein, β-cryptoxanthin and α-carotene, remained virtually unchanged (Porcu and Rodriguez-Amayo, 2006). 2.8.2 Other processing practices As acerola is highly perishable, researchers have investigated many market opportunities for a diverse range of value-added, processed products. The process for production of frozen acerola is outlined below. After the fruits are washed and sorted, the selected fruits are diverted from the packaging line to a forced air

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tunnel to be frozen. The duration of freezing should be as short as possible, as slow freezing can cause large ice crystals to form. These cause cell membranes to rupture, reducing compartmentalization in the fruit. The resulting increase in interaction between enzymes and substrates leads to undesirable changes such as softening and yellowing. Yellowing of frozen fruits can be avoided by forced air or hydro-cooling prior to freezing at −18°C. Fruits should be packaged immediately after the fruits have been frozen, preferably with an automatic packing machine that weighs and seals thermoplastic bags. Polyethylene bags may contain 0.5, 1, 2, 14 or 16 kg frozen fruit, according to market requirements, and are arranged inside water and compression resistant cardboard boxes (Alves et al., 1999). For prolonged storage frozen fruits must be kept at −20°C. Physical, biochemical, microbiological and nutritional changes can still occur in the frozen fruit during storage depending on the duration of storage and temperature. The physical changes that begin during the initial freezing process may continue during storage, in particular water recrystallization due to the temperature fluctuations that arise from excessively frequent door opening or incoming loads with elevated temperatures. These temperature fluctuations favour the growth of the undesirable larger ice crystals at the expense of smaller ones, emphasizing the need to maintain the cold chain throughout distribution. Maciel et al. (2004) assessed the effects of storage conditions on the nutritional and organoleptic properties of frozen acerola fruit, fruit pulp and jelly. Their results showed that low temperature (−18°C) storage effectively retained the vitamin C level of frozen acerola fruits and pulp. The total acidity and pH of frozen jelly (49% sucrose, 1% pectin and 50% acerola juice) remained practically constant during 180 days of storage and the product’s quality remained the same. However the authors cautioned that frozen storage of acerola fruit other than those required for further processing for a period longer than 30 days should be discouraged because its sensory characteristics can be altered. Marques et al. (2006) investigated the effect of freeze-drying on several quality parameters of acerola fruits such as water activity (aw), glass transition temperature (Tg), vitamin C content, shrinkage and rehydration capacity. They observed that freeze-dried acerola fruits can easily be reconstituted and important parameters, such as vitamin C content, are well preserved, even in fruits processed at an intermediary stage of ripening. De Freitas et al. (2006) evaluated chemical, sensory and microbiological changes in non-sweetened glass-bottled acerola tropical fruit juice processed by the hot fill method and stored for 350 days under simulated retail conditions (28°C). They reported that over this period the juice maintained good microbiological stability and retained total soluble solids and SO2 levels throughout storage. However, the juice browned slightly and increased in pH, while total carotenoids, anthocyanins and vitamin C decreased slightly. Acerola fruits have a pectin content of 0.5 to 4.0% fresh material weight. This macromolecule is currently used in the candy industry and in the enrichment of food as dietary fibre. Pectins extracted from acerola fruits can also be used to enhance the turbidity, consistency and appearance of fruit juices (Alkorta et al., 1996). In fruits, the pectin substances account for about 0.5 to 4% of the fresh

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material weight. When the tissue is ground, the pectin is found in the liquid phase (soluble pectin) causing an increase in viscosity and the formation of pulp particles, whereas other pectin molecules remain bound to cellulose and this facilitates water retention (Kashyap et al. 2001). The enzyme pectinmethylesterase (PME) from acerola fruits can be used in the preparation of low methoxyl pectin and in the destabilization of cloud in fruit juices. However, studies reported by de Assis et al. (2008) showed that a PME from acerola (characterized after partial purification by filtration in Sephadex G-100) had a variety of PME isoforms, with high thermal stability. Acerola PME displayed high catalytic activity at relatively high temperatures, which induced changes in juice flavour, thereby compromising the use of PME for juice clarification.

2.9

Conclusions

Though acerola is widely accepted as having a diverse range of health, pharmacological and nutritional benefits both in its fresh and processed forms, not enough studies have yet focused on improving fundamental knowledge for rational cultivar selection, improving fruit yield, size and skin thickness and reduction in or elimination of seeds via biotechnology. Especially as marketing is strongly based on its high vitamin C content and abundance of carotenoids, there needs to be further research into the stability of these antioxidants in fresh-cut fruit, in bottled juice and even in nutraceuticals and products where acerola juice is combined with other fruit juices and manufactured into energy beverages, sport drinks and other functional food products. Existing research suggests its antifungal potential for the treatment of dermaphytic infections, its capacity to bolster immunity, to prevent formation of blood clots and to reduce the risks associated with cancers, heart diseases and other degenerative diseases, but its medicinal benefits require further exploration. Other important medicinal benefits that need further research include: the ability of its copper content to facilitate the absorption of iron in the body; the ability of acerola juice to act as a powerful solvent for inorganic calcium deposits in the body, thereby assisting in maintaining the elasticity of the body; the fruit’s dietary fibre content which can provide relief from constipation by providing roughage for the enhancement of colon health, not to mention its low calory, fat and sodium content and lack of cholesterol, making it a perfect fruit for health conscious individuals. Quality indices for acerola fruit need to be better specified, as the quality of the raw material varies and processed products are available in many forms. The pesticide residues found in acerola have not been sufficiently investigated. Maximum permitted levels of pesticides that are acceptable for local markets and for international trade must be established. Improved methods of harvesting, packaging, storing, precooling and enhancing quality and shelf life are warranted. Research, extension and development studies on the above will expand existing markets in Japan, Germany, France, Belgium, Hungary, in the US and in Latin America especially in Chile, Uruguay and Argentina where there is growing

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demand for acerola fruit for juice enrichment and where there are product development opportunities in the pharmaceutical industry. In particular, research to avoid deterioration of bioactivity must be undertaken. Particularly noteworthy is the well-established fact that acerola fruits at the immature green and green stages of maturity could be exploited as a source for pectin, a macromolecule currently used in the candy industry and in dietary fibre enrichment of foods.

2.10

References

Alkorta I., Garbisu C., Llama M. J. and Serra J. L. (1996), ‘Immobilization of pectin lyase from Penicellium italicum by covalent binding to nylon’, Enzym Microb Technol, 18, 141–146. Alves R. E. and Menzies J. B. (1994), ‘Postharvest characterization of red and yellow acerolas from commercial planting’, Proceedings of XIII Congresso Brasileiro de Fruiticultura, 1, 99–100. Alves R. E., Menezes J. B., Chitarra A. B. and Chittara M. I. F. (1992), ‘Respiratory activity and physic-chemical and chemical characteristics of acerola in different stages of maturation (Malpighia emarginata DC.)’, Agropecuaria Technica, Areia, 13, (1/2), 27–34. Alves R. E., Chitarra A. B. and Chitarra M. I. F. (1995), ‘Postharvest physiology of acerola (Malpighia emarginata DC.) fruits: Maturation changes, respiratory activity and refrigerated storage at ambient and modified atmospheres’, Acta Hortic, 370, 223–229. Alves R. E., Filgueiras H. A. C., Mosca J. L. and Menezes B. (1999), ‘Brazilian experience on the handling of acerola fruits for international trade: Harvest and postharvest recommendations’, Acta Hortic, 485, 31–36. Araujo P. S. R. and Minami K. (1994), ‘Acerola’, Fundacao Cargill, Campinas, SP, Brazil, 81 pp. Arostegui F. and Pennock W. (1995), ‘La acerola’, Publ Miscelanea 15, Rios Pedras, Puerto Rico, 9 pp. Badejo A. A., Esaka M., Jeong S. T. and Goto-Yamamoto N. (2007), ‘Molecular cloning and expression of GDP-D-Mannose-3”, 5” –Epimerase during fruit ripening in acerola’, Acta Hortic, 763, 91–97. Byrne M. (1993), ‘New food products in around the world’, Food Eng Int, 46–54. Carrington C. M. S. and King R. A. G. (2002), ‘Fruit development and ripening in Barbados cherry (Malpighia emarginata DC.)’, Scientia Hortic, 92, 1–7. Cavalcante I. H. L., Beckman M. Z., Martins A. B. G. and Campos M. C. C. (2007), ‘Preliminary selection of acerola genotypes in Brazil’, Fruits, 62, 27–34. Cerqueira M. A., Lima A. M., Teixeira J. A., Moreira R. A. and Vicente A. A. (2009), ‘Suitability of novel galactomannans as edible coatings for tropical fruits’, Journal of Food Engineering, 94, 372–378. Davey W. W., Montagu M. V., Inze D., Sanmartin M., Kanellis A. et al. (2000), ‘Plant L-ascorbic acid: chemistry, function, metabolism, bioavailability and effects of processing’, J Sci Food Agric, 80, 825–860. de Assis S. A., Fernandes F. P., Martins A. B. G. and Oliveira O. M. M. (2008), ‘Aerola: importance, culture conditions, production and biochemical aspects’, Fruits, 63 (2), 93–101. de Assis S. A., Lima D. C. and Faria O. M. M. (2001), ‘Activity of pectinmethylesterase, pectin content and vitamin C in acerola fruit at various stages of fruit development’, Food Chem, 74, 133–137. de Freitas S. A. S., Maia G. A., de Sousa P. H. M., Brasil I. M. and Pinheiro A. M. (2006), ‘Storage stability of acerola tropical fruit juice obtained by hot fill method’, Int J of Food Science and Technology, 41 (10), 1,216–1,221.

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Filgueiras H. A. C., Wang S. Y., Dinl M., Lu Y., Farley C. et al. (2007), ‘Evaluating the antioxidant capacity of fruits from five new clones of acerola (Malpighia emarginata DC.)’, EULAFF International Workshop, Angra dos Reis, Brazil. 23 pp. Gomes J. E., Perecin D., Martins A. B. G. and Almeida E. J. (2000), ‘Variabilidade fenotipica em genotipos de acerola, Pesqui. Agropecu. Bras’, 35, 2,205–2,211. Guadarramma A. (1984), ‘Algunos cambios quimicos durante la maduracion de fructose de semeruco (Malpighia punicifolia L.)’, Rev. Fac. Agron (Maracay), 13, 111–128. Hanamura T., Uchida E., and Aoki H. (2008), ‘Changes of the composition in acerola (Malpighia emarginata DC.) fruit in relation to cultivar, growing region and maturity’, J of the Science of Food and Agriculture, 88 (10), 1,813–1,820. Johnson P. D. (2003), ‘Acerola (Malpighia glabra L., M. punicifolia L., M. emarginata DC.): agriculture, production and nutrition’, World Rev Nutr Diet, 91, 67–75. Kashyap D. R., Vohra K. P., Chopra S. and Tewari R. (2001), ‘Applications of pectinases in the commercial sector: a review’, Bioresour Technol, 77, 215–227. Koura S., Kato T., Tachikawa S., Onjo M. and Ishihata K. (2002), ‘Effect of aminoethoxyvinylglycine on fruit set and on control of ripening in acerola’, Acta Hortic, 575, 821–828. Lopes R., Bruckner C. H., Cruz C. D., Lopes M. T. G. and Freitas G. B. (2001), ‘Repetibilidade de characteristicas do frutos de aceroleira’, Pesqui Agropecu Bras, 36, 507–513. Maciel M. I. S., de Lima V. L. A. G., dos Santos E. S. and Lima M. D. A. (2004), ‘Effects of biofilm and refrigeration on acerola postharvest conservation’, Rev Bras Frutic, 26, (1), 1–5. Maciel M. I. S., de Melo A., de Lima V. L. A. G., de Silva M. R. F. and de Silva I. P. (1999), ‘Processing and storage of acerola (Malpighia sp.) fruit and its products’, J of Food Science and Technology, 36, 142–146. Marques L. G., Ferreira M. C. and Freire J. (2006) ‘Freeze-drying of acerola (Malpighia glabra L.)’, Chemical Engineering and Processing, 46 (5), 451–457. Mezadri T., Fernandez-Pachon M. S., Villano D., Garcia-Parrilla M. C. and Troncosco A. M. (2006), ‘El fructo de la acerola: composicion y posibles usos alimenticios’, Arch Latinoam Nutr, 56, 101–109. Miyashita R. K., Nakasone H. Y. and Lamoureux C. H. (1964), ‘Reproductive morphology of acerola (Malpighia glabra L.)’, Hawaii Agric Exp Sta Tech Bull, 63, 31. Mohammed M. (1996), ‘Postharvest handling and storage of West Indian cherry (Malpighia emarginata DC.)’, Continuous Education Programme in Agricultural Technology (CEPAT), Faculty of Agriculture, University of the West Indies Training Course in Postharvest Technology of Fruits, Vegetables and Root Crops, 12 pp. Monselise S. P. (1986), ‘CRC Handbook of fruit set and development’, CRC Press, Boca Raton, FL. Morton J. (1987), ‘Barbados cherry’, in Morton J., Fruits of Warm Climates, 204–207. Naidu K. A. (2003), ‘Vitamin C in human health and disease is still a mystery?, An overview’, Nutr J, 2, 7–16. Nakasone H. Y., Miyashita R. K. and Yamane G. M. (1966), ‘Factors affecting ascorbic acid content of the acerola (Malpighia glabra L.)’, Proc Amer Soc Hortic Sci, 89, 161–169. Neto L. G. and Soares J. M. (1994), ‘Acerola para exporacao aspectos technicos da producao’, EMBRAPA Brasilia, Brazil, 13 pp. Nogueira R. J. M. C., Moraes J. A. P. V., Burity H. A. and Silva Junior J. F. (2002), ‘Efeito do estadio de maturacao dos frutos nas caracteristicas fisico-quimicas de acerola’, Pesqui Agropecu Bras, 37, 463–470. Porcu O. M. and Rodriguez-Amaya D. B. (2006), ‘Variation in the carotenoid composition of acerola and its processed products’, Journal of the Science of Food and Agriculture, 86 (12), 1,916–1,920.

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Roberts-Nkrumah L. B., Mohammed M. and Barbeau G. (1994), ‘The production of West Indian cherry (Malpighia emarginata DC.)’, Proceedings of IICA 3rd Regional Workshop on Tropical Fruits, 187–190. Santini R. Jr and Huyke A. (1956), ‘Identification of the anthocyanin present in the acerola which produces colour changes in the juice on pasteurization and canning’, J Agr Univ Puerto Rico, 40, 171–178. Schoenberger L., Krottenthaler M. and Back W. (2002), ‘Sensory and analytical characterization of non-volatile taste-active compounds in bottom-fermented beers’, MBAA TQ, 39, 210–217. Semensato L. R. and Pereira J. (2000), ‘Characteristicas de fructose de genotipos de aceroleira cultivados sob elevada altitude’, Pesqui Agropecu Bras, 35, 1,529–1,536. Simao S. (1971), ‘Careja das Antilhas. In: Manual de Fructicultura’, Agronomica Cers, Sao Paulo, 477–485. Vendramini A. L. and Trugo L. C. (2000), ‘Chemical composition of acerola fruit (Malpighia puniciflora L.) at three stages of maturity’, Food Chem, 71, 195–198. Watada A. E. (1987), ‘Vitamins’, in Weichman, J, Postharvest Physiology of Vegetables, Marcel Dekker, New York, 455–467. Wheeler G. L., Jones M. A. and Smirnoff N. (1998), ‘The biosynthetic pathway of vitamin C in higher plants’, Nature, 393, 365–369.

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3 Achachairú (Garcinia humilis (Vahl) C. D. Adam) O. Duarte, National Agrarian University, Peru

Abstract: Achachairú is a Guttiferae native to oriental Bolivia, formerly Rheedia laterifolia L. Herzog, and now named Garcinia humilis (Vahl) C. D. Adam. This fairly large tree produces very good tasting fruit with a white, juicy and sweet pulp that normally contains one fairly large seed and two aborted ovules. Its weight is around 40 g. The seed is apomictic, and more than one plant can arise from it. The peel, of an orange-brown colour at maturity, is thick but somewhat brittle. The fruit is nonclimacteric and fairly resistant to transport and storage. Adequate storage temperature is 12°C while 6°C results in chilling injury. Few studies have been done on its postharvest physiology and handling requirements. The success of small export quantities has raised interest in expanding production, since most of the fruit comes from wild or backyard trees, with little coming from technically conducted orchards. Key words: Achachairú, postharvest, non climacteric, chilling injury, thick peel, apomixes.

3.1

Introduction

3.1.1 Origin, botany, morphology and structure Rheedia laterifolia L. Herzog belongs to the Guttiferae family and grows wild in the Eastern parts of Bolivia, where it is very popular. This species has been included recently in the genus Garcinia of the Old World as Garcinia humilis (Vahl) C. D. Adam, although the flowers generally have only four sepals. According to Morton (1987) this genus comprises about 45 species that have not yet been fully defined. In Spanish it is called achachairú, shashairú, ibaguazú, cachicheruqui or tapacuari. Wild plants are harvested to sell the fruit in nearby towns, mainly in the city of Santa Cruz de la Sierra. There are backyard trees, many of them spontaneous, in rural areas and small plantations. Larger orchards have been started in recent years, because this fruit, that has a flavour resembling that of mangosteen, seems to have a market potential outside Bolivia. Some air

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shipments of fruits from wild or semi-cultivated trees have been sent to Europe and this has created interest in starting commercial plantations (Duarte and Paull, 2008). At the 2011 fruit logistica in Berlin fruit coming from Australia was shown under the name of ‘achacha’. In this region there are several relatives of this species including Rheedia achachairú, R. brasiliensis, R. gardneriana, R. macrophylla, R. madruno, R. spruceana, R. rogaguensis, etc. with edible fruits. These are in less demand, though, except for ocoró (R. acuminata), which according to Ardaya et al. (1995) is marketed in similar volumes. The pyramidal canopy of the achachairú tree can grow to 6 to 12 m in height and the trunk can reach a diameter of 40 cm. The opposite, lanceolate leaves, measuring 15 to 25 by 4 to 7 cm, are shiny and slightly darker green on the upper side, with an acute apex, entire margins and a prominent central vein, while the lateral parallel veins are not very conspicuous. The developing leaves are pinkish-bronze or reddish and turn yellowish-green before maturing. Young leaves can be severely burnt by the sun or deformed, so during the initial years semi-shade has to be provided using tall annual plants such as castor bean or pigeon pea or small trees. There are about 200 hermaphrodite flowers (17 to 36 mm long, 20 to 34 stamens, 3 to 5 mm ovary, two sepals, four petals, a pedicel of about 2 cm), to each male flower (9.6 to 12.5 mm long, 26 to 28 stamens that can have a vestigial ovary and a pedicel of about 4 cm). Hermaphrodite flowers come in groups of two to five. Some trees have only male flowers. Anthesis occurs in the morning until noon and honey-bees and other insects seem to play an important role in pollination. About 57% of the flowers are selffertilizing. The remaining fruits come from cross-pollination, thus explaining the variability found among seedlings (Ardaya et al., 1995). The fruit is a berry that has a smooth but hard 2-mm thick skin, that starts out a bluish-green colour (Plate III: see colour section between pages 244 and 245) and evolves to a yellow-orange colour before ripening, ending up orange-brownish when fully ripe (Plate IV: see colour section). The ovoid fruit can measure 4.0 to 5.2 by 3.0 to 4.0 cm in height and diameter, with an average weight of about 40 g (Duarte and Paull, 2008). By weight the fruit is 40% edible pulp, 47% peel and 13% seeds (Duarte and Paull, 2008). The fruits are found inside the canopy. They contain normally one large seed and two aborted ovules. Seeds are cylindrical, brown-coloured measuring 3.0 to 3.4 by 1.5 to 2.0 cm. They can have one to three nucellar embryos plus the sexual embryo, and if split into two pieces each seed can give rise to a plant. Seed size and number are related to fruit size. 3.1.2 Worldwide importance and economic value This species is grown basically only in Bolivia. Some small plantings have been started in Honduras, Guatemala, Colombia, among other countries, but they amount to very little area, so essentially Bolivia is the only important producer. Production still comes mainly from wild trees or small backyard plantings, although in recent years some commercial plantations have been started due to the potential of this fruit as an export product.

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No exact statistics exist on production or planted areas. It is estimated that these new plantings amount to less than 1000 hectares. A 15-year-old tree can produce 2000 to 3000 fruits and some reports indicate production levels of up to 7000 to 8000 fruits for 50-year-old trees. It is estimated that an adult plantation can produce about 19.6 tons per hectare (Ardaya et al., 1995). 3.1.3 Culinary uses, nutritional value and health benefits This fruit is basically eaten fresh out of the hand. The peel is split in two with the thumbnails and one half removed leaving the white flesh containing the seed(s) exposed, that can be removed with the fingers, a spoon or the teeth. Some of the pulp is used to make ice cream or juice. There are no other industrial uses for this fruit. The peel can be put in a blender with water and sugar to make a nice drink. The fresh pulp, according to Ardaya et al. (1995) contains 83.9% water, 0.4% protein, 0.5% fat, 14.2% total carbohydrates, 0.6% fibre and 0.3% ash. There are no reports about the specific properties of the fruit or medicinal uses. There is no information on special nutritive elements either, but it is a very well-flavoured fruit.

3.2

Fruit development and postharvest physiology

3.2.1 Fruit growth, development and maturation The fruit will grow to maturity in about five to six months depending on temperatures. The fruit starts out as a very small, round, green-coloured ovary that becomes ovoid and becomes a bluish-green colour. As already mentioned, as ripening approaches the colour turns yellow and later orange-brown, until it is almost light brown when overripe. Not much else has been studied about this fruit. 3.2.2 Respiration, ethylene production and ripening The fruit is non climacteric since it will not continue to ripen properly after being harvested at the unripe stage. No data on ethylene or carbon dioxide production after harvest are available.

3.3

Maturity and quality components and indices

Maturity is normally determined by the colour of the fruit only, and coincides with the best flavour condition, although no formal maturity indices exist. The fruit should have passed beyond the yellow colour and become orange with a brownish tint in order to be harvested. No other maturity indices are currently taken into consideration.

3.4

Preharvest factors affecting fruit quality

Lack of soil moisture reduces the fruit size, although the fruit’s flavour can be enhanced by the resulting higher concentration of sugars. Mechanical damage

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caused by rubbing leaves or branches will also reduce quality, mainly because it affects the fruit’s appearance.

3.5

Postharvest handling factors affecting quality

3.5.1 Temperature management Storage at very low temperatures can damage the fruit. Storing the fruit at 6°C will result in chilling injury. 3.5.2 Physical damage Mechanical injury will also result in blackening of the damaged area, and as a consequence rotting will follow. 3.5.3 Water loss Although water loss does not happen very fast, the fruit will eventually shrivel and reduce in weight. 3.5.4 Atmosphere Not many results have been published of studies in this area. Poly vinyl chloride (PVC) wraps had a positive effect on extending fruit life after harvest (Duarte and Castedo, 2005). More research is needed on plastic films, waxes and other liquid coatings. These may have a positive effect as atmosphere modifiers and in reducing water loss.

3.6

Physiological disorders

As already mentioned, chilling injury has been found in achachairú held at 6°C, which indicates that it behaves as a tropical fruit.

3.7

Pathological disorders

Rotting of the peel will eventually occur after harvest if damage has occurred (for example if the fruit was roughly handled before or after harvest) or if it has been stored when wet.

3.8

Insect pests and their control

Fruit flies can attack very mature fruits and therefore fruits should be harvested as soon as they reach the right colour. The usual fruit fly control measures should be

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used, together with a lure like hydrolyzed protein or sweet solutions of molasses or brown sugar and a contact diptericide, to eliminate the flies that arrive to the treated areas of the trees attracted by the lure. Not many other pests are of importance.

3.9

Postharvest handling practices

Few studies have been conducted on the best handling practices for this fruit. Avoiding of bruises and rough handling will help prolong fruit life after harvest. 3.9.1 Harvest operations Harvesting is normally done by hand. People climb the trees in order to pick the fruit with the hands. No special tools are normally used to detach the fruit and in many cases fruit are dropped onto the ground, which increases quality deterioration postharvest. 3.9.2 Packinghouse practices Commercial packinghouse operations are not in place for this fruit. If fruits are muddy, they are washed or rubbed with the hands but they are not cleaned, sorted precisely or carefully packaged. Sometimes they are classified by size, normally into three or four categories, just by looking at the fruit. They are normally packed into wooden crates, cardboard boxes and even polypropylene sacs. On arriving at the place of sale no special storage conditions are usually available and in many cases street vendors keep the fruit in carts in full sun or under an improvised plastic shade in the streets. 3.9.3 Control of ripening and senescence No coating, waxing or plastic wrapping is normally used. The fruit is not even refrigerated when selling to the local markets. 3.9.4 Recommended storage and shipping conditions Duarte and Castedo (2005) found that storage at 12°C combined with packing in trays wrapped in poly vinyl chloride (PVC) film was the best treatment, extending storage life to three weeks, but they did not investigate the effect of varying the temperature. The use of different temperatures, wraps or coatings and their combination, as well as other techniques, should be investigated in the future. The fruit can last at least one week in room conditions for fresh market use and two to three weeks for industrial use (ice cream, refreshments). Fruits will shrivel and lose firmness but will not rot, unless they are kept wet in plastic bags or have been previously damaged.

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Processing

It would be difficult to prepare fresh-cut achachairú. Presenting the fruit peeled with the pulp around the seeds could be an interesting possibility, however, since peeling and removing the whole inner part is very easy and the pulp around the seeds stays firm. Oxidation could be a problem, though, and would need to be prevented. Industrial processing is performed on a very limited scale. In terms of domestic processing, some people separate the pulp from the seeds to prepare juice in a blender or make ice cream. In some cases the fruit peel is put in the blender with water and sugar and a fairly tasty drink is prepared. The fruit is not normally canned. It is sometimes frozen at home or in cottage industries so that the pulp can be kept for juice or ice cream preparation after the harvest season is over.

3.11

Conclusions

This is a very flavoursome fruit that is starting to become known outside of its place of origin. It has been exported to Europe on a small scale over the last 20 years. The flesh is very tasty and the fruit peel is very tough and resistant but will shrivel and eventually rot. The main defect of this fruit is the large size of its seeds that comprise one-third to almost one-half of the fruit cavity. Its fine taste creates the potential to expand production, but a marketing campaign will be required to make the fruit well-known in new markets. The plant and the fruit are not attacked by many insects and diseases. If exports are increased, commercial plantations will have to be started, appropriate plant materials selected, propagation methods revised and plantings managed adequately, as when growing any important fruit crop. This will improve quality and yield, and the interested markets could be satisfied and even grow in the future. Postharvest handling should be improved by avoiding rough handling of the fruit, keeping it shaded and wrapping it in PVC or using a coating agent. The use of refrigeration would markedly improve the storage life of this fruit.

3.12

References

Ardaya D., Vargas M. A. and Kodera Y. (1995), El cultivo del achachairú. Santa Cruz de la Sierra, Bolivia, Centro de Investigación Agrícola Tropical (CIAT) y Agencia de Cooperación Internacional del Japón (JICA). Duarte O. and Castedo M, (2005), Estudios de conservación de frutos y semillas de achachairu y su propagación vegetativa. Tesis de Ingeniero Agrónomo, Escuela Agrícola Panamericana – El Zamorano, Honduras. Duarte O. and Paull R. (2008), Achachairú (Rheedia laterifolia (L.) Herzog), In Encyclopedia of Fruit and Nuts, Wallingford, UK, CAB International: 272–273. Morton J. E. (1987), Fruits of Warm Climates, Winterville, North Carolina, USA, Creative Resources Systems.

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4 Ackee fruit (Blighia sapida Konig) M. A. Emanuel and N. Benkeblia, University of the West Indies Mona Campus, Jamaica

Abstract: The ackee (Blighia sapida), a tropical fruit belonging to the Sapindaceae family, has its origin in West Africa but has traversed the Atlantic Ocean, making the Caribbean (where it grows wildly and is also cultivated) its home. The colloquial name Ackee is derived from the terms ‘anke’ and ‘akye-fufuo’, which are used to describe the fruit in West Africa. It was named Blighia sapida in honour of the infamous Captain William Bligh who transported the fruit from Jamaica to England in 1793. Although Ackee fruit was first known for its poisonous properties, it is nowadays considered one of the major fruits consumed in Jamaica and is an ingredient of the national dish Ackee Saltfish. Extensive literature exists on hypoglycin A, the toxic compound of unripe Ackee, while no referenced data are readily available on its physiology and reports are very limited on its biochemistry. The aim of this chapter is to fill this gap moderately, and give an overview on the fruit as fresh and commercial produce. Key words: Blighia sapida, ackee, maturity, biochemistry, composition.

4.1

Introduction

4.1.1 Origin and history The Caribbean region accounts for not more than 0.03% of the total world’s lands, however, the region is rich with a wide range of species and varieties of plants. More than 2% of the total number of plant species in the world is endemic and found in this region, and some species are found only in Jamaica (Adams, 1972). It is established that ackee is indigenous to the forests of the Gold Coast of West tropical Africa where it is not consumed much, but various parts of the Ackee tree have been put to domestic use. In Ghana, for example, the fruiting tree is considered ornamental, and trees are planted for shade. The ackee fruit was brought to Jamaica in 1778 to furnish food for slaves. In 1793 the fruit was brought to England by the renowned Captain Bligh, and named Blighia sapida in 1806 by Koening in honour of Captain Bligh. It was readily adopted and became commonly grown in dooryards and along

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roadsides and, to some extent, naturalized. The arils still constitute a favourite food of the island and the fruit is featured in a calypso despite the health hazards associated with it. Ackee trees are found throughout Jamaica: however, most of the trees grow in the Clarendon and St Elisabeth parishes. The ackee was planted also in Trinidad and Haiti and elsewhere in the West Indies and the Bahamas, and apparently was carried by Jamaican slaves to Panama and the Atlantic Coast of Guatemala and Costa Rica. In 1900 it was outlawed in Trinidad after it had caused some fatalities. There are scattered trees in Surinam, Venezuela, Colombia, Ecuador and Brazil, quite a number maintained as curiosities in southern Florida, and some are planted around Calcutta, India. The tree has been tried in the warm, moist climate of Guyana and Malaya but when planted at Lamao in the Philippines in 1919, the trees did not bear fruits in the first fruiting season although they did so in the following years. 4.1.2 Botanical description The ackee tree is tropical evergreen with a yellow-red fruit that is about 10 cm wide and weighs 100 g. As the ackee fruit ripens, the colour of the fruit changes from green to yellow, to yellow-red, and then to red when the fruit is fully open showing the yellow arils and black seeds. When ripe, the fruit splits longitudinally into three sections to reveal glassy black seeds in each section surrounded by a thick yellow oily, fleshy portion. This is the aril, which is edible and has a nutty flavour (Barceloux, 2008). Ackee fruit belongs to the family Sapindaceae, and is also known as the ackee apple, or vegetable brain (seso vegetal in Spanish) (Plate V: see colour section between pages 244 and 245). Other Spanish names for ackee are also used such as: arbol de seso and palo de seso (in Cuba); huevo vegetal and fruto de huevo (in Guatemala and Panama); arbol del huevo and pera roja (in Mexico); merey del diablo (in Venezuela); bien me sabe or pan y quesito (in Colombia) and akí (in Costa Rica). In Portuguese, ackee is called castanha or castanheiro de Africa. In French, it is named arbre fricassé or arbre à fricasser (in Haiti); yeux de crabe or ris de veau (in Martinique), while in Surinam it is known as akie. In Africa, from where it is supposed to have originated, ackee is called kaka or finzan (in Côte d’Ivoire), abd finza (in the Sudan), while in other African regions ackee is generally known as akye, akyen or ishin, because of the many dialectal names. The colloquial name, ackee, is derived from the terms anke and akye-fufuo, which are used to describe the fruit in West Africa. It was named Blighia sapida in honour of the infamous Captain William Bligh, who transported the fruit from Jamaica to England in 1793. In Jamaica, two types of ackee are recognized – ‘cheese’, or hard, and ‘butter’, or soft. The ‘cheese’ ackee aril is hard, cream coloured and retains its shape when cooked, while the ‘butter’ ackee aril is soft and yellow, losing its shape easily during cooking. The ripe fleshy ackee aril is widely consumed by Jamaicans. It is one of the national dishes, and is considered as one of the national symbols in Jamaica. The unripe fruit contains a water-soluble toxin, hypoglycine A (L-aminomethylenecyclopropylpropionic acid), and the less toxic hypoglycine B.

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The latter compound is the -glutamyl conjugate of hypoglycine A. Unripe akee fruit also contains glutamate analogs that are carboxycyclopropylglycine compounds (Natalini et al., 2000). To prevent toxicity, the seeds and husk of the ackee fruit must be carefully removed and the aril thoroughly washed and cooked before consumption. Cooking arils of unripe ackee fruit does not destroy the toxins, whereas cooking effectively arils of ripe fruits eliminates the toxicity by leaching hypoglycine A (McTague and Forney, 1994; Golden et al., 1984).

4.2 Toxicity of ackee fruit Although ackee fruit was first known for its poisonous properties, it is nowadays considered one of the major fruits consumed in Jamaica. The toxicity of ackee fruit has been associated with the consumption of unripe fruit since the late nineteenth century (Scott, 1916). Between 1880 and 1955, a variety of case reports associated the ingestion of ackee fruit with vomiting, generalized weakness, altered consciousness and death, including an epidemic of 151 cases and 32 deaths during 1954 near Montego Bay, Jamaica (Feng and Kean, 1955; Feng, 1969). Hassall and Reyle (1954) first isolated the two toxic constituents (hypoglycine A and B) from the arils and seeds of unripe ackee in 1954 (Fig. 4.1). In 1976, Tanaka et al. confirmed the ingestion of hypoglycine A from unripe ackee fruit as the cause of Jamaican vomiting sickness. An extensive literature exists on the toxicity of hypoglycine A (Billington et al., 1978; Henry et al., 1998; Joskow et al., 2006; Sherratt, 1986). A number of other metabolites have been isolated from the ackee fruit. While not as biologically interesting, the compounds are unusual in their structure. Blighinone, a sparingly soluble quinone was isolated from the arilli of the fruit (Garg and Mitra, 1968). Vomifoliol, has been isolated from the leaves and stems of the plant and has been implicated in the endogenous regulation of stomatal aperture (Stuart et al., 1976). More recently, another non-proteinogenic amino

Fig. 4.1

Structural composition of hypoglycine A.

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acid (2S, 1’S, 2’S)-2-(2’-carboxycyclopropyl), glycine (CCG 1), was isolated from the fruit (Natalini et al., 2000). It is similar in structure to hypoglycine A with respect to the presence of a cycopropane ring structure, which is a rare occurrence in nature. From the toxicological point of view, metabolism of hypoglycin yields methylenecyclopropylacetyl-CoA (MCPA-CoA). The Acyl-CoA dehydrogenase accepts MCPA-CoA as a substrate, removing a proton from the a-carbon to yield an intermediate that irreversibly inactivates acyl-CoA dehydrogenase by reacting covalently with FAD on the enzyme (Corredor et al., 1967; Schulz, 1991; Yasuyuki and Tanaka, 1990). However, other research reported that methylenecyclopropylacetyl-CoA severely inhibits not only acyl-CoA dehydrogenase I (butyryl-CoA dehydrogenase, EC 1.3.99.2) but also acyl-CoA dehydrogenase II (octanyl-CoA dehydrogenase, EC 1.3.99) (Kunau and Lauterbach, 1978). Moreover, the effect of methylenecyclopropane-pyruvic acid (a toxic amino acid occurring in the ackee and a metabolite of hypoglycine) on gluconeogenesis in vitro was studied. It was noted that glucose production from a variety of precursors was found to be markedly inhibited, the agent being active at low concentrations (0.1 mM). The site of the block was located specifically at the fructose 1,6-diphosphatase reaction; however, the mechanism by which this effect is achieved is not known (Kean and Rainford, 1973).

4.3

Fruit maturity

The ackee takes seven to eight weeks to attain full maturity. During weeks two to three of fruit development, the fruit doubles in size, after which it increases at a much slower rate (Stair and Sidrak, 1992). At full maturity the fruit are pearshaped and acquire a red or yellow tinge with red colouration. The pods then open revealing the seeds and three fleshy arilli, and fruits are considered safe for consumption only at this stage of maturity (Plate VI: see colour section between pages 244 and 245) as reported by Kean and Hare (1980) and described below (see section 4.4). It has been hypothesized that during fruit maturity hypoglycine A is translocated from the arils to the seeds of the fruit (Plate VI: colour section), where it is converted to the dipeptide hypoglycine B. As the fruit matures the concentration of hypoglycine B in seeds increases from 0.40 mg g−1 to 3.30 mg g−1. (Kean and Hare, 1980). Hypoglycine B is found only in the seeds of the fruit. It also possesses hypoglycemic activity but is less potent than hypoglycine A. Brown et al. (1991) analyzed ackee fruits with different range of maturities, and found that hypoglycine A contents in the arils dropped from over 1000 ppm to undetectable (10 plants) (1–2 plants)

Collected wild for human consumption

Phyllanthus emblica

*

*

*

Phyllanthus acidus P. acutissimus P. albidiscus P. amarus P. angkorensis P. chamaepeuce P. clarkei P. collinsae P. Columnaris P. elegans P. emblica P. geoffrayi P. gracilipes P. Kerrii P. lingulatus P. mirabilis P. oxyphyllus P. reticulates P. roreus P. sikkinensis P. virgatus P. acidus P. emblica P. acidus P. acidus P. emblica P. emblica P. javanicus (Ceremai) P. acidus P. emblica P. acidus P. amarus (Bhonya amali) P. emblica P. emblica P. acidus P. acidus P. acidus (Grosella) P. emblica P. emblica P. emblica

*

*

* * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * *

* * *

* * * *

* *

* * * *

* *

* * *

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Aonla (Emblica officinalis Gaertn.)

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As Ayurvedic (Indian system of medicine) preparations: Chavanprash, trifla, trifla pash, trifla mashy, trifla churn, madhumeh (diabetic) churn, and bavasir nashak mahaushdhi. As cosmetic and industrial products: Hair oil, shampoo, tooth powder and in the tanning industry.

5.1.5 Medicinal uses Several investigators have determined the efficacy of aonla as an anti-atherosclerotic (Thakur et al., 1988), antidiabetic (Tripathi et al., 1979), antimutagenic (Sharma et al., 2000) and anticancer agent (Jose et al., 2001). Rawat and Uniyal (2003) reported that aonla root bark, stem bark, leaf, fruit and seed possess medicinal properties. The root bark is astringent and is useful for treating ulcerative stomatitis and gastric ulcer. The bark is astringent and used in treating gonorrhea, jaundice, diarrhea and myalgia. The leaves are used to treat conjunctivitis, inflammation, dyspepsia, diarrhea and dysentery. The fruits are astringent, cooling, anodyne, carminative, digestive, stomachic, laxative, alterant, alexeteric, aphrodisiac, diuretic, antipyretic, tonic and trichogenous. They are used for treatment of diabetes, cough, asthma, bronchitis, headache, ophthalmic disorders, dyspepsia, colic, flatulence, hyperacidity, peptic ulcer, erysipelas, skin diseases, leprosy, haematemasis, inflammations, anaemia, emaciation, hepatic disorders, jaundice, strangury, diarrhea, dysentery, intringic haemorrhages, leucorrhoea, menorrhagia and prevention of greyness of hair. Seeds are reported to be useful in treating asthma, bronchitis and biliousness. Aonla is an important ingredient of triphala, which consists of harer (Terminalia chebula), bahera (Terminalia bellirica) and aonla (Emblica officinalis) in equal proportions. Triphala is an appetite stimulant and carminative, considered beneficial for eyes and alleviates kapha, pitta, leprosy, constipation anomalies or urinary secretion and malarial fever. Triphala is an important component of muskakadiganal and mustadigana. In Charaksamhita (an ancient book on Ayurvedic medicine), aonla has been listed amongst the foods that are agesustaining. Emblica fruit extract exhibits antioxidant properties, its aqueous extract being a potent inhibitor of lipoid peroxidation and a scavenger of hydroxyl and superoxide radicals in vitro (Scartezzini and Speroni, 2000).

5.2

Fruit development and postharvest physiology

5.2.1 Fruit growth, development and maturation In North India, the aonla tree begins to shed its determinate shoots from February onwards, and its indeterminate shoots are devoid of foliage by the end of February to mid-March. The new determinate shoots, which emerge at nodes from the margins of the scars formed after abscission of determinate shoots in the previous seasons, begin to appear by the end of February and continue to appear until the first week of April. Blossom buds appear on the newly developed determinate

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shoots but shoots that emerged after mid-April do not bear flowers and remain vegetative (Naik, 1949). The flowering period is affected less by temperature and more by day length (Ram, 1982). Male flowers appear first followed by female flowers in the axils of leaves on a determinate shoot. Anthesis of male flowers occurs between 16.00 and 17.00 hrs in ‘Banarasi’, whereas that in ‘Chakaiya’ occurs both in the morning (08.30 to 11.30 hrs) and afternoon (15.30 to 18.30 hrs) (Alleemullah and Ram, 1990). Dehiscence of pollen grains coincides with the anthesis of male flowers in different cultivars, and the majority of the pollen grains are fertile (Bajpai, 1957; Alleemullah and Ram, 1990). The stigma is receptive between the second and fifth day after anthesis. Wind, honeybee and gravity play important roles in pollination on which initial fruit set and ultimate fruit retention depends (Bajpai, 1968; Ram, 1983; Alleemullah and Ram, 1990). Pathak and Srivastava (1994) have observed self-incompatibility in initial studies in flowering and fruit set in aonla, where the number of female flowers varied from two to eight. Fertilization takes place in about 24 hours of pollination (Bajpai, 1968; Ram, 1971). The ovary gets encased in a paper brown covering called ‘cupule’, signifying fruit set. Such fruit set remains dormant for about three to five months after pollination, and growth and development starts at the end of July and first week of August after the onset of the monsoon depending upon the location and climatic conditions. In general, fruit attains 5 to 6 mm diameter by the end of August. The pointed and tapering fruitlet assumes a spherical shape. The fruit grows rapidly from the middle of August to the first week of October and completes almost 75% growth during this period. The growth rate again slows between the second week of October and the first week of November and increases slightly thereafter in a double sigmoid pattern. 5.2.2 Respiration, ethylene production and ripening Aonla is a non-climacteric fruit (Pareek, 2010a). Very little research has been done on aonla postharvest physiology, but it seems that respiration patterns and ripening behaviour vary among the different cultivars, and are affected by climatic conditions and geographical location where the fruit is grown. Respiration is high after fruit set and then declines and maintains low until the fruit starts to mature. Aonla fruit showed respiratory activity (measured as production of carbon dioxide) ranging from 72.00 to 82.10 mg CO2 kg−1 h−1. As a non-climacteric fruit, aonla cannot be ripened after harvest (Pareek, 2010b).

5.3

Maturity and quality components and indices

5.3.1 Determination of maturity indices Being an under-utilized fruit crop, little attention has been given to establishing reliable maturity indices of aonla. However, commonly used parameters like specific gravity, total soluble solids (TSS): acid ratio, colour of fruit surface, fibre

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content, seed colour, heat units, days from flowering to maturity can be used for determining the maturity index of particular cultivar of aonla in a particular region (Ojha, 1986; Singh, 1997; Singh et al., 2004). On the basis of season of maturity, aonla cultivars have been classified into three groups, i.e. early, mid and late season (Pathak et al., 1993). The maturity seasons of selected aonla cultivars are described in Table 5.2. However, the maturity period is affected by various factors such as location, climate, soil type, and other cultivation practices. In the north Indian arid climatic conditions of Rajasthan and Gujarat, fruits of ‘Agra Bold’, ‘NA-7’ and ‘Banarasi’ mature during the last week of October; ‘Francis’ and ‘Krishna’ mature during the first week of November; ‘Gujarat-1’ and ‘Gujarat-2’ by middle of November and ‘Kanchan’ and ‘Chakaiya’ during the last week of November (Singh et al., 2006). At the time of maturity specific gravity should be 1.02 in ‘Chakaiya’; 1.03 in ‘NA-7’, ‘Krishna’ and ‘Kanchan’; 1.06 in ‘Gujarat-2’; 1.07 in ‘Agra Bold’ and 1.08 in ‘Banarasi’, ‘Francis’ and ‘Gujarat-1’. Fibre content at maturity is 0.37% in ‘Krishna’, 0.38% in ‘Banarasi’, 0.54% in ‘NA-7’, 0.58% in ‘Gujarat-1’, 0.60% in ‘Gujarat-2’, 0.65% in ‘Agra Bold’, 0.72% in ‘Francis’, 0.81% in ‘Chakaiya’ and 0.84% in ‘Kanchan’ (Singh et al., 2006). Fruit colour ranged from dull greenish-yellow to translucent in various cultivars. Fruit skin characteristics of various cultivars at maturity is described in Table 5.3. Table 5.2 Maturity seasons of selected aonla cultivars

Table 5.3

Early

Mid

Late

Banarasi Krishna NA-10

Francis NA-7 Kanchan NA-6 NA-9

Chakaiya

Fruit skin characteristics of aonla cultivars at maturity

Cultivar

Fruit skin characteristics

Banarasi Krishna

Thin, smooth, semi-translucent, whitish-green to straw yellow Smooth, whitish-green to apricot yellow in colour with red spots on exposed surface Smooth, thick at upper side and thin at basin, light green in colour Smooth, light green, strips deep red at pea stage which disappear later on Smooth, semi-translucent, light green in colour Smooth, semi-translucent, yellowish-green Slightly rough, thick and light green in colour Smooth, semi-translucent, light green in colour Rough, yellowish-green with pink tinge

Francis Kanchan NA-6 NA-7 NA-8 NA-9 NA-10

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Growing Degree Days (GDD) can also be taken into consideration for determination of fruit maturity. The average GDD for aonla is 5000 hours (Singh et al., 2005d; Shukla et al., 2007). 5.3.2 Quality components The chemical composition of aonla fruits is influenced by cultivar, management practices and environmental factors. The chemical composition of fresh fruit with respect to moisture, protein, fat, crude fibre, starch, sugars, minerals and vitamins is shown in Table 5.4. The total sugar content of aonla fruits varies from 7 to 9.6%: reducing sugars from 1.04 to 4.09 % and non-reducing sugars from 3.05 to 7.23 % among the various cultivars. Aonla is particularly rich in vitamin C. The pulp of fresh fruits contains 200 to 900 mg of vitamin C per 100 g (Kalra, 1988). The fruit pulp contains moisture (81.2 %), fat (0.1 %), calcium (0.05%), potassium (0.02%), iron (1.2 mg 100 g−1), nicotinic acid (0.02 mg 100 g−1) and vitamin C (600 mg 100 g−1) (Kapoor, 1990). The fruit contains trigalloylglucose, techebin, corilagin, ellagic acid, phyllembic acid (6.3%), lipids (6.0%), gallic acid (5.0%) and emblicol (Kapoor, 1990). The seeds contain a fixed oil, phosphaides, and a small quantity of essential oil with a characteristic odour. The fixed oil (16%) is brownish-yellow in colour and contains linolenic (8.78%), linoleic (44.0%), oleic (28.4%), stearic (2.15%), palmitic (2.99%) and myristic (0.95%) acids (Kapoor, 1990). Tannins from aonla bark are found to have 2,3-cis configuration and to be a mixture of partially 3-o-gallated prodelphinidin and procyanidin (Gongye, 1987). The fruits of aonla are reported to contain hydrolysable tannins, emblicannin A and emblicannin B, along with pedunculagin and punigluconin (Ghosal et al., 1996). These fruits were to be considered rich source of ascorbic acid until Ghosal et al. questioned its presence in 1996. However, in 2006, Scartezzini et al. proposed a reliable HPLC-DAD (Fig. 5.1) for the identification and quantification Table 5.4

Chemical composition of fresh aonla fruits

Characteristic

Composition

pH TSS (°B) Acidity (%) Ascorbic acid (mg 100g−1) Reducing sugar (%) Non-reducing sugar (%) Total sugar (%) Pectin (% calcium pectate) Tannin (% gallotannic acid) Protein (%) Moisture (%)

2.45 13.50 2.25 590.00 2.45 0.79 3.31 0.55 0.50 0.93 84.56

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Aonla (Emblica officinalis Gaertn.)

Fig. 5.1

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HPLC profile of methanolic extract of emblica monitored at 280 NM.

of ascorbic acid and further indicated that high antioxidant activity is due to a large percentage of the presence of ascorbic acid (Scartezzini et al., 2006). Recently, Raghu et al. (2007) compared ascorbic acid content of the fruits by conventional colorimetric estimation, specific enzymatic method and as the o-phenylene diamine derivative of dehydroascorbic acid and found contents of 34 to 38 mg of vitamin C equivalent to 100 g of fresh weight. The free and bound phenolics of aonla fruits showed high content of phenolic compounds (126 and 3.0 mg g−1). Gallic acid and tannic acid were identified as the major antioxidant components in phenolic fractions of aonla (Kumar et al., 2006).

5.4

Preharvest factors affecting fruit quality

Many factors, especially cultural practices and environmental conditions, can influence the development of aonla and therefore influence its quality. Cultivar, fibre, tannin and vitamin C content are the important components of aonla fruit quality. Some of the cultivars (‘NA-6’, ‘NA-7’ and ‘Banarasi’) have low fibre content and are therefore preferred for processing. ‘Hathijhool’, ‘Chakaiya’, and ‘Kanchan’ are prolific bearers but contain high amount of fibre as well as tannins. Vitamin C and fibre content in different aonla cultivars vary from 500 to 1500 mg 100 g−1 and 0.35 to 1.50 %, respectively. Although no systematic work has been done on nutritional requirement of aonla fruits, aonla trees need an adequate supply of nutrients for rapid growth, flowering and fruiting. Ten-year-old and older trees should get a fertilizer dose of 100 g N + 500 g P2O5 + 1000 g K2O plus 1000 kg Farm Yard Manure. In sodic soil, 100 g of boron, zinc sulphate and copper sulphate should also be incorporated along with fertilizers as per the tree age and vigour. Two sprays of micronutrients during August-September containing B, Zn, Cu (0.4 %) along with hydrated lime is helpful in reducing fruit drop, improving fruit quality and reduction in fruit

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necrosis particularly in ‘Francis’. Boron deficiency affects the appearance of fruits and results in pinkish spots on the fruit surface (Pathak et al., 2003). Treatment with calcium nitrate, calcium chloride and borax increased shelf life, lowered physiological weight loss and reduced respiration rates (Yadav and Singh, 1999). Treatment with 1 % calcium nitrate resulted in lowest weight loss (11.09 %) and decay loss (14.43 %) and prolonged shelf life up to 20 days (Yadav and Singh, 1999). Three sprays of borax (0.6 %) in the month of September reduced the browning in fruits (Sharma, 2006). Postharvest application of calcium nitrate (1 %) minimized weight loss during the storage period and no pathological loss was observed with borax treatment (4 %) during up to nine days of storage (Nath et al., 1992).

5.5

Postharvest handling factors affecting quality

5.5.1 Temperature management Aonla fruit as the case for almost all subtropical fruits is very sensitive to improper temperature management. Chilling injury (CI) is manifested initially in aonla fruit as brown discolouration on the skin, often accompanied by pitting and water soaking lesions. In more severe cases the flesh is also affected. CI also can cause uneven ripening, poor colour and fruits more prone to decay. Generally, storage below 6°C results in CI in aonla fruits. Not much work has been carried out in cultivar differences for susceptibility to CI in aonla. The best control of CI is to avoid exposure to temperatures lower than optimum. The optimum temperature for aonla storage was found to be 12°C (Pareek, 2010b). 5.5.2 Physical damage Aonla fruits are susceptible to surface abrasions at the time of harvesting. In India fruits are generally harvested by beating the twigs or shaking the plant, with fallen fruits being physically damaged. Fruits with scuffs or bruises on the surface make them unsuitable for processing, especially for making preserves. Damaged and wounded fruits are characterized by a high rate of respiration as well as a high rate of ethylene production. These fruits are more susceptible to microbial attack and postharvest decay. Therefore, careful harvesting, proper sorting, packaging and storage are essential requirements to maintain the postharvest quality of aonla fruits. 5.5.3 Water loss Aonla fruits are harvested in India during November to March, when temperatures are high enough to cause high rates of water loss and to reduce the quality of the fruit if pre-cooling and low temperature storage are delayed after harvest. Exposure to sunlight adversely affects the quality as well as marketable quantity by weight. Therefore, harvested fruits should be transported to the packinghouse, processor or market as soon as possible.

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Physiological disorders

5.6.1 Chilling injury Chilling injury (CI) occurs in aonla fruit at temperatures below 6°C and the optimum temperature for storage is 12°C. Pitting, peel discolouration, water soaked lesions on the surface followed by irregular ripening with poor colour and increased susceptibility to decay are the symptoms of CI in aonla fruit (Pareek, 2010b).

5.6.2 Internal fruit necrosis Internal fruit necrosis is characterized by browning of the innermost mesocarpic tissues at the time of endocarp hardening, followed by browning of the epicarp, resulting in the development of black areas on the fruit surfaces. In severe cases, the mesocarp of the affected fruits may turn completely black, becomes corky along with the development of gummy pockets on the fruit surface. The ‘Francis’ cultivar is highly susceptible to fruit necrosis, followed by ‘Banarasi’. This disorder has been reported to be due to the deficiency of boron and can be corrected by three sprays of borax (0.6 %) during the months of September and October at fortnightly intervals (Sharma, 2006).

5.6.3 Pink colouration In recent years, it has been noticed in many orchards in India that spots of pink colour appeared on aonla fruits. This disorder is due to boron deficiency. Fruit marketability is adversely affected. Two sprays of borax in September and October have been shown to reduce the pink colouration on fruit surface (Pareek, studies currently in progress).

5.6.4 White specks The development of white specks on the surface and interior of the fruit is a major hindrance during curing and pickling. The white-specked fruits become very poor in appearance and mushy in texture. Studies to evaluate the effects of various pretreatments on the development of white specks were carried out (Premi et al., 1998). The extent of white specks was lower in aonla fruit segments preserved in steeping solution containing 10 % salt and 0.04 % potassium meta-bi-sulphite than in those preserved by dry, salting with 10 % salt and 0.02 % potassium meta-bi-sulphite during one month of storage. The fruits that developed white specks were poor in texture and brownish in colour. These white specks were isolated and extracted with water, then purified as white solid matter. This was found to be insoluble in water and other common organic solvents but soluble in alkali solutions. The white solid matter was mucic acid (D-galactaric acid). Its mineral analysis indicated the formation of an unknown complex of this compound with calcium and potassium (Premi et al., 1998).

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Postharvest biology and technology of tropical and subtropical fruits

Pathological disorders

Aonla is a hardy crop and there are few known effects of diseases during production in India. However, aonla rust and postharvest diseases are major constraints. In China, brown spot (Phyllostica emblica), false anthracnose (Kabatiella emblica), Pestalotiopsis leaf spot (P. heterocornis) and powdery mildew (Oidium sp.) were reported. The first two species are described as new species and Pestalotiopsis leaf spot was a newly reported pathogen for China (Zhang and Qi, 1996).

5.7.1 Rust Rust is a major and economically important disease in aonla. A maximum disease incidence of 21% was noted in the last week of December and the development was higher when relative humidity increased and temperature decreased (Anonymous, 1989). Black pustules develop on fruits, which later develop in a ring pattern. In an advanced stage, many pustules coalesce together and cover a large area of the fruit surface. A papery covering covers these pustules at the initial stage and black spores are exposed when the covering ruptures. Aonla rust is caused by an obligate parasite (Revenelia emblica Syd.), which requires the live host for infection and establishment under favourable conditions. Integrated approaches should be followed for effective control of aonla rust, which involves cultural methods, chemical control and use of resistant cultivars. Clean cultivation is essential and infected fruits and leaves must be collected and destroyed. Proper pruning to maintain optimum canopy density and avoiding humidity build-up results in less incidence and intensity of infection of the pathogen. Three sprays of 0.5% wettable sulfur or Zineb (0.2%) at intervals of one month starting from the month of July can be useful to control rust (Tyagi, 1967). The commercially cultivated cultivars ‘Chakaiya’, ‘Krishna’, ‘Kanchan’, ‘NA-7’, and ‘NA-10’ are relatively susceptible to rust. Out of nine cultivars screened under Faizabad (India) conditions, ‘NA-6’ was found to be resistant. No cultivar was found to be immune to rust (Anonymous, 2002).

5.7.2 Anthracnose Anthracnose is the second major disease in aonla fruits. The causal organism of the disease is the Colletotrichum state of Glomerella cingulata. It appears on leaflets and fruits during August to September. Initial symptoms of the disease appear in the form of minute, circular, brown to grey spots with yellowish margin in leaflets, and severely affected leaves dry up. In fruits, the initial symptoms are pin head sized spots, which are dark brown to pink to red. As the pathogen proliferates, spots change colour, eventually becoming dark brown spots with red margin and yellow halos (Misra and Shivpuri, 1983). To control the disease, infected fruits and leaves have to be removed at the initial stage of disease appearance. Spraying with 0.1% Carbendazim or 0.2% Difolatan can help control the disease (Nallathambi et al., 2007).

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5.7.3 Fruit rots Other diseases causing fruit rots can cause considerable economic losses in aonla. Thirteen types of different fungi have been isolated from stored fruits of aonla (Mishra, 1988). Phoma rot, Alternaria, Cladosporium, Pestalotia, Penicillium and Aspergillus are the common rots associated with aonla. Among all types of rots, Phoma rot is most widespread in India. Different species of Phoma cause different fruit rots in aonla. Dry rot of aonla is caused by Phoma emblicae (Jamaluddin et al., 1975) or Phoma putanium (Pandey et al., 1980) and soft rot is caused by Phoma phyllanthi (Lal et al., 1982). Small pinkishbrown necrotic spots extending towards both ends of the fruit, forming an eyeshaped spot, are the characteristic symptoms of this disease. Infected fruit appears dark brown and crinkled with softening of underlying tissues. In severely infected fruits, lesions coalesce forming bigger pustules (Nallathambi et al., 2007). Not many studies have been made on physiological changes in fruits due to Phoma infection, however, it is known that postharvest infections of aonla fruits by Phoma exigna result in a very rapid decrease in vitamin C content compared with the slow decrease during storage of healthy fruits (Reddy and Laxminarayana, 1984). Alternaria alternata (Fr.) Keissler is responsible for Alternaria rot. Slightly depressed, brown to dark brown circular necrotic lesions appear on the fruit. Sometimes concentric rings are also present on these spots. The smaller spots coalesce to form larger spots. The centre portion of the infected tissue becomes soft and pulpy. The fungus survives in debris and soil. Dropped fruits and fruits touching the soil become infected and the disease spreads later by dissemination of spores through the air. Cladosporium rot is also known as dry rot and caused by Cladosporium tenuissiumum in November to February and by C. cladosporoids in February to March. Disease starts as a colourless area, where slightly soft spots develop and later progress into a circular manner. The diameter of the lesions varies from 1.0 to 1.5 cm in a 1-week-old infection. Subsequently, light to dark brown necrotic lesions are the characteristic symptom (Jamaluddin, 1978). Penicillium rot is also known as soft rot and caused by Penicillium digitatum, P. citrinum, and P. isolandicum. Initially water soaked lesions appear near brown patches on the fruit surface. As the rot progresses, three distinct colour zones of bright yellow, purple brown and bluish-green are observed on the infected fruits. In advanced stages of infection the fruits emit a foul smell. Other less-reported rots are caused by Aspergillus niger (Jamaluddin et al., 1979), Penicillium digitatum (Taneja et al., 1983), Aspergillus luchunensis, Fusarium acuminatum (Sumbali and Badyal, 1990), Cytospora sp. (Tandon and Verma, 1964) and Pestalotia cruenta (Tandon and Srivastava, 1964). Management of fruit rots Decay control is accomplished with an adequate preharvest and postharvest integrated program. Postharvest wash water should contain 100 to 150 ppm of sodium hypochlorite plus fungicides depending on the source and extent of the

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problem. Proper handling of the fruit during harvest, packaging, elimination of mechanical injury, rapid cooling, maintenance of optimum temperature and maintenance of hygienic conditions are essential for decay control. Several chemicals are applied to aonla both pre- and postharvest for control of fruit rots. Two preharvest sprays of 0.01% calcium nitrate with 0.1% Topsin M were found to be effective for control of rot (Yadav and Singh, 1999). Treatment with Topsin M and Bayleton controlled Penicillium oxalicum and Aspergillus niger for two to three weeks. Four percent borax as a postharvest dip resulted in effective control of fruit rot (Nath et al., 1992).

5.8

Insect pests and their control

The major pests of aonla are Virachola isocrates, Betousa stylophora Swinhae, Gracillaria acidula, Celepa celtis, and Inderbela tetraonis belonging to the order Lepidoptera, Ceciaphis emblica, Nipaecoccus vastator and Oxyrhachis tarandus of Homoptera, Myllocerus discolor of Cleoptera and termite Odontotermes spp. of Isoptera.

5.8.1 Fruit borer (Virachola isocrates) Borers lay eggs on young fruits, and the caterpillars bore into the fruits and feed on developing seeds. The insects make holes in the fruit, which facilitates the entry of microorganisms resulting in decay of fruits. To prevent the spread of the insects, infested fruits should be collected and destroyed. A spray of Endosulphan (0.05%) is effective during July to August. Pomegranate cultivation should be avoided near aonla orchards.

5.9

Postharvest handling practices

5.9.1 Harvest operations Careful harvesting is important in aonla fruit because damaged fruits are not useful for processed products. Fully developed fruits, which show signs of maturity, should be harvested in a timely fashion. Delay in harvesting results in heavy dropping of fruits particularly in cultivars like ‘Banarasi’ and ‘Francis’, and also adversely affects the following year’s bearing. The recommended method of harvesting is hand picking of individual fruits. Shaking of twigs of the tree is a common practice in India, but fruits are damaged when they drop on the ground. These fallen fruits are the source of soil-borne microorganisms, which can cause rots during storage. Therefore, fruit harvesters should use long ladders and carry cotton or jute bags for collecting the fruits. Fruits should be harvested early in the morning or in the evening to avoid high field temperatures. Harvested fruits should be immediately moved under shade.

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Packinghouse practices

Grading Aonla may be graded according to weight or diameter. Grading has not been standardized in aonla, but the authors recommend that aonla fruits should be graded into three size grades as shown in Table 5.5. Fruits may also be graded on weight basis (A grade = 50 ± 5 g, B grade = 40 ± 5 g and C grade = 30 ± 5 g). Highest physiological loss in weight (PLW) was observed in C grade fruits followed by B grade and was least in A grade fruits during eight days of storage at ambient temperature. PLW in the ‘Francis’ cultivar was 12.50, 16.00 and 20.50 % in A, B and C grade fruits respectively on the eighth day of storage. PLW was 6.50, 11.30 and 14.50 % for A, B and C grade fruits in ‘Chakaiya’ (Pareek et al., 2008) (Table 5.6). Final destination or utilization of aonla fruits is based on the size, weight and fibre content of fruits. Large-sized fruits with 45 ± 5 g weight and low in fibre are used for preserves, candy and pickle making, while small-sized fruits with medium to high fibre contents are used in making of medicinal products, i.e. chavanprash. Misshapen fruits or fruits with necrosis and blemishes can be peeled, trimmed and used in making trifla and for drying or powder making. Packaging At present packaging is inadequate for aonla handled in India. Aonla fruits are packed in cloth sacks of 50 to 100 kg capacity. These fruits suffer vibration and Table 5.5

Recommended grades for aonla fruits

Grade

Description

A

Large-sized fruit: diameter 4.5 cm and above, free from blemishes; weight 50 + 5g Small-sized fruit: diameter less than 4.5 cm, free from blemishes; weight 40 + 5g Defective fruits, i.e. blemished, scarred and necrotic fruits; weight 30 + 5g

B C

Table 5.6 Water loss (%) during storage of aonla fruits in different size grades Grades

cv. ‘Francis’ A B C cv. ‘Chakaiya’ A B C

Days after harvest 2

4

6

8

3.20 4.50 6.00

7.50 8.75 13.80

11.30 14.50 16.00

12.50 16.00 20.50

1.50 2.80 4.75

3.50 7.25 9.00

5.20 9.50 12.50

6.50 11.30 14.50

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compression injuries during stacking and transportation in these large sacks. Corrugated fibre boxes (CFB) of appropriate size (20 kg capacity) should be used. Lightweight paper liners should be used inside the CFB cartons to reduce abrasions. Minimum spoilage (16.0%) was reported in CFB with newspaper liners followed by CFB boxes with polythene liners (17.0%), and was highest in cloth sacks without any liner (30.19%) after 13 days of storage (Singh et al., 2005b). The effects of cloth sacks, corrugated fibreboard box, pigeon pea basket, wooden crate and bamboo basket with polythene liner as packaging material were studied for the transportation and storage of aonla cv. ‘NA 7’ at an ambient temperature of 21 ± 2°C (minimum) and 33 ± 2°C (maximum) with a relative humidity of 65 ± 3%. Minimum spoilage loss was reported in fruits kept in CFB with newspaper liners. The same treatment also resulted in the lowest respiratory activity (81.1 mg CO2 kg−1 h−1) and exhibited 11 days of economic shelf life under ambient conditions. The highest respiration rate was reported for aonla handled in cloth sacks (90.0 mg CO2 kg−1 h−1) on the thirteenth day of storage (Singh et al., 2009). Wooden crates of 40 kg capacity with polythene liners were also found to be suitable for packing and long distance transportation of aonla fruits. % weight loss and bruising were minimized in this sturdy container as compared to cloth sacks (Singh et al., 1993). 5.9.3 Recommended storage and shipping conditions The fruit availability period of fresh aonla is two to three months, and typically there is a seasonal glut during November to mid-January. Therefore, storage of aonla fruits at appropriate temperature is essential to extend the availability period and to stabilize the prices in the market. The fruits may be kept successfully in cold storage for seven to eight days at 12°C and 85 to 90 % relative humidity. Very little research has been done on low temperature, modified atmosphere or controlled atmosphere storage of this fruit. The shelf life is very short at ambient temperatures and differs by cultivar. Pareek et al. (2009) reported the shortest shelf life in ‘Francis’ cultivar (6 days) and highest in ‘Chakaiya’ (8 days) at ambient temperature. Singh and Kumar (1997) stored fully mature aonla fruits using four different treatments: at room temperature, under modified storage conditions (packed in low density polyethylene pouches), in a zero energy cool chamber (which provides evaporative cooling conditions and very high relative humidity) and in a zero energy plus modified storage conditions. It was found that decay was at a minimum (26.56%) under modified storage conditions on the twenty-fourth day of storage, whereas it was at the maximum (48.70%) in a zero energy cool chamber. Nath et al. (1992) studied the effect of postharvest treatments on shelf life of aonla fruits with calcium nitrate (1%), GA3 (50 ppm) and borax (4 %) and found that the physiological loss in weight and pathological loss increased with the length of the storage period. Calcium nitrate (1%) treatment minimized weight loss during the storage period and no pathological loss was observed with borax treatment during up to nine days of storage.

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To enhance the shelf life of aonla fruits of a local cultivar, Patel and Sachan (1995) studied the effects of calcium nitrate (1%), GA3 (40 ppm), Cycocel (400 ppm) and kinetin (10 ppm). Fruits were dipped in these solutions, packed in perforated polythene bags and stored at ambient temperature. The physiological loss in weight and decay percentage increased with the increase in storage period. Calcium nitrate (1%) was the best treatment to minimize weight loss. No decay was observed during up to nine days of storage in kinetin (10 ppm) treated fruits. GA3 (40 ppm) treatment resulted in better retention of vitamin C during storage of aonla fruits. Singh et al. (2005a) recorded the least physiological loss in weight (2.12 to 16.00% and 2.15 to 16.34%) and spoilage (2.40 to 15.00% and 2.50 to 15.60%) and storage duration of 11 days in fruits treated with calcium nitrate at 1.5% + perforated polythene bag, and GA3 100 ppm + perforated polythene bag. The same treatments also resulted in low respiratory activity (72 to 82 mg CO2 kg−1 h−1). The untreated control in these studies had only 7 days of economic life under ambient conditions. Singh et al. (2005a) assessed four aonla cultivars (NA-7, NA-10, Krishna and Chakaiya) for their shelf life at ambient condition (18 ± 2°C and 65 ± 5% RH). In general, the aonla fruits showed browning of skin followed by loss of glossiness during storage. ‘Krishna’ and ‘NA-10’ were more prone to browning than ‘NA-7’ and ‘Chakaiya’. The cumulative physiological loss in weight, TSS, acidity and tannins increased, while ascorbic acid content decreased on prolonging the storage period in all the cultivars. ‘NA-10’ and ‘Krishna’ exhibited minimum loss in weight, TSS, ascorbic acid, and tannins in comparison to ‘Chakaiya’ and ‘NA-7’. Greenness (a chromacity value) was maintained in cultivar ‘NA-10’ and ‘Krishna’ followed by ‘Chakaiya’ during storage. Contrary to this, maximum yellowness index (based on L, a and b values) was recorded in ‘NA-7’ and minimum in ‘Krishna’. However, ‘NA-7’ exhibited the least browning compared to ‘Krishna’ during up to ten days of storage (18 ± 2°C and 65 ± 5 % RH). Therefore, ‘NA-10’ and ‘Krishna’ had better shelf life of ten days and retained high vitamin C content, glossy and green appearance compared to ‘NA-7’, which can be stored for only six to eight days under ambient conditions.

5.10

Processing

Aonla becomes ready for harvesting from mid-November to the first week of January. Aonla is not consumed fresh or raw, as it is acidic and astringent. The excellent nutritive and therapeutic value offers great potential for processing into several quality products, i.e. preserves (murabba), squash drinks, candy, jelly, jam, syrup, pickles, chutney, preserved pulp, blended beverage, carbonated drinks, Ready-to-Serve drinks, supari, churan, powder, barfi, laddoo and segments in sugar syrup. The postharvest losses in aonla vary from 30 to 40% due to its perishable nature and gluts during harvesting time, and the resulting decline in quality reduces the market value of the fruit. Proper temperature management during

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transport and short-term cold storage could reduce these losses, however, value addition through processing would be the most effective tool for economic utilization of the fruits during the peak of production. 5.10.1 Traditional and new methods of processing Aonla has been in use for pickles and preserves for ages in India and the methods employed were based on traditional knowledge. Aonla has been an important ingredient for chavanprash, an ayurvedic health tonic. Traditional methods used for processing are unhygienic in nature, time consuming and nutritive losses can be high. The manual methods of processing are laborious, costly and cannot maintain the quality of the finished products. Minor accidents have been reported during manual operations such as pricking and shredding, and the shelf life of traditionally prepared products tends to be lower and the quality inferior. Modern methods for preparing different aonla products are hygienic, and provide maximum retention of nutrients, especially vitamin C. There is an urgent need to design a full line of processing equipment including graders, segment separator, pricking machine, shredder, etc. The engineering of suitable machines will improve quality to international standards so that products can better compete in the international market (Goyal et al., 2008). 5.10.2 Aonla products Aonla fruits are normally used to make preserves. A preserve is made from fully matured aonla by cooking fruits whole or in the form of large pieces in heavy sugar syrup, until the fruit becomes tender and transparent. Freshly made preserves are wholesome and have an attractive appearance. When fruits are stored for a long period before processing, their natural colour and flavour deteriorate on account of oxidative changes. Preserves should therefore be made only during the season, unless there are adequate facilities to store the fruits properly so that they are available in the off-season as well. No proper attention has yet been given to improving the preparation of other products like jam, jellies, squash, candy, toffee, barfi, laddoo, and the preserved pulp of aonla fruits. Candy is an intermediate moisture food that is prepared after shade drying of drained fruits impregnated with cane sugar or glucose. Like other fruits, aonla can also be processed into good-quality pulp. This can be used as base material for preparations of different products, i.e. squash, syrup, jam and nectar. Thus, there is an overriding need to develop and popularize several other value added products of aonla as fruit production increases. Various studies suggest that many types of value-added products of aonla can be prepared, and a great potential exists for better utilization of aonla. However, more attempts are needed to standardize the procedures for preparation of various new value-added products and to assess the suitability of aonla cultivars for preparation of these products. Removal of astringency from aonla fruits is an important step prior to the preparation of various value-added products. At present

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different ingredients or chemicals such as salt, alum and lime are used to counteract the astringency in aonla. However, very little information is available with regard to their comparative safety and effectiveness in the removal of astringency from different aonla cultivars. 5.10.3 Cultivar screening for aonla processing Processed products of good quality can be made only from good quality raw material. Singh and Pathak (1987) evaluated five cultivars of aonla for processing based on their physico-chemical properties and organoleptic quality. Out of these five cultivars ‘Kanchan’ and ‘Krishna’ were suitable for candy and jam. ‘Banarasi’ was suitable for drying and ‘Chakaiya’ was suitable for pickles, chutney and syrup. Bhagwan (1992) observed that ‘NA-9’ was ideal for candy making. Singh et al. (1993) also reported that ‘NA-6’ is an excellent cultivar of aonla for making good quality candy. Nath and Sharma (1998) reported that ‘Chakaiya’ is good for making nectar, squash, syrup and jam products, whereas ‘Banarasi’ is better for candy and pickle preparation. Nath (1999) observed that ‘Chakaiya’ was suitable for beverages (nectar, squash and syrup) and jam whereas ‘Banarasi’ was better for candy and pickle preparation. Singh et al. (2004) evaluated five cultivars (‘NA-6’, ‘NA-7’, ‘NA-10’, ‘Kanchan’ and ‘Chakaiya’) for fruit processing. ‘NA-6’ recorded the lowest content of fibre, higher content of pulp and TSS with moderate fruit size and ascorbic acid content while ‘NA-7’ had a higher content of ascorbic acid. These cultivars have also higher productivity and fruits are free from necrosis or internal browning, hence they seem to be ideal for processing. The composition of selected aonla cultivars is provided in Table 5.7. 5.10.4

Effect of pricking, soaking and blanching treatments on quality of aonla products The retention of nutrients such as ascorbic acid in the final aonla products depends on the methods of preparation. Pricking, soaking and blanching of aonla fruits are necessary to render the preserves and candies soft and to facilitate uniform Table 5.7

Composition of selected aonla cultivars

Varieties

Average Pulp (%) Fibre (%) Seed (%) TSS (%) Acidity Ascorbic fruit (%) acid (mg weight (g) 100 g−1)

NA-6 NA-7 NA-10 Kanchan Chakaiya CD at 5%

41.40 42.90 44.84 30.92 35.82 4.26

94.27 92.97 93.57 92.36 93.61 0.97

0.87 1.33 1.30 1.40 1.93 0.51

4.86 5.70 5.13 6.24 43.46 0.96

11.12 10.96 10.14 10.86 9.44 1.04

Source: Singh et al. (2004)

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1.80 1.95 1.82 1.72 2.26 0.52

641.27 733.63 626.82 603.64 655.64 86.38

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absorption of sugar (Kalra, 1988). There are many reports on losses of nutrients during preparation of candy and preserves. The loss of ascorbic acid content during preparation of candy has been observed in aonla (Pathak, 1988; Tripathi et al., 1988; Bhagwan, 1992; Singh et al., 1993). Sastry and Siddapa (1959) found that prolonged brine treatments of aonla destroy the ascorbic acid content. The ascorbic acid content of aonla preserves decreases during preparation (Sethi, 1980). Sethi and Anand (1982) found that 55.5 % of the ascorbic acid content is lost during preparation of intermediate moisture food aonla preserves (including pricking, soaking and blanching) and only 45.5 % ascorbic acid was retained in the final product. Tripathi et al. (1988) reported that the aonla candy retained 108.6 mg 100 g−1 ascorbic acid as against initial value of 571.76 mg 100 g−1 in the fresh fruit. Anand (1970), while studying the effect of certain pretreatments on the loss of tannins and vitamin C in aonla preserves, found that soaking and blanching of the fruit resulted in heavy losses of these constituents. Damame et al. (2002) reported that unblanched dehydrated products were found to be superior to all the blanched dehydrated products in terms of vitamin C retention over a 6-month storage period. Aonla candy and preserve were found to be the most unsuitable sources of vitamin C. Among the unblanched products, aonla pulp recorded the highest vitamin C content, followed by supari. Among the blanched products the aonla supari, treated with 2 % salt, was found to be superior in vitamin C content. Overall results indicate that aonla pulp, supari and juice are the most suitable sources of vitamin C due to minimum losses of this vitamin during storage. Jain and Khurdiya (2002) observed that blanching of the aonla fruit prior to juice extraction significantly improved the juice recovery, increased the density and tannin content of the juice but reduced the vitamin C content by 12 %. Addition of water increased the juice volume but diluted the juice and reduced the water-soluble constituents. Higher water-soluble constituents and ascorbic acid contents were obtained by blanching the fruits and separating the segments. The astringency in aonla fruits is due to the presence of polyphenols or tannins, which make them unpalatable but have therapeutic value (Sastry et al., 1958). Astringency can be removed by curing with either salt or lime. Sethi (1980) recommended blanching of aonla fruits for 4 minutes in boiling water while Sethi and Anand (1983) found that 25 % of ascorbic acid and 24.4 % of tannins in aonla are lost during blanching. Geetha et al. (2006) observed that blanching done prior to processing of aonla preserve has a marked effect on all the physico-chemical constituents of aonla. Ascorbic acid content during the process of blanching was reduced significantly from 563.12 mg 100 g−1 (before blanching) to 434.95 mg 100 g−1 (after blanching) showing a loss of 19.20 %. Similarly, Total Soluble Solids, acidity, total sugars, reducing sugars, non-reducing sugars, moisture and pectin content showed a loss of 10.67, 30.78, 4.95, 5.83, 2.45, 2.20 and 21.60 %, respectively with blanching. Phenolic compounds are important in determining colour and flavour of fruits. The losses of total phenolic compounds in finished aonla candy have been reported by Pathak (1988) and Tripathi et al. (1988) as compared to fresh fruit. Sethi and

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Anand (1982) observed the loss of tannins during preparation of intermediate moisture foods of aonla as compared to initial values in fresh fruits. Pathak (1988) reported that a 2 % salt solution for soaking of pricked aonla fruits was considered organoleptically ideal. Bhagwan (1992) and Singh et al. (1993) observed that organoleptically good quality aonla candy was prepared with 2% salt and alum soaking of pricked fruits, each for 24 hours. 5.10.5 Techniques for manufacturing processed products The most suitable techniques determined by organoleptic evaluation by Pareek (2010a) for some of the important aonla products are described here. Pulp extraction technique Nath (1999) carried out a study on the extraction of aonla pulp and suggested a method for preparation of aonla pulp from fully matured fruits. In this process, the fruits are blanched in boiling water for about ten minutes to separate the segments from the seed. An equal quantity of water is added to the segments during pulping. If the pulp is to be preserved, it should be heated to 75°C and then cooled to room temperature. Potassium meta-bi-sulphite (2 g kg−1 of pulp) should be mixed thoroughly and the pulp should be packed in sterilized bottles and then sealed. Vitamin C losses can be minimized by using an improved pulp extraction technique, in which a shredder machine is used for removing seeds instead of the boiling water treatment. Pickles Small-sized aonla fruits, which are not suitable for preparation of preserves and other confectionary items, may be utilized for Indian pickle making. To improve upon the texture of the fruit and also to remove astringency, brining is important in pickling. When pickles are ready a few days after treatment, they can be stored at room temperature. Premi et al. (2002) standardized the method for preparation of instant oil-less pickles from aonla. Two cultivars of aonla (‘Desi’ and ‘Chakaiya’) were used for the preparation of dehydrated oil-less pickles. The overall quality of dehydrated pickles made from pretreated segments of ‘Desi’ cultivar was better than those made from ‘Chakaiya’. For curing aonla fruits for pickling, brining along with potassium meta-bi-sulphite treatment was found to be more effective for longterm storage than was dry salting or other pretreatments for the control of white specks, retention of texture and retention of nutrients in both cultivars. The drying rate was faster for pickles made from cured and steam blanched segments of ‘Desi’ than for other cultivars. Juice extraction Jain and Khurdiya (2002) standardized a procedure for the extraction of juice from aonla fruits. Blanching the fruits prior to juice extraction significantly improved the juice recovery, increased the density and tannin content of the juice

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but reduced the vitamin C content by 12%. Higher soluble constituents and vitamin C content were obtained by blanching the fruits and separating the segments. Among the methods of juice extraction, centrifugal juice extraction recorded higher density, soluble constituents and higher vitamin C and tannin contents as compared to crushing and pressing whole or segments of aonla fruits. Ready-to-serve (RTS) drinks Ready-to-serve drinks can be prepared by using 10 % pulp with 12 % total soluble solids and 0.3% acidity. Juice is extracted separately and sugar syrup of the desired strength prepared separately by boiling sugar with water and adding citric acid towards the end of boiling. After cooling syrup to room temperature, mix the syrup and juice, homogenize, fill and crown cork the bottles. The bottles are then pasteurized in a boiling water bath for 20 minutes, air-cooled and stored for use. Various workers have explored the possibilities of utilizing aonla fruit for the preparation of blended juice and beverages (Prasad et al., 1968; Singh and Kumar, 1995; Nath, 1999; Deka et al., 2001). If aonla juice is blended with other fruit juices for the preparation of ready to drink beverages, it boosts their nutritional quality. These fruit juices in turn improve the acceptability of aonla juice. Deka et al. (2001) conducted various experiments to study the feasibility of blending juices and pulp from lime, aonla, grapes, pineapple and mango in different preparations for the manufacturing of a ready-to-drink fruit juice beverage. The highest sensory scores were obtained with a formulation comprising of 95% lime and 5% aonla juice. Jain and Khurdiya (2004) conducted an experiment to develop vitamin C rich ready-to-serve beverages prepared from apple, lime, pomegranate, Perlette and Pusa Navrang grape juices fortified with aonla juice. For juice extraction, aonla fruits were blanched, seed removed manually, and segments were fed into a centrifugal juice extractor. The juice was strained and pasteurized at 90°C for one minute, poured into sterilized glass bottles, crown corked, and air-cooled. Juice from other fruits was extracted and pasteurized using standard methods. The aonla juice was mixed with each of the apple, lime, pomegranate, Perlette, and Pusa Navrang grape juices in the ratio of 0:100, 10:90, 15:85, 20:80, 25:75, 80:70, and 50:50. All the 40 blends were then adjusted to proportions of water, sugar, and citric acid in order to contain 10 % juice, 10 % TSS, and 0.22 % acidity except the lime–aonla blend which had 5 % juice, 10 % TSS, and 0.22 % acidity. All the blends were pasteurized at 90°C for one minute before packing in sterilized glass bottles of 200 ml capacity. On the basis of overall sensory quality and vitamin C content, the ready-to-serve beverage prepared by blending aonla and Pusa Navrang grape juice in the 20:80 ratio was reported to be the highest rated. Squash and syrup To prepare 15 litres of aonla squash drink, 3.75 kg juice/pulp should be mixed in sugar solution to prepare a final product with 45 % juice/pulp, 50 % Total Soluble

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Solids, and 1% acidity (Fruit Products Order of India specifications). Syrup from the aonla pulp can be prepared according to Fruit Product Order specifications, i.e. 45% juice/pulp, 68% TSS and 1.2% acidity. Nectar Nectar can be prepared by using 10 % pulp with 12 % TSS, 0.3 % acidity and 350 ppm SO2. To prepare 10 litres of aonla nectar, 1 kg pulp should be mixed in sugar solution. The syrup can be prepared by dissolving 1.2 kg sugar and 20 g citric acid in 7.6 litres of water by slow heating. Add the pulp after cooling the solution. Mix in the preservative (1 g potassium meta-bi-sulphite) and homogenize. Jams To prepare aonla jam, the pulp is extracted from the fruit, mixed with the desired quantity of sugar and citric acid and this mixture is cooked to desired consistency. The end point judged by hand refractometer (68°Brix) or by drop test or sheet test. Herbal extracts added to aonla pulp for preparing jam improved medicinal quality. Fifty percent aonla pulp, 75 % asparagus + 2 % ashwagandha extract with 68 % Total Soluble Solids and 1 to 2 % acidity was reported to be the best combination (Singh et al., 2005e). Candy Aonla fruit can be utilized for making excellent quality candies or intermediate moisture food (IMF). Pathak (1988) described the technology for preparation of aonla candy. Aonla candies are becoming popular because of minimum volume, higher nutritional value and longer storage life. Tandon et al. (2003) found that candy prepared from lye-peeled fruits of aonla showed decreased content of ascorbic acid compared to blanched fruits. The candy prepared from ‘Lakshmi-52’, ‘Kanchan’ and ‘Chakaiya’ was found the best quality. Singh et al. (2005e) prepared aonla candy with four different techniques (whole and segmented fruits with either sugar or pectin coatings). Candy prepared from segmented fruit with pectin coating recorded the highest organoleptic score because of its attractive colour and flavour, followed by whole fruit candy with pectin coating. Preserves Aonla fruits are normally used to make preserves. A preserve is made from fully matured aonla fruits by cooking them whole or in the form of large pieces in heavy sugar syrup, until they become tender and transparent. Preserves should be made from large fruits and dipped in 2 % common salt solution until the green fruit changes to a cream color, with replacement of the brine solution on alternate days. The fruits are thoroughly washed, pricked with a stainless steel pricker and then blanched in boiling water for 4 to 5 minutes. Sugar equal to the weight of

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fruits is sprinkled over the fruit and the batch is stored overnight. The strength of sugar syrup should be increased by 10°Brix on at 2-day intervals until it reaches 75°Brix. Chavanprash Chavanprash is a health tonic described in the Indian system of medicine known as Ayurveda. It is prepared by mixing aonla pulp and sugar, then a variety of spices and medicinal plants extracts while cooking. The ingredients vary with the recipes and about 65 types of plant extracts are used to prepare this health tonic. Shreds and drying The osmo-air drying method was found to be the best method for drying aonla because of better retention of nutrients like ascorbic acid and sugars. The level of antinutrients like tannins was also found to be lower in osmo-air dried aonla compared to other methods of drying. Browning of the dehydrated fruits was also minimal in the case of osmo-air dried fruits. The nutrient content in osmo-air dried aonla was satisfactory after 90 days of storage (Pragati et al., 2003). It was found that the aonla powder prepared from pretreated ‘Chakaiya’ variety and mechanically dried can be stored effectively in high-density polyethylene (HDPE) packages under refrigerated conditions for three months without much loss in vitamin C, and with better overall acceptability in terms of appearance, flavour and texture (Sharma et al., 2002). Processes for producing dehydrated aonla powder have been standardized by Alam and Singh (2005). The pricked aonla fruits were blanched for 5 minutes in 5 % boiling salt solution containing 0.15 % NaHCO3 and 0.10 % MgO. The blanched aonla fruits were sulphited for 30 minutes in 0.5 % potassium meta-bisulphite. The treated fruits were sliced manually with a knife. For the dehydration of aonla slices, the mechanical dryer (50, 60 and 70°C), solar and cabinet dryers were used. They found that the mechanically dried slices contained higher in vitamin C content and were organoleptically superior to slices dried using the solar and cabinet dryers. Kavitha et al. (2003) studied the effect of osmotic dehydration on vitamin C content of aonla at different salt concentrations and different temperatures. The overall retention of vitamin C was found better in the unblanched osmotically dehydrated and air dried samples. Alam and Singh (2010) studied the optimization of the osmotic dehydration process for aonla fruit in salt solution by using response surface methodology. The independent process variables for the osmotic dehydration process were osmotic solution concentration (5 to 25 % w/v salt), osmotic solution temperature (30 to 60°C), solution to fruit ratio (4 to 8 v/w), and process time (60 to 240 minutes). The osmotic drying process was optimized for maximum water loss, overall acceptability and minimum solute gain, colour change, and vitamin C loss. The optimum conditions were 22 % salt concentration, 44.5°C osmotic solution temperature, 6.5 solution to fruit ratio, and 60 minutes’ process time. Among the process variables, salt concentration has the most significant effect on water loss, solute gain, and overall acceptability; solution temperature has the most effect on colour change; and process time has the most effect on vitamin C loss.

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Murthy and Joshi (2007) dried aonla fruits under three different conditions: sun drying, hot air tray drying, and fluidized bed drying. Sun drying required the longest period of drying (660 minutes), while the shortest time of drying was for fluidized bed drying at 80°C with 115 m/minute air velocity (120 minutes). The retention of ascorbic acid in the samples dried using fluidized bed drying was greater as compared to those dried under the sun and in hot air trays. Methakhup et al. (2005) reported that aonla flakes subjected to vacuum drying at 75°C and at absolute pressure of 7 K Pa contains similar level of ascorbic acid retention compared to those dried by a low-pressure super heated steam at 65 and 75°C at absolute pressure of 7 to 13 K Pa. Tea Aonla tea is prepared from dried aonla flakes. Kongsoontornkijkul et al. (2006) investigated the effect of different drying methods, i.e. hot air drying, vacuum drying, and low-pressure superheated steam drying on the retention and degradation of vitamin C in dried aonla flakes. The effect of temperature of water used to prepare the tea on the release of ascorbic acid and on its later degradation was also investigated. Low-pressure superheated steam drying helped retain ascorbic acid in dried flakes better than did hot air and vacuum drying. Lower hot water temperature during tea preparation was recommended to retard ascorbic acid degradation.

5.11

Conclusions

Aonla fruit is one of the most nutritious fruits of India and its medicinal properties have long been known. Aonla cultivation is gaining popularity due to its commercial attractiveness to growers. It presents tremendous commercial opportunities for growers in difficult agroclimatic zones, such as dry regions of arid zones, salt affected soils and in ravines. Many processed products have been standardized for this fruit, but much of its basic biology, physiology and chemistry are not known. Some of the most basic postharvest information related to chilling injury, storage conditions, respiration and ethylene evolution rates are not well understood. The following are recommendations for future researchers. Aonla, like many other herbs, has been in use for centuries in India, but it is important that traditional knowledge of aonla is documented and protected through patents. The modernized and automated technologies used to produce certain aonla products need to be improved and patented. Scaling up the processing of selected products such as aonla pulp, powder or candy could attract investment by the international community. Marketing the attributes of aonla fruit to the global community can generate interest in the benefits of regular consumption of aonla value-added products. Documentation of respiration rate, ethylene evolution rate, pre and postharvest treatments, storage temperatures and relative humidity, packaging and transportation conditions, etc. are required for each commercial cultivar.

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Shelf-life studies of fruit juices should be conducted, to better understand the effects of different temperature treatments, carbonation, additives and techniques such as modified atmosphere packaging. The potential for extracting alkaloid and formulation of antioxidants tablets from aonla powder should be explored. Standardization of processing factors related to detection of bacteriological contamination, preservation methods and protocols, use of additives, pesticide residues, etc. is required.

5.12

References

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Sethi V. and Anand J. C. (1982), ‘Physico-chemical and microbiological quality of carrot and aonla preserves’, Indian Food Packer, 36, 38–43. Sethi V. and Anand J. C. (1983), ‘Retention of nutrients in carrot and aonla preserve’, Indian Food Packer, 37, 64–67. Sharma N., Trikhaa P., Athar M. and Raisuddin S. (2000), ‘In vitro inhibition of carcinogeninduced mutagenecity by Cassia occidentalis and Emblica officinalis’, Drug and Chemical Toxicology, 23, 477–484. Sharma R. R. (2006), Fruit Production: Problems and Solutions, International Book Distributing Company, Lucknow, India. Sharma S. R., Alam S. and Gupta S. (2002), ‘Storage study on dehydrated aonla powder’, Annual Convention of Indian Society of Agricultural Engineers, 35, 155–156. Shukla A. K., Bhargava R. and Shukla Anil K. (2007), ‘Heat unit summation – An index to predict fruit maturity in aonla’, Indian Journal of Horticulture, 64, 3, 231–233. Singh B. P., Pandey G., Sarolia D. K., Pandey M.K. and Pathak R. K. (2005a), ‘Shelf-life evaluation of aonla cultivars’, Indian Journal of Horticulture, 62, 2, 137–140. Singh I. S. (1997), ‘Aonla – An industrial profile’, Department of Horticulture, N.D. University of Agriculture and Technology, Faizabad, Uttar Pradesh, India, p. 17. Singh I. S. and Kumar S. (1995), ‘Studies on the processing of aonla fruits. II Aonla products’, Progressive Horticulture, 27, 1–2, 39–47. Singh I. S. and Pathak R. K. (1987), ‘Evaluation of aonla (Emblica officinalis Gaertn.) varieties for processing’, Acta Horticulturae, 208, 173–177. Singh I. S., Pathak R. K., Diwedi R. and Singh H. K. (1993), ‘Aonla Production and Post Harvest Technology’. Department of Horticulture, N.D. University of Agriculture and Technology, Kumarganj, Faizabad, Uttar Pradesh, India, p. 34. Singh R. and Kumar S. (1997), ‘Studies on the effect of different storage conditions on decay loss of aonla var. Chakaiya’, Haryana Journal of Horticultural Science, 26, 9–12. Singh S., Nagaraja A., Singh A. K., Joshi H. K., Bagle B. G. and Dhandar D. G. (2006), ‘Post Harvest Management in Aonla and Ber’. Central Horticultural Experiment Station, (Central Institute for Arid Horticulture), Vejalpur, Godhra, Gujarat, India, p. 25. Singh S., Singh A. K. and Joshi H. K. (2004), ‘Fixation of maturity standards in Indian gooseberry (Emblica officinalis Gaertn.) under semi arid ecosystems of Gujarat’, proceedings of First Indian Horticulture Congress, 6–9 November, Indian Agricultural Research Institute, New Delhi, India, pp. 341–342. Singh S., Singh A. K. and Joshi H. K. (2005b), ‘Effect of size grading on quality and shelf life of aonla (Emblica officinalis Gaertn.) cv. NA-7’, proceedings of National Seminar on Commercialization of Horticulture in Non-traditional Areas, Indian Society of Arid Horticulture, Central Institute for Arid Horticulture, Bikaner, India, February, 2005. Singh S., Singh A. K. and Joshi H. K. (2005c), ‘Prolonging storability of Indian gooseberry (Emblica officinalis Gaertn.) under semi arid ecosystem of Gujarat’, Indian Journal of Agricultural Sciences, 75, 647–650. Singh S., Singh A. K., Joshi H. K., Bagle B. G. and Dhandar D. G. (2005d), ‘Heat unit summation – an index for predicting fruit maturity in Aonla (Emblica officinalis Gaertn.) under semi arid tropics of Western India’, proceedings of 8th Indian Agricultural Scientists and Farmers Congress, BHU, Varanasi and Bioved Research and Communication Center, Allahabad, India, 20–22 February, p. 123. Singh S., Singh A. K., Joshi H. K., Bagle B. G. and Dhandar D. G. (2009), ‘Evaluation of packages for transportation and storability of aonla (Emblica officinalis) under semiarid environment of western India’, Journal of Food Science and Technology, 46, 2, 127–131. Singh V., Singh H. K. and Chopra C. S. (2005e), ‘Studies on processing of aonla (Emblica officinalis Gaertn.) fruits’, Beverage and Food World, 32, 50–52. Singh V., Singh H. K. and Singh I. S. (2004), ‘Evaluation of aonla varieties (Emblica officinalis Gaertn.) for fruit processing’, Haryana Journal of Horticulture Science, 33, 1–2, 18–20.

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Sumbali G. and Badyal K. (1990), ‘New records of fungal species associated with fruit rot of Phyllanthus emblica Linn’, Indian Journal of Mycology and Plant Pathology, 20, 22, 202–203. Tandon D. K., Dikshit A. and Kumar S. (2005), ‘Development of churan from dried aonla powder’, Beverage and Food World, 32, 53–54. Tandon D. K., Yadav R. C., Sood S., Kumar S. and Dikshit A. (2003), ‘Effect of blanching and lye peeling on the quality of aonla candy’, Indian Food Packer, 57, 147–149. Tandon R. N. and Srivastava M. P. (1964), ‘Fruit rot of aonla caused by Pestalotia cruenta Syd. in India’, Current Science, 33, 3, 86–87. Tandon R. N. and Verma A. (1964), ‘Some new storage diseases of fruits and vegetables’, Current Science, 33, 625–627. Taneja S., Parmar S. M. S., Williamson D. and Jain B. L. (1983), ‘Changes in phenol content of amla (Emblica officinalis) fruit after fungal infection’, Indian Journal of Mycology and Plant Pathology, 13, 1, 63–64. Thakur C. P. (1985), ‘Emblica officinalis reduces serum, arotic and hepatic cholesterol in rabbits’, Experientia, 41, 423–424. Thakur C. P., Thakur B., Sinha P. K. and Sinha S. K. (1988), ‘The Ayurvedic medicines, Haritaki, Amla and Bahera reduce cholesterol induced atherosclerosis in rabbits’, Indian Journal of Cardiology, 21, 167–172. Tripathi S. N., Tiwari C. M., Upadhyay B. N. and Singh R. S. (1979), ‘Screening of hypoglycemic action in certain indigenous drugs’, Journal of Research in Indian Medicine Yoga and Homoepathy, 14, 159. Tripathi V. K., Singh M. B. and Singh S. (1988), ‘Studies on comparative compositional changes in different preserved products of aonla var. Banarasi’, Indian Food Packer, 42, 60–66. Tyagi R. N. S. (1967), ‘Morphological and taxonomical studies on the genus Revenelia Berk occurring in Rajasthan’, PhD Thesis, University of Rajasthan, Udaipur, India. Yadav S. K. (1987), ‘Protection against radiation induced chromosome damage by Emblica officinalis fruit extract’, Caryologia, 49, 261–265. Yadav V. K. and Singh H. K. (1999), ‘Studies on the preharvest application of chemicals on shelf life of aonla (Emblica officinalis Gaertn.) fruits at ambient temperature’, Journal of Applied Horticulture, 1, 2, 118–121. Zhang C. F. and Qi P. K. (1996), ‘Identification of fungal diseases of amla (Phyllanthus emblica L.)’, Journal of South China Agriculture University, 17, 4, 6–10.

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6 Arazá (Eugenia stipitata McVaugh) J. P. Fernández-Trujillo, Technical University of Cartagena, Spain, M.S. Hernández, M. Carrillo and J. Barrera, Amazonian Institute of Scientific Research Sinchi, Colombia

Abstract: Arazá is an Amazonic fruit from the Myrtaceae family with a sigmoidal growth and a shelf life of less than four days at 20°C. The acidic pulp contains high levels of vitamin C, provitamin A, proteins and malic acid, and has a very pleasant aroma. The fruit is usually harvested in its mature-green stage of maturity, using skin colour, titratable acidity and fruit firmness as harvest indices. The fruit is very susceptible to mechanical damage, dehydration and shrivelling, anthracnose rot, softening and chilling injury at temperatures below 12°C. Postharvest treatments such as modified atmosphere packaging, intermittent warming, 1-methylcyclopropene and hot water dips, and use of adequate packaging may extend its shelf life up to two weeks at 12°C. The fruit is used fresh and processed (juices, frozen pulps, jams, sweets). This chapter describes basic recommendations for postharvest handling and maintaining quality, and suggests future research directions. Key words: Eugenia stipitata, postharvest, climacteric fruit, vitamin C, shrivelling.

6.1

Introduction

6.1.1 Origin, botany, morphology and structure Arazá (Eugenia stipitata McVaugh) is a perennial tree of the Myrtaceae family, Eugenia genus. Two subspecies were described by McVaugh (1956): stipitata from Brazil and Peru (also known as araçá-boi in Brazil or as pichi in Peru, the wild one), and sororia from Peru (also called rupina caspi, the domesticated subspecies). One landrace occurs in the Western Amazon (Gentil and Clement, 1997). The arazá fruit is a fleshy berry with a fine, yellow, pubescent epicarp, and attractive flavor (Galvis and Hernández, 1993a). Fruit shape is different in both subspecies of arazá: round to oblate in sp. stipitata and ovoid in sp. sororia. With regard to the arazá fruit’s structure, the parenchyma is the predominant tissue, with rounded cells and a well-defined thin cell wall. A cross-section of

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mature arazá fruit shows that cell growth stops in the last phase (S3), when the cell walls become thinner and deteriorate, while the seeds reach their definitive size and the fleshy mesocarp shows thin-walled cells. By the end of S3, the intercellular spaces are enlarged, while the cell wall becomes weaker as a result of hydrolysis, and the secretory channels have deteriorated. The pericarp of the mature arazá fruit includes the epidermis, a single external layer with thin-walled cells that divide anticlinally. The hypodermis, with small meristematic cells, lies below the epidermis. Secretor channels originate from the hypodermis. Several layers of parenchymatic cells form the mesocarp tissue. The pericarp increases at the beginning of fruit development as a result of cell division and later by cell expansion (Hernández et al., 2007b). 6.1.2 Worldwide importance Arazá is grown in countries of the Western Amazon basin (Peru, Brazil, Colombia, Bolivia, and Ecuador) and also in Costa Rica. Arazá seeds have been distributed to grow trees for ornamental purposes (e.g. Florida, Brazil). The main harvest season is February to May for the subspecies stipitata in Belém, Brazil (Morton, 1987). Two and sometimes up to four production seasons exist in Colombia’s Northern Amazon owing to the short period of growth between fruit set and harvesting (around 84 days in San José de Guaviare, Colombia) (Galvis and Hernández, 1993a). The production is year-round in the southern Amazon (Hernández and Fernández-Trujillo, 2004). As a tropical fruit, its potential economic value is very high. However, currently any economic value is limited to the countries of origin because the fruit is rarely exported. In Colombia, it is considered to belong to the second group of tropical fruits with export potential. The fruit is not usually edible as fresh, but is used after processing. The frozen pulp in different formats is offered for export to North America and Europe particularly from Costa Rica and Colombia, since Brazil consumes most of its own production. 6.1.3 Culinary uses, nutritional value and health benefits Arazá is marketed fresh, but is usually consumed as a strong or weak juice or in fruit or juice cocktails. It is also used in nectars, jellies (‘ates’ or ‘bocadillos’ in Spanish), jams and preserves. Arazá flavoring is commonly used to flavor sweets, ice creams, sorbets, yogurts (including organic yogurt), yogurt shakes with up to 35% arazá pulp, and other beverages (milkdrink, acidmilkdrink, fitdrink, powerdrink, wheydrink, refreshments), syrup, or to produce pulp-based foods such as ‘aragurt’. A jelly can be made from the pulp and seed, but excessive cooking partially destroys its attractive flavor. Fruit composition reports in the literature are based on a dry or a fresh weight basis, depends on the subspecies considered (Table 6.1), and mainly consists of 8 to 10.75% proteins, 5 to 6.5% fiber, 69 to 72% other carbohydrates, 0.16 to 0.21 calcium, some phosphorus, potassium and magnesium and 10 to 12 mg·kg−1 of

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Postharvest biology and technology of tropical and subtropical fruits Table 6.1 Composition of fully mature arazá fruit in percentage of fresh weight Subspecies Component

Sp. stipitata

Sp. sororia

E. stipitata (dry matter basis)

Humidity Protein Carbohydrates Fats Ash Fibers Ascorbic acid (mg)

90 1 7 0.3 1.1 0.6 7.7

91.5 1.0 5.5 1.1 ND 0.9 30.3

– 11 48 ND 4 37 300

Sources: Gentil and Clement (1997); Hernández et al. (2009); Rogez et al., (2004.) Note: ND = not determined.

zinc (ICRAF, 2009). Total dietary fiber is around 39% dry matter (Rogez et al., 2004). The starch content is significant, even in ripe fruit (0.63%; Filgueiras et al., 2002). In 100 g of fruit there is approximately 7.75 mg of vitamin A, 9.84 mg of vitamin B1 and 7.68 mg of vitamin C (doubling the orange juice levels) (Rogez et al., 2004). The surprisingly high protein content presumably results from the inclusion of the seeds (ICRAF, 2009). The predominant organic acid in arazá fruit is malic acid (250 μmol·g−1; Fig. 6.1a), while succinic and citric acids are low (below 50 μmol·g−1 at S3 stage) (Hernández et al., 2007b). The concentration of soluble sugars (glucose, fructose and sucrose) is low (Table 6.1; Fig. 6.1b). Total phenolics in mature fruit reach 64 mg.100−1 g fresh pulp of gallic acid (Vargas et al., 2005). Total pectic substance content in yellow fruit (0.4%) is not very high, and one-fifth of the total pectic material is water-soluble, while the high-methoxyl fraction is quite small but still predominant in the alcohol insoluble solids fraction. The native activity of the pectic enzymes (pectinmethylesterase and polygalacturonase) is relatively low (Filgueiras et al., 2002). Essential amino acids content is close to the needs of preschool children and is an ideal proportion for adults, in the case of valine, leucine, isoleucine, threonine, methionine, lysine, histidine and arginine. Of the amino acids, glutamic acid and glutamine followed by asparagine/aspartic acid show the highest concentration (Rogez et al., 2004). The bioactive compounds in arazá could have potential human health benefits owing to the potential antioxidant and free radical scavenging properties (Duke, 2009). Although local folk medicine recommends arazá for bowel and bladder treatments and for alleviating colds, no research has been done to contrast these treatments on a rational scientific basis. The most abundant aroma compounds in arazá fruit are sesquiterpenes with 38% germacrene D followed by 10.4% α-pinene and 15.2% β-pinene, and others

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Fig. 6.1 Changes in arazá fruit during ripening and postharvest storage at 20°C and 12°C: (a) Titratable acidity (♦); Malic acid (Δ) Hue angle or h* in sexagesimal degrees, (◊); (b) Weight loss (percentage on a fresh weight basis at harvest), (●); Firmness; (N, …); Ascorbic acid (μmol/g fresh weight), {); Fructose content (μmol/g fresh weight ▲). Levels at harvest were flesh firmness of 34.6 N, 26 μmol/g ascorbic acid and 1.2 μmol/g fructose; (c) Respiration rate (RR) in nmol·kg−1·seg−1 of CO2 of mature green arazá fruit during ripening at 20°C (♦) or 12°C (■) and 85% relative humidity; (d) Ethylene production (EP) expressed in μL·kg−1·h−1 of C2H4 and the same storage conditions than RR.

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at concentrations below 2.5% of the total headspace area counts. Traces or low relative total headspace percentages have been reported for another thirty aromatic compounds, while several remain unidentified. Esters are present at relatively low concentrations (Franco and Shibamoto, 2000).

6.2

Fruit development and postharvest physiology

6.2.1 Fruit growth, development and maturation Fruit development follows a simple sigmoid curve with three phases of fruit growth: an initial phase of cellular division, followed by an exponential growth phase of cellular elongation, and finally the ripening phase (Hernández et al., 2007b). Sigmoidal models of fruit growth have been developed for fruit weight (on a fresh and dry matter basis) and equatorial and longitudinal diameter (Hernández et al., 2007b). 6.2.2 Respiration, ethylene production and ripening Arazá fruit shows a climacteric pattern during its fast ripening, accompanied by peak of ethylene production (Galvis and Hernández, 1993b; Hernández et al., 2007b and 2009). Before the initiation of the climacteric, respiration rates are around 50 mg ·kg−1·h−1 of CO2, while the upsurge of respiration during the climacteric period reaches a peak of around 200 mg·kg−1·h−1 of CO2 (Fig. 6.1c). Ethylene production peak matches the climacteric CO2 peak during arazá ripening; the levels in mature fruit reaching 20 μL·kg−1·h−1 of C2H4 (Fig. 6.1d). Ripening changes include a pronounced change in skin color from green to yellow, softening, and the development of a pleasant aroma; an increase in polygalacturonase activity, soluble pectin and high-methoxyl alcohol insoluble pectin; a decrease in organic acid concentration (including ascorbic acid) and lowmethoxyl alcohol insoluble pectin, accompanied by a decrease in titratable acidity and total and free and bound phenolics (Figs. 1A and 1B; Filgueiras et al., 2002; Vargas et al., 2005). For example, ascorbic acid may decrease by 25% during one to two weeks of storage at optimum temperatures (12°C) and particularly after transfer to ambient marketing conditions. Fruit skin is hairless and attains maximum antioxidant activity when fully mature (Filgueiras et al., 2002; Vargas et al., 2005). Differences between subspecies are not well studied, but the subspecies sororia presents a pleasant acid taste and higher total soluble solids (6.2°Brix and 231 mM of H+ of titratable acidity) when it is mature compared with the subspecies stipitata (3.8°Brix and 296 mM of H+ of titratable acidity).

6.3

Maturity and quality components and indices

Arazá longitudinal and equatorial size is around 70 mm, and average fruit weight is 150 to 200 g (Donadio and Moro, 2002; Hernández et al., 2009; Tai-Chun and

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Álvarez, 1995). In the wild, fruit berry weight can vary from 30 to 800 g (Gentil and Clement, 1997). In Colombia, skin accounts for around 8% of the total weight, seeds 23% and pulp 69%, with an average of thirteen seeds per fruit (Hernández et al., 2007b). In Jaboticabal SP (Brazil), an area where arazá has been tried for ornamental purposes, Donadio and Moro (2002) reported a total weight of 153 g with around 33% skin, 18% seeds and 49% pulp. This result indicates that small and less juicy fruit may be an indicator of less adapted trees and poorer fruit quality. Skin color can be evaluated to classify the fruit maturity using a visual scale of 1 to 6 degrees (Plate IX: see colour section between pages 244 and 245) that matches lightness, chroma and hue skin color indices (L*, C*, h*), as defined by Hernández et al. (2009) and shown in Fig. 6.1a and Plate IX (see colour section). Class 1 is mature green, with the entire surface being dark green, L* = 52 to 54 units, C* = 32 to 37 units, h* = 106 to 108° (but fruit still capable of ripening; Plate Xa: see colour section). Class 2 is a breaker with 85% green and 15% pale yellow, and L* = 54 to 57 units, C* = 38 to 41 units, h* = 101 to 105°. The rest of the classes show more than 50% yellow skin. Class 3, is a half-yellow (turning) fruit with 50% yellow and L* = 58 to 60 units, C* = 42 to 44 units, h* = 95 to 99°. Class 4 corresponds to yellow, with 75% yellow color with L* = 61 to 64 units, C* = 45 to 48 units, h* = 89 to 94°. Class 5 is fully mature, with 100% yellow color (the optimum color for fresh consumption, Plate Xb: see colour section) with L* = 65 to 67 units, C* = 49 to 54 units, and h* = 83 to 88°. Finally, Class 6 is overripe fruit, with dark to yellow skin with L* = 68 to 71 units, C* = 55 to 59 units, h* = 80 to 84°. Harvest indices used in Colombia include a skin color hue value (h*) of around 110 ± 2° (corresponding to the dull green stage), a flesh firmness of around 30 N (Newton) and titratable acidity (TA) value above 300 mmol L−1 of H+. A level of 1 in maturity index (obtained by dividing total soluble solids between titratable acidity expressed in percentage of malic acid) has also been suggested as harvest index (Hernández et al., 2009). Depending on the stage of maturity at harvest, the pulp has a low soluble solids content (3.4 to 6.2°Brix), and pH is around 2.6 to 3.4 units, while titratable acidity is close to 3% malic acid (Fig. 6.1a). Dry matter increases during fruit growth, reaching levels of around 17% w/w in mature fruit (Hernández et al., 2009). Over-mature fruit (Plate Xc: see colour section) is prone to suffer fermentation, although its high pulp acidity limits microorganisms proliferation.

6.4

Preharvest factors affecting fruit quality

Fruit composition of arazá fruit given in the literature varies, particularly as regards the ascorbic acid content, probably due to differences in methodology used (extraction and analysis) and also to the stage of fruit maturity, subspecies, origin and natural genotypic and genotypic x environment variations. Arazá also shows differences in its nutrient content depending on the individual tree tested, particularly in thiamine, riboflavin, calcium, sodium, potassium and magnesium,

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and, to a lesser extent, total protein content, fat, fiber, iron, phosphorus and ascorbic acid. Soil quality and mineral availability are important factors in the nutrient value of arazá (Barrantes et al., 2002), and therefore influencing fruit size and composition. Climactic conditions are critical for arazá trees and for the production of good quality fruit. External aspects of the fruit and its susceptibility to preharvest disorders and diseases are particularly affected. The main meteorological factor affecting arazá production is precipitation. Relative humidity and temperature have secondary impacts on the flowering and fruiting. If these factors are constant and annual rainfall ranges between 200 and 300 mm·month−1, the shrub produces heavy and colored fruits (Aguiar, 1983). Otherwise the fruit is prone to attack by fruit flies and anthracnose during growth. Donadio and Moro (2004) mention the poor adaptation of arazá trees in Brazil outside Amazonic areas and describe severe fungal infection. The susceptibility of fruit to mechanical damage is also evident during preharvest (bruises and fruit deformation; Plate Xd: see colour section between pages 244 and 245). Fruits without adequate shade are susceptible to sunscald. Fruit production increases when plants reach their mature stage (age six to eight years) but also in the months with more rainfall or when plants are shaded by trees such as Cordia alliodora (van Kanten and Beer, 2005) or Hevea brasiliensis. However, the shade intensity must not be too great: arazá fruit has greater fruit sizes under lower shade intensity, and the production of fruit increases (van Kanten and Beer, 2005). In Colombia, Barrera et al. (2009a and 2009b) recommends 82% of interception of radiation brightness for achieving the best production. Therefore, agroforestry seems to be a great option due to the shade requirements of this shrub. Such trees also supply nutrients to small arazá trees, protecting them against severe climactic changes (temperatures, rain and winds), and surrounding the fruit with a high relative humidity (above 80%) and adequate temperatures for ripening (Barrera et al., 2009a).

6.5

Postharvest handling factors affecting quality

6.5.1 Temperature management At harvest, temperatures in the areas of production usually range from 18 to 33°C. To keep arazá fruit cool after harvest, it should be kept as much as possible in the shade and transported overnight from the areas of production to its final destination, since the availability of precooling technologies in the production areas is scant. 6.5.2 Physical damage Mechanical damage at harvest or during postharvest is the most critical problem for maintaining arazá fruit quality. The high susceptibly to arazá to such damage (with 50 to 80% total postharvest losses) is associated with fast softening, the absence of support tissue (collenchyma or sclerenchyma) and perhaps low fruit dry matter content (Hernández et al., 2007b; Rogez et al., 2004). Damage is caused by bruising (Plate Xe: see colour section) and impact during harvest and

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postharvest, compression due to excessive fruit load in the plastic boxes (no more than three levels are advisable), and vibration during transportation. Internally in the fruit, mechanical damage is manifested as light to dark brown spots below the fruit skin with some degree of skin translucency, which may appear after few hours to one day after harvesting (Plate Xc and Xe: see colour section between pages 244 and 245). 6.5.3 Water loss The second critical problem of arazá is weight loss, particularly in fruit stored above 18°C at low relative humidity, reaching up to 20% w/w at the highest ripening temperatures in less than one week (Fig. 6.1b). 6.5.4 Atmosphere Ethylene treatments have not been developed for arazá fruit, but accelerated degreening seems to be feasible due to the fast ripening changes of arazá fruit. Carbon dioxide tolerance has not been systematically studied but levels below 6 to 10% seem advisable, with oxygen ranging from 10 to 20.9%, but not for more than 10 to 15 days at temperatures around 10°C (Gallego et al., 2002; 2003).

6.6

Physiological disorders

The main physiological disorders of arazá fruit are chilling injury (scald, pitting, uneven ripeness, re-hardening and excessive acidity), uneven ripeness due to calcium chloride dips, shriveling and senescence off-flavors in over-mature fruit (Plate Xc, and Xe to Xj: see colour section). 6.6.1 Chilling injury Arazá is very sensitive to chilling injury (CI) at temperatures below 12°C with different degrees of skin scald, followed by pitting (Plate Xf: see colour section), depending on storage duration, as seen from experiments conducted in a temperature range of 6 to 11°C. CI symptoms are more severe in less mature than in mature fruit, particularly uneven ripening (Plate Xg: see colour section). CI symptoms are exacerbated when transferring the fruit to additional shelf-life periods at temperatures above 12°C. Abnormal or uneven ripening in arazá is frequently associated with abnormally high fruit acidity and re-hardening (Hernández et al., 2009). CI symptoms are frequently colonized in a few days by anthracnose rot caused by Colletrotrichum gloeosporiodes (Penz.) Penz. & Sacc. (teleomorph: Glomerella cingulata). 6.6.2 Other physiological disorders Arazá fruit is susceptible to concentrated calcium chloride dips (0.36 M or above) with symptoms of uneven ripening in patches and skin injuries that are not alleviated by low-temperature dips (Hernández et al., 2003b; Plate Xh: see colour section).

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Arazá is also susceptible to shriveling (Plate Xe and Xi: see colour section between pages 244 and 245) owing to its high susceptibility to dehydration. Senescence symptoms in over-mature fruit include lack of acidity, flesh firmness below 10 N, and off-flavors concomitant with a dramatic increase in fruit decay.

6.7

Pathological disorders

The main postharvest disease in arazá is the above-mentioned anthracnose in wounds or in chilling-injured areas (scalded areas; Plate Xj: see colour section). Gloesporium album and Monilia sp. have been isolated from decayed fruit (Ferreira and Gentil, 1999; Hernández et al., 2009). The fungi have also been identified in the seeds (Torres et al., 2008). A fungicide treatment with Sportak 45% active ingredient (a.i.) plus prochloraz at 0.24 mL a.i. L−1, blotting and drying in air flow at 12°C has occasionally been used to control anthracnose (Gallego et al., 2003). However, postharvest fungicides are rarely used due to the trend towards organic certification in arazá production. Refrigeration (10°C) plus modified atmosphere packaging usually prevents anthracnose development with or without pre-conditioning the fruit (Gallego et al., 2002). Control of anthracnose with hot water dips alone has been found unsatisfactory (Hernández et al., 2002). Cylindrocladium scoparium rot is characterized initially by small light brown lesions, which evolve to severe damaged areas that can reach about 0.3 cm of pulp depth (Nuñes et al., 1995). During postharvest handling fruits are usually washed with hypochlorite (200 mg·L−1) but rots are only partially controlled and no treatment to control rot has been established. The pathogenicity of Curvularia sp. (Wakk.) Boedijn may be important. This thick-walled pigmented fungus is considered necrotrophic and its development could be a problem because it requires longer postharvest treatments than thinwalled species to reduce germination (Buck et al., 2002). For example, 21% of fruit stored for two weeks at 12°C, followed by a shelf-life period of three days at 20°C, suffered from this rot. Symptoms of Curvularia spp. include fruit softness and pink spot areas in the pulp with fermentative degradation and lack of juice (Hernández and Fernández-Trujillo, 2004; Hernández et al., 2009). Fruits stored at lower temperatures showed half the incidence of this rot (Hernández et al., 2009). Its causes have not been completely verified. The incidence of rust (Puccinia psidii or Uromyces sp.) has been recorded in Manaus and Costa Rica (Moraes et al., 1994; Tai Chun and Álvarez, 1995). Fruit selection and elimination of decayed fruits are the main preventive measurements against this disease and others. Yeasts are a minor problem but can affect fruit bruises and/or chemical-scalded areas caused by treatments with calcium chloride dips of 0.36 or 0.72 M (4 or 8% w/v) (Hernández et al., 2003b; 2007b). In the testa of arazá seeds another sixteen fungi genera have been identified, two of them with sterile mycelium. This might have a negative impact on latent fruit infections. Five of the previous genera (Colletotrichum sp, Fusarium sp,

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Curvularia sp, Pestalotia sp and Cladosporium sp) are opportunistic and another five are opportunistic pathogens (Aspergillus sp, Penicillium sp, Rhizopus sp, Myrothecium sp and Helmintosporium sp). Geotrichum sp., Thielaviopsis sp. and Rhizoctonia sp., well-known phytopathogens that affect the fruit of several species (Torres et al., 2008), have been identified in the seeds but not in arazá fruit. Neither biological control of fungal rot nor combined treatments with hot water pretreatments have been applied to arazá fruit.

6.8

Insect pests and their control

The main arazá pests are fruit flies, such as Anastrepha obliqua and A. striata (diptera: tephritidae) (Saldanha and Silva, 1999), and the coleoptera Conotrachelus eugeniae and Atractomerus immigrans on rinds. Neosilba zadolicha (diptera: lonchaeidae) larvae are seldom present in fruit blemishes caused by these insects (Couturier et al., 1996). The Mediterranean fruit fly (Ceratitis capitata Wied) has been identified in Costa Rican orchards (Moraes et al., 1994; Tai Chun and Álvarez, 1995). In the field, plastic McPhail traps baited with attractants are used to capture these flies. Infested fruit must be collected and buried at least 50 cm deep in the ground (Villachica et al., 1996). The black bee (Trigona branneri Cockerell), a bee without a sting, feeds on the skin, pulp and sometimes the seed of the fruit, causes severe fruit damage if the bee population is large (Villachica et al., 1996). There are no quarantine procedures against tropical flies for this fruit, but recommendations to avoid spread of pests from one plantation to another, and integrated protocol management during the pre- and postharvest phase are necessary (Couturier et al., 1994; 1996). Cold quarantine treatments cannot be indiscriminately used because of CI. Pre- or postharvest biological control is not well established and has not even been widely studied yet for arazá.

6.9

Postharvest handling practices

6.9.1 Harvest operations Fruit are carefully harvested during the morning, packed in polyethylene boxes and transported to a packinghouse (Carrillo et al., 2009). 6.9.2 Packinghouse practices Fruit are usually selected manually in the field on polished on flat tables covered by washable materials in order to remove small or rotten fruit and others with sunburn or mechanical or insect damages. Fruit can be graded according to the degree of maturity based on skin color (Plate IX: see colour section between pages 244 and 245). Only grades 2 to 3 are usually marketable, while more advanced stages of maturity are sent to local markets and/or immediate processing. Mature green fruit

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are the best for long-distance markets (Plate Xa: see colour section between pages 244 and 245). Fruit are packed in reusable polyethylene boxes or boxes made of soft wood. An alternative is to pack the fruit in pouches (a net made of flexible low density polyethylene foam or ‘mallalon’) to reduce mechanical damage before packing in cardboard or plastic boxes (Carrillo et al., 2009). However, traditional cardboard packaging is not recyclable, so that new recyclable cardboard packaging has been designed in Colombia to allow fruit ventilation and the packing of 8.5 kg fruit dividing the cardboard box into three compartments (Carrillo et al., 2009). The packed fruit is kept in the shade and transported overnight (six to eight hours). Additional postharvest handling treatments involve washing fruit in tap water for 3 min to remove dust and other residuals, sanitizing with 80 to 100 mg·L−1 sodium hypochlorite for 5 min, and finally rinsing in tap water to remove residues of the treatment before allowing to dry in air. Such fruit are less susceptible to rot during ripening in the recommended storage conditions (12 to 13°C and 95% relative humidity; Peña et al., 2007). Arazá fruit is not subjected to waxing. Experimental edible coatings of yuca or cassava (Manihot esculenta Crantz) starch have been tested. This coating is prepared by dissolving yuca starch (2% w/v) for 15 min at 78°C until jellification. Glycerol (2%) is added as the plasticizer and the gel is stirred for 10 min. Fruit are dipped in this mixture for 1 min at 15°C and then let to dry for 3 h. Starch coatings do not contain emulsifiers or lipids because of possible deterioration of the film properties. The coating delays ripening changes, such as the climacteric peak and color changes from green to yellow; also, respiration rates and ethylene production are reduced, but coating does not affect other internal quality traits (Jiménez et al., 2008). 6.9.3 Control of ripening and senescence The short shelf life of arazá fruit (three to four days at 25°C or above) is due to a high respiration rate (RR), high levels of ethylene production (EP), accompanied by severe dehydration, shriveling, softening and susceptibility to mechanical damage, anthracnose decay, and also due to CI at temperatures below 11 to 12°C. Hot-water dips (5 min at 50°C; HWD) can accelerate arazá ripening during subsequent storage at 12°C: At this treatment predominant acids are consumed, which is an advantage during the marketing of this acidic fruit. A solution of calcium chloride in HWD increases calcium absorption by the fruit and contributes to the delay of some ripening changes. Calcium chloride dips alone (i.e. 0.36 M at 4°C), delay ripening changes during subsequent ripening at 12°C because of the better retention of sugars (mainly sucrose and fructose) and organic acids (malate and succinate). However, anthracnose, and to a lesser extent, other signs of decay can be exacerbated by this treatment. Low-temperature calcium chloride dips far below 0.36 M could be a promising treatment for retaining overall internal fruit quality and modulating calcium absorption by the fruit (Hernández et al., 2003b). 1-methylcyclopropene (1-MCP) has been used at laboratory and semicommercial scale in arazá (Carrillo et al., 2011; Hernández et al., 2007b). 1-MCP

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is even effective for treating the fruit at tropical temperatures (27°C) for 1 h. Recommendations for maintaining postharvest quality are harvesting at the mature-green stage, treatment with 1 μL L−1 of 1-MCP for 1 h, and storage at 12°C for up to two weeks. This treatment prolongs arazá postharvest life by about one week by delaying or reducing the respiration and ethylene production rates, skin color changes, the loss of organic acids, and softening. Also, 1-MCP can have an important effect by reducing rots and weight losses. At 7°C, 1-MCP also reduces mature-green fruit weight loss and shriveling. Long 1-MCP treatment periods of 6 or 12 h at 20°C caused partial and uneven ripeness. Treating fruit in their post-climacteric stage of maturity had little effect on ripening compared with the mature-green stage. 1-MCP increases the respiration rate and/or the ethylene production in certain combinations of advanced harvest maturities and/or unfavorable storage temperatures. Ethylene treatments seem to be unnecessary because of the fast ripening of mature-green arazá fruit after harvest. 6.9.4 Recommended storage and shipping conditions The best storage temperature is 12°C for less than two weeks with 90 to 95% relative humidity because this avoids CI and reduces shriveling and rot development. Relative humidity levels below 85% would result in unacceptable weight losses and shriveling. A warming treatment of 18 h at 20°C with 90% relative humidity after six days at 10°C reduces skin scald and associated decay, and extends shelf life by up to two weeks (Hernández et al., 2003a). Respiration rates are very high during the postharvest phase at temperatures particularly above 12 to 13°C and carbon dioxide removal will prevent CO2 accumulation within the storerooms. Ethylene scrubbing is also advisable if the fruit is kept in contact with other fruits susceptible to ethylene. Information about controlled atmosphere storage in arazá is lacking, but modified atmosphere (MA) packaging or individual seal packaging has been used. For example passive modified atmosphere was generated within a selective low-density polyethylene (LDPE 38 μm, film permeability 4,000 cm3 m−2 d−1 to O2, 2,700 cm3 m−2d−1 to CO2, and 0.4 to 0.6 cm3 m−2 d−1 to water vapour) (Gallego et al., 2002; 2003). Carbon dioxide levels above 5% within the packages should be avoided. MA packaging of individual fruit has been tested. For example, the storage of arazá fruit under active MA conditions with the injection of 2% CO2 and 21% O2 preserves fruit quality for 2 weeks at 10°C. This treatment delays changes in color parameters (L*, C* and h*), and results in reduced incidence of anthracnose, scald and weight loss compared with control fruits and fruit packaged in macroperforated or the LDPE films reported before (Gallego et al., 2003; Hernández et al., 2007a). Compatibility for transportation is similar to that found in other climacteric and aromatic tropical fruit sensitive to CI. The fruit must be transported with other aromatic tropical fruit sensitive to ethylene and chilling injury (i.e. at temperatures of 12 to 13°C and preferably with good air renewal).

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Processing

6.10.1 Fresh-cut processing Arazá fruit has low potential for fresh-cut processing due to the presence of seeds and the very high acidity of the pulp. However, small chunks can be used in confectionery. 6.10.2 Other processing practices Arazá unit processing operations to obtain pulp have been reported by Hernández and Barrera (2000; 2004). Fruits are rinsed with tap water (by sprinkling or immersion) to remove residues and the remains of tree branches and leaves. Fruits are then disinfected by immersion in a solution of 400 mg·L−1 thiabendazole for 5 min under continuous fruit movement. After that a second rinsing removes fungicide residues with pressurized tap water sprinklers. Then the fruit is allowed to dry before separating into maturity classes (Plate IX: see colour section between pages 244 and 245), removing fruit without the adequate quality attributes. Fully mature fruit (soluble solids/titratable acidity ratios of 1 to 3; Plate Xb: see colour section) are the best for pulp processing following the protocols reported by Hernández and Barrera (2000; 2004). Processing practices such as freezing, canning, drying or osmotic dehydration have been used to preserve arazá pulp and juices. Aseptic packaging could be used to improve pulp quality. Blanching arazá pulp for 7 min, fast freezing and slow thawing help to maintain textural properties, including liquid retention and ascorbic acid content, while changes in phenolic compounds, β-carotene and antioxidant activity are minimized (Millán et al., 2007). Traditional products include frozen pulp, traditional canning of the whole fruit, nectars, jams, fermented beverages in milk serum, wines, spiced or non-spiced sausages, jellies, candies and different kind of biscuits, sweets and desserts (Hernández et al., 2006; Carrillo et al., 2009; Rodríguez and Bastidas, 2009). Candies of different compositions are one of the best-known fruit pulp uses, and certain brands are very successful in the national market. The fruits have also been used to produce liquors (Andrade and Ribeiro, 1997) and perfumes. Arazá is lyophilized after adding 10% v/w of the dissacharide trehalose solutions (25°Brix) to fresh pulp, which results in reduced browning associated with the Maillard reaction and good flavor quality. The last innovation in commercial-scale pasteurized pulp is the use of flexible packaging. These packages are stored under refrigeration for up to 50 days with minimum additives (0.15 mg·kg−1 sodium benzoate and potassium sorbate, respectively) (Carrillo et al., 2009). Deacidification of clarified arazá juice by electrodialysis can be used to produce malic acid but reduces flavor without affecting overall sensory properties (Vera et al., 2007).

6.11

Conclusions

Challenges to maintain arazá’s fresh fruit quality in the future will be based on reducing the high total losses without compromising flavor and nutritional quality.

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The transport system is usually a limiting factor in the Amazon basin. New transportation systems should be developed and implemented, taking into account factors such as vibration and difficulties in adequate temperature management. This, in turn, is directly linked to energy supply guarantees at a reasonable economic and environmental cost. Adapting general harvest and postharvest recommendations to different growing areas is required, because such aspects as the effect of fruit subspecies behavior or fruit variability in postharvest conditions have not been addressed. It is necessary to establish a table of quality grades for the fruit, taking into account the variability that exists between subspecies. The first goal should be to develop alternative and sustainable fruit packages and a postharvest handling system to reduce mechanical damage during harvesting, handling and transportation. The second goal must be the development of quarantine procedures, particularly for mature-green fruit. A good start may be trials with metabolic stress disinfestation procedures. This procedure is based on physical manipulation, generating cycles of expansion and compression forces, which are combined with low vapor concentrations of natural disinfecting chemicals to disinfect and disinfest simultaneously and rapidly fresh agricultural products (Lagunas-Solar et al., 2006). The third goal must be the development of sustainable coatings to keep weight loss below reasonable levels in tropical temperatures without fermentation. Finding alternatives to sodium hypochlorite is also desirable. The fourth goal should be to establish postharvest protocols combining the removal of rotten fruit, the careful selection of defect-free fruit according to the stage of maturity, precooling, temperature control and treatments with ripening inhibitors and other coadjutants in order to offer local consumers good produce and reinforce local markets. The development of new cultivars with a reduced number of seeds or parthenocarpic fruit may open up new possibilities for fresh-cut processing (particularly as cubes or slices). The development of molecular markers based on simple sequence repeat (SSR) loci in arazá (Zapata-Ortiz et al., 2009) will boost gene expression studies in the future. Studies of postharvest behavior parallel to breeding as well as germplasm and biodiversity maintenance are required, because different ecotypes in the arazá subspecies have been identified. New postharvest treatments must be developed, and others, such as heat treatments in combination, should be reevaluated. For example, gradual cooling combined with MA packaging using a suitable polymeric film and adequate storage conditions could avoid physiological disorders in arazá fruit. The variability of some nutrients in arazá points out to interesting field that will benefit from proper crop management and nutritional quality-oriented arazá breeding for postharvest purposes. Cultivars with a lower susceptibility to postharvest disorders and diseases and higher resistance to postharvest handling without sacrificing flavor are required. Agroforesty associations can be developed to provide shade in order to improve fruit quality and size. Socioeconomic and environmental issues must be carefully addressed, too. The marketing of the fruit is strongly based on sustainable management of the

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crop, and care for the Amazon Basin and its population. It is used to promote business for local or international companies exporting fresh or processed tropical Amazonian fruit. However, arazá is now grown in areas outside the Amazon Basin, in Colombia for example. In summary, arazá is a very perishable fruit, very sensitive to mechanical damage, CI and shriveling. The fruit has serious constraints for marketing at local or international level without the maintenance of the cold chain alone or combined with other postharvest treatments, such as MA packaging, ethylene inhibitors and good handling practices and packaging. In the absence of such measures and a market for fresh fruit, more than 70% of the production must be processed in producing areas and new products and by-products should be scaled to industrial level, taking into account possible loss of ascorbic acid and labile nutrients. Different food processing technologies could be used to improve pulp quality and added value to the derived products.

6.12

References

Aguiar J. P. L. (1983), ‘Araçá-boi (Eugenia stipitata, McVaugh): aspectos e dados preliminares sobre a sua composição química’, Acta Amazonica, 13, 953–954. Andrade J. S., Ribeiro F., (1997), ‘Adequação tecnológica de frutos da Amazônia: licor de araçá-boi (Eugenia stipitata McVaugh)’, Acta Amazónica, 27(4), 273–278. Barrantes R., Yaya D. and Arias G. (2002), ‘Estudio químico bromatológico de diferentes individuos de Eugenia stipitata McVaugh (arazá)’, Ciencia e investigación, 5(1). Available from: http://sisbib.unmsm.edu.pe/BVRevistas/ciencia/v05_n1/estudio_ quimico.htm [accessed 5 December 2009]. Barrera J. A., Orjuela N., Melgarejo L. M. and Hernández M. S. (2009a), ‘Efecto de deficiencias minerales y de la luz en arazá (Eugenia stipitata) y copoazú’, Ministerio de Agricultura de Colombia e Instituto Amazónico de Investigaciones Científicas SINCHI. Bogotá DC, Colombia. Fortalecimiento de la cadena de frutales en la Amazonia suroccidental, ch. 1, 1–26. Barrera J. A., Orjuela N., Melgarejo L. M., Caidedo D. and Hernández M. S. (2009b), ‘Interacción planta-ambiente en modelos de producción con arazá (Eugenia stipitata McVaugh) y copoazú (Theobroma grandiflorum Will ex Spreng Schum)’, Ministerio de Agricultura de Colombia e Instituto Amazónico de Investigaciones Científicas SINCHI. Bogotá DC, Colombia. Fortalecimiento de la cadena de frutales en la Amazonia suroccidental, ch. 1, 1-27-53. Buck J. W., van Iersel M. W., Oetting R. D. and Hung Y. C. (2002), ‘In vitro fungicidal activity of acidic electrolyed oxidizing water’, Plant Dis, 20, 278–281. Carrillo M. P., Hernández M. S., Hernández C., Jiménez P., Cardona J., et al. (2009), ‘Calidad e innovación en la cadena de valor de frutales nativos, arazá y copoazú’, Ministerio de Agricultura de Colombia e Instituto Amazónico de Investigaciones Científicas SINCHI. Bogotá DC, Colombia. Fortalecimiento de la cadena de frutales en la Amazonia suroccidental, ch. 3, 55–76. Carrillo M. P., Hernández M. S., Barrera J. A., Martínez O. and Fernández-Trujillo J. P. (2011), ‘1-methylcyclopropene delays arazá ripening and improves postharvest fruit quality’, LWT-Food Sci Technol, 44, 250–255. Couturier G., Tanchiva E., Cárdenas R., González J., and Inga H. (1994), ‘Los insectos plaga del camu camu (Myrciaria dubia H.B.IC) y del arazá (Eugenia stipitata Mc Vaugh). Identificación y control’, Serie informe técnico no 25. INIA, Lima, Peru. Available from:

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http://horizon.documentation.ird.fr/exl-doc/pleins_textes/doc34-01/41354.pdf [accessed 30 December 2009]. Couturier G., Tanchiva E., Gonzales J., Cardenas R. and Inga H. (1996), ‘Preliminary observations on the insect pests of arazá (Eugenia stipitata McVaugh, Myrtaceae), a new fruit crop in Amazonia’, Fruits, 51, 229–239. Donadio L. C. and Moro F. V. (2004), ‘Potential of Brazilian Eugenia Myrtaceae as ornamental and as a fruit crop’, Acta Hort, 632, 65–68. Duke J. (2009). ‘Dr. Duke’s phytochemical and ethnobotanical databases (online database)’. Available from: http://sun.ars-grin.gov:8080/npgspub/xsql/duke/pl_act. xsql?taxon=1241 [accessed 14 December 2009]. Ferreira S. A. N. and Gentil D. F. O. (1999), ‘Arazá (Eugenia stipitata): cultivo y utilización. Technical Manual’, Tratado de Cooperación Amazónica and Instituto Naciorial de Pesquisas da Amazonia, Venezuela. Filgueiras H. A. C., Alves R. E., Moura C. F. H., Araújo N. C. C. and Almeida A. S. (2002), ‘Quality of fruits native to Latin America for processing: arazá (Eugenia stipitata McVaugh)’, Acta Hort, 575, 543–547. Franco M. R. B. and Shibamoto T. (2000), ‘Volatile composition of some Brazilian fruits: Umbu-caja (Spondias citherea), camu-camu (Myrciaria dubia), arapa-boi (Eugenia stipitata), and cupuacu (Theobroma grandiflorum)’, J Agric Food Chem, 48, 263–1,265. Gallego L., Hernández M. S. and Fernández-Trujillo J. P. (2002), ‘Evolución de la calidad del fruto del arazá (Eugenia stipitata McVaugh) bajo atmósfera modificada’, in López A., Esnoz A., Artés F., Avances en Técnicas y Ciencias del Frío 1, Cartagena (Murcia, Spain), 517–523. Gallego L., Hernández M. S., Fernández-Trujillo J. P., Martínez O. and Quicazán M. (2003), ‘Color development of arazá fruit as related to modified atmosphere packaging’, Acta Hort, 628, 343–350. Galvis J. A. and Hernández M. S. (1993a), ‘Análisis del crecimiento del fruto y determinación del momento de cosecha del arazá’, Colombia Amazónica, 6, 107–121. Galvis J. A. and Hernández M. S. (1993b), ‘Comportamiento fisiológico del arazá (Eugenia stipitata) bajo diferentes temperaturas de almacenamiento’, Colombia Amazónica, 6, 123–134. Gentil D. F. O. and Clement C. R. (1997), ‘The arazá (Eugenia stipitata): results and research directions’, Acta Hort, 452, 9–17. Hernández M. S., Arjona H. E., Martínez O. and Fernández-Trujillo J. P. (2003a), ‘Influence of intermittent warming treatments on the postharvest quality of arazá fruit (Eugenia stipitata Mc Vaugh)’, in Dris R. and Sharma A., Food Technology and Quality Evaluation. Science Publishers Inc., Enfield (NH, USA) and Plymouth (UK), vol. 4, ch. 43, 261–265. Hernández M. S. and Barrera J. A. (2000), ‘Manejo postcosecha y transformación de frutales nativos promisorios en la Amazonia colombiana’, Edn Produmedios, Bogotá DC, Colombia. Hernández M. S. and Barrera J. A. (2004), ‘Aspectos biológicos de conservación de frutas promisorias de la amazonia colombiana’, Edn Guadalupe Ltda. Bogotá DC, Colombia. Available from: www.fao.org/inpho/content/documents/vlibrary/ad418s/ad418s00.pdf [accessed 4 January 2010]. Hernández M. S. and Fernández-Trujillo J. P. (2004), ‘Arazá fruit’, in Gross K. C., Saltveit M. E. and Wang C. Y., USDA Agricultural Handbook No. 66. USDA. USA. Available from: http://www.ba.ars.usda.gov/hb66/029araza.pdf [accessed 5 December 2009]. Hernández M. S., Barrera J., Bardales X. L. and Carrillo M. P. (2006), ‘Manejo y transformación de frutales nativos de la amazonia’, Colombia Amazónica, August (extra), 191–204. Hernández M. S., Barrera J., Fernández-Trujillo J. P., Carrillo M. P. and Bardales X. L. (2007a), ‘Manual de manejo de cosecha y postcosecha de frutos de arazá (Eugenia stipitata Mc Vaugh) en la Amazonia colombiana’. Instituto Amazónico de Investigaciones

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Científicas SINCHI. Bogotá DC, Colombia. Available from: http://www.corpoica.org.co/ SitioWeb/Archivos/Publicaciones/Arazmanejoyconservacion.pdf [accessed 5 December 2009]. Hernández M. S., Barrera J. A., Martínez O. and Fernández-Trujillo J. P. (2009), ‘Postharvest quality of arazá fruit during low temperature storage’, LWT – Food Sci Technol, 42, 879–884. Hernández M. S., Fernández-Trujillo J. P. and Martínez O. (2002), ‘Efecto del pretratamiento térmico con agua caliente en el almacenamiento de frutos de arazá (Eugenia stipitata McVaugh)’, in López A., Esnoz A. and Artés F, Avances en Técnicas y Ciencias del Frío 1, Cartagena (Murcia, Spain), 341–346. Hernández M. S., Fernández-Trujillo J. P. and Martínez O. (2003b), ‘Postharvest quality of arazá fruit (Eugenia stipitata Mc Vaugh) treated with calcium chloride solutions at two temperatures’, Acta Hort, 628, 653–660. Hernández M. S., Martínez O. and Fernández-Trujillo J. P. (2007b), ‘Behavior of arazá fruit quality traits during growth, development and ripening’, Scientia Hort, 111, 220–227. International Center of Agroforestry – ICRAF (2009), ‘Eugenia stipitata. Agroforestry tree database’. Available from: http://www.worldagroforestrycentre.org/sea/products/ afdbases/af/asp/SpeciesInfo.asp [accessed 23 May 2009]. Jiménez S. P., Hernández M. S., Carrillo M. P., Barrera J. A., Martínez O. and FernándezTrujillo J. P. (2008), ‘Puntos críticos en la fisiología y la conservación postcosecha de dos mirtáceas amazónicas (arazá y camu camu)’, in Oria R., Val J. and Ferrer A., Avances en maduración y post-recolección de frutas y hortalizas, Zaragoza (Spain), 410–417. Lagunas-Solar M. C., Essert T. K., Piña C., Zeng N. X. and Truong T. D. (2006), ‘Metabolic stress disinfection and disinfestation (MSDD): a new, non-thermal, residue-free process for fresh agricultural products’, J Sci Food Agric, 86, 1,814–1,825. McVaugh R. (1956), ‘Tropical American Myrtaceae’, Fieldiana Bot, 29, 145–228. Millán E., Restrepo L. P. and Narváez C. E. (2007),‘Efecto del escaldado, de la velocidad de congelación y de descongelación sobre la calidad de la pulpa congelada de arazá (Eugenia stipitata Mc Vaugh)’, Agronomía Colombiana, 25, 333–338. Moraes V. H. de F., Hans C., de Souza A. G. C. and Cohen I. (1994), ‘Native fruit species of economic potential from the Brazilian Amazon’, Angewandte Botanik, 68, 47–52. Morton J. L. (1987), ‘Guava related species’, in Morton J. L., Fruits of Warm Climates, Miami, FL, 366–368. Nuñes A. M. L., Stein R. L. B. and de Albuquerque F. C. (1995), ‘Araçá-boi (Eugenia stipitata): Um novo hospedeiro de Cylindrocladium scoparium’, Fitopatol Bras, 20, 488–490. Peña A. C., González M. L., Hernández M. S., Novoa C. and Fernández-Trujillo J. P. (2007), ‘Evaluación del comportamiento del fruto de arazá (Eugenia stipitata Mc Vaugh) en las operaciones de acondicionamiento húmedo’, Revista de la Sociedad Colombiana de Ciencias Hortícolas, 1(2), 182–188. Rodríguez S. and Bastidas P. (2009), ‘Evaluating the cooking process for obtaining hard candy from arazá (Eugenia stipitata) pulp. Revista Ingeniería e Investigación 29(2), 35–41. Rogez H., Buxant R., Mignolet E., Souza J., Silva E. and Larondelle Y. (2004), ‘Chemical composition of the pulp of three typical Amazonian fruits: araca-boi (Eugenia stipitata), bacurí (Platonia insignis) and cupuacu (Theobroma grandiflorum)’, Eur Food Res Technol, 218, 380–384. Saldanha L. A. and Silva N. M. (1999), ‘Semi-artificial bearing of the larvae of Anastrepha obliqua (Diptera:Tephritidae) in Manaus, Amazonas-Brazil’, Fl Entomol, 82, 82–87. Tai Chun P. A. and Álvarez M. (1995), ‘Pre and post harvest pests and diseases of arazá (Eugenia stipitata) in Costa Rica’, Biblioteca Orton IICA/CATIE. Costa Rica. Available from: http://books.google.es/books?id=mOwNAQAAIAAJ&lpg=PA18&ots=BwXfgQ JwWN&dq=araza%20fruit%20fungi&pg=PP1#v=onepage&q=&f=false [accessed 5 December 2009].

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Torres C., Correa N. D. and Díaz J. E. (2008), ‘Characterising fungal microorganisms in Amazon peach seeds (Eugenia stipitata)’, Orinoquia, 12(1), 31–44. Available from: http:// orinoquia.unillanos.edu.co/index.php?option=com_docman&task=doc_view&gid=123 [accessed 6 December 2009]. Van Kanten R. and Beer J. (2005), ‘Production and phenology of the fruit shrub Eugenia stipitata in agroforestry systems in Costa Rica’, Agroforestry Systems, 64, 203–209. Vargas A. M., Rivera C. A. P. and Narváez C. E. (2005), ‘Capacidad antioxidante durante la maduración del arazá (Eugenia stipitata McVaugh)’, Rev Col Quím, 34, 7–65. Vera E., Sandeaux J., Persin F., Pourcelly G., Dornier M., et al. (2007), ‘Deacidification of clarified tropical fruit juices by electrodialysis. Part II. Characteristics of the deacidified juices’, J Food Engin, 78, 1,439–1,445. Villachica H., Carvalho J. E. U., Müller C. H., Díaz C., Almanza M. (1996), ‘Frutales y hortalizas promisorios de la Amazonia’. Lima, Peru, Tratado de Cooperacion AmazonicaSecretaria Pro-tempore. Available from: http://www.otca.org.br/publicacao/SPT-TCAPER-44.pdf [accessed 30 December 2009]. Zapata-Ortíz J. A., Quintero L. and Barrera J. A. (2009), ‘Variabilidad genética de cultivos de arazá (Eugenia stipitata) y cocona (solanum sessiliflorum) presentes en los departamentos de Caquetá y Guaviare, Amazonia Colombiana mediante marcadores ISSR’, BSc thesis report. Sinchi Inst., Bogota, Colombia.

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7 Assyrian plum (Cordia myxa L.) T. Al-Ati, Kuwait Institute for Scientific Research, Kuwait

Abstract: Cordia myxa (which bears the Assyrian plum) is a common tree in certain Asian and African areas. The tree, leaves and fruit of Cordia myxa have important applications in different societies and the fruit is known for its medicinal uses. Very little research on Cordia myxa has been published, but the focus of most articles to date has been nutritional and toxicological analysis. This chapter reviews the many useful characteristics of this underutilized and understudied fruit, including its health-promoting properties. There is the need to explore possible uses for bioactive or functional components extracted from the fruit, which may find application in food processing or in new products. More studies are needed to advance understanding of the fruit’s postharvest quality attributes and characteristics and to develop useful postharvest technologies to help maintain quality and extend shelf life. This may not only encourage farmers to grow more Cordia myxa trees, but also would promote culinary uses and research into other applications. Increased production of this crop would help to enhance the nutritional status of many people, especially in Asia and Africa where the tree is cultivated, and at the same time introduce the fruit to new markets around the world. Key words: Cordia myxa, postharvest, medicinal uses, quality attributes, soluble acids, titratable acidity, firmness.

7.1

Introduction

7.1.1 Origin, botany, morphology and structure Cordia myxa L. is probably native to an area stretching from tropical Africa through to the Middle East. It is part of a genus of about 320 tropical species that belongs to Boraginaceae (Hound’s-Tongue) family. Its common name is the Assyrian plum and the fruit has the following plant classification (Weaver and Anderson, 2007): Kingdom: Subkingdom:

Plantae Tracheobionta (vascular plants)

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Assyrian plum (Cordia myxa L.) Superdivision: Division: Class: Subclass: Order: Family: Genus: Species:

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Spermatophyta (seed plants) Magnoliophyta (flowering plants) Magnoliopsida (dicotyledons) Asteridea Lamiales Boraginaceae (borage family) Cordia L. (cordial) Cordia myxa L. (Assyrian plum)

There are approximately 300 different species of trees and shrubs of the Cordia genus in the Boraginaceae family. The cordias are characterized by their extravagant, fragrant flowers, hairy leaves, and edible fruits. The name Cordia is derivative of the surname of sixteenth-century German botanist Valerius Cordus and the species name myxa comes from the Greek word for mucus. Common names of the fruit of Cordia myxa include Assyrian plum and sebesten. The tree is also known as the bird’s nest tree. Figures 7.1 to 7.4 and Plates XXI and XXII (see colour section between pages 244 and 245) show the different parts of the Cordia myxa tree. The tree, branches, leaves and fruits of Cordia myxa can be described thus (Oudhia, 2007): Cordia myxa is a

Fig. 7.1

Cordia myxa tree.

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Fig. 7.2

Cordia myxa leaves.

dioecious shrub or small tree that can be as high as 12 m, with either a tortuous or straight bole and grey, cracked bark (Fig. 7.1). The branchlets are hairy, though they later become glabrous with very prominent leaf scars. The leaves are characterized by alternate, simple, stipules with a petiole length of 0.45 to 0.5 cm. The shape of the leaf is variable, with a blade that can be broadly ovate or orbicular, a base that can be round, cordate or cuneate, an apex that can be either rounded or acuminate and margins that vary from entire to toothed (Fig. 7.2). The flowers of the Cordia myxa are unisex; they have a white or creamy coloring and a pedicel length of 1 to 2 mm (Fig. 7.3). The fruit, an either globular or ovoid drupe of 2 to 3.5 cm in length, is apiculate and enclosed at the base by the accrescent calyx (Plate XI: see colour section between pages 244 and 245). As shown in Fig. 7.4, the pulp of the fruit is transparent, mucilaginous and sweet in taste. In addition, the fruit is pale brown or pink in color, becoming darker as it ripens. Small chains of flowers appear in March/April (University of Arizona, 2009). A selection of 30 groups of Cordia myxa collected from 95 sites with different

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Assyrian plum (Cordia myxa L.)

Fig. 7.3

Fig. 7.4

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Cordia myxa flowers.

Cross-section of Cordia myxa fruit.

agro-climatic conditions showed significant variations in plant growth, leaf size, fruit size, yield and fruit quality; genotypes with large size leaves are more likely to produce larger size fruits (Samadia, 2005). 7.1.2 Worldwide importance Cordia myxa is important in a number of cultures, in which it has several uses and applications. The Bobo people in Burkina Faso, for instance, consume the fruit and seeds, use the leaves for medicinal purposes, and consider the wood too sacred to be burnt (Weaver and Anderson, 2007). To give another example, the low productivity of khadins (a type of farming system for producing food grain, which is important in many areas around the world, especially in the western region of the

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Indian arid zone) can be overcome by planting trees such as Cordia myxa (Prasad et al., 2004). Furthermore, although in some regions the Cordia myxa does not require formal cultivation, it helps to improve the dietary status of local people, especially in certain regions of Asia and Africa (Aberoumand, 2009a). 7.1.3 Culinary uses, composition, nutritional value and health effects Cordia myxa cultivation is not widespread. It is grown on a limited scale, especially in domestic gardens, In the state of Kuwait and other gulf countries, where it is known as Bambar, it is a popular summer fruit that can be eaten fresh when it is ripe or picked partially ripe for processing or pickling. Similar practices are also followed elsewhere. It is valued for its attractive aroma, delectable full round shape, pink color and fruity sweet flavor. Its popularity has been decreasing recently, though, probably as a result of its high perishablility, and hence short shelf life and limited marketability. Most of the published papers about the Cordia species have focused on its composition and its nutritional, medicinal and toxicological properties. Compositional analysis shows that on a dry weight basis, Cordia myxa contains about 6.21% water, 12.75% glucose, 9.38% fructose, 29.09% sucrose, and 5.86% starch (which is relatively low for a fruit), 248 mg 100 gm−1 phytic acid and 1.39 TIU g−1 trypsin inhibitor (Aberoumand, 2009b). It also contains 25.7g. 100g−1 total dietary fiber (relatively high compared to other fruits), as well as 4.5% pectin (Aberoumand and Deokule, 2010). The fruit also contains 6.7% ash, 1.62 mg g−1 sodium, 7.83 mg g−1 potassium, 0.46 mg g−1 calcium, 0.51 mg g−1 iron and 0.35 mg g−1 zinc (Aberoumand and Deokule, 2009). Fageria et al. (2003) studied the effect of blanching and sulfitation on the composition and quality of Cordia myxa fruits at different maturation stages. They found that harvesting the fruit at 45 days and blanching for 3 minutes with 0.3% potassium metabisulphite (KMS) produced fruits with better sensory quality, higher drying ratios, and higher levels of total soluble solids, ascorbic acid, protein and carbohydrates. Several researchers have investigated the antimicrobial (de Carvalho et al., 2004; de Souza et al., 2004; Ioset et al., 2000), anti-inflammatory (Sertie et al., 2005; Al-Awadi et al., 2001; Akhtar and Ahmad, 1995), structural and functional properties of components of its fruit (da Silva et al., 2004; Benhura and Chidewe, 2002; Gabbrielli et al., 1993), and some medicinal properties (Canales et al., 2003; Lans et al., 2000) of different parts of the plant. Extracts of Cordia leaves exhibit significant analgesic, anti-inflammatory and anti-arthritic activities (Ficarra et al., 1995). Such activities are thought to be attributed to various flavonoids and phenolic compounds found in the leaves. Four flavonoid glycosides, robinin, rutin, datiscoside and hesperidin, were determined in the Cordia extracts, together with one flavonoid aglycone, dihydrorobinetin, and two phenolic derivatives: chlorogenic and caffeic acid. When acute colitis was induced in the colon of rats, myeloperoxidase activity was high and levels of glutathione peroxidase, superoxide dismutase and trace

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elements were low. Treatments composed of Cordia myxa fruits reversed these colitis-induced changes in the colon, liver and plasma of colitic rats. It is thought that this anti-inflammatory effect is caused by the antioxidants present in the fruit (Al-Awadi, 2001). A study suggested that the fruit’s strong antioxidant activity enhances the activity of Cordia myxa against carbontetrachloride or acetamideinduced fibrosis in rats (Afzal et al., 2007). Another investigation showed that the protective role of the fruit against fibrosis induced in rats by carbontetrachloride and thioacetamide could be due to the phenolic content of 11.1 mg g−1 gallic acid equivalent and to the antiradical activity, which is measured to be 10.0 (ARA percent) ascorbic acid equivalent (Afzal et al., 2009). The closely-related species Cordia dichotoma is also popular in certain cultures for medicinal uses. This is due to the anti-inflammatory compounds alpha-amyrin and 5-dirhamnoside in the seeds and allantoin, β-sitosterol and 3′, 5-dihydroxy-4′-methoxy flavanone-7-Oα-L-rhamnopyransoide in the bark (Orwa et al., 2009).

7.2

Fruit development postharvest physiology

7.2.1 Fruit growth, development and maturation Plate XII (see colour section between pages 244 and 245) shows how size, shape and color of Cordia myxa fruits change as the fruit matures; Al-Ati, 2010). As it matures, the fruit changes color from green (G) (not ripe), yellowish-green (YG), greenish-yellow (GY), yellow (Y) (fully ripe) and freckled yellow (FY). During the maturation stage the flavor of the fruit also goes through significant changes: while it starts off very astringent (inedible), it acquires a mild sweetness at the yellow stage which is most favored by consumers. The unripe Cordia myxa fruit is conical in shape, while fully ripe fruit are round and two to three times larger in size (Plate XII: see colour section). The skin of the fruit is very smooth and, once it reaches full maturity, becomes very delicate and hence very susceptible to even mild mechanical damage. When the fruit is immature, the flesh surrounding the seed is hard, but becomes gel-like as maturity advances acquiring its sweet, fruity flavor as it does so. The diameter of a fully mature fruit ranges from 26.4 to 33.1 mm.

7.3

Maturity and quality indices

Quality tests of Cordia myxa reveal that, on average, the fully ripened fruit have: 21.2% moisture, 22.6% soluble solids concentration, pH 6.6, titratable acidity (percentage malic acid) 1.2 (Al-Ati, 2010). The complexity of the taste and flavor is mainly controlled by pH and TA, which determine the sourness and acidity of the fruit, and the SSC determines sweetness (Mitcham et al., 1996). The values of these parameters are therefore important attributes for Cordia myxa because they are most likely to be involved in the development of the unique flavor of the fruit. To compare Cordia myxa with other fruits, the TA of pineapple was reported to be 1.0% and its SSC is about 12%; while pomegranate has a TA of 1.4%, and its

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SSC is 17% (Kader, 2002). Also, a test examining the textural properties of the fruit show that the fully ripe Cordia myxa has an average firmness of 1.56 Kg. This is reduced drastically when stored at 8°C for ten days to an average firmness of 0.704 Kg (Al-Ati, 2010).

7.4

Postharvest handling factors affecting quality

There have been very few postharvest studies of Cordia myxa. As mentioned above, the fruit is known for its sensitivity to rough handling and is therefore prone to mechanical damage. Cushioned packaging materials may help protect the fruit and its skin from such damage. Water loss seems to diminish the fruit’s storage life significantly. According to AOAC (2002), the rates of water loss were investigated in a study by Al-Ati (2010). When the fruit was stored at room temperature for one day, the result was an average water loss of 1.6 g at the yellowish stage of ripeness, 2.5 g at the greenish-yellow stage, and 2.7 g at the yellow stage. However, at day 14 water loss became 4.9 g at greenish-yellow, 7.0 g greenish-yellow and 8.2 g at yellow stage of ripeness. Since a 5 to 8% decline in the water content of peaches and nectarines can result in shriveling that is visible to consumers (Mitcham and Mitchell, 2002), Cordia myxa should perhaps be harvested at the yellowish-green stage to help to maintain fruit weight and minimize shriveling.

7.5

Conclusions

Cordia myxa is very popular in certain Asian and African cultures due to its medicinal properties. Researchers have now begun to identify the fruit’s nutritional value and demonstrate the health benefits of its components. However, cultivation is still very limited worldwide, and it is of no apparent economic value to any specific country. The cultivation of Cordia myxa in the countries in which it can be grown and the promotion of its consumption in different forms (fresh, pickled, etc.) can help societies in these countries to meet their nutritional needs. It has the potential to be a successful commercial product, either as a whole fruit or as an ingredient in a variety of processed food products, but this potential has yet to be exploited. Current postharvest practices are insufficient to preserve, protect and extend the shelf life of the fruit, and do not allow it to be marketed long distances from its place of cultivation. Further studies on the fruit’s postharvest biology and the effects of handling practices are required. These could promote global recognition of the fruit and encourage plant physiologists and technologists to study the fruit in more detail. Improved postharvest practices could also enable it to be exported internationally. Some basic properties of the fruit, such as its respiration rate, have not been measured, and therefore the effect of modified atmosphere packaging and controlled atmosphere storage are not known. Diseases of Cordia myxa trees

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and causes of fruit quality deterioration and senescence patterns of fruits have also not been studied. Identifying and studying these would be beneficial. Lastly, a product development approach could also help to produce different food, nutraceutical and pharmaceutical products based on Cordia myxa. Such an approach could increase the demand for this nutritious fruit worldwide.

7.6

References

Aberoumand A. (2009a), ‘Preliminary assessment of nutritional value of plant-based diets in relation to human nutrients’, International Journal of Food Science & Nutrition, 60 (Supplement 4), 155–162. Aberoumand A. (2009b), ‘Balance between nutrients and anti-nutrients in some plant food’, Asian Journal of Food and Agro-Industry, 2, 334–339. Aberoumand A. and Deokule S. (2009), ‘Determination of elements profile of some wild edible plants’, Food Analytical Methods, 2, 116–119. Aberoumand A. and Deokule S. (2010), ‘Assessment of the nutritional value of plant-based diets in relation to human carbohydrates: A preliminary study’, Advance Journal of Food Science and Technology, 2, 1–5. Afzal M., Obuekwe C., Khan A. and Barakat H. (2007), ‘Antioxidant activity of Cordia myxa L. and its hepatoprotective potential’, Electronic Journal of Environmental, Agricultural and Food Chemistry, 6(8), 2,236–2,242. Afzal M., Obuekwe C., Khan A. and Barakat H. (2009), ‘Influence of Cordia myxa on chemically induced oxidative stress’, Nutrition and Food Science, 39(1), 6–15. Akhtar A. and Ahmad K. (1995), ‘Anti-ulcerogenic evaluation of the methanolic extracts of some indigenous medicinal plants of Pakistan in aspirin-ulcerated rats’, Journal of Ethnopharmacology, 46(1), 1–6. Al-Ati T. (2010), ‘Fruit quality attributes of Cordia myxa grown in the State of Kuwait’ (unpublished paper). Al-Awadi F., Srikumar T., Anim J. and Khan I. (2001), ‘Antiinflammatory effects of Cordia myxa fruit on experimentally induced colitis in rats’, Nutrition, 17(5), 391–396. AOAC (2000), Official Methods of Analysis, 17th edn, Association of Official Analytical Chemists, Washington, D.C. Benhura M. and Chidewe C. (2002). ‘Some properties of a polysaccharide preparation that is isolated from the fruit of Cordia abyssinica’, Food Chemistry, 76(3), 343–347. Canales T., Avila J., Duran A., Caballero J., de Vivar A. and Lira R. (2003), ‘Ethnobotany and antibacterial activity of some plants used in traditional medicine of Zapotitlan de las Salinas, Puebla (Mexico)’, Journal of Ethnopharmacology, 88(2–3), 181–188. da Silva S., Rodrigues M., Agra M., da Cunha E., Filho J. and da Silva M. (2004), ‘Flavonoids from Cordia globosa’, Biochemical Systematics and Ecology, 32(3), 359–361. de Carvalho P., Rodrigues R., Sawaya A., Marques M. and Shimizu M. (2004), ‘Chemical composition and antimicrobial activity of the essential oil of Cordia verbenacea’, Journal of Ethnopharmacology, 95(2–3), 297–301. de Souza G., Haas A., von Poser G., Schapoval E. and Elisabetsky E. (2004), ‘Ethnopharmacological studies of antimicrobial remedies in the south of Brazil’, Journal of Ethnopharmacology, 90(1), 135–143. Fageria M., Preeti K. and Dhaka R. (2003), ‘Effect of fruit harvesting stages and processing treatments on the quality of sun dried fruits of lehsua (Cordia myxa Roxb.)’, Journal of Applied Horticulture, 5(1), 32–38. Ficarra R., Ficarra P., Tommasini S., Calabro M. L., Ragusa S. et al. (1995), ‘Leaf extracts of some Cordia species: analgesic and anti-inflammatory activities as well as their chromatographic analysis’, Farmaco, 50(4), 245–256.

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Gabbrielli G., Trovato A., Rapisarda A. and Ragusa S. (1993), ‘In Vitro cytotoxic effect of the leaves of some species of Cordia’, Pharmacological Research, 27 (Supplement 1), 115–116. Ioset J., Marston A., Gupta M. and Hostettmann G. (2000), ‘Antifungal and larvicidal cordia quinines from the roots of Cordia curassavica’, Phytochemistry, 53(5), 613–617. Kader A. (2002), ‘Quality and safety factors: definition and evaluation for fresh horticultural crops’, In Kader A, Postharvest Technology of Horticultural Crops, California, University of California, 279–285. Lans C., Harper T., Georges K. and Bridgewater E. (2000), ‘Medicinal plants used for dogs in Trinidad and Tobago’, Preventive Veterinary Medicine, 45(3–4), 201–220. Mitcham B., Cantwell M. and Kader A. (1996), ‘Methods for determining quality of fresh commodities’, Perishable Handling Newsletter, 1(85), 1–5. Mitcham E. and Mitchell F. (2002), ‘Postharvest handling system: pome fruits’, In Kader A, Postharvest Technology of Horticultural Crops, California, University of California, 347. Orwa C., Mutua A., Kindt R., Jamnadass R. and Simons A. (2009), Agroforestree Database: a tree reference and selection guide version 4.0. Available from: http://www. worldagroforestry.org/sites/treedbs/treedatabases.asp [accessed 10 May 2010]. Oudhia P. (2007), Cordia myxa L. [Internet] Record from Portabase. Schmelzer G. H., and Gurib-Fakim A. (eds), PROTA (Plant Resources of Tropical Africa/Resources vegetales de l’ Afrique tropicale), Wageningen, Netherlands. Available from: http://database.prota. org/search.htm [accessed 10 May 2010]. Prasad R., Mertia R. and Narain P. (2004), ‘Khadin cultivation: a traditional runoff farming system in Indian desert needs sustainable management’, Journal of Arid Environments, 58(1), 87–96. Samadia D. (2005), ‘Genetic variability studies in Lasora (Cordia myxa Roxb.)’, Indian Journal of Plant Genetic Resources, 18(3), 236–240. Sertie J., Woisky R., Wiezel G. and Rodrigues M. (2005), ‘Pharmacological assay of Cordia verbenacea V: oral and topical anti-inflammatory activity, analgesic effect and fetus toxicity of a crude leaf extract’, Phytomedicine, 12(5), 338–344. University of Arizona (2009), Campus Arboretum. Available from: http://www.arboretum. arizona.edu/taxa/Cordia_myxa.html [accessed 10 May 2010]. Weaver R. and Anderson P. (2007), ‘Botany section’, Tri-Ology, 46(3), 1–2.

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8 Avocado (Persea americana Mill.) E. M. Yahia, Autonomous University of Queretaro, Mexico and A. B. Woolf, The New Zealand Institute for Plant & Food Research, New Zealand

Abstract: Avocados are a subtropical climacteric fruit that is generally oblong in shape and green skinned, although ‘Hass’, the dominant commercial cultivar, ripens to purple-black. They are one of the few fruits that contain significant amounts of oils (fatty acids). The high concentrations of monounsaturated fatty acids and other phytochemicals make avocado a very healthy and nutritious fruit. Avocados do not ripen unless removed from the tree, meaning fruit can be mature but ‘tree stored’ for as long as 12 months. Increased commercial maturity is associated with increased fruit size, oil and dry matter content, and decreased ripening times. Avocados have a relatively short storage life, limited primarily by the expression of internal chilling injury (CI) symptoms, but rots are a limitation for fruit grown in many countries. Optimum storage temperature is generally around 6°C, and temperatures below 3 to 4°C (depending on cultivar and time in the season) lead to external CI (skin blackening). Controlled atmosphere storage and 1-MCP (SmartFreshSM) are effective commercial tools for improving storage life. Since avocado cannot be consumed unripe, an increasingly important commercial tool is the use of ethylene to hasten and synchronize ripening. New processing options, such as cold-pressed oil extraction and high-pressure processing, are receiving increasing attention. Key words: Persea americana, avocado, postharvest, chilling injury, pests, diseases, oil, processing.

8.1

Introduction

8.1.1 Origin, botany, morphology and structure Avocado is a dicotyledonous plant from the Ranales order and the Lauraceae family. It was classified as Persea gratissima by Gaertner, and Persea americana by Miller. P. americana developed subspecies because of geographical isolation, which finally originated into different botanical types. The avocado tree (Persea americana Mill.) belongs to the family Lauraceae and is one of the few commercially significant members of the genus Persea. The fruit is called Ahuacatl by the Aztecs

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in Mexico and from there derived the term ‘avocado’, aguacate (in Spanish), avocat (in French) and abacate (in Portuguese). The Aztecs considered avocados an aphrodisiac and called it huacatl, meaning testicles, reflecting the fruit shape. The fruit is also called palta in Chile, Ecuador and Peru, and has been referred to by a number of other terms such as alligator pear, vegetable butter, butter pear and midshipman’s butter (Yahia, 2011). The avocado originated in Central America and southern Mexico. Based on archaeological evidence found in Tehuacán, Puebla (Mexico), it is believed to have appeared approximately 12,000 years ago (Yahia, 2011). It has been determined that the centre of origin of this fruit is the central part of Mexico, passing through Guatemala to Central America. In this region, the natural gene stock can be found, which can be useful for the biotechnological improvement of the species. As evidence for this theory, primitive avocado trees have been found in the ‘Oriental Sierra Madre’ along from the State of Nuevo León (Mexico) to Costa Rica. From this region, avocado dispersed to the south-eastern part of the USA, the West Indies, and then to a large part of South America (Colombia, Venezuela, Brazil, Ecuador, Peru, Bolivia, Chile; Rodríguez Suppo, 1992; Yahia, 2011). The avocado is botanically classified into three races, with differences in fruit maturity and oil content between the different races (Biale and Young, 1971). West Indian (WI), Persea americana Mill. var. americana (P. gratissima Gaertn.), are tropical with large variably shaped fruit and lower oil content; Mexican (MX), P. americana Mill. var. drymifolia Blake (P. drymifolia Schlecht. & Cham.), are semitropical with smaller elongated thin-skinned fruit and higher oil content; and Guatemalan (G), P. nubigena var. guatemalensis L. Wms., are subtropical with mostly round thick-skinned fruit and intermediate oil content (Bergh and Lahav, 1996). The Mexican race, which originated in the mountains of Mexico and Central America, is characterized by relatively small fruit, ranging from 75 to 300 g, with a thin, smooth skin. Mexican race fruit are mostly green skinned (the natural seedling ‘criollo’ is black skin), and the pulp is green in colour with very high oil content (up to 30% by fresh weight). Mexican cultivars are well adapted to the cool climates of the tropics and subtropics and are the most cold-tolerant of the three races. Mature trees of the Mexican race are capable of withstanding temperatures as low as −4°C without damage (Joubert and Bredell, 1982). The West Indian race is native to the lowlands of Central America and northern South America, and these are best adapted to lowland tropical conditions of high temperature and humidity. They are characterized by intermediate fruit size, with smooth, leathery and sometimes glossy skin. Generally, West Indian avocado trees are the most cold (frost)-sensitive and are damaged by temperatures below −1.2°C (Joubert and Bredell, 1982). While racial ancestry was identified as the most important factor influencing susceptibility to cold, other factors such as tree size, age and vigour, crop load and cultural practices were also shown to influence cold damage (Malo et al., 1977; Yahia, 2011). Fruit of the Guatemalan race are native to the highlands of Central America. The Guatemalan cultivars are intermediate between the other two cultivars with respect to climatic adaptation. Guatemalan fruit are large, averaging 500 to 600 g,

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and characterized by thick brittle peel, high oil content and nutty flavoured pulp (Storey, 1988; Yahia, 2011). Systematic studies have classified more than 500 varieties; however, many are not commercially produced, because of productivity problems (production time, amount of fruit), quality (protein and fat content), and handling problems (such as resistance to damage during transportation). Many of the commercial cultivars are hybrids of the three races. There is great variability in fruit traits not only between races but also between cultivars within a race. One of the most distinct differences between cultivars is the peel colour when ripe. The peel of some cultivars changes from green to black or purple with advanced maturity or ripening. ‘Hass’, a Guatemalan-Mexican (G-MX) hybrid, is a black-skinned (when ripe), ovate cultivar whose fruit weighs 140 to 300 g (Yahia, 2011) (Fig. 8.1). ‘Hass’ is the most important commercial cultivar worldwide, and the predominant cultivar in the important production countries (Mexico, Chile and the USA) and is also important in other smaller producer countries (e.g. Spain, Australia and New Zealand). Some other commercial cultivars include ‘Bacon’, ‘Fuerte’, ‘Gwen’, ‘Ryan’, ‘Lamb Hass’, ‘Pinkerton’, ‘Reed’, ‘Sharwil’, ‘Edranol’ and ‘Zutano’. The main Florida cultivars (West Indian and Guatemalan races and hybrids) are ‘Simmonds’, ‘Nadir’, ‘Booth 8’, ‘Choquette’ and ‘Lula’. With the exception of ‘Reed’, which is believed to be entirely of the G race, the other cultivars are considered primarily G-MX hybrids. ‘Sharwil’ is a MX-G cross and represents more than 57% of the commercial acreage in Hawaii. Its green-skinned fruit weigh 220 to 560 g, matures in winter and spring, and has small seeds and greenish-yellow flesh with a rich, nutty flavour (Yahia, 2011).

Fig. 8.1

Change of colour after ripening in ‘Hass’ avocado.

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The avocado fruit can be round, pear shaped, or oblong, and the skin of the fruit may vary in texture and colour. The skin may be pliable to woody, smooth to rough, and green-yellow, reddish-purple, purple, or black in colour. The flesh of the fruit is greenish-yellow to bright yellow when ripe and buttery in consistency, but inferior varieties may be fibrous. The avocado fruit has one large seed, which makes up to 10 to 25% of the fruit weight. The fruit of different avocado cultivars vary in moisture and oil content, from less than 5% to more than 30% oil (Yahia, 2011). 8.1.2 Worldwide importance and economic value About 349 000 ha (2007 data) are dedicated to the production of avocado in about 60 countries, producing more than 2.6 million tonnes annually (Table 8.1), with average yield of about 7.40 tonnes per ha. Mexico is the leading producer, accounting for about 34% of the total production, with other important producing countries including Chile (7.6%), Indonesia (6.1%), USA (5.7%), Colombia (4.8%), the Dominican Republic (5.1%), Brazil (4.7%), and Peru (3.7%; FAO statistics). The largest importers of avocado are USA (47%), France (15%), the Netherlands (8%), UK (6%) and Japan (4%) (Yahia, 2011). 8.1.3

Culinary uses, nutritional value and health benefits

Avocado consumption and culinary uses Avocado consumption (Table 8.2) is concentrated in the major producing areas. US per capita consumption of fresh avocados increased from 0.18 kg in 1970 to Table 8.1 Production of avocado in different countries, 2007 Ranking

Volume (tons)

Country

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

734 456 160 657 129 576 101 247 108 509 120 878 99 026 78 220 77 115 73 523 60 175 59 121 55 210 53 533 41 901 2 121 667

Mexico Chile Indonesia Colombia Dominican Republic United States of America Brazil Peru Spain Guatemala Kenya China Israel Venezuela South Africa World total

Source: FAOSTAT, 2008.

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Consumption of avocado in the European Union, 1999

Country

Kg per person year−1

Country

Kg per person year−1

Austria Bel-Lux Denmark Finland France Germany Greece

0.160 0.899 0.580 0.150 1.420 0.157 0.228

Ireland Italy Netherlands Portugal Spain Sweden United Kingdom

0.194 0.033 1.128 0.035 0.596 0.610 0.315

0.68 to 1.0 kg in the late 1980s, and in 2000 ~1.4 kg. This is equivalent to consumption of nectarines and comparable to that of pineapples (0.77 kg), but considerably less than bananas (11 kg), apples (8.7 kg) and oranges (6.6 kg). Avocado is consumed as a fresh fruit, besides its use in the oil, cosmetic, soap, and shampoo industries. Unlike many fruits that typically have a sweet or acidic taste, avocados have a smooth, buttery consistency and a rich flavour. A popular use is as a salad fruit, but avocados are also processed into guacamole and can be used in sandwich spreads. Oil extracted from avocados can be used for cooking and preparation of salads, sauces and marinades. Cold-pressed avocado oil (using extraction technologies similar to those for olive oil) for culinary use is a relatively new processed product (Woolf et al., 2009), compared with olive oil. Avocado oil (typically refined after extraction) is used for skin care products such as sunscreen lotions, cleansing creams, and moisturizers, or for hair conditioners and makeup bases. Several more uses have been added around the world. For example, in Mexico and Brazil, it is added to ice creams and sorbets; in Japan it is eaten in sushi rolls; in Cuba the pulp is mixed with capers, green olives, lemon juice and olive oil to make a sauce that is served with steamed fish; and in Nicaragua it is stuffed with cheese, fried and baked. In Taiwan, it is eaten with milk and sugar; in Korea it is mixed with milk and used as a facial cream and body lotion; in Indonesia it is mixed with coffee, rum and milk to make a refreshing beverage; in the Caribbean it is mixed with salt, garlic, and coconut and served as an entrée; and in the Philippines the avocado purée is mixed with sugar and milk to make a beverage that is served as a dessert (Yahia, 2003). Nutritional value and health benefits Consumers have a mixed perception of avocados, some considering them healthy (Lerman et al., 1994), while others who are aiming to lose weight believe avocados are fattening because of their high fat content (25 to 30% w/w FW). However, Pieterse et al. (2005) found in a study with 55 subjects who were on an energyrestricted diet, that the consumption of 200 g day−1 of avocado instead of 30 g of mixed dietary fat did not reduce weight loss compared with a control group. They also found no effect on serum lipid concentrations.

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Mono-unsaturation of the lipids: The lipid content of avocados is made up of approximately 15 to 20% saturated fats, 60 to 80% monounsaturates and ≅10% polyunsaturates. A diet high in monounsaturated fatty acids (MUFAs) is recommended on healthy grounds. This diet has shown favourable effects on lipoprotein measurements, endothelieum vasodilation, insulin resistance, metabolic syndrome, antioxidant capacity, and myocardial and cardiovascular mortality (Serra-Majem et al., 2006). The healthy Mediterranean diet recommends abundant plant foods and olive oil as the principal source of dietary lipids. Avocados and avocado oil have a very similar lipid profile to olives and olive oil, and hence can be included as a healthy addition to the Mediterranean diet. Avocados also contain significant amounts of other beneficial healthy compounds including tocopherols (vitamin E), plant pigments, sterols, fibre, and folate (Yahia, 2011) (Tables 8.3 to 8.5). Table 8.3 Avocado fruit composition Component Water (%) Lipids (%) Proteins (%) Fibre (%) Ash (%) Sugars (%) Glucose Fructose Sucrose Organic acids (%) Malic acid Citric acid Oxalic acid Vitamins (mg 100 g−1) Ascorbic acid Thiamine Riboflavin Nicotinic acid Vitamin B6 Folic acid Biotin Carotenoids (mg 100 g−1) α-carotene β-carotene Criptoxanthin Minerals (mg 100 g−1) Potassium Phosphorus Calcium Magnesium Sodium Iron Zinc

Quantity 74.4 20.6 1.8 1.4 1.2 0.30 0.10 0.10 0.32 0.05 0.03 11.0 0.07 0.12 1.9 0.62 0.04 0.006 0.29 0.03 0.16 480 27.0 14.0 23.0 2.0 0.7 0.5

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Nutritional content (g 100 g−1) of some avocado cultivars grown in Mexico

Variety

Moisture

Ash

Fat

Protein

Carbohydrates

Total fibre

Pellejo Grande Verde Hass

1.10 0.50 1.10 1.30

1.37 1.37 1.81 1.60

1.37 1.37 1.81 1.60

1.37 1.37 1.81 1.60

3.70 4.82 5.89 5.60

3.73 2.25 0.40 –

Table 8.5 Vitamin content (mg 100 g−1) in three avocado cultivars Vitamins

‘Fuerte’

‘Hass’

‘Anaheim’

Thiamine Riboflavin Niacin Pantoteic acid Pyridoxine* Folic acid Biotin

0.12 0.22 1.45 0.90 0.61 0.03 0.005

0.09 0.23 2.16 1.14 0.62 0.04 0.006

0.08 0.21 1.56 1.11 0.39 0.018 0.0034

Note: *Including pyridoxal and pyridoxamine.

Vitamin E: Avocados have high concentrations of the antioxidant α-tocopherol (vitamin E), with as much as 2.87 mg 100 g−1 flesh reported for ‘Hass’ avocados (Lu et al., 2005) (Table 8.5). Requejo-Jackman et al. (2005) reported concentrations ranging from 5.5 to 9.0 mg 100 g−1 oil, in oil extracted by cold-pressed extraction for a range of different cultivars grown in New Zealand. Pigments: Avocados contain high concentrations of carotenoids and chlorophylls (Table 8.4). Carotenoids have been studied for their antioxidant capacities and ability to protect against diseases. These active components have been associated with a reduced risk of cancer and other chronic diseases. Avocados contain high amounts of lutein, which is known to reduce age-related macular degeneration (Richer et al., 2004). Lu et al. (2005) reported 2.93 μg g−1 FW in the pulp of ‘Hass’ avocados. Ashton et al. (2006) determined the carotenoid concentrations in the skin and flesh sections (dark green, pale green, yellow) of the avocado and found differences across these tissues, and that these decreased with ripening after harvest. Alpha- and β-carotene have pro-vitamin A activity; their presence in the fruit enhances greatly its health-giving benefits. There is also a strong correlation between ingestion of foods with high chlorophyll concentrations and a decreased risk of certain types of cancer (Minguez-Mosquera et al., 2002). Chlorophyll concentrations are highest in the skin of avocado (≅186 μg g−1 FW), then decrease moving inwards from the dark green flesh to the yellow flesh, 38 to 2.2 μg g−1 FW, respectively (Ashton et al., 2006). Plant Sterols: Avocados also contain high amounts of plant sterols, the main sterol being β-sitosterol (Piironen et al., 2003). Plant sterols are known to decrease

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cholesterol absorption if 1.5 to 2 g of sterols is consumed per day. Avocado oil from a variety of cultivars was found to contain 2.25 to 4.3 mg g−1 FW, with the highest concentration in ‘Hass’ (Requejo-Jackman et al., 2005). Avocados also contain a high concentration of folate (0.04 mg 100 g−1), which is recommended for women of child-bearing age to reduce the risk of neural birth defects (South African Avocado Growers’Association, www.avocado.co.za). The amount of dietary fibre in avocados is also high, at 6.72 g 100 g−1 (Li et al., 2002).

8.2

Fruit development and postharvest physiology

8.2.1 Fruit growth, development and maturation The pericarp, which is the fruit tissue proper excluding the seed, comprises the rind (exocarp), the fleshy edible portion (mesocarp), and a thin layer next to the seed coat (endocarp) (Biale and Young, 1971). The large seed of the avocado consists of two fleshy cotyledons, a plumule, a hypocotyl, a radicle and two seed coats adhering to each other. The endosperm disappears in the course of development. The cotyledons consist of parenchyma tissue interspersed with idioblasts (oil-containing cells) and contain starch as the main storage material (Biale and Young, 1971). The avocado fruit is unusual, in that cell division in the mesocarp is not restricted to the initial period of growth but also continues during fruit development and even occurs in the mature fruit attached to the tree (Van Den Dool and Wolstenholme, 1983; Lewis, 1978). In some cases, cell enlargement stops when the fruit reaches about 50% of its size at full maturity, while cell division accounts for the continued growth (Cummings and Schroeder, 1942). 8.2.2 Hormonal control of fruit development Two important endogenous factors affecting the physiology of fruit growth are hormones and nutrients (Bower and Cutting, 1988; Cutting et al., 1986b; 1986c). At all stages of fruit development, it was observed that the mesocarp contained lower amounts of the auxin, indole acetic acid (IAA), than the seed and testa (Cutting et al., 1985). Auxin increases the skin strength of the fruit and regulates endosperm development. There is strong evidence that ethylene is involved in the abscission of young avocado fruitlets, since Davenport and Manners (1982) observed that an increase in ethylene did not occur in fruit that failed to abscise. The prevention of the ethylene peak and associated fruitlet abscission could, therefore, be under the control of other plant growth substances such as cytokinins, which showed a strong peak during this period. Blumenfeld and Gazit (1970) found high amounts of cytokinins in both the cotyledons and testa of avocado, which decreased with development. The high amounts of cytokinin activity in the young seed served to increase the sink strength of the fruit for nutrients and other metabolites. The high cytokinin amounts detected in young fruitlets may actively assist in increasing the sink strength of the fruit, and therefore promote fruit growth (Bower and Cutting, 1988). Stress-induced increases in abscisic acid

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(ABA) cause an irreversible loss in fruit growth, and the physiological mechanism associated with ABA-induced retardation of ‘Hass’ avocado fruit growth appears to be inextricably linked to a decline in cytokinin content and includes: reduction in mesocarp and seed coat plasmodesmatal branching, gating of mesocarp and seed coat plasmodesmatal by deposition of electron dense material in the neck region, abolition of the electrochemical gradient between mesocarp and seed coat parenchyma, and arrest of cell-to-cell chemical communication (Moore-Gordon et al., 1998). Adato and Gazit (1976) were unable to elicit initiation of fruit ripening, except with a very high dose of IAA. IAA decreases to low concentrations in all parts of the fruit with the onset of maturity (Wolstenholme et al., 1985). A direct role of auxins in the initiation and development of the ripening response is not clear. Gazit and Blumenfeld (1970a) showed low concentrations of cytokinin activity in the mesocarp by the time the fruit was mature. Cutting et al. (1986a; 1986b; 1986c) were unable to confirm the role of cytokinins in avocado fruit ripening, although there were indications that the interaction with ABA may occur, as suggested by Lethman and Palni (1983). Lieberman et al. (1977) found that exogenous addition of gibberellins had little effect on avocado ripening. They showed an increase in ethylene and ripening following application of ABA before the climacteric peak, but depressed evolution if applied after the peak, concluding that ABA accelerates ageing. Gazit and Blumenfeld (1972) reported little change in ABA concentration during fruit development, but once ripening started, a considerable increase occurred. They have also reported that the increase in ABA closely followed the ethylene curve, with peaks at the same time. Bower et al. (1986) found that the free ABA content in ripening avocados increased with fruit softening, with the peak at approximately the same degree of softness at which the maximum ethylene peak occurred, and declined thereafter. Factors other than water stress can also affect both ABA concentrations and ripening rate. 8.2.3 Respiration, ethylene production and ripening Avocado differs from most other fruits in that ripening does not normally take place on the tree, but only after picking (Schroeder, 1953). This means that they can be held on the tree even for many months after they are physiologically mature (that is to say, will ripen normally after removal from the tree). After harvest, their ‘resistance’ to ripening is lost within one to two days (Gazit and Blumenfeld, 1970a) and fruit will ripen, although the time to ripen will reduce with increasing time on the tree (often loosely referred to as ‘maturity’ by industry). Time to ripen decreases with time in storage, and (Gazit and Blumenfeld, 1970b) treatment (‘pre-ripening’, ethylene conditioning or conditioning), as carried out for bananas, is becoming an important tool for providing consumers with ‘ripe tonight’ fruit. Fruit ethylene production begins after harvest and increases greatly with ripening to >100 μl C2H4 kg−1 h−1 at 20°C. Avocados are best ripened at 15 to 20°C (Hopkirk et al., 1994). The ripening rate at 25°C may result in increased

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decay, uneven ripening of the flesh and off-flavours. Fruit generally ripen better (more evenly and with less rots) if they are stored for one or two weeks, then ripened at 20°C. However, if fruit are to be ripened at 25°C, then final quality is better if the fruit are not refrigerated but held at a temperature closer to the final ripening temperature. Following ripening, fruit should be pre-cooled to less than 5°C and held for ~ a week at most. Ripe (soft) avocados require care in handling to minimize physical damage. Respiration and ethylene production The avocado is a climacteric fruit, with a marked rise in respiration rate and ethylene production at the onset of ripening, followed by a decline (Zauberman and Schiffman-Nadel, 1972). The respiration rate of avocado fruit is relatively high compared with that of many other fruits; about 20 to 50 mg CO2 kg−1 h−1 at 5°C, 50 to 160 at 10°C, and 80 to 300 mg CO2 kg−1 h−1 at 20°C (Kader and Arpaia, 2001). Rates of ethylene production are generally low for unripe avocados, 100 μL kg−1 h−1 at 20°C when fully ripe. Thus, the implications for ethylene on avocados depend on the physiological state of the fruit. For unripe, newly harvested fruit recently placed into storage, ethylene concentrations will be undetectable and exposure to ethylene will result in an increased ripening rate, and reduced storage and shelf life. However, ripe fruit will produce significant ethylene in storage and thus should be kept separate from unripe avocado or other ethylene-sensitive products. Because avocados are sensitive to ethylene, they should not be stored near ripe fruit or other fresh produce that produce more than trace ethylene (Chaplin et al., 1983). Ethylene exposure during storage accelerates ripening/softening and can increase incidence and severity of internal chilling injury (CI) and decay. Exogenous applications of ethylene after harvest cause an earlier climacteric with consequent ripening (Eaks, 1978). Although other factors initiate the respiratory rise, alter sensitivity to ethylene, or control its increase, the autocatalytic production of ethylene is of vital importance to normal avocado ripening. Any factors affecting this process could be expected to alter the fruit-ripening pattern. 1-methylcyclopropene (1-MCP) 1-MCP works by binding to the ethylene receptors, thus preventing ethylene binding and subsequent action. The main response in avocado is delayed ripening. This means that treatment with high concentrations (e.g. 10 μL L−1) can result in fruit remaining unripe for weeks at room temperature without softening. The first published work (Feng et al., 2000) examined the ripening response of a range of cultivars (‘Ettinger’, ‘Hass’, ‘Reed’ and ‘Fuerte’) after 1-MCP treatment and showed that even 30 to 70 nL L−1 could delay ripening at 20°C for over 10 days, including concomitant reduction in cell wall softening enzymes (PG and cellulase) and climacteric ethylene production. This effect was observed even though fruit were treated with 300 μL L−1 ethylene immediately after 1-MCP treatment, clearly demonstrating the ability of 1-MCP to bind with near-complete efficacy against subsequent ethylene exposure.

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1-MCP and wax significantly delayed the ripening of ‘Tower II’ avocados stored at 20°C (Jeong et al., 2003). Fruit treated with both 1-MCP and wax had better retention of green skin colour and fruit firmness, and delayed climacteric ethylene evolution and respiration rates than fruit under other treatments. Waxing alone reduced weight loss and delayed softening, but did not delay climacteric ethylene evolution and respiration rates. Whereas firmness of control fruit decreased from >100 to 20 N over a 7-day period at 20°C, fruit treated with both 1-MCP and wax required more than 11 days at 20°C to soften to 20 N. The firmness of waxed ‘Booth 7’ avocados declined from >170 to 15 N during 19 days’ storage at 13°C, whereas fruit treated with both 1-MCP and wax required nearly five weeks to reach firmness values of 25 N. Adkins et al. (2005) investigated the potential of 1-MCP to manipulate ripening of non-stored ‘Hass’ avocado fruit by treatment before or after ethylene and at different times during ripening, and found that ripening of fruit exposed to 100 μL L−1 ethylene for 24 h at 20°C could be delayed by up to 3.3 days by applying 1-MCP. However, once the fruit started to soften, there was little effect of 1-MCP, compared with non 1-MCP-treated fruit. There is little potential to control ripening using ethylene after treatment with 500 nL L−1 1-MCP, but higher concentrations may be more effective. 1-MCP binding to the receptors is irreversible, but over time, inhibition of ethylene effects can be overcome by production of new receptors (Sisler et al., 1996). In avocado, however, ‘restarting’ of the ripening process seems to be much harder to achieve than in other fruits. A possible reason for the apparent relative ‘irreversibility’ of 1-MCP in avocado was suggested by Dauny et al. (2003), who found that 1-MCP was absorbed faster and in greater amounts by ‘Hass’ avocados and avocado oil than by ‘Cox’s Orange Pippin’ apple fruit and water, respectively (Dauny et al., 2003). Thus, release of 1-MCP from the oil fraction and ‘re-binding’ to ethylene receptors may be the possible mechanism that influences ripening and 1-MCP efficacy in avocado. It has been found that for 1-MCP-treated avocado stored for four weeks, ethylene treatment has little effect on reducing average shelf life, even with high concentrations (1,000 μL L−1; Woolf and White, unpublished). Recent work in South Africa has suggested that CO2 treatment (20% for 24 h at 20°C) after storage may be a possible method of reversing the ripening inhibition (Roets et al., 2009). The key commercial benefit of 1-MCP is its ability to reduce the internal chilling injury (flesh greying or diffuse flesh discolouration) that occurs during storage, a ripening and/or ethylene-related disorder (Pesis et al., 2002; Woolf et al., 2005). This is discussed further below. 8.2.4 Cell wall metabolism and softening During avocado fruit ripening, it was found that the middle lamella of cell walls begins to disappear, with pectin removal from the matrix of the cell walls. Later, a loss of organization and density in the walls occurs and during the

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post-climacteric, the walls almost completely disappear (Platt-Aloia et al., 1980; Platt-Aloia and Thomson, 1981). Scott et al. (1963) reported cellulose as the major constituent of avocado cell walls. Huber (1983) considers the avocado to be the fruit most representative of those in which cellulases are of primary importance. Pesis et al. (1978) found a rapid increase in this enzyme accompanying softening, which was closely correlated with the respiratory climacteric and ethylene. Application of ethylene in the air surrounding fruit for 48 h after harvest also caused an increase in cellulase activity, which led Pesis et al. (1978) to conclude that ethylene plays a role in controlling cellulase activity. Tucker and Laties (1984) showed that ethylene treatment increases transcription of cellulaseencoding genes. The early stages of softening in the avocado appear to be due to cellulase, controlled at least in part by ethylene, with polygalacturonase (PG) responsible for final softening (Bower and Cutting, 1988). However, although Feng et al. (2000) found similar trends in cellulase activity, they suggested that the initial phase of avocado fruit softening appears to occur without significant PG activity. Jeong et al. (2002) observed a reduction in pectin methyl-esterase (PME) activity with ripening, and this was correlated with the delay associated with 1-MCP treatment.

8.3

Maturity, quality at harvest and phytonutrients

8.3.1 Maturity and quality at harvest Avocado is characterized by great natural variability. This is dramatically influenced by the very long period for which fruit can remain on the tree, as long as 18 months or more after flowering in some environments. Determining the point at which to commence commercial harvesting is of course important, and in avocado this can be a problematic area because of the relative lack of maturity indices compared with those in other crops. Harvesting fruit too early leads to poor ripening, often associated with shrivelling, rubbery texture, ‘stringy’ vascular tissue, watery/green flavour and increased rots (Lee et al., 1983; Pak et al., 2003; Pak and Dawes, 2001). Fruit that have reached physiological maturity (i.e. will ripen after harvest) may not be commercially acceptable because of poor taste (low dry matter/oil content), lack of flavour, uneven ripening (within a fruit), and highly variable ripening between fruit of the same lot (‘checkerboarding’). Overmature fruit may have off-flavours, tend to have more rots, and generally have shorter storage potential. The main harvest maturity index used in most countries is dry matter (or its inverse – water content, as is used in South Africa), which is highly correlated with oil content (Lee et al., 1983). Other measures of early maturity may include changes in skin colour (emerald green colour), loss of skin glossiness, or a brown seed coat. Minimum dry matter content required ranges from 17 to 25%, depending on cultivar and country. In California, the minimum dry matter percentages at harvest for the major cultivars are: ‘Bacon’ (17.7%), ‘Fuerte’ (19.0%), ‘Gwen’ (24.2%),

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‘Hass’ (20.8%), ‘Pinkerton’ (21.6%), ‘Reed’ (18.7%) and ‘Zutano’ (18.7%). In California, fruit are also released onto the market at predetermined dates based on dry matter and size for each cultivar. For example, the size/release dates for ‘Hass’ are: size 40 and greater, November 28; size 48, December 12; size 60, January 2; and size 70 or smaller, January 16. Based on the experiences obtained in Mexico for export fruit, it can be established that avocados should have an average of 22% of dry matter, and the lowest value of a sample should not be under 20%. The California regulation defined the minimum maturity of avocado fruit as containing 21% dry matter content. In 1983, dry matter content became an index of maturity for the California avocado industry, and this has been followed by the Mexican avocado growers (Kurlaender, 1996). Although most countries use a minimum dry matter of around 21% (probably following California standards for market access reasons), a higher minimum dry matter concentration of 24 to 25% (as used in New Zealand) generally results in a higher quality product. Florida (West Indian) avocados have lower oil content (3 to 15% oil) and are generally harvested at a specified calendar date (days after full bloom) and weight or size (Ahmed and Barmore, 1980). Recent interest in possible revision of commercial standards has led to some sensory and consumer studies. Arpaia (2003) examined responses from a smaller number of panellists repeatedly over a season using a hedonic scale, with ‘Hass’. The dry matter concentration at which the panellists ‘liked slightly’ was ~23%. In an Australian study (with over 100 consumers), consumer preference (likelihood of purchase) increased with increasing dry matter concentrations (and continued to increase even above 30% dry matter; Gamble et al., 2010). Significantly, a concentration of more than 26% was needed to achieve a rating of ‘Probably will buy’ (70 to 89% chance of purchase). Dry matter (DM) measurement is simple in principle: remove a sample of flesh from the fruit, weigh it, then dry to a constant weight, and re-weigh. However, the large spatial variation in dry matter in avocado fruit (Schroeder, 1985; Woolf et al., 2003) means that the way in which the tissue is sampled can have a significant effect on the resulting dry matter value and its repeatability. Countries have developed their own protocols for DM assessment: e.g. South Africa: Swarts (1978); California: Lee and Coggins (1982); Australia: Brown and Trout (1986); and New Zealand: Woolf et al. (2003); Pak et al. (2003). The range of flesh sampling strategies include sampling from opposing eighths cut longitudinally (Arpaia et al., 2001); opposing quarters cut longitudinally (Brown and Trout, 1986); one longitudinal quarter (Pak et al., 2003); or equatorial samples from the Hofshi coring system (Arpaia et al., 2001). A recent development, the Hofshi coring machine removes equatorial flesh samples (‘cores’ or ‘plugs’) of 15.8 mm diameter, and is increasingly being used around the world because it gives statistically similar results to the more traditional ‘opposing eighths’ method, yet it is faster, safer, less cumbersome, and less prone to sampling-induced variation from DM gradients in the fruit (Arpaia et al., 2001; Woolf et al., 2003). Various methods are used to dry the flesh tissue – ovens, dehydrators, or microwaves, the key being to achieve a constant dry weight, without burning the

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sample, e.g. using a temperature of 60 to 65°C (Woolf et al., 2003), although some use higher temperatures (100°C; Brown and Trout, 1986). Non-destructive measurement of dry matter would have a range of potential benefits. NIR (Near Infra Red) spectroscopy is the technology that is the closest to successful commercialization. In the packinghouse, NIR could be used to grade fruit into dry matter categories, which might be sold to different markets depending on taste, or more likely, shipped to different markets. Clark et al. (2003) showed that transmittance NIR could be used to predict dry matter of avocados; they have developed a model that predicted dry matter with at least 90% accuracy. Alternatively, hand-held NIR ‘guns’ could be used in the orchard to measure large numbers of fruit non-destructively and rapidly (for monitoring of dry matter trends and/or clearance to harvest (Brown and Sarig, 1994)). For some countries, late-season production is a potential market. However, for late-season fruit, dry matter and oil are not reliable indicators of maturity (Hofman et al., 2000), and indeed these reach a plateau for a number of months. Burdon et al. (2007) examined changes in late-season fruit (>32% dry matter) measuring dry matter, soluble solids content (SSC), starch, and individual sugars (perseitol, mannoheptulose, sucrose, fructose and glucose). However, few consistent trends were found over the two seasons. 8.3.2 Taste As previously noted, avocado is an atypical fruit in that it has a smooth, buttery consistency and a rich flavour. The sensory quality of an avocado should be judged when the fruit is eaten ripe. Flavour, aftertaste, odour, texture and flesh colour are all key quality attributes that have an impact on the overall acceptability. These attributes are dependent on many factors such as cultivar, maturity/oil content, flesh firmness at the point of consumption, and fruit size. The most important factor influencing acceptability is the oil content, which correlates strongly with fruit maturity, as measured by dry matter. Several studies have investigated the relationship between maturity and overall taste acceptability; however, many researchers have commented on the variability within and between fruit picked at the same time (Lewis, 1978). Harding (1954) assessed fruit (‘Hass’) for flavour and taste; these attributes were not assessed individually but grouped together in four distinct categories. Common flavour descriptors were green, nutty and grassy bitter; texture descriptors: rubbery, soft and buttery. An ‘unpleasant aftertaste’ was also detected. The bitter flavour is a characteristic of immature avocado flesh, in many cases leaving a distinctive aftertaste on the palate. In some varieties (‘Hass’, ‘Fuerte’ and ‘Sharwil’) this flavour is undetectable in mature, ripened flesh. Brown (1972) found an association between the presence of ten C17 olefinic and acetylenic oxygenated aliphatic compounds with the ‘unpleasant bitter-type flavour’. Lewis et al. (1979) examined ‘Hass’ fruit for colour, texture, flavour and general acceptability, although no descriptors were used. Flavour was found to be the most important attribute affecting acceptability, with acceptability ratings increasing as fruit matured. Later, Lee et al. (1983) examined avocados, of

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which ‘Hass’ was one, for two flavour descriptors (nutty and green) and texture (watery to creamy) and found that taste scores increased as fruit matured. In the literature, the effect of fruit maturity on taste acceptability has been examined, yet taste acceptability has not been explicitly described using sensory descriptors. The sensory team at Plant & Food Research (formerly HortResearch, New Zealand) used a trained sensory panel to develop the following sensory descriptors of ‘Hass’ avocados with the reference standards (Table 8.6; Walker,

Table 8.6 Sensory descriptive terms and reference standards developed for ‘Hass’ avocados, New Zealand Sensory attribute

Definition

Odour Green odour

Green/Vegetative odour

Hay odour Nutty odour

Flavour Woody pine flavour Canned pea flavour Savoury taste Bitter taste

Floral flavour Banana flavour Citrus flavour Texture Firmness

Oil release

Reference standard (intensity on 150-mm line scale)

Liquor from Watties® canned green beans Intensity = 135 Dried grassy odour Dried marjoram Intensity = 135 Nutty odour of crushed macadamia Crushed macadamia nuts nuts present when the avocado pulp Intensity = 90 is pressed with the back of a spoon Flavour characteristic of pine nuts/ oaky Chardonnay

Crushed pine nuts Intensity = 120

Cooked green pea flavour characteristic of canned peas Savoury taste similar to that from shellfish or broth Bitter taste similar to that occurring in vegetables such as overly mature broccoli Characteristic of fresh flowers Characteristic of fresh bananas Characteristic of fresh citrus fruit

‘Hartleys’ mushy peas (canned) Intensity = 135 MSG 2 g L−1 Intensity = 120 Caffeine 0.2 g L−1 Intensity = 75

The force required to compress the sample between the back teeth

‘Mainland’ Edam 1.5 cm3 Intensity = 150 ‘Philadelphia’ Cream Cheese 1.5 cm3. Intensity = 60 ‘John West’ Tuna chunks in oil. Intensity = 135

Amount of oil released from the sample when pushed against the roof of the mouth with the tongue

(Absent/present) (Absent/present) (Absent/present)

(Continued)

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Table 8.6

continued

Sensory attribute

Definition

Reference standard (intensity on 150-mm line scale)

Water release

Amount of water released from the sample when pushed against the roof of the mouth with the tongue Rate at which the sample breaks down when chewed with the back teeth

Surimi 1.5 cm3 Intensity = 75

Rate of breakdown

Fibrousness Particles

Presence of fibres detected during chewing with the back teeth Flesh breaks down into particulate mass when chewed

‘Philadelphia’ Cream Cheese 1.5 cm3 Intensity = 35 Spreadable ‘Philadelphia’ Cream Cheese 1.5 cm3 Intensity = 130 ‘Hartleys’ canned rhubarb Intensity = 120 (Absent/present)

Source: Walker, White, Harker, and Woolf, unpublished data.

White, Harker, and Woolf, unpublished data). The following attributes: ‘hay/dried grass’, ‘green’ and ‘nutty’ odours, ‘woody/pine’, ‘savoury’ and ‘canned pea’ flavours, ‘bitter’ taste and the texture terms ‘oil release’, ‘water release’ and ‘fibrousness’ were assessed on line scales having anchors at 0 = absent and 150 = extreme. The attributes ‘firmness’ and ‘rate of breakdown’ were assessed on line scales having anchors at 0 = soft and 150 = firm, and at 0 = slow and 150 = melts quickly, respectively. Four minor attributes were assessed by indication of presence or absence: ‘floral’, ‘banana’ and ‘citrus’ flavours and the texture term ‘particle breakdown’.

8.4

Preharvest factors affecting postharvest fruit quality

8.4.1 Mineral nutrition Thorp et al. (1997) surveyed mineral content in ‘Hass’ and found a range for average fruit mineral concentrations of: Ca, 25 to 47 mg 100 g−1 dry weight (DW); Mg, 91 to 113 mg 100 g−1 DW; and K, 1126 to 1608 mg 100 g−1 DW. Others have also noted the wide variation in levels such as calcium, magnesium, potassium, boron and zinc concentrations between trees (Marques et al., 2006). Calcium appears to be the most significant mineral in terms of fruit quality with impacts on rots and ripening. Higher Ca concentrations led to reduced rots (Hofman et al., 2002) and reduced storage disorders such as vascular browning and mesocarp discolouration (Thorp et al., 1997; Hofman et al., 2002; Marques et al., 2006). Hofman et al. (2002) also noted an interaction between calcium and magnesium (Mg) concentrations and the (Ca + Mg)/potassium ratio with negative correlations observed between these minerals and rots, storage disorders and days to ripen (Hofman et al., 2002). Everett et al. (2007; 2008) found that application of calcium lead to reduced postharvest rots.

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Negative correlations were observed between fruit potassium and phosphorus and time to ripen (Hofman et al., 2002). Potassium and magnesium (and calcium) were found to impact on body rot severity, percentage dry matter and fruit weight (Marques et al., 2006). There are recent reports of the possible beneficial effects of silicon on rots, either as a pre-harvest application, or as a postharvest dip (Bertling et al., 2009). 8.4.2 Rootstock The large differences between adjacent trees and the seedling origin of rootstocks led Hofman et al. (2002) to propose that rootstocks might be a significant contributing factor to fruit quality. Work was therefore carried out using clonal ‘Velvick’ (CV) or clonal ‘Duke 7’ (CD) rootstocks for ‘Hass’ that examined fruit quality and mineral concentrations for non-stored or stored fruit (Marques et al., 2003). CV had lower severity of body rots for both non-stored and stored fruit than CD (20 vs 38%). CV also led to lower diffuse discolouration and vascular browning than CD. Interestingly, CV fruit had ~15 to 20% more flesh calcium and boron, and lower nitrogen concentrations. They concluded that rootstock can influence fruit quality, and that mineral concentrations have a role. However, in New Zealand, no significant effect of cultivar (‘Fuerte’, ‘Zutano’, ‘Vista’, ‘Reed’, or ‘Hayes’, ‘Hopkins’) was observed over a 2-year period (Dixon et al., 2007). 8.4.3 Sun exposure It has been reported that exposure of the avocado fruit to direct sunlight can result in temperatures in excess of 15°C above the ambient air temperature (Woolf et al., 1999), as has also been observed in other crops such as apple (Ferguson et al., 1998). Indeed, we have observed temperatures of over 30°C even in mid-winter with air temperatures of 12°C where incident radiation is at its lowest, and skin temperatures as high as 52°C in mid-summer (Woolf, unpublished data). Fruit exposed to such temperatures have a wide range of differences in postharvest responses including reduced chilling injury (0°C storage) on exposed sides of the fruit, higher tolerance to 50°C hot water treatment, slower ripening of the whole fruit (including higher fruit firmness on the exposed side of the fruit (Woolf et al., 1999)). Thus, it appears that preharvest temperature experienced by avocado fruit affects their postharvest behaviour in manners similar to postharvest heat treatments (Woolf et al., 1999). This work was verified in a completely different growing environment (Israel) with five cultivars (Woolf et al., 2000). High preharvest temperatures due to exposure to the sun dramatically affected a range of postharvest responses in ‘Ettinger’, ‘Fuerte’, ‘Hass’, ‘Horshim’ and ‘Pinkerton’. Along with verifying the results obtained in New Zealand, the shaded fruit were found to exhibit more extensive and faster development of inoculated Colletotrichum gloeosporioides than the sun-exposed fruit. Both works showed

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accumulation of RNA, which encodes for heat shock proteins (hsps) and their proteins (as determined by western and radio-labelled protein synthesis analyses), which showed patterns of accumulation concomitant with thermotolerance. Thus, sun exposure and its resulting temperatures are likely be responsible for the variability observed in many postharvest responses and should be considered in sampling of fruit for both experimental trials, and commercially.

8.5

Postharvest handling factors affecting fruit quality

Coursey (1971) reported that postharvest losses of avocado were estimated to be 43%, and smooth-skinned varieties were more prone to physical injuries during handling and transport than the rough skinned varieties. Some of the most important causes of postharvest losses in avocado include mechanical damage, physiological disorders (especially chilling injury: CI), decay, and insects. Avocado is a subtropical fruit sensitive to CI (Pesis et al., 1994). The main symptoms are black stains in the epidermis and a grey or brown discolouration in the mesocarp. Morris (1982) reported another symptom as alteration of internal metabolism, which leads to an increase in anaerobic respiration and, as a consequence of abnormal metabolites, results in the development of a foul taste and odour. Anthracnose (commonly caused by Colletotrichum gloeosporioides) is the most important disease in avocado that reduces fruit quality after harvest. Friction damage, which is characterized by an oxidation of the tissue that later inclines downward and becomes necrotic, is one of the most frequent problems during fruit harvest and handling. A cut to the skin breaks the protective layer of the fruit completely, accelerates water loss, and exposes the tissue directly to the environment. Damage is typically more serious where there are inadequate packaging processes. 8.5.1 Temperature management Temperatures above 30°C generally cause adverse effects on avocado quality and ripening (Erickson and Takaake, 1964; Zauberman et al., 1977). From 10 to 25°C, the avocado fruit commonly softens faster as holding temperature increases. From 5 to 8°C (typical storage temperatures for most cultivars), softening is usually controlled, but ripening will occur in a shorter and less variable manner when fruit are transferred to higher temperatures. For most cultivars, external chilling injury (discrete skin discolouration) (Plate XIII: see colour section between pages 244 and 245) occurs at between 0 and 4°C, depending on cultivar, maturity and ripeness. When fruit are ripe, or near-ripe (soft), they can be stored at lower temperatures without external chilling injury (Young and Kosiyachinda, 1976). Freezing of fruit occurs at ~1.5°C (White et al., 2009), but of course exposure time is an additional factor. Temperature is no doubt the single most important factor in fruit storage and quality of avocados, as it is the case for other fruits. All biological processes are controlled by temperature, including ripening, and fruit quality from both

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physiological and pathological perspectives. The rate of ripening depends on temperature of storage (Eaks, 1978). The response of avocado to storage temperatures varies according to fruit type (race), variety, growing conditions, time in the season (stage of maturity) and stage of ripeness. Of course, there are also many postharvest treatments that can influence the fruit’s physiological response to temperature, such as 1-MCP (primarily influencing ripening) and temperature treatments (e.g. heat treatments or low temperature conditioning, which influence physiological responses to low temperature). In terms of genetic influence on storage responses, Guatemalan and Mexican cultivars are generally stored at 4 to 8°C, while West Indian cultivars are more sensitive to low temperatures and are stored at temperatures similar to those for most tropical fruits (~13°C; Hatton et al., 1965; Zauberman et al., 1973). The most significant commercial cultivars (e.g. ‘Hass’ and ‘Fuerte’) are generally stored at ~5 to 7°C. In terms of storage duration, avocados are generally in the short to medium category compared with other fruits, with a successful storage time of two to four weeks for most cultivars. For the main commercially traded cultivars, three to four weeks of storage should be achievable, but longer times are more challenging because of either expression of physiological and/or pathological disorders. For ‘Hass’, it remains a challenge to achieve good fruit quality reliably after six weeks. However, there are reports of successful storage times of 12 weeks for ‘Hass’ and eight weeks for ‘Fuerte’ using a combination of prochloraz, fungicide, waxing, SmartFreshSM treatment followed by controlled atmosphere (CA) storage (Lemmer et al., 2006). 8.5.2 Physical damage While avocado are generally robust fruit, physical damage to the skin during harvest, cleaning and packing can have significant negative fruit quality effects, both cosmetically and from a pathology perspective (Fig. 8.2). Although some avocados are ‘smooth-skinned’, many exhibit raised bumps on the skin, most (but not all) of which contain a lenticel at the top. These are particularly prone to physical damage. Everett et al. (2008a) showed that physical damage to the lenticels (due to fruit-to-fruit damage) was influenced significantly by the turgidity of the cells in the lenticels. Thus, harvesting immediately after rainfall is likely to increase damage, and probably rots in storage. This may explain the results of Elmsley et al. (2007), who observed that, although time of harvest in the day generally had relatively little effect on fruit quality, there was a slight reduction in body rots in fruit harvested in the afternoon compared with early morning. While there may or may not be significant pathological implications to damage to the lenticels, any damage to the skin is generally not desirable, and should be avoided where possible. Even if rots are not an issue, clearly there are at least commercial implications in terms of appearance of the fruit, both at importer and/or wholesaler points in the supply chain, and of course for the consumer. This issue is even more important for green-skinned fruit, since the colouring of darker skin (such as ‘Hass’) disguises minor skin defects.

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Fig. 8.2

Bruising injury. Image courtesy of Plant and Food Research, New Zealand.

8.5.3 Water loss As for most crops, weight loss is a significant commercial factor since, at the very least, it can be seen as ‘very expensive water’. Recommendations of a relatively high relative humidity during storage (85 to 95%) and common use of wax coatings are aimed at reducing weight loss. Weight loss between harvest and storage has been found to be a significant issue in terms of storage (Yearsley et al., 2002; Dixon et al., 2005), and thus it was recommended that time taken to pack the fruit should be minimized. Generally weight loss is an issue that should be considered as something to minimize. However, there are points of balance that need to be considered. Firstly, most treatments that significantly reduce weight loss (e.g. modified atmosphere (MA) bags of various sorts) often lead to excessive rots. Also, some weight loss is important in promoting the ripening of avocado; indeed weight loss has been considered as a possible ripening trigger (Dixon et al., 2003). For example, we found that storing fruit in a 100% RH environment (which led to negligible weight loss) resulted in very significant delays in ripening, and thus subsequent expression of rots (White, Burdon and Woolf, unpublished data). 8.5.4 Atmosphere Optimum modified atmospheres (MA) and controlled atmospheres (CA) (2 to 5% O2 and 3 to 10% CO2) delay softening and skin colour changes and reduce

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respiration, ethylene production rates, and CI of avocado fruit (Yahia, 1998). CA delays the softening process, and thus maintains the resistance of the fruit to fungal development (Spalding and Reeder, 1975). There is also a range of other CO2/O2 manipulations that have physiological effects, and extensions to regular CA storage such as ‘dynamic CA’ that are now receiving attention. Controlled atmosphere (CA) storage Low O2 injury may appear as irregular brown to dark brown patches on the skin and may additionally cause diffuse browning of flesh beneath affected skin (Yahia, 1997a; Carrillo-López and Yahia, 1991; El-Mir et al., 2001; Loulakakis et al., 2006; Yahia and Rivera, 1994), and can be expressed as browning at the stem-end of the fruit (Yearsley and Lallu, 2001), a ‘chocolate dipped’ appearance. Carbon dioxide atmospheres above 10% can be detrimental, leading to discoloration of the skin and development of off-flavours, particularly when the O2 concentration is less than 1%. Very early research by Overholser (1928) reported that the storage life of ‘Fuerte’ avocados was prolonged for 1 month when fruit were held in an atmosphere of 4 to 5% O2 and 4 to 5% CO2 at 7.5°C, compared with air storage. Brooks et al. (1936) reported that fruit could be held in atmospheres containing 20 to 50% CO2 at 5 to 7.5°C for two days without causing any injury. Atmospheres with CO2 concentrations below 3% prolonged the storage life of Florida avocados at all temperatures, and reduced the development of brown discolouration of the skin (Stahl and Cain, 1940). Extensive work was later done also with ‘Fuerte’ avocado, and concluded that the time for the fruit to reach the climacteric was extended in proportion to the decrease in O2 concentration from 21 to 2.5% (Biale, 1942; 1946). In later years, Young et al. (1962) demonstrated that the delay of the climacteric could also be achieved by 10% CO2 in air, and the combination of low O2 and high CO2 further suppressed the intensity of fruit respiration. Hatton and Reeder (1965; 1969; 1972) and Spalding and Reeder (1972; 1974) found that a CA of 2% O2 and 10% CO2 at 7.5°C doubled the storage life of the cultivars ‘Lula’, ‘Fuch’ and ‘Booth 8’. Mature-green ‘Hass’ avocado can be kept at 5 to 7°C in 2% O2 and 3 to 5% CO2 for nine weeks, then will ripen in air at 20°C to good quality. Elevated (>10%) CO2 concentrations may increase skin and flesh discolouration and offflavour development, especially when O2 is six weeks) at standard storage temperatures. Skin pitting, scalding, and blackening are the main external CI symptoms on mature-green avocado kept at 0 to 2°C for more than seven days before transfer to ripening temperatures. External CI occurs as irregular patches of blackening on the skin and can be observed during storage, but generally increases slightly in intensity after removal from cold storage (White et al., 2009). The damage is first seen in inner cell layers of the exocarp and then the outer layers of the skin (Woolf, 1997). In cultivars that naturally darken during ripening, such as ‘Hass’, the damage will be less apparent after ripening, but may be discriminated as brown, corky skin tissue in ripe fruit. External CI is generally induced by temperatures

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lower than 3°C, but fruit become less sensitive with increasing maturity, and ripe fruit are less affected. Fruit exposed to low temperatures may be of poor internal quality when ripe, with a high incidence of rots and softening disorders (Woolf et al., 1995), but will have lower incidence of internal CI (greying). 1-MCP does not reduce external chilling injury (Woolf et al., 2004). For ‘Hass’ fruit stored for long periods at standard storage temperatures (six to seven weeks at about 6°C), a form of external CI is expressed that is of a very similar appearance to that observed at low temperature, which can sometimes be seen in fruit that are quite soft (nearly ripe) at the point of removal from storage.

8.7

Pathological disorders

Postharvest rots (or ‘ripe rots’) (Fig. 8.3) are one of the key problems of avocado in most growing regions/countries with the exception of very dry environments such as Chile, Peru and California. 8.7.1 Epidemiology In order to minimize postharvest diseases of avocados an integrated disease management programme needs to be implemented. Both pre-harvest and postharvest protocols and procedures are important for their control. A basic

Fig. 8.3

Severe stem end rots and associated severe vascular browning. Image courtesy of Plant and Food Research, New Zealand.

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understanding of the infection processes and the periods of highest risk for infection to take place are required so as to achieve best control. The most important postharvest decays of avocados are caused by the fungi C. gloeosporides, which causes anthracnose or black spot decay, and Diplodia natalensis. Also important are Phomopsis spp. and Dothiorella spp. which cause stem-end rot (Ahmed and Barmore, 1980). Diseases of avocados are divided into two categories based on their location (Snowdon, 1990). Stem-end rots (Fig. 8.3) enter the fruit at the stem, or peduncle end of the fruit and move down the fruit resulting in discoloured flesh, often with associated browning of the vascular strands (Johnson and Kotze, 1994), which often extend well beyond the disease margin of the flesh. Body rots invade through the skin and generally manifest as circular brown to black spots that may be covered with spore masses in the later stages of infection. Decay penetrates through the flesh, resulting in discrete areas of discoloured flesh. In cultivars that darken when ripe (such as ‘Hass’), rots may be less obvious externally (unless they are sporulating). The most prevalent fungi responsible for postharvest diseases of avocado fruit are Colletotrichum acutatum, C. gloeosporioides, Botryosphaeria parva, B. dothidea and Phomopsis (Hartill, 1991). Apart from Phomopsis, which is almost exclusively isolated from stem-end rots, these fungi can cause both stem-end rots and anthracnose (a disease usually characterized by necrotic lesions on the body of the fruit) on ‘Hass’ avocados. Botryosphaeria spp. is generally isolated in greater numbers from rots of avocados than are any of the other fungi. Everett and Pak (2001) found that Colletotrichum acutatum was more often associated with stem rots, and Botryosphaeria parva with body rots, but also that there were significant regional and seasonal differences. Infection with C. gloeosporides occurs while the fruit is developing on the tree. Fruit spot disease caused by C. gloeosporioides is the most commonly occurring disease of avocado. Infection of avocado fruits by Fusarium solani and F. sambucinum causes accelerated softening of fruits. Other diseases of avocados are cercospora spot (Cercospora purpurea) and scab (Sphaceloma perseae), which attack leaves as well as fruits (Kadam and Salunkhe, 1995). Anthracnose, caused by Glomerella cingulata, of which the conidial state is Colletotrichum gloeosporioides, is found in the USA, Israel (Prusky et al., 1983), Argentina (Oste and Ramallo, 1974), Australia (Peterson and Inch, 1980), New Zealand (Hartill, 1991), India, South Africa (Rowell, 1983) and Puerto Rico (Nolla, 1926). Infection studies have identified Colletotrichum gloeosporioides as a weak pathogen. Anthracnose appears as the fruit begins to soften as circular black spots covered with pinkish spore masses in later stages. Decay can penetrate through the flesh and induce browning and rancid flavour. Infection is enhanced by wounding, artificially and by the fruitspotting bug (Fitzell, 1987). On the tree during the season, spores of this fungus have been shown to germinate, form an appressoria and a short infection peg that penetrates about 1.5 μm into the skin (Coates et al., 1993). The fungus then remains quiescent until harvest, when antifungal dienes in the skin of avocado fruit break down because of degradation by lipoxygenase activity (Karni et al., 1989; Prusky et al., 1988). The fungus then resumes growth and invades the avocado fruit to

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cause postharvest rots (Prusky et al. 1982; 1983; 1984; 1988; 1990; 1991; Adikaram et al., 1992; Neeman et al., 1970). Breakdown of the antifungal dienes was delayed by CO2 (Prusky et al., 1991), hypobaric pressure (Prusky et al., 1984) and by treatment with antioxidants (Prusky et al., 1995). Cercospora spot of avocados, caused by Pseudocercospora purpurea, causes spots on fruit, which at first form small greenish-white dots that expand into slightly sunken irregular brown blotches. Mature lesions are rarely larger than 0.5 cm, but the cracks and lesions formed provide entry for other fungi, particularly anthracnose (Snowdon, 1990). This disease is found in Brazil (Albuquerque, 1962), South Africa (Darvas, 1982), Cameroon (Gaillard, 1971), Japan (Hino and Tokeshi, 1976), Mexico (Fucikovsky and Luna, 1987) and USA (Nagy and Shaw, 1980). Up to 69% of preharvest fruit loss on some orchards in South Africa has been attributed to infection with this fungus (Darvas and Kotze, 1987). Dothiorella rot, caused by Botryosphaeria ribis, of which the conidial state is Dothiorella gregaria is found in Israel, South Africa (Labuschagne and Rowell, 1983), the USA (Stevens and Piper, 1941), and parts of South America (Zentmyer, 1961). In New Zealand this disease is caused by Botryosphaeria parva (Hartill et al., 1986) or Botryosphaeria dothidea (Hartill, 1991) and in Australia by Dothiorella aromatica (Muirhead et al., 1982). This disease can invade avocados through the body of the fruit or through the cut stem end (Snowdon, 1990). Symptoms usually only appear as fruit begin to soften after harvest, although this fungus has been isolated from lesions on hard unripe Californian avocados (Snowdon, 1990). Stem-end rot is generally caused by Botryodiplodia theobromae in Australia (Peterson, 1978), South Africa (Darvas et al., 1987), the Ivory Coast (Frossard, 1964) and the USA (Stevens and Piper, 1941). Dothiorella spp., Phomopsis perseae (Peterson, 1978) and Thyronectria pseudotrichia (Darvas et al., 1987) have also been implicated in stem-end rots. Dothiorella spp. and Phomopsis spp. can cause latent infection in developing fruit (Peterson, 1978). However, Botryodiplodia is a wound parasite, and most infections with this fungus probably take place at harvest. In New Zealand, Botryosphaeria dothidea, B. parva, Colletotrichum gloeosporioides, C. acutatum and Phompsis spp. have all been associated with stem-end rot (Hartill, 1991). This appears as dark brown to black discolouration, which begins at the stem and advances toward the blossom end, finally covering the entire fruit. Dothiorella gregaria is another cause of stem-end rot in ripe avocados. Scab, caused by Spaceloma perseae, affects young developing fruit. Raised corky brown spots are produced on the skin, which mar the cosmetic appearance of the fruit. Wound pathogens can gain entry to the fruit through lesions caused by this fungus (Ramallo, 1969). Scab occurs in North, Central and South America, in the West Indies (Jenkins, 1934), and in South Africa and the Philippines (Snowdon, 1990). Some other fungi that can cause postharvest diseases of avocado worldwide, but are rare in occurrence and are not perceived to be important include Alternaria sp. in Israel (Zauberman et al., 1975); Penicillium expansum in the USA and the West Indies (Horne, 1934; Wardlaw, 1934); Fusarium spp. in Israel (Zauberman and Schiffmann-Nadel, 1979); South Africa (Darvas and Kotze, 1987); the USA (Horne, 1934) and the West Indies (Wardlaw, 1934); Pestalotiopsis versicolor in

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South Africa (Darvas and Kotze, 1987); Phytophthora citricola which attacks fruit near the ground in Mexico (Fucikovsky and Luna, 1987) and the USA (Koike et al., 1987); Trichothecium roseum in the USA (Horne, 1934); and Rhizopus stolonifer in South Africa, the USA and Israel (Darvas and Kotze, 1987; Zentmyer et al., 1965). In New Zealand species of Fusarium have also been isolated from anthracnose (Hartill, 1991). In New Zealand Colletotrichum acutatum has been isolated from both stem-end rots and anthracnose of ‘Hass’ avocados (Hartill, 1991). Colletotrichum acutatum spores released from infected dead twigs and fruit in the canopy, or possibly on the orchard floor, seem to infect avocado fruit while hanging in the tree. Most infections are probably initiated from within the avocado tree, the influence of shelter-belt infections does not seem to be important, and timing of infection appears to be random throughout the year (Everett, 1994). C. acutatum may be a wound pathogen, as only a few fruit became infected when unwounded fruit were artificially inoculated throughout the season in the orchard. Damage caused by grading equipment was insufficient to aid infection. Avocado blight, caused by Sphaceloma perseae (Myriangiales: Elsinoeaceae), found in Michoacán (Mexico), Florida, Puerto Rico, Brazil, Africa, Peru, Cuba, Haiti and California, attacks the fruit (in all stages), leaves, and young branches. The affected fruit present brown lesions of corky aspect with round or irregular shapes at first. When these lesions grow, they can cover a large part of the fruit or the whole fruit, and cause fissuring in leaves and branches. In the fruit, the damages are exclusive of the exocarp, while the rest of the fruit remains healthy. However, the lesions can be an entry point for other organisms (Gallegos, 1983). The S. perseae fungus requires a high relative humidity and high temperatures for its proper development. The most susceptible stage of the fruit is when it reaches a third or a half its normal size. Damage to the fruit caused by insects, rodents or mechanically, allows the entrance of the disease, which produces spores on the attacked tissue. Among all the cultivars grown in Mexico, ‘Fuerte’ is the most susceptible to this disease. ‘Hass’ can also be severely affected if the fungus is not prevented. ‘Booth 1’, ‘Pollock’, and ‘Waldin’ are considered slightly susceptible. The Mexican local hybrids (Criollos) are also likely to be affected by the fungus, although the incidence is lower because fruit from these trees ripens in the spring (Gallegos, 1983). 8.7.2 Preharvest control Preharvest control methods for postharvest fungal decay include good orchard sanitation (removal of mummified fruit and dead wood; Everett et al., 2007a) and effective preharvest application of a fungicide such as copper, which is widely used in some countries where humid growing conditions prevail. Although the effects may not be strong, there is some indication that more open canopy (better airflow) might reduce rots (Everett et al., 2007a; 2008b). Most researchers working in humid growing environments find significant interorchard differences, particularly in terms of rots. Often one finds that in a group of three to five orchards, one or two orchards will show significantly higher rot incidence (Adkins et al., 2005; Burdon and Lallu, 2009). This suggests firstly that

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there are good orchard practices that should be understood and more widely applied, and secondly that for markets that require a long storage time, low-rot orchards should be selected. Likewise, using fruit too early or late in the season is also going to increase the risk of a poor out-turn after prolonged storage (Dixon et al., 2003). Preharvest sprays with copper have been shown to significantly reduce postharvest diseases (Hartill et al., 1990a). Everett and Pak (2001) correlated the number of copper fungicide applications/season and showed a significant relationship to body rots (r2 = 0.81). Four sprays during the season were insufficient to reduce postharvest rots, and twelve sprays were required before significant differences were obtained. Preharvest copper alternatives Benlate application has been shown to reduce disease significantly when three sprays were applied during the season (Hartill et al., 1990b). Everett et al. (2007b) examined a range of treatments for fruit stored for four weeks. Boscalid, Pristine® (boscalid/ pyraclosrobin), and fluazinam were found to give better control than the unsprayed control, and were comparable to two copper sprays (Kocide® Opti and Camp™ DP (copper hydroxide formulations). Everett et al. (2008b) reported that phosphoric acid trunk injections reduced postharvest rots (both body and stem end rots). Development of prediction models in the orchard for calculation of periods of infection risk is a valuable tool to enable growers to target spray applications more effectively and thus reduce costs, and also reduce the risk of resistance to chemicals (Everett et al., 2003). Understanding of temperature effects on spore germination (as carried out by Everett and Pak, 2002) may provide useful information to incorporate into such models. 8.7.3 Postharvest control Postharvest handling, especially temperature and ripening control should be optimized. Sanitation in the packinghouse is necessary. Harvesting should not be carried out in the rain or when fruit are wet, and careful handling to minimize skin damage helps to reduce rots (Mandemaker et al., 2006). The most important postharvest factor for reducing rots is maintaining optimum temperature during handling, storage, transport, and ripening. It is also critical not to store fruit for long periods. Postharvest temperature control is effective in reducing the incidence of diseases (Truter and Eksteen, 1987a, 1987b; Young and Kosiyachinda, 1975; Fitzell and Muirhead, 1983). However, optimum temperatures are specific for different cultivars and in different regions. For example, New Zealand ‘Hass’ avocados stored under appropriate South African recommendations (‘Hass’ from KwaZulu/Natal) were affected by more rots than the standard New Zealand postharvest temperature regime (Hopkirk et al., 1994). Storage in 2% O2 and 5% CO2 extended the effective storage of ‘Hass’ avocados to four weeks, but rots were severe (Hopkirk et al., 1994). High concentrations of CO2 (10%) were reported to prevent development of anthracnose for three to four weeks in ‘Fuchs’ and ‘Waldin’ fruit stored at 7.2°C in Florida (Spalding and Reeder, 1975),

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but such treatments don’t appear to be effective in New Zealand (White and Hopkirk, unpublished data). As noted previously, ripening fruit at lower temperatures (15 to 20°C) can lead to significant reduction in rots compared with higher temperatures (Hopkirk et al., 1994). Although ripening at 15°C has been found to be a robust and reliable regime, it is difficult to instigate commercially. Postharvest fungicides (prochloraz, benlate/benomyl and thiabendazole) are used in some countries, but these are not registered for use in the USA (Darvas et al., 1990). Use of prochloraz (Sportak®) is required for export to Australia from New Zealand and thus much research has been carried out into its efficacy. It can be applied either as a dip or spray, but New Zealand experience has lead to the recommendation of spray application rather than a dip, since build-up of spores in dipping tanks has been observed. Postharvest dipping with prochloraz can be unreliable. It appears that there may be a curing effect, or alternatively an infection period immediately after harvest that is not halted by a delayed application of prochloraz. Hartill et al. (1986) found no difference in rots if prochloraz was applied within 24 h of picking. Everett and Korsten (1996) have demonstrated the effectiveness of applying prochloraz either in wax or as an ultralow volume spray. Fruit treated with prochloraz cannot be exported to Asia, the USA and some countries in Europe. In the recent years a wide range of possible postharvest fungicide treatments have been examined in New Zealand. Although not registered, Thiabendazol (TBZ) and Pristine® (boscalid/pyraclosrobin) were applied and there were generally beneficial effects on body rots, and sometimes stem-end rots, but variation between orchards in efficacy (Everett et al., 2007a). For late season fruit (generally higher rot pressure), Mandemaker et al. (2007a) found no effective treatments among the following; Carbendazim, azoxystrobin, folpet, fatty acids (potassium salts), and benomyl. Work in New Zealand lead by Everett and in South Africa lead by Korsten has sought to develop biological control agents for postharvest rots. Examples include Seranade® Max (Bacillus subtilis QST 713), and Serratia marcescens HR42. As is often the case with biological control agents, lack of repeatable efficacy limits commercialization. Wax by itself also seemed to reduce incidence of stem-end rots; however, waxing has been reported to increase the incidence of all postharvest diseases on ‘Fuerte’ avocados (Darvas et al., 1990). Waxing probably increases the humidity next to the skin of the fruit, and also the production of ethylene, both can promote the growth of anthracnose fungi (Darvas et al., 1990; Flaishman et al., 1995). However, Darvas et al. (1990) have shown that wax extended the shelf life of ‘Fuerte’ avocados.

8.8

Insect pests and their control

Avocado trees growing in dry climates have relatively few insect pests. One that has become very significant lately is the avocado thrip (Scirtothrips perseae, Nakahara), which has recently moved into California. This resulted in significant losses of fruit due to feeding on the skin (Fig. 8.4), leading to fruit described as ‘avocado spuds’,

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Fig. 8.4 Extreme damage to avocado due to feeding of avocado thrips (Scirtothrips perseae, Nakahara). Image courtesy of Plant and Food Research, New Zealand.

since fruit can be completely devoid of green skin, thus resembling a potato. Perhaps surprisingly this does not significantly affect ripe-fruit quality. Other thrips may be a problem in other countries such as red-banded thrips (Selenothrips rubrocinctus) in Australia, and greenhouse thrips (Heliothrips haemorrhoidalis) in New Zealand. Leafroller caterpillars typically cause damage to the skin due to feeding of the larvae (caterpillars), often around the stem end of the fruit, or where leaves are touching fruit. Examples include: Ivy leafroller (Cryptoptila immersana, Walker) and avocado leafroller (Homona spargotis, Meyrick) in Australia; Amorbia (Amorbia cuneana), Orange tortrix (Argyrotaenia citrana) and Omnivorous looper (Sabulodes aegrotata) in California; and Greenheaded leafroller (Planotortrix octo) and Brownheaded leafroller (Ctenopseustis obliquana) in New Zealand. Fruit spotting bug can cause damage to fruit where ‘stings’ to the fruit lead to hard lumps or ‘stones’ in the flesh (of ripe fruit). Species include Amblypelta nitida and banana spotting bug (Amblypelta lutescens lutescens). A range of other insects may be pests, including mealybug, scale and various mites. 8.8.1 Preharvest control In order to establish a good strategy for integrated pest control, thresholds of economical damage need to be determined. These can help to reduce the frequency

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of preharvest sprays, lower the crop handling costs, increase production, and reduce the incidence of postharvest fumigation. In Mexico, only four pesticide products are recommended for chemical control: 1) parafinic petroleum oil; 2) Malathion CE 47; 3) Methylic parathion, and 4) Permetrine. In Chile, the presence of a large fauna of biological control agents has helped to contain potential avocado pests. However, there is no doubt that the use of pesticides in the orchards contributes to maintaining this situation. Different pests that sometimes need to be restrained can be handled with selective pesticides that do not interfere significantly with biological control agents (BCAs). In other cases, spraying specific sectors of the orchard will help to maintain the beneficial fauna. In the same way, the establishments of reservoirs for biological controllers, together with cultural practices such as the elimination of low branches, the removal of branches that constitute the origin of infections, and the maintenance of vegetation that feed beneficial fauna in the adult stage, are also biological control practices. Finally, the artificial introduction of biological controls through the development and release method can help where the beneficial fauna are not efficient enough or do not colonize the orchard in time (López-Laport, 1999).

8.8.2

Postharvest control

Methyl bromide Avocados grown in fruit fly-infested areas require quarantine treatments to be marketed in many countries. Methyl bromide (MeBr) treatment is an APHISapproved treatment for Mediterranean fruit fly, but can result in a significant reduction in fruit quality. Avocados are also commonly MeBr-fumigated at entry into countries for quarantine insects other than fruit fly. Avocado fruit treated with MeBr can exhibit some external damage, ripening two to four days earlier than non-fumigated controls. Pitting and other visual damage caused by fumigation is commonly masked in the case of cultivars with purple or black fruit when the fruit ripen and achieve a dark colour. The cultivars least damaged are those with purple or black skin. MeBr fumigation does not affect the flesh as much as the skin. Flesh colour and flavour are commonly acceptable in most cultivars, and the former is usually equal to that of controls in appearance. In certain cultivars, however, fumigated fruit commonly show more internal browning, with visibly affected vascular bundles throughout the flesh (Ito and Hamilton, 1980). Irradiation Extension of shelf life by gamma irradiation has been successful for some fruits, but appears to hold little prospect for avocado. Akaine and Goo (1971) found avocado fruit to show surface and internal damage at 5 Krad. At this dosage and lower, the climacteric respiration occurred earlier than that for controls, and so gave no storage advantage. Smith and Jansen (1983) found 2.5 Krad to be the maximum safe dosage, but without significant advantage from a postharvest perspective. Young (1965) studied the effect of gamma radiation on respiration,

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ethylene production and ripening of ‘Fuerte’ avocados, and reported that irradiation in the pre-climacteric phase at 5 and 10 Krads caused an immediate doubling of respiration and a small ethylene production, 100 Krads caused a doubling of respiration and small ethylene production, but severe injury and fruit did not ripen. Irradiation after the climacteric has been initiated or in the post-climacteric phase had no effect on ethylene production or respiration, nor was there any effect on the appearance or quality of the fruit. Doses in excess of 20 Krad seemed to cause brown discolouration to the mesocarp; 10 Krads resulted in extension of storage life of ‘Fuerte’ by ~five days at 20°C, but fruit irradiated at 50 Krads did not ripen, the tissue remained hard and turned brown (Nogalingam, 1993). Low-temperature or ‘cold’ disinfestation Use of low temperatures (generally 11 to 16 days at 60 days) of cold storage. It is characterized by the development of dark green necrotic lesions with a velvety appearance that affect only the uppermost part of the berries; eventually the lesions invade sub-epidermal tissues but never the mesocarp. Mycelial growth of C. cladosporioides and C. herbarum can be considerably arrested, but not totally inhibited, at 0 °C (Briceño and Latorre, 2008). Rhizopus rot Rhizopus rot (R. stolonifer, also known as R. nigricans) usually starts at the base of mature berries as a soft, very watery rot that partially or completely decays infected berries. Longitudinal fissures are produced, and a black mold develops along the fissures. The skin of the berry turns light gray. Infection is always associated with injured berries under warm weather conditions during harvest. Infection caused by R. stolonifer may be followed by sour rot organisms (yeasts or acetic acid bacteria). Rhizopus rot can be arrested totally if grapes are stored below 4 °C (Guerzoni and Marchetti, 1987; Latorre et al., 2002b). Aspergillus rot Aspergillus rot (A. carbonarius, A. niger) produces water-soaked brown lesions on wounded berries, followed by dark, black sporulation (conidia). It is primarily associated with warm weather conditions in the vineyard, and it can be arrested totally if grapes are rapidly cooled and kept below 4 °C. Aspergillus rot is often associated with sour rot organisms (yeasts or acetic acid bacteria) (Guerzoni and Marchetti, 1987; Kazi et al., 2008; Latorre et al., 2002b; Rooney-Latham et al., 2008). Other decay fungi Other filamentous fungi that have been reported to cause grape decay include Alternaria alternata, Botryodiplodia theobromae, Cladosporium sphaerospermum, Colletotrichum acutatum, C. gloeosporioides (Glomerella cingulata), Diplodia natalensis, Elsinöe ampelina, Guinardia bidwelli (= Greeneria uvicola), Melanconium fuligineum, Monilia fructicola, Pestalotiopsis menezesiana, P. uvicola, Phomopsis viticola, Pilidiella diplodiella (= Coniella diplodiella), Rhizopus arrhizus var. arrhizus (= R. oryzae) and Stemphyllium botryosum (Camili and Benato, 2005; Sawant et al., 2008; Sholberg et al., 2003; Steel et al.,

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2007; Visarathanonth et al., 1988; Xu et al., 1999). Additionally, some yeasts (e.g., Aureobasidium pullulans and Cryptococcus laurentii) and bacteria (e.g., Bacillus subtilis) have occasionally been associated with grape rot in California (Morgan and Michailides, 2004). Insect damage Several pests, insect and acari, can severely injure grapes in the vineyard, and their presence and the damage can reduce the quality and acceptability of grapes. Among other pests, grape berry moths (Lobesia botrana), mealybugs (Pseudococcus maritimus, P. viburni, P. longispinus, Planococcus ficus), western flower thrips (Frankliniella occidentalis), vinegar flies (Drosophila spp.) and yellow jackets (Vespula spp.) often injure grapes, facilitating the dissemination and penetration of fungal pathogens. The possible dissemination of some insects and acari on grapes has forced the introduction of specific quarantine treatments to lower the risk of introduction and establishment of new pests in some countries. 9.5.2 Abiotic agents Abiotic agents can cause considerable deterioration of grape quality and trade value. Therefore, farmers need to be aware of the main abiotic factors in order to preventively control them. The most frequent and important abiotic factors are discussed in this section. Bleaching Bleaching caused by SO2 is characterized by partial or total discoloration of the berry, affecting the anthocyanins and chlorophyll. Bleaching usually starts at the pedicel end because of injuries and weak insertion that allows the penetration of SO2 inside the berry base. Often, this syndrome is known as ‘sunken’. Experiments done under controlled SO2 concentrations classified cultivars’ susceptibility to SO2 as very susceptible (‘Ribier’, ‘Hongbaoshi’ and ‘Red Globe’), moderately susceptible (‘Niunai’), susceptible (‘Kyoho’ and ‘Muscat Hamburg’) and minimally susceptible (‘Longyan’ and ‘Black Autumn’) (Gao et al., 2003). The SO2-sensitive cultivar ‘Red Globe’ has a loose epicuticular wax structure and a low concentration of superoxide dismutase compared to the minimally susceptible cultivar ‘Longyan’ (Zhang et al., 2003). (See Plate XVI in the colour section between pages 274 and 275.) Dehydration Dehydration is a physical process where vapor moves from a high water potential stage to a low water potential stage (water pressure deficit, WPD, condition). Along the postharvest handling chain of grapes, a WPD is produced between the cluster and the atmosphere, which favors water loss. Threshold values of water loss of 4% for ‘Red Globe’, 3.6% for ‘Thompson Seedless’ and 3.3% for ‘Flame Seedless’ have caused rachis browning symptoms under controlled conditions

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(Crisosto et al., 2001). At harvest time, high temperature and low humidity are the main physical factors that promote WPD; however, when the fruit is packed into polyethylene bags, the humidity increases and WPD is reduced; and fruit temperature remains a critical factor. During storage, the time it takes for the cluster to achieve the chamber temperature should be considered as a critical factor to reduce WPD; therefore, forced air cooling has become a required practice in the table grape industry. The water loss rates of ‘Red Globe’ clusters following harvest in a commercial grape operation were 1.8% per day during harvest and transport to packaging, 1.33% per day during packaging, 1.09% per day during the wait for forced air cooling, 0.99% per day during forced air cooling and 0.0054% per day during storage at 0 °C (Zoffoli, 2008). Increasing the humidity inside the box using a restricted ventilation cluster bag and/or box liner has been beneficial for maintaining cluster freshness. ‘Red Globe’ clusters packed in a box liner with 2.0% ventilation area (VA) lost 1.7 times more weight than those packed in a box liner with 0.3% VA after 60 days storage at 0 °C. ‘Red Globe’ cluster quality was characterized by shoulder and central rachis thickness lower than 3 mm and 2.5 mm, respectively, at harvest. The clusters had poor rachis quality after 60 days at 0 °C when packed in a 2% polyethylene bag (Zoffoli, 2008). Hairline cracks Hairline cracks are an expression of phytotoxicity due to overexposure to sulfur dioxide (SO2) characterized by the development of small, fine, longitudinal, linear cracks, almost undetectable to the naked eye (Fig. 9.5a). Juice exudation from the split zone makes the berry skins wet and sticky. The incidence of hairlines increases when the concentration and time product (CT) of SO2 exceeds 3 mL L−1 h−1. No hairline is observed when the CT is below 0.8 mL L−1 h−1. Difference among orchards has been reported (Zoffoli et al., 2008) and overuse of gibberellic acid (GA) and forchlorfenuron (CPPU), for berry growing explains the susceptibility (Zoffoli et al., 2009a). Therefore, to reduce this disorder it is essential to use a minimal dose of SO2 that allows adequate decay protection without reducing berry quality (Zoffoli et al., 2008). Shatter Shatter (losing berries) is a physical condition representing the proportion of berries that have separated from the cap stem. It may be initiated by an abscission layer at the insertion of the berry to the pedicel during ripening, but symptoms appear at harvest and continue to occur in stored grapes until final consumption. However, in ‘Autumn Black’ clusters, shatter develops by separation of the berries with their pedicels. Shatter increases as grapes mature, and usually the severity is high in seedless cultivars (e.g., ‘Flame Seedless’ and ‘Thompson Seedless’) and low in seeded cultivars (e.g., ‘Red Globe’). Therefore, shatter severity varies from season to season, among table grape cultivars and among vineyards, according to harvest time and storage conditions. Table grape management can affect shatter

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Fig. 9.5

(a) hairline cracks; (b) berry splitting symptoms. Data from Zoffoli et al., 2008.

considerably. For instance, shatter increases with gibberellic acid and after forchlorfenuron applications for berry enlargement. Both growth regulators promote pedicel thickness (Zoffoli et al., 2009a). A positive correlation between pedicel thickness and peroxidase activity, stimulated by post-bloom applications of gibberellic acid to vines, was found (Pérez and Gómez, 1998). Similarly, shatter can considerably increase under rough handling at harvest and packing. Shatter tolerance has been established in some countries. For instance, a maximum of 3% shatter at harvest is currently accepted for highquality grapes. Another type of shatter is humid shatter, where berries separate, leaving part of the vascular bundle with the pedicel. This symptom often occurs in ‘Thompson Seedless’ and is associated with rough handling. Skin and flesh browning Berry browning is a physiological disorder, primarily of Muscat-type cultivars with high polyphenol concentrations, such as ‘Italia’, ‘Regal Seedless’, ‘Victoria’, ‘Princess’ and ‘Majestic’. Symptoms are external (skin) and internal (flesh) brown discolorations caused by polyphenol oxidation reactions in the presence of oxygen and polyphenol oxidase in damaged tissues. Skin browning is associated with physical, biological or chemical damage. For instance, rough handling of the grapes during harvest, packaging or transport often induces skin browning. The incidence of skin browning is low at harvest but increases after cool storage, particularly in fruit over-exposed to sun. Skin browning varies from year to year and among orchards. Research performed on the ‘Princess’ table grape cultivar

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has demonstrated that the incidence of skin browning increases when the grapes are harvested with TSS ≥18% or when the TA is ≤ 0.6% (Vial et al., 2005). Flesh browning symptoms can affect the entire berry and can be attributed to methyl bromide phytotoxicity (Auda et al., 1977; Leesch et al., 2008). Methyl bromide-treated berries have a significantly lower concentration of the natural antioxidant glutathione (Liyanage et al., 1993). Other flesh browning symptoms can be restricted to the vascular bundles or to the endocarp at the seed or rudimentary seed area (e.g., in ‘Thompson Seedless’). In some very susceptible table grape cultivars, e.g. ‘Italia’, it is postulated that the flesh browning disorder is associated with cell membrane damage induced by chilling injury. Freezing damage is visible as external browning and a milky color in the berry. The rachis and laterals of the cluster are also affected by freezing temperatures, with similar browning symptoms of water loss. Other external and internal browning symptoms can be caused by abiotic and biotic factors, such as the reddish ring spot at the touch point on the berry surface produced by thripsfeeding activity (Roditakis and Roditakis, 2007; Fourie, 2009). (See Plate XVII.) Splitting Fruit splitting is a common disorder in grapes, consisting of circumferential and longitudinal injuries, or both, on the grape berry surface (Fig. 9.5b). For instance, in ‘Thompson Seedless’ table grapes, circumferential ring fractures usually appear around the pedicel, and longitudinal fractures appear down the sides of overmature berries. Splitting develops during cell enlargement, coinciding with a high internal hydrostatic pressure. It has been demonstrated that turgor pressures of 15 and 40 atm are required for splitting in susceptible and resistant grape cultivars, respectively (Considine and Kriedemann, 1972). There is evidence that the skin of the grape is reinforced in the region of the lenticels. The split is thought to start from the less viscoelastic tissue surrounding the lenticel (Considine, 1982; Considine and Brown, 1981). Splitting can be induced by irrigation or rain, and it can also occur during storage (Nelson, 1985). Waterberry Waterberry is also known as ‘bunch stem necrosis’ ‘palo negro’, ‘shanking’, ‘stiellahme’ and ‘dessechement ed al rafle’. It is characterized by watery, soft, flabby berries that become opaque and lighter in color than normal berries. Waterberry appears during ripening, resulting from necrosis of the phloem in cluster stems and cap stems. Therefore, the flow of metabolites into the berries is interrupted, and the berries remain acidic with low TSS. Waterberry is associated with high total nitrogen and high ammonium levels in the stem tissues produced by lack of ammonium assimilation into proteins (Christensen and Boggero, 1985; Ruiz and Moyano, 1998; Silva et al., 1986). It is favored by high nitrogen fertilization, canopy shading and cool weather conditions during fruit ripening. It can be prevented by reducing nitrogen fertilization and thinning shoots, particularly during ripening. It is especially problematic in the cultivars ‘Thompson Seedless’, ‘Flame Seedless’, ‘Crimson Seedless’, ‘Calmeria’ and ‘Queen’;

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however, this disorder also affects wine cultivars (Ureta et al., 1981). Similarly, the development of soft berries with a transparent appearance has also been attributed to high concentrations of nitrogen, arginine and putrescine in the berries (Ruiz et al., 2004).

9.6

Postharvest handling and packaging

9.6.1 Harvest operation Table grapes are harvested when the grapes reach the optimum acceptability for the consumer, determined mainly by the sugar content (TSS 15 to 17%), titratable acidity (TA) and TSS:TA ratio (>20). Sugar content is measured by the TSS concentration using a refractometer, and the TA is measured by titration with 0.1 N sodium hydroxide to a phenolphthalein of pH 8.2 endpoint. A minimum maturity standard has been adopted by several countries to assure pleasant grapes at the consumer level. Although the critical value varies among countries, a TSS concentration of 16% has been adopted for most table grape cultivars; however, a 15% TSS concentration is considered acceptable in low acid cultivars such as ‘Red Globe’ and ‘Ribier’. In geographical areas where the degradation of acids occurs, a TSS:TA ratio of 20:1 is used as an index to determine the harvest time in early harvested grapes without decreasing the grape quality perception by consumers (Nelson, 1985). Detachment of grape clusters from the vines should be performed by trained operators, who carefully select mature grapes and avoid mechanical damage. The grape clusters can be trimmed in the field, introduced into a 60×40×25 cm plastic box, transported and packed in small grower-owned sheds or in a large packinghouse with cooling facilities. Clusters should be packed within the first 6 h after harvest. 9.6.2 Packaging operation There are two possibilities: field packaging and in-house packaging. Field packaging is a harvest operation where grapes are picked, sorted and packed directly into the shipping box. This packaging system allows transportation in a more protected manner and reduces water loss and bruising. In this process, pickers and packers work together, trimming and packing the clusters until finishing the box. The empty and filled boxes are left on the ground and other workers transport them to the shed area where the boxes await transport to the cooling facility. Otherwise, ‘avenue packing’ is an alternative to field packing in which clusters are trimmed and packed in different locations. The clusters are harvested, trimmed, cleaned and put into the field lug. Other workers transport the clusters to a selection and packaging site where clusters are packaged into shipping boxes. In-house packaging is done in relatively large houses, often under controlled temperature conditions where plastic boxes filled with clusters are placed onto a

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Fig. 9.6 Scheme of working table in packing line operation for table grapes: (A) empty field lugs; (B) fruit in field lugs with untrimmed table grapes; (C) empty shipping boxes; (D) packed boxes; (E) scale; (F) lug for packaging materials (bags, papers, generator pads).

packing belt from which workers start to prepare the clusters. Workers are located at a ‘working table’ (Fig. 9.6) where the clusters are selected, trimmed and transferred into the cleaned lug. Berries left from the cleaning and trimming operations are collected in individual containers located further down the working table or on a belt-conveyer that moves the dirty materials out of the area. Small, sharp scissors and a scale are provided at the working table. In the packing section, workers are allocated to a packaging table where they take the lug containing clean selected and trimmed clusters from the conveyer and pack clusters into different shipping boxes, according to cluster shape, berry color and cluster size. In a separate line, located 50 cm over the packing table workstation, a roller conveyer moves empty shipping boxes. Packaging materials, such as polyethylene boxes, bags, cartons, wooden or non-returnable plastic boxes, waxed paper, generator pads and plastic or paper bags, are provided at the packing table workstation. Shipping boxes are transported on pallet bases that are 120×100 cm or 120×80 cm (Europallet) in size. Therefore, the package sizes should meet the requirement of metric shipping containers. Special arrangement on the pallet must be considered when using 40×30 cm, 50×30 cm or 60×40 cm boxes 10 to 13 cm high. The pallet height cannot be more than 1.8 m, with 72 to 96 boxes per pallet depending on box dimensions (Fig. 9.7). 9.6.3 Labeling Each packaged box should include the necessary information to make it possible to trace the grapes from the vineyard to the market. Therefore, the producer brand name, geographical location, product name and table grape cultivar (variety) should be identified on each shipping box. The weight in kilograms and date of packaging must be indicated as well. Postharvest treatments, such as the use of SO2, must be clearly marked on the container to comply with market requirements.

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Fig. 9.7

Pallets with two box arrangement types: (a) five columns with 15 layers of 40 cm ×60 cm boxes and (b) six columns with 16 layers of 40 cm×50 cm boxes.

9.6.4 Cooling operation To avoid condensation on the berry surface during packaging, grapes should not be cooled down to 0 °C immediately after harvest, and trimmed grape clusters must be stored and packed in holding chambers at 15 °C and 90% relative humidity (RH), provided by evaporative cooling systems. Packed fruit should be stacked for cooling within 6 h after harvest. Forced air cooling, which delivers cool air directly to the fruit by establishing a pressure gradient across the lugs in the pallet, removes the latent heat of the grapes faster than any other cooling system, reducing water vapor deficit and the respiration rate of the grapes and rapidly arresting the development of decay fungi. The speed at which the forced air cooling cools down the grapes from field temperature depends on the volume of air passing through the fruit and on the mass of grapes and the field temperature of the grapes. However, as the air volume increases, the required static pressure greatly increases, raising the energy consumption of the fan. Generally, the system should be designed to deliver 1 to 2 cfm lb−1 (0.001 to 0.002 m3 sec−1 kg−1) of packaged grapes (Nelson, 1985) (Fig. 9.8). Air flowing through packaged grapes meets some resistance. The total resistance depends on the number of packages in line across a stack and the

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Forced air cooling.

packaging materials used. The bag ventilation area of the box and the use of wax to cover the inside of the box are the main factors that affect the flow of cooling air through packaged grapes. Vented box liners increase the cooling time by a factor of three or four as compared to no liners. Shipping containers including paper in the four sides of the box increase the 7/8 cooling time from 3 to 12 h, when a box liner with 0.3% vent area (VA) is used. The airflow resistance (‘static head’) is measured as millimeters of water, and the difference in pressure between the outer face of the stack (higher pressure) and the inner face (downstream, where the air leaves) is determined. Any air leakage in the pallet stacking reduces the efficacy of forced air cooling. A total VA of at least 4% for the vented face has been a general recommendation for the shipping box. However, when grapes are densely packed and a polyethylene bag is included, the vent should be located along the top edge of the vented face. Elongated vents are preferable to round holes. Conduction cooling rather than convection cooling, by incorporation of a polyethylene bag, promotes water condensation inside the box liner walls; a difference of 4 °C can be found between outer and inner faces of the pallet. Changing the pressure gradient across the pallet reduces the temperature difference but increases the risk of high temperatures in the middle of the pallet; therefore, the viability of this operation should be evaluated before use. Fruits stacked on a pallet are stored in a cold room, in order to homogenize the fruit temperature before loading them into the container or into the vessel. During

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temperature homogenization, the air speed is set at 1 to 1.5 m s−1 compared with an air speed of 0.1 to 0.2 m s−1 during the holding period. A period of 3 to 4 days is required for pulp temperature homogenization; the length of this period depends on the fruit temperature and the amount of stacked fruit in relation to the total heat removal capacity of the cold room.

9.7 Temperature management Recommended pulp temperatures for storage of grapes are −0.5 °C to 0 °C, with 95% RH and an airflow of 20 to 40 cfm t−1. The storage room should be operated between −1 and 0°C, since berries freeze near −2 °C and the rachis freezes at −1 °C. Forced air cooling reduces the fruit temperature to between 0 to 4 °C within less than 12 h. This operation is usually done with 32 000 kg of packed grapes starting with a 25 to 30 °C pulp temperature.

9.8

Sulfur dioxide treatments

Sulfur dioxide (SO2) fumigation treatments and/or SO2 generator pads inside grape boxes have been used for many years as methods of controlling decay caused by B. cinerea in stored grapes (Harvey and Uota, 1978; Nelson and Ahmedullah, 1976; Nelson and Baker, 1963). Currently, the use of SO2 is a standard sanitation practice to treat grapes for long distance transportation and long cold storage. SO2 fumigation reduces the surface contamination of grape clusters with conidia of B. cinerea and prevents the rapid spread of the mycelium of B. cinerea by contact between diseased and healthy grapes. Because of its capacity to inhibit enzyme-catalyzed reactions, SO2 reduces stem browning, helping to maintain the stem appearance for longer periods of time. 9.8.1 Mode of action SO2 does not penetrate the intact berry skin, remaining almost completely on the berry surface. Therefore, it only kills spores and mycelia present on the surface of the berries and is unable to control the fungus inside grapes (Nelson, 1958; Smilanick et al., 1990a). However, SO2 is efficiently absorbed through berry injuries (e.g., hairline cracks, splitting, non-suberized lenticels), resulting in partial or entire berry bleaching. The fungal toxicity of the SO2 treatment is attributed almost entirely to the fact that SO2 can be absorbed passively through the plasma membrane, causing oxidation reactions that affect different metabolic processes of B. cinerea and other fungi. The sensitivity of conidia of B. cinerea to SO2 increases two- to fourfold for every 10 °C increment between 0 and 32 °C, which has been attributed to the effect of temperature on SO2 absorption (Smilanick et al., 1990b) (Fig. 9.9).

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Fig. 9.9 Effect of temperature on the toxicity of sulfur dioxide (SO2) against Botrytis cinerea. Estimated lethal concentrations (LC) to obtain a 50% (LC50) and 99% (LC99) control (data from Smilanick et al., 1990b).

9.8.2 SO2 dosages The amount of SO2 needed to kill conidia and inactivate exposed mycelia of B. cinerea at a given temperature is dependent on the SO2 concentration and the length of the fumigation period. In general, higher SO2 concentrations are needed to kill conidia than mycelia (Palou et al., 2002a; Smilanick and Henson, 1992). Formulas for calculating the SO2 concentration during fumigation are available (Nelson, 1985). However, a concentration time (CT) concept has been developed to calculate the SO2 exposure needed to arrest grape decay fungi for total use of the SO2 with minimal SO2 release into the atmosphere (Smilanick and Henson, 1992). This CT value can be obtained with different combinations of SO2 concentration and time. For instance, a CT of 100 is near the minimum value (CT 78.3 ± 22.3) needed to kill conidia and inhibit mycelial growth of B. cinerea at 0 °C, and it can be obtained using 50 mg L−1 for 2 h or 100 mg L−1 for 1 h or 200 mg L−1 for 0.5 h. For the initial fumigation of grapes after harvest, where the control of spores on the surface of grapes is required, 100 mg L−1 – h should be sufficient; for subsequent storage fumigations where control of mycelial growth from latent infections is required, 50 mg L−1 – h should be sufficient (Smilanick and Henson, 1992). It has been demonstrated that a low but constant SO2 emission rate of 3.6 to 5.5 μmol kg−1 h−1 is sufficient to arrest the dispersion of gray mold in grapes stored at 0 °C and 95–98% RH (Palou et al., 2002a).

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9.8.3 Pre-packaging SO2 fumigation The pre-packaging SO2 fumigation is commonly done in sealed fumigation chambers, immediately after harvest, using 0.5% SO2, w/v, for 15 to 20 min at 20–22 °C. To reduce the amount of SO2 released into the atmosphere, the SO2 concentration applied must be adjusted, using a dosimeter tube, to 100 mg L−1 – h CT value. Different relationships between the initial SO2 concentration and the CT value will be obtained depending on the amount of fruit and the chamber construction. The grapes are then ventilated before continuing with the packaging process. Alternatively, SO2 fumigation can be applied using SO2 guns (e.g., DOSIGAS, Proquivi, Santiago Chile; YTGas, YT Ingeniería Ltda., Viña del Mar, Chile) to deliver an exact amount of SO2 per box of packaged grapes. A minimum of 60 mL of SO2 is recommended for 8 kg of fruit. This latter methodology has been useful for grapes packaged in the field, replacing the above-mentioned pre-packaging SO2 fumigation. 9.8.4 Post-packaging SO2 fumigation SO2 fumigation can be carried out in packaged grapes stored at 0 °C in cold rooms, and it is often performed in conjunction with forced air cooling, using 5000 to 10 000 mg L−1 SO2 for 20 to 30 min (Smilanick et al., 1990b). Forced air cooling ensures a good distribution and penetration of the SO2 in palletized boxes. Repeated weekly applications with lower SO2 concentrations (2500 mg L−1 SO2) are needed to prevent a rapid spread of B. cinerea by contact between diseased and healthy grapes. SO2 fumigations at an even lower SO2 concentration (200 mg L−1), applied three times a week can be successful in cold stored grapes, and the lower concentration reduces the risk of SO2 phytotoxicity (Marois et al., 1986). Finally, evaluating the CT value at different points in the chamber will ensure that the correct SO2 concentration is applied. SO2 generator pads (e.g., Proteku in Brazil; Fresca, Osku, Proem and Uvas Quality in Chile; Uvasys in South Africa) consist of sodium metabisulfite (Na2S2O5) grains enclosed in paper-plastic pockets inside a pad (Nelson and Ahmedullah, 1976; Zoffoli, 2002). The generator pads vary in dimensions (23×33 cm, 20×46 cm, 26×46 cm, 33×46 cm) and can contain 20, 24, 32 or 40 pockets per pad. The Na2S2O5, when hydrated by water vapor, continuously emits SO2, protecting grapes from decay for up to 60 days during cold storage. The rate of emission of SO2 from a generator pad is proportional to the temperature and humidity inside the box. Currently, one pad containing 8 g of sodium metabisulfite per 8.2 kg box is placed over the grapes in each box, and 0.1 g of sodium metabisulfite is spent per day. These SO2 generator pads are particularly needed for long ocean shipments, when grapes cannot be subjected to periodic SO2 fumigations. SO2 generator pads made with dual-release SO2 phases are currently used. The dual-release SO2 phases are achieved by using small and large Na2S2O5 particles, adequate Na2S2O5 formulations and a pad made of paper for the fast SO2 release phase, and one made of polyethylene combined with paper for the

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slow SO2 release phase. Increasing the proportion of polyethylene in the slowrelease phase reduces the amount of sodium metabisulfite, and the same effect is produced by increasing the perforation area of the polyethylene bag (Zoffoli et al., 2005) or enclosing the SO2 generating pad in a plastic laminated with macroperforation (Zutahy et al., 2008). Commonly, the SO2 generator pads contain 1 and 7 g of Na2S2O5 in fast-release and slow-release formulations, respectively. The SO2 generator pads release SO2 as a function of temperature and RH (Fig. 9.10). The dynamics of SO2 emission vary during postharvest storage, achieving a maximum SO2 concentration after about 2 h at room temperature before pre-cooling; the total fast-release phase is released during the forced air cooling process (Fig. 9.11). Therefore, the SO2 concentration during cold storage depends on the slow release phase, which is liberated slowly or rapidly depending on temperature variation, RH and condensation inside the box. The distribution of SO2 inside packed boxes of grapes is not necessarily uniform; it is generally higher at the top of the box, just below the generator pad (Fig. 9.11). The distribution of the SO2 also depends on the type of packaging material used as well as the tightness of the pack, the use of pallets and the system of air circulation employed (Harvey and Uota, 1978; Harvey et al., 1988). Because of the uneven distribution of SO2 inside the packages, the addition of a second SO2 generator pad, placed at the bottom of the box, has been recommended; however, the risk of phytotoxicity consequently increases considerably. A novel sulfur

Fig. 9.10 Evolution of SO2 concentration from generating pad (8 g, sodium metabisulfite) stored at 100%, 85% and 75% relative humidity (RH) and 20°C. Data from Zoffoli, 2008.

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Fig. 9.11 Evolution of SO2 gas obtained with SO2 generating pad (Uvasys). SO2 generating pad was placed at the top of box of ‘Thompson Seedless’ table grapes. Measurements were made at the top, above the table grapes or at the base of the box, below the table grapes, before cooling at 20°C. Data from Zoffoli et al., 2009.

dioxide-releasing perforated plastic liner has been evaluated to improve the uniformity of SO2 inside the box (Mlikota Gabler et al., 2007; Zoffoli et al., 2007). 9.8.5 SO2 tolerance Because ingestion of SO2 residues (sulfites) can cause hypersensitive reactions in some people, the Environmental Protection Agency (EPA) established a 10 mg kg−1 residue tolerance in the US. At present, the SO2 used in Europe is considered a food additive, therefore specific labeling is required. In the US, the use of SO2 is no longer accepted for certified organic grapes, some regulatory agencies do not allow the discharge of SO2 into the air after fumigation and workers must not be exposed to the gas at levels above 2 mg L−1 (Lichter et al., 2006). 9.8.6 SO2 alternatives Several alternatives to the use of SO2 have been studied, including the use of acetic acid vapor (Moyls et al., 1996; Sholberg et al., 1996), chlorine gas (Zoffoli

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et al., 1999) and ethanol (Karabulut et al., 2005). However, these alternatives have not yet been applied commercially (Lichter et al., 2006). Ozone (O3) has also been evaluated for the same purpose (Palou et al., 2002b; Mlikota Gabler et al., 2010; Sarig et al., 1996). Muscodor albus has been formulated for use in a pad or sachet delivery system for biofumigation to control postharvest gray mold through production of lethal alcohol volatiles (Mlikota Gabler et al., 2006). Combinations of 10 or 15% CO2 with 3, 6 or 12% O2 have been proven to be effective in controlling B. cinerea in late-harvested ‘Thompson Seedless’ table grapes for up to 90 days at 0 °C (Crisosto et al., 2002).

9.9

Quarantine treatments

Table grapes for the export market must comply with sanitary requirements imposed by the importing countries. For instance, grapes shipped to the US should comply with the rules established by the USDA Animal and Plant Health Inspection Service (USDA-APHIS). According to these rules, quarantine treatments, consisting of methyl bromide fumigation or continuous low temperature treatment, must be applied to grapes imported from any country. The concentration and time of methyl bromide fumigation depends on the berry temperature. The lower the temperature, the higher the concentration of methyl bromide needed to kill the insects for which the quarantine is imposed. However, it should be considered that the risk of berry phytotoxicity is increased with high methyl bromide concentrations. A summary of the protocol for methyl bromide application is described in USDA-APHIS PPQ (2009), and an example is provided in Table 9.2. Methyl bromide is currently being restricted because of health, safety and environmental concerns (as it is a stratospheric ozone-depleting substance). Therefore alternatives have been evaluated, but efficacy appears to be variable between insects, among life stages of insects and with regard to the effect on fruit quality. Among laboratory studies ethyl formate appears to be the most promising volatile compound for postharvest insect control on table grapes (Simpson et al., 2007). Table 9.2 Quarantine treatment of methyl bromide fumigation for table grape entering the US from Chile to mitigate the pest risk of Brevipalpus chilensis Temperature °C

>26.5 21–26.4 15.5–20.9 10.0–15.4 4.5–9.9

Dosage rate

Minimum concentration readings (g m−3)

g m−3

Lb 1,000 ft−3

0.5 h

2.5 h

24 32 40 48 64

1.5 2.0 2.5 3.0 4.0

10 26 32 38 48

14 19 24 29 38

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9.10 Transport The commercialization of table grapes requires the selection of a transport system that allows the maintenance of a uniform fruit temperature, optimum air circulation and compatibility between fruit species. Transportation times for countries located 30 to 40 days away from the markets are critical because most of the postharvest life of the grape will be spent in a refrigerated marine container or inside the cold chamber of the vessel.

9.10.1 Marine containers Marine containers are available in capacities of 28, 59 and 68 m3. They have independent refrigerated units, powered by 220- or 440-volt three-phase electricity that allows for direct plugging in to the electric power system on the vessel or at port. A temperature of −0.5 °C should be specified in the container thermostat for grapes. Containers are designed to deliver and maintain the storage temperature, and they cannot reduce the grape temperature during transport. Because of low grape respiration rates and low ethylene sensitivity, marine containers loaded with grapes should be set without air exchange. It is important to consider that the SO2 produced by the SO2 generating pads accumulates, so grapes must not be loaded along with fruits or vegetables sensitive to SO2 damage, such as apples, pears, plums, peaches or nectarines. Otherwise, washing with alkaline solution is required in order to avoid corrosion inside the container. The marine containers should be cooled down to −0.5 °C, which is the desired transport temperature, while they are connected directly to the electric system of the dock. If the marine containers are open at the dock in a humid environment, the marine containers should be cooled to the dew point temperature of the outside air in order to avoid condensation inside the container (Thompson et al., 2000). Dew point values in relation to temperature and RH are given in Fig. 9.12. A uniform temperature inside the container can be obtained by following proper loading practices (Thompson et al., 2000). In contrast to the horizontal air flow of cold chambers and forced air cooling, refrigerated containers are equipped with a bottom air delivery system. Air from the refrigeration unit flows from the floor through the packages vertically and returns horizontally across the top of the load and back to the refrigeration unit to complete the air cycle. To allow vertical airflow from the floor to the pallet load, pallet containers and inner packaging should have sufficient venting and air space, and the floor should be completely covered by the produce or by a solid material. If the produce is palletized, the pallet opening for forklifts should also be covered to block air from traveling horizontally. The open floor between pallets should also be covered. A description of loading systems is provided in Fig. 9.13. Temperature recorders should be installed in order to register the supply and return air temperatures.

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Dew point temperature related to relative humidity and air temperature.

Fig. 9.13 (a) Pallet distribution inside the container; (b) view of pallet and floor covering to improve vertical air circulation. Data from Thompson et al., 2000.

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9.11

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Processing

Grapes are often produced for fresh consumption, such as table grapes, but they are also sold as the following products: grape juice, partially fermented grape juice (‘chicha’ in some Latin-American countries), wine, alcoholic beverages (e.g., brandy, cognac, grappa, jerez, oporto, pisco and singani), wine vinegar, grape jam, grape preserves and raisins. Additionally, grapes can be used to produce grape seed oil used for cooking, salad dressings or cosmetic products (e.g., body creams and lip balm). Although specific grape cultivars are used to elaborate each product, table grape cultivars are often produced both for fresh consumption and for drying as raisins. In this section, general information regarding raisin production is presented.

9.11.1 Raisins Since ancient times, raisins have been produced from a different type of table grape cultivars, such as V. vinifera, from which raisins acquire their characteristic flavor, aroma, color, shape and size. Raisin production is an industry of 700 000 tons worldwide. The largest raisin-producing countries, which account for over 80% of the global raisin production, are Turkey and the United States, which annually produce 230 000 tons and 250 000 tons, respectively. Raisins are also produced in Afghanistan, Argentina, Australia, Chile, Greece, India, Iran, Mexico, South Africa, Spain and other countries where the climate for raisin production is ideal with very dry, warm summers and mild winters (USDA, 2008). Raisins are a good source of folic acid, pantothenic acid, vitamin B6 and other vitamins that are essential for human nutrition. They are also an important source of calcium, magnesium, phosphorus, iron, copper and zinc. Raisins do not have any fat, which is considered an advantage for human nutrition (Bongers et al., 1991). They are a naturally stable food and are resistant to spoilage because of their low moisture content, high amount of soluble solids and low pH. Grape cultivars and type of raisins Four types of raisins are demanded internationally: dark-skinned raisins (sundried raisins), golden raisins (heat-dried raisins), Corinth raisins (small, dark raisins primarily from ‘Black Corinth’ grapes) and snack raisins (large raisins). Raisins are produced primarily from the following types of grapes: ‘Thompson Seedless’, ‘Black Corinth’, ‘Fiesta’, ‘Flame Seedless’ and ‘Muscat’. ‘Thompson Seedless’ is one of the most important grape cultivars for the production of raisins because of its oval and elongated shape, early ripening and the grapes’ facility to remain separated from each other after drying. However, in a test of several cultivars, ‘Thompson Seedless’ consistently dried the slowest (Ramming, 2009). Other cultivars, such as ‘Black Corinth’ which originated from Greece, yield smaller raisins than the ‘Thompson Seedless’ cultivars. Raisins produced from ‘Black Corinth’ cultivars are valued by the pastry industry because of their size,

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spherical shape, reddish to black color, thin skin and tendency to be seedless. They perform well because of their early ripening, quick drying and high production. Muscat grape cultivars, such as the ‘Muscat of Alexandria’ cultivar, are another important source for raisin production because they are large, juicy and contain few seeds. They are also dull green in color and have a sweet and attractive muscat flavor. However, the seeds must be removed before drying. Raisin production process The overall raisin production process includes the following: grape harvesting, drying, processing and packaging. Grape harvesting Grapes are hand picked or machine harvested at the maximum concentration of sugar that is evaluated by the TSS content (19%–24%) (Christensen et al., 1995). Mechanized fruit harvest requires a special trellising system that facilitates vine pruning, vine harvesting and cane cutting before the grapes are harvested to aid in fruit removal and to minimize mechanical damage. Grape drying Raisins can be produced using natural and artificial drying methods. Natural methods include sun-dried and dried-on-vine, whereas artificial methods include the use of heated air dryers. Natural methods are usually preferred because of the costs. During raisin drying, moisture content is reduced from approximately 75% to below 15%, yielding approximately 1 kg of raisins out of 4 kg of grapes. The final grape color change to brown or dark brown depends on the grape cultivar and the drying method, and the sensory quality is commonly affected by the drying process used (Thompson, 2000). Sun-dried Sun-dried grapes are produced by placing grape clusters on 80 cm by 90 cm papers or polyethylene trays that are either short (2 m to 6 m) or long (greater than 6 m). The trays are laid out on concrete floors next to the vineyards or on leveled ground between the vine rows or next to the vineyards, for two to four weeks depending on weather conditions. When the moisture content is reduced to approximately 15%, the individual short paper trays are rolled up with the raisins to form packages, or the raisins are swept into boxes or bins and transported to a processing plant. The disadvantage of the short trays is that they cannot be easily rolled up like a cigarette to protect the raisins against over-drying, caramelization and rain. Long trays usually require turning and pickup machinery that reduces cost and eliminates all manual handling of trays after picking. Pickup machines can be self-propelled or tractor-pulled. The raisins are placed in bins behind the pickup unit or across the row to a separate bin on a tractor-pulled trailer (Christensen and Peacock, 2000).

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Dried-on-vine The dried-on-vine method of raisin production often uses mechanical harvesters, and this method is accomplished by maintaining the attachment of grape clusters to the vines that have been trained to allow the clusters maximal sun exposure. With this method, 50% of the fruit near the leaf area is removed by hand pruning the canes six weeks before harvest. During the cane cutting, clusters are dipped in a 0.5% ethyl oleate and 0.6% potassium carbonate solution to increase the drying rate and to achieve the desired light-gold fruit color in the ‘Thompson Seedless’ raisins (Dincer, 1996; Uhlig et al., 1996). The dried-on-vine method reduces the risk of rain damage, and it is less labor intensive than raisin production by sun drying. Hot-air drying In the hot-air drying method, grapes are hand-harvested and transported to a drying facility that has a concrete tunnel with a fan and propane burner mounted above the drying chamber to provide hot air flow that is between 65°C and 70°C. To facilitate water loss, grapes are dipped for 8 to 15 seconds in a hot solution at 82°C that contains 0.2%–0.5% sodium hydroxide and then are rinsed with cold water. The grapes are then spread on drying trays and treated for 5 to 8 hours with SO2 at a concentration of 2 kilograms to 4 kilograms per ton of grapes. This drying method has the advantage of ensuring a uniform supply of golden raisins, but the relatively high cost limits its use. Other pretreatment techniques, such as the use of a microwave or a pulsed electric field, are being evaluated (Dev et al., 2008). A high correlation exists between the residual polyphenol oxidase (PPO) activity and the darkness of the raisins, known as the Hunterlab L value, after drying the raisins at 50°C. Addition of SO2 reduces the PPO activity and enhances the production of light-colored raisins. Further, pretreatment of the grapes in 93°C water with a 2 minute dip produced similar results (Aguilera et al., 1987). For drying, the grapes are loaded onto 90 cm by 180 cm trays made of wood or plywood. The trays are supported in wheeled trucks that hold 25 to 26 trays each. Truck holders move through the tunnel in the opposite direction to the hot air, which allows the hottest product to be in contact with the highest temperature of air. Air temperature is kept at 65–70°C, and it has to be adjusted depending on the amount of fruit in the tunnel to avoid sugar caramelization and off-flavor development (Thompson, 2000). Raisin processing At the processing plant, raisins are passed over wire screens that are shaken to remove dirt and debris. Raisins can be stored for later processing at this time, and in this case, methyl bromide or phosphine fumigant is used to avoid insect infestations during storage. Otherwise, raisins are emptied onto a conveyer line where the residual debris is removed by passing the raisins over a fine mesh screen with forced air blowing

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on them. The raisins are then shaken to be separated from bunches followed by the removal of cap stems, either mechanically using two rotating, conical surfaces or manually. When raisins are produced from seeded grape cultivars, the seeds are mechanically removed at this stage. Finally, raisins are sorted according to their size by passing them through a series of mesh screens. Raisins are then placed into packages ranging in size from small, one-half ounce cardboard containers for individual consumption to large, 10 kg or 500 kg containers for industrial use. Raisins are stored and transported under cold conditions (10–15°C) with 50–60% RH. To maintain the raisin quality, a low oxygen atmosphere of 1% is recommended (Guadagni et al., 1978).

9.12

Conclusions

Table grapes are grown in vast areas that include Mediterranean, tropical and subtropical regions. Most of the varieties are sold for fresh consumption and as raisins. Grape is a non-climacteric fruit with a relatively low respiration rate. Main changes in berry composition and softening occur after veraison, promoted by abscisic acid synergistically with ethylene. Decay (biotic) and dehydration (abiotic) are the main deterioration factors of table grape during storage at 0°C. Fungicide application integrated with cultural management of the vine during preharvest reduces the risk of decay, and in combination with 0°C and 90–95% relative humidity maintains the freshness of the rachis during storage. The use of in-package SO2 release or periodic SO2 fumigation during storage is required to protect the grape from decay during storage and transport, making the table grape industry highly dependent on this compound.

9.13

References

Aguilera, J.M., Oppermann, K., and Sanchez, F. (1987), ‘Kinetics of browning of Sultana grapes’, J. Food Sci., 52, 991–993. Auda, C.M., Berger, H., Reszezfuski, A., Adriana and Lizana, A. (1977), ‘Pardeamiento interno de uvas Sultanina’, Inv. Agricola (Chile), 3, 43–49. Blanke, M.M. and Leyhe, A. (1987), ‘Stomatal activity of the grape berry cv. Riesling, Muller Thurgau and Ehrenfelser’, J. Plant Physiol., 127, 451–460. Bongers, A.J., Hinsch, R.T., and Bus, V.G. (1991), ‘Physical and chemical characteristics of raisins from several countries’, Am. J. Enol. Vitic., 42, 76–78. Briceño, E. and Latorre, B. (2008), ‘Characterization of Cladosporium rot in grapevines, a problem of growing importance in Chile’, Plant Dis., 92, 1635–1642. Broome, J.C., English, J.T., Marois, J.J., Latorre, B.A. and Aviles, J.C. (1995), ‘Development of an infection model for Botrytis cinerea bunch rot of grapes based on wetness duration and temperature’, Phytopathology, 85, 97–102. Cadle-Davidson, L. (2008), ‘Monitoring pathogenesis of natural Botrytis cinerea infections in developing grape berries’, Am. J. Enol. Vitic., 59, 387–395. Camili, E.C. and Benato, E.A. (2005), ‘Diseases of grapes’, Informe Agropecuario, 26, 50–55.

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Cantín, C.M., Fidelibus, M., and Crisosto, C. (2007), ‘Application of abscisic acid (ABA) at veraison advanced red color development and maintained postharvest quality of “Crimson Seedless” grapes’, Postharvest Biol. Technol., 46, 237–241. Casado, C.G. and Heredia, A. (1999), ‘Structure and dynamics of reconstituted cuticular waxes of grape berry cuticle (Vitis vinifera L.)’, J. Exp. Bot. 50, 175–182. Christensen, P.L., Bianchi, M.L., Lynn, C.D., Kasimatis, A.N. and Miller, M.W. (1995), ‘Harvest date on Thompson Seedless grapes and raisins. I. Fruit composition, characteristics, and yield’. Am. J. Enol. Vitic, 46, 10–16. Christensen, L.P., and Boggero, J.D. (1985), ‘A study of mineral nutrition relationships of waterberry in Thompson Seedless’, Am. J. Enol. Vitic., 36, 57–64. Christensen, P. L. and Peacock, W.L. (2000), ‘The raisin drying process’. In: Raisin production manual, pp. 207–216, P. Christensen (ed.), University of California, Agriculture and Natural Resources, Publication 3393, Oakland, CA, USA. Coertze, S., Holz, G., and Sadie, A. (2001), ‘Germination and establishment of infection on grape berries by single airborne conidia of Botrytis cinerea’, Plant Dis., 85, 668–677. Coombe, B.G. (1960), ‘Relationship of growth and development to changes in sugars, auxins, and gibberellins in fruit of seeded and seedless varieties of Vitis vinifera’, Plant Physiol, 35, 241–250. Coombe, B.G., and Hale, C.R. (1973), ‘The hormone content of ripening grape berries and the effect of growth substances treatments’, Plant Physiol., 51, 629–634. Considine, J.A. (1982), ‘Physical aspects of fruit growth: cuticular fracture and fracture patterns in relation to fruit structure in Vitis vinifera’, J. Hort. Sci., 57, 79–91. Considine, J.A., and Brown, K. (1981), ‘Physical aspect of fruit growth: theoretical analysis of distribution of surface growth forces in fruits in relation to cracking and splitting’, Plant Physiol., 68, 371–376. Considine, J.A., and Kriedemann, P.E. (1972), ‘Fruit splitting in grapes: determination of the critical turgor pressure’, Aust. J. Agr. Res., 23, 17–24. Crisosto, C.H., Garner, D. and Crisosto, G. (2002), ‘High carbon dioxide atmosphere affect stored “Thompson Seedless” table grapes’, HortScience, 37, 1074–1078. Crisosto, C.H., Smilanick, J.L. and Dokoozlian, N.K. (2001), ‘Table grapes suffer water loss, stem browning during cooling delays’, Calif. Agric., 55, 39–42. Dev, S.E., Padmini, T., Adedeji, A., Gariépy, Y. and Raghavan, G.S. (2008), ‘A comparative study on the effect of chemical, microwave, and pulsed electric pretreatments on convective drying and quality of raisins’, Dry. Technol., 26, 1238–1243. Dincer, I. (1996), ‘Sun drying of “Sultana” grapes’. Dry. Technol., 14, 1827–1838. Downton, W.J.S. and Loveys, B.R. (1978), ‘Compositional changes during grape berry developmente in relation to abscisic acid and salinity’, Austr. J. of Plant Physiol., 5, 415–423. Donoso, A., and Latorre, B.A. (2006), ‘Characterization of blue mold caused by Penicillium spp. in cold stored table grapes’, Cien. Inv. Agr., 33, 119–130. Fourie, J.F, (2008), ‘Harvesting, handling and storage of table grapes (with focus on preand post-harvest pathological aspects)’, Acta Hort., 785, 421–424. Fourie, J.F. (2009), ‘Browning of table grape’, SA. Fruit Journal, 8, 52–53. Franck, J., Latorre, B.A., Torres, R. and Zoffoli, J.P. (2005), ‘The effect of preharvest fungicide and postharvest sulfur dioxide use on postharvest decay of table grapes caused by Penicillium expansum’, Postharvest Biol. Technol., 37, 20–30. Gardea, A.A., Martínez-Tellez, M.A., Sanchez, A., Baez, M., Siller, J.H., et al. (1994), ‘Post-harvest weight loss of Flame Seedless clusters’, In: International Symposium on Table Grape Production, Anaheim, CA. Am. Soc. Enol. Vitic., 203–206. Gao, H., Hu, X., Zhang, H., Wang, S. and Liu, L. (2003), ‘Study on sensitivity of table grapes to SO2’, Acta Hort., 628, 541–548. Greyling, M. (2007). Guidelines for Preparing Export Table Grapes, Capespan Export (Cty) Limited. Besville, South Africa. 77 pp.

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Mlikota Gabler, F., Zoffoli J.P., and Smilanick, J.L. (2007), ‘Sulfur dioxide-releasing perforated plastic liners to control postharvest gray mold of Redglobe table grapes’, 5th International Table Grape Symposium, Someret West, South Africa, 14–16 November. Mlikota Gabler, F., Smilanick, J.L., Mansour, M.F., and Karaca H. (2010), ‘Influence of fumigation with high concentrations of ozone gas on postharvest gray mold and fungicide residues on table grapes’, Postharvest Biol. Technol., 55, 85–90. Morgan, D.P., and Michailides, T.J. (2004), ‘First report of melting decay of “Red Globe” grapes in California’, Plant Dis., 88, 1047–1047. Moyls, A.L., Sholberg, P.L., and Gaunce, A.P. (1996), ‘Modified-atmosphere packaging of grapes and strawberries fumigated with acetic acid’, HortScience, 31, 414–416. Nair, N.G., and Allen, R.N. (1993), ‘Infection of grape flowers and berries by Botrytis cinerea as a function of time and temperature’, Mycol. Res., 97, 1012–1014. Nelson, K.E. (1958), ‘Some studies of the action of sulfur dioxide in the control of Botrytis rot of Tokey grapes’, J. Am. Soc. Hortic. Sci., 71, 183–189. Nelson, K.E. (1985), Harvesting and Handling California Table Grapes for Market, Pub. 1913. University of California, Division of Agriculture Science, Oakland, CA, USA, p. 52–53. Nelson, K.E., and Ahmedullah, M. (1976), ‘Packaging and decay control system for storage and transit of table grapes for export’, Am. J. Enol. Vitic, 24, 74–79. Nelson, K.E., and Baker, G.A. (1963), ‘Studies on the sulfur dioxide fumigation of table grapes’, Am. J. Enol. Vitic., 14, 13–22. Palou, L., Crisosto, C.H., Garner, D., Basinal, L.M., Smilanick, J.L., and Zoffoli, J.P. (2002a), ‘Minimum constant sulfur dioxide emission rates to control gray mold of cold stored table grapes’, Am. J. Enol. Vitic., 53, 110–115. Palou, L., Crisosto, C.H., Smilanick, J.L., Adaskaveg, J.E., and Zoffoli, J.P. (2002b), ‘Effects of continuous 0.3 ppm ozone exposure on decay development and physiological responses of peaches and table grapes in cold storage’, Postharvest Biol. Technol., 24, 39–48. Peppi, M.C., Fidelibus, M.W., and Dokoozlian, N. (2006), ‘Abscisic acid application timing and concentration affect firmness, pigmentation and color of “Flame Seedless” grapes’, HortScience, 41, 1–6. Peppi, M.C., Fidelibus, M.W., and Dokoozlian, N. (2007), ‘Application timing and concentration of abscisic acid affect the quality of “Redglobe” grapes’, J. Hort. Sci. Biotech., 82, 304–310. Pérez, F., and Gómez, M. (1998), ‘Gibberellic acid stimulation of isoperoxidase from pedicel of grape’, Phytochemistry, 48, 411–414. Pommer, C.V. (2006), ‘Double cropping of table grapes in Brazil’, Chronica Horticulturae 46, 22–25. Possinhan, J.V. (2008), ‘Developments in the production of table grapes, wine and raisins in tropical regions of the world’, Acta Hort., 785, 45–50. Ramming, D.W. (2009), ‘Water loss from fresh berries of raisin cultivars under controlled drying conditions’, Am. J. Enol. Vitic., 60, 208–214. Riederer, M. and Schreiber, L. (2001), ‘Protecting against water loss: analysis of the barrier properties of plant cuticles’, J. Exp. Bot., 52, 2023–2032. Roditakis, E. and Roditakis, N.E. (2007), ‘Assessment of the damage potential of three species of white variety table grapes – In vitro experiments’, Crop Protection, 26, 476–483. Rooney-Latham, S., Janousek, C.N., Eskalen, A., and Gubler, W.D. (2008), ‘First report of Aspergillus carbonarius causing sour rot of table grapes (Vitis vinifera) in California’, Plant Dis., 92, 651. Rosenquist, J.K., and Morrison, J.C. (1988), ‘The development of the cuticle and epicutical wax of the grape berry’, Vitis., 27, 63–70. Ruiz, R. and Moyano, S. (1998), ‘Bunch stem necrosis in grapes and its relationship to elevated putrescine levels and low potassium content’, Aust. and N.Z. Wine Industry J., 13, 319–324.

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Zoffoli, J.P. (2002), ‘Orientaciones para un manejo eficiente del generador de anhídrido sulfuroso en el embalaje de uva de mesa’, ACONEX (Chile), 75, 20–25. Zoffoli, J.P. (2008), ‘Postharvest handling of table grape’, Acta Hort., 785, 415–420 Zoffoli, J.P., Latorre, B.A., and Naranjo, P. (2008), ‘Hairline, a postharvest cracking disorder in table grapes induced by sulfur dioxide’, Postharvest Biol. Technol., 47, 90–97. Zoffoli, J.P., Latorre, B.A., and Naranjo, P. (2009a), ‘Preharvest applications of growth regulators and their effect on postharvest quality of table grapes during cold storage’, Postharvest Biol. Technol., 51, 183–192. Zoffoli, J.P., Latorre, B.A., Rodriguez, J., and Aguilera, J.M. (2009b), ‘Biological indicators to estimate the prevalence of gray mold and hairline cracks on table grapes cv. Thompson Seedless after cold storage’, Postharvest Biol. Technol., 52, 126–133. Zoffoli, J.P., Latorre, B.A., Rodriguez, E.J., and Aldunce, P. (1999), ‘Modified atmosphere packaging using chlorine gas generators to prevent Botrytis cinerea on table grapes’, Postharvest Biol. Technol., 15, 135–142. Zoffoli, J.P., Rodríguez, J., Mlikota Gabler, F., Smilanick, J.L., and Santiago, M.S. (2007), ‘Evaluation of sulfur dioxide emission from SO2-releasing plastic liners and their effectiveness to control postharvest gray mold on Thompson Seedless grapes’, 5th International Table Grape Symposium, Somerset West, South Africa, 14–16 November. Zoffoli J.P., Rodríguez, J. and Rodríguez, C. (2005), ‘Impacto del área de ventilada de la bolsa de embalaje en la calidad de poscosecha de la uva de mesa cultivares Thompson Seedless, Red Globe’, ACONEX (Chile), 88, 25–31. Zutahy, Y., Lichter, A., Kaplunov, T. and Lurie, S. (2008), ‘Extended storage of “Red Globe” grapes in modified SO2 generating pads’, Postharvest Biol. Technol., 50, 12–17.

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10 Guava (Psidium guajava L.) S.P. Singh, Curtin University of Technology, Australia

Abstract: Guava is a commercial fruit crop in many tropical and sub-tropical countries of the world. The fruit is a rich source of vitamins, minerals, fibre and dietary antioxidants. High perishability and susceptibility to physical damage, chilling injury, diseases and insect-pests are the major postharvest constraints of guava fruit. This chapter reviews the economic importance, postharvest physiology, maturity indices and effects of pre- and postharvest factors on guava fruit quality. Postharvest diseases, disorders and phytosanitary treatments are also reviewed. The chapter then discusses the harvest and postharvest handling procedures and methods of ripening and senescence control. The processing of guava fruit into fresh-cut and other processed products is also described. Key words: Psidium guajava, guava, maturity indices, postharvest quality, storage, processing.

10.1

Introduction

10.1.1 Origin, botany, morphology and structure Guava (Psidium guajava L.) is a member of the Myrtaceae family. The genus Psidium includes about 150 species, but Psidium guajava is the most important fruit of this genus (Pommer and Murakami, 2009). Guava is believed to have originated from an area extending from southern Mexico into or through Central America (Morton, 1987). The Spaniards and Portuguese are considered to be responsible for distribution of guava fruit to other parts of the world. The wide adaptability of the guava tree to various soils and climates may have facilitated its naturalization in tropical and sub-tropical regions worldwide. Botanically, guava fruit is a berry. Fruit are medium to large in size with an average weight of 100–250 g and 5–10 cm in diameter, and have four or five protruding floral remnants (sepals) at the apex (Fig. 10.1). Based on the cultivar, fruit can be spherical, ovoid or pyriform in shape. Fruit surface is rough to smooth, free of

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Fig. 10.1

Guava (Psidium guajava L.) fruit and leaves.

pubescence. Skin colour of immature and unripe fruit is mostly dark green which changes to yellowish-green, pale yellow and yellow with red blush on shoulders at ripe stage depending upon the cultivar. Pulp of ripe fruit is soft and juicy and is white, pink or salmon-red (see Plates XVIII and XIX in the colour section between pages 274 and 275). The seed cavity at the centre of fruit may be small to large with many hard to semi-hard seeds. The outer mesocarp of guava fruit is sandy or gritty in texture due to presence of stone cells (78%), which have strongly lignified cell walls, whereas endocarp tissue is rich in parenchyma cells and low in stone cells (Marcelin et al., 1993). Thick pulp, few seeds and stone cells, high sugar concentrations and typical aroma are the desirable fruit characteristics for table purposes. 10.1.2 Worldwide distribution and economic importance Guava is commercially cultivated in many tropical and sub-tropical countries of the world. India is the largest producer of guava fruit followed by Pakistan, Mexico and Brazil (Singh, 2010 and references therein). Egypt, Thailand, Colombia, Indonesia, Venezuela, Sudan, Bangladesh, Cuba, Vietnam, the US, Malaysia, Puerto Rico and Australia are among the other guava producing countries. A list of some popular guava cultivars grown in different countries is presented in Table 10.1. In response to increasing demand for fresh fruit and processed products, the

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Major guava cultivars in the producing countries of the world

Country

Cultivar(s)

India

‘Allahabad Safeda’, ‘Lucknow-49’ (syn. ‘Sardar’), ‘Banarsi Surkha’, ‘Apple Colour’, ‘Chittidar’, ‘Nasik’, ‘Dholka’, ‘Dharwar’, ‘Habshi’, ‘Seedless’, ‘Red Fleshed’, ‘Behat Coconut’, ‘Hisar Safeda’ ‘Safeda’, ‘Allahabad’, ‘Lucknow-49’, ‘Red Fleshed’, ‘Seedless’, ‘Karela’, ‘Apple Colour’ ‘Media China’, ‘Regional de Calvillo’, ‘China’, ‘La Labor’, ‘Acaponeta’, ‘Coyame’, ‘Kumagai’, ‘Paluma’, ‘Rica’, ‘White Ogawa’, ‘Red Ogawa’ ‘Paluma’, ‘Rica’, ‘Pedro Sato’, ‘Kumagai’, ‘Ogawa’, ‘Sassaoka’, ‘Yamamoto’, ‘Século XXI’ ‘Bassateen El Sabahia’, ‘Bassateen Edfina’, ‘Allahabad Safeda’ ‘Beaumont’, ‘Okinawa’, ‘Glom Sali’, ‘Glom Toon Klau’, ‘Khao Boon Soom’ ‘Puerto Rico’, ‘Rojo Africano’, ‘Extranjero’, ‘Trujillo’ ‘Indonesian Seedless’, ‘Indonesian White’ ‘Kampuchea’, ‘Jambu Kapri’, ‘Hong Kong Pink’, ‘Jambu Biji’, ‘Putih’, ‘Maha 65’, ‘Bentong Seedless’, ‘Taiwan Pear’, ‘Vietnamese’ ‘Swarupkathi’, ‘Mukundapuri’, ‘Kanchannagar’, ‘Kazi’ ‘Allahabad Safeda’, ‘Lucknow-49’, ‘Indonesian Seedless’, ‘Beaumont’, ‘Ka Hua Kula’, ‘GA-11’ ‘Beaumont’, ‘Ka Hua Kula’, ‘Hong Kong Pink’, ‘Indonesian Seedless’ ‘Redland’, ‘Supreme’, ‘Red Indian’, ‘Ruby X’, ‘Miami Red’, ‘Miami White’, ‘Blitch’, ‘Patillo’, ‘Webber’, ‘Rolfs’, ‘Hart’, ‘Detwiler’, ‘Turnbull’ ‘Fan Retief’, ‘Frank Malherbe’, ‘TS-G2’ ‘Xa Ly Nghe’, ‘Ruot Hong Da Lang’, ‘Xa Ly Don’

Pakistan Mexico Brazil Egypt Thailand Colombia Indonesia Malaysia Bangladesh Australia USA (Hawaii) USA (Mainland) South Africa Vietnam

Sources: Morton, 1987; Pommer and Murakami, 2009; Singh, 2010

production of guava has considerably increased in the current decade as the new plantations of improved varieties and hybrids are emerging. The increase in area and production of guava could be attributed to the breeding efforts in various countries. The international trade of fresh guavas is currently limited, but the processed products, such as juice, nectar, paste, puree and jam, are becoming increasingly popular in the European and North American markets. 10.1.3

Uses, nutritional value and health benefits

Guava has been used as a food crop and medicinal plant. Guava fruit has a sweetsour taste combined with a pleasant aroma. It is mainly consumed as fresh or processed into various products like fresh-cut salads, juice, nectar, paste, puree, concentrates, jam, jelly, candy bars, etc. Generally, white-fleshed cultivars are preferred for dessert and red-fleshed for processing. The extracts of roots, bark,

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leaves and fruit have been widely used for traditional medicinal purposes in Central America and Africa against diarrhoea, gastroenteritis and antibacterial colic pathogenic germs of the intestine (Pérez-Gutiérrez et al., 2008). Leaf extracts of guava have been widely researched for their antimicrobial properties and have diverse applications in curing various maladies. The pharmacological and clinical uses of guavas have been comprehensibly reviewed elsewhere (Pérez-Gutiérrez et al., 2008). Fresh guava fruit is low in calories and rich in several vitamins and minerals. According to the national nutrient database of the United States Department of Agriculture (USDA), the major nutritional components of fresh guava fruit per 100 g are: sugars 8.92 g; vitamin C 228.3 mg; vitamin A 624 IU; vitamin E 0.73 mg; vitamin K 2.6 μg; lycopene 5.2 mg (in red-fleshed cultivars only); potassium 417 mg; phosphorus 40 mg; magnesium 22 mg, and calcium 18 mg (USDA, 2010). It is an excellent source of antioxidants, such as ascorbic acid, carotenoids and phenols (Kondo et al., 2005; Lim et al., 2007), which are known to play an important role in the prevention of chronic and degenerative diseases. Similar to many other fruits, polyphenols contribute significantly to the higher antioxidant capacity of guavas. The presence of a high concentration of dietary fibre (48–49 % on dry matter basis) in the peel and pulp of guava fruit makes it a natural food product that meets requirements for consideration as an antioxidant dietary fibre (Jiménez-Escrig et al., 2001). The distribution of various healthpromoting phytochemicals also varies within the fruit and from cultivar to cultivar. Fruit skin is higher in ascorbic acid and phenols than flesh (Bashir and Abu-Goukh, 2003; Kondo et al., 2005; Lim et al., 2007). Generally, white-fleshed cultivars contain higher concentrations of ascorbic acid, phenols and sugars (sucrose, fructose and glucose) than red-fleshed ones (Bashir and Abu-Goukh, 2003; González-Aguilar et al., 2004); seeded cultivars have higher phenols and ascorbic acid than their seedless counterparts (Lim et al., 2007).

10.2

Fruit development and postharvest physiology

10.2.1 Fruit growth, development and maturation Flowering and fruiting in guava occurs continuously throughout the year under mild subtropical and tropical conditions. In subtropical climates of north India, guava flowers in summer, rainy and winter seasons, and thus produces fruit during rainy, winter and spring seasons, respectively (Rathore, 1976). Guava fruit shows a double sigmoidal growth curve (Rathore, 1976; Mercado-Silva et al., 1998). The growth period can be divided into three distinct phases: (1) rapid phase of growth extends for 45 to 60 days after anthesis; (2) relatively slow lasts for 30 to 60 days during which seeds become fully mature and hard; and (3) exponential phase lasts for 30 to 60 days and ends at fruit maturity (Rathore, 1976). During the last phase of growth, fruit show the highest increase in weight and diameter in addition to other changes such as decrease in hardness, chlorophyll and tannins. Other major biochemical changes during the final phase of growth

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include an increase in soluble solids concentration (SSC), titratable acidity and ascorbic acid (Rathore, 1976; Mercado-Silva et al., 1998; Singh and Jain, 2007). However, the length of each growth phase is strongly influenced by climatic conditions and cultivar type. For example, in Mexico, the number of days required for the ‘Media China’ cultivar to reach the ripe stage is 130 days during spring– summer and 190 days in autumn–winter season (Mercado-Silva et al., 1998). In north India, the growth of seeded fruit of ‘Allahabad Safeda’ during 30 and 105 days after pollination was greater than fruit of ‘Allahabad Seedless’ and it was mainly due to the higher levels of gibberellins in the former due to presence of seeds (Nagar and Rao, 1982). The seeded fruit grew faster and reached their largest diameter on the 120th day after pollination, while the seedless fruit at maturity were less than half the size of the seeded fruit. In general, guava fruit take about 100 to 150 days from full bloom to harvest. 10.2.2 Respiration and ethylene production Guavas are generally classified as a climacteric fruit (Akamine and Goo, 1979; Brown and Wills, 1983; Mercado-Silva et al., 1998; Singh and Pal, 2008a), but some cultivars are non-climacteric in nature (Azzolini et al., 2005). Respiration rate of fruit is influenced by many factors such as cultivar, season and maturity. For example, white-fleshed cultivars respire more slowly than pink-fleshed ones (Bashir and Abu-Goukh, 2003; Singh and Pal, 2008a). The postharvest climacteric peaks in respiration and ethylene production were observed after 4–5 days in spring–summer fruit compared with 7–8 days in autumn–winter fruit (MercadoSilva et al., 1998). During fruit ripening, ethylene production and respiration rates of fruit harvested at the full sized, pale green stage were higher than those harvested at small or medium dark green stage (Brown and Wills, 1983). Fruit harvested at advanced maturity reach their respiratory climacteric in 4–6 days accompanied by rapid changes in skin colour and flesh firmness. Like respiration, ethylene production behaviour of guava depends upon the cultivar, harvest maturity and storage conditions. Ethylene production rates increase during fruit ripening and reach a peak that may or may not coincide with the respiratory peak. Guava cultivars such as ‘Allahabad Safeda’, ‘Apple Colour’ and ‘Hisar Safeda’ produce higher amounts of ethylene than ‘Lucknow-49’ (Mondal et al., 2008; Singh and Pal, 2008a). It is suggested that the lower ethylene rates and higher concentrations of polyamines in ‘Lucknow-49’ are responsible for its better shelflife compared to ‘Hisar Safeda’. The increase in ethylene has been correlated with increased 1-aminocyclopropane-1-carboxlylic acid (ACC) oxidase activity during fruit ripening indicating ACC oxidase may be a limiting step in ethylene biosynthetic pathway in guava fruit because ACC content increased progressively throughout fruit ripening (Mondal et al., 2008). Guava fruit respond to the exogenous application of ethylene depending upon fruit maturity and climacteric or non-climacteric nature of the cultivar (Reyes and Paull, 1995; Azzolini et al., 2005). The exogenous application of ethylene, for example, enhanced changes in skin colour and softening in

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immature, green fruit of the ‘Beaumont’ cultivar, but did not affect the ripening behaviour of quarter-yellow fruit of this cultivar (Reyes and Paull, 1995), while ‘Pedro Sato’ guavas harvested at a mature, light green stage did not respond to postharvest ethylene treatment (Azzolini et al., 2005). However, postharvest exposure to 1-methylcyclopropene (1-MCP), an ethylene action inhibitor, inhibits ethylene production rate and delays fruit ripening in both climacteric and nonclimacteric type cultivars (Azzolini et al., 2005; Bassetto et al., 2005; Singh and Pal, 2008b). 10.2.3 Biochemical changes during fruit ripening During fruit ripening, chlorophyll content decreases and carotenoid content increases, causing skin colour to change from green to yellow (Jain et al., 2003). The intensity of red blush on fruit shoulders also increases in some cultivars. The flesh colour also changes to creamy white, yellow, pink or salmon red depending on the cultivar. The carotenoids contribute to the flesh colour of guava fruit; the relative amounts of different carotenoids determine the intensity of flesh colour. In general, total carotenoids concentrations increase during fruit ripening (Jain et al., 2003). Lycopene (50 μg/g) is the major carotenoid pigment in red fleshed guavas, in addition to the presence of β-carotene (3.7 μg/g) (Wilberg and Rodriguez-Amaya, 1995; Mercadante et al., 1999). In a Brazilian red guava cultivar ‘IAC-4’, 16 carotenoids have been identified which include lycopene, β-carotene, phytofluene, γ-carotene, β-cryptoxanthin, rubixanthin, cryptoflavin, lutein, and neochrome (Mercadante et al., 1999). During ripening, fruit softening in guava is accompanied by significant modifications in cell wall carbohydrates. Total pectin content, generally, increases initially and then declines at the overripe stage. The soluble pectins increase as the fruit ripening progresses. The concentrations of chelator-soluble-polyuronides and -carbohydrates also increase during fruit ripening. The levels of other cell wall carbohydrates such as cellulose, hemicellulose, lignin and starch decrease during fruit ripening (Jain et al., 2003). The rate of fruit softening may vary from cultivar to cultivar, but the extent of pectin solubilization was comparable in two guava cultivars: ‘Beaumont’, a rapid-softening cultivar, and ‘Kampuchea’, a slow-softening cultivar. ‘Beaumont’ guava took about 1.5 days to reach 50% of initial firmness at harvest, while ‘Kampuchea’ took about 24 days (Ali et al., 2004). The collective action of cell wall hydrolyzing enzymes, polygalacturonase (PG), pectin methylesterase (PME), β-galactosidase, (1→4)-β-glucanase and cellulase, causes significant textural changes in guava fruit. PG activity increases progressively during fruit ripening in guavas, while PME increases initially and then declines (Abu-Goukh and Bashir, 2003; Jain et al., 2003). A significant increase in activities of other enzymes like β-galactosidase, (1→4)-β-glucanase, and cellulase also contributes to the cell wall modifications (Abu-Goukh and Bashir, 2003; Ali et al., 2004). Fruit ripening in guava is accompanied by significant changes in biochemical composition. The concentrations of soluble solids and total sugars increase during

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fruit ripening in guavas (El Bulk et al., 1997; Bashir and Abu-Goukh, 2003; Singh and Pal, 2008a; Singh and Pal, 2008b). Generally, fructose is the predominant sugar in ripe guava, followed by glucose and sucrose. The individual sugar profiles vary from cultivar to cultivar (Wilson et al., 1982; El Bulk et al., 1997). In general, titratable acidity and total phenolics decrease during fruit ripening (Paull and Goo, 1983; Tandon et al., 1989; Bashir and Abu-Goukh, 2003; Singh and Pal, 2008b; Singh and Pal, 2009). Citric acid is the major organic acid, followed by malic and glycolic acids (Wilson et al., 1982). Ascorbic acid concentrations increase significantly during the initial stages of fruit ripening and then decrease with senescence (Rathore, 1976; El Bulk et al., 1997; Soares et al., 2007; Gomez and Lajolo, 2008). The increase in ascorbic acid during fruit ripening in guava has been associated with the increased activity of L-galactono-1,4-lactone dehydrogenase, a key enzyme in the ascorbic acid biosynthetic pathway. The activity of dehydroascorbate reductase, which acts to reduce dehydroascorbate into ascorbate, also increases during the initial stages of guava fruit ripening to compensate for increased oxidation of ascorbate by ascorbate peroxidase (Gomez and Lajolo, 2008). Guava fruit has a strong characteristic aroma due to esters and terpenes. In mature fruit, the esters (Z-3-hexenyl acetate, E-3-hexenyl acetate, ethyl hexanoate, and ethyl butanoate), 1,8-cineole, monoterpenes (myrcene and limonene) and sesquiterpenes (caryophyllene, α-humulene and β-bisabollene) are the predominant aroma compounds (MacLeod and Troconis 1982; Chyaui et al. 1992; Soares et al. 2007). The key aroma compounds of guava fruit contributing to a green, grassy odour note are (Z )-3-hexenal and, to a lesser extent, hexanal; 3-sulfanyl-1hexanol and 3-sulfanylhexyl acetate impart the sulphury, tropical note; and 4-hydroxy-2,5-dimethyl-3(2H)-furanone, ethyl butanoate and cinnamyl acetate predominantly account for the sweet, fruity and flowery aroma (Steinhaus et al., 2009). In general, the abundance of aroma-volatile compounds increases during fruit ripening.

10.3

Maturity indices

Harvesting at optimum stage is an important step to ensure the supply of a flavoursome and nutritious fruit to the consumer. Fruit flavour is significantly influenced by harvest maturity, and the advancement of fruit maturity leads to accumulation of sugars, increase in ascorbic acid, decrease in phenols and acids, and biosynthesis of aroma volatile compounds (El Bulk et al., 1997; Bashir and Abu-Goukh, 2003; Soares et al., 2007). Excessive delays in harvesting reduce the potential shelf-life of guava (Tandon et al., 1989). Changes in fruit skin colour and size have been recommended as the best harvest maturity indices (MercadoSilva et al., 1998; Singh and Pal, 2008a; Singh and Pal, 2008b). The change in fruit skin colour from dark green to light green coupled with attained fruit size are useful indices to determine harvest maturity. Other maturity indices such as specific gravity, chemical attributes and fruit detachment force have been found

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beneficial for determining the harvesting stage (Kumar and Hoda, 1974; Rathore, 1976; Paull and Goo, 1983; Tandon et al., 1989; Mercado-Silva et al., 1998). Specific gravity decreases during the final phase of fruit maturation in guava. The fruit quality and consumer acceptability of guava harvested at specific gravity 100 mm; 2: 351–450 g, 96–100 mm; 3: 251–350 g, 86–95 mm; 4: 201–250 g, 76–85 mm; 5: 151–200 g, 66–75 mm; 6: 101–150 g, 54–65 mm; 7: 61–100 g, 43–53 mm; 8: 35–60 g, 30–42 mm; 9: vitamin C depletion. The presence of nitrate accelerated all three processes without significantly affecting the Ea value. Tin dissolution, rather than depletion of vitamin C, appears to be the predominant factor limiting the shelf life of the product. It is estimated that appropriately processed jackfruit juice packaged in plain tinplate cans could keep well for 17 months at room temperature in the absence of nitrates. A further potential use of jackfruit is in the preparation of jam and jelly due to the presence of adequate pectin content and the visco-elastic properties of the pulp. Jams and jellies can be developed as conventional products and as low calorie products by incorporation of non-nutritive sweeteners in the formulation.

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Manimegalai et al. (2001) also described the development of jackfruit bars. The storage stability of the product when packaged in different packaging materials, i.e. polypropylene/metalized polyester-laminated pouches, was analysed, and the shelf stability was found to be six months at room temperature. The product showed better shelf-stability when packaged in specific laminated pouches than when wrapped in butter paper or packaged in polypropylene pouches. Jackfruit pulp can also be used in mixed fruit bars in combination with the pulp of other fruits such as mango and pineapple. Its visco-elastic properties can play a substantial role in producing an adequate texture for a mixed fruit bar. Frozen products Jackfruit bulbs are ideal for freezing due to their firm texture and ability to withstand the process. John and Narasimham (1998) described the quality characteristics of blast frozen and cryo-frozen ripe jackfruit bulbs. The bulbs were packaged in cans and subjected to blast/cryo-freezing for storage at −18 °C. After six months of storage, cryo-frozen samples showed a toughness value of 1.42 kg cm−2 compared to the initial value of 1.62. In blast frozen samples, the toughness value was 1.29 kg cm−2 indicating greater toughness retention in the case of cryo-frozen samples. Cryo-frozen products also showed better colour retention as well as higher sensory value than blast frozen bulbs after six months of storage. Products from immature jackfruit Compared with studies on value addition relating to the ripe fruit, immature jackfruit has drawn less attention. Immature jackfruit is popularly used in curry preparation on the Indian subcontinent, and John et al. (1993) reported the use of hurdle processing in stabilizing curry prepared from immature jackfruit. The hurdles applied included acidification, vacuum packaging and in-pack pasteurization. The hurdles were found to be adequate to render the product microbiologically safe, giving an overall shelf life of 120, 270 and 360 days at storage temperature of 28, 4 and −18 °C, respectively. Certain conventional practices are employed on the Indian subcontinent to produce pickles with extended shelf-life by immersing immature jackfruit in brine or vinegar. Immature jackfruit slices can also be subjected to dehydration to prepare dehydrated curry mixes. When powdered, immature jackfruit can be used as a flour extender, as is commonly the case with its close relative, the breadfruit. Kanzaki et al. (1997) described and established the phylogenetic relationship between jackfruit and breadfruit. By-products from jackfruit As already mentioned, there are several edible parts other than ripe bulbs within jackfruit. In ripe fruit, the seed and the unfertilized floral parts may also be eaten. Jackfruit seeds are rich in starch and when roasted are edible with a crisp texture. Ripe jackfruit seeds are also used in desserts or in culinary preparations. Jackfruit seed starch has a lower gelatinization temperature range than modified starch and requires less energy for gelatinization (Mukprasirt et al., 2004). The peak viscosity

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of jackfruit seed starch was lower than that of commercially modified starch and the same trend could be seen in the case of set back velocity, swelling power and solubility of jackfruit seed starch. Because of its high thermal and mechanical shear stability, jackfruit seed starch could be an ideal replacement for modified starches. Singh et al. (1991) described the functional properties and protein quality of jackfruit seed flour. The protein content in jackfruit seeds was found to be 16.3% with 89% protein digestibility. The high solubility of jackfruit seed in the acidic reagent indicated that the protein might be used in the formulations of acid foods such as protein-rich carbonated beverages. Kabir (1998) described the isolation of a lectin known as ‘jacalin’ for versatile application in immunobiological research. It is a tetrameric two-chain lectin combining a heavy α chain of 133 amino acids residues with a light β chain of 20–21 amino acids residues. The lectin is specific for α-O-glycoside of the disaccharide antigen (Gal β 1–3 GalNAc). The outer perianth and peel of jackfruit and the unfertilized floral parts are a rich source of pectin, which could be commercially manufactured for high quality pectin.

12.8

Conclusions

As a giant tropical compound fruit with excellent flavour and textural quality, jackfruit has the potential to become popular in the global market. Outside of certain parts of the world such as South-East Asia and Florida, jackfruit has not received a large amount of attention due to the lack of authentic vegetative propagation methods, meaning that jackfruit is only popularly found as a kitchen garden tree or in avenue plantations rather than in commercial orchards. There is an acute need to develop appropriate propagation technology based on micro-propagation methods, and to bring information about soil requirements, agronomic practices, pest management and postharvest handling techniques to a wider audience. Modified atmosphere storage of jackfruit bulbs needs to be further investigated, in particular regarding the use of antifog film wraps and the application of active MA packaging methods by micro and macro climatic regulation of storage atmospheres. One of the foremost requirements in the value addition of jackfruit is the development of primary processing technologies such as thermal processing, freezing and chemical preservation of pulp in bulk containers. The marketing of bulbs stabilized by hurdle processing is very promising, as the product has a pleasant taste and an attractive colour. Jackfruit should not be considered suitable only for the poor, as its nutritional and sensory quality is competitive enough to earn it a place in the global market. Future work on nutrigenomics could potentially help in improving jackfruit quality for the satisfaction of different consumer sectors around the world.

12.9

References

Balbach A and Boarim D S F (1992). As frutas na medicina natural, Sao Paulo: Editora Missionaria.

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Berry S K and Kalra C L (1988). Chemistry and technology of jackfruit (Artocarpus heterophyllus) – A review. Ind Food Pack 42(3), 62–76. Bhatia B S, Siddappa G S and Lal G (1955). Composition and nutritive value of jackfruit. Ind J Agri Sci 25, 303–306. Bobbio F D, El-Dash A A, Bobbio P A and Rodriguies L R (1978). Isolation and characterization of the physico-chemical properties of the starch of jackfruit seeds (Artocarpus heterophyllus). Cereal Chem 25, 505–511. Che Man Y B and Sin Ku K (1997). Processing and consumer acceptance of fruit leather from the unfertilized floral parts of jackfruit. J Sci Food Agri 25(1), 102–108. Che Man Y B and Taufik (1995). Development of stability of jackfruit leather. Trop Sci 25 245–250. Chowdhury F A, Raman M A and Mian A J (1997). Distribution of free sugars and fatty acids in jackfruit (Artocarpus heterophyllus). Food Chem 25 (1), 25–28. Devaraj T L (1985). Speaking of Ayurvedic remedies for common disease, New Delhi: Sterling. Dutta S (1956). Cultivation of jack fruit in Assam. Ind J Hort, 25 (4), 189–197. Elevitch C R and Manner H I (2006). Artocarpus heterophyllus (jackfruit), ver. 1.1v. In Elevitch C R (ed.) Species Profiles for Pacific Island Agroforestry, Permanent Agriculture Resources, Hawaii. Available from: http://www.agroforestry.net/tti/A.heterophyllusjackfruit.pdf [Accessed 18 June 2010] Ferrao J E M (1999). Fruiticultura tropical: especies com frutos comestiveis, Vol 1. Lisbon: Instituto de Investigacao Cientifica Tropical. Fosberg F R, Sachet M and Oliver R (1979). A geographical checklist of the Micronesian dicotyledonae. Micronesia, 25, 1–295. Giraldo-Zuniga A D, Arevalo Pinedo A, Rodrigues R M, Lima C S S and Feitosa A C (2006). Kinetic drying experimental data and mathematical model for jackfruit (Artocarpus integrifolia) slices. Ciencia y Technologia Alimentaria- J Food, 25, 89–92. Jagadeesh S L, Hegde L, Swamy G S K, Reddy B S, Gorbal K et al. (2006). Influence of physico-chemical parameters of jackfruit bulbs on chips quality. Annual Conference of the Canadian Society for Bioengineering, Edmonton Alberta, July 16–19. Jagadeesh S L, Reddy B S, Basavaraj N, Swamy G S K, Gorbal K et al. (2007a). Inter tree variability for fruit quality in jackfruit selections of Western Ghats of India. Sci Hort 25, 382–387. Jayaraman K S (1998). Development of intermediate moisture tropical fruit and vegetable products. Technological problems and prospects. In Seow C C (Ed.), Food Preservation by Moisture Control, Elsevier Applied Science, Essex, UK, pp. 175. John P J and Narasimham P (1993). Processing and evaluation of carbonated beverage from jackfruit waste (Artocarp+us heterophyllus). J Food Proce Preserv 25(6), 373–380. John P J and Narasimham P (1998). Quality of blast-frozen and cryo-frozen ripe jackfruit bulbs. J Food Sci Technol 25, 59–61. John P J, Balasubramanyam N and Narasimham P (1993). Effect of packaging, processing, and storage conditions on the quality of raw jackfruit curry in flexible pouches. J Food Proce Preserv 25(2), 109–118. Kabir S (1998). Jacalin: a jackfruit (Artocarpus heterophyllus) seed-derived lectin of versatile applications in immunobiological research. J Imm Methods, 25, 193–211. Kanzaki S, Yonemori K, Sugiura A and Subhadrabandhu S (1997). Phylogenetic relationships between the jackfruit, the breadfruit and nine other Artocarpus spp. from RFLP analysis of an amplified region of cpDNA. Sci Horti 25 (1), 57–66. Kays S J (1991). Development of plants and plant parts. In: Postharvest physiology of perishable plant products. AVI Publishing, Van Nostrand Reinhold, New York, 257–333. Krishnaveni A, Manimegalai G and Saravanakumar R (2001). Storage stability of jackfruit (Artocarpus heterophyllus) RTS beverage. J Food Sci Technol 25(6), 601–602.

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Kumar G S, Appukuttan P S and Basu D (1982). α-D-Galactose- specific lectin from jackfruit (Artocarpus integra) seed. J Biosci 25, 257. Leistner L (1994). Principles and application of hurdle technology. In Gould G W (Ed.), New and Emerging Technologies, Blackie Academic and Professional Glasgow. Maia J G S, Andrade E H A, and Zoghbi M G B (2004). Aroma volatiles from two fruit varieties of jackfruit (Artocarpus heterophyllus Lam.). Food Chem 25, 195–197. Maiti C S, Wangchu L and Mitra S K (2002). Genetic divergence in jackfruit (Artocarpus heterophyllus Lam.). Ind J Genet Plant Breed 25(4), 369–370. Manimegalai G, Krishnaveni A and Saravanakumar R (2001). Processing and preservation of jackfruit (Artocarpus heterophyllus L.) bar (thandra). J Food Sci Technol 25(5), 529–531. Moriguchi T, Ischizawa Y and Sanada T (1990). Différences in sugar composition in Prunus persica fruit and the classification of the principal components. Engei Gakkai Zasshi, 25 (21), 307–312. Morton J F (1987). Jackfruit. In: J F Morton (Ed.), Fruits of Warm Climates. Florida Flair Books, Miami, FL, pp. 58–64. Morton J F (1965). The jackfruit (Artocarpus heterophyllus Lam.): Its culture, varieties and utilization. Florida State Horticultural Society, 336–344. Mukherjee B (1993). Traditional medicine, New Delhi: Mohan Primalani for Oxford and IBH Publishing Co. Mukprasirt A and Sajjaanantakul K (2004). Physicochemical properties of flour and starch from jackfruit seeds (Artocarpus heterophyllus Lam.) compared with modified starches. Int J Food Sci Technol 25(3), 271–276. Munasque V S and Mendoza D B (1990). Development physiology and ripening behaviour of Senorita banana (Musa sp L) fruits. ASEAN Food J 25, 152–157. Nahar N, Mosihuzzaman M and Dey S K (1993). Analysis of free sugar and dietary fibre of some vegetables of Bangladesh. Food Chem 25, 397–400. Olias J M, Sanz C, Rios J J and Perez A G (1995). Substrates specificity of alcohol acyltransferases from strawberry and banana fruits. In: Fruit flavours. ACS Symposium Series, vol. 596, pp. 135–141. Ong B T, Nazimah S A H, Osman A, Que S Y, Voon Y Y et al. (2006). Chemical and flavour changes in jackfruit (Artocarpus heterophyllus Lam.) cultivar J3 during ripening. Postharv Biol Technol 25, 279–286. Pua C K, Sheikh Abd Hamid N, Rusul G and Abd Rahman R (2007). Production of drumdried jackfruit (Artocarpus heterophyllus) powder with different concentration of soy lecithin and gum arabic. J Food Eng 25(2), 630–636. Punan M S, Rahman A S A, Nor L M, Muda P, Sapii A T et al. (2000). Establishment of a quality assurance system for minimally processed jackfruit. In Quality assurance in agricultural produce. Eds. Johnson G I, To L V, Duc N G and Webb M C. ACIAR Proceedings, 100, MARDI, Kuala Lumpur, Malaysia, 115–122. Rahman A K M M, Huq E, Mian A J, and Chesson A (1995). Microscopic and chemical changes occurring during the ripening of two forms of jackfruit (Artocarpus heterophyllus L.). Food Chem 25, 405–410. Rahman M A, Nahar N, Jabbar M A and Mosihuzzaman M (1999). Variation of carbohydrate composition of two forms of fruit from jack tree (Artocarpus heterophyllus L.) with maturity and climatic conditions. Food Chem 25, 91–97. Rasmussen P (1983). Identification of volatile components of jackfruit by gas chromatography/mass spectrometry by two different columns. Analytic Chem 25, 1331–1335. Reaves R M (1959). Histological and histochemical changes in the developing and ripening of peaches. Am J Bot 25, 214–248. Rees T A P, Dixon W L, Pollock C J and Franks F (1981). Low temperature sweetening of higher plants. In: Friend J and Robert M J C (Eds.), Recent Advances in the Biochemistry of Fruits and Vegetables. Academic Press, London, New York, pp. 41–60.

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Reyes V G (1997). Factors limiting shelf life and quality of minimally processed fruits and vegetables. The Association of Southeast Asian Nations (ASEAN)–Australia Economic Cooperation Program III: Quality Assurance Systems for ASEAN Fruits (QASAF) Workshop on Minimal Processing of Tropical Fruits, Kuala Lumpur, 21–23 October 1997. Brisbane, Palamere Pty Ltd. Samaddar H N (1985). Jackfruit. In: Bose T K (Ed.), Fruits of India: Tropical and Subtropical. Naya Prokash, Calcutta, 487–497. Saxena A, Bawa A S and Raju P S (2008). Use of modified atmosphere packaging to extend shelf life of minimally processed jackfruit (Artocarpus heterophyllus L.) bulbs. J Food Eng 25 (4), 455–466. Saxena A, Bawa A S and Raju P S (2009a). Phytochemical changes in fresh-cut jackfruit (Artocarpus heterophyllus L.) bulbs during modified atmosphere storage. Food Chem 25, 1443–1449. Saxena A, Bawa A S and Raju P S (2009b). Effect of minimal processing on quality of jackfruit (Artocarpus heterophyllus L.) bulbs using response surface methodology. Food Bioproc Technol DOI: 10.1007/s11947-009-0276-x. Saxena A, Bawa A S and Raju P S (2009c). Optimization of a multitarget preservation technique for jackfruit (Artocarpus heterophyllus L.) bulbs. J Food Eng 25 (1), 18–28. Saxena A, Maity T, Raju P S, and Bawa A S (2010). Degradation kinetics of color and total carotenoids in jackfruit (Artocarpus heterophyllus) bulb slices during hot air drying. Food Bioproc Technol DOI: 10.1007/s11947-010-0409-2. Selvaraj Y and Pal D K (1989). Biochemical changes during the ripening of jackfruit (Artocarpus heterophyllus L.). J Food Sci Technol 25 (6), 304–307. Sen Gupta U K and Rao C V N (1963). The pectic acid from the pulp of jackfruit (Artocarpus Integrifolia). I. Methylation studies. Bul Chem Soc Japan 25 (12), pp.1683–1688. Seow C C and Shanmugam G (1992). Storage stability of canned jackfruit (Artocarpus heterophyllus) juice at tropical temperature. J Food Sci Technol 25, 371–374. Sharaf A and El-Saadany S S (1987). Biochemical studies on guava fruits during different maturity stages. Chem Mikrobiol Technol Lebensm 25, 145–149. Singh A, Kumar S and Singh I S (1991). Functional properties of jackfruit seed flour. Lebens Wiss Technol 25 (4), 373–374. Soepadmo E (1992). Artocarpus heterophyllus Lam. In: Verheij E W M and Coronel R E (Eds.). Plant Resources of South East Asia 2. Edible Fruits and Nuts. PROSEA, Bogor, Indonesia. Sword G, Bobbio P A and Hunter G L K (1978). A research note: volatile constituents of jackfruit (Artocarpus heterophyllus). J Food Sci 25, 639–640. The Wealth of India (1985). Raw Material (revised), National Institute of Science Communication and Information Resources (NISCAIR), Council of Scientific & Industrial Research (CSIR), New Delhi, Vol 1: A, p. 447. Ukkuru M P and Pandey S (2006). Value added products from jackfruit. Proces Food Indust, July 2006, 36–37. Vibhakara H S (2007). Studies on the stabilization of some fruits and vegetables using multitarget preservation. Ph.D. thesis, University of Mysore, Mysore, India. Wiley C R (1994). Minimally processed refrigerated fruits and vegetables. New York: Chapman & Hall, pp. 66–127. Wills R B H, Lim J S K and Greenfield H (1986). Composition of Australian food. (Vol 31). Tropical and subtropical fruit. Food Tech Aust 25, 118–123. Wong K C and Tie D Y (1992). Volatile constituents of durian (Durio zibethinus Murr.). Flav Frag J 25, 79–83. http://www.traditionaltree.org. Artocarpus heterophyllus, In Species Profiles for Pacific Island Agroforestry, Ed. Elevitch C R and Manner, H I. April 2006.

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13 Chinese jujube (Ziziphus jujuba Mill.) and Indian jujube (Ziziphus mauritiana Lam.) J. P. Sheng and L. Shen, China Agricultural University, China

Abstract: Jujube fruits with high nutritional and medical value are consumed worldwide as fresh and dry fruit. This chapter discusses the origin and importance of the Chinese jujube (Ziziphus jujuba Mill.) and the Indian jujube (Ziziphus mauritiana Lam.), and describes their postharvest physiology, postharvest handling and storage, postharvest disorders, pathology, associated entomology and processing. Key words: jujube, storage, processing, postharvest physiology, disorder.

13.1

Introduction

13.1.1 Origin, botany and morphology Jujube is the common name for any of a genus of evergreen and deciduous shrubs and trees of the buckthorn family, classified as the genus Ziziphus of the family Rhamnaceae and order Rhamnales. The Rhamnaceae family comprises 50 genera and more than 600 species (Bailey, 1947) of which the species Z. jujuba Mill (Chinese jujube) and Z. mauritiana Lam. (called Indian jujube or ber) are the most important in terms of distribution and economic significance. Plants of the genus have small, regular flowers that produce drupaceous fruits. They are grown in tropical and subtropical regions all over the world. They are widespread in the Mediterranean region, Africa, Australia and tropical America (Pawlowska et al., 2009). Some kinds of jujube such as Chinese jujube are native to warm regions of Eurasia, such as China, Korea and parts of southeastern Africa (Lin and Cheng, 1995). The species Z. jujuba Mill (Chinese jujube) is indigenous to China, where its history of cultivation goes back over 4000 years. It has been widely planted in reforested areas within the Yellow River valley, chosen as a species compatible with the present ecology and economy (Yan and Gao, 2002). There are many varieties of

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Chinese jujube in different regions, with quite different colors, shapes, sizes and nutritional contents. (See Plate XXIII in the color section between pages 274 and 275.) The major varieties for Z. jujuba are ‘Jinsixiaozao’, ‘Junzao’, ‘Dongzao’, ‘Lingzao’, ‘Jianzao’, ‘Xuezao’, ‘Sanbianhongzao’, ‘Fangchuizao’, ‘Budaizao’, etc. Some varieties are suitable for fresh use, while some are better for processing as dried jujube. China produces about 90% of the world’s jujubes for food and pharmaceutical applications (Yan and Gao, 2002). Chinese production itself has risen from 1.1 million tonnes in 1998 to 2.0 million tonnes in 2006 (Li et al., 2005). Much of the annual Chinese jujube production is consumed in fresh and dried forms; therefore, there have been numerous studies on the storage and processing of Chinese jujube in order to enhance its quality. The major cultivars of Z. mauritiana Lam. are ‘Katha’, ‘Bagwari’, ‘Umran’, ‘Chhuhara’, ‘Illaichi’, ‘Karaka’, ‘Mundia’ ‘Murhra’ and ‘Narma’. In India, the ripe fruits are mostly consumed raw, but are sometimes stewed, whereas slightly under-ripe fruits are candied. Residents of Southeast Asia eat the unripe fruits with salt. Ripe fruits crushed in water are a very popular cold drink, or alternatively, the ripe fruits are preserved by sun-drying and a powder is prepared for out-of-season purposes. Acidic types of jujube are used for pickling or for chutneys (Pareek et al., 2009). In China and Africa, the dried and fermented pulp is pressed into cakes resembling gingerbread (Pawlowska et al., 2009; Shi and Qi, 2002). Jujube is also grown as an ornamental plant in southwestern regions of the United States. 13.1.2 Nutritional value and health benefits Chinese jujube fruit is a favored and profitable fruit, and is much admired for its high nutritional value. It is commonly used as a food, food additive and flavorant. The Ziziphus species are commonly used in folk medicine for the treatment of various diseases such as digestive disorders, general weakness, liver complaints, obesity, urinary troubles, diabetes, skin infections, loss of appetite, fever, pharyngitis, bronchitis, anemia, diarrhea and insomnia (Han and Park, 1996; Kirtikar and Basu, 1975). For thousands of years, it has been commonly used as a crude drug in traditional Chinese medicine for analeptic, palliative and antibechic purposes. According to analysis by the Food and Nutrition Board, National Research Council (1989), the average dried Z. jujuba sugar content is 50.3 ~ 86.9 g kg−1, while the protein content is 3.3 ~ 4.0 g kg−1, and fat content is 0.2 ~ 0.4 g kg−1 (dried weight basis). Chinese jujube also contains 18 kinds of amino acids, including eight essential amino acids, and is rich in vitamins and minerals. The ascorbic acid content is up to 500 ~ 800 mg in 100 g of fresh Z. jujuba, such as Chinese winter jujube (also called Dongzao). This level is higher than that of kiwi fruit (1~2 times), citrus (7~10 times) and apples (100 times) (Table 13.1). The species Z. mauritiana Lam. is mainly consumed fresh, has an ascorbic acid content of 65~280 mg 100 g−1 and is rich in essential minerals and carbohydrates (Table 13.1). The physico-chemical characteristics of major Indian jujube cultivars are introduced by Pawlowska et al. (2009). Grading standards for the fruit are shown in Tables 13.2 and 13.3.

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Sanbianhongzao

Dongzao

Red 84.85 77.93 1.51 5.24 0.39 4.75 17.38 2.41 375.00 72.30 45.6 51.20 6.42

Red 80.86

60.24 1.46 7.18 1.02 6.86

20.98

2.78 458.00

59.30

91.0

36.50 6.93

7.90

24.60

118

105.00

3.01 201.00

21.09

0.71 6.43

5.83

1.07

58.73

Red 82.17

6.01

42.10

76.9

79.70

2.56 244.00

22.52

0.65 6.60

5.56

0.57

67.32

Red 85.63

1.99

0.16

15.2

34.20

– 298.00

74.08

– 0.307

–

1.37

7.88

Red –

0.76–1.80

0.30

25.60

26.80

5.83 0.47–1.57

81.6–83

1.25 2.63

–

0.60

1.4–6.2

(Continued)

Greenish yellow 18.0–23.0

Ziziphus jujuba Lam.

Junzao

Jinsixiaozao

Jianzao

Indian jujube

Chinese jujube

Yazao

Nutrition content of Chinese jujube and Indian jujube

Appearance Red Carbohydrate 81.62 (mg100 g−1 ·DW) Reducing sugar 57.61 (mg/100 g−1 ·DW) Soluble fibre 2.79 (mg1001g·DW) Insoluble fibre 6.11 (mg100 g−1·DW) 0.37 Lipid (mg100−1g·DW) 5.01 Protein (mg100 g−1·DW) Moisture 18.99 (mg100 g−1·DW) Ash (mg100 g−1·DW) 2.26 Potassium 79.20 (mg100 g−1·FW) Phosphorus 110.00 (mg100 g−1·FW) 65.20 Calcium (mg100 g−1·FW) Manganese 39.70 (mg100 g−1·FW) 4.68 Iron (mg100 g−1·FW)

Component

Table 13.1

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Continued

Junzao

Sanbianhongzao

Dongzao

0.47 0.42 0.09 0.05 203.00 8.36 794.00

0.63 0.27 0.04 0.07

192.00 8.53

1025.00

Sources: Li et al., 2007; Sheng et al., 2003; Xu and Wu, 2009; He et al., 2002

6.21

7.61

563.00

7.01

296.00

0.09

0.06

0.42 0.31

5.96

342.00

5.18

315.00

0.05

0.05

0.35 0.19

3.22

–

–

379.40

–

–

0.16 0.07

15.2

–

–

280.00

0.024

0.016

3.00 0.80

0.02–0.05

Ziziphus jujuba Lam.

Jianzao

Jinsixiaozao

Yazao

Indian jujube

Chinese jujube

Sodium 6.34 (mg100 g−1·FW) Zinc (mg 100 g−1·FW) 0.55 Copper (mg 0.26 100 g−1·FW) Thiamine (mg 0.05 100 g−1·FW) Riboflavin (mg 0.07 100 g−1·FW) 359.00 Vitamin C (mg 100 g−1·FW) Phenolic content GAE 7.42 (mg g−1) Antioxidant capacity 1173.00 FRAPA (μmol g−1)

Component

Table 13.1

Chinese jujube and Indian jujube

303

Table 13.2 Grading standard for dry red jujube (Zhang and Li, 2007) with permission of the authors Grade

Shape and size

Quality

Top

Uniform size (≤300 fruits per kg) and shape, owned cultivar characters

Plump flesh, bright red, dryness, impurity ≤0.5%

1

2

3

Mechanical injury and Moisture blemish content

No mildewed, serous part, immature, diseased and wormy fruits, skin crack and oiled skin spot fruit ≤3%. Uniform size (≤360 Plump flesh, No mildewed, serous fruits per kg) and bright red, part, immature and shape, owned dryness, impurity diseased fruits. Skin cultivar characters ≤0.5% crack, oiled skin spot or wormy fruit ≤5%. Uniform size (≤420 Plump flesh, No mildewed and fruits per kg) and bright red, serous part fruits. shape, owned dryness, impurity Diseased, wormy, skin cultivar characters ≤0.5% crack, oiled skin spot or dried immature fruit ≤10% and diseased and wormy fruit ≤5% Fruit with normal Fruit flesh uneven, No mildewed fruit, shape and cultivar fruit with uneven serous part, diseased, characters bright red ≤10%, skin crack, oiled skin dryness, impurity spot or dried immature ≤0.5% fruit ≤15% and diseased and wormy fruit ≤5%

≤28% of Ziziphus jujuba Mill. cv. Jinsixiaozao

≤28% of Ziziphus jujuba Mill. cv. Jinsixiaozao ≤28% of Ziziphus jujuba Mill. cv. Jinsixiaozao

≤28% of Ziziphus jujuba Mill. cv. Jinsixiaozao

Table 13.3 Grading standard for Dongzao jujube (Zhang and Li, 2007) with permission of the authors Grade

1

2

3

Weight

≥20 g per fruit

16 ~20 g per fruit

10 ~16 g per fruit

Shape

Nearly spherical and uniform

Nearly spherical and uniform

Nearly spherical

Defects

No

No disease and pest fruit, No disease and pest crevasse fruit ≤3% fruit, crevasse fruit ≤5%

Color

Red and brightness, tinctorial area >30%

Red and brightness, tinctorial area >30%

Taste

Crisp, tender and juicy, Crisp, tender and juicy, sweet and acidulous, sweet and acidulous, delicious, no residue delicious, no residue

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Red and brightness, tinctorial area >30% Crisp, juicy, sweet and acidulous, delicious, no residue

304

13.2

Postharvest biology and technology of tropical and subtropical fruits

Ripening behavior and postharvest physiology

13.2.1 Ripening behavior During the growth and development process, a series of changes take place in the size, shape and color of jujube fruit. For Chinese jujube, most varieties mature from middle-late September to early October. The stages of Chinese jujube maturity can be divided into the white maturity stage, crisp ripe stage and the ripening stage (Geng, 1995), as described below. The white maturity stage is characterized by the fruit having an essentially fixed size and shape. In this mature stage, the green peel color subsides, and the fruit takes on a green-white or milky-white color. The flesh of the fruit is soft, and the fruit juice and sugar content are low. Therefore, the jujube in the white maturity stage is suitable for processing into preserved fruit. The crisp ripe stage is characterized by a half-red or wholly-red fruit, a crisp flesh texture, higher juice levels, and a sharp increase in sugar content. Fruit at this stage is used for making fresh cookies and is processed into wine. The ripening stage is characterized by a more deeply-red pericarp and yellowish-brown flesh which adheres closely to the nucleus. As jujube fruit at this stage is fully mature, its products have a high dry weight, a heavy and dark color, a full and flexible pulp, and are of good quality for eating. For each cultivar, the requirements for fruit growth and development can be calculated in terms of degree-days. In general, the harvest period in northern India is mid-February to March for cultivar ‘Gola’, mid-March to the last week of March for cultivar ‘Kaithli’, and March to April for cultivar ‘Umran’. The periods of availability of jujube fruits in India vary from December to March, depending on climatic conditions. Therefore, the degree-days required for maturity should be computed for different regions (Pawlowska et al., 2009). The best time for eating fresh is when the fruit is red; if the color becomes dark red, the fruit may be overripe and susceptible to decay.

13.2.2 Ethylene and CO2 evolution rates The various Z. jujuba cultivars may differ in their patterns of respiration and ethylene production. The storage life of Chinese jujube is primarily related to the fruit respiration rate, and does not correlate closely with the ethylene production rate (Kader et al., 1982). Some cultivars such as ‘Dazao’ and ‘Yuanzao’ are considered to be non-climacteric (Kader et al., 1982; Lu et al., 1993). Shen et al. (2004) reported that the respiration rate and ethylene production of ‘Dongzao’ jujube at 4°C and 20°C each exhibited increasing tendencies with extension of storage time, but that no apparent peaks of respiration or ethylene production were detected. This suggests that ‘Dongzao’ jujube fruit is non-climacteric. In contrast, Jiang and Sheng (2003) found that the rates of respiration and ethylene production of ‘Jins’ jujube during storage initially increased, then reached respective peaks before finally decreasing rapidly, and were further promoted when the fruit was exposed to ethylene. These observations suggest that ‘Jins’ cv.

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is climacteric. At present, researchers have diverse opinions regarding the patterns of respiration and ethylene production which differ among the various cultivars of Chinese jujube. Pawlowska et al. (2009) found that Indian jujube fruit has a high respiration rate and a climacteric respiration pattern, and reaches its prime eating quality at the climacteric peak. They also reported that jujube fruit produces high amounts of ethylene and responds to exogenous ethylene treatment as measured by changes in skin color, juice color and composition. Cultivar ‘Zaytoni’ is classed as climacteric on the basis of its respiration rate and ethylene production during postharvest periods, with the peaks of CO2 and ethylene production occurring simultaneously (Muay’ed et al., 2002) In the ‘Kaithli’, ‘Rashmi’, ‘Umran’, ‘Ponda’ and ‘ZG-3’ cultivars, the rate of respiration increases gradually and reaches its peak when the fruits have attained a chocolate-tinged color, indicating the late-peaking climacteric nature of these fruits. 13.2.3 Treatments to reduce respiration and ethylene rates Keeping a low rate of respiration rate and ethylene production is key to securing long shelf-life of Chinese jujube and Indian jujube fruit. The main methods used commercially are as follows. Low temperature Temperature is the most important environmental factor affecting respiration and ethylene production rates of jujube fruits. Research by Qu (1985) suggests that storage effects and temperature have a close relationship. Temperature directly affects the respiration rate; hence, proper temperature control to suppress the metabolic activity of fruits is the most basic requirement for storage of jujube fruit. Furthermore, Wu et al. (2001) have shown that low temperature can suppress Chinese jujube fruit respiration and maintain low-level metabolism; jujube fruit at room temperature (20°C) has a high respiration rate, while at 0°C the respiration rate is low, and the respiration rate on the seventh day is only 3.5% of that of the first day. Low pressure Wang et al. (2003) found that low-pressure storage led to a slowing down of respiration in jujube fruit, and inhibited ascorbic acid oxidase (AAO) activity. Under these low pressure conditions, loss of hardness and color changes in the fresh fruit were also significantly inhibited. 1-Methylcyclopropene (1-MCP) Ethylene plays an important role in ripening and senescence of various fruits, vegetables and flowers (Abeles et al., 1992). The compound 1-MCP is a highly promising compound among several recently developed inhibitors of ethylene actions, and has been shown to prevent ethylene-induced effects in various ornamentals, fruits and vegetables (Serek et al., 1995; Sisler and Serek, 1997; Fan and Mattheis, 2000).

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Jiang and Sheng (2003) found that jujube fruit ripening was significantly inhibited by 1-MCP. Unlike the control (fruit not exposed to 1-MCP), Chinese jujube fruit treated with 1-MCP did not exhibit a significant climacteric dependency in terms of respiration and ethylene production. In addition, the effects of exogenous ethylene on fruit ripening of ‘Jins’ cv. were also effectively overcome by 1-MCP treatment. Storage of ‘Dongzao and the effects of 1-MCP treatment on jujube fruit quality during storage were also studied by Sheng et al. (2003) who found that 1-MCP did not alter the trends in ethylene production or respiration rate, but did significantly reduce the total amount of ethylene production and the respiration rate. Gibberellic acid (GA) Compared with the actions of ethylene, GA is known to be effective in retarding leaf senescence, chlorophyll loss of citrus fruit peel and softening of peaches (Martinez, 2000). It is not known how GA regulates ripening of jujube fruit. However, Jiang and Sheng (2003) found that GA delayed the decreases in firmness and ascorbic acid levels, and reduced the level of ethanol. Furthermore, it was observed that the combination of GA + 1-MCP yielded additional beneficial effects in inhibiting ripening of the Chinese jujube. Liu (2009) also found that GA treatment delayed the rapid accumulation of malondialdehyde (MDA) and damage to the membrane system in Zhongning yuan zao jujube (Liu, 2009). Nitric oxide (NO) There is increasing evidence that NO can react with metal ions or sulphydryl groups in proteins (David et al., 2005; Koppenol, 1998). As a signal transmitter of cells, NO can not only play an important role in the physiology, biochemistry, pathology and pharmacology of the circulatory, respiratory, digestive, endocrine, nervous and immune system in humans and animals, but can also regulate the processes of growth, disease resistance and stress tolerance in plants. Exogenous NO treatment can postpone ripening and senescence and prolong the storage life of horticultural products such as strawberry and green pepper (Zhu el al., 2005; Cheng et al., 2005). Sun and Liu (2007) found that 20 pL.L−1 NO could mitigate the injurious effects of ethanol on ‘Dongzao’ and effectively delay the browning and softening of fruits during storage. Calcium Calcium ions can help maintain the structure and function of cell walls, which affects fruit hardness. Treatment with exogenous calcium can increase the calcium levels in fruit, decrease the respiration rate and polymethylgalacturonase (PG) activity, and reduce ethylene production and pectin degradation. As a result, it can help maintain fruit hardness, reduce the incidence of disease in storage, and finally, delay senescence after harvest, as is the case in ‘Dongzao’ fruit (Chen, 1984; Wu et al., 2001). Further information on calcium treatments can be found in section 13.5.2 and section 13.6.4.

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13.2.4 Artificial ripening Jiang and Sheng (2003) found that the firmness of jujube fruit decreased significantly with exposure to an increasing ethylene concentration from 0 to 10 μl L−1, while the level of soluble solids increased. This result suggests that ripening of jujube fruit was enhanced by ethylene. Furthermore, Yu (1997) found that ethephon treatment could promote the ripening of fresh jujube fruit, enhancing formation of the red color and improving the fruit quality. The content of ascorbic acid and sugar was found to be increased, while that of other acids was decreased. Abbas (1994) also found that ethephon treatment (500 μL.L−1) could advance green jujube maturity by increasing the TSS and ascorbic acid content, and reducing TA content. Currently, ethylene or ethephon are used for artificial ripening of some fruits, and as long as the amounts used are controlled within the safe maximum levels of the states’ standard guidelines, ethylene is safe for consumers. Abscisic acid (ABA) is one of the main factors causing softness and senescence of jujubes, and increased ABA content can decrease the sucrose content and speed up fruit senescence (Zhang, 2000). Compared to control, ABA was found to increase the rate of production of superoxide anion in ‘Dongzao’ jujube during storage, promote the accumulation of MDA and H2O2, hasten the activity peaks of catalase (CAT), polyphenol oxidase (PPO) and peroxidase (POD), increase AAO activity and sharply decrease the total phenol content. Treatment of ‘Lizao’ jujube with indole-3-acetic acid (IAA), ethephon, and ABA enhanced ethylene production in the initial stages after harvest, increased the MDA content and lipoxygenase (LOX) activity, accelerated the softening, and decreased the ascorbic acid content and sound fruit rate. The effects of ABA were particularly marked (Yan, 2004).

13.3

Postharvest pathology and entomology

13.3.1 An introduction to postharvest pathology Postharvest pathology is one of the most important factors affecting the commercial value of jujube fruit. About 80% of jujube fruit develop disease when stored at room temperature for approximately 10 days, but this would generally take two months when storage is at low temperature (4°C). The pathogens isolated and identified on jujube fruit by different researchers vary, as do the pathogens isolated and identified at different times from different regions, and from jujube fruit gardens with different ecotypes (Table 13.4) (Wei, 2006). One disease is also often caused by a mixture of a variety of different infections. During packaging, storage and transport, fruit may be exposed to various decay-causing microflora. Some of the predominant organisms observed on freshly harvested fruit are Aspergillus niger, A. sydowii, Rhizopus oryzae, Penicillium chrysogenum, Alternaria tenisima, Phoma spp., and Cuvrularia spp., of which A. niger andR. oryzae cause the greatest spoilage in vitro (Kainsa, 1978). About 16 fungi belonging to 12 genera have been reported to cause postharvest decay in jujube fruit, transit and storage. However, the names of some of the diseases affecting jujube fruit post harvest are based primarily upon the

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Table 13.4

List of diseases of jujube fruit

Name

Pathogens

Distribution and harmful degree

References

Anthracnose of jujube Jujube fruit shrink disease

Colletotrichum gloeosporioides Pens Eruinia jujubovra Wang Cai Feng et Gao; Dothiorellu gregaria Sacc; Coniothyrium olivaceum Bon; Alternaria alternata f.sp. tenuis Alternaria alternate (Fr.) Keissler; Phoma destructiva Plowr; Fusicoccum sp.

Henan, Shandong, Shanxi, Hebei Henan, Hebei, Shandong, Shanxi, Beijing and Anhui, the rot rate is 30% to 50%, the most severe areas have almost total crop failure

Sun Yongan et al. (1984) Chen Yijin et al. (1989); Qu Jianxu, et al. (1992); Li Zhiqing et al. (1997); Zheng Xiaolian et al. (1995, 1996)

Jujube brown cortex disease (brown cortex and shrunken fruit type)

Henan, Hebei, Shandong, Shanxi, Beijing and Anhui, the rot rate is 30% to 50%, the most severe areas have almost total crop failure Black-red spot Taiyuan and Jiaocheng Alternaria tenuis; disease of jujube in Shanxi, and other Phoma sp. places, 10% to 15% loss Main producing areas Alternaria sp.; Rot fruit of Alternaria tenuissima; of jujube in Lubei of Zizyphus jujuba Shandong, 66.7% loss Mill. cv. Dongzao Erwinia sp.; disease; Black spot Pseudomonas sp.; Xanthomonas sp. type; Canker, soft-rot type; Black spot disease of Dongzao In the north and Ring spot of Macrophoma Huanghua, Hebei, jujube kawatsukai Hara Henan and other places, 10% to 20% of fruit are affected, 40% to 50% in rainy years, the most severe areas have almost total crop failure Macrophoma Thick rotten Hebei, Shandong, disease of kawatsukai Hara; Tianjin, the rot rate is Jinsixiaozao; Dark Physalospora obtuse about 30%, the most furuncle disease of (Schw.) Cooke; severe area have almost Jinsixiaozao; total crop failure Fusicoccum sp.; Brown ring disease Alternaria alternata of Jinsixiaozao (Fr..) Keissler; Phoma destructiva Plowr

© Woodhead Publishing Limited, 2011

Kang Shaolan et al. (1998)

Lin Zhongmin et al. (2001)

Xin Yucheng et al. (2003); Ji Yanping et al. (2003); Li Xiaojun et al. (2004)

Chang Jupu (2004)

Su Anren et al. (1994); Liu Chunqin et al. (2004); Zhang Lizhen et al. (2004)

Chinese jujube and Indian jujube Table 13.4

309

Continued

Name

Pathogens

Black rot disease Alternaria alternata of Zizyphus jujuba (Fr.) Keissler; Phoma Mill. cv. Dongzao aestructiva Plowr; Fusicoccum sp. Thick liquid Rhizomorpha Roth.; disease; Mould Alternaria Ness.; rot disease; Foot Rhizopus sp.; rot of fruit stem Mucor sp.; Soft-rot disease of jujube; Aspergillosis; Blue mold of jujube; Trichoderma disease of jujube Other disease

Rhizopus sp.; Aspergillus sp.; Penicillium sp.; Trichoderma sp.

Botrytis sp.; Penicillium sp.; Phyllosticta sp.; Alternaria sp.; Aspergillus sp.; Bispora or Dicoccum sp.

Distribution and harmful degree

References

Similar to fruit shrink disease, causing rot in post-harvest storage

Sheng Jiping et al. (2003)

Hebei, Shandong, Tianjin, the rate of rot is about 20% to 40% after stored for 60 days Henan, Anhui, Hebei and Shaanxi, taking place in the harvesting, storage and processing period

Wu Xingmei et al. (2003)

Taking place in the storage period

Ren Guolan et al. (2004)

Zhao Jialu et al. (2002); Hao Lin et al. (2000)

symptoms of infected jujube fruit, and have both an alias and a common name. There are also different types of some diseases. All of these factors result in confusion. For example, jujube fruit shrink disease is also known as jujube brown cortex disease, black rot and brown rot; furthermore, black rot is also known as brown spot. Jujube brown cortex disease can be further divided into brown pericarp and fruit shrink diseases. Z. jujuba fruit rot disease can also be divided into black spot, canker and soft-rot type. The diseases caused by pathogenic organisms are mainly thick liquid disease and stem end rot disease (Wu, 2003). Jujube fruit shrink disease Jujube fruit shrink disease, which as mentioned above is also known as brown cortex and black rot disease, is the most serious of the jujube diseases. This disease is initiated in the jujube white maturity period, causing flesh browning, a bitter taste and early fruit drop, resulting in a decreased yield and quality. This disease is mainly caused by fungi and bacteria singly or jointly (Wu, 2003). Thick liquid disease Thick liquid disease is caused by Rhizomorpha Roth. and Alternaria Nees ex wallr. The symptoms are firstly a pale skin, and dark red and dark brown

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discoloration spots in the shoulder or waist of the fruit. The color also deepens, the texture of the skin changes, the flesh provides no resistance to touch and the inside of the fruit becomes a pulp slurry. Finally, the severe lesions make the entire fruit rot. It is a particularly serious disease in later stages of storage (Wu, 2003). Foot rot of the fruit stem Foot rot of the fruit stem is caused by a mixed infection. The pathogenic organisms are the root Rhizomorpha Roth. ex Fr., Rhizopus, Alternaria and Penicillium. Foot rot of the fruit stem begins from the base of stem. According to the color, the disease can be divided into water-rotten type, brown rot type and black rot type. The water-rotten-type lesion exhibits light brown or watery spots, and soon the entire fruit rots. As the name suggests, the brown rot-type lesion is brown, and rotting is faster than with the water-rotten-type lesion. The black rot-type lesion is black and results in the slowest rotting rate. Thick liquid disease and foot rot of the fruit stem are the most severe diseases during storage (Wu, 2003).

13.3.2

Control of postharvest pathology

Physical control and chemical control Physical control measures commonly include low-temperature storage, controlled atmosphere (CA) storage, vacuum storage and heat treatment. Common chemical control measures include dipping with fungicides. Lal (1981) evaluated five fungicides and found that Bavistin and Difolation performed best and could be recommended as fruit dips at 500 ppm and 1000 ppm, respectively. Treatment with 1% Bavistin and 5% Virosil reduced both pathological and physiological losses in ambient conditions (30°C) as well as in cold storage (7°C) (Vishal, 1999). Fungal infections on stored ‘Gola’ fruit caused by pathogens such as Rhizopus sexualis, R. microperum and R. oligosporus, as well as Mucerpyriformis, Alternaria alternata, A. niger, A. fiavus, Trichothecium roseum, Tridadium splendens, Phoma scrghuia, Fusarium culminorum and Penicillium spp. were suppressed when jujube fruits were stored at low temperature (7°C) after treatment with cold water (30 min, 0°C), hot water (50°C for 5 min), and 0.5% calcium chloride. There was a significant decrease in the infection rate (a reduction of 93.3%) in fruit stored at room temperature (28 ± 2°C) after treatment with cold water (15 min, 0°C), hot water (5 min, 50°C), 2,500 ppm Virosil and 0.5% calcium nitrate (Nallathambi, 2000). Further information about treatments that influence levels of postharvest disease as well as other factors related to postharvest quality, such as rate of ripening, can be found in section 13.6. Biological control Biological control of plant diseases relies on the use of appropriate antagonists. Most antagonists which have a significant inhibitory effect on pathogenic fungi can be isolated from bacteria, fungi and yeast in plants and soil. The mechanism of biological control by antagonists is considered to be that antagonists compete with the pathogens for nutrition and space, or that the antagonists induce host

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resistance. Strain B501 isolated by Xue et al. (2008) from the surface of jujube fruit showed antagonistic activity on jujube fruit against black spot disease caused by Alternaria alternata. This bacterium was identified as Pantoea agglomerans according to its physiological and biochemical properties, and from phylogenetic analysis of its 16S rDNA sequence. Strain B501 could noticeably and significantly reduce the incidence of black spot when applied on wounded fruits at the relatively low concentration of 1×107 cfu/ml, with a success rate of 80%. 13.3.3 Postharvest entomology At present, there are more than 42 major harmful insect pests found in Ziziphus fruit, with losses caused by insects in the storage of dry fruit more serious than that in fresh jujube storage. The serious pests are Lygus lucorum Meyer-Dur, Eriophyes annultus Nale, Contarinia SP, Tetranychus truncatus Ehara and Europhera batanyensis Cara-dja. There are economic, security and environmental advantages to the use of biological controls to inhibit insect pests, which makes them a suitable prospect for use on jujube. It has been found that the nuclear polyhedrosis virus of Sucra jujuba Chu has particularly inhibitory effects (Ji and Liu, 2000).

13.4

Postharvest disorders

Postharvest disorders of jujube include alcoholic fermentation, browning and chilling injury. Shen et al. (2004) investigated the process of fermentation softening in Dongzao jujube fruit. The results showed that the ethanol content increased linearly during storage. When the ethanol content reached 0.1 g·100 g−1 formula weight (FW), fermentation softening took place, with over-accumulation of ethanol being the main reason for softening. Fumigation of fruits for 12 h at room temperature with 1-MCP at 1.0 μL·L−1 inhibited ethylene production and delayed the progress of fermentation and softening. Wu et al. (2001) examined the relationship between softening, browning and polygalacturonase (PG) and PPO activity, as well as the effects of preharvest treatment with CaCl2 and 6-BA solution on softening, browning and PG and PPO activity, in postharvest ‘Zanhuang’ jujube. During storage periods, PG activity fluctuated and showed little correlation with softening, while the browning index and PPO activity increased, with PPO activity showing a relationship with flesh browning. With preharvest treatment of 1% CaCl2 or 1% CaCl2+15 mg/kg 6-BA, at the last stage of storage the flesh firmness of ‘Zanhuang’ jujube was improved by 1.2 kg cm−2 or 1.5 kg cm−2, respectively, relative to control. Jujube fruit is also susceptible to chilling injury when exposed to temperatures below freezing. Wang et al. (2007) reported that the freezing temperature of ‘Langzao’ in the half-red stage is −2.4°C ~ −3.8°C, while ‘Lizao’ is susceptible to freezing injury when exposed to −2°C over a long period. Chilling injury is characterized by the appearance of pits on the fruit peel as a result of damage to plasma membranes and loss of cellular integrity.

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13.5

Postharvest biology and technology of tropical and subtropical fruits

Preharvest treatments to extend shelf life

Preharvest treatments have important effects on the shelf life of jujube fruits, and appropriate treatment before harvest will distinctly extend the fruit shelf life. There are many available methods to extend the shelf life of jujube fruits, such as choosing the optimal harvest maturity, calcium treatment and bagging on the tree. 13.5.1 Varieties and harvest maturity The choice of jujube cultivar affects postharvest fruit quality. Wei and Li (2009) investigated the effects of variety on the quality of fruits of Chinese jujube. Flesh firmness and the contents of ascorbic acid, soluble solids, sucrose and total sugars in ‘Liwuchangzao’, ‘Dongzao’ and ‘Lizao’ harvested at the same time decreased after 95 days of cold storage. Of the three varieties, after storage the flesh firmness and ascorbic acid content were lowest in ‘Lizao’, while the sucrose content in ‘Dongzao’ was reduced by 88.5%, which represented the greatest reduction of the three varieties. The contents of titrable acidity in ‘Lingwuchangzao’ and ‘Dongzao’ showed an upward trend, but there was a downward trend in ‘Lizao’. The fructose content of ‘Dongzao’ rose sharply by 113.6%, resulting in ‘Dongzao’ becoming sweeter than ‘Lingwuchangzao’ and ‘Lizao’ after storage. Jujube fruits that are allowed to ripen on the tree normally have a shorter shelflife, and the best results have been obtained when fruit are picked before the onset of ripening. The development of fruit skin color is one of the most reliable maturity indices. Fruit are harvested at the mature golden-yellow stage for the ‘Umran’ and ‘Kaithli’ cultivars, and at the mature green stage for the ‘Mallaey’ and ‘Bambadawi’ cultivars (Pareek et al., 2009). Wei and Li (2009) also investigated the impact of harvest timing on ‘Liwuchangzao’ cv. quality, and the changes in jujube quality before and after storage. The results showed that the flesh firmness of fully red fruit flesh was less than that of half-red fruit of ‘Lingwuchangzao’ cv. harvested on a different date. The half-red fruit have a longer shelf life. Han et al. (2008) studied the differences in respiration, cell membrane permeability and weigh loss ratio in ‘Lingwuchangzao’ harvested at the three harvest maturity, fumigated with thiabendazole (TBZ) at 20±0.5°C and stored at −0.5±0.5°C. They reported that the low-maturity grade had better storage properties, but lower quality. Every physiological index of jujube fruit showed an increase after fumigation. Overall, with regard to storage properties and quality, the low maturity degree was considered to be the best harvest maturity, under proper storage conditions. 13.5.2 Calcium treatment The calcium content of fruit influences the shelf life. Therefore, preharvest applications of calcium compounds can have an effect on storage life. Fruits naturally contain calcium as compounds of pectate, carbonate, oxalate and phosphate. Shi et al. (2004) analyzed the effects of calcium on fruit ripening and senescence, of ‘Dongzao’ ‘Dongzao’ were treated with 0.2% calcium chloride as a spray five

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times before harvest. The protein content of calcium-treated fruit was significantly higher than that of non-treated fruit. Some important antioxidant enzymes which can eliminate free radicals, reduce the damage to the membrane system and delay the aging process in plants were also detected in this experiment. The results showed that LOX activity decreased but superoxide dismutase (SOD), POD and PPO activity increased from the white maturing to the half-red period. This showed that calcium treatment before harvest had a positive anti-senescent effect on the postharvest ‘Dongzao’ fruit. Xing et al. (2009) also reported that three different calcium solutions sprayed three times on the surfaces of ‘Dongzao’ fruit during the early stages of fruit growth could remarkably retard the increase in browning index, prolong the shelf-life and reduce loss of fruit firmness. Spraying ber fruits 10 days before harvest with CaCl2 (1.7 g L−1) with 1% Teepol as a surfactant reduced fruit weight loss, delayed color development and resulted in maintenance of quality during storage (Pareek et al., 2009). In another study, a reduced respiration rate was associated with increased calcium content arising from exogenous application of calcium nitrate (Gupta and Mehta, 1988). Spraying with 1% CaNO3 at the color-turning stage was also found to improve the shelf-life of fruit at room temperature (Siddiqui et al., 1989). 13.5.3 Bagging Bagging on the tree has been widely used and is an effective way to improve the postharvest quality of fruit. Bagging can promote anthocyanin synthesis and improve fruit coloration, reduce pest infestation, and maintain the smoothness of the fruit surface. Li et al. (2008) studied the effects of preharvest bagging on the postharvest storage properties of ‘Lizao’ jujube, and showed that the respiration rate of bagged jujube fruit was lower than that of the control fruit. PG activity showed little correlation with softening. The curve of POD activity showed two peaks, with the second higher than the first, while the activity curve of PPO during storage showed a single peak. Relative to control, the activities of PG and POD in bagged jujube fruit were inhibited and the POD peaks were delayed. Flesh firmness was also retained at a higher level in the bagged fruit and the rate of decay was reduced.

13.6

Postharvest treatments to extend shelf life

This section examines the effects of postharvest treatments on fruit quality. 13.6.1 Low-temperature storage Temperature is one of the most important factors affecting the storage life of fresh jujube fruit. Cold storage of fruit has advanced noticeably in recent years, leading to better maintenance of organoleptic qualities, reduced spoilage and longer shelflife. To a certain extent, the lower the temperature, the better the storage. To avoid chilling injury, the cold storage temperature of most varieties of fresh jujubes

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should be controlled at −0.5°C ~ 1°C, and the respiration rate of the fruit should be controlled at a very low level. Several studies have examined the effect of low temperature on postharvest changes in the chemical constituents of jujube fruits, and on their storage behavior. Storage at temperatures around 0°C inhibited the jujube respiration rate, helped maintain a fresh state, and preserved ascorbic acid contents (Chen and Wang, 1983). Use of low temperatures (0°C) can slightly restrain PG and pectin methylesterase (PE) activity in the earlier stages of fruit maturity, preserve SOD and POD activity, and reduce the rise in malondialdehyde (MDA) activity (Wu, 2001). Zhai et al. (2008) studied the changes in quality during the different stages of maturity of ‘Xinjiang Dongzao’ jujube fruit in storage. The results showed that using a preserving agent and packing in micro-porous preservative film, then storing at (−2 ± 0.5)°C, is an effective way to improve the quality of ‘Dongzao’ jujube. Jawanda et al. (1980) observed that ‘Umran’ and ‘Sanaur’ fruit could be stored at −2°C in commercial cold storage for up to 30 and 40 days, respectively. Tembo et al. (2008) reported that jujube fruits stored at low temperature (5°C) lost only 48% of their weight during the entire 12-week storage period, while fruit stored at ambient temperature (22°C) and intermediate temperature (15°C) lost 70 and 75% of their weight, respectively. After three weeks of storage, more than 40% of the fruit at the ambient and intermediate storage temperatures had shriveled, compared to only 3% at the low storage temperature. It can be concluded that cold storage conditions can help reduce the respiration rate and ethylene production of fruit, maintain firmness and POD and CAT activity, and can retard weight loss, rises in MDA content and membrane permeability, prolonging shelf life. In cold storage (10°C, 79% relative humidity (RH)), fruit of the ‘Gola’, ‘Kaithii’ and ‘Umran’ cultivars remained acceptable for up to 42, 28 and 35 days, respectively (Pareek et al., 2009). 13.6.2 Controlled atmosphere (CA) Treating ‘Dongzao’ with 20 μL L−1 NO can mitigate the injurious effects of ethanol and effectively delay the browning and softening of fruit during storage (Sun, 2007). Treatment with 20 μL L−1 NO was also found to significantly slow the increase in red index, inhibit changes in PPO and phenylalanine ammonialyase (PAL) activities, help maintain a low total anthocyanin content and a high total phenol content, and delay the increase in soluble solids and decrease in ascorbic acid (Zhu, 2009). Compared to storage in air, the contents of ethanol and ethyl acetate, and the degradation of anthocyanin and chlorophyll, were significantly lower in fruit stored in 5% O2 + 0% CO2 or 10% O2 + 0% CO2 at −1 °C. In comparison to other treatments, short-term high O2 (70%) treatment was the most effective in maintaining peel color and anthocyanin and chlorophyll contents, and preventing peel browning. The ethanol content was significantly lower in the fruits stored in CA with 10% O2 + 0% CO2, relative to storage in air, while storage in 5% O2 + 0% CO2 was effective in reducing the ethyl acetate content throughout the storage

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period. The use of CA conditions effectively controlled disease development of the jujube fruit, while soluble solid contents (SSC) and TA were not significantly affected by CA treatments (Lin, 2004). The membrane permeability of jujube fruit was kept in a relatively controlled state by CA (12–15% O2 + 0% CO2), and the increase in alcohol content was also retarded. The browning and fermentation of jujube could also be inhibited by appropriate CA conditions (Zong, 2005). A CA index of 2% O2 + 0% CO2 was the most beneficial during storage of ‘Dongzao’. Using an appropriately low level of O2, it was possible to restrict the decrease in pulp hardness, maintain cell membrane integrity and reduce acsorbic acid losses, while this did not cause a great accumulation of ethanol and acetaldehyde (Wang, 2008). Use of an appropriately low concentration of O2 for ‘Dongzao’ could also reduce the respiration rate, slow down the increase in the relative electrical conductivity of the pulp, restrict the reduction in relative pulp firmness, delay the degradation of ascorbic acid, and maintain general fruit quality during storage (Wang, 2009). Compared with low temperature storage in air, CA with 10% O2 plus 0% CO2 significantly reduced the softening rate and maintained fruit firmness and total soluble sugar (TSS) and TA content during the entire storage period. Moreover, in fruits stored in CA a relatively greater abundance of esterified pectins and lignin-like phenols was found in the flesh cell wall, with less linear long-chain aliphatic compounds in the cuticle layer (Wu, 2009). 13.6.3 Ozone application The application of ozone in storage of ‘Dongzao’ can inhibit microbial growth, reduce fruit respiration and ethylene levels, prevent browning and delay metabolic processes (Liu and Wang, 2004). These researchers also found that starch content and amylase activity were lower in jujube treated with ozone. Wet storage of the jujube combined with ozone at low temperatures could effectively inhibit LOX and POD activity, and delay the decline of SOD activity and rise in MDA activity, which helps to maintain the integrity of the cell membrane. Treatment of ‘Lingwuchangzao’ with 100 μg·L−1 ozone could remarkably mitigate the acid content changes, reduce the sugar content, and keep the ascorbic acid level. After 90 days storage, the percentage of hard fruit was 50% and that of acceptable fruit was 95.3% (Hang, 2007). Treatment with 0.75% chitosan coating and 300 μg/L ozone at room temperature could reduce losses of TSS, TA and ascorbic acid, postpone the decrease in sugar levels, and remarkably mitigate the decreases in phenol content. This treatment could also activate POD, which is a key component of the protective enzyme system. Compared with control, ozone water treatment can help maintain fruit firmness of ‘Dongzao’ and inhibit changes in surface redness and ethanol accumulation, help maintain the TA and ascorbic acid content, delay senescence, and aid in maintenance of a better appearance and quality during storage. In these experiments, the best concentration of ozone water treatment was found to be 1.00–1.99 mg.L−1 (Yang, 2009).

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13.6.4 Calcium solution treatment Calcium plays an important role in postharvest physiological and biochemical and fruit storability. As already mentioned, exogenous calcium treatment can help to maintain fruit hardness, reduce disease, and delay ripening and fruit softening (Ferguson, 1995). Treatment with 2% CaCl2 solution can significantly prolong the postharvest fruit storage period (Chen, 1984). Ca2+ treatment was found to regulate the physiological activity of jujube fruits, and prohibit the respiratory consumption of organic acid and the loss of ascorbic acid (Li, 2003). Vacuum infiltration of Ca2+ in ‘Lingwuchangzao’ can prevent the oxidization of ascorbic acid. By the sixtieth day of storage the percentage of acceptably fresh fruit in the treatment group was 90.9%, while that in the control group was 60.5%. However, the effects of vacuum-infiltration of Ca2+or Ca2+ plus plant hormone on the flesh firmness and TA, SSC, total sugar and pectin levels were not significant. About 5% of jujube fruits were found to be cracked after infiltration with Ca2+ or Ca2+ plus plant hormone, thus affecting the appearance of the jujube (Wei, 2008). 13.6.5 Preservative treatments Fumigation of Z. jujuba Mill cv. ‘Lingwu Chang’ with 5 g/m3 4.5% TBZ, (−0.5 ± 0.5°C; RH 90 ± 3.0%) was found to remarkably mitigate against the changes in acid levels and the reduction in sugar levels (Zhao et al., 2009). Traditional Chinese herbs are widely used as safe preservatives. Gan et al. (2008) found that the optimal concentrations of preservatives for Z. jujuba Mill cv. ‘Lingwu Chang’ were 40 g L−1 ethanol extract of Forsythia suspensa (Thumb.) Vahl, 20 g/L water extract of Alpinia officinarum Hanc, 12 g L−1 ethanol extract of Eugenia caryophyllata (Thumb), 10 g L−1 CaCl2, and 75 mg/kg GA3. After 30 d storage at room temperature (18 ~ 22°C), the rate of decay was only 12.64%, the rate of softening was 1.83% and water loss was 1.82%. Meanwhile, the fruit quality was well maintained, with the fruit retaining its firmness and fine flavor after storage. Some edible preservative agents for Chinese jujube have been developed. Dou et al. (2009) used sugar, ascorbic acid and citric acid to develop edible preservative agents for ‘Dongzao’, with both giving good results: Formula I with a 70% ethanol solution of a mixture of wax and lipid, and Formula II with a sugar, ascorbic acid and citric acid aqueous solution. 13.6.6 Chlorine dioxide treatment The quality of ‘Dongzao’ has been shown to be enhanced by treatment with 80 mg.kg−1 chlorine dioxide, relative to control. After 80 days of storage, the percentage of sound ‘Dongzao’, the firmness, the ascorbic acid content, and the PG activity were found to be higher than those of the control, while soluble pectin levels and PPO activity were lower than those of the control (Zhang, 2008). These results showed that chlorine dioxide can be used to preserve ‘Dongzao’ quality.

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13.6.7 Ethanol treatment Treatment with 4.5 mL.kg−1 ethanol can delay softening and the decline in ascorbic acid content, as well as decrease the rate of decay, and prolong the postharvest life (Li, 2006). Ethanol application is also reported to decrease the respiratory rate and ethylene production, preserve appearance, and delay senescence and ripening of jujube fruit (Li, 2008). 13.6.8 Irradiation Irradiation treatment can prevent rot and extend jujube shelf life post-ripening (Liu, 1998), but the radiation dose and irradiation time are difficult to control, and therefore this method is not currently widely used. A 1 kGy dose gamma-ray irradiation of plastic film-packed dried Z. jujuba can effectively kill insects in the jujube, such as Lepidoptera or Elytrum. After one year of preservation, the sound fruit percentage of the irradiated jujube was found to be more than 90%. The levels of the major nutrients such as sugars, amino acids, vitamins and inorganic salts were apparently not altered (Liu, 1987). However, treating Z. jujuba with UV light irradiation for 15 min before storage, then packing with a small non-perforated thin-film package, or a large perforated thick-film package, in combination with the presence of permanganate in the package, was found to be ineffective in keeping jujube fresh (Xu et al., 1996). 13.6.9 Hypobaric storage Hypobaric storage of jujube fruit has been found to help maintain firmness and ascorbic acid content, reduce acetaldehyde and alcohol content in the pulp, lower the respiratory rate and ethylene production rate, and inhibit AAO and alcohol dehydrogenase (ADH) activities, although an effect of hypobaric storage on flesh browning was not apparent (Xue, 2003). Fruit stored under hypobaric conditions of 55.7 kPa showed the best quality (Jin, 2006). In comparison with the control, hypobaric storage of ‘Dongzao’ helped retain firmness and preserve the appearance, decrease weight loss, maintain the organic acid and ascorbic acid content, and retard senescence (Wang, 2007). Hypobaric storage decreased the respiration rate of ‘Lizao’, delayed the loss of fruit ascorbic acid content, decreased the rate of production of superoxide anion, clearly slowed down changes in redness, increased the percentage of sound fruit and to a certain extent prolonged the fruit storage life. There were no significant differences found in terms of the physiological and biochemical indexes of ‘Lizao’ between treatment under 20.3 kPa and 50.7 kPa (Cui, 2008). 13.6.10 Heat treatment Treatment with hot water at 53°C for 6 minutes could help delay ‘Dongzao’ senescence, maintain the flavor, suppress physiological and pathological injury,

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and reduce decay and dehydration rate (Cao, 2007). Immersion of Z. Mauritiana fruit in hot water at 55°C for 10 minutes was also found to help maintain quality, and significantly inhibit decay and water loss, during storage (Yao, 2007). 13.6.11 Other treatments The shelf-life of jujube fruit which was treated by microwave for 20~25 s was prolonged by 2~3 days. The rates of respiration, degradation of TSS, loss of organic acids (OA) and ascorbic acid, and water loss all decreased (Chen, 2008).

13.7

Postharvest handling

13.7.1 Storage at ambient temperature After harvest, jujube fruit are usually stored at ambient temperature until they are either sold or processed. The fruit are often stored in heaps under shade or in storage rooms, but it is better to store them in packages such as gunny bags, net bags, polythene bags or boxes. Depending upon the cultivar and the storage conditions, fruit can be kept for 4 to 15 days without loss of organoleptic quality (Zhang and Li, 2007). During storage, the fruit lose weight and shrivel, change color from green-yellow or golden-yellow to reddish-brown and lose acidity and ascorbic acid, but gain in sweetness. 13.7.2 Grading Jujube fruit is commonly harvested at different stages of maturity, and needs to be sorted into different groups before marketing, storage or processing. Fruit are sorted and graded according to maturity, size, shape and color. First the fruit are sorted by hand, and the under-ripe, over-ripe, damaged and misshapen fruit are removed. The under-ripe fruit are set aside and left to ripen, while over-ripe fruit, which are not desirable for the fresh market or for processing, are discarded. The remaining fruit are graded into two or three groups, based on the size and color. Grading can either be carried out manually or by passing the fruit through sieves of different mesh sizes (Zhang and Li, 2007). The grading standards for dry red jujube and ‘Dongzao’ jujube fruits are included in Table 13.2 and Table 13.3, respectively. After grading, fruit destined for further processing are washed using chlorinated water (100 ppm) and drained. Fruit destined for sale are packed, and either stored or transported to the market. 13.7.3 Packaging After harvest, the fruit are brought to the pack house or under shade for cleaning, packing, or for postharvest treatment to extend their shelf life. The fruit are packed either for controlled storage or for safe transport to local or distant markets.

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Correct and appropriate packaging of the fruit is essential for their safe transportation and storage. An ideal fruit package ensures that the fruit is completely protected from physical damage and does not spoil. During transport and storage, jujube fruit are susceptible to infection with bacteria and fungi, especially if organic packing or cushioning material is used for packaging. A freshness-promoting paper bag, treated with Chinese herbal medicine, can also be used for packaging to reduce the incidence of rotten Z. jujuba fruit (Zhang, 2004). Perforated polythene bags (150 gauge), nylon nets or cardboard cartons can be used to package small quantities of fruit of 1–2 kg. For larger volumes of fruit (10–20 kg), gunny bags, cloth packages or wooden boxes with holes or slits are used. Baskets made from locally available materials such as bamboo can also be used. For transportation, corrugated cardboard cartons holding about 5 to 10 kg are the most suitable packaging material. Shredded paper is the best material for cushioning and protection during transport (Zhang and Li, 2007). For short distances, cheaper materials such as gunny bags, cloth or old boxes can be used provided that the fruit are cushioned and ventilation is provided (Zhang and Li, 2007). Small quantities of about 1 to 3 kg fruit for retail sale should be packaged in transparent plastic bags, plastic bags with holes, or mesh bags. These are not only beneficial for extending the fruit shelf life, but are more aesthetically appealing to customers (Zhang and Li, 2007).

13.8

Processing

Jujube can be used to prepare various processed products such as dehydrated products, candy, juice, wine, vinegar, jam, jelly, slices and powder, as well as fresh cut fruit (Wan et al., 2009) (see Fig. 13.1). Here we discuss only dehydrated products, candy, juice, beverages and frozen fruit, which are the most significant processed products. 13.8.1 Dehydrated jujube products Drying fresh jujube reduces the water content from about 70% to about 25%. The increased concentration of TSS means that it is difficult for microorganisms to survive and the resulting dehydrated jujube products are consumed worldwide (Khurdiya and Roy, 1986; Chen, 1985). Briefly, the process for production of dehydrated jujube is as follows: cultivation → timely harvesting → fruit classification and selection → cleaning → pre-treatment → oven-drying → temporary softening → packaging → storage → market. The fresh jujube fruit that are chosen should be consistent in color and size, at the ripening stage and free from pests. When the jujube drying process is complete, the fruit should be placed indoors so that it can reabsorb a certain amount of water and therefore soften before packaging (Chen, 1985).

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Fig. 13.1

Processed Chinese jujube: (a) dehydrated jujube; (b) candied jujube; (c) jujube powder; (d) sliced jujube.

13.8.2 Candied jujube Candied jujube is produced by boiling the fruit in a sugar solution to increase the sugar concentration to a certain point, then drying it. The surface of the candied jujube is brown and it is a very popular product in China and India (Ma, 2003; Gupta, 1983). The process is as follows: fruit classification and selection → cleaning → size reduction → candying → soaking → baking → packaging in plastic bag. It is possible to use honey instead of sugar in the process. The product is then known as ‘bee-sugar candy’ (Ma, 2003). 13.8.3 Jujube juice and beverages Juice and beverages can be made from either fresh jujube or dried jujube (Shi and Qi, 2002; Khurdiya, 1980). Briefly, the processes are as follows:

•

Juice from fresh fruit: selection of fresh fruit → washing → draining → baking → soaking and juice extraction by filtering → ingredient addition → preheating → bottled degassing → sterilization → cooling.

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Juice from dried jujube: selection of dry dates → loading → cleaning → softening → draining → breakdown of jujube → extraction → first filtration → second filtration → concentration → sterilization and aseptic filling → finished product (Shi and Qi, 2002).

Juice from fresh jujube fruit is clear like apple juice. Juice from dried jujube has a distinctive dark red color and a sweet, delicious flavor. However, health drinks which are a mixture of jujube and other ingredients are more nutritionally complete and often more fit for healthy purpose. 13.8.4 Frozen jujube fruit Freezing is also a potential method of jujube fruit storage. Wei and Deng (2002) examined frozen storage of ‘Lizao’ Chinese jujube, and reported that ‘Lizao’ frozen at −50°C retained its high quality for 8~12 months at −22°C to −35°C. Following storage for 8 months, the ascorbic acid retention was found to be 52.8 ~ 62.6%, and firmness retention 70.1~78.6%, after thawing at room temperature.

13.9

References

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Li J W, Liu P F, Shao D D, Xiao L D (2007), ‘Nutritional composition of five cultivars of Z. jujuba’, Food Chem, 103, 454–460. Lin R, Li J, Chang J (1995), ‘A study of storage life and biological characteristics in jujube (Zizyphus jujuba Mill)’, Acta Hort Sinica, 22, 25–28. Liu F, Zhang X, Wu S L, Fu Q C (2008), ‘Study of the essential oil of Michelia wilsonii finetet gagnep on the Preservation of Zizyphus jujuba Mill’, J Changchun Normal Univ, 27 (3), 65–69. Liu X H, Yu G L (1998), ‘Study of jujube preservation’, Food Res Development, 19(3), 50–53. Liu X J, Wang Q (2004), ‘A study on changes of post-harvest physiology of Dongzao in humid cool and conventional cold room conditions’, J Fruit Sci, 21(4), 346–349 Liu Z, Wang Y C, Wang G Z, Chen Y T (1987), ‘Irradiation preservation of dried jujube and day lily’, Appl Atomic Energy Agric, 2, 13–17. Lu G H, Li C J, Lu Z S (1993), ‘Wound-induced respiration in thin slice of Z. jujuba fruit’, Plant Physiol, 141, 115–119. Ma W (2003), ‘Smoked jujube, candied jujube, wine – jujube processing technology’, Farm Products Processing, 8, 28–29. Martinez R D (2000), ‘Exogenous polyamines and gibjujubeellic acid effects on peach (Prunus persica L.) storability improvement’, J Food Sci, 65, 288–294. Muay’ed F A, Bushra S F (2002), ‘Respiration rate, ethylene production and biochemical changes during fruit development and maturation of jujube (Ziziphus mauritiana Lamk)’, J Sci Food and Agric, 82, 1472–1476. Nallathambi P, Umamaheswari C, Vashishtha B B, Vishal N (2000), ‘Fruit rot (Alternaria alternata) and sources of resistance in jujube germplasm under arid conditions’, Annals of Arid Zone, 39, 477–478. Pareek S, Kitinoja L, Kaushik R A, Paliwal R (2009), ‘Postharvest physiology and storage of ber’, Stewart Postharvest Rev, 5 (5), 1–10. Pawlowska A M, Camangi F, Bader A, Braca A (2009), ‘Flavonoids of Zizyphus jujuba L. and Zizyphus spina-christi (L.) Wild (Rhamnaceae) fruits’, Food Chem, 112, 858–862. Qu Z Z (1985), ‘Crisp jujube storage preliminary report’, J Beijing Agric College, 2, 114. Serek M, Sisler E C, Reid M S (1995), ‘1-Methylcyclopropene, a novel gaseous inhibitor of ethylene action, improves the life of fruits, cut flowers and potted plants’, Acta Hort, 394, 337–345. Shen L, Sheng J P, Niu J S, Liu Q X (2004), ‘Changes of respiration and ethylene production and effects of 1-MCP during the fermentation softening of Chinese winter jujube fruit’, J China Agri Univ, 9 (2), 36–39. Sheng J P, Luo Y B, Shen L (2003), ‘Chinese winter jujube and its fruits storage’, Acta Hort, 620, 203–208. Shi Q L, Qi Y (2002), ‘The present situation and development trend of processing and utilization about Z. jujube Mill in China’, Machinery for Cereals, Oil and Food Processing, 8, 30–32. Shi L, Shen L, Zhang Z Q, Shi F, Chang S M et al. (2004), ‘Effects of preharvest calcium treatment on relative enzymes activity of Dongzao fruit during ripening and senescence’, Food Sci, 25, 170–172 Siddiqui S, Gupta O P, Yamdagni R (1989), ‘Effect of preharvest sprays of chemicals on the shelf life of jujube (Ziziphus mauritiana Lamk.) fruits cv. Umran’, Haryana J Hort Sci, 18, 177–183. Sisler E C, Serek M (1997), ‘Inhibitors of ethylene responses in plants at the receptor level: recent developments’, Physiol Plant, 100, 577–582. Sun L N, Liu M C, Zhu SH, Zhou J, Wang M L (2007), ‘Effect of nitric oxide on alcoholic fermentation and qualities of Chinese winter jujube during storage’, Agric Sci in China, 6(7), 849–856.

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Tembo L, Chiteka Z, Kadzere I, Akinnifesi F K, Tagwira F (2008), ‘Storage temperature affects fruit quality attributes of Jujube (Ziziphus mauritiana Lamk.) in Zimbabwe’, African J Biotechnol, 7(17), 3092–3099. Vishal Nath, Bhargava R, Pareek O P (1999), ‘Improvement in shelf life of jujube (Ziziphus mauritiana Lamk.) by postharvest treatments’, 4th Agricultural Science Congress, Jaipur, India, 210, 21–24. Wan L, Shen L, Zhao D Y, Ding Y, Sheng J P (2009), ‘Effects of chitosan-based coating on safety and storage quality of fresh-cut Chinese winter jujube’, Food Sci, 30(4), 277–281. Wang L, Zhao Y L, Yan G Z, Li J H, Wang C S (2009), ‘Effect of CA storage on postharvest storage quality of Dongzao jujube’, Storage & Process, 51, 40–44. Wang R F, Luo Y B, Chang Y P (2003). ‘Physiological-biochemical changes of jujube fruits under the storage in a low pressure condition’, J Chin Inst Food Sci Technol, 3(2), 76–82. Wang Y P, Liang L S, Wang G X (2007), ‘Effects of low pressure on quality of ‘Dongzao’ jujube fruit in hypobaric storage’, Food Sci, 28(2), 335–339. Wang C S, Li J H, Wang Y Q, Zhao M (2008), ‘Advance of study on postharvest physiology and storage of fresh jujube’, J Shanxi Agric Sci, 28(3), 75–79. Wei T J, Dou Y P (2008), ‘Effects of vacuum-infiltration of Ca2+ and plant hormone on storage and freshness retention of jujube (Zizyphus jujuba Mill. cv.Lingwuchangzao) under low temperature’, Food Sci, 24(10), 118–121. Wei T J, Wei X T (2006), ‘Advances in research on diseases of Z.jujuba fruits (Zizyphus jujuba Mill.)’, Acta Agric Boreali-Occidentalis Sinica, 15(1), 88–94. Wei T J, Deng X M (2002), ‘Primary experiment report on frozen storage of “LiZao” Z. jujuba’, Sci Technol Food Ind, 23(10), 69–71. Wei T J, Li B Y (2009), ‘Effects of varieties and harvest time on fruit quality of Zizyphus jujube’, Chin Agric Sci Bull, 25(09), 184–187. Wu C E, Wang W S, Kou X H, Liang L Y (2001), ‘Effect of CaCl2 and 6-BA solution on softening, browning and activity of related enzyme in postharvest jujube fruits’, Trans Chin Soc Agric Eng, 34(1), 66–71. Wu P, Tian S P, Xu Y (2009), ‘Effects of controlled atmosphere on cell wall and cuticle composition and quality of jujube fruit (cv.Huping)’, Sci Agric Sinica, 42(2), 619–625. Wu X M, Sun L, Liu Y Q, Du H B, Wang K F, Qu Y Y (2003), ‘Research on main diseases in winter jujube storage time’, Econ Forest Res, 21(2), 19–22. Xing S J, Liu F C, Du Z Y, Zhao Q B, Song Y M (2009), ‘Effects of preharvest calcium treatment on storage property, calcium fractions, and subcellular distribution in Zizyphus Jujube Mill. cv. Dongzao fruits’, Food Sci, 30(2), 235–239. Xu J R, Li H, Wang J Z (1996), ‘Further-report on preservation of jujube in low temperature’, Hebei Forestry Sci Technol, 3, 15–18. Xue M L, Zhang J P, Zhang P (2003), ‘Effect of hypobaric storage on physiological and biochemical changes of dong jujube fruit during cold storage’, Sci Agric Sinica, 36(2), 196–200. Xue M L, Zhang L Q, Tang W H (2008), ‘Identification of bacterial strain B501 and its biocontrol activity against black spot on jujube fruits’. Chinese J Biol Control, 24(2), 122–127 Yan S J, Kou X H, Liang L Y, Wu C E, Cheng Y Q (2004), ‘Effects of IAA, ABA and ethephon on some physiological indexes of postharvest Li jujube (Zizyphus Jujuba cv.Lizao) fruit’, Plant Physiol Communications, 40(3), 323–325. Yan Y H, Gao Z P (2002), ‘Industrialization of Z.jujuba’, J Northwest Sci-Technol Univ Agric Forestry, 30(12), 95–98 (in Chinese). Yang X G, Zhang Z D, Liu X J, Zhao C Z, Wang Y (2009), ‘Effects of cold ozone water treatment on the fresh-keeping quality of winter-jujube’, Food Sci Technol, 34(10), 28–31.

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Yao X, Tu Y (2007), ‘Analysis of effect of different heat treatments on storage of Indian Jujube Fruit’, Food Mach, 23(3), 109–111. Zhai J L, Zhou H, Yang Y B, Jiang Y (2008), ‘Study on quality change of Xinjiang Dongzao jujube under low temperature storage’, Food Sci Technol, 5, 246–248. Zhang S H, Zhang C (2008), ‘The effects of chlorine dioxide (ClO2) on quality of winter jujube’, Mod Food Sci Technol, 22(3), 84–86.

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14 Kiwifruit (Actinidia spp.) J. Burdon and N. Lallu, The New Zealand Institute for Plant & Food Research Ltd, New Zealand

Abstract: The global kiwifruit industry has been built almost exclusively on the green-fleshed Actinidia deliciosa cultivar ‘Hayward’. It could be said that without the unusually good postharvest performance of ‘Hayward’, there may not have been the opportunity to create the global market for kiwifruit as it exists today. The postharvest performance of ‘Hayward’ fruit is largely the result of a tolerance of low temperatures used for storage. This chapter reviews kiwifruit, with a focus on fruit physiology and the way it affects the commercial postharvest sector, based largely on what is known about the ‘Hayward’ and ‘Hort16A’ cultivars. Key words: kiwifruit, postharvest physiology, physiological disorders, commercial handling and storage, postharvest pathology.

14.1

Introduction

Kiwifruit belong to the genus Actinidia, which comprises a diverse range of species, the two main commercially significant species being A. deliciosa and A. chinensis. There are 55 species and about 76 taxa currently recognised within the genus (Li et al., 2007), although this is being continually revised in the light of new information. Most taxa occur in south central and southwest China, an area regarded as being the centre of diversity and evolution of Actinidia (Liang, 1983). Most of the fruit that are currently being commercialised are the larger fruited selections of A. deliciosa or A. chinensis. An exception is the fruit of A. arguta, which are small grape-sized fruit that have to be handled and marketed like berryfruit. From the initial introductions of seed into New Zealand in 1904 (Ferguson, 2004), several kiwifruit strains were developed with commercial potential, including ‘Abbott’, ‘Allison’, ‘Bruno’, ‘Hayward’ and ‘Monty’. As more significant volumes of fruit began to be exported from New Zealand in the 1960s, the postharvest performance of the fruit became more important. ‘Hayward’ became the dominant cultivar because of its superior flavour and postharvest performance.

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Production in other countries was based on ‘Hayward’ sourced from New Zealand, resulting in the globally traded kiwifruit industry being based for many years almost exclusively on ‘Hayward’. While the overall volume of kiwifruit traded internationally is small compared with that of some other fruits, for some countries kiwifruit is a significant economic crop. Currently, on the basis of quantities of fruit produced, the major producing countries are China (467 000 metric tons), Italy (442 000 mt), New Zealand (370 000 mt) and Chile (173 000 mt) (data for the period 2007–10; Belrose, 2010). However, the production and export circumstances of these countries differ considerably. While China is a major producer, it is a minor exporter: about 1% of Chinese production is exported compared with more than 90% of production for New Zealand and Chile. In China a wider range of kiwifruit cultivars are grown, including ‘Qinmei’: this is the second most commonly grown cultivar of kiwifruit, but is only important in China. Whilst the global kiwifruit industry was developed on the ‘Hayward’ cultivar, that situation is now changing with the introduction and commercialisation of new cultivars. The most successful of these thus far has been ‘Hort16A’, which was created by HortResearch (now The New Zealand Institute for Plant & Food Research Limited) and is traded as ZESPRI® GOLD Kiwifruit. This cultivar was the result of a cross made in 1987, and was officially launched as a commercial product in 2000. ‘Hort16A’ belongs to the species A. chinensis, producing fruit with a yellow flesh and a more complex ‘tropical’ flavour than ‘Hayward’ fruit. ‘Hort16A’ now comprises about a quarter of the New Zealand annual export volume of about 100 m trays. There are also other new cultivars being commercialised from a range of sources. In Italy many of the new cultivars are from crossing with ‘Hayward’ (Summerkiwi®, ‘Katiuscia’) or bud-mutations of ‘Hayward’ (Bo-Erica®, Earligreen®, Green Light®, Top Star®) claiming advantages, such as earliness, over the traditional ‘Hayward’ (Ferguson, 2009; Testolin and Ferguson, 2009). There are also new A. chinensis cultivars other than ‘Hort16A’ being commercialised, of which the best known and most widely grown is probably ‘Jintao’ (http//:www. kiwigold.it). Notable among new commercial cultivars is ‘Hongyang’ (Wang et al., 2003), which has yellow flesh with a red centre, giving a natural selling point. The range of commercially available kiwifruit cultivars may increase beyond those from A. deliciosa, A. chinensis and A. arguta, in the near future. However, in general, the postharvest performance of these newer cultivars does not match that of ‘Hayward’ and providing quality fruit for a long selling window may be more difficult. With each of the new cultivars comes all the postharvest challenges that have either been managed, or avoided, with ‘Hayward’. The ability to manage these postharvest challenges is dependent on understanding the fruit physiology.

14.2 The Actinidia vine and fruit 14.2.1 Vine In the wild, the kiwifruit is a perennial climbing vine, growing in temperate rainforests. These natural origins are likely to underpin the behaviour and

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performance of the vine and fruit when grown commercially. The natural habit of the vine is to climb over other plants; commercially, the vine is provided with pergola or T-bar support structures onto which it is trained and managed. The kiwifruit vine builds carbohydrate reserves in both the shoots and roots to provide reserves for over-wintering and for bud-break and new growth in spring before the new season’s leaves become photosynthetically functional. Bud-break is dependent on chilling, although commercially this may be manipulated by the application of bud-break enhancers such as hydrogen cyanamide, which may also help condense the period over which bud-break occurs. Saturation of the photosynthetic capacity of ‘Hayward’ leaves is dependent on the light conditions under which the plants are grown. Plants grown under higher light conditions adapt and saturate at higher light levels than plants grown under low light conditions (Laing, 1985). Below 300 μmol/m2.s, the rate of photosynthesis is reduced. The photosynthetic rate of ‘Hayward’ increases with temperature, although the difference between the rate at 10 and 30°C is only about 20% on a leaf-area basis (Laing, 1985). On a leaf weight basis, the rate is constant at temperatures above 15°C. When comparing the effect of temperature on vegetative growth rather than photosynthesis, ‘Hayward’ vines have been shown to have a wide temperature optimum between 20 and 30°C (Morgan et al., 1985). Water is critical for the uptake of minerals and the movement of metabolites within the vine. Within the natural rainforest environment, water would not generally be limited: under commercial conditions water must be supplied by irrigation if natural rainfall is lacking. Adequate water supply is essential for steady fruit growth, particularly during the initial phase of fruit expansion. It has been estimated that a commercial kiwifruit vine uses about 100–150 L of water per day in the New Zealand climate (Clothier and Scotter, 1983; Sale and Lyford, 1990). Whilst water is essential for vine and fruit physiology, too much is detrimental; kiwifruit appear to be very sensitive to flooding and root anoxia (Smith et al., 1990). The extent of the root system is likely to be dependent on the soil type and depth. On a forest floor or in shallow soils, the root system may be shallow. In deeper soils, such as exist around the main kiwifruit growing area of Te Puke in New Zealand, root systems have been found to extend beyond 4 m (Greaves, 1985). 14.2.2 Fruit The commercially grown kiwifruit of A. deliciosa and A. chinensis are berries that are typically ovoid in shape, although size and shape vary among cultivars. The fruit have a brown skin and are covered in uni- or multiseriate hairs. The number and size of hairs differ among cultivars; ‘Hayward’ hairs are more numerous and robust than those of ‘Hort16A’. By the time the fruit are harvested, these hairs are dead and easily removed. The skin comprises several layers of dead compressed cells, with no specific peel tissue such as occurs in citrus or banana fruits, and no thick waxy covering (Hallett and Sutherland, 2005). The dead skin cells are suberised and accumulate phenolics to differing degrees, dependent on exposure

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to the sun. A fruit grown in full sunlight will develop a very brown skin whereas a fruit grown under a dense canopy will have a greener appearance. In early harvested ‘Hort16A’ fruit the skin layer may be scuffed easily to reveal the fruit flesh beneath. As the fruit develops further, the fruit skin becomes harder to scuff, making the fruit more durable for handling. The change in skin adhesion may be associated with the completion of the death and compression of those layers of cells that form the skin. There is a clear delineation of cells that will form the skin from those of the fruit flesh (Hallett and Sutherland, 2005). Early in development, not all the cell layers that will form the skin have died and been compressed. The lower layers of cells that will eventually form part of the skin are still living and may form a line of weakness between the already dead skin cells and the outer pericarp. Once all the skin cells have died, and been compressed, the ability to separate the skin from the fruit flesh may be reduced. This change in skin condition also appears linked to a reduction in the skin permeance of more mature fruit (Celano et al., 2009). One final, but very obvious, external feature of ‘Hort16A’ fruit is the presence of a pronounced protuberance or ‘beak’ at the distal end of the fruit. The protuberance in ‘Hort16A’ is the most marked of the currently commercialised cultivars, many of which have no protuberance. Internally kiwifruit comprises an outer and inner pericarp surrounding a central core or columella. Much of the cell structure of the fruit has been described for ‘Hayward’ or other earlier cultivars (summarised by Beever and Hopkirk, 1990). The outer pericarp comprises both small spherical cells and also larger, elongated cells that may be up to 1 mm in length. There appears to be a fundamental difference between the small and large cells of the outer pericarp. While the small cells accumulate large numbers of starch grains during fruit growth (Hallett et al., 1992), and also contain the cysteine protease actinidin (Nieuwenhuizen et al., 2007), the larger cells do not accumulate starch or actinidin to the same levels. Differences between the two cell types also occur during ripening. The cell walls of the smaller cells show swelling coincident with fruit softening, whereas the cell walls of the large cells do not swell (Hallett et al., 2005). In the outer pericarp, there are also cells which contain calcium oxalate crystals within a mucilage sheath (Strauss, 1970). In ‘Hort16A’, but not ‘Hayward’, stone cells are present in the outer pericarp (Hallett and Sutherland, 2005): in general, stone cells tend to be present in A. chinensis but absent from A. deliciosa (P. Sutherland, pers. comm.). The inner pericarp comprises locules in which there are two radial rows of seeds within a mucilaginous matrix (Ferguson, 1984). Clearly visible with little magnification are numerous calcium oxalate crystals in the inner pericarp around the seeds. While oxalic acid may be present in both soluble (oxalic acid, potassium oxalate, sodium oxalate) and insoluble forms (calcium oxalate crystals), it is the insoluble crystals that receive most attention, as one form of crystal is a needlelike raphide that may cause irritation in the throat and mouth when eaten (Perera et al., 1990; Walker and Prescott, 2003). The distribution of oxalate in the fruit is not uniform, being most concentrated in the skin and inner pericarp. Biologically, oxalate has tended to be regarded as a sink accumulating from excess ascorbate

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(Keates et al., 2000), and kiwifruit are typically high in ascorbate or vitamin C (Ferguson and MacRae, 1991). More recently, it has been suggested that oxalate formation is not simply a dead-end, but that its formation is regulated in association with ascorbate metabolism (Rassam and Laing, 2005). The presence of the oxalate crystals is significant when the calcium nutrition of the fruit is being considered, as a variable amount of calcium may be bound in the crystals and not be available physiologically. Hence while the total calcium content of ‘Hayward’ appears to be high (10–25 mg/100 g f.w.; Ferguson et al., 2003; Thorp et al., 2003) compared with that in fruit such as apples (Ferguson et al., 1980), the bound proportion must be taken into consideration in determining whether calcium is limiting in the fruit or not. This aspect of the calcium balance of the fruit may in part account for the variable reports on whether calcium plays a role in fruit firmness retention in ‘Hayward’ (Hopkirk et al., 1990; Gerasopoulos et al., 1996). The central core is white-ish and comprises large, homogeneous parenchyma cells. These cells also soften as the fruit ripen, although the timing of changes in the pericarp and core may differ. At the stem-end of the fruit there may be some sclerified tissue just below the picking scar that creates a hard ‘woody spike’, although in most fruit this is barely noticeable. A range of ripe fruit flesh colours exists within the Actinidia genus. These flesh colours include green, yellow, orange, red and purple. In ‘Hayward’ the green flesh colour present at harvest persists, or changes little, during storage and ripening. In contrast, the newer commercial introductions have included the yellow-fleshed A. chinensis fruit ‘Hort16A’ and ‘Jintao’, and also the yellow/red-fleshed ‘Hongyang’. The difference between cultivars in which the fruit flesh is green or yellow when ripe is the capacity to degrade chlorophyll. Both green- and yellow-fleshed fruit contain a similar range of pigments. These pigments include chlorophylls and carotenoids, including lutein and β-carotene (Gross, 1982; Watanabe and Takahashi, 1999; McGhie and Ainge, 2002). However, this does not mean there is no change in the colour of ‘Hayward’, just that it is very slow and while a decrease in chlorophyll has been recorded after storage (Ben-Arie et al., 1982), the loss may not be visibly noticeable. Chlorophyll loss in air storage may be more noticeable than in fruit stored in controlled atmospheres (CA) for 5–6 months, as CA retards chlorophyll loss, making for a noticeably greener flesh colour than in air-stored fruit (Lallu et al., 2005). The amount of chlorophyll in fruit may also differ at harvest depending on growing conditions. In ‘Hort16A’ fruit, the change in flesh colour from green to yellow occurs as the fruit mature and ripen (Patterson et al., 2003). There is no increase in the carotenoids during maturation or ripening, and it is their unmasking through a reduction in chlorophyll that causes the change in colour (Montefiori et al., 2009). However, degreening in ‘Hort16A’ is not tightly linked to other commonly measured fruit characteristics, such as soluble solids content (SSC) and firmness. Hence, depending on environmental conditions, ‘Hort16A’ fruit may be fully degreened, firm and with a low SSC, or may still be green yet soft and with a relatively high SSC. The basic chemical composition of ‘Hayward’ kiwifruit has been described in previous reviews (Beever and Hopkirk, 1990; Given, 1993; Cheah and Irving,

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1997; Perera et al., 1998). When considering these data, the following points should be considered. Firstly, much of the early work may have been undertaken on cultivars other than ‘Hayward’, such as ‘Bruno’. Secondly, the current crop loading and orchard management practices for ‘Hayward’ differ markedly from those in the earlier days of research. These changes in commercial practices (crop load, pruning for open canopies, girdling and the use of biostimulants) may alter the absolute compositional values, but not the fundamental nature of the fruit. Physical data on the heat transfer characteristics of ‘Hayward’ fruit relevant to cooling and storage have been published (Harris and McDonald, 1975). One fundamental aspect of kiwifruit physiology is the way in which nonstructural carbohydrates are accumulated within the fruit. The products of photosynthesis are initially stored in the fruit as starch, with a relatively low rate of increase in soluble sugars. Starch may comprise up to 50% of the dry matter of the fruit. Later, the developmental state of the fruit changes from starch, accumulation to starch breakdown and starch is converted to soluble sugars, resulting in a rapid increase in the rate of soluble sugar accumulation. The soluble sugars that result are mainly hexoses rather than sucrose. While myo-inositol is commonly found in plants, the concentrations found in kiwifruit are high compared with those in other plants (Bieleski et al., 1997). A. arguta differs from A. deliciosa and A. chinensis in that the fruit accumulate greater amounts of sucrose (Boldingh et al., 2000) and the trisaccharide planteose has been recorded as a short-term storage carbohydrate in the leaves (Klages et al., 1997). Early research on kiwifruit physiology reported that ethylene production increased in the fruit towards the end of ripening (Pratt and Reid, 1974). As a consequence, kiwifruit have been categorised as climacteric fruit. 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Index

ABG–3161, 52 Acca sellowiana [Berg] Burret, 115–31 culinary uses, nutritional value and health benefits, 119–20 general feijoa fruit facts, 119 cultivars and genetic variability, 118–19 origin, botany, morphology and structure, 115–17 flower and mature fruit on the tree, 117 ripening index for feijoa fruit, Plate X postharvest crop losses, 127–9 chilling injury, 127–8 insect pests and their control, 129 internal and external symptoms, Plate XI other physiological disorders, 128–9 pathological disorders, 129 physical damage, 128 postharvest handling factors affecting quality, 125–7 ethylene, 127 fruit size grading, 125 grading standards in Colombia, 126 handling and grading, 125–6 modified or controlled atmosphere, 126–7 temperature and relative humidity, 126 postharvest physiology and quality, 124–5 respiration and ethylene production, 124 ripening, quality components and ripening indices, 124–5 preharvest factors affecting fruit quality, 120–3

flowering and pollination, 120–1 fruit growth and development, 121–2 maturity and harvest, 122–3 modern feijoa orchard, 123 yield, 123 processing, 129–30 worldwide importance and economic value, 117–18 Acetobacter aceti, 29 Acetobacter bacteria, 59 Achradelpha mammosa see Pouteria sapota Jacq. H.E. Moore & Stearn Achras mammosa L. see Pouteria sapota Jacq. H.E. Moore & Stearn Acrostalagmus albus, 266 Actinidia spp., 326–53 commercial practice, 348–53 controlled atmosphere storage, 352–3 degreening, 350–1 harvest index, 349–50 temperature management, 351–2 future trends, 353 maturation, 331–3 physiological disorders, 341–3 impact and compression damage, Plate XXV low temperature breakdown, Plate XXIV postharvest handling, 346–8 postharvest pathology, 343–6 postharvest physiology, 333–41 low temperature responses, 339–41 ripening other than softening, 338–9 softening, 333–8

© Woodhead Publishing Limited, 2011

568

Index

vine and fruit, 327–31 fruit, 328–31 vine, 327–8 after-roast darkening, 467–8 air roasting, 466 alcohols, 88 Alphons see Mangifera indica L. Alphonso see Mangifera indica L. Alternaria rot, 526 Ameeri see Mangifera indica L. American Society for Testing Materials, 37 1-aminocyclopropane–1-carboxylic acid (ACC), 85 Amrapali see Mangifera indica L. amyloglucosidase (AMG), 176 Anastrefa fraterculus, 266 Anastrefa obliqua, 266 Anastrepha ludens, 529 Anastrepha ludens Loew, 230 Anastrepha obliqua, 529 Anastrepha suspense Loew, 230 anthocyanase, 371 anthocyanins, 365, 370, 371 anthracnose, 228, 376, 525 antioxidants, 457 aril necrosis, 97 artificial ripening, 307 Artocarpus heterophyllus Lam., 275–98 composition and nutritional value, 279–84 acidity and crude fibre, 280–1 biochemical constituents, 281 carbohydrate and fatty acid content, 281–2 changes during ripening and inter tree variability, 283–4 chemical composition, 283 phenolic content, 280 total soluble solids, 281 vitamins, minerals, amino acids and other constituents, 282–3 volatiles, 280 culinary uses, 278–9 economic value and overview of major uses, 277–8 jackfruit being sold in market, Plate XXII fruit growth, respiratory behaviour and ripening, 279 medicinal value, 278 origin, botany, morphology and structure, 275–6 pathological disorders and insect pests, 288 postharvest handling practices, 284–7 details, 286–7

preharvest factors affecting fruit quality and harvest timing, 284 processing, 288–95 beverages, jam and fruit bars, 292–4 by-products, 294–5 dehydrated products, 291–2 dehydration process protocol, 293 fresh-cut processing, 288, 290 frozen products, 294 hurdle technology-based shelf-stable product, 290–1 minimal processing protocol, 290 process protocol for hurdle technology-based processing, 291 products from immature jackfruit, 294 utilisation of jackfruit as various products, 289 worldwide importance, 276–7 hard and soft pulp varieties, Plate XXI Arumanis see Mangifera indica L. Ashwini see Mangifera indica L. Aspergillus flavus, 21 Aspergillus niger, 21 Aspergillus niger Van Tiegh, 60 Aspergillus nigri vars, 148 Aspergillus parasiticus, 60 Aspergillus rot, 187 Aspergillus rot, 526 Ataulfo see Mangifera indica L. Avogreen, 391 Bacillus subtilis, 391 Bactrocera spp, 529–30 Badami see Mangifera indica L. bagging, 313 Banganapalli see Mangifera indica L. Bappakai see Mangifera indica L. Batrocera correcta (Bezzi), 230 Beaumont guava, 218 beetle see Necrobia rufipes de Geer. Bellary see Mangifera indica L. Bengal see Litchi chinensis Sonn. berry ripening, 183 Betocera rufomaculata, 288 Beverly see Mangifera indica L. biocontrol agents, 388–9, 391–2 biodiesel, 37 bioelectrical resistance (BER), 170, 171 Bioriented Polypropylene (BOPP), 389, 390 black nose, 58 black rot, 60 bleaching, 188 blue mould see Penicillium expansum

© Woodhead Publishing Limited, 2011

Index Bo-Erica, 327 Bosworth–3 see Litchi chinensis Sonn. Botryodiplodia theobromae Pat, 60 Botryosphaeria, 345 Botrytis cinerea, 185–6, 431–2 Botrytis fuckeliana, 431–2 “Bou Faroua” disorder, 61 Bourbon see Mangifera indica L. BoxiBag, 389 Breba crop, 140 Brewster see Litchi chinensis Sonn. brown centres, 455 browning, 429–30 bruising, 128 bunch stem necrosis see waterberry Cadra cautella, 21 caffeic acid, 87 calcium, 306 Calocarpum mammosum see Pouteria sapota Jacq. H.E. Moore & Stearn Calyx-end fruit rot, 60 Cambiodiana see Mangifera indica L. Canarium odontophyllum Miq., 34–9 culinary uses, nutritional value and health benefits, 36–7 harvesting, 37–8 long bamboo pole with a sickle at the end is used, Plate V ‘Laja’ and ‘Lulong’ clones fruit nutritional values, 36 fruit physical characteristics, 36 maturity and quality components and indices, 38 origin, botany, morphology and structure, 34–6 fruit panicles with white immature dabai fruit, Plate IV postharvest handling factors affecting quality, 38–9 fruits after 7 days storage, 38 postharvest physiology, 37 canopy position, 221–2 caprification, 137 illustration, 138 Caprifigs, 137 Capulinia jaboticabae, 266 Carabao see Mangifera indica L. Caribbean fruit fly see Anastrepha suspense Loew Cecil see Mangifera indica L. centrifugal fluidised bed (CFB) drying, 549 Ceratitis capitata (Wiedemann), 265, 529 Ceratitis cosyr, 529

569

Ceratitis rosa, 529 Ceylon Jack see Artocarpus heterophyllus Lam. Champa Hazari see Artocarpus heterophyllus Lam. Chandrakaran see Mangifera indica L. Changhong 3 see Eriobotrya japonica L. chico-mamey see Pouteria sapota Jacq. H.E. Moore & Stearn chilling injury, 94 cocona fruit, 4 coconut, 20 durian, 96 feijoa, 127–8 fig, 147 golden apple, 169–71 guava, 223, 227–8 internal and external symptoms, Plate XI jaboticaba, 264 litchi, 373 loquat, 428–9 mango, 523 Chinese jujube see Ziziphus jujuba Mill. chitosan, 392–3 chlorine fertilisation, 17 Chuliang see Dimorcarpus longan Lour. chutney, 548 Cladosporium rot, 187 Clysar EHC–50 copolymer film, 519 Clysar EHC–100 copolymer film, 519 Clysar EH–60 film, 519 cocona see Solanum sessiliflorum Dunal coconut see Cocos nucifera L. Cocos nucifera L., 8–30 botany, morphology and structure, 8–9 fruit shape and colour, Plate III dwarf cultivars, 8–9 fruit biology and postharvest physiology, 11–12 growth, development and maturation, 11–12 respiration and ethylene production, 12 ripening behaviour, 12 maturity indices, 15–17 trimmed young coconut fruit, 16 origin, distribution, production area and trade value, 9–10, 11 average annual export and import statistics (1961–2007), 11 average annual harvested area, production and yield (1961–2008), 10 physiological disorders and pests, 20–1 mature coconut, 20–1 young coconut, 20

© Woodhead Publishing Limited, 2011

570

Index

postharvest handling factors affecting quality, 18–20 atmosphere, 19–20 humidity, 19 physical damage, 18 temperature, 18–19 postharvest handling practices, 21–6 consumer table, 26 harvest operations, 21–2 packing house practices, 22–4 recommended storage and shipping conditions, 25–6 ripening and senescence control, 24–5 preharvest factors affecting quality, 17–18 cross pollination, 17 light, 17 maturity, 18 nutrients, 17 processing, 26–9 coconut gel (nata de coco), 29 coconut water, 28–9 copra, 26–7 desiccated coconut, 27–8 milk, 28 oil, 27 roasted coconut, 29 quality components, 12–15 fruit shape, kernel and liquid content, 12–13 moisture, sugar, acid and oil content, 13–14 other components, 14–15 tall cultivars, 8–9 use: fresh, processed products and nutritional value, 10–11 Codex Stan 184—1993, 512 CODEX Standard, 55–6 Colleototrichum gloeosporiodes, 129 Colletotrichum acutatum, 434 Colletotrichum gloeosporioides, 5, 228, 376, 377, 431 Colletotrichum gloeosporioides Penz., 20 Colocarpum sapota (Jacq.) see Pouteria sapota Jacq. H.E. Moore & Stearn Common see Mangifera indica L. Conotrachelus myrciariae, 266 controlled atmosphere, 126–7, 147, 154, 314–15, 436–7 controlled atmosphere storage, 226–7, 352–3, 395–6 copper hydroxides, 5 copra, 26–7 coumarins, 477

Cryovac D955, 519 Cryptorhynchus mangiferae, 530–1 cubiú see Solanum sessiliflorum Dunal cumala see Pouteria lucuma (Ruiz and Pav.) Kuntze CX STAN 177–1991, 27–8 CX-STAN 210–1999, 27 Cyptosporiopsis, 345 dabai see Canarium odontophyllum Miq. Dasheri see Mangifera indica L. date see Phoenix dactylifera L. DC Tron, 539 defoliation, 4 Deglet Noor see Phoenix dactylifera L. dehydration, 188–9 dessechement ed al rafle see waterberry dielectric heating, 536 Dimorcarpus longan Lour., 408–19 arils of longan cv. ‘Shixia,’ Plate XXIX fruit tree of longan cv. ‘Shixia,’ Plate XXVIII marketing, 418 packaging, 415 postharvest characteristics, 409–12 composition, 409–10 ethylene evolution, 411 maturity, 409 nutritional composition per 100 g of longan fruit aril, 410 pathology, 412 peroxidative activity, 411 respiration, 411 texture, 410–11 ultrastructural changes, 411–12 postharvest handling, 412–15 fungicides, 413–14 handling system, 415 other handling technologies, 414–15 precooling, 412–13 recommendations for fungicide treatment, 413 recommendations for precooling, 413 sorting and grading, 412 processing, 418 storage, 416–17 ambient temperature, 416 low temperature, 416 modified and controlled atmospheres, 416–17 temperature recommendations for selected major cultivars, 416 transport, 417–18 export market, 417–18

© Woodhead Publishing Limited, 2011

Index local market, 417 recommendations for transport and marketing, 417 Diplodia natalensis, 432 durian see Durio zibethenus Merr. Durio zibethenus Merr., 80–109 distribution, production area and trade value, 81–2 production area and export volume in three leading producing countries, 82 fruit development and postharvest physiology, 82–6 growth, development and maturation, 82–5 respiration and ethylene production, 85 ripening behaviour, 85–6 width, length, weight and thickness during growth and development, 84 insect pests and their control, 99–100 internal insects, 100 surface insects, 100 maturity and harvesting indices, 88–93 days from anthesis, 89 dry matter content of aril, 89–91 fruit specific gravity, 92–3 fruit stem strength, 91 Monthong durians dry matter content, 90 sap sweetness from cut stem, 91–2 spine strength, 91 stem surface roughness, 91 swelling around abscission zone, 91 tapping sound, 89 maturity and quality components and indices, 86–93 antioxidant capacity, 87 fruit size and shape, 86–7 fruit stem, 87 lipid and pulp fibre content, 87 main volatiles in durians from three leading producing countries, 88 pigments, 87 volatiles, 88 origin, botany, morphology and structure, 80–1 fruit, cross section and dehiscence of durian, Plate VIII Monthong durian cross section, Plate IX pathological disorders, 98–9 Lasiodiplodia and others, 99 Phytopthora, 98–9 physiological disorders, 96–8 aril tip browning, 97 chilling injury, 96

571

Monthong durians firmness and uneven ripening score harvested from trees, 98 uneven fruit ripening, 97–8 water soaked core, 96–7 postharvest handling factors affecting quality, 94–6 atmosphere, 95–6 humidity, 95 others, 96 physical damage, 94 temperature, 94–5 postharvest handling practices, 100–6 controlled and modified atmosphere, 105–6 handling steps for durian exported from Thailand, 101 harvest operations, 102–3 packinghouse practices, 103 recommended storage and shipping conditions, 104–5 ripening and senescence control, 103–4 preharvest factors affecting fruit quality, 93–4 external factors, 93–4 internal factors, 93 rain and irrigation, 93–4 soil nutrients, 94 processing, 106–8 chip, 107–8 flour and powder, 108 fresh-cut durian, 106–7 frozen durian (pulp unit or whole fruit), 107 paste, 108 polyssacharide gel durian rind, 108 uses of fresh and processed products, and nutritional value, 82, 83 durian aril nutritional composition, 83 ‘Monthong’ durian aril antioxidant capacity and penolic contents, 83 Earligreen, 327 easy let-downs, 464 electrolyte leakage (EL), 170, 171 endosepsis, 147, 148 Ephestia cautella, 21 Eriobotrya japonica L., 424–39 culinary uses, nutritional value and health benefits, 425–6 different processed produced, Plate XXXI

© Woodhead Publishing Limited, 2011

572

Index

fruit ripening and resistance based on molecular and proteomic levels, 438 fruits of different varieties, Plate XXX integrative technologies for control of decay and chilling injury, 438–9 maturity and quality, 426–7 maturity characteristics, 426 quality characteristics, 426–7 nutrient compounds per 100 g of fruit, 425 physiological disorders, 428–31 browning, 429–30 chilling injury, 428–9 physical damage, 431 purple spot, 430–1 postharvest diseases, 431–2 Botrytis cinerea, 431–2 Colletotrichum gloeosporioides, 431 Diplodia natalensis, 432 Phytophthora palmivola, 432 Pseudomonas syringae, 432 postharvest physiology, 427–8 fruit physiological, physical and chemical changes, 427–8 respiration, ethylene production and ripening, 428 postharvest treatments, 432–4 decay control, 434 harvest operations, 432–3 packinghouse practices, 433 recommended storage and shipping conditions, 434 ripening and senescence control, 433–4 storage technologies, 435–8 controlled atmosphere conditions, 436–7 decay index and loquat fruit stored at CA for 50 days, 437 decay index and weight loss in different storage conditions, 437 hypobaric pressure storage, 437–8 low temperature storage, 435 modified atmosphere packaging, 435–6, 437 worldwide importance and economic value, 424–5 esters, 88 ethephon, 103, 106 ethylene, 37, 106, 127, 139, 152, 164, 165 ethylene diamine tetra-acetic acid (EDTA), 391 European Standard Organisation, 37 Ewais see Mangifera indica L. Extreme see Mangifera indica L.

Fay Zee Siu see Litchi chinensis Sonn. Fazli see Mangifera indica L. feijoa see Acca sellowiana [Berg] Burret Feizixiao see Litchi chinensis Sonn. fermentation spoilage see souring ficin, 136–7 Ficus carica L., 134–55 culinary uses, nutritional value and health benefits, 136–7 fruit development and postharvest physiology, 137–9 caprification, 138 development stages, externally and internally, Plate XII growth, development and maturation, 138–9 morphology and types, 137–8 respiration and ethylene production, 139 response to ethylene, 139 harvested at two different maturity stages ‘Brown Turkey’ fig, 142 ‘Kadota’ fig, 143 ‘Mission’ fig, 143 ‘Zidi’ fig, 144 insect pests and their control, 150 maturity, 142–4 internal differences at different stages, 142 ‘Panachee’ fig harvested at commercial maturity, 144 quality components and índices, 140 origin, botany, morphology and structure, 134–5 pathological disorders, 147–9 fresh figs susceptible to decay, 148 physiological disorders, 147 postharvest handling factors affecting quality, 145–7 atmosphere, 147 delayed cooling effect on weight loss of ‘Brown Turkey’ and ‘Kadota’ fig, 146 fresh figs physical damage, Plate XIII physical damage, 146 temperature management, 145–6 water loss, 146–7 postharvest handling practices, 150–4 ‘Brown Turkey’ figs manual harvesting, 151 containers types for packing fresh figs, 153 fresh figs are harvested into small containers, 151

© Woodhead Publishing Limited, 2011

Index harvest operations, 150–2 packing area, 152 packing figs at the side of field immediately after harvest, 153 packinghouse practices, 152 recommended storage and shipping conditions, 154 ripening and senescence control, 152–3 preharvest factors affecting fruit quality, 140–5 atmosphere, 147 Breba, 140–1 crops per year, 141 cultural practices, 145 fruit splitting, 141 genotype, 145 physical damages, 146–7 processing, 154–5 fresh-cut processing, 154 other processing practices, 154–5 respiration and ethylene production, 139 worldwide importance and economic value, 135 field packaging, 192 fig see Ficus carica L. fig pollination see caprification Fiji see Mangifera indica L. filtration technique, 28 flavour reversion, 456 floating technique, 92 flower thrips, 188 foot rot, 310 forced air cooling, 194, 195, 196 forced hot-air quarantine treatments, 534 free fatty acids (FFA), 456–7 fruit rot, 60, 228 fruit softening, 333–8 fruit splitting, 191 fruit worm see Neoleucenoides elegantalis fumigation, 62 gamma irradiation, 386 Generally Regarded As Safe compounds, 391 gibberellic acid, 104, 306 glacial acetic acid, 29 Goa see Mangifera indica L. Golden see Mangifera indica L. golden apple see Spondias dulcis Forst. syn. Spondias cytherea Sonn Good Agricultural Practices, 73 Good Hygienic Practices, 73 Good Manufacturing Practices, 73 Graham see Mangifera indica L.

573

grape berry moths, 188 gray mould see Botrytis cinerea Green Light, 327 Groff see Litchi chinensis Sonn. grosse sapote see Pouteria sapota Jacq. H.E. Moore & Stearn guava see Psidium guajava L. guava fruit fly see Batrocera correcta (Bezzi) Guiwei see Litchi chinensis Sonn. Gulabi see Artocarpus heterophyllus Lam. Haak Yip see Litchi chinensis Sonn. Haden see Mangifera indica L. Hansenula, 59 harvest index, 349–50 hayko, 161 Hayward see Actinidia spp. heat injury, 171 heat treatments, 387–8 Heiye see Litchi chinensis Sonn. hermaphroditic, 120 4-hexylresorcinol, 391 Higgins see Mangifera indica L. high temperature short time (HTST) pneumatic drying, 549 Hindi see Mangifera indica L. Hindy Sinnara see Mangifera indica L. Hong Huai see Litchi chinensis Sonn. Hongyang see Actinidia spp. Hort16A see Actinidia spp. hot water immersion, 532–3 hot water treatment, 230–1, 390–1 Huaizhi see Litchi chinensis Sonn. hydrochloric acid (HCI), 176 hydrolysis, 456 hypobaric pressure storage, 437–8 hypobaric storage, 317 Indarbela tetraonis, 288 Indian jujube see Ziziphus mauritiana Lam. indole acetic acid (IAA), 48 internal discoloration see brown centres International Macadamia Quality Standard, 454 irradiation, 231–2, 317, 535–6 Irwim see Mangifera indica L. jaboticaba see Myrciaria cauliflora (Mart.) O.Berg. [Myrtaceae] jackfruit see Artocarpus heterophyllus Lam. Jarra see Mangifera indica L. Jiefanfzhong see Eriobotrya japonica L.

© Woodhead Publishing Limited, 2011

574

Index

Jintao see Actinidia spp. jujube fruit shrink disease, 309 Julia see Mangifera indica L. Kaimana see Litchi chinensis Sonn. Kampuchea guava, 218 Kapa Benka see Artocarpus heterophyllus Lam. Kasargod see Mangifera indica L. Keitt see Mangifera indica L. Kensington Pride see Mangifera indica L. Kent see Mangifera indica L. Keow Savoey see Mangifera indica L. Kerosene see Mangifera indica L. kiwifruit see Actinidia spp. Kom see Litchi chinensis Sonn. Kradum, 82–5, 86–7, 91 Kurukkan see Mangifera indica L. Kwai May Pink see Litchi chinensis Sonn. Kwai Mi see Litchi chinensis Sonn. Langra see Mangifera indica L. Lasiodiplodia sp., 171 Lasiodiplodia theobromae, 377 Lasiodiplodia theobromae, 99 LDPE see low density polyethylene lipolysis, 455, 456 litchi see Litchi chinensis Sonn. Litchi chinensis Sonn., 361–98 constraints during long-term storage and export, 370–9 chilling injury, 373 foodborne pathogens, 377–9 micro-cracking and fruit cracking, 373–4 pericarp browning and desiccation, 370–3 fruit composition, 365–8 aroma volatiles, 367–8 ascorbic acid and mineral content, 366–7 sugars and acids, 365–6 fruit development, maturation and composition, 363–8 chemical index for litchi maturity, 364 colour and phenolic components in the pericarp, 364–5 growth, development, maturation and respiration, 363 maturity indices and quality components, 364 good quality litchi fruits production for postharvest export chain, 368–70 fertiliser application for good quality fruit, 368–70 orchard management, 370

modified atmosphere storage, 389–95 biocontrol agent, 391–2 chitosan, 392–3 Generally Regarded As Safe compounds, 391 hot water treatment, 390–1 1-methylcyclopropene, 393–5 origin, botany, morphology and structure, 361–2, Plate XXVI packing line operation and cold chain management, 385–6 sorting and size grading, 385 temperature management, 385–6 postharvest chain and packhouse treatments, 381–6 HCl dips, 384 metabisulphite salts, 384–5 sulphur dioxide fumigated fruit after 21 days storage, 382 sulphur dioxide fumigation, 381, Plate XXVII sulphur dioxide fumigation procedure, 383–4 undesirable effects of sulphur dioxide fumigation, 381–3 postharvest decay, 374–7 microbial ecology of litchi, 374–5 postharvest pathogens affecting litchi, 375–7 postharvest picking, in-field sorting and transport, 379–81 harvesting litchi, 380 postharvest technologies developments, 386–96 biocontrol agents, 388–9 controlled atmosphere storage, 395–6 gamma irradiation, 386 heat treatments, 387–8 postharvest dip treatments, 386–7 processing, 396–7 canning, 397 drying, 396–7 fresh-cut processing, 396 worldwide importance, 362–3 longan see Dimorcarpus longan Lour. loquat see Eriobotrya japonica L. low density polyethylene, 168 low temperature conditioning (LTC), 435 lucma see Pouteria lucuma (Ruiz and Pav.) Kuntze lucmo see Pouteria lucuma (Ruiz and Pav.) Kuntze lucuma see Pouteria lucuma (Ruiz and Pav.) Kuntze

© Woodhead Publishing Limited, 2011

Index lúcuma see Pouteria lucuma (Ruiz and Pav.) Kuntze lúcumo see Pouteria lucuma (Ruiz and Pav.) Kuntze Luluma mammosa see Pouteria sapota Jacq. H.E. Moore & Stearn Luoyangqing see Eriobotrya japonica L. Mabrouka see Mangifera indica L. macadamia see Macadamia spp Macadamia integrifolia, 450–69 Macadamia jansenii, 450 Macadamia spp, 450–69 culinary uses, nutritional value and health benefits, 451–2 drying effects on quality, 461–3 drying methods, 462–3 drying regimes for macadamia nut-in-shell, 463 factory processing, 464–8 after-roast darkening, 467–8 cracking, 464–5 dry roasting method used by a processor, 468 roasting, 465–7 roasting regimes in air, 467 roasting regimes in vegetable oils, 467 handling and physical damage, 464 origin, botany, morphology and structure, 450–1 fruit morphology, Plate XXXIII preharvest factors affecting nut quality, 458–9 crop management, 458–9 cultivar and site, 458 cultivar differences for oil content in different regions of Eastern Australia, 458 pests and disease, 459 pre-harvest physiology, 452–3 fruit growth and development, 452–3 mature fruit structure, 453 quality and the on-farm postharvest chain, 460–1 dehuskers and macadamia quality, 460–1 harvest operations, 460 sorting and resorting, 461 quality components and indices, 453–7 appearance, 455 importance of antioxidants, 457 oil content and immaturity, 454 quality defects, 454–5 rancidity and shelf life, 455–7 shoulder damage, Plate XXXIV

575

worldwide importance and economic value, 451 Macadamia tetraphylla, 450–69 Madras see Litchi chinensis Sonn. Magiferae indica, 171 malondialdehyde, 411 mamey see Pouteria sapota Jacq. H.E. Moore & Stearn mamey apple see Mammea americana L. mamey colorado see Pouteria sapota Jacq. H.E. Moore & Stearn Mammea americana L., 474–80 culinary uses, nutritional value and health benefits, 475–7 fruit development and postharvest physiology growth, development and maturation, 477 respiration, ethylene production and ripening, 477 insect pests, 478 maturity and quality components and indices, 477 nutrient value per 100 g of fruit, 476 origin, botany, morphology and structure, 474–5 tree and fruit, Plate XXXV pathological disorders, 478 physiological disorders, 478 postharvest handling factors affecting quality atmosphere, 478 temperature management, 478 postharvest handling practices, 478–9 harvest operations, 478 recommended storage and shipping, 479 ripening and senescence control, 479 processing, 479 worldwide importance, 475 mammee apple see Mammea americana L. mammein, 477 mammey sapote see Pouteria sapota Jacq. H.E. Moore & Stearn mammon see Pouteria lucuma (Ruiz and Pav.) Kuntze Mancozeb, 5 Mangifera indica L., 492–550 botany, morphology and structure, 494 chemicals effect on quality, 514–15 growth regulators, 515 pests and disease control, 514–15 composition of edible portion, 498–9

© Woodhead Publishing Limited, 2011

576

Index

control of pathological diseases, 526–8 biological control, 526–7 chemical treatments, 527 heat treatments, 527–8 irradiation, 528 external and internal colour changes during maturation and ripening, Plate XXXIX fruit development and postharvest physiology, 501–9 compositional changes during fruit maturation and ripening, 504–8 growth, development and maturation, 501 manipulation of postharvest physiology by molecular biology, 508–9 respiration, ethylene production and ripening, 501–4 insect pests, 528–31 fruit flies, 529–30 mango weevils, 530–1 insect quarantine treatments, 531–6 chemical control, 531–2 heat treatments, 532–4 irradiation, 535–6 modified and controlled atmospheres, 534–5 ‘Manila’ fruit, 495 maturity and quality components and indices, 509–12 use of computation in different ASEAN countries, 511 nutritional value and health benefits, 497–501 pathological diseases, 524–6 Alternaria rot, 526 Anthracnose, 525 Aspergillus rot, 526 other diseases, 526 stem-end rot, 525 physiological disorders, 521–4 biennial bearing, 521 chilling injury, 523 internal breakdown, 522 other physiological disorders, 523–4 postharvest handling factors affecting quality, 515–21 atmosphere, 516–21 physical damage, 515–16 temperature management, 515 transpiration and water loss, 516 postharvest handling practices, 536–44 clamshell for six ‘Ataulfo’ mangoes, 543

harvesting and collection of mango, 536 harvest operations, 536–9 latex exudates on mango fruit, 537 mango package, 542 mango packinghouse, Plate XL packinghouse practices, 539–43 recommended storage and shipping conditions, 544 ripening and its control, 543 washing of mango fruit in packinghouse, 540 waxing, 540–1 preharvest factors affecting fruit quality, 513–15 bagging, 515 fertilisation, 514 light, 513 rainfall and irrigation, 514 temperature, 513–14 processing, 544–9 fresh-cut, 544–7 other processing practices, 548–9 ‘Tommy Atkins’ external and internal colour changes, Plate XXXVIII tree and fruit, 493 worldwide importance and economic value, 494–7 mango see Mangifera indica L. mango juice, 548–9 mango nectar, 548–9 mango squash, 549 mango weevil see Cryptorhynchus mangiferae Manila see Mangifera indica L. marco see Pouteria lucuma (Ruiz and Pav.) Kuntze Margaronia caecalis, 288 marmalade-fruit see Pouteria sapota Jacq. H.E. Moore & Stearn marmalade-plum see Pouteria sapota Jacq. H.E. Moore & Stearn mature coconut maturity indices, 17 physiological disorders and pests, 20–1 disease, 20–1 growth, 21 insect damage, 21 rodent damage, 21 postharvest handling factors affecting quality, 18–20 atmosphere, 20 humidity, 19

© Woodhead Publishing Limited, 2011

Index physical damage, 18 temperature, 19 postharvest handling practices, 21–6 harvest operations, 22 packing house practices, 24 recommended storage and shipping conditions, 26 ripening and senescence control, 25 quality components, 12–15 moisture, sugar, acid and oil content, 13–14 other components, 14–15 mature-green stage, 493 Mauritius see Litchi chinensis Sonn. Mazagaon see Mangifera indica L. McLean’s Red see Litchi chinensis Sonn. mealybugs, 188 Mediterranean fruit fly see Ceratitis capitata (Wiedemann) methyl bromide, 62, 201 methyl bromide (MeBr), 531–2 1-methylcyclopropene, 127, 305–6, 393–5 Mexican fruit fly see Anastrepha ludens Loew Misk see Mangifera indica L. modified atmosphere packaging, 224–5, 389–95, 435–6 Mogi see Eriobotrya japonica L. Monthong durian, 82–5, 91 antioxidant capacity and penolic contents, 83 cross section, Plate IX dry matter content, 90 firmness and uneven ripening score harvested from trees, 98 morphactin, 229 Mudaria magniplaga Walker, 100 Muttam Varikha see Artocarpus heterophyllus Lam. Myrciaria cauliflora (Mart.) O.Berg. [Myrtaceae], 246–70 culinary uses, nutritional value and health benefits, 252–4 chemical composition, 253 common phenolics, 254 fruit development and postharvest physiology, 254–6 growth, development and maturation, 254–5 pigment content, 255 respiration, ethylene production and ripening, 255–6 insect pests, 265–6 important pests, 265

577

maturity and quality components and indices, 256–60 anthocyanin content, 260 changes in organic acids after flowering, 258 non-structural carbohydrates content, 257 structural carbohydrates content, 259 origin, botany, morphology and structure, 246–51 Brazilian centres of diversity for native fruits, 247 development into fruits and flowers, Plate XX dry matter accumulation and volume change, 250 genetic similarity pattern, 249 main species, common names and origins, 248 morphological aspects, 251 pathological disorders, 264–5 important diseases, 264 physiological disorders, 264 postharvest handling factors affecting quality, 261–4 atmosphere, 263–4 physical damage, 262 temperature management, 261–2 water loss, 262–3 postharvest handling practices, 266–8 harvest operations, 266 packinghouse practices, 267 recommended storage and shipping conditions, 267–8 preharvest factors affecting fruit quality, 260–1 processing, 268–70 fresh-cut processing, 268 jelly, 269–70 liqueur, 268–9 phenolics, tannins, anthocyanins and antioxidants, 269 total acidity, volatile acidity, alcohol content, pH, 270 vinegar, 270 wine, 269 worldwide importance and economic value, 251–2 Myrciaria tenella, 250 Myrciaria trunciflora, 250 Namdokami see Mangifera indica L. Nam Dok Mai see Mangifera indica L. Nang Klang Wun see Mangifera indica L.

© Woodhead Publishing Limited, 2011

578

Index

nata de coco, 29 Necrobia rufipes de Geer., 21 Neoleucenoides elegantalis, 5 Nileswar Dwarf see Mangifera indica L. nitric oxide, 306 NOM-FF–58–1985, 512 non-enzymatic (Maillard) browning, 130 Numici see Litchi chinensis Sonn. Nuomici see Litchi chinensis Sonn. nuts, 418 oil roasting, 466 Olour see Mangifera indica L. organoleptic tests, 162 Oro see Mangifera indica L. oxalic acid/ammonium oxalate (OAAO), 176 Paho see Mangifera indica L. Pairi see Mangifera indica L. PAL enzyme, 394 Palmer see Mangifera indica L. Palo see Pouteria lucuma (Ruiz and Pav.) Kuntze palo negro see waterberry Parrot see Mangifera indica L. pasteurisation, 68 Peach/Apricot see Mangifera indica L. peach tomato see Solanum sessiliflorum Dunal pectin, 176 Pectinex Ultra SP-L, 176 Pelliculana salmonicolor, 288 Penconazol, 5 Penicillium expansum, 186–7 Penicillum spp, 375–6, 388 perforated MA, 520 Peronophythora litchi, 377 peroxidase (POD), 371–2 Phoenix dactylifera L., 41–74 Barhee dates, Plate VI control methods, 61–3 biological control, 63 fumigation, 62 high temperatures, 61 ionising radiation, 62 low temperatures, 61–2 modified atmospheres and controlled atmospheres, 63 dates market in Saudi Arabia, 42 factors affecting fruit development and ripening, 46–7 mineral nutrition, 47

relative humidity and rainfall, 46–7 temperature, 46 food safety considerations, 72–3 fruit growth and development, 45–50 biochemical changes, 48–50 fruit set, 45–6 fruit thinning, 46 growth pattern, 47 growth regulators, 47–8 pollination, 45 harvesting, 63–6 illustration, 65 removing defective dates from strands, 65 roadside selling in southern Tunisia, 64 insect pests, 60–1 maturity and harvesting indices, 53–4 nutritional components and health benefits, 50–2 pathological disorders, 59–60 disease control strategies, 60 fungi, 59–60 souring, 59 physiological disorders, 57–9 black nose, 58 darkening, 57 internal breakdown, 58 mixed green, 59 skin separation (puffiness), 57–8 splitting, 59 sugar spotting (sugaring), 58 white nose, 58–9 postharvest handling factors affecting quality, 57 postharvest handling practices, 63–72 dehydration, 67 handling organic dates, 71–2 hydration, 67–8 pasteurisation, 68 ripening, 66–7 storage condition, 70–1 postharvest physiology, 52–3 ethylene production and responses, 52 respiration, 52 responses to modified and controlled atmospheres, 53 preharvest factors affecting postharvest fruit quality, 56–7 preparation for market, 68–70 cleaning, 68 cooling, 69–70 ‘Deglet Noor’ dates consumer packages, 70 packaged dates, 69

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Index packaging, 69 sizing, 68–9 sorting, 68 surface coating, 69 processing, 72 production in some important producing countries (2007), 42 quality indices, 54–6 characteristics and criteria, 54–5 protective covers for date bunches, 55 standard grades, 55–6 US standard, 56 removing defective dates from bunches, Plate VII Tamar stage of ‘Deglet Noor’ dates, 44 Phomopsis artocarpina, 288 phosphine, 62 Phyrdenus muriceus Germar, 5 Phytophthora fruit rot, 228 Phytophthora infestans, 5 Phytophthora palmivola, 432 Phytopthora palmivora Butler, 98, 99 Pichia anomala Moh93, 229 Pichia anomala Moh104, 229 pickles, 548 Pico see Mangifera indica L. Pierie see Mangifera indica L. Planococcus pacificus Cox, 5 polgalacturonase (PG), 86 pollination, 45 polyethylene plastic bag, 38–9 polyphenolic compounds, 429–30 polyphenol oxidase (PPO), 371–2, 391, 429–30 polyphenol oxydase (PPO), 128–9 postharvest dip treatments, 386–7 potash, 514 potassium fertiliser, 17 Pouteria lucuma (Ruiz and Pav.) Kuntze, 443–8 classification on basis of peel and pulp colour, 446 culinary uses, nutritional value and health benefits, 444–5 fruit development and postharvest physiology growth, development and maturation, 445 respiration, ethylene production and ripening, 445 insect pests and their control, 447 maturity and quality components and indices, 446 nutritional value per 100 g of fruit, 445

579

origin, botany, morphology and structure, 443–4 fruit structure, Plate XXXII physiological disorders, 446 postharvest handling factors affecting quality physical damage, 446 temperature management, 446 water loss, 446 postharvest handling practices harvest operations, 447 recommended storage and shipping conditions, 447 ripening and senescence control, 447 processing, 447–8 worldwide importance, 444 Pouteria sapota Jacq. H.E. Moore & Stearn, 482–9 chilling injury, 486 culinary uses, nutritional value and health benefits, 483–4 fruit sold in Mexico, Plate XXXVII mamey sapote fruit, Plate XXXVI insect pests and their control, 487 maturity and quality components and indices, 485 nutrient value per 100 g of fruit, 484 origin, botany, morphology and structure, 482–3 pathological disorders, 486–7 physiological disorders, 486 postharvest handling factors affecting quality, 485–6 temperature management, 485–6 water loss, 486 postharvest handling practices, 487–8 harvest operations, 487 packinghouse practices, 487 recommended storage and shipping conditions, 488 ripening and senescence control, 488 ripening rates in fruits after ethylene treatments, 488 postharvest physiology, 484–5 processing, 488–9 worldwide importance, 483 pozol, 484 preharvest bagging, 221 Prochloraz, 388 prochloraz, 229 “Pro-long” semipermeable fruit coating, 521 Pseudomonas solanacearum, 5 Pseudomonas syringae, 432

© Woodhead Publishing Limited, 2011

580

Index

Psidium guajava L., 213–39 maturity indices, 219–20 origin, botany, morphology and structure, 213–14 guava fruit and leaves, 214 salmon to pink-fleshed guava fruit, Plate XIX white-fleshed guava fruit, Plate XVIII physiological disorders, 227–8 postharvest handling factors affecting fruit quality, 222–7 physical damage, 223–4 temperature management, 222–3 postharvest handling practices, 232–5 harvest operations, 232 packinghouse practices, 233–4 recommended storage and shipping, 235 ripening and senescence control, 234–5 postharvest insect-pests and phytosanitary treatments, 230–2 heat and cold treatments, 230–1 irradiation, 231–2 postharvest pathological disorders, 228–30 postharvest physiology, 216–19 biochemical changes during fruit ripening, 218–19 fruit growth, development and maturation, 216–17 respiration and ethylene production, 217–18 preharvest factors affecting fruit quality, 220–2 canopy position and tree age, 221–2 fruiting season, 220 mineral nutrients, growth regulators and other chemicals, 222 orchard practices, 221 processing, 235–8 fresh-cut, 235–6 other processed products, 237–8 storage atmosphere, 225–7 controlled atmosphere, 226–7 short-term modified atmosphere exposure, 225–6 uses, nutritional value and health benefits, 215–16 water loss, 224–5 modified atmosphere packaging, 224–5 surface coatings, 225 worldwide distribution and economic importance, 214–15 major cultivars, 215

Puccinia psidii Wint., 264 purple spot, 430–1 putrescine, 429 Pythium, 5 quarantine treatment, 129 quercetin, 87 Rad see Mangifera indica L. rancidity, 455–6 Raspuri see Mangifera indica L. Rataul see Mangifera indica L. reddish-brown beetle see Tribolium castaneu Herbst relative humidity, 95 Rhizoctonia, 5 Rhizopus, 526 Rhizopus artocarpi, 288 Rhizopus nigricans Ehr, 60 Rhizopus rot, 187 Rhizopus sp., 21 ripe fruit mealy bug see Planococcus pacificus Cox ripe rots, 345 root-knot nematodes, 150 rots, 344 rucma see Pouteria lucuma (Ruiz and Pav.) Kuntze Sabre see Mangifera indica L. Saigon see Mangifera indica L. Salem see Mangifera indica L. Sammar Bahisht see Mangifera indica L. Sammini see Mangifera indica L. sanitation standard operating procedures, 73 sapote see Pouteria sapota Jacq. H.E. Moore & Stearn sapote mamey see Pouteria sapota Jacq. H.E. Moore & Stearn Seda see Pouteria lucuma (Ruiz and Pav.) Kuntze Sensation see Mangifera indica L. Septoria solanicola, 5 shanking see waterberry sheet pitting, 169 Shixia see Dimorcarpus longan Lour. short-term modified atmosphere, 224–5 shoulder damage, 455 Simmonds see Mangifera indica L. Singapore Jack see Artocarpus heterophyllus Lam. SmartFresh, 334 SMS solution, 25

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Index smut, 148 Solanum sessiliflorum Dunal, 1–6 composition, 3 culinary uses, nutritional value and health benefits, 3 fruit development and postharvest physiology, 3–4 growth, development and maturation, 3–4 respiration and ethylene production and ripening, 4 insect-pests and their control, 5 maturity and quality components and indices, 4 origin, botany, morphology and structure, 1–2 fruit, Plate II plants showing immature and mature fruits, Plate I pathological disorders, 5 physiological disorders, 4–5 postharvest factors affecting quality, 4 postharvest handling practices, 6 preharvest factors affecting quality, 4 processing, 6 worldwide importance and economic value, 2 soluble solids concentration, 140 Souey Tung see Litchi chinensis Sonn. souring, 148 South America apricot see Mammea americana L. spermidine, 429 spermine, 429 Spondias dulcis Forst. syn. Spondias cytherea Sonn, 159–77 culinary uses, nutritional value and health benefits, 161–2 fruit development and postharvest physiology, 162–5 changes during growth and development, 163 compositional changes, 164 ethylene production at three stages of fruit maturity during storage, 165 growth, development and maturation, 162 respiration and ethylene production and ripening, 162–5 insect pests and control, 172–3 mature green and ripe fruits, Plate XV maturity indices and quality components, 165–6

581

origin, botany, morphology and structure, 159–60 miniature and large types, Plate XIV packaging and waxing effect bioelectrical resistance, 169 electrolyte leakage, 170 percentage marketable and decayed fruits, 168 pathological disorders, 171–2 physiological disorders, 169–71 chilling injury, 169–71 heat treatments effect on selected quality attributes, 170 other physiological disorders, 171 postharvest handling factors affecting quality, 166–9 atmosphere, 168 physical damage, 167 temperature management, 166–7 water loss, 167–8 postharvest handling practices, 173–5 harvest operations, 173 packinghouse practices, 173–4 recommended storage and shipping conditions, 174–5 ripening and senescence control, 174 preharvest factors affecting fruit quality, 166 processing, 175–6 fresh-cut processing, 175 other processing options, 175–6 worldwide importance and economic value, 160–1 spray-dried mango powders, 549 SSC see soluble solids concentration stationary lag stage, 183 St Domingo apricot see Mammea americana L. stem-end rot, 344–5, 525 stiellahme see waterberry Strawberry see Mangifera indica L. stylar end rot, 228 Sukkary see Mangifera indica L. sulphur dioxide, 130 fumigation, 149, 381–4 generator pads, 198–9 treatments, 196–201 alternatives, 200–1 dosages, 197 effect of temperature on toxicity, 197 evolution of concentration from generating pad, 199 evolution of gas obtained with generating pad, 200

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582

Index

mode of action, 196–7 post-packaging fumigation, 198–200 pre-packaging fumigation, 198 tolerance, 200 Summerkiwi, 327 sunbathe, 37 sun drying, 549 superoxide dismutase, 411 Suvamarekha see Mangifera indica L. syconium, 137 TA see titratable acidity table grapes see Vitis vinifera L. Taimour see Mangifera indica L. Tai So see Litchi chinensis Sonn. Tanaka see Eriobotrya japonica L. terpinolene, 538 thick liquid disease, 309–10 titratable acidity, 140 Tommy Atkins see Mangifera indica L. Tongbi see Dimorcarpus longan Lour. Tongdum see Mangifera indica L. Top Star, 327 total titratable acidity, 162 Totapuri see Mangifera indica L. touch picking, 122, 124 Toxoptera aurantii, 266 Tribolium castaneu Herbst, 21 Trigonas spinipes, 266 Tuzhong see Dimorcarpus longan Lour. ultra high temperature (UHT), 28 ultraviolet light-C, 236 UN/ECE standard FFV–45, 513 United States Environmental Protection Agency (USEPA), 62 unsound kernel, 454, 458 Vapogard, 387 vapour heat treatment, 231, 533–4 vibration method, 92 vinegar flies, 188 Vitellaria mammosa see Pouteria sapota Jacq. H.E. Moore & Stearn Vitis vinifera L., 179–207 abiotic agents, 188–92 berry splitting and hairline cracks, 190 bleaching, 188 bleaching symptoms, Plate XVI browning symptoms, Plate XVII dehydration, 188–9 hairline cracks, 189 shatter, 189–90 skin and flesh browning, 190–1

splitting, 191 waterberry, 191–2 biotic factors, 185–8 Aspergillus rot, 187 blue mould, 186–7 Cladosporium rot, 187 gray mould, 185–6 gray mould symptoms, 186 insect damage, 188 other decay fungi, 187–8 Rhizopus rot, 187 cultivars, 180 maximum storage time, deterioration factors and origin, 180 deterioration factors, 184–92 fruit anatomy, 181–2 cluster and berry components, 181 physiology of berry growth and maturation, 182–4 development, accumulation of soluble solid and titratable acidity of “Thompson Seedless,” 182 respiration heat, 184 postharvest handling and packaging, 192–6 cooling operation, 194–6 forced air cooling, 195 harvest operation, 192 labelling, 193 packaging operation, 192–3 pallets with two box arrangement types, 194 working table in packing line operation, 193 processing, 204–7 quarantine treatments, 201 methyl bromide fumigation, 201 raisins, 204–7 dried-on-vine, 206 grape cultivars and type of raisins, 204–5 grape drying, 205 grape harvesting, 205 hot-air drying, 206 processing, 206–7 production process, 205 sun-dried, 205 sulphur dioxide treatments, 196–201 alternatives, 200–1 dosages, 197 effect of temperature on toxicity, 197 evolution of concentration from generating pad, 199

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Index evolution of SO2 gas obtained with generating pad, 200 mode of action, 196–7 post-packaging fumigation, 198–200 pre-packaging fumigation, 198 tolerance, 200 temperature management, 196 transport, 202–3 dewpoint temperature, 203 marine containers, 202–3 pallet distribution inside container, 203 Wai Chee see Litchi chinensis Sonn. water activity, 461 waterberry, 191–2 water soaked core see wet core waxing, 168 wet core, 96 white nose, 58–9 wind damage, 128 Wuxing see Eriobotrya japonica L. Xanthomonas campestris pv., 171 xenia effect, 17 Xtend, 389, 390 yellow jackets, 188 young coconut maturity indices, 15–17 trimmed young coconut fruit, 16 physiological disorders and pests, 20 postharvest handling factors affecting quality, 18–20 atmosphere, 19–20 humidity, 19 physical damage, 18 temperature, 18–19 postharvest handling practices, 21–5 harvest operations, 21–2 packing house practices, 22–4 recommended storage and shipping conditions, 25 ripening and senescence control, 24–5 quality components moisture, sugar, acid and oil content, 13 Zaozhong 6 see Eriobotrya japonica L. zapote see Pouteria sapota Jacq. H.E. Moore & Stearn Zebda see Mangifera indica L. ZESPRI, 327 Zill see Mangifera indica L. Ziziphus jujuba Mill., 299–321 nutritional value and health benefits, 300–3

583

Dongzao jujube grading standard, 303 nutrition content, 301–2 red jujube grading standard, 303 origin, botany and morphology, 299–300 varieties, Plate XXIII postharvest disorders, 311 postharvest handling, 318–19 grading, 318 packaging, 318–19 storage at ambient temperature, 318 postharvest pathology, 307–10 diseases, 308–9 foot rot of fruit stem, 310 jujube fruit shrink disease, 309 thick liquid disease, 309–10 postharvest pathology and entomology, 307–11 postharvest entomology, 311 postharvest pathology control, 310–11 biological control, 310–11 physical and chemical control, 310 postharvest treatments to extend shelf-life, 313–18 calcium solution treatment, 316 chlorine dioxide treatment, 316 controlled atmosphere, 314–15 ethanol treatment, 317 heat treatment, 317–18 hypobaric storage, 317 irradiation, 317 low-temperature storage, 313–14 other treatments, 318 ozone application, 315 preservative treatments, 316 preharvest treatments to extend shelf life, 312–13 bagging, 313 calcium treatment, 312–13 varieties and harvest maturity, 312 processing, 319–21 candied jujube, 320 dehydrated jujube products, 319 frozen jujube fruit, 321 jujube juice and beverages, 320–1 processed Chinese jujube, 320 ripening behaviour and postharvest physiology, 304–7 artificial ripening, 307 ethylene and carbon dioxide evolution rates, 304–5 ripening behaviour, 304 treatments to reduce respiration and ethylene rates, 305–6 calcium, 306

© Woodhead Publishing Limited, 2011

584

Index

gibberellic acid, 306 low pressure, 305 low temperature, 305 1-methylcyclopropene, 305–6 nitric oxide, 306 Ziziphus mauritiana Lam., 299–321 nutritional value and health benefits, 300–3 Dongzao jujube grading standard, 303 nutrition content, 301–2 red jujube grading standard, 303 origin, botany and morphology, 299–300 postharvest disorders, 311 postharvest handling, 318–19 grading, 318 packaging, 318–19 storage at ambient temperature, 318 postharvest pathology, 307–10 diseases, 308–9 foot rot of fruit stem, 310 jujube fruit shrink disease, 309 thick liquid disease, 309–10 postharvest pathology and entomology, 307–11 postharvest entomology, 311 postharvest pathology control, 310–11 biological control, 310–11 physical and chemical control, 310 postharvest treatments to extend shelf-life, 313–18 calcium solution treatment, 316 chlorine dioxide treatment, 316 controlled atmosphere, 314–15

ethanol treatment, 317 heat treatment, 317–18 hypobaric storage, 317 irradiation, 317 low-temperature storage, 313–14 other treatments, 318 ozone application, 315 preservative treatments, 316 preharvest treatments to extend shelf life, 312–13 bagging, 313 calcium treatment, 312–13 varieties and harvest maturity, 312 processing, 319–21 candied jujube, 320 dehydrated jujube products, 319 frozen jujube fruit, 321 jujube juice and beverages, 320–1 ripening behaviour and postharvest physiology, 304–7 artificial ripening, 307 ethylene and carbon dioxide evolution rates, 304–5 ripening behaviour, 304 treatments to reduce respiration and ethylene rates, 305–6 calcium, 306 gibberellic acid, 306 low pressure, 305 low temperature, 305 1-methylcyclopropene, 305–6 nitric oxide, 306 Zygosaccharomyces, 59

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Plate I (Chapter 1) Cocona plants grown as an annual crop showing immature and almost mature fruits as well as plant and leaf size under this system. Notice the hairy young fruits.

Plate II (Chapter 1) Cocona fruit. Notice the greenish color of ripening fruit and the soft pulp in the inside that contains the seeds. Fruits have been wiped to remove hairs.

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Plate III (Chapter 2) (a) different shape and color of coconut fruit; (b) a young coconut of ‘one and a half layer’ stage. Its cross section showing the white portion of the solid endosperm (kernel) at the stylar end and the translucent portion at the stem end. Notice the long rachillae attached to the top of the fruit; (c) germinating mature coconut. Notice the haustorium, the young shoot and root; (d) de-husked coconut showing the three ridges dividing the three carpels on the stylar end, and the three eyes on the stem end of the fruit. Notice the soft eye is in the largest segment; (e) trimming of young coconut beginning with chopping off the green skin; (f) trimming of young coconut followed by slicing off the body of the fruit.

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Plate IV (Chapter 3) Fruit panicles with white immature dabai fruit, turning purplish pink and powdery black colour on ripening.

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Plate V (Chapter 3) Harvesting dabai fruit by placing a net on the ground and climbing up the tree, then using a long pole with a sharp sickle at its end to harvest branches with fruits.

Plate VI

(Chapter 4) Barhee (Barhi) dates.

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Plate VII

(Chapter 4) Removing defective dates from bunches.

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Plate VIII (Chapter 5) (a) durian fruit from well (left) and poorly (right) pollinated flowers; (b) the swelling around the abscission zone of durian stem; (c) durian pulp after dehusking; (d) peltate hair on durian spine (courtesy of S. Sangchote); (e) cross section of a durian fruit showing uneven iodine-starch staining of the aril; (f) dehiscence of a durian.

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Plate IX (Chapter 5) (a) a cross section of a ripe Monthong durian fruit showing air space between the aril and the husk (notice that most seeds are aborted); (b) checking durian maturity by determining dry matter of the aril using a microwave oven; (c), a chilling injury symptom on durian husk; (d) Phytophthora rot on a durian fruit; (e) a durian dehusking tool (courtesy of S. Seehawong); (f) durian paste on display shelf.

Plate X (Chapter 6) Ripening index for feijoa fruit (a) seed pulp half white, half clear; (b) all of seed pulp area clear, (c) all of seed pulp area clear, but darkening (greyish); (d) seed pulp is completely brown, (e) seed pulp and flesh are brown. (a)–(b) mature fruit – for fresh consumption; (c) fruit for processing; (d)–(e) late senescence (developed by The New Zealand Institute for Plant & Food Research limited, Mt Albert, New Zealand).

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Plate XI (Chapter 6) Chilling injury in feijoa. (a) Internal symptoms include vascular browning and pink discoloration of the flesh; (b) external symptoms include longitudinal browning of the skin.

Plate XII

(Chapter 7) Different stages of fig fruit development, externally and internally.

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Plate XIII

(Chapter 7) Fresh figs are very sensitive to physical damage, one of the main reasons for their short shelf-life.

Plate XIV

(Chapter 8) Miniature and large types of golden apple fruits.

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Plate XV (Chapter 8) (a) Mature green and ripe golden apple fruits without sooty mould on fruit skin; (b) mature green golden apple fruits with sooty mould covering extensive areas on fruit skin.

Plate XVI (Chapter 9) Berry bleaching symptoms produced by SO2. SO2 penetrates around the insertion of berry pedicel in (a) Thompson Seedless; (b) Red Globe berries. SO2 penetrates through cracks on berries in (c) Red Globe.

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Plate XVII (Chapter 9) (a) Internal browning of Thompson Seedless; (b) and (c) cold damage, berries exhibit light brown discoloration with stem browning; (d) abrasion damage.

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Plate XVIII

Plate XIX

(Chapter 10) Transverse section of a white-fleshed guava fruit.

(Chapter 10) Transverse section of a salmon to pink-fleshed guava fruit.

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Plate XX (Chapter 11) Development of flowers into fruits of the Myrciaria jabuticaba (Vell) Berg (jabuticaba ‘Sabará’). (a) external tree aspect; (b) production aspect; (c) Blossom; (d) 4 DAB; (e) 7 DAB; (f) 11 DAB; (g) 16 DAB; (h) 28 DAB; (i) 45 DAB; (j) 50 DAB; (k) 60 DAB; (l) internal tree aspect. Source: Durigan, 2009. © Woodhead Publishing Limited, 2011

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Plate XXI

Plate XXII

(Chapter 12) Hard and soft pulp varieties of jackfruit.

(Chapter 12) (a)–(d): Jackfruit being sold in the market of Mysore, India.

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Plate XXIII (Chapter 13) The different varieties of jujube: (a) Budaizao; (b) Fangyuanguiyizao; (c) Longzao; (d) Jinsixiaozao; (e) Yuanlingzao; (f) Mumzao; (g) Chahuzao; (h) Twinszao; (i) Junzao; (j) Dongzao.

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Plate XXIV (Chapter 14) Low temperature breakdown in ‘Hayward’ kiwifruit. (a) A continuous ring of tissue of granular appearance is present under the skin in the outer pericarp. Granular flecks deeper in the pericarp possibly indicate more extensive disordering with time. (b) A 1–2 mm wide zone of granular flecks just under the skin in the outer pericarp. The disordered tissue extends from the distal end of the fruit where it is most extensive and light brown in colour, towards the stem-end of the fruit where the flecks are sparse. (c) Water-soaked tissue in the inner pericarp and where the inner pericarp meets the outer pericarp, and water-soaked tissue with some granular tissue under the skin. A zone or ring of granular tissue is present in the outer pericarp. (d) Translucent or water-soaked tissue in the inner pericarp at the distal end of the fruit. A zone of translucent or watersoaked tissue forms a ring in the mid-region of the outer pericarp that is most extensive at the distal end of the fruit and reduces towards the equator. Granular flecks are also present throughout the outer pericarp.

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Plate XXV (Chapter 14) Impact (a and b) and compression (c) damage in ‘Hayward’ kiwifruit.

Plate XXVI

(Chapter 15) Litchi fruit (cv. McLean’s Red).

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Plate XXVII

(Chapter 15) Litchi fruit after sulphur dioxide fumigation.

Plate XXVIII (Chapter 16) Fruit tree of longan cv. ‘Shixia’ grown in Guangdong province, China.

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Plate XXIX (Chapter 16) Arils of longan cv. ‘Shixia’ grown in Guangdong province, China.

Plate XXX (Chapter 17) Loquat fruits (Eriobotrya japonica Lindl.) of different varieties: (a) ‘Jinwuxing’; (b) ‘Jiefangzhong’; (c) ‘Zaozhong 6’; (d) ‘Dahongpao’.

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Plate XXXI (Chapter 17) Different processed products of loquat fruit: (a) loquat juice; (b) loquat wine; (c) loquat jam; (d) loquat ointment; and (e) loquat tea.

Plate XXXII (Chapter 18) (a) Exterior of the lucuma fruit; (b) interior of the lucuma fruit; (c) Lucuma fruit showing physical injury; (d) Lucuma fruit and juice

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Plate XXXIII (Chapter 19) Mature Macadamia fruit morphology. (a) raceme of Macadamia fruit showing green pericarp. (b) Left to right: dehiscent fruit; seed (‘nut’), h, hilum; m, seed micropyle (white dot at bottom of seed); s, suture between hilum and micropyle. (c) Clockwise: seed in pericarp (‘husk’); pericarp interior with tannin coated endocarp; open testa (‘shell’) showing enamel layer on inner surface of testa, m, micropyle at enamel end; h, hilum at opposite end; embryo in position in testa with cotyledon apex extending towards micropyle (m).

Plate XXXIV (Chapter 19) Macadamia whole kernels with shoulder damage, visible as damaged areas near the apex of the kernel.

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Plate XXXV

(Chapter 20) (a) Mamey apple tree; (b)–(c) mamey apple fruit; (d) exterior and interior of mamey apple fruit.

Plate XXXVI

(Chapter 21) (a)–(c) Mamey sapote fruit.

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Plate XXXVII

Plate XXXVIII

(Chapter 21) Mamey sapote fruit sold in the street in Mexico.

(Chapter 22) External and internal colour changes during ripening of ‘Tommy Atkins’ mango fruit.

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Plate XXXIX (Chapter 22) Changes in external and internal colour during maturation and ripening of mango.

Plate XL

(Chapter 22) Mango packinghouse.

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Related titles: Postharvest biology and technology of tropical and subtropical fruits Volume 1 (ISBN 978-1-84569-733-4) While products such as bananas, pineapples and kiwi fruit have long been available to consumers in temperate zones, novel fruits such as litchi and longan are now also entering the market. Tropical and subtropical fruits are vulnerable to postharvest losses and may also be transported long distances for sale. Therefore technologies for quality maintenance postharvest and a thorough understanding of the underpinning biological mechanisms are essential. This authoritative four-volume collection considers the postharvest biology and technology of tropical and subtropical fruit. Volume 1 focuses on key issues of fruit physiology, quality, safety and handling relevant to all those in the tropical and subtropical fruits supply chain. Postharvest biology and technology of tropical and subtropical fruits Volume 2 (ISBN 978-1-84569-734-1) Chapters in Volume 2 of this important collection review factors affecting the quality of different tropical and subtropical fruits, concentrating on postharvest biology and technology. Important issues relevant to each specific product are discussed, such as postharvest physiology, preharvest factors affecting postharvest quality, quality maintenance postharvest, pests and diseases and value-added processed products, among other topics. Postharvest biology and technology of tropical and subtropical fruits Volume 3 (ISBN 978-1-84569-735-8) Chapters in Volume 3 of this important collection review factors affecting the quality of different tropical and subtropical fruits, concentrating on postharvest biology and technology. Important issues relevant to each specific product are discussed, such as postharvest physiology, preharvest factors affecting postharvest quality, quality maintenance postharvest, pests and diseases and value-added processed products, among other topics. Details of these books and a complete list of Woodhead’s titles can be obtained by: • visiting our web site at www.woodheadpublishing.com • contacting Customer Services (e-mail: [email protected]; fax: +44 (0) 1223 832819; tel.: +44 (0) 1223 499140 ext. 130; address: Woodhead Publishing Limited, 80 High Street, Sawston, Cambridge CB22 3HJ, UK

© Woodhead Publishing Limited, 2011

Woodhead Publishing Series in Food Science, Technology and Nutrition: Number 209

Postharvest biology and technology of tropical and subtropical fruits Volume 4: Mangosteen to white sapote

Edited by Elhadi M. Yahia

© Woodhead Publishing Limited, 2011

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Published by Woodhead Publishing Limited, 80 High Street, Sawston, Cambridge CB22 3HJ, UK www.woodheadpublishing.com Woodhead Publishing, 1518 Walnut Street, Suite 1100, Philadelphia, PA 19102-3406, USA Woodhead Publishing India Private Limited, G-2, Vardaan House, 7/28 Ansari Road, Daryaganj, New Delhi – 110002, India www.woodheadpublishingindia.com First published 2011, Woodhead Publishing Limited © Woodhead Publishing Limited, 2011. Chapter 15 was prepared by US government employees; this chapter is therefore in the public domain and cannot be copyrighted. The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials. Neither the authors nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Library of Congress Control Number: 2011929803 ISBN 978-0-85709-090-4 (print) ISBN 978-0-85709-261-8 (online) ISSN 2042-8049 Woodhead Publishing in Food Science, Technology and Nutrition (print) ISSN 2042-8057 Woodhead Publishing in Food Science, Technology and Nutrition (online) The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acid-free and elemental chlorine-free practices. Furthermore, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. Cover image: Fruit stand in Malaysia (Photo: Elhadi M. Yahia). Typeset by RefineCatch Limited, Bungay, Suffolk Printed by TJI Digital Limited, Padstow, Cornwall, UK

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Contents

Contributor contact details .......................................................................... Woodhead Publishing Series in Food Science, Technology and Nutrition ..... Foreword ......................................................................................................

xv xxiii xxxi

1 Mangosteen (Garcinia mangostana L.)............................................... S. Ketsa, Kasetsart University, Thailand and R. E. Paull, University of Hawaii at Manoa, USA 1.1 Introduction................................................................................. 1.2 Fruit development and postharvest physiology .......................... 1.3 Maturity and quality components ............................................... 1.4 Preharvest factors affecting fruit quality .................................... 1.5 Postharvest handling factors affecting quality ............................ 1.6 Physiological disorders ............................................................... 1.7 Pathological disorders ................................................................. 1.8 Harvesting practices.................................................................... 1.9 Postharvest operations ................................................................ 1.10 Processing ................................................................................... 1.11 Conclusions................................................................................. 1.12 Acknowledgements..................................................................... 1.13 References...................................................................................

1

2 Melon (Cucumis melo L.)..................................................................... M. E. Saltveit, University of California, Davis, USA 2.1 Introduction................................................................................. 2.2 Fruit development and postharvest physiology .......................... 2.3 Maturity and quality components and indices ............................ 2.4 Preharvest factors affecting fruit quality .................................... 2.5 Postharvest handling factors affecting fruit quality ....................

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Contents 2.6 2.7 2.8 2.9 2.10 2.11 2.12

Physiological disorders ............................................................... Pathological disorders ................................................................. Insect pests and their control ...................................................... Postharvest handling practices .................................................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

38 39 39 39 42 42 43

3 Nance (Byrsonima crassifolia (L.) Kunth).......................................... O. Duarte, National Agrarian University, La Molina, Peru 3.1 Introduction................................................................................. 3.2 Fruit development and postharvest physiology .......................... 3.3 Maturity and quality components and indices ............................ 3.4 Preharvest factors affecting quality ............................................ 3.5 Postharvest handling factors affecting quality ............................ 3.6 Physiological disorders ............................................................... 3.7 Pathological disorders ................................................................. 3.8 Insect pests and their control ...................................................... 3.9 Postharvest handling practices .................................................... 3.10 Processing ................................................................................... 3.11 Conclusion .................................................................................. 3.12 References...................................................................................

44 44 46 47 47 48 48 48 48 48 49 49 50

4 Noni (Morinda citrifolia L.) ................................................................. A. Carrillo-López, Autonomous University of Sinaloa, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico 4.1 Introduction................................................................................. 4.2 Fruit growth, development and maturation ................................ 4.3 Preharvest conditions and postharvest handling factors affecting quality .......................................................................... 4.4 Pathological disorders ................................................................. 4.5 Insect pests and their control ...................................................... 4.6 Postharvest handling practices .................................................... 4.7 Processing ................................................................................... 4.8 Conclusions................................................................................. 4.9 References...................................................................................

51

5 Olive (Olea europaea L.) ...................................................................... C. H. Crisosto and L. Ferguson, University of California, USA and G. Nanos, University of Thessaly, Greece 5.1 Introduction................................................................................. 5.2 Fruit development and postharvest physiology .......................... 5.3 Maturity and quality components and indices ............................ 5.4 Postharvest handling factors affecting quality ............................ 5.5 Physiological disorders ...............................................................

63

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Contents 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14

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Pathological disorders ................................................................. Insect pests and their control ...................................................... Harvest operations ...................................................................... Packinghouse handling practices ................................................ Grades and standards for processed olives ................................. Recommended storage and shipping conditions......................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

71 72 72 75 80 83 84 84 84

6 Papaya (Carica papaya L.)................................................................... S. P. Singh, Curtin University of Technology, Australia and D. V. Sudhakar Rao, Indian Institute of Horticultural Research, India 6.1 Introduction................................................................................. 6.2 Fruit development and postharvest physiology .......................... 6.3 Maturity indices .......................................................................... 6.4 Preharvest factors affecting fruit quality .................................... 6.5 Postharvest factors affecting fruit quality ................................... 6.6 Physiological disorders ............................................................... 6.7 Postharvest pathological disorders ............................................. 6.8 Postharvest insect pests and phytosanitary treatments ............... 6.9 Postharvest handling practices .................................................... 6.10 Processing ................................................................................... 6.11 Conclusions................................................................................. 6.12 References...................................................................................

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7 Passion fruit (Passiflora edulis Sim.) .................................................. W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain and G. Fischer, National University of Colombia, Colombia 7.1 Introduction................................................................................. 7.2 Preharvest factors affecting fruit quality .................................... 7.3 Postharvest physiology and quality ............................................ 7.4 Postharvest handling factors affecting quality ............................ 7.5 Crop losses .................................................................................. 7.6 Processing ................................................................................... 7.7 Conclusions................................................................................. 7.8 References................................................................................... 8 Pecan (Carya illinoiensis (Wangenh.) K. Koch.)................................ A. A. Gardea and M. A. Martínez-Téllez, Research Center for Food and Development, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico 8.1 Introduction.................................................................................

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Contents 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13

Nutritional value of pecan nuts ................................................... Harvesting, handling and storage ............................................... Current quality grading system ................................................... In-shell and shelled pecan ........................................................... Description of main quality attributes ........................................ Storage ........................................................................................ Postharvest physiology factors affecting nut quality .................. Potential improvements in handling ........................................... Processing ................................................................................... Conclusions................................................................................. Acknowledgements..................................................................... References...................................................................................

145 147 152 154 155 156 158 160 161 161 162 162

9 Persimmon (Diospyros kaki L.) ........................................................... A. B. Woolf, The New Zealand Institute for Plant & Food Research Limited, New Zealand and R. Ben-Arie, Israel Fruit Growers’ Association, Israel 9.1 Introduction................................................................................. 9.2 Fruit development and postharvest physiology .......................... 9.3 Maturity, quality at harvest and phytonutrients .......................... 9.4 Preharvest factors affecting postharvest fruit quality ................. 9.5 Postharvest handling factors affecting fruit quality .................... 9.6 Physiological disorders ............................................................... 9.7 Pathological disorders ................................................................. 9.8 Insect pests and their control ...................................................... 9.9 Postharvest handling practices .................................................... 9.10 Processing ................................................................................... 9.11 Conclusions................................................................................. 9.12 References...................................................................................

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10 Pineapple (Ananas comosus L. Merr.) ................................................ A. Hassan and Z. Othman, Malaysian Agricultural Research and Development Institute (MARDI), Malaysia and J. Siriphanich, Kasetsart University, Kamphang Saen, Thailand 10.1 Introduction................................................................................. 10.2 Fruit development and postharvest physiology .......................... 10.3 Physical and biochemical changes during maturation and ripening ................................................................................ 10.4 Preharvest factors affecting fruit quality .................................... 10.5 Postharvest factors affecting quality ........................................... 10.6 Physiological disorders ............................................................... 10.7 Pathological disorders ................................................................. 10.8 Insect pests and their control ...................................................... 10.9 Postharvest handling practices ....................................................

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Contents 10.10 10.11 10.12 10.13

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Processing ................................................................................... Conclusions................................................................................. Acknowledgements..................................................................... References...................................................................................

211 212 212 212

11 Pistachio (Pistacia vera L.) .................................................................. M. Kashaninejad, Gorgan University of Agricultural Sciences and Natural Resources, Iran and L. G. Tabil, University of Saskatchewan, Canada 11.1 Introduction................................................................................. 11.2 Physiological disorders ............................................................... 11.3 Postharvest pathology and mycotoxin contamination ................ 11.4 Postharvest handling practices .................................................... 11.5 Processing of fresh pistachio nuts............................................... 11.6 Processing of dried pistachio nuts .............................................. 11.7 References...................................................................................

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12 Pitahaya (pitaya) (Hylocereus spp.) .................................................... F. Le Bellec and F. Vaillant, Centre for Agricultural Research and Development (CIRAD), France 12.1 Introduction................................................................................. 12.2 Uses and market .......................................................................... 12.3 Botany, origin and morphology .................................................. 12.4 Cropping system ......................................................................... 12.5 Cultivation techniques ................................................................ 12.6 Pests and diseases ....................................................................... 12.7 Quality components and indices ................................................. 12.8 Postharvest handling factors affecting quality ............................ 12.9 Processing ................................................................................... 12.10 Conclusions................................................................................. 12.11 References...................................................................................

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13 Pitanga (Eugenia uniflora L.) .............................................................. M. Vizzotto and L. Cabral, Brazilian Agricultural Research Corporation (EMBRAPA), Brazil and A. Santos Lopes, Federal University of Pará, Brazil 13.1 Introduction................................................................................. 13.2 Postharvest physiology ............................................................... 13.3 Maturity and quality components and composition.................... 13.4 Postharvest handling factors affecting quality ............................ 13.5 Postharvest handling practices .................................................... 13.6 Processing ................................................................................... 13.7 Conclusions................................................................................. 13.8 References...................................................................................

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Contents

14 Pomegranate (Punica granatum L.).................................................... M. Erkan, Akdeniz University, Turkey and A. A. Kader, University of California, Davis, USA 14.1 Introduction................................................................................. 14.2 Fruit development and postharvest physiology .......................... 14.3 Maturity and quality components and indices ............................ 14.4 Preharvest factors affecting fruit quality .................................... 14.5 Postharvest handling factors affecting quality ............................ 14.6 Physiological disorders ............................................................... 14.7 Pathological disorders ................................................................. 14.8 Postharvest handling practices .................................................... 14.9 Processing ................................................................................... 14.10 Conclusions................................................................................. 14.11 References...................................................................................

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15 Rambutan (Nephelium lappaceum L.) ................................................ M. M. Wall, US Department of Agriculture, Agricultural Research Service (USDA-ARS), USA, D. Sivakumar, Tshwane University of Technology, South Africa and L. Korsten, University of Pretoria, South Africa 15.1 Introduction................................................................................. 15.2 Fruit development and postharvest physiology .......................... 15.3 Maturity and quality components and indices ............................ 15.4 Preharvest factors affecting fruit quality .................................... 15.5 Postharvest handling factors affecting quality ............................ 15.6 Physiological disorders ............................................................... 15.7 Pathological disorders ................................................................. 15.8 Insect pests and their control ...................................................... 15.9 Postharvest handling practices .................................................... 15.10 Processing ................................................................................... 15.11 Conclusions................................................................................. 15.12 References...................................................................................

312

16 Salak (Salacca zalacca (Gaertner) Voss) ............................................ S. Supapvanich, Kasetsart University, Thailand, R. Megia, Bogor Agricultural University, Indonesia and P. Ding, University of Putra Malaysia, Malaysia 16.1 Introduction................................................................................. 16.2 Fruit development and postharvest physiology .......................... 16.3 Changes in quality components during maturation .................... 16.4 Preharvest factors affecting fruit quality .................................... 16.5 Postharvest factors and physiological disorders affecting fruit quality ................................................................................. 16.6 Postharvest pathology and entomology ...................................... 16.7 Postharvest handling practices ....................................................

334

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Contents

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16.8 Processing ................................................................................... 16.9 Conclusions................................................................................. 16.10 References...................................................................................

347 348 348

17 Sapodilla (Manilkara achras (Mill) Fosb., syn Achras sapota, L.) ... E. M. Yahia and F. Guttierrez-Orozco, Autonomous University of Queretaro, Mexico 17.1 Introduction................................................................................. 17.2 Fruit development and postharvest physiology .......................... 17.3 Maturity and quality components and indices ............................ 17.4 Preharvest factors affecting fruit quality .................................... 17.5 Postharvest handling factors affecting quality ............................ 17.6 Physiological disorders ............................................................... 17.7 Pathological disorders ................................................................. 17.8 Insect pests and their control ...................................................... 17.9 Postharvest handling practices .................................................... 17.10 Processing ................................................................................... 17.11 Conclusions................................................................................. 17.12 References...................................................................................

351

18 Soursop (Annona muricata L.) ............................................................ M. A. Coêlho de Lima and R. E. Alves, Brazilian Agricultural Research Corporation (EMBRAPA), Brazil 18.1 Introduction................................................................................. 18.2 Fruit growth and ripening ........................................................... 18.3 Maturity and quality components and indices ............................ 18.4 Preharvest factors affecting fruit quality .................................... 18.5 Postharvest handling factors affecting quality ............................ 18.6 Physiological disorders ............................................................... 18.7 Pathological disorders ................................................................. 18.8 Postharvest handling practices .................................................... 18.9 Conclusions................................................................................. 18.10 References................................................................................... 19 Star apple (Chrysophyllum cainito L.) ................................................ E. M. Yahia and F. Guttierrez-Orozco, Autonomous University of Queretaro, Mexico 19.1 Introduction................................................................................. 19.2 Fruit development and postharvest physiology .......................... 19.3 Maturity and quality components and indices ............................ 19.4 Preharvest factors affecting fruit quality .................................... 19.5 Postharvest handling factors affecting quality ............................ 19.6 Physiological disorders ............................................................... 19.7 Pathological disorders ................................................................. 19.8 Insect pests and their control ......................................................

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Contents 19.9 19.10 19.11 19.12

Postharvest handling practices .................................................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

20 Sugar apple (Annona squamosa L.) and atemoya (A. cherimola Mill. × A. squamosa L.) ................................................ C. Wongs-Aree, King Mongkut’s University of Technology Thonburi (KMUTT), Thailand and S. Noichinda, King Mongkut’s University of Technology North Bangkok (KMUTNB), Thailand 20.1 Introduction................................................................................. 20.2 Fruit development and postharvest physiology .......................... 20.3 Maturity ...................................................................................... 20.4 Preharvest factors affecting fruit quality .................................... 20.5 Postharvest handling factors affecting quality ............................ 20.6 Physiological disorders ............................................................... 20.7 Diseases, insect pests and their control....................................... 20.8 Postharvest handling practices .................................................... 20.9 Processing ................................................................................... 20.10 Conclusions................................................................................. 20.11 Acknowledgements..................................................................... 20.12 References...................................................................................

397 397 397 398 399

399 405 408 410 411 412 414 415 421 422 422 423

21 Tamarillo (Solanum betaceum (Cav.)) ................................................ W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain, A. East, Massey University, New Zealand and A. Woolf, The New Zealand Institute for Plant & Food Research Limited, New Zealand 21.1 Introduction................................................................................. 21.2 Preharvest factors affecting fruit quality .................................... 21.3 Postharvest physiology and quality ............................................ 21.4 Postharvest handling factors affecting quality ............................ 21.5 Crop losses .................................................................................. 21.6 Processing ................................................................................... 21.7 Conclusions................................................................................. 21.8 References...................................................................................

427

22 Tamarind (Tamarindus indica L.) ....................................................... E. M. Yahia, Autonomous University of Queretaro, Mexico and N. K.-E. Salih, Agricultural Research Corporation, Sudan 22.1 Introduction................................................................................. 22.2 Fruit growth and ripening ........................................................... 22.3 Maturity and quality components and indices ............................ 22.4 Preharvest factors affecting fruit quality .................................... 22.5 Diseases and pests and their control ...........................................

442

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Contents 22.6 22.7 22.8 22.9 22.10

Postharvest handling factors affecting quality ............................ Postharvest handling practices .................................................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

23 Wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry) and related species .......................................................... Z.-H Shü, Meiho University, Taiwan, C.-C. Hsieh and H.-L. Lin, National Chung-hsing University, Taiwan 23.1 Introduction................................................................................. 23.2 Fruit development and postharvest physiology .......................... 23.3 Maturity, quality components and indices .................................. 23.4 Physiological disorders ............................................................... 23.5 Pathological disorders ................................................................. 23.6 Insect pests and their control ...................................................... 23.7 Postharvest handling practices .................................................... 23.8 Conclusions................................................................................. 23.9 References...................................................................................

xiii 451 452 453 455 455 458 458 464 464 464 467 467 469 470 470

24 White sapote (Casimiroa edulis Llave & Lex) ................................... E. M. Yahia and F. Guttierrez-Orozco, Autonomous University of Queretaro, Mexico 24.1 Introduction................................................................................. 24.2 Fruit development and postharvest physiology .......................... 24.3 Maturation and quality components and indices ........................ 24.4 Preharvest factors affecting fruit quality .................................... 24.5 Postharvest handling factors affecting quality ............................ 24.6 Physiological disorders ............................................................... 24.7 Pathological disorders ................................................................. 24.8 Insect pests and their control ...................................................... 24.9 Postharvest handling practices .................................................... 24.10 Processing ................................................................................... 24.11 Conclusions................................................................................. 24.12 References...................................................................................

474 477 477 478 478 478 479 479 479 480 480 480

Index.............................................................................................................

483

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Contributor contact details Chapter 3

(* = main contact) Chapter 1 S. Ketsa* Department of Horticulture Faculty of Agriculture Kasetsart University Bangkok, 10900 Thailand

O. Duarte Universidad Nacional Agraria – La Molina Monte Real 207, Dept. 7 Chacarilla, Surco Lima 33 Peru Email: [email protected]

Email: [email protected] R. E. Paull Department of Tropical Plant and Soil Sciences University of Hawaii at Manoa Honolulu, HI 96822 USA Email: [email protected] Chapter 2 M. E. Saltveit Mann Laboratory Department of Plant Sciences University of California Davis, CS 95616 USA

Chapter 4 A. Carrillo López* Maestría en Ciencia y Tecnología de Alimentos Facultad de Ciencias QuímicoBiológicas Universidad Autónoma de Sinaloa Blvd de las Américas s/n Culiacán Sinaloa, C. P. 80000 México Email: [email protected] [email protected]

Email: [email protected]

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Contributor contact details

E. M. Yahia Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida de las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México

D. V. Sudhakar Rao Division of Postharvest Technology Indian Institute of Horticultural Research Hessaraghatta Lake Bangalore, 560 089 India

Email: [email protected]

Email: [email protected]

Chapter 5

Chapter 7

C. H. Crisosto* and L. Ferguson Department of Plant Sciences University of California, Davis One Shields Avenue Davis, CA 95616 USA

W. C. Schotsmans* Department of Postharvest Science Institut de Recerca i Tecnologia Agroalimentàries Avenida de Alcalde Rovira Roure 191 25198 Lleida Spain

Email: [email protected] [email protected]

Email: [email protected]

G. Nanos School of Agricultural Sciences University of Thessaly Fitoko Str 38446 Volos Greece

G. Fischer Facultad de Agronomía Universidad Nacional de Colombia A. A. 14490, Av. Carr. 30 No. 45–03 Bogotá Colombia

Email: [email protected]

Email: [email protected]

Chapter 6

Chapter 8

S. P. Singh* Department of Environment and Agriculture Curtin University of Technology GPO Box U1987 Perth 6845 Australia

A. A. Gardea* Unidad Guaymas Centro de Investigación en Alimentación y Desarrollo, A.C. Carretera a Varadero Nacional km 6.6. Guaymas, Sonora, 85480 Mexico

Email: sukhvinder.pal.singh@gmail. com

Email: [email protected]

© Woodhead Publishing Limited, 2011

Contributor contact details M. A. Martínez-Téllez Centro de Investigación en Alimentación y Desarrollo, A.C. Carretera a la Victoria, km 0.6 Hermosillo, Sonora, 83000 México Email: [email protected] E. M. Yahia Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México Email: [email protected]

Chapter 10 A. Hassan* and Z. Othman Malaysian Agricultural Research and Development Institute (MARDI) GPO Box 12301 50774 Kuala Lumpur Malaysia Email: [email protected] J. Siriphanich Department of Horticulture Faculty of Agriculture Kamphaeng Saen Kasetsart University Nakhon Pathom, 73140 Thailand Email: [email protected]

Chapter 9

Chapter 11

A. B. Woolf* The New Zealand Institute for Plant and Food Research Mt Albert Private Bag 92169 Auckland Mail Centre 1142, Auckland New Zealand Email: [email protected] R. Ben-Arie Fruit Storage Research Laboratory Israel Fruit Growers’ Association Kiryat Shemona 10200, Israel Email: [email protected]

xvii

M. Kashaninejad* Department of Food Science and Technology Gorgan University of Agricultural Sciences and Natural Resources Beheshti Avenue Gorgan 49137-15739 Iran Email: [email protected] [email protected] L. G. Tabil Department of Chemical and Biological Engineering University of Saskatchewan 57 Campus Drive Saskatoon SK S7N 5A9 Canada Email: [email protected]

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Contributor contact details

Chapter 12 F. Le Bellec* CIRAD, UPR 103 HORTSYS TA B-103/PS4, Boulevard de la Lironde 34398 Montpellier Cedex 5 France Email: [email protected] F. Vaillant CIRAD, UMR 95 QUALISUD TA B-95/16, 73 rue Jean François Breton 34398 Montpellier Cedex 5 France Email: [email protected] Chapter 13

L. Cabral Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Food Technology Av. das Américas, 29501 Guaratiba, Rio de Janeiro CEP 23020-470 Brazil Email: [email protected] Chapter 14 M. Erkan* Department of Horticulture Faculty of Agriculture Akdeniz University 07059 Antalya Turkey Email: [email protected]

M. Vizzotto* Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Temperate Agricultural Rodovia BR 392, km 78 Pelotas RS – Brazil – CEP 96010-971 Email: marcia.vizzotto@cpact. embrapa.br

A. A. Kader Department of Plant Sciences University of California, Davis CA 95616 USA Email: [email protected] Chapter 15

A. S. Lopes Federal University of Pará (UFPA) College of Food Engineering Rua Augusto Corrêa 01, Guamá Belem, PA CEP 66075-110 Brazil

M. M. Wall* US Department of Agriculture Agricultural Research Service P.O. Box 4459 Hilo Hawaii 96720 USA

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Contributor contact details D. Sivakumar Department of Crop Sciences Tshwane University of Technology Pretoria 0001 South Africa Email: [email protected] L. Korsten Department of Microbiology and Plant Pathology University of Pretoria Pretoria 0002 South Africa Email: [email protected] Chapter 16 S. Supapvanich* Faculty of Natural Resources and Agro-Industry Chalermprakiat Sakonnakhon Province Campus Kasetsart University 59 Chiangkhrua, Muang Sakonnakhon Province 47000 Thailand Email: [email protected] R. Megia Department of Biology-FMIPA Bogor Agricultural University Darmaga Campus Bogor 16680 Indonesia Email: [email protected]

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P. Ding Department of Crop Science Faculty of Agriculture Universiti Putra Malaysia 43400 UPM Serdang, Selangor Malaysia Email: [email protected] Chapters 17, 19 and 24 E. M. Yahia* and F. Guttierrez-Orozco Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México Email: [email protected]; [email protected] Chapter 18 M. A. Coêlho de Lima* Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Tropical Semi-Arid BR 428 Km 152 P. O. Box 23 56302-970, Petrolina Pernambuco State Brazil Email: [email protected] R. E. Alves Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Tropical Agroindustry Dra Sara Mesquite Street, 2270 60511-110, Fortaleza Ceará State Brazil Email: [email protected]

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Chapter 20 C. Wongs-Aree* Postharvest Technology Program School of Bioresources and Technology King Mongkut’s University of Technology Thonburi (KMUTT) Bangkok 10140 Thailand

A. B. Woolf The New Zealand Institute for Plant and Food Research Limited Mt Albert Research Centre Private Bag 92169 Mt Albert New Zealand Email: allan.woolf@plantandfood. co.nz

Email: [email protected] S. Noichinda Faculty of Applied Science King Mongkut’s University of Technology North Bangkok (KMUTNB) Bangkok 10800 Thailand

Chapter 22 E. M. Yahia* Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México

Email: [email protected] Email: [email protected] Chapter 21 W. C. Schotsmans* Department of Postharvest Science Institut de Recerca I Tecnologia Agroalimentàries Avenida de Alcalde Rovira Roure 191 25198 Lleida Spain Email: [email protected]

N. K.-E. Salih Forestry Research Center Agricultural Research Corporation P. O. Box 7089 Khartoum Sudan Email: [email protected] Chapter 23

A. East Centre for Postharvest and Refrigeration Research Massey University Private Bag 11222 Palmerston North 4442 New Zealand

Z.-H. Shü* Research Institute of Health and Biotechnology and Department of Science and Technology Meiho University Neipu, Pingtung 912 Taiwan

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Contributor contact details C.-C. Hsieh Department of Horticulture National Chun-hsing University Taichung 400 Taiwan

H.-L. Lin Department of Horticulture National Chung-Hsing University Taichung 400 Taiwan

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134 Microbiological analysis of red meat, poultry and eggs Edited by G. Mead 135 Maximising the value of marine by-products Edited by F. Shahidi 136 Chemical migration and food contact materials Edited by K. Barnes, R. Sinclair and D. Watson 137 Understanding consumers of food products Edited by L. Frewer and H. van Trijp 138 Reducing salt in foods: practical strategies Edited by D. Kilcast and F. Angus 139 Modelling microorganisms in food Edited by S. Brul, S. Van Gerwen and M. Zwietering 140 Tamime and Robinson’s Yoghurt: science and technology Third edition A. Y. Tamime and R. K. Robinson 141 Handbook of waste management and co-product recovery in food processing Volume 1 Edited by K. W. Waldron 142 Improving the flavour of cheese Edited by B. Weimer 143 Novel food ingredients for weight control Edited by C. J. K. Henry 144 Consumer-led food product development Edited by H. MacFie 145 Functional dairy products Volume 2 Edited by M. Saarela 146 Modifying flavour in food Edited by A. J. Taylor and J. Hort 147 Cheese problems solved Edited by P. L. H. McSweeney 148 Handbook of organic food safety and quality Edited by J. Cooper, C. Leifert and U. Niggli 149 Understanding and controlling the microstructure of complex foods Edited by D. J. McClements 150 Novel enzyme technology for food applications Edited by R. Rastall 151 Food preservation by pulsed electric fields: from research to application Edited by H. L. M. Lelieveld and S. W. H. de Haan 152 Technology of functional cereal products Edited by B. R. Hamaker 153 Case studies in food product development Edited by M. Earle and R. Earle 154 Delivery and controlled release of bioactives in foods and nutraceuticals Edited by N. Garti 155 Fruit and vegetable flavour: recent advances and future prospects Edited by B. Brückner and S. G. Wyllie 156 Food fortification and supplementation: technological, safety and regulatory aspects Edited by P. Berry Ottaway 157 Improving the health-promoting properties of fruit and vegetable products Edited by F. A. Tomás-Barberán and M. I. Gil 158 Improving seafood products for the consumer Edited by T. Børresen 159 In-pack processed foods: improving quality Edited by P. Richardson 160 Handbook of water and energy management in food processing Edited by J. Klemeš, R. Smith and J-K Kim 161 Environmentally compatible food packaging Edited by E. Chiellini 162 Improving farmed fish quality and safety Edited by Ø. Lie 163 Carbohydrate-active enzymes Edited by K-H Park 164 Chilled foods: a comprehensive guide Third edition Edited by M. Brown 165 Food for the ageing population Edited by M. M. Raats, C. P. G. M. de Groot and W. A Van Staveren 166 Improving the sensory and nutritional quality of fresh meat Edited by J. P. Kerry and D. A. Ledward 167 Shellfish safety and quality Edited by S. E. Shumway and G. E. Rodrick 168 Functional and speciality beverage technology Edited by P. Paquin

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198 Freeze-drying of pharmaceutical and food products T-C Hua, B-L Liu and H Zhang 199 Oxidation in foods and beverages and antioxidant applications Volume 1: understanding mechanisms of oxidation and antioxidant activity Edited by E. A. Decker, R. J. Elias and D. J. McClements 200 Oxidation in foods and beverages and antioxidant applications Volume 2: management in different industry sectors Edited by E. A. Decker, R. J. Elias and D. J. McClements 201 Protective cultures, antimicrobial metabolites and bacteriophages for food and beverage biopreservation Edited by C. Lacroix 202 Separation, extraction and concentration processes in the food, beverage and nutraceutical industries Edited by S. S. H. Rizvi 203 Determining mycotoxins and mycotoxigenic fungi in food and feed Edited by S. De Saeger 204 Developing children’s food products Edited by D. Kilcast and F. Angus 205 Functional foods: concept to product Second edition Edited by M. Saarela 206 Postharvest biology and technology of tropical and subtropical fruits Volume 1 Edited by E. M. Yahia 207 Postharvest biology and technology of tropical and subtropical fruits Volume 2 Edited by E. M. Yahia 208 Postharvest biology and technology of tropical and subtropical fruits Volume 3 Edited by E. M. Yahia 209 Postharvest biology and technology of tropical and subtropical fruits Volume 4 Edited by E. M. Yahia 210 Food and beverage stability and shelf life Edited by D. Kilcast and P. Subramaniam 211 Processed Meats: improving safety, nutrition and quality Edited by J. P. Kerry and J. F. Kerry 212 Food chain integrity: a holistic approach to food traceability, safety, quality and authenticity Edited by J. Hoorfar, K. Jordan, F. Butler and R. Prugger 213 Improving the safety and quality of eggs and egg products Volume 1 Edited by Y. Nys, M. Bain and F. Van Immerseel 214 Improving the safety and quality of eggs and egg products Volume 2 Edited by F. Van Immerseel, Y. Nys and M. Bain 215 Feed and fodder contamination: effects on livestock and food safety Edited by J. Fink-Gremmels 216 Hygienic design of food factories Edited by J. Holah and H. L. M. Lelieveld 217 Technology of biscuits, crackers and cookies Fourth edition Edited by D. Manley 218 Nanotechnology in the food, beverage and nutraceutical industries Edited by Q. Huang 219 Rice quality K. R. Bhattacharya 220 Meat, poultry and seafood packaging Edited by J. P. Kerry 221 Reducing saturated fats in foods Edited by G. Talbot 222 Handbook of food proteins Edited by G. O. Phillips and P. A. Williams 223 Lifetime nutritional influences on cognition, behaviour and psychiatric illness Edited by D. Benton

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Foreword

Most published postharvest research on fruit, covering decades of activity, has concentrated on temperate or model crops. There are good reasons for this, mainly associated with the well-established production and marketing industries, and long-established research teams in Europe, North America and Australasia. This great effort has given us much of our current understanding of fruit ripening, the characterisation of ethylene as a growth regulator, far reaching fundamental knowledge on core issues in plant science such as respiration, cell wall metabolism, aroma volatiles, and more latterly, on genetic and molecular control of fruit properties. This work has particularly provided the technology which has allowed a remarkable level of control of fruit quality after harvest, and provided the mainstay for substantial economic gains at the levels of both industry and national economies. However, estimates of world fruit production (2005–07) show that tropical crops including citrus make up to about 60% of world major fruit crop production (World Kiwifruit Review, 2010). In conjunction with this, the volume of global exports of tropical and subtropical fruit is about twice that of temperate fruit crops (data for 2007, for instance, show about 19 million tonnes for temperate and 38 million tonnes for tropical/subtropical produce; FAOSTATS database). Such crops comprise a major part of the economies of tropical and subtropical countries, and some such as bananas, plantains and breadfruit, are staple foods with critical dietary components. While the scale and importance of this in itself would warrant an extensive research base, one of the most compelling issues for postharvest researchers is the level of food waste. Various analyses of wastage along the value chain have been made, but the consensus seems to be that in developing countries, where most of the tropical and subtropical crops are grown, food losses can amount to up to 50% or more. A breakdown of this (Kader, 2005; World Economic Forum, 2009) suggests that most waste occurs between harvest and retail, with low percentages of food loss at the consumer end of the chain.

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Foreword

This provides an immediate target for postharvest research, and there is some urgency on this, given current concerns over food security in the next few decades (Nature, 2010). There will be collateral benefits. The most important may well be in increasing export potential of crops that traditionally have short storage lives and that are easily damaged during transport and handling. Even increasing access to near markets will provide economic gain, but there is greater potential in targeting more affluent markets and consumers who are seeking a wider range of fruit types and eating experiences, and are prepared to pay more for them. There are other advantages. Optimised postharvest procedures will result in greater maintenance of the nutritive and calorific value of fruit crops by minimising physiological deterioration and that from pests and diseases. And now that sustainability has become a serious market issue, there are environmental impacts from reducing food loss. For instance, there have been estimates that water losses associated with food wastage could reach a level where up to half the original water supply from irrigation is lost (World Economic Forum, 2009). So how will postharvest research on tropical and subtropical fruit crops help? We have to know our commodities, and the contents of this book directly addresses this. Understanding the fruit crop, fruit development, when to harvest, the specific ripening process, and postharvest response, is critical to optimising postharvest storage and handling. We tend, however, to try to impose traditional postharvest practices on all crops, often when this is not appropriate. Low temperature storage is an obvious case, and tropical crops particularly are chillingly sensitive: there is a constant struggle to prolong storage life through temperature control with a recalcitrant commodity. Many improvements in quality control through the supply chain can be made for a lot of crops with very simple application of basic postharvest handling and storage practices. These target pest and diseases, disinfestation issues, and ways of reducing the rate of fruit ripening while increasing tolerance to storage and transport conditions. However, we can be more innovative. In most cases, there has been relatively little done in breeding and selection of tropical and subtropical fruit crops with postharvest quality attributes as targets. There is a lot of scope here, particularly in the new genomics era, where faster and smarter breeding can be undertaken, and more value extracted from existing genetic material. There is quite a lot of research currently underway on tackling tropical fruit problems through fresh cut technology, and the use of edible coatings and biofilms, to prolong storage and shelf life. While this may have a minor impact on local use and in decreasing food wastage in less urban environments and markets, there may be larger benefits for urban and export markets. There is also an approach that might require extra thought and greater interrogation of the properties of the particular crops. Instead of imposing highly technical storage conditions, understanding how the fruit responds to ambient conditions and then seeing if there are innovative ways of handling the crop under those conditions might be more economical and practical under less sophisticated systems. The history of postharvest suggests that local innovation has often been

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very effective and perhaps we have been persuaded to look at modern technology at the expense of more original thinking. We need robust knowledge of our crops, and then very targeted postharvest approaches to reducing waste and ensuring high market quality. This is not a choice, but is an imperative for local economies, and for future food security. Ian Ferguson The New Zealand Institute for Plant & Food Research

References FAOSTATS database. Kader A A (2005) Increasing food availability by reducing postharvest losses of fresh produce. Acta Hortic, 682, 2169–2175. (2010) The growing problem. Nature, 466, 456–561. World Economic Forum (2009) Driving sustainable consumption. Value chain waste: Overview briefing. World Kiwifruit Review (World Kiwifruit Review).

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1 Mangosteen (Garcinia mangostana L.) S. Ketsa, Kasetsart University, Thailand and R. E. Paull, University of Hawaii at Manoa, USA

Abstract: Mangosteen (Garcinia mangostana L.) is one of the most admired tropical fruit and known widely as the Queen of Fruits for its beautiful purple blue pericarp and delicious flavor. The edible aril is white, soft and juicy with sweet pleasant taste. Mangosteen is a climacteric fruit that undergoes rapid postharvest changes resulting in a short shelf life at ambient temperature. Physiological disorders induced by preharvest and postharvest factors have a major impact on the appearance and eating quality. In addition to fresh consumption, the aril is processed into other products. The fruit pericarp also contains many chemical compounds that have possible medicinal value. Key words: mangosteen, postharvest change, physiological disorder, postharvest handling quality.

1.1

Introduction

1.1.1 Origin, botany, morphology and structure The mangosteen (Garcinia mangostana L.) originated in Southeast Asia and is a member of the family Clusiaceae. In earlier works, the genus had been placed in the Guttiferae. The genus name Garcinia was given by Linnaeus in honor of French naturalist Laurent Garcin for his work as a botanist in the eighteenth century. Laurent Garcin with others had made one of the most detailed descriptions of the fruit. Although the word ‘mango’ occurs in the word ‘mangosteen’ there is no botanical relationship at the genus or family levels. The name mangosteen is thought to have been derived from Malay or Javanese. According to Verheij (1991: 443): The mangosteen as a fresh fruit is in great demand in its native range and is savored by all who find its subtle flavors a refreshing balance of sweet and sour. It should be pointed out that Asians consider many foods to be either ‘cooling’ such as the mangosteen or ‘heating’ such as the durian depending on whether they possess

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Postharvest biology and technology of tropical and subtropical fruits elements that reflect yin and yang. This duality is commonly used to help describe balance in many aspects of life in general and food in particular throughout Asia.

Morton (1987: 505) describes the mangosteen as follows: The mangosteen is a very slow-growing, erect tree with a pyramidal crown. The tree can attain 6 to 25 m (20 to 82 ft) and has dark-brown or nearly black, flaking bark, the inner bark containing much yellow, gummy, bitter latex. This evergreen has opposite, short-stalked leaves that are ovate-oblong or elliptic, leathery and thick, dark-green, slightly glossy above and yellowish-green and dull beneath. New leaves have a rosy hue. The mature leaves are 9 to 25 cm long (3 1/2 to 10 in) and 4.5 to 10 cm wide (1 3/4 to 4 in) with conspicuous, pale midribs. Female flowers are 4 to 5 cm wide (1 1/2 to 2 in). The flowers are borne singly or in pairs at the tips of young branchlets; their fleshy petals may be yellowish-green, edged with red or mostly red, and the petals are quickly shed.

No male flowers or trees have been described, though it is said to be dioecious. Mangosteen is only known as a female cultivated plant. Based on morphological characters, mangosteen may be a sterile allopolyploid hybrid (2n = 88 − 90) between two Garcinia spp. Morton (1987: 505) further describes that: the smooth round fruit, 3.4 to 7.5 cm in diameter (1 1/3 to 3 in), is capped by a prominent calyx at the stem end that has 4 to 8 triangular, flat remnants of the stigma in a rosette at the apex. When the fruit is mature and ripe, it is dark-purple to reddishpurple. The rind (pericarp) is 6 to 10 mm thick (1/4 to 3/8 in) and spongy and in cross-section is red outside and purplish-white on the inside. The pericarp has a bitter yellow latex, and a purple, staining juice. Inside the pericarp are 4 to 8 triangular segments of snow-white, juicy, soft edible flesh (aril) that clings to the seeds. The fruit may be seedless or have 1 to 5 fully developed seeds. The seeds are ovoid-oblong, somewhat flattened, 2.5 cm (1 in) long and 1.6 cm wide (5/8 in).

The edible aril is white, juicy, sweet and slightly-acid, with a pleasant flavor (Fu et al., 2007; Ji et al., 2007). It is similar in shape and size to a tangerine. The circle of wedge-shaped arils contains 4 to 8 segments, the larger of which contain the apomictic seeds that are unpalatable unless roasted. Fruit are harvested at various stages of ripeness, referred to as Stage 1 to Stage 6. During ripening, Hue angle and pericarp firmness decline significantly, while soluble solids contents (SSC) increases and titratable acidity (TA) decreases resulting in an increase of SSC : TA ratio, and better tasting fruit. Fruit harvested at Stage 1 and allowed to ripen to Stage 6 show no significant differences in sensory quality and fruit appearance to fruit harvested at Stage 6. In the absence of fertilization, asexual ovary nucellus tissue development occurs that ensures fruit and aril growth. The asexual embryos develop from the nucellus tissue and these apomixic ‘seed’ are used in propagation. The ‘seed’ is a clone of the mother plant with little variation (Richards, 1990; Ramage et al., 2004), but the absence of true seed associated with sexual fertilization limits varietal development and selection. DNA and RNA marker analysis from material sourced globally has shown variation among the different mangosteen populations.

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The majority of the samples had essentially the same genetic make-up (genotype) but significant differences were found in same samples (Yapwattanaphun and Subhadrabandhu, 2004). This difference could be due to chance mutation or selection within the limited variation that is known to occur. 1.1.2 Worldwide importance Mangosteen fruit is now grown worldwide and is being exported and marketed in more developed countries. Often it is advertised and marketed as a novel functional food and is sometimes called a ‘super fruit’. It is presumed to have a combination of

• • • •

appealing characteristics, such as taste, fragrance and visual qualities, nutrient richness, antioxidant strength, and potential impact for lowering risk of human diseases (Gross and Crown, 2007).

1.1.3 Nutritional value and health benefits The aril, though having a pleasant taste and flavor, has a low nutrient content (Table 1.1). Recent research on antioxidant determination showed that plant foods with rich colors had high scores of oxygen radical absorbance capacity (ORAC) whereas those that were white (without pigments) had low ORAC (Wu et al., 2004). Following this simple and subjective index, the white mangosteen aril Table 1.1 Nutritional values of mangosteen fruit (per 100 g edible portion). Content

per 100 g edible portion

Water Energy Protein Fat Carbohydrate Dietary fiber Ash Calcium Phosphorus Iron Copper Zinc B1 (Tiamine) B2 (Riboflavin) Niacin Vitamin C

80.9 g 76.0 cal 0.5 g 0.2 g 18.4 g 1.7 g 0.2 g 9.0 mg 14.0 mg 0.5 mg 0.11 mg 0.1 mg 0.09 mg 0.06 mg 0.1 mg 2.0 mg

Source: Anon. (2004). Fruits in Thailand. Department of Agricultural Extension, Ministry of Agriculture and Cooperatives, Bangkok, Thailand.

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should have a low ORAC, though no ORAC results have been reported for the aril to date. Some mangosteen juice products contain whole fruit purée or polyphenols extracted from the inedible pericarp (rind) as a formulation strategy to add phytochemical value. The resulting juice has a purple color and astringency derived from pericarp pigments. Xanthone extracts taken from the pericarp (Jung et al., 2006) and added to a juice could be beneficial (Anon, 2007). Apha-mangostin, a xanthone, can stimulate apoptosis in leukemia cells in vitro (Matsumoto et al., 2004). The preliminary nature of this research means that no definite conclusions can be drawn about possible health benefits for humans eating mangosteen.

1.2

Fruit development and postharvest physiology

1.2.1 Fruit growth, development and maturation At fruit set, fruit shape is almost spherical, with fruit length and width being almost equal and remaining so throughout the fruit growth (Fig. 1.1). Width and length increase slowly during the first two weeks after flowering then increase rapidly up to week 5 and more slowly thereafter. Fresh weight showed a similar pattern of growth, slow during the first two weeks and rapidly increasing. Aril fresh weight increased steadily from week 2 until the end of week 12 when it was 29% of the whole fruit (Wanichkul and Kosiyachinda, 1979a). Surprisingly, pericarp thickness

Fig. 1.1 Changes in length (●), width ({), fresh weight (∆), pericarp thickness (▲) and soluble solids (■) content in aril (…) of mangosteen fruit during growth and development (Wanichkul and Kosiyachinda, 1979a).

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changed only slightly between weeks 2 and 12. The data also suggested that growth was mainly expansion rather than cell division after week 2. Mangosteen fruit take about 12 weeks from fruit set to maturity that can vary about one week (Wanichkul and Kosiyachinda, 1979b). This small variation in maturation time is not commercially significant as growers can harvest fruit at a range of maturities. Fruit can be harvested as early as Stage 1 when fruit are light greenish-yellow with 5–10% scattered pink spots that ripen to acceptable eating quality at room temperature. The earlier Stage 0, when the fruit are yellowish-white or yellowish-white with light-green, are also considered mature though the aril eating quality is inferior to fruit harvested at Stage 1 and later (Palapol et al., 2009a). 1.2.2 Respiration, ethylene production and ripening Ripening fruit exhibits a respiratory climacteric pattern (Noichinda, 1992; Piriyavinit, 2008). The respiratory rate of fruit harvested at Stage 0 and ripened at 25 °C is about 10 ml/kg-h rising to about 30 ml/kg-h at the climacteric peak on day 4 and then falls to about 18 ml/kg-ml on day 7 (Fig. 1.2). Stage 0 fruit treated with exogenous ethylene treatment have an earlier climacteric respiratory rise. The higher the concentration of ethylene applied, the sooner the climacteric respiration occurs. The respiratory peak of Stage 0 fruit occurs on day 4 and when treated with 1, 10 and 100 uL/L ethylene on days 2.6, 2 and 1.5 with respiration rate at 26, 30, 31 and 32.5 ml/kg-h, respectively. Mechanical impact also increases the respiration rate of the fruit, the greater the impact the greater respiratory rate increases (Noichinda, 1992).

Fig. 1.2

Respiration (∆), ethylene production (…) and internal concentrations of ethylene (●) in mangosteen fruit harvested at Stage 0 (Noichinda, 1992).

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Ethylene production during ripening is delayed compared to the rise in respiration (Fig. 1.2). The rise in ethylene begins to increase after day 4 with the peak occurring after the respiratory peak on day 6.5, and then declines. The initial rate of ethylene production on day 1 for Stage 0 fruit is about 2 ul/kg-h and at the maximum about 14 ul/kg-h. The internal ethylene concentration at Stage 0 on day 1 is about 0.75 ppm, increasing to 2.5 ppm on day 2.5 and rapidly increases to a maximum of about 19 ppm by day 6 (Noichinda, 1992). The increase in ethylene production by whole fruit and the aril parallels a similar increase in 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity by the fruit aril. The aril ACO activity largely explains the ethylene production data, while possible additional 1-aminocyclopropane-1-carboxylic acid synthase (ACS) activity occurs in the pericarp. Fruit stored at 15 °C showed an ethylene production peak on day 1, which is a few days earlier than the maximum found in fruit stored at 25 °C. The rapid appearance of the ethylene peak in fruit stored at 15 °C is likely associated with chilling injury. As the storage duration at 15 °C increases, the changes in ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) levels, and the activities of ACS and ACO occur later than in fruit held at 25 °C. The pericarp of fruit stored at 15 °C and treated with 1-MCP have reduced activity of both ACS and ACO (Piriyavinit, 2008). Pericarp color change is coincident with the changes in respiration and ethylene production (Noichinda, 1992). The climacteric rise starts on day 2 as the fruit turns from to a light-greenish yellow with 51–100% scattered pink spots (Stage 2) (see Plate I in the colour section between pages 238 and 239). Pericarp color develops rapidly from Stage 2 to Stage 3 (reddish-pink), 4 (red to reddish-purple), 5 (dark purple) and 6 (purple black) within five or six days, depending on temperature. Fruit firmness also sharply decreases when fruit turns reddish-pink on day 3. The TSS: TA ratio and eating quality of fruit ripened to Stage 3 are not significantly different from fruit ripened to Stages 5 and 6. Consumers prefer to eat fruit ripened to Stage 5 or 6 as the fruit pericarp of Stage 4 fruit is still firm and is difficult to remove by hand (Palapol et al., 2009a). 1.2.3 Color development The pericarp color development occurs both on and off the tree. Tongdee and Suwanagul (1989) developed a skin color index scale for mangosteen maturity that is divided into 6 Stages (see Plate I in the colour section). Stage 0 fruit are yellowish white or yellowish white with light green, changing to light greenishyellow with 5–50% scattered pink spots at Stage 1. When the fruit are light greenish-yellow with 51–100% scattered pink spots is Stage 2, to when the spots are not as distinct as in Stage 2 or reddish-pink is Stage 3. Later stages are when red to reddish-purple (Stage 4), dark purple (Stage 5) and purple-black (Stage 6). Fruit harvested at Stage 0 develop skin color the same as fruit ripened on tree at Stage 6. Fruit when harvested at Stage 1, 2, 3, 4 and 5 reach Stage 6 in 6, 5, 4, 3, 2 and 1 days at 25 °C, respectively (Palapol et al., 2009a). Ratanamarno (1998) reported that mangosteen fruit at Stage 1 when stored at low temperatures (15 °C)

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changed to Stage 6 later than fruit stored at 35 °C and fruit stored at room temperature (30 °C). After transferring fruit stored at 15 °C to 25 °C, the red coloration (Hue value) and anthocyanin content increased rapidly and the increase correlated closely with an increase in ethylene production (Palapol et al., 2009a). Color development in mangosteen pericarp is closely correlated with the increase total anthocyanins (Fig. 1.3). The rapid increase in anthocyanin suggests that the precursors are readily available for conversion to cyanidins. No other pigments appear to contribute to skin color.

Fig. 1.3 (a) Cross section of mangosteen pericarp showing outer pericarp (OP) and inner pericarp (IP). The bar denotes 2 mm. (b) Hue values (▲) of skin color and total anthocyanin contents of inner (■) and outer (…) mangosteen pericarp during color development from light greenish yellow with 5% scattered pink spots to purple black (Stages 1–6) (Palapol et al., 2009a).

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The increase in total anthocyanin contents of the inner pericarp tissue follows the same trend as the outer pericarp though with a lower Hue value and total anthocyanin content. Hue value is a good objective measure of fruit maturity (Palapol et al., 2009a). The anthocyanins in the outer pericarp have been separated and identified by HPLC/MS. The five compounds reported are cyanidin-sophoroside, cyanidinglucoside, cyanidin-glucoside-pentoside, cyanidin-glucoside-X, cyanidin-X2 and cyanidin-X, where X denotes an unidentified residue of m/z 190. The 190 mass does not correspond to any common sugar residue. Cyanidin-3-sophoroside and cyanidin-3-glucoside are the major compounds and the only ones that increased with fruit color development (Fig. 1.4). The anthocyanin biosynthesis pathway has several key steps. The mangosteen anthocyanin biosynthesis genes GmPAL to G23mUFGT have been completely characterized (Palapol et al., 2009b). GmPAL to G23mUFGT all belong to multigene families and show sequence similarity to anthocyanin related genes in many other plants including several fruit. The transcript levels of the three mangosteen MYBs, GmMYB1, GmMYB7 and GmMYB10, increased markedly with onset of red coloration both on-tree and after harvest (Fig. 1.5). GmMYB10 is the most

Fig. 1.4 Anthocyanin profiles in outer pericarp of mangosteen fruit harvested at Stage 1 to 6 (light greenish yellow with 5% scattered pink spots to purple black) during color development. Peak identity was as follows: (1) cyaniding-sophoroside, (2) cyanidingglucosider-pentoside, (3) cyanidin-glucoside and cyanin-glucoside-X (overlapping peak), (4) cyaniding-X2, and (5) cyaniding-X. X denotes a residue of m/z 190 which has not been identified (Palapol et al., 2009a).

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Fig. 1.5 Transient activation of the mangosteen and Arabidopsis DFR promoter by GmMYBs, AtPAPl, and AtbHLH2 transcription factors. All TFs were co-infiltrated with DFR-Luc promoter in transient tobacco transformation assays. The dual luciferase (LUC) to 35S Renilla (REN), where an increase in activity equates to an increase in LUC relative to REN (Hellens et al., 2005). Error bars are the means ± SE for four replicate reactions (Palapol et al., 2009a).

up-regulated of the GmMYB transcription factors (299-fold on the tree and 501-fold postharvest fruit at Stage 5 – (dark purple)) and declines at Stage 6 (black purple) (Fig. 1.5). This expression pattern is similar to that of MdMYB10 in apple (Espley et al., 2007) and VvMYBPA1 in grape berry skins (Bogs et al., 2007). The expression patterns suggest that GmMYB10 is a potential candidate to regulate anthocyanin biosynthesis in mangosteen fruit. The expression pattern of all anthocyanin biosynthesis genes correlated with that of GmMYB10, in expression changes and with onset of color development, and declines in synthesis at the final stages. Mangosteen fruit color changes correlate well with ethylene production. Treatment with the ethylene receptor inhibitor 1-MCP delays the increase in Hue value (red), ethylene production and anthocyanin accumulation. In both 1-MCP and ethylene plus1-MCP treatments, 1-MCP down-regulates the expression of GmMYB genes, especially GmMYB10, and the anthocyanin biosynthetic genes. This correlative data gives strong support to the conclusion that ethylene and the expression of the GmMYB10 transcription factors closely control anthocyanin biosynthesis in mangosteen (Palapol et al., 2009b). Direct data is needed to show that ethylene directly regulates GmMYB10 and all anthocyanin biosynthesis genes at the transcription level. Though 1-MCP delays ethylene production, exogenous ethylene does not induce ethylene and anthocyanin production (Piriyavinit, 2008; Palapol et al., 2009b).

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Ethylene application also does not increase the expression anthocyanin biosynthetic and MYB transcription genes (Palapol et al., 2009b). Mangosteen fruit stored at 15 °C developed fruit color more slowly than the fruit stored at 25 °C (Palapol, 2009a). Storage of fruit at 15 °C, besides having delayed color development and ethylene production, inhibits the transcript levels of all anthocyanin biosynthetic genes that increased in abundance when transferred to 25 °C (Palapol et al., 2009b). Maybe the failure to see an ethylene response is because ethylene sensitivity is changing (increasing) during ripening. 1.2.4 Softening Pericarp firmness declines sharply from Stage 1 at 779.3 to 46.5 N at Stage 6 (Palapol et al., 2009a). The softening of the pericarp and also the aril parallels fruit ripening. As ripening starts, the fruit pericarp changes from uniform green to the development of red spots while the aril remains firm and connected to the pericarp. As the fruit ripens further to the pericarp having dark purple at an overripe stage, the aril becomes soft and juicy, and easily separates from the pericarp. Aril firmness declines slowly at room temperature between day 0 and day 4, and then shows a sharp change from day 4 to day 10 as the fruit develop full pericarp purple color. At 13 °C, aril firmness changes little over the 10 days of ripening. The water soluble pectin content in aril increased more rapidly at room temperature than when held at 13 °C. Aril insoluble pectin content declines during ripening with a sharp change between day 4 and day 8, while both pectin methylesterase and polygalacturonase activities increase more rapidly when held at room temperature than at 13 °C. This data suggest that changes in cell wall solubilization may be responsible for aril softening during ripening (Noichinda et al., 2007). The difference in firmness of mangosteen aril held at different temperatures reflects a correlation between water soluble pectin and activities of pectin methylesterase and polygalacturonase. However, high pectin methylesterase activity is detected at harvest (day 0) while polygalacturonase activity increases after harvest when held at both temperatures (Noichinda et al., 2007). This result suggests that pectin methylesterase (PME) may not have access to pectin during early fruit ripening and polygaloturonase (PG) does not increase until later when cell wall changes allow esterase activity and provision for de-esterified substrate for PG.

1.3

Maturity and quality components

Fruit color is the major criterion used to judge maturity and for grading of mangosteen fruit. The fruit are usually harvested at different stages according to color, from light greenish-yellow with scattered pink spots to dark purple. After harvest, the purple color continues to develop very quickly. For high fruit quality, the minimum harvest color stage is that of a fruit with distinct irregular, pink-red spots over the whole pericarp surface. If fruit are harvested with a light greenishyellow with scattered pink spots, the fruit do not ripen to full flavor (Tongdee and Suwanagul, 1989; Paull and Ketsa, 2004).

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Table 1.2 Time, quality and sensory evaluation of mangosteen fruit harvested at Stage 1 (A) and allowed to ripen at 25 °C, or harvested at the six different maturity stages and measurements made when the fruit reached Stage 6 (B). Fruit Time Firmness (N) a*/b* ratio stage (d) A B A B

% SSC A

B

A

B

A

B

B

1 2 3 4 5 6

15.2c 15.3bc 16.3ab 16.6a 17.1a 17.2a

17.2 17.3 17.5 17.9 17.5 17.4

0.77bc 0.78b 0.84a 0.80ab 0.79b 0.73c

0.81 0.81 0.80 0.78 0.75 0.74

19.8bc 19.6bc 19.3c 20.8bc 21.7ab 23.7a

21.2b 21.3b 21.9ab 23.0ab 23.5a 23.7a

4.2 3.7 3.8 4.0 3.7 4.1

0 1 2 3 5 9

6.66a 5.30b 4.91c 4.59d 4.20e 3.84f

44.8 0.03b 43.6 0.44b 46.0 1.16b 42.9 2.28b 45.0 3.71b 47.9 16.69a

11.06b 12.09ab 12.10ab 10.04b 9.63b 13.95a

% TA

SSC/TA

Sensory

Source: Palapol et al. (2009a). Notes: The firmness values in column A are log (In) transformed data, with original data from Stage 1 to 6, being 779.3, 201.3, 136.0, 98.4, 66.5 and 46.5 N, respectively. Means within any column followed by the same letter are not significantly different (P > 0.05).

Postharvest fruit quality is generally dependent on the stage of maturity at harvest. Fruit harvested at Stages 1 to 6 and allowed to ripen to Stage 6 showed no significant differences in fruit quality or sensory characteristics (Table 1.2). This suggests that ripening had already initiated before harvest of Stage 1 fruit but not Stage 0. This ripening habit provides considerable harvest flexibility allowing the Thai grower to harvest fruit for export at Stage 1 (light greenish yellow with 5% scattered pink spots) that develop full flavor and have a slightly longer shelf-life over fruit harvested at later stages. The Malaysian harvest guideline for mangosteen export is similar to Thailand, being reddish-yellow with patches of red (Osman and Milan, 2006).

1.4

Preharvest factors affecting fruit quality

Like other fruit crops, fruit quality depends on many preharvest factors. However, only a few preharvest factors are considered to have significant impact on fruit quality after harvest. 1.4.1 Location Orchard on soils with poor drainage or a low slope favors the occurrence of translucent aril and ‘gamboges’ (Laywisadkul, 1994; Chutimunthakun, 2001). ‘Gamboges’ is a physiological disorder that leads to the occurrence of yellow latex exudate on the pericarp surface and occasionally the aril. Therefore, growers seek land for growing mangosteen trees that has good drainage and also higher slope. Over watering of trees can also result in translucent aril and ‘gamboge’. 1.4.2 Fertilizer Application of complete chemical fertilizers plus calcium and zinc, during fruit growth plays an important role in ensuring high yield and quality of mangosteen

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fruit. Good fertilization practice can also reduce the occurrence of translucent aril and gamboge. Fertilizer is applied at least three times during vegetative growth, again pre-flowering and lastly during fruit development (Sdoodee et al., 2006). 1.4.3 Pests Thrips are considered to be the most important insect pests. They feed on young fruit with the scars becoming obvious at fruit maturation concomitant with the change from green to reddish and purple (see Plate II(A) in the colour section). Typical symptoms include silvering of fruit skin, pale yellow/brown discoloration, elongated and patchy scars or hardened scars, and ‘alligator skin’ like scars that may cover the entire fruit surface (see Plate II(A) in the colour section). Heavily scarred skin can sometimes prevent normal fruit growth (Affandi and Emilda, 2009). Fruit from outside the canopy are more likely to have thrips damage than those inside the canopy (Sdoodee et al., 2006). According to Affandi and Emilda (2009), several thrips control methods used for other fruit can be adopted for mangosteen. For example, botanical pesticides such as ‘Sabadilla’ derived from the seeds of Schoenocaulon officinale, as well as biopesticides such as abamectin and spinosad can be used (Hoddle et al., 2002; Wee et al., 1999; Faber et al., 2000; Astridge and Fay, 2006). Other cultural control techniques used to reduce thrips population are composted organic yard waste, composted mulch applied under plant canopy, and augmentation of predatory thrips Franklinothrips orizabensis, F. vespiformis and Leptothrips mc-cornnelli (Hoddle et al., 2002; Wee et al., 1999). The University of California Statewide Integrated Pest Management Program (2006) suggested integrated pest management (IPM) for controlling thrips. Such a plan would include the optimal use of natural enemies, removing all weeds under the canopy to eradicate alternative hosts, regular pruning of infected trees, use of a fluorescent yellow sticky trap, and application of reflective mulch to disturb host plant orientation of the thrips. Use of fluorescent yellow sticky traps is limited for monitoring the population of thrips due to the cost of adhesive glues such as the one called tangle foot (Chu et al., 2006). Chemical insecticide should be used as a last alternative. If necessary, monochrotophos, methiocarb or carbosulfan can be applied in mangosteen orchards to control thrips. After harvest, thrip-damaged fruit can be coated with carnauba or shellac waxes that results in a better appearance. The appearance of damaged fruit after coating resembles that of normal fruit (Phongsopa et al., 1994). This practice is used by Thai exporters.

1.5

Postharvest handling factors affecting quality

1.5.1 Temperature management The rapid ripening of mangosteen fruit at ambient temperatures is accompanied by shriveling of the calyx. The pericarp color changes and calyx shriveling result

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in the loss of marketability within a few days. Temperature management is essential to prolong shelf life. Storage of fruit at low temperature is commonly used to maintain quality and extend shelf life, because low temperature reduces the rate of respiration, ethylene production and other metabolic processes (Wills et al., 1998). Mangosteen can be stored at 12–13 °C and have a shelf life of about three weeks with acceptable eating quality (Choehom et al., 2003). Storage at 4 or 8 °C can lead to significant pericarp hardening, although the aril may still be acceptable after 44 days (Augustin and Azudin, 1986). When stored at 4 to 8 °C, surface coatings can reduce weight loss, prevent calyx wilting and assist in maintaining appearance. Dipping the calyx and the stem end of the fruit in various concentrations of hormones (e.g., BA, GA3 and NAA) before storage at 12 °C also delays shriveling and extends the storage period (Choehom et al., 2003). 1.5.2 Physical damage The surface of the mangosteen pericarp consists of a continuous epidermis layer covered by cuticular wax with lenticels. The epidermis covers a thick layer of parenchyma tissue and inner strip of sclereids (Phongsopa et al., 1994). The spongy pericarp serves as an excellent packing material to protect the soft aril during transportation. However, mechanical injury due to compression or impact injury, common in handling, results in some pericarp hardening (Tongdee and Sawanagul, 1989; Ketsa and Koolpluksee, 1992). Mechanical injury induced firmness increase occurs within three hours of the injury to both reddish and dark purple fruit. The firmness increase in injured dark purple fruit occurs more rapidly than that to reddish brown fruit. Regardless of fruit maturity, holding fruit in a nitrogen atmosphere after injury significantly inhibits the firmness increase compared to fruit held in air (Bunsiri et al., 2003). The firmness that develops is directly related to the height from which the fruit are dropped, the higher the drop height, the greater the firmness that occurs in the damaged pericarp (Tongdee and Sawanagul, 1989; Bunsiri et al., 2003). Thrips caused the greatest percentage of fruit surface scarring (46.7%) preharvest, while pericarp hardening is a harvest and postharvest handling problem which at the consumers’ home can affect 33% of the fruit. Pushpariksha (2008) summarized the impact on postharvest quality of mechanical injury as pericarp cracking, surface scarring, pericarp hardening, aril translucency, gamboge and decay. 1.5.3 Water loss The thrip-damaged epidermis at anthesis leads to the formation of a periderm layer as the fruit develops. These thrip-damaged fruits have a higher weight loss rate of 2.23% per day after harvest, compared to 1.63% per day for undamaged fruit (Phongsopa et al., 1994). Weight loss also induces pericarp hardening similar to the pericarp hardening associated with chilling injury (Dangcham et al., 2008), whereas impact induces pericarp hardening only in the damaged area (Bunsiri et al., 2003). Calyx and stem end shrivel are related to weight loss and results in

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poor postharvest appearance (Choehom et al., 2003). When stored at 13 °C (89–90% RH), weight loss of up to 6.8% can occur in 18 days, while coated fruit lose about 4% (Noichinda, 1992). Wax application reduces weight loss during storage at both ambient and low temperatures (Noichinda, 1992; Phongsopa et al., 1994; Choehom et al., 2003). Plant growth regulators such as BA, GA3 and NAA applied in combination or alone prior to storage, delays calyx and stem end shriveling (Choehom et al., 2003). 1.5.4 Atmosphere and coatings The recommended controlled atmosphere storage conditions are 13 °C, with 10–15% carbon dioxide and 2% oxygen (Pakkasarn, 1997). Aryucharoen (2004) confirmed the 13 °C storage temperature but recommended 3–5% carbon dioxide and 2% oxygen. For maximum storage life Wichitrananon (2001) found that fruit stored at 13 °C are still acceptable after 42 days when stored in 0% carbon dioxide and 0% oxygen. Fruit wrapped with polyethylene and polyvinyl chloride films and stored at 13 °C had almost twice the storage life of fruit stored without wraps (Pranamornkij, 1997). Ratanatraiphop (2003) reported that fruit coated with Stra-fresh #7055, glucomanan, chitosan and methylecellulose reduced weight loss, softening and pericarp color change, respiration rate and ethylene production during storage at 15 °C and had a storage life of 28 to 32 days, while the control fruit had storage life of 24 days. Similarly, Chanloy (2006) reported that fruit coated with 1% methylcellulose and 1000 mg/l GA, placed into polyethylene bags with 3% carbon dioxide or without polyethylene bags and stored at 13 °C had storage life of 32 and 28 days, respectively, compared to 24 days for the control.

1.6

Physiological disorders

1.6.1 Chilling injury The symptoms of CI in mangosteen fruit included darkening and hardening of the pericarp (Kader, 2007). These symptoms occur when fruit are moved to higher temperatures following storage at less than 10 °C for longer than 15 days or more than five days at 5 °C. Decay susceptibility also increases at chilling temperatures. The aril may still have acceptable quality after 44 days at 4 to 8 °C (Augustin and Azudin, 1986). Pericarp hardening is the most common symptom of CI in mangostee fruit (Uthairatanakij and Ketsa, 1996; Ponrod, 2002; Choehom et al., 2003). Fruit stored at 6 °C had greater pericarp firmness than those stored at 12 °C and the more mature (reddish purple) fruit had greater firmness than less mature (reddish brown) fruit. The unacceptable CI symptom of pericarp hardening of mangosteen fruit is found within 5, 10 and 20 days after storage at 3, 6 and 12 °C, respectively (Choehom et al., 2003). The pericarp hardening is more pronounced after storage at 6 °C for nine days and then transferred to room temperature (29.5 °C) for three days.

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The lower the storage temperature the sooner pericarp hardening develops (Uthairatanakij, 1995; Uthairatanakij and Ketsa, 1996; Kosiyachinda, 1986; Dangcham et al., 2008). Pericarp hardening is associated with an increase in lignin content (Uthairatanakij and Ketsa, 1996; Dangcham et al., 2007). A negative correlation exists between total free phenolics and lignin contents, and pericarp firmness and is similar to that found in mangosteen fruit after impact (Ketsa and Atantee, 1998; Bunsiri et al., 2003). Lignin accumulation is also found in cherimoya fruit after prolonged storage at chilling temperature (Maldonado et al., 2002). Cai et al. (2006) reported that the firmness of loquat fruit increases during postharvest ripening and is positively correlated with lignin accumulation in the flesh tissue. Lignification is a process that also occurs in secondary wall formation and under special conditions such as wounding, pathogen attack or fungal elicitor treatment (Vance et al., 1980; Ride, 1983). The degree of mangosteen pericarp hardening due to CI is related to the activity of enzymes involved in phenolic metabolism. The decrease in phenolic occurs concomitantly with the increased firmness and lignin contents in mangosteen pericarp stored at low temperature and suggests that phenolics may be incorporated into lignin. The resulting incorporation leads to an increase in pericarp lignin contents and hardening. The turnover of phenolics in mangosteen fruit subject to chilling temperature may be more rapid than their synthesis resulting in decline in phenolics (Dangcham et al., 2008). Total free phenolics declined and lignin contents increased more rapidly in the more mature reddish purple fruit than in reddish brown fruit and was greater in fruit stored at lower temperatures (Dangcham et al., 2007). Total free phenolics declines throughout storage whereas phenylalanine ammonia lyase (PAL) activity slightly increases only at the end of storage. This result suggests that phenolics are being incorporated into lignin at the start of storage and that CI induced an increase in PAL. The increase in pericarp firmness following storage at 6 °C is about 16-fold, while the lignin contents increase about 1.75-fold. This difference in increase suggests that the increase in lignin contents alone may not fully explain the rapid increase in pericarp firmness after low temperature storage. Lignins are found in both the free and bound state in plant cell walls (Morrison, 1974) and participate in cross-linking cell wall polysaccharides (Kondo et al., 1990; Lam et al., 1994; Ralph et al., 1995). Ester linkage occurs between glycosyluronic groups and the lignin hydroxyl groups, and ether linkage between polysaccharides and lignins (Iiyama et al., 1994; Lawoko, 2005). In addition, linkages are formed between lignin and proteins (Keller et al., 1988; Whetten et al., 1998). In plant tissues, lignin synthesis is correlated with activities of many enzymes such as PAL, cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) (Lewis and Yamamoto, 1990). The increased firmness of loquat fruit (Cai et al., 2006) and bamboo shoot (Luo et al., 2007) is a consequence of lignification, and associated with an increase of PAL, CAD and POD activities. PAL is an important enzyme required for synthesis of phenolic compounds that catalyses the conversion of L-phenylalanine to trans-cinnamic acid, a precursor of various phenylpropanoids,

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such as lignins, coumarins and flavonoids (Hahlbrock and Scheel, 1989; Lewis and Yamamoto, 1990; Schuster and Retey, 1995). Chilling temperatures can generally stimulate the biosynthesis of phenolic compounds by enhancing PAL activity (Aquino-Bolaños et al., 2000). PAL activity has been reported to be involved with CI development in many plants such as ‘Fortune’ mandarin, pineapple and ‘Navelate’ oranges (Martínez-Téllez and Lafuente, 1993; SanchezBallesta et al., 2000; Zhou et al., 2003; Sala et al., 2005). PAL activity of fresh-cut asparagus also increased in the first 10 days, before decreasing during the latter period of storage concomitant with lignin content (An et al., 2007). These results are similar to the findings in mangosteen fruit stored at 6 °C. PAL mRNA accumulates at start of storage at 6 °C and then decreases. The increase in mangosteen PAL gene expression at low temperature occurs prior to the increased PAL activity, lignin accumulation and pericarp hardening (Dangcham et al., 2008). The accumulation of PAL mRNA initially without an increase in PAL activity and phenolic levels, might be the result of low temperature stress, while the accumulation when fruit are transferred to room temperature was concomitant with the pericarp hardening (Dangcham et al., 2008). Similarly an increase in LgPOD activity occurs in mangosteen fruit stored at 6 °C then transferred to room temperature. This increase in LgPOD is concomitant with an increase in POD activity, lignin content and pericarp hardening (Dangcham et al., 2008). Low O2 treatment applied during and after low temperature storage of mangosteen fruit does not reduce pericarp hardening. Pericarp firmness and lignin contents still increased under low O2 during storage at 6 °C and at room temperature after transfer from 6 °C. This contrasted previous reports that mangosteen pericarp damaged after impact and fruit stored at low temperature under N2 is not as firm, and had lower lignin contents and more total phenolics than damaged pericarp held in the air (Uthairatanakij, 1995; Ketsa and Atantee, 1998; Bunsiri et al., 2003). Low temperature may exert a greater inhibitory effect on many enzymes involved in lignin synthesis, while a low O2 level only affects the last lignifications step of monolignol polymerization (Imberty et al., 1985). We confirmed this by applying low O2 treatment to stored mangosteen fruit after transfer to room temperature, and this had a greater effect on pericarp hardening than low O2 treatment applied only during low temperature storage. This suggests that low temperature may delay biochemical reactions involved in PAL and POD activities and the metabolic turnover of phenolic would be slower. Upon transfer to room temperature, all biochemical reactions involved in lignin synthesis become more rapid and have a greater O2 requirement. POD activity in mangosteen pericarp is low when stored at 6 °C under low O2 level, but its activity increased after transfer to room temperature. Low O2 levels occur in fruit that have received a wax coating (Peng and Jiang, 2003; Dong et al., 2004) or in modified atmosphere packaging (Shen et al., 2006) and they also have reduced POD activity. POD activity in fruit pericarp after transfer from 6 °C to room temperature under low O2 level is low, while in normal air a small increase occurs. However, low O2 is also found to have no effect on POD activity at the

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end of storage. This confirms the previous idea that low temperature has a greater impact on biochemical changes than low O2 level. Moreover, POD activity in mangosteen fruit stored at 6 °C under low O2 and transferred to room temperature is high while lignin content is low. In contrast, POD activity in mangosteen fruit stored at 6 °C under normal air is low while lignin content is higher after transfer to room temperature. This indicated that O2 is required for the oxidation in the final step of polymerization for lignin synthesis in mangosteen pericarp (Bunsiri et al., 2003a). CAD activity in fruit pericarp does not change during low temperature storage or after transfer to room temperature while pericarp firmness increased. This suggested that CAD may not be a rate-limiting step in lignin synthesis in mangosteen fruit pericarp during low temperature storage. CAD activity in damaged pericarp of mangosteen fruit after impact increases 15 min after impact, concomitant with an increase in lignin synthesis, and CAD activity increases much more than PAL and POD activities (Bunsiri, 2003). The increase in lignin contents in loquat fruit (Cai et al., 2006), copper stress treated Panax ginseng root (Ali et al., 2006) and bamboo shoot (Luo et al., 2007) is associated with CAD activity. Furthermore, CAD activity in transgenic plants (CAD antisense) such as tobacco (Halpin et al., 1994) and poplars (Baucher et al., 1996) is reduced, but the amount of lignin does not change. Thus, CAD might not be related to lignin synthesis and pericarp hardening of mangosteen fruit stored at low temperatures. 1.6.2 Pericarp hardening after impact The firmness increase in mangosteen pericarp following impact is well recognized (Tongdee and Suwanagul, 1989; Ketsa and Atantee, 1998; Uthairatakij and Ketsa, 1996). The increase in damaged pericarp firmness is more rapid in more mature fruit, fruit subjected to a greater drop height, and when oxygen is present than in less mature fruit, lower drop height and low oxygen level. The increased firmness of damaged pericarp occurred concomitantly with an increase of lignin content (Fig. 1.6). Lignin content in damaged pericarp is less under nitrogen atmosphere than under oxygen, as the final step of lignin biosynthesis requires oxygen for the polymerization of monomeric lignin precursors catalyzed by peroxidase. The increase of lignin in damaged pericarp after impact is supported histochemical microscopy and consistent with the increase in thioglycolic lignin (Bunsiri et al., 2003b). Following impact, the firmness of damaged pericarp increased rapidly, concomitantly with an increase in lignin content. The increase in lignin content in damaged pericarp is substantial when compared to the increases in firmness of damaged pericarp, as the basal lignin content in undamaged pericarp is initially high. The increase in firmness of damaged pericarp three hours after impact is 215 to 385%, while the increase in lignin content of damaged pericarp is 150 to 288%, dependent upon fruit maturity and drop height. Lignin-carbohydrate complex (LCC) increase in damaged pericarp of mangosteen fruit and the increase in lignin and carbohydrate contents is greater than that of protein content. The increase in

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Fig. 1.6 Firmness (a) and lignin content (b) of undamaged (■) and damaged (…) pericarp of dark purple mangosteen fruit after physical impact at a drop height of 100 cm. Fruit were held at room temperature (29 °C) before impact (t = 0) or 15, 30, 60, 120 and 180 min after impact. Data are means ± SD of six replicate fruit (Bunsiri, 2003).

lignin, carbohydrate and protein contents in LCC of damaged pericarp requires oxygen (Whetten and Sederoff, 1995; Bunsiri et al., 2003b). A transient, significant increase is found in the activity of PAL, CAD and POD. The activity of PAL increases about four-fold, that of CAD about eight-fold; and POD activity increases about six-fold within 15 min after mechanical impact. The significant increase in activities is found to occur between 10 and 15 minutes after impact, and a considerable decrease in activities is observed between 15 and 20 minutes after impact (Bunsiri, 2003). The data indicates that mechanical impact induces a concomitant increase in the activities of several enzymes involved at the early (PAL) and late stages (CAD and POD) of lignin synthesis. The rapid increase in the activities of PAL, CAD and POD in the pericarp slightly precedes (15 min) a detectable increase in pericarp lignin levels (Fig. 1.7). The increase in the activity of these and other enzymes might therefore be the cause of the increased lignin levels (Boudet, 2000). The present results are similar

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Fig. 1.7 Phenylalanine ammonia lyase (a), cinnamylalcohol dehydrogenase (b) and peroxidase (c) activities of undamaged (…) and damaged (■) pericarp of dark purple mangosteen fruit after physical impact at a drop height of 100 cm. Fruit held at room temperature (29 °C) before impact (t = 0) or 15, 30, 60, 120, 180 min after impact. Data are expressed as units per mg pericarp protein, whereby one unit is defined as the activity to produce 1 μM cinnamic acid within 1 h. Data are means ± SD of six replicate fruit (Bunsiri, 2003).

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to those found in bamboo shoots, where an increase in firmness after harvest was positively correlated with an increase of the contents of lignin and cellulose. The lignin accumulation in the bamboo shoot is positively correlated with an increase in the activities of PAL, CAD and POD (Luo et al., 2007). The rapidity of the increase in enzyme activity (four- to eight-fold increase) in as little as 15 minutes after the mechanical impact indicates that de novo synthesis of the proteins is unlikely. A detectable increase in protein synthesis by an outside stimulus, if involving the activation of genes, usually requires at least one hour (Alberts et al., 2008). The present data suggest that the mechanical impact leads to activation of existing proteins. If so, it is at present unclear how the impact would exert such a post-translational effect. 1.6.3 Translucent aril Translucent aril is a major physiological disorder that develops in the field before harvest. Symptoms are internal and include flesh changes from white to translucent (see Plate II(B) in the colour section) and textural changes from soft to firm and crisp (Pankasemsuk et al., 1996). Heavy and continuous rains during fruit growth and ripening favor translucency development in certain locations where the drainage is poor. The greater the rainfall that occurs at harvest times, the higher the incidence of fruit with translucent arils. The incidence of translucent aril is assumed to be caused by excess water uptake during fruit growth and development. The excess water may penetrate fruit rind, subsequently causing translucent aril (Sdoodee and Limpun-Udom, 2002). Orchards with greater slopes and better drainage have a lower incidence of fruit with translucent aril. Orchards with shallow water tables (1 to 50 cm) also have higher incidence of translucent aril than orchards with deeper water tables (101 to 200 cm) (Chanaweerawan, 2001). Similarly, when mangosteen are irrigated (75 mm per day) for five days during the harvesting, more fruit have translucent aril than trees with normal irrigation (15 to 20 mm per day) (Laywisadkul, 1994). The crucial period when excess rainfall or irrigation can lead to greater incidence of fruit with translucent aril is from about nine weeks after blooming (Chutimunthakun, 2001). The aril that is translucent is firmer than normal, and the translucent aril tissue has twice the amount of damaged protoplasts than normal aril. This is assumed to be due to excessive water uptake causing higher turgor pressure resulting in disruption of plasma membrane and cell death. Subsequently water and solutes leak out from protoplasts to the intercellular space leading to translucent aril (Luckanatinvong, 1996; Dangcham, 2000). Translucent aril has lower alcohol insoluble solids, soluble pectin and CDTA soluble pectin and higher Na2CO3 soluble pectin than normal aril (Dangcham, 2000). The translucent aril also contains higher ratio of K : Ca, K : Mg, and K : Ca+Mg than normal aril (Pludbuntong, 2007). Accumulation of calcium in light-exposed fruit is higher than shaded fruit and the incidence of translucent aril is lower in fruit on the top of the canopy that are light-exposed (Chiarawipa, 2002). The pericarp of non-

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translucent fruit contains higher N, Ca, K, and B contents than fruit with translucent aril (Pechkeo, 2007). Since calcium plays an important role in maintaining cell wall integrity (Helper, 2005), low content of Ca may lead to weaken cell walls of aril that cannot resist the influx of water. Foliar application of calcium chloride and boric acid to mangosteen trees increases the ratio of normal aril to translucent aril fruit (Pechkeo, 2007). Top cutting, soil mulching and foliar application of calcium can also alleviate the incidence of translucent aril (Chiarawipa, 2002), while soil application of complete fertilizers to mangosteen trees prior to full bloom and foliar application of complete fertilizers plus zinc during fruit set can reduce translucency in aril (Jirapat, 2002). 1.6.4 Gamboge Gamboge or gummosis is also a physiological disorder characterized by yellow exudation of gum onto the fruit surface (see Plate II(C) in the colour section). Sometimes yellow gum is also exuded from the inner pericarp into aril surface or between the carpels inside the fruit (see Plate II(C) in the colour section). The aril with the yellow gum tastes bitter, so consumers avoid buying mangosteen fruit with yellow gum on the fruit surface. It is believed that the environmental conditions that cause both translucent aril and gamboge are the same. Heavy and continuous rains during fruit growth and ripening favor gamboge in certain locations where the drainage is poor. However, the evidence that water relations are involved in gamboge is not strong as for aril translucency. An imbalance or deficiency of essential elements in soil and mangosteen tree may also contribute to gamboge (Pechkeo, 2007). Fruit harvested early in the season have a higher incidence of gamboge than fruit harvested late irrespective of the amount of rainfall. Extra irrigation does result in more fruit with gamboge (Laywisadkul, 1994). Even though environmental conditions and nutrient deficiency are believed to be involved in the incidence of gamboges, it is not known how this occurs. Latex in mangosteen fruit is produced by latex cells or laticifer inside the pericarp and exported via laticiferous vessels. Under conditions of the excessive water uptake breakage of laticiferous vessels may occur, which in turn allows yellow gum to leak out from pericarp and this yellow gum moves inward to aril or outwards to the fruit surface. Soil drainage, soil mulching, top pruning and foliar application of calcium, boron and zinc can alleviate gamboge (Chiarawipa, 2002; Jirapat, 2002; Pechkeo, 2007).

1.7

Pathological disorders

Unlike other tropical fruit, pre and postharvest diseases of mangosteen fruit are not a serious problem. This may be due to the pericarps physical and chemical properties. The fruit pericarp is thick and hard, and contain chemicals whose activity can act as antibiotic compounds. Occasionally postharvest diseases are reported for mangosteen fruit such as black aril rot caused by Lasiodiplodia theobromae (Pat.) triffon and Manbl (Botryodiplodia theobromae), white aril rot

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caused by Phomopsis sp. (Sacc.) Bnbak and soft aril rot caused by Pestalotia sp. Seaver. Most of these diseases infect the fruit in orchards and it is recommended to periodically spray with an approved fungicide before harvest (Visanthanon, 1999).

1.8

Harvesting practices

Mature fruit at any stage from Stage 1 to Stage 6 can be harvested depending on the market and purpose. Common practice for growers in Thailand is to pick up fruit at Stage 1 (light greenish yellow with 5–50% scattered pink spots) for export markets, Stage 2 (light greenish yellow with 51–100% scattered pink spots) or Stage 3 (reddish pink) for the local and regional markets. The sensory quality of fruit harvested at Stages 1 to 5 and ripened to Stage 6 is similar to fruit harvested at Stage 6 from the tree (Palapol et al., 2009a). Since mangosteen fruit are prone to pericarp hardening after impact, growers harvest carefully to minimize physical damage using baskets made of linen cloth or nylon net connected to bamboo poles to reach mangosteen fruit high in the tree. Fruit are carefully placed into plastic baskets and then taken to a packinghouse or directly to the markets.

1.9

Postharvest operations

1.9.1 Packinghouse practices Fruit in containers are moved from the orchard to a packinghouse or packing station. The containers must be able to protect the fruit against bruising and abrasion, so fruit should not be packed in containers over 30 cm deep otherwise fruit at the bottom will be subject to compression injury resulting in pericarp hardening. Fruit are culled to separate good fruit without skin damage from fruit with skin and calyx blemish, and sorted so that undersize fruit can be sold in local markets. Fruit are graded based on color according to market requirement for export or local use. After grading, yellow gum on the fruit surface is scrapped off with a knife and pressurized air supply is used to blow insects and dirt from underneath the calyx. Fruit for export are graded by weight and the normal range is 70 to 100 g per fruit, while undersized fruit with and without skin blemish are sold at the local markets. Fruit for export are packed individually into partition sections of single-layered corrugated 5 kg cartons or four fruit are packed into individual foam or plastic trays wrapped with PVC film and packed into a master carton. The latter is better at preserving calyx and stem freshness but increases packing costs. 1.9.2 Control of ripening Mangosteen is a climacteric fruit with a respiratory peak that occurs sooner when fruit are treated with ethylene (Noichinda, 1992). Inhibition of ethylene biosynthesis or ethylene action, therefore, may be effective in slowing down a number of ripening

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processes. A six-hour treatment with 1-MCP delays pericarp color development and aril softening during storage at 25 °C or 15 °C, leading to a longer shelf life (Piriyavinit, 2008). In fruit stored at 25 °C and treated with 1-MCP, the typical pericarp color changes are delayed until about day 6, and the decrease of aril firmness is delayed until day 4. At 15 °C, the pericarp color changes are inhibited until day 15, and the aril firmness only until day 4. Thai exporters have adopted a six-hour 1-MCP fumigation to delay pericarp color change and this provides greater flexibility in handling. Care is needed to avoid high rates of 1-MCP fumigation that can lead to pericarp hardening and fruit that will not be ripened normally. The use of gaseous ethylene and calcium carbide does not stimulate early ripening of mangosteen fruit compared to the control fruit. This suggests that the ripening process has already been induced before Stage 1 (Piriyavinit, 2008) or that the fruit’s sensitivity to ethylene increases during ripening. 1.9.3 Storage recommendation Fruit can be stored at room temperature (28 to 29 °C) for a few days, and their calyx and stem ends will start to become shriveled. The fruit pericarp will also be hardened due to weight loss as the storage time at room temperature is increased. Mangosteen fruit is a tropical fruit which is prone to chilling injury if stored below 10–12 °C (Choehom et al., 2003; Dangcham et al., 2008). This optimum storage temperature of 10–12 °C (85–95% RH) gives a storage life of approximately three weeks with an acceptable aril quality (Choehom, 2003; Noichinda, 1992). Mangosteen fruit can be stored below the optimum temperature for only a few days and must be consumed right after removal from low temperature storage otherwise the fruit pericarp will become hardened due to chilling injury (Dangcham et al., 2008).

1.10

Processing

1.10.1 Fresh-cut Unripe mangosteen fruit are used in the fresh-cut trade and not the ripe stage as used for other fruit. The fresh-cut mangosteen product is crispy with a sweet taste. This product is popular in southern Thailand, one of the main mangosteen growing areas. Mangosteen fruit at Stage 0 (yellowish white or yellowish white with light green) or Stage 1 (light greenish yellow with 5 to 50% scattered pink spots) are chosen and their pericarp is carefully removed from the aril in order to prevent latex from the pericarp contaminating the aril and resulting in aril darkening and a bitter taste. Aril without the pericarp is soaked in lime water solution (calcium hydroxide solution) containing 1% alum + 1% NaCl, or 0.50% citric acid + 0.25% calcium chloride (Kitpipit, 2005) for 30 minutes to prevent browning and softening. Subsequently the aril is washed with clean water, and all arils with blemishes are removed. The whiteness of fresh-cut aril can only be maintained for about five hours and then it changes steadily to an unappealing darker color. Fresh-cut mangosteen is prepared daily to meet demand.

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1.10.2 Paste Ripe or over-ripe mangosteen fruit are used to make a mangosteen paste. Fruit are cleaned and the pericarp removed. Aril with or without seeds is heated and stirred with medium or low heat. Thirty kilograms of mangosteen fruit make about 1 kilogram of paste, which can be processed into leather or candy. The paste with seeds has a nutty taste. 1.10.3 Juice Mangosteen fruit has a high content of antioxidants which are thought to be beneficial for health and this presumed health benefit has meant that mangosteen juice has become increasingly popular. Aril is boiled (2:3, v/v) and filtered to remove the seeds. Sugar and salt are added to the juice to improve flavor and boiled once more. Since the juice is white, it is not regarded as attractive as the fresh intact mangosteen fruit. Therefore, colorant extracted from mangosteen pericarp is added to the juice to improve juice color to be slightly pink. If too much mangosteen colorant is added, the juice tastes astringent due to tannins in the pericarp. The juice is marketed in metal cans, plastic or glass bottles. 1.10.4 Drying The pericarp of ripe or overripe mangosteen fruit is removed. The aril with seeds whose water content is approximately 70% is dried at less than 80 °C for two hours and at 70 °C for eight hours. Aril and seeds become a homogenous mixture after drying and the water content is reduced to approximately 13%. Dried aril tastes sweet and sour and with seeds will also have a nutty taste because of seed kernel. Ten kilograms of mangosteen fruit yields about 1 kilogram of dried product. Since pericarp of mangosteen fruit is rich in chemicals whose properties can be used as medicine, the pericarp can be dried similarly to the aril and kept for future use. Dried pericarp can be also made into powder and kept for medical use. 1.10.5 Freezing Mangosteen fruit at Stages 4 or 5 can be frozen. Fruit without blemish and defects are cut into halves at the equatorial planet and opened to check if the fruit aril is translucent or has no gamboge. Blemish free fruit are then wrapped individually with plastic tape surrounding the cut area and frozen at −40 °C for 120 minutes. If the fruit had not been cut in halves, it takes ~140 minutes to freeze. The frozen fruit must be stored at −20 °C. Sophanodora and Sripongpunkul (1990) reported that arils dipped in the solution containing 0.25% calcium chloride and 0.50% citric acid for one minute before freezing at −30 °C for 220 minutes retained their natural color and were accepted by consumers. 1.10.6 Freeze-dried and other products After the pericarp is removed, the aril can be freeze-dried in a three step process. First, the aril is frozen at −40 to −20 °C for 2 to 6 hours, then held under vacuum

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(10 mtorr) at −20 to 10 °C for 5 to 10 hours. Thirdly, aril is frozen at −10 to 0 °C for 2 to 6 hours. Freeze-dried mangosteen is sealed in aluminum foil-lined plastic bags to prevent moisture absorption and light exposure. The freeze dried product has a shelf life at room temperature of at least six months. Mangosteen fruit can be processed into other products such as wine, vinegar, ice cream, yoghurt and cosmetics.

1.11

Conclusions

Mangosteen fruit is named the Queen of Tropical Fruit due to its attractive appearance and taste. Nowadays mangosteen fruit are consumed worldwide, either fresh or processed, because they have amazing compounds whose properties have a great potential benefit to human health. However, fresh mangosteen fruit are perishable and sensitive to chilling injury and a barrier to marketing. Preharvest fruit disorders for which solutions are not available can lead to significant harvest and postharvest loss.

1.12 Acknowledgements The research cited in this chapter was made possible, in part through financial support from the Thailand Research Fund (TRF) and the Commission on Higher Education, Ministry of Education and Kasetsart University Research and Development Institute (KURDI).

1.13

References

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2 Melon (Cucumis melo L.) M. E. Saltveit, University of California, Davis, USA

Abstract: Melons contribute to the nutritive and aesthetic quality of our diet. When harvested mature, most melons exhibit a climacteric in respiration and ethylene production coincident with ripening (i.e., softening, aroma development). Ethylene antagonists, such as CO2 and 1-methylcyclopropene (1-MCP), can slow ripening. Sugar content usually declines after harvest because of the lack of storage carbohydrates to be hydrolysed into simple sugars. The chilling sensitivity of most melon cultivars precludes their storage below 5 ° to 10 °C, but this sensitivity varies greatly with cultivar and stage of maturity. Fresh-cut melons are increasingly important and present unique postharvest challenges to maintain quality. Key words: melon, postharvest, climacteric, chilling injury, fresh-cut.

2.1

Introduction

2.1.1 Botany, morphology and structure Melons are cucurbits; cultivated species of the Cucurbitacese. This family contains about 750 species in 96 genera that are found mainly in the tropics. Most plants are tendril-bearing vines that produce fleshy fruits derived from an inferior ovary; a pepo. The four major cucurbit crops are cucumber, melon, squash (pumpkin), and watermelon (Table 2.1). This chapter will focus on the postharvest biology and technology of melons (Cucumis melo L.). The specie Cucumis melo is further divided into several botanical varieties or types. The three most important types are cantalupensis, inodorus, and reticulates (Table 2.2) Melons are monoecious or andromonoecious annuals with long trailing vines and round stems. Staminate flowers are borne in axillary clusters on the main stem, while perfect flowers are borne at the first node of lateral branches. The flowers are predominately yellow. The fruit is a multi-carpled berry that is epigynous. Fruits vary in size, shape, rind characteristics, and flesh color depending on variety. Seeds are cream-colored, oval, and on average 10 mm long.

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Postharvest biology and technology of tropical and subtropical fruits Table 2.1 The four major cucurbit crops Common name

Scientific name

Melon Cucumber Watermelon

Cucumis melo L Cucumis sativus L. Citrullus lanatus (Thunb.) Matsum. & Nakai. Cucurbita maxima Duch. Ex Lam. Cucurbita moschata Duch. Ex Poir. Cucurbita pepo L.

Squash, pumpkin Squash, pumpkin Squash, pumpkin Table 2.2

Major groups of melons (Cucumis melo L.)

Scientific name

Characteristics

Cantalupensis

Skin that is rough and warty, not netted. European cantaloupe and Algerian melon.

Inodorus

Canary melon, Casaba, Kolkhoznitsa melon, Hami melon, honeydew, Navajo Yellow, Piel de Sapo/Santa Claus, sugar melon, tigger (tiger) melon, and Japanese melons.

Reticulatus

True muskmelons, with netted skin. Examples include Bailan melon, North American cantaloupe, Galia, Ogen, Persian, Sharlyn melons. Modern crossbred varieties, e.g. Crenshaw (Casaba X Persian), Crane (Japanese X N.A. cantaloupe)

2.1.2 Worldwide importance China produces about 50% of the world’s crop by weight. Turkey and Iran are the next largest melon-producing countries, with the U.S. and Spain rounding out the top five producers. Europe, Central America, and Africa are also important world production centers. In Japan, melons are usually grown in greenhouses. The yield of US Western Shipping melons has remained stable for the last 20 years. In 2008, the total value of US cantaloupe production was $371 million and honeydew production was valued at $68 million. Cantaloupe production was the highest on record since 2003, while honeydew production was the lowest on record since 1992. Combined, all melons made up the third highest ranked vegetable crop in the US behind lettuce and onions. 2.1.3 Culinary uses, nutritional value and health benefits Melons are usually consumed as desserts, snacks, breakfast or picnic foods. Recently, processed melon products (e.g., pre-cut product displays, in-store salad bars) have been developed to appeal to the single serving market and to smaller households. Seedless varieties have also helped spur consumption. Improved harvesting and handling techniques, as well as the development of sweeter hybrid varieties have improved quality and consumer acceptance. However, even under the best conditions, total carotenoids and vitamin C declined after harvest.

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A serving of cantaloupe is about 180 grams (1 cup; 250 ml) and contains 60 calories. There is little fat and only 1 g of protein per serving. The carbohydrates are comprised of 14 g of sugar and 2 g of dietary fiber. The yellow and orange fleshed melons contain beta-carotene (provitamin A), and all melons are good sources of vitamin C. A serving of cantaloupe supplies 120% and 110% of the daily requirements of vitamin A and C, respectively. This food is also a good source of niacin, vitamin B6, folate, and potassium.

2.2

Fruit development and postharvest physiology

2.2.1 Fruit growth, development and maturation After pollination, the kinetics of growth is a simple sigmoid curve with the initial phase of cell division accompanied by small changes in fruit size. Expansion of cells gives rise to a linear increase in size over time. Fruit growth is uniform along all dimensions to produce spherical fruit or predominately along the longitudinal axis to produce oblong fruit. Unlike fruit in which cellular expansion occurs primarily at the floral end, the roughly uniform expansion of melon fruit produces a uniform distribution of minerals throughout the tissue. The dilution of poorly translocated minerals (e.g., calcium) in tissues that expand to a greater extent than others can produce a dilution of essential minerals and make the tissues susceptible to physiological disorders such as blossom end rot in tomatoes and bitter pit in apples. This unequal distribution does not occur in melons, so if any physiological disorders occur (e.g., surface pitting from chilling injury), they are uniformly distributed about the surface. Maturation of the fruit is marked by a reduction and finally a cessation of increases in both size and fresh weight, while the rate of increase in dry weight due to translocation of sugars continues to decline as fruit near full ripeness. An abscission layer forms in the subtending stem in the cantaloupe and muskmelon types, while such a physical abscission zone fails to develop in the inodorus group. However, physiological abscission may occur in all melons even before the start of the development of a physical abscission layer as the result of diminished function of the vascular system (i.e., phloem and xylem) as fruit attain full size and start to ripen. The ease of separation of the fruit at the abscission zone provides an excellent indicator of harvestable maturity. The lack of an abscission zone in honeydew may explain why their maturity at harvest can be so variable. It is difficult to ascertain the level of maturity by a purely visual examination of the exposed honeydew fruit in the field. A gentle tug can easily separate a mature cantaloupe fruit from the vine, while honeydew fruit must be cut from the vine to prevent tearing of the fruit near the point of detachment from the stem. 2.2.2 Respiration, ethylene production and ripening Most melons are climacteric and exhibit elevated rates of respiration and ethylene production coincident with ripening (Fig. 2.1). During normal ripening, melons

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Fig. 2.1 Climacteric rise in respiration and ethylene production in cantaloupe melons left on the vine (attached) or harvested (detached). The arrows indicate when the fruit were harvested or when they naturally abscised (Shellie and Saltveit, 1993).

can produce copious amounts of ethylene which stimulates their further ripening and can affect ethylene sensitive crops stored with them. The stimulation of ethylene production by ethylene is termed auto-catalytic ethylene production. Holding partially ripe cantaloupes and other melons at 15 ° to 20 °C will allow them to produce their own ethylene and develop good eating quality without additional ethylene treatment. In fact, ethylene exposure may promote rapid ripening with the loss of shelf life. Honeydews (and other ‘winter’ melons) are sometimes harvested before they develop the ability to produce enough ethylene to ripen normally. Exposing these fruit to 100 to 150 ppm ethylene in air for around 24 hours stimulates ripening with its associated changes in aroma and softening. However, most melons are now harvested mature enough to not require a postharvest ethylene treatment. The sugar content of harvested melons does not increase upon ripening because at harvest, mature melons do not have extensive reserves of starch which can be hydrolyzed into sugars. Improper handling (e.g., elevated temperatures, injuries) can stimulate respiration with the loss of sugars and taste quality.

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Softening associated with ripening has been extensively studied and mutant lines have been created through traditional plant breeding or generic engineering with diminish rates of softening (Pech et al., 2008). The disruption of ethylene production or sensing has been a major focus of such research. However, the discovery that some components of ripening (e.g., aroma development) are not tightly coupled to ethylene production indicated that ripening could be modified by altering other metabolic pathways.

2.3

Maturity and quality components and indices

Melons are harvested by maturity, not by size; although size is an important component of their marketability. The soluble solids (e.g., sugar) content is the primary factor governing maturity. 2.3.1 Commercial maturity of cantaloupe Maturity is optimal at the firm-ripe stage or ‘3/4 to full-slip’ when a clear abscission (i.e., slip, separation) from the vine occurs with light pressure. Cantaloupes can ripen after harvest (i.e., soften and develop characteristic aroma and flavor) but do not increase in sugar content. For maximum quality, cantaloupes should be harvested at the ‘full-slip’ stage for local markets since the sugar content, flavor and texture improve very rapidly as the fruit approaches this stage of development, but a less mature stage is optimal for shipment to distant markets to avoid excessive losses from over-ripeness and decay. High quality melons should be nearly spherical and uniform in appearance. An abscission zone should have formed producing a full slip with no adhering peduncle (i.e., stem-attachment). Fruit can be harvested at one-half or quarter slip if their soluble solids content is sufficiently high. The surface should lack scars, sunburn or other defects. The fruit should be firm with no evidence of bruising or excessive scuffing. The fruit should be heavy for its size and have a firm internal cavity without loose seeds or accumulated liquid. U.S. grades are Fancy, No. 1, Commercial and No. 2. Distinction among grades is based predominantly on external appearances and measured soluble solids. Federal Grade Standards specify a minimum of 11% soluble solids for U.S. Fancy (‘Very good internal quality’) and 9% soluble solids for U.S. 1 (‘Good internal quality’). A refractometer is usually used to measure the °Brix, which is accepted as the current standard measurement for soluble solids. Sizing is based on count per 18.2 kg (40 lb.) container. There are typically 9, 12, 15 and occasionally 18 or 23 melons per carton. A cardboard divider is folded at different locations to produce compartments for the different sized fruit (see Plate III in the colour section between pages 238 and 239). 2.3.2 Commercial maturity of honeydew There are three commercial maturities for honeydew melons.

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1 Mature, unripe. Ground color white with greenish accents, no characteristic aroma, peel fuzzy/hairy and not waxy. California Grade Standards establish a minimum legal harvest index of 10% soluble solids (10 ° Brix). 2 Mature, ripening. Ground color white with slightly discernible green tint, slightly waxy peel, blossom-end firm and unyielding, no or slight aroma. Preferred commercial maturity class. 3 Ripe. Ground color creamy white with yellow accents, clearly waxy peel, characteristic aroma noticeable, blossom-end yields slightly to press. The fruit should be well-shaped, nearly spherical and uniform in appearance. There should be an absence of scars or surface defects, with no evidence of bruising. The fruit should appear heavy for size, and the surface should be waxy and not fuzzy. The US grades are similar to those for cantaloupe, but more emphasis is given to surface appearance. Sizing is based on count per 13.6 kg (30 lb) container, most typically four or five, and occasionally six melons per carton. The maturity and ripeness of ‘Winter’ melons (e.g., Crenshaw, Persian, Casaba, Juan Canary, and Santa Claus) can be difficult to determine because they do not form an abscission zone and ‘slip’ from the vine when ripe. These melons may require ethylene to enhance ripening, which can be administered in transit from production areas, or at distribution centers.

2.4

Preharvest factors affecting fruit quality

Good cultural practices should be followed with adequate and consistent watering to avoid rapid expansion of the fruit which could cause cracking. Fertilization should allow uniform growth and provide sufficient trace minerals (e.g., calcium) to lessen the development of physiological disorders. However, calcium fertilization may have limited benefit because most soils have adequate calcium and calcium has limited mobility in the plant. Like other field crops, melon yield increased with increasing nitrogen fertilization, but quality was not affected by nitrogen level. Exposure to chilling or excessively high temperatures before harvest may increase the fruits susceptibility to postharvest chilling injury. Intense solar radiation on exposed fruit (either in the field or during transit to a packing facility in uncovered field containers) may raise the skin and underlying flesh temperature sufficiently to cause damage (e.g., sunburn, sunscald) with symptoms of skin discoloration and poor or abnormal ripening. Incomplete pollination can produce misshaped fruit; e.g., a pear-shaped fruit.

2.5

Postharvest handling factors affecting fruit quality

2.5.1 Temperature management Melons are often harvested in the summer at elevated temperatures. The fruit should be rapidly cooled soon after harvest to maintain optimal quality. Precooling

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to 10 °C is typical, but cooling to 4 °C is more desirable. Forced-air is the most common method used to cool field packed fruit. The use of hydrocooling is diminishing as packing shifts from the packing shed to the field. Immersion of hot fruit in cold water during hydrocooling may permit intrusion of water through the stem scar and the absorption of contaminants that have accumulated in the cooling water. 2.5.2 Physical damage Surface abrasion and scuffing, especially in the non-netted inodorus varieties, increases skin discoloration and water loss, which is a major cause of the loss of firmness. The open seed cavity in many mature melons makes them susceptible to a postharvest defect in which the tissues associated with the seeds become separated from the pericarp wall because of violent physical motion (e.g., rolling, dumping, shaking). The early harvest of US Western Shipping melons and their relatively closed cavity minimizes this type of damage during transportation to distant markets (see Plate IV in the colour section). 2.5.3 Water loss The spherical nature of melon fruit minimizes the surface to volume ratio, and their well developed rind and skin combine to limit water loss. However, apart from biochemical changes in cell wall plasticity which produces tissue softening, water loss can cause a loss of firmness. This is especially true in fresh-cut melon products where the removal of natural barriers to diffusion leaves the exposed tissue susceptible to vapor-pressure deficit driven water loss. Waxing, plastic wraps, packaging and maintaining high relative humidity surrounding the commodity have been be used to lessen water loss. 2.5.4 Atmosphere Melons, especially cantaloupes, derive a slight benefit from storage at 2 ° to 7 °C in 3 to 5% oxygen and 10 to 20% carbon dioxide. This fungistatic level of carbon dioxide suppresses decay on the stem and rind, and acts as an ethylene antagonistic to slow ripening with its associated softening and color changes. Controlled and modified atmospheres may also reduce chilling sensitivity. However, 20% carbon dioxide will cause a carbonated flavor in the fruit flesh which can be lost upon transfer to air. Oxygen levels below 1% and carbon dioxide levels above 20% may impair ripening and produce off-flavors and odors. Beneficial atmospheres can be generated by enclosing the fruit in plastic films. Plastic wraps can also reduce water loss and its associated loss of firmness. Melons shipped substantial distances (e.g., cantaloupes shipped from South America to Europe) often use a bag-in-box design where cooled fruit are placed within a plastic bag in a box. The bag is folded over before the box is closed. The

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bag retards gas diffusion so the humidity around the fruit increases, which lowers water loss, and fruit respiration elevates the carbon dioxide level to around 10% which retards microbial growth. Since this beneficial carbon dioxide level is a balance between carbon dioxide diffusion out of the bag and carbon dioxide production by the fruit, it is very important to maintain the temperature (and thereby the rate of respiration) for which the package design was optimized. Melons must be cooled before packaging and the maintenance of the proper temperature is crucial if they are to be kept in plastic during retail marketing. The high rate of respiration during the climacteric of ripening melons can produce sufficient heat to raise their temperature. Package design should allow sufficient air movement around the fruit to remove this vital heat and maintain the desired storage temperature.

2.6

Physiological disorders

2.6.1 Chilling injury Melons are chilling sensitive and are adversely affected by storage at low, non-freezing temperatures. The level of sensitivity varies with maturity, cultivar and previous growing and handling conditions. Cantaloupes are slightly chilling sensitive and can exhibit surface browning and increased decay after extended storage below 2 °C. Honeydew and other melons are more sensitive. In these melons, chilling produces water-soaked areas in the flesh, browning of the surface, increased decay and a failure to ripen normally (see Plate III in the colour section). Since chilling affects ripening, riper fruit (e.g., maturity #3 honeydew) are less susceptible to chilling injury. Honeydew that are mature but unripe should be stored at 10 °C, while ripe fruit can be stored at 5 ° to 7 °C without suffering chilling injury. Experimental treatments involving exposures to low or high temperatures for short intervals, dips in various aqueous solutions, and modified atmospheres have been developed which lessen the development of chilling injury symptoms. However, commercial handling of melons is best served by adhering to proper temperature management to avoid chilling in the first place. 2.6.2 Other physiological disorders Most physiological disorders (e.g., water soaked and flesh browning) are associated with exposure to extreme conditions; elevated temperatures, and ethylene or carbon dioxide concentrations, and low temperatures or oxygen concentrations. Premature softening and water-soaking of fruit flesh have been associated with low calcium levels. Postharvest dips in aqueous calcium solutions increase calcium levels in whole and segmented fruit. However, this method cannot be used with field-packed fruit. Melons develop few disorders after harvest if held under proper storage conditions.

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Pathological disorders

Postharvest losses are predominately caused by physical injury due to bruising and chilling injury and not by diseases. However, melons are susceptible to a number of bacterial and fungal diseases; they include powdery mildew, downy mildew, Alternaria leaf spot, Anthracnose, and Fusarium wilt. Melons are also susceptible to watermelon mosaic, cucumber mosaic, cantaloupe latent virus; diseases which are transmitted by aphids. Squash mosaic virus is seed borne and beetle transmitted. Curly top virus is transmitted by beet leaf hoppers. Melon diseases can be controlled through crop rotation, using resistant cultivars and approved fungicides. Disease vectors can be controlled with insecticides. Postharvest fungicide dips are essential to control postharvest diseases during storage, or long distance transport. A recommended fungicide application is a mixture of 500 ppm benomyl (Benlate) and guazatine (Panoctine). Hot water dips may be used to supplement or augment such fungicidal treatments.

2.8

Insect pests and their control

The pests which affect melons include melon aphid, green peach aphid, cucumber beetle, leafhopper, leaf miner, red spider mites, and melon worm. Soil pests include nematodes, wire worms, and corn seed maggot. Some insects are disease vectors, with bacterial wilt being transmitted by the cucumber beetle.

2.9

Postharvest handling practices

2.9.1 Harvest operations Melons are harvested mature and undergo significant changes in aroma production and firmness, and lesser changes in sugar content after harvest. Mature cantaloupes are harvested at the full slip stage when the fruit easily separates from the stem. Reduced susceptibility to mechanically injury and additional marketing-life can be achieved by harvesting the fruit at a mature, but less ripe stage of development. Less mature fruit do not so easily detach from the stem and these half-slip and quarter-slip fruits can be identified by the portion of stem remaining attached to the harvested fruit. Honeydew types of melons do not form this abscission zone between the fruit and stem. These fruit should be cut, not pulled from the vine to prevent mechanical damage to the stem-end of the fruit. Harvesting is almost entirely done by hand because it is difficult to distinguish the proper stage of melon maturity mechanically and to permit multiple harvests. Harvest aids are commonly employed in field packing operations and to pick up the boxed melons. However, the large machines necessary for field packing can severely damage the vines and only permit one harvest.

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2.9.2 Packinghouse practices Melons are warm-season fruit that are often harvested when day time temperatures are quite hot. Harvesting in the early morning or at night can reduce the heat load. Melons can be harvested into lined, low-volume bins for transport to packing facilities (Fig. 2.2). Bulk melons are usually dry dumped before being sorted and cooled. However, field packing is preferred to minimize handling and subsequent mechanical injury. Field heat is removed at the packing facility by hydro-cooling before grading, sizing and packing of bulk melons, or by forced-air cooling for packaged melons. Sizing and sorting the fruit to produce uniform packs and the application of post-harvest treatments (e.g., applying wax, fungicides) is more easily accomplished in a packing facility. Diligent supervision is needed to maintain consistent quality in field packing operations.

Fig. 2.2 Postharvest harvesting and handling of melon fruit that are packed in the field or in a packing shed.

2.9.3 Control of ripening and senescence Temperature management remains the primary means of controlling the rate of ripening. The rate of respiration, and thereby the rate of most associated metabolic processes increases two- to three-fold for every 10 °C rise in fruit temperature. Rapid ripening increases moisture loss and reduces quality and storage life. To maximize quality retention, harvested fruit should be cooled to their lowest tolerated temperature. Most fruit and vegetables should be stored at the

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lowest non-freezing temperature; usually 0 °C. However, since melons are chilling sensitive they must be stored at a higher temperature which naturally results in a shorter shelf life than non-chilling sensitive fruit. Since ripening is so tightly coupled with ethylene production, genetically modified lines of melons have been produced with greatly diminished rates of ethylene production. These lines have slower rates of ripening and extended shelflife. The natural variability in the amplitude and rapidity of the climacteric has also been used to develop lines with altered rates of ripening by traditional breeding methods. Interestingly, fruit left to ripen on the plant continue to exhibit a climacteric in ethylene production, but the rise in respiration (i.e., carbon dioxide production), which usually accompanies the rise in ethylene production in harvested fruit, is greatly diminished until the fruit is detached or naturally abscises (Shelly and Saltveit, 1993; Hadfield et al., 1995: Bower et al., 2002). It appears that detachment of the fruit during harvest interrupts the flow of something into the fruit which lessens the climacteric rise in respiration. Since the respiratory climacteric consumes sugars which are critical to the taste quality of the fruit, maintaining the effect of this inhibitory factor in harvested fruit could extend their shelf life and taste quality. Ethylene antagonistic such as carbon dioxide and 1-MCP can block ethylene perception and the positive feedback of ethylene on ethylene production and slow the rate of natural or imposed ethylene-induced ripening. However, although these treatments can slow ripening, their use does not diminish the need for prompt cooling and proper temperature management for optimal retention of quality. 2.9.4 Recommended storage and shipping conditions Storage life of cantaloupes is typically 12–15 days within the optimal range of 2.2 °–5.0 °C and 85–90% R.H. Holding the temperature at 2.2 °C can extend the storage life to 21 days, but sensory quality will be reduced as this reduces the production of characteristic flavors and aromas. Honeydews are slightly more chilling sensitive than cantaloupes and should be stored at 7 °C and 85–90% R.H for a storage life of 12–15 days. Short term storage during transit can range from 2.5–5 °C, but these exposures should be minimized since holding melons at these temperatures for seven days may induce chilling injury; especially in the more susceptible cultivars. The damage may not be apparent until the fruit are transfer to typical retail display temperatures where the symptoms of chilling injury will quickly develop. Temperature fluctuations resulting in condensation of water on the fruit’s surface should be avoided as the free water on the surface promotes mold growth. The optimum temperature and handling conditions for honeydew melons are essentially the same as for Crenshaw and Persian melons. Their storage period, however, is shorter and generally does not exceed 14 days. Casaba, Juan Canary,

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and Santa Claus melons retain best quality at the high end of the storage temperature range, 10 °C for up to 21 days.

2.10

Processing

2.10.1 Fresh-cut processing The main impediment to marketing fresh-cut melons is the loss of firmness and development of water-soaked areas. Retention of firmness and texture can be maximized with post-processing dips in aqueous calcium solutions. Various calcium salts have been studied (e.g., calcium chloride, calcium lactate), but each imparts a flavor which consumers may find objectionable. Rapid marketing and proper temperature and humidity management is absolutely crucial to maintain the quality of fresh-cut melons. Fresh-cut melon portions should be washed in a chilled chlorinated water bath immediately after cutting. A further wash in a chilled citric acid and tribasic calcium phosphate solution after sorting and grading would help to maintain quality. Although not the only route of contamination, edible portions of the melon flesh may be contaminated in the cutting or rind removal process. Treatments which would be too severe to apply to the whole fruit destined for prolonged storage and transit (e.g., gaseous ozone and hot water), can be used prior to processing since their main target is to decontaminate the peel which is removed during processing.

2.11

Conclusions

As packing moves away from using a packing shed to predominately field packing, postharvest treatments of whole fruit will be limited to those that can be applied to boxed fruit. Aqueous applications of waxes and fungicides, and quarantine treatments will need to be modified to accommodate the types of containers used in field packaging. The genetic engineering of various metabolic pathways; especially those involved in ethylene production and perception, will continue to be active areas of research and commercial implementation. Instruments are currently being developed that could nondestructively and rapidly measure fruit soluble solids. Once perfected, these instruments could be incorporated into mechanical harvesters, used by pickers to distinguish ripe and unripe fruit more effectively in the field, or used on a pack house grading line to segregate the fruit into maturity and quality classes that would have more uniform postharvest characteristics. Future genetic modifications and technological innovations may augment postharvest melon handling, but they will not eliminate the need for the basic tenants of postharvest biology and technology; maintain proper fruit temperature, relative humidity, and sanitation, and handle the fruit gently and rapidly.

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References

Beaulieu JC, and Gorny JR (2004) ‘Fresh-cut fruits’, in The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks, Agriculture Handbook Number 66, eds. Gross KC, Wang CY, and Saltveit ME, http://www.ba.ars.usda.gov/hb66/ contents.html Bower J, Holford P, Latché A, and Pech JC (2002) Culture conditions and detachment of the fruit influence the effect of ethylene on the climacteric respiration of melon, Postharvest Biol Tech, 26, 135–146. Hadfield KA, Jocelyn K, Rose C, and Bennett AB (1995) The respiratory climacteric is present in Charentais (Cucumis melo cv. Reticulatus F1 Alpha) melons ripened on or off the plant, J Expt Bot, 46(293), 1923–1925. Lester G and Shellie KC (2004) ‘Honey dew melon’, in The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks, Agriculture Handbook Number 66, eds. Gross KC, Wang CY, and Saltveit ME, http://www.ba.ars.usda.gov/hb66/contents.html Miccolis V and Saltveit ME (1991), Morphological and physiological changes during fruit growth and maturation of seven melon (Cucumis melo L.) cultivars, J Amer Soc Hort Sci, 116(6), 1025–1029. Miccolis V and Saltveit ME (1995), Influence of storage period and temperature on the postharvest characteristic of six winter-type muskmelon (Cucumis melo L.) cultivars, Postharvest Biol Tech, 5, 211–219. Pech JC, Bouzayena B, and Latchéa A (2008) Climacteric fruit ripening: Ethylenedependent and independent regulation of ripening pathways in melon fruit, Plant Science, 175(1–2), 114–120. Saltveit ME (2003), A summary of CA requirements and recommendations for vegetables, Acta Hortic, 600, 723–727. Saltveit ME (2003), ‘Fresh-cut vegetables’, in Postharvest Physiology and Pathology of Vegetables, eds. J.A. Bartz and JK Brecht, Marcel Dekker, Inc. pp. 691–712. ISBN: 0-8247-0687-0. Saltveit ME (2005), Wound-induced physiological changes in fresh-cut produce, Proc. APEC Symposium, August 1–3, Bangkok, Thailand. Shellie KC and Saltveit ME (1993), The lack of a respiratory rise in muskmelon fruit ripening on the plant challenges the definition of climacteric behavior, J Expt Bot, 44, 1403–1406. Shellie KC and Lester G (2004) ‘Netted melons’, in The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks, Agriculture Handbook Number 66, eds. Gross KC, Wang CY, and Saltveit ME, http://www.ba.ars.usda.gov/hb66/contents.html Suslow TV, Cantwell M, and Mitchell J (2009) Melon Produce Facts. http://postharvest. ucdavis.edu/Produce/ProduceFacts/Fruit/honeydew.shtml

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3 Nance (Byrsonima crassifolia (L.) Kunth) O. Duarte, National Agrarian University, La Molina, Peru

Abstract: Nance is a popular minor fruit in Central America commonly found in markets although there are practically no commercial plantations. The fruit is gathered from seedling trees that are sown either by birds or by man as backyard trees. The fruit can be sweet or acid and is used fresh in juices, boiled in syrup, candied or after having gone through an alcoholic fermentation process. Many people dislike it because of the soapy smell produced by its high fat content. The tree bark has high tannin content and is used to cure diarrhea and other ailments. Key words: nance, Byrsonima crassifolia, postharvest, tannin, fat content, alcoholic fermentation.

3.1

Introduction

3.1.1 Origin, botany, morphology and structure Nance, nancite (Central America), peralejo (Cuba), nanche, nanchi, chi, nanchite (Mexico), indano (Perú), changugu, craboo, maricao, peralejo, perdejo, peralejo de sabana (Caribbean), muricí (Brazil), golden spoon or golden cherry (USA), are some of the names of the fruit of Byrsonima crassifolia. This species is native to the dry tropical forests of southern Mexico, the Antilles, Central America and the Amazon basin in South America. It belongs to the Malpighiaceae family and several related species exist, such as Byrsonima coriacea, B. verbascifolia and others (Standley and Steyermark, 1946; Williams, 1981; Barbeau, 1990). It is an evergreen tree that can reach 10 m but normally will grow to 3–4 m in height. The trunk is not very straight and its wood can be used to make small wooden objects. The leaves are simple, entire, opposite, shiny on their upper side and have a short petiole. They can reach 6 to 16 cm length and 3 to 8 cm width. According to Morton (1987) the showy flowers are hermaphroditic with a diameter of about 1.5 cm. The five sepals are green and the five petals turn from yellow to an orange or reddish color as they get older. The flowers come in terminal

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inflorescences and change color gradually according to the age of the flowers so that the different colors can be seen in the inflorescence (see Plate V in the colour section between pages 238 and 239). The flowers are dependant on pollination by insects like Trigona folviventris Guerin., Apis mellifera and Polyubia occidentalis Oliver (Duarte and Vernon, 2002). The ovary is trilocular with one ovule per locule and with three stigmas. The fruit is a globular drupe measuring from 1 to 2 cm in diameter (see Plate VI in the colour section). The external peel is soft and normally turns from green to yellow, and sometimes orange, red when ripe. However the peel of some types remains green when ripe. The pulp is about 0.5 cm thick and white to yellowish-white or cream in color. The fruit can be sweet, acid or sometimes bitter. Fruit weight can vary from 2 to 5 g. The fruit has a single round stone in the center that consists of three embryos with their covers fused together. Therefore sometimes three plants can germinate from a single ‘seed’, but normally only one of the embryos germinates (Donadio et al., 2002). 3.1.2 Worldwide importance and economic value Nance is mainly consumed in its areas of production where most of the crop is sold by roadside vendors. The rest reaches the markets of certain cities in Mexico and Central America. In many of these countries, restaurants, juice vendors and housewives buy the fruit mainly to make juices or desserts. Some fruit is exported from Central America to Canada and the United States as frozen fruit or pulp, to avoid quarantine barriers. Also fruit in syrup or alcohol is exported in small amounts for Central American and Caribbean immigrants living in the United States or Canada. 3.1.3 Culinary uses, nutritional value and health benefits The fruit is normally eaten fresh but can also be processed into juices, pulps (which can be used in fruit yoghurts), jams (which have a buttery taste), alcoholic products or candied products or preserved in syrup (fruit composition is shown in Table 3.1). The fruit has a relatively high fat content and in some places lipids are extracted from it. According to Donadio et al. (2002) the peel can contain 25% fat and the seed around 11%, the pulp acidity is about 2.45% with a Brix of 4.49 °, the pH is around 3 and it has a low content of vitamins that according to Morton (1987) is about 0.010 to 0.014 mg thiamine, 0.015 to 0.039 mg riboflavin, 0.266 to 0.327 niacin and 90 to 129 mg ascorbic acid per 100 g of fresh pulp. Bayuelo-Jimenez (2008) says the distinct fruit aroma that some people dislike is mainly due to ethylbutanoate (sweet and fruity), ethylhexanoate (fruity), butyric acid (rancid cheese), hexanoic acid (pungent cheese) and phenylethyl alcohol (floral scent). The leaves and the trunk bark are rich in tannins, as well as the unripe fruits. The tannins are used for tanning and a decoction of this bark is used to cure diarrhea, to lower fever and as an anti inflammatory.

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Table 3.1 Chemical composition of 100 grams of the edible portion of fresh nance (Byrsonima crassifolia) fruit in the green-mature and mature stages and weight composition of the fruit Chemical composition

Green-mature

Mature

Moisture Total dry matter: – Ashes – Organic matter

83.99 g 16.01 g 0.70 g 15.30 g

83.04 g 16.96 g 0.74 g 15.22 g

Organic matter breakdown: – Crude protein – Ether extract (Fats) – Crude fiber – Nitrogen free extract of which reducing sugars constitute

0.92 g 1.59 g 2.26 g 10.54 g 7.45 g

0.89 g 2.23 g 2.33 g 10.77 g 8.86 g

Weight composition: Seed Pulp and peel

10.22% 89.78%

14.42% 85.58%

Source: Duarte and Vernon, 2002.

3.2

Fruit development and postharvest physiology

3.2.1 Fruit growth, development and maturation According to Duarte and Vernon (2002) this species needs cross pollination for adequate fruit set. These authors found that when using a mosquito net to cover the inflorescences almost no fruit set occurred (0.5–1.0%) whereas the percentage of fruit set in uncovered fruits was 40–46%. The fruit will take from five to six months from anthesis to ripening (Fig. 3.1). The fruit are initially green in color turning lighter as they mature and finally becoming yellow, although some types can be almost red, dark orange or green. The mature fruit will normally drop to the ground from where it is picked at harvest time. The day the fruit drops from the tree it cannot be eaten because it has

Fig. 3.1 Nance (Byrsonima crassifolia) fruit growth curve for weight (continuous line) and diameter (dotted line) at El Zamorano, Honduras (Duarte and Vernon, 2002).

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an astringent taste due to high concentration of tannins. This unpleasant taste will normally disappear next day and by that time the fruit will have a softer texture (this can be checked by pressing it between the fingers). The fruit can also be harvested several days before it drops naturally, as is described in the following section.

3.2.2 Respiration, ethylene production and ripening There is not much written information on this aspect. According to Velásquez de Klimo (2006), the fruit shows a climacteric rise in ethylene production during the third day of storage at 20 °C, while there is no defined pattern in carbon dioxide production. Yet, at the same time this author indicates that other workers claim that nance is not a climacteric fruit. However, there is no doubt that the fruit can be harvested as soon as it starts changing color to paler green or yellow or to the color of the variety. This fruit will ripen normally and can be eaten as soon as the calyx abscises from it and the fruit shows certain softness when pressed between the fingers. Further studies need to be done to define the behavior of this fruit that from the above information seems more likely to be climacteric.

3.3

Maturity and quality components and indices

As already mentioned, the fruit is normally considered mature when it drops naturally. No maturity indices has been developed other than color or fruit drop, which is the more commonly used index. There are no commercial orchards and therefore no standard varieties of nance exist. There is a broad classification of fruit by flavor as acid or sweet, sometimes by the ripe fruit color. The main quality criteria are size and degree of damage, either mechanical, from insects or from diseases. The spotlessly clean fruit are separated sometimes from the fruit that are damaged, contain larvae or show bruises. Insects can also attack the fruit and sometimes larvae are found inside. Aside from this there are no strict quality control measures, since nance is most frequently sold for making juices or pulp or desserts or alcoholic beverages, than for consumption as a raw fruit. Obviously the consumer prefers a spotless fruit but many times there is not much to choose from in the market.

3.4

Preharvest factors affecting quality

Damage by some fungal diseases and attack from insects that lay eggs that evolve into larvae can occur. Sometimes leaf cutting ants (Atta sp.) can be a problem, cutting and taking pieces of the fruit which normally will render the fruit useless.

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Postharvest biology and technology of tropical and subtropical fruits

Postharvest handling factors affecting quality

Mixing fruit of different sizes and maturity stages causes problems, as the softer fruits get squeezed by the less soft fruits and ooze their juices. There is a tendency to pack the fruits incompetently using inadequate packing material and containers that have excessive volumes. In many instances fruit arrives squashed at the market or supermarket due to excessive size of the packing container or its roughness.

3.6

Physiological disorders

No information is available on physiological disorders of nance.

3.7

Pathological disorders

Nance plant and fruit are both very tolerant and there are very few diseases that affect them. Sooty molds, though, that live on the honey dew (secretion) that certain sucking insects leave on the plant, can be problematic.

3.8

Insect pests and their control

According to Bayuelo-Jimenez (2008) there are some insects that attack nance trees, among them Macrospis festina which eats the fruits, and Oncideres dejean and Orthezia insignis which cut the branches.

3.9

Postharvest handling practices

Ideally the fruit should be picked from the tree just before it will drop. This is not practical and therefore it is recommended to harvest the fruits that are turning lighter green or to put a netting or canvas under the canopy so the fruit do not touch the ground when they drop. Fruits picked up from the ground are likely to have become moist and been attacked by insects like ants and others that will damage them. The fruits should be classified by size into at least three categories – small, medium and large. They should also be classified by softness and maturity stage as well as by appearance, separating fruit without blemishes from the others as well as those of different sizes or colors. Fruits of similar size and maturity stages should be packed together. Packing containers should be small, with a capacity of no more than five or six kilograms and with smooth and padded walls and bottoms. Storage temperatures should be around 9 to 13 °C as at these temperatures the fruit quality remains acceptable for 10 to 12 days. It is recommended that the fruit

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should not be left for more than 24 hours at room temperature. Keeping fruits under water is also mentioned as a storage technique (Morton, 1987).

3.10

Processing

The most common method of processing usually involves placing the fruit with some water in a blender at low speed to separate the pulp from the stones. This pulp can then be used to make juices. Another practice is boiling the fruit with sugar to make a jam. The seeds are strained afterwards. Sometimes the fruit is candied by boiling with a larger quantity of sugar so rather than producing syrup a sweet paste is left that surrounds the seed. Fruit with excellent appearance are processed in a light syrup and sold in supermarkets in glass jars. Various alcoholic products can be made with nance fruit. Ripe and blemish free fruits can be put in a jar after washing, some sugar added and the spaces filled with water. The jars are then left in the sun until alcoholic fermentation has taken place. The resulting product is a good tasting liquor that can be stored for years. Alternatively the fruit can be put in a jar and the spaces filled with boiled water before it is left for the internal sugars to ferment. This method takes longer. Another method is to fill the jar with fruit and sugar cane alcohol (aguardiente) instead of water. The jar is left for several months so that the alcohol penetrates the pulp and at the same time takes on the flavors and aromas of the ripe fruit. When freezing the fruit it is best to use the Individually Quick Freeze (IQF) system to avoid the formation of ice crystals in the fruit. If ice crystals form they damage the fruit′s internal structure, so it will look bad once it has thawed. The fruit should be kept at −18 °C for best results after prolonged storage.

3.11

Conclusion

Nance is probably among the five or six most popular fruits in countries like Guatemala, El Salvador, Honduras and Nicaragua and is fairly popular in Mexico, Panama and parts of Brazil. However, there is very little literature available on this crop. It is normally not cultivated in technically conducted plantings and its propagation is sexual resulting in high variability. An export market for the crop already exists, as the fruit is exported to the United States and Canada where it is an ethnic product for a particular population sector. This reinforces the need for more research on this crop in order to raise its level of production, quality and commercial importance. In all probability if selected plant materials are propagated asexually (which can be done very successfully), the plants properly cultivated, and the fruit handled and stored according to the latest technical information, nance could become an interesting species to grow in some areas, especially for the export market.

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Postharvest biology and technology of tropical and subtropical fruits

References

Barbeau G (1990), Frutas tropicales en Nicaragua, Dirección General de Técnicas Agropecuarias. Managua, Nicaragua, Editorial Ciencias Sociales. Bayuelo-Jimenez J (2008), The nance (Byrsonima crassifolia). In: Janick J and Paul R (eds). The Encyclopedia of Fruit and Nuts. Wallingford, UK, CAB International, pp 459–461. Donadio L C, Moro F V and Servidone A A (2002), Frutas Brasileiras. Jaboticabal, Sao Paulo, Brasil, Editora Novos Talentos, p 288. Duarte O and Vernon R (2002), Biología floral y reproductiva del nance (Byrsonima sp). Proc. Interamerican Soc. Trop. Hort. 46: 40–41. Morton J (1987), Fruits for Warm Climates. Greensboro, N.C., USA. Media Incorporated. Standley P C and Steyermark J A (1946), Flora de Guatemala. Fieldiana: Botany 24(5): 478–479. Velásquez de Klimo I (2006), Manejo pos cosecha del nance (Byrsonima crassifolia (L) HBK). Ministerio de Agricultura y Ganadería. San Salvador, El Salvador. IICA Frutales, Programa Nacional de Frutales. Williams L O (1981), The Useful Plants of Central America. Ceiba 24(1–2): 202–203.

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4 Noni (Morinda citrifolia L.) A. Carrillo-López, Autonomous University of Sinaloa, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico

Abstract: Noni (Morinda citrifolia L.) is the small tropical evergreen tree native to South-East Asia whose whole fruit, juice, seed, leaf, bark and root are used as sources of traditional medicines by Australian aboriginal, Pacific Island and South-East Asian communities. These plant parts have shown antioxidant, antimicrobial, anti-cancer and anti-inflammatory properties. Noni cultivation has spread extensively to regions such as Mexico, Central and South America, and in recent years its economic value has grown significantly worldwide due to assertions of its health benefits. The largest markets for noni products are North America, Europe, Japan, Mexico, Asia and Australia. It is sold mainly as juice, but the fruit is also often marketed in its fresh, unprocessed form in both formal and informal markets. Optimization of agricultural techniques, postharvest practices and processing technologies for noni are required. Postharvest handling information on the fruit is quite scarce. Key words: Morinda citrifolia, noni, postharvest, processing, postharvest handling, anticancer, anti-inflammation.

4.1

Introduction

4.1.1 Origin, botany, morphology and structure The noni (Morinda citrifolia), a small evergreen tree, is native to South East Asia (Indonesia to Australia) and is a member of the Rubiaceae family. Its fruit is known worldwide by many vernacular names including Indian mulberry, hog apple, mengkudu, pain killer, gogu atoni, great morinda, jo ban, mona and kesengel, but the most widely-used commercial name is noni (Wagner et al., 1999). The plant flowers and fruits all year round, producing a small, white, perfect flower (one that has both male and female organs). The fruit develops into an oval shape, reaching 4–10 cm in length and 3–4 cm in diameter (see Plate VII in the colour section between pages 238 and 239). When ripe the fruit has a rancid cheese odor, and therefore is also known as cheese fruit. It contains many seeds,

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which are similar in size and shape to apple seeds, but have a harder seed coat. Whereas, there have been many assertions of the health benefits of noni, no governments have yet approved any claims of its health benefits. However, the European Commission (2010) has recently authorized the placing on the market of puree and concentrate of Morinda citrifolia as a novel food ingredient. Previously, the European Commission did the same for leaves of Morinda citrifolia in 2008 (European Commission, 2008) and pasteurized noni juice in 2003 (European Commission, 2003). 4.1.2 Worldwide importance Morinda citrifolia cultivation has spread extensively to regions beyond its origin area: Mexico, Central and South America (Panama, Venezuela, Surinam). It is a source of traditional medicine in coastal Aboriginal communities in Cape York, the Pacific Islands and South East Asia, and in recent years has experienced significant economic growth worldwide due to assertions of its various health benefits. The largest markets for noni are North America, Europe, Japan, Mexico, Asia and Australia, with the worldwide market for these products estimated at US$400 million (McPherson et al., 2007). Some countries (e.g. Costa Rica and Cambodia), have increased cultivation of noni accordingly. Plate VIII in the colour section shows noni fruit in a popular market in Mexico. 4.1.3 Chemical composition Some of the physicochemical characteristics of noni fruit are as follows: water: 90%; pH: 3.72; dry matter: 9.87; total soluble solids: 8 °Brix; protein content: 2.5%; lipid content: 0.15%; glucose content: 11.97 g L−1; fructose: 8.27 g L−1; potassium: 3900 mg L−1; sodium: 214 mg L−1; magnesium: 14 mg L−1; calcium: 28 mg L−1; vitamin C: 155 mg 100 g−1 (Chunhieng 2003). The main components of the dry matter appear to be soluble solids, dietary fiber and proteins, and the main amino acids are aspartic acid, glutamic acid and isoleucine (Chunhieng et al., 2005). Minerals (mainly potassium, sulphur, calcium and phosphorus) account for 8.4% of the dry matter. Vitamins that have been reported in the noni fruit include ascorbic acid (24–158 mg 100 g−1 dry matter) (Morton, 1992; Shovic and Whistler, 2001), and provitamin A (Dixon et al., 1999). Altogether, more than 150 phytochemical compounds have been identified in the fruit and other parts of the noni plant. The major phytochemicals are phenolic compounds, organic acids and alkaloids (Wang and Su, 2001). Commonly reported phenolic compounds include antraquinones (damnacanthal, morindone and morindin), aucubin, asperuloside, and scopoletin (Wang and Su, 2001). Caproic and caprilic acids are the main organic acids (Dittmar, 1993). The principal alkaloid, at least according to Heinicke (1985) is xeronine, however this author reported no chemical characterization for the ‘alkaloid’ xeronine, nor has this subsequently been found and characterized in noni or other plant tissue by anyone else (McClatchey, 2002).

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Phenolic compounds have been found to be the major group of functional phytochemicals in noni juice. Damnacanthal (in root), scopoletin (plant), morindone (in root), alizarin (in root), aucubin (in plant), nordamnacanthal, rubiadin (in root), rubiadin-1-methyl ether (in root bark) and other anthraquinone glycosides have been identified (Morton, 1992; Dittmar, 1993; Dixon et al., 1999; Wang and Su, 2001). According to Farine et al. (1996), fifty-one compounds were abundant enough to be identified by gas chromatography-mass spectroscopy. The ripe fruit is characterized by a large amount of carboxylic acids, especially octanoic and hexanoic acids, but also alcohols (3-methyl-3-buten-1-ol), esters (methyl octanoate, methyl decanoate), ketones (2-heptanone), and lactones ((E)-6-dodeceno-Y-lactone) can be found (Farine et al., 1996). More recently, Pino et al. (2010) reported that ninety-six compounds were identified in noni fruit, out of which octanoic acid (about 70% of total extract) and hexanoic acid (about 8% of total extract) were found to be the major constituents. During fruit maturation and ripening, the concentrations of octanoic acid, decanoic acid and 2E-nonenal decreased, while concentration of some esters (methyl hexanoate, methyl octanoate, ethyl octanoate and methyl 4E-decenoate) increased (Pino et al., 2010). Two unsaturated esters, 3-methyl-3-buten-1-yl hexanoate and 3-methyl-3-buten-1-yl octanoate, were reported for the first time in noni fruit. Concentrations of these two constituents also significantly decreased during maturation and ripening (Pino et al., 2010). 4.1.4 Culinary uses, nutritional value and health benefits Despite its strong smell and bitter taste, the fruit is eaten either raw or cooked. South East Asians and Australian Aborigines consume the fruit raw with salt or cook it with curry. The seeds are also edible when roasted. The main use of Morinda citrifolia today, though, is in the form of a liquid tonic extracted from the fruit. An industry has developed around this fruit juice which is marketed as ‘Noni’ or ‘Noni juice’. The whole fruit of Morinda citrifolia, its juice, seeds, leaves, bark and root are recognized to possess medicinal properties and the Polynesians have been using the noni plant for food and medicinal purposes for more than 2000 years. The fruit is claimed to prevent and cure several diseases (Chan-Blanco et al., 2006; Hirazumi et al., 1994). Traditional uses of noni include the treatment of diarrhea, intestinal parasites, indigestion and stomach ulcers, diabetes, high blood pressure, headache, kidney and bladder tumors, fevers, inflamed and sore gums, sore throat with cough, toothache, arthritis, sprains and broken bones, cough, tuberculosis, asthma and respiratory afflictions, menstrual cramps, regulation of menstruation and prostate complaints, skin problems such as abscesses, boils, blemishes, wounds and infections (Macpherson et al., 2007). In particular, parts of the plant and its fruit are considered remedies for imbalances of the digestive, intestinal, respiratory and immune systems. The likely mode of action is stimulation of the immune system to fight bacterial, viral, parasitic and fungal infections and to prevent the formation and proliferation of tumors (Dixon et al., 1999).

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In recent years different parts of the noni plant have been the subject of medical research aimed at investigating noni’s effects on health. Some of these studies are discussed below. Anti-microbial effects Atkinson (1956) reported that noni inhibits the growth of certain bacteria, such as Staphylococcus aureus, Pseudomonas aeruginosa, Proteus morgaii, Bacillus subtilis, Escherichia coli, Helicobacter pylori, Salmonella and Shigella. It is claimed that the antimicrobial effect may be due to the presence of phenolic compounds such as acubin, L-asperuloside, alizarin, scopoletin and other anthraquinones. Duncan et al. (1998) also reported that the antioxidant scopoletin has an anti-microbial effect. Another study by Locher et al. (1995) showed that an acetonitrile extract of the dried fruit inhibited the growth of Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli and Streptococcus pyrogen. Saludes et al. (2002) found that ethanol and hexane extracts of noni have an anti-tubercular effect since they inhibit 89–95% the growth of Mycobacterium tuberculosis. The major components identified in the hexane extract were E-phytol, cycloartenol, stigmasterol, β-sitosterol, campesta-5,7,22-trien-3-b-ol, and the ketosteroids, stigmasta-4-en-3-one and stigmasta-4-22-dien-3-one. Other studies reported a significant antimicrobial effect on different strains of Salmonella, Shigella and E. coli (Bushnell et al., 1950; Dittmar, 1993). The antimicrobial effect in these studies was highly dependent on the stage of ripeness and processing. A greater effect was seen in ripe fruit that had not been dried. Anti-cancer properties Noni juice is a rich source of antioxidants (Wang et al., 2009) which are important in neutralizing ‘free radicals’ or particles that cause DNA damage that can lead to cancer. When mice were inoculated with Lewis lung carcinoma, those ingesting a daily dose of 15 mg of noni juice had an increase of 119% in life span (Hirazumi et al., 1994) and nine out of 22 mice with terminal cancer survived for more than 50 days. In addition, the ingestion of noni extract, combined with conventional chemotherapy in the treatment of mice with cancer, proved to increase their life spans (Hirazumi et al., 1994). Commercial noni juice has been shown to be able to prevent the formation of chemical carcinogen-DNA adducts (Wang and Su, 2001). Rats with artificially-induced cancer in specific organs were fed for one week with 10% noni juice in their drinking water. They showed reduced DNA-adduct formation, depending on sex and organ (Wang and Su, 2001). In addition, the antioxidant damnacanthal, an anthraquinone found in the plant’s root, has been characterized and has shown some important functional properties, mainly anti-carcinogenic attributes (Solomon, 1999). Anti-inflammatory and other effects Noni juice selectively inhibited COX enzyme activity in vitro and had a strong anti-inflammatory effect comparable to that of CELEBREX® and without side effects (Su et al., 2001). Kamiya et al. (2004) have demonstrated the effects of

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noni fruit on preventing arteriosclerosis, a disease related to the oxidation of low density lipoproteins (LDL). Methanol and ethyl acetate extracts from noni inhibited copper induced LDL oxidation by 88 and 96%, respectively, using the thiobarbituric acid reactive substance method. This beneficial effect could be due to the presence of lignans and phenylpropanoid dimers (Kamiya et al., 2004). Two clinical studies also reported relief of arthritis and diabetes due to noni consumption (Elkins, 1998; Solomon, 1999). Lastly, noni juice has a low glycemic index which helps balance blood sugar levels (Macpherson et al., 2007). The antioxidant scopoletin, a coumarin was also found to have analgesic properties as well as a significant ability to control serotonin levels in the body (Levland and Larson, 1979). Safety issue The suggested link between noni juice ingestion and liver toxicity has been refuted on the basis that it is not consistent with histopathology and clinical chemistry results of subchronic oral toxicity tests in animals as well as observed laboratory values of clinical safety studies (West et al., 2006). Furthermore, the opinion of the European Food Safety Authority (EFSA, 2006) through the scientific panel on dietetic products, nutrition and allergies, was that it is unlikely that consumption of noni juice, at the observed levels of intake, induces adverse human liver effects. There is no convincing evidence for a causal relationship between the acute hepatitis observed in the case studies reported by Stadlbauer et al. (2005), Millonig et al. (2005) or Yuce et al. (2006) and the consumption of noni juice. Conversely, liver protective effects of noni juice have been demonstrated by Jensen et al. (2006).

4.2

Fruit growth, development and maturation

In Hawaii, noni fruit are harvested year round, although there are seasonal trends in the amount of flowering and fruit production that may be affected or modified by the weather and by fertilizers and irrigation. Fruit production may diminish somewhat during the winter months in Hawaii (Nelson, 2003). It is possible to find fruits at different stages of maturity on the same plant at the same time (Chan-Blanco, 2006). In Hawaii, the flowers of Morinda citrifolia develop into mature fruits over a span of at least several weeks. However, there are no published scientific data on the precise time required for fruit growth and development from fruit set to maturation and ripening. The fruit is light green when unripe, becoming whitish yellow when ripe (hard white stage). When harvested at ‘hard white’ stage, in few days the fruit turns soft and translucent yellow (Janick and Paull, 2008). A personal experience with this fruit was as follows: the noni fruit was harvested from a small orchard in Culiacán México at the ‘hard white’ ripeness stage and became very soft, with translucent yellow skin and acquired a putrid smell in two days at about 30 °C. Fruit may be picked and used at any stage of development. Fruit with the appropriate level of maturity should be selected depending on its end use.

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Postharvest biology and technology of tropical and subtropical fruits Table 4.1 Skin color and firmness during noni fruit maturation and ripening Maturity stage

Color

Firmness

1 2 3 4 5

Dark green Green-yellow Pale yellow Pale yellow Translucent-grayish

Very hard Very hard Very hard Fairly hard Soft

Source: Chan-Blanco et al. (2006).

Table 4.2

Noni fruit physical characteristics

Fruit weight, g Length of fruit, cm Girth of fruit, cm Specific gravity, g mL−1 Recovery of juice (%) Pulp percentage Seed percentage

147.9 9.8 5.26 1.13 38.95–46.72 44.76–46.72 3.24–4.31

Adapted from Rethinam and Sivaraman, 2007.

The evolution of the color and firmness of fruits maturing and ripening on the tree is shown in Table 4.1. Some physical fruit characteristics of importance to noni fruit processors are shown in Table 4.2.

4.3

Preharvest conditions and postharvest handling factors affecting quality

Scientific publications about the effects of preharvest conditions and postharvest handling of noni fruit quality are scarce. At the preharvest stage, a high incidence of pathological infection such as sooty mold can reduce photosynthesis in the plant, resulting in poor plant growth and reduced fruit size and quality. Pathological disorders are treated in more detail in the following section. Singh et al. (2007) indicated that the shelf life of the fruit postharvest was up to 5–7 days in open conditions at room temperature of 25–30 °C and relative humidity of 70–75%. Mature fruit tend to change color from greenish yellow to creamy yellow from the third day onwards, whereas ripe fruit of yellowish green color, turn to white on the fifth day. Regarding weight, 12–15 g of loss in weight was found in mature fruits and about 16–18 g of loss in weight of ripe fruit. Optimum storage conditions and the effects of changing temperatures on fruit quality remain to be investigated.

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Pathological disorders

A very severe pathological problem called ‘black flag’ has been reported from the Hawaiian area (Nelson, 2004), which is caused by phytophtora species. Infection results in extensive blight of leaves, stem and fruit and green fruit of all ages are susceptible to infection. Fruit may be infected through the flowers, epidermis, or pedicel. More often, though, fruit infection occurs through the peduncle, which joins the fruit with the stem, and progresses from the base of the fruit to the fruit apex. The entire fruit and the adjacent stems turn dark brown or black. Rotten fruit may become desiccated (‘mummified’) when dry weather follows a black flag epidemic. The disease may be controlled with foliar applications of phosphorus acid fertilizers (Nelson, 2004). Nelson and Abad (2010) reported a new species of phytophtora causing black flag. They described how this taxon’s morphology does not match any of the valid 95 Phytophthora species described to date and proposed a name for this new species: Phytophtora morindae. Another pathological problem in noni is sooty mold, a black, superficial growth of a nonparasitic fungus that utilizes the sugary exudates produced by softbodied insects such as scales and aphids. Sooty mold can easily be wiped off leaves by hand or can be controlled by a soapy water spray (Nelson, 2001). A big threat to noni cultivation in the Pacific is root-knot disease caused by nematodes (Meloidogyne spp.). Attack by nematodes severely stunts plant growth and allows the root infection by opportunistic pathogens such as the fungus Sclerotium rolfsii (Janick and Paul, 2008). Root-knot is best controlled by avoiding infection in the seedlings in the nursery, using disease-free plantlets and avoiding the introduction of nematode-infected plants to a new field. Moderate irrigation is recommended.

4.5

Insect pests and their control

According to Nelson (2001), pests known to attack noni in Hawaii include aphids (Aphis gossypii), ants, scales (the green scale), mites (eriophyid mites), whiteflies (fringe guava whitefly), and slugs. Noni monocultures favor pest outbreaks; thus, the severity and frequency of pest attacks can be minimized by intercropping with other species of non-host plants. Pest outbreaks can also be prevented by the elimination of weeds that favor pests development and mites can be reduced by pruning affected leaves. According to Janick and Paul (2008) the most severe damage in Hawaii is associated with whiteflies, whereas in Micronesia the most problematic species is the leaf miner. In general, insect damage may be more severe in locations that are dry or have low rainfall.

4.6

Postharvest handling practices

4.6.1 Harvest operations Noni fruit are harvested by hand by picking individual fruit from the branches. After harvesting, the fruit ripens within a week at ambient temperature, and

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therefore because of its short storage life the fruit cannot currently be transported to distant places even within the same country. According to Singh et al. (2007), harvesting fruit with the pedicel helps to maintain quality postharvest and improve market acceptability. In this study, the highest level of spoilage was observed in fruit harvested without the pedicel. 4.6.2 Packinghouse practices Fruit are placed in baskets, bags or bins for transport to the processing facility. Noni fruit do not bruise or damage easily, so usually no special padded containers or other precautions are used to prevent significant fruit damage (Nelson, 2003). However, for commercialization purposes some fruits are wrapped together in small trays (Fig. 4.1). 4.6.3 Recommended storage and shipping conditions If harvested at the ‘hard white’ ripeness stage or earlier, exposure of noni fruit to direct sunlight or to warm temperatures immediately after harvest is not a significant concern. Noni fruit are usually not refrigerated after harvest (Nelson, 2003). However, because of the increased interest in noni products, it will become important to investigate the optimal handling practices so sale of the fresh fruit outside its area of cultivation becomes possible.

Fig. 4.1

Packaged noni fruit.

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Noni (Morinda citrifolia L.)

4.7

59

Processing

Most noni is consumed as juice (Dixon et al., 1999). Fruit for juice production are picked at their ‘hard white’ stage a few days before they turn whitish yellow, become soft and fall from the tree. The ‘hard white’ fruit should be washed before the flesh softens, then the fruit are held at ambient or room temperature for one to several days to ripen and soften before they are processed. The juice seeps out naturally from the pulp into juice-collection containers, but it can be extracted by squeezing the fruit with a press (Janick and Paull, 2008). If ripe fruit are allowed to sit for an extended period, they begin attracting unwanted fruit flies, rats and other insects or pests, so this should not be allowed to happen. According to Nelson (2003), in Hawaii, noni fruit juice and juice products are processed and prepared by a variety of methods. ‘Traditional’ juice is drip-extracted and then fermented/aged for at least two months. The ‘non-traditional’ method of juice extraction involves pressing or squeezing the juice from ripe fruits. Noni juice may be diluted, or bottled in its pure state. Some noni juices are pasteurized, but not all (Nelson, 2003). Noni juice concentrate can be produced by flash evaporation and the pulp of the fruit is also chopped, dehydrated and powdered for use in reconstituted noni juice products in the dietary supplement industry (Nelson, 2003). For powders or fresh-cut products, fruit can be processed before it fully ripens, as unripe fruit is easier to handle with some types of chopping and drying equipment.

4.8

Conclusions

The noni (Morinda citrifolia) plant, and especially its fruit, has been used for centuries in folk medicine. The most important compounds identified in noni fruit are phenolics (such as damnacanthal and scopoletin), organic acids (caproic and caprylic acid), vitamins (ascorbic acid and provitamin A), amino acids (such as aspartic acid), and minerals. In vitro research and some animal experiments have shown that noni has antimicrobial, anti-cancer, antioxidant, anti-inflammatory, analgesic and cardiovascular activity. Consumption of noni juice is currently high, not only in the producing countries, but also in the USA, Japan and Europe, and this market interest suggests a promising future. However, to determine the real potential of this fruit, more studies are needed to identify its nutritional and functional compounds and the technological processes required to preserve them. Furthermore, studies on the postharvest handling of the fresh fruit are also still needed, due to the necessity of transporting the fruit far from the local production areas for processing or sale. Postharvest physiology (respiration rate, ethylene production rate and ethylene sensitivity), optimal ripening and storage temperatures, and other factors that affect fruit quality after harvest should be investigated.

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4.9

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References

Atkinson N (1956), Antibacterial substances from flowering plants. 3. Antibacterial activity of dried Australian plants by rapid direct plate test. Australian Journal of Experimental Biology 34:17–26. Bushnell OA, Fukuda M and Makinodian T (1950), The antibacterial properties of some plants found in Hawaii. Pacific Science 4:167–183. Chan-Blanco Y, Vaillant F, Perez AM, Reynes M, Brillouet J-M and Brat P (2006), The noni fruit (Morinda citrifolia L.): A review of agricultural research, nutritional and therapeutic properties. Journal of Food Composition and Analysis 19(6–7):645–654. Chunhieng MT (2003), Développement de nouveaux aliments santé tropicale application á la noix du Brésil Bertholettia excelsa et au fruit de Cambodge Morinda citrifolia. PhD thesis, INPL, France. Chunhieng T, Hay L and Montet D (2005), Detailed study of the juice composition of noni (Morinda citrifolia) fruits from Cambodia. Fruits (Paris) 60(1):13–24. Dittmar A (1993), Morinda citrifolia L. – Use in Indigenous Samoan medicine. Journal of Herbs, Spices and Medicinal Plants 1(3):77–92. Dixon AR, McMillen H and Etkin NL (1999), Ferment this: The transformation of Noni, a traditional Polynesian medicine (Morinda citrifolia, Rubiaceae). Economic Botany 53(1):51–68. Duncan SH, Flint HJ and Stewart CS (1998), Inhibitory activity of gut bacteria against Escherichia coli O157 mediated by dietary plant metabolites. FEMS Microbiology Letters 164: 258–283. EFSA (2006). European Food Safety Authority. Opinion on a request from the Commission related to the safety of noni juice (Juice of the fruit of morinda citrifolia). EFSA Journal 376:1–12. Available from: http://www.efsa.europa.eu/en/scdocs/scdoc/376.htm [Accessed 29 July 2010]. Elkins R (1998), Hawaiian Noni (Morinda citrifolia) Prize Herb of Hawaii and the South Pacific. Woodland Publishing, Utah. European Commission (2003), Commision decision of 5 June 2003 authorising the placing in the market of noni juice (juice of the fruit of Morinda citrifolia) as a novel food ingredient under regulation (EC) No 258/97 of the European Parliament and of the council. In Official Journal of the European Union, 2003, 001. European Commission (2008), Commision decision of 15 December 2008 authorising the placing in the market of leaves of Morinda citrifolia as a novel food ingredient under regulation (EC) No 258/97 of the European Parliament and of the council. In Official Journal of the European Union, 2008. European Commission (2010), Commision decision of 21 April 2010 authorising the placing in the market of puree and concentrate of the fruits of Morinda citrifolia as a novel food ingredient under regulation (EC) No 258/97 of the European Parliament and of the council. In Official Journal of the European Union, 2010. L102/49. Available from: http://ec.europa.eu/food/food/biotechnology/novelfood/index_en.htm [Accessed 29 July 2010]. Farine, JP, Legal L, Moreteau, B, Le Quere, JL (1996), Volatile components of ripe fruits of Morinda citrifolia and their effects on Drosophila. Phytochemistry 41: 433–438. Heinicke RM (1985), The pharmacologically active ingredient of Noni. Pacific Tropical Botanical Garden Bulletin 15:10–14. Hirazumi A, Furusawa E, Chou SC and Hokama Y (1994), Anticancer activity of Morinda citrifolia (noni) on intraperitoneally implanted Lewis lung carcinoma in syngenic mice. Proceedings of the Western Pharmacological Society 37:145–146. Janick J and Paull RE (2008), The Encyclopedia of Fruit & Nuts. CAB International, London UK. pp. 954. ISBN 9780851996387. Jensen CJ, Westendorf J, Wang MY and Wadsworth, DP (2006). Noni juice protect the liver. European Journal of Gastroenterology & Hepatology 18:575–577.

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Kamiya K, Tanaka Y, Endang H, Umar M and Satake T (2004), Chemical constituents of Morinda citrifolia fruits inhibit copper-induced low-density lipoprotein oxidation. Journal of Agricultural and Food Chemistry 52:5843–5848. Levland O and Larson HO (1979), Some chemical constituents of Morinda citrifolia. Planta Medica 36(2):186–187. Locher CP, Burch MT, Mower HF, Berestecky J, Davis H, et al. (1995), Anti-microbial activity and anti-complement activity of extracts obtained from selected Hawaiian medicinal plants. Journal of Ethnopharmacology 49:23–32. McClatchey W (2002), From Polynesian healers to health food stores: changing perspectives of Morinda citrifolia (Rubiaceae). Integrative Cancer Therapies 1(2): 110–120. Macpherson H, Daniells J, Wedding B and Davis C (2007), The potential for a new value adding industry for noni tropical fruit producers. Australian Government Rural Industries Research and Development Corporation. Publication No 07/132. p 46. Millonig G, Stadlman S and Vogel W (2005). Herbal hepatoxicity: acute hepatitis caused by a Noni preparation (Morinda citrifolia). European Journal of Gastroenterol & Hepatology 17:445–447. Morton JF (1992), The ocean-going noni or Indian mulberry (Morinda citrifolia, Rubiaceae) and some of its ‘colorful’ relatives. Economic Botany 46(3):241–256. Nelson SC (2001), Noni cultivation in Hawaii. Fruit and Nuts 4:1–4. Nelson SC (2003), Noni cultivation and production in Hawaii. In: Proceedings of the 2002 Hawaii Noni Conference. University of Hawaii at Nanoa, College of Tropical Agriculture and Human Resources, Hawaii. Nelson SC (2004), Black flag of noni (Morinda citrifolia) caused by a Phytophtora species. Honolulu (HI), University of Hawaii. p. 4 (Plant Disease; PD-19). Nelson SC and Abad ZG (2010), Phytophthora morindae, a new species causing black flag disease on noni (Morinda citrifolia L) in Hawaii. Mycologia 102(1):122–134. Pino JA, Márquez E, Quijano CE and Castro D (2010), Volatile compounds in noni (Morinda citrifolia L.) at two ripening stages. Ciencia e Tecnologia de Alimentos 30(1):183–187. Rethinam P and Sivaraman K (2007), Noni (Morinda citrifolia L.) the miracle fruit – a holistic review. International Journal of Noni Research 2(1–2):4–37. Saludes JP, Garson MJ, Franzblau SG and Aguinaldo AM (2002), Antitubercular constituents from the hexane fraction of Morinda citrifolia L. (Rubiaceae). Phytotherapic Research 16:683–685. Shovic AC and Whistler WA (2001), Food sources of provitamin A and vitamin C in the American Pacific. Tropical Science 41:199–202. Singh DR, Srivastava RC, Subhash Chand and Abhay Kumar (2007), Morinda citrifolia L. – An evergreen plant for diversification in commercial horticulture. International Journal of Noni Research 2(1–2): 45–61. Solomon N (1999), The Noni Phenomenon. Discover the powerful tropical healer that fights cancer, lowers high blood pressure and relieves chronic pain. Direct Source Publishing; ISBN: 1887938877. Stadlbauer V, Fickert P, Lackner C, Schmerlaib J, Krisper P, et al. (2005). Hepatotoxicity of Noni juice: Report of two cases. World Journal of Gastroenterology 11: 4758–4760. Su C, Wang MY, Nowicki D, Jensen J and Anderson G (2001), Selective COX-2 inhibition of Morinda citrifolia (Noni) in vitro. In: Proceedings of the Eicosanoids and other bioactive lipids in cancer, inflammation and related disease. The 7th Annual Conference, 14–17 October 2001, Loews Vanderbilt Plaza, Nashville, Tennessee, USA. Wagner WL, Herbst DH and Sohmer, SH (1999), Manual of Flowering Plants of Hawai’i (Revised Edition); University of Hawai’i Press. Wang MY, Lutfiyya MN, Weidenbacher-Hoper V, Anderson G, Su CX and West B J (2009), Antioxidant activity of noni juice in heavy smokers. Chemistry Central Journal 3(13):1–5.

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Wang MY and Su C (2001), Cancer preventive effect of Morinda citrifolia (Noni). Annals of the NY Academy of Science 952:161–168. West BJ, Jensen CJ, Westendorf J and White LD (2006), A safety review of noni fruit juice. Journal of Food Science 71:R100–R106. Yuce B, Gulberg V, Diebold J and Gerbes AL (2006). Hepatitis induced by noni juice from Morinda citrifolia: a rare cause of hepatotoxicity or the tip of the iceberg? Digestion 73:167–170.

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5 Olive (Olea europaea L.) C. H. Crisosto and L. Ferguson, University of California, USA and G. Nanos, University of Thessaly, Greece

Abstract: Olives (Olea europaea L.) are extensively cultivated around the world today in proper climates apart from the Mediterranean region. Olives must be properly harvested, handled, processed and stored for successful high quality table olives or oil production. Most of the world table olives are processed as Spanish-style green olives and California-style black-ripe olives, but Greek-style naturally ripe olives, stuffed olives and many other types and forms of olive fruit foodstuffs are marketed around the world. Most olives are used for olive oil extraction, which is produced and consumed, not only in the Mediterranean basin, but also all over the world. Key words: Olea europaea, curing, pickled, canning, olive packed styles, chilling injury.

5.1

Introduction

5.1.1 Origin, botany, morphology and structure A member of the Oleaceae family (Olea europaea L.), is a small tree native to the eastern part of the Mediterranean region. The ancient Egyptians, Greeks, Romans and other Mediterranean nations cultivated olives for their oil and fruit. The olive is a drupe, botanically similar to other stone fruits. It consists of the carpel with the wall of the ovary developing into both fleshy and dry portions; the skin (exocarp), which is free of hairs, and contains stomata; and the pit (endocarp) enclosing the seed. The fleshy mesocarp, from which edible oil is also extracted with physical methods, is the edible portion of the olive after processing. When processed, the exocarp is also eaten. Fruit shape, size and pit size and surface morphology vary greatly among cultivars. 5.1.2 Worldwide importance and economic value Olives are one of the most extensively cultivated and fast expanding fruit crops in the world. The area under olive cultivation tripled from 2 600 000 to 8 500 000

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Eleven largest olive producing countries

Rank

Country/region

Production (in tons)

Cultivated area (in hectares)

— 1 2 3 4 5 6 7 8 9 10 11

World Spain Italy Greece Turkey Syria Tunisia Morocco Egypt Algeria Portugal Lebanon

17 317 089 6 160 100 3 149 830 2 300 000 1 800 000 998 988 500 000 470 000 318 339 300 000 280 000 275 000

8 597 064 2 400 000 1 140 685 765 000 594 000 498 981 1 500 000 550 000 49 888 178 000 430 000 250 000

Source: http://www.internationaloliveoil.org

hectares between 1960 and 2004. The ten largest producing countries, according to the Food and Agriculture Organization, are all located in the Mediterranean region and produce 95% of the world’s olives (Table 5.1). Thus, olives are one of the few crops with such major economic importance for the region. In the Mediterranean region including southern Europe, northern Africa and the Middle East, olives and olive oil have been common ingredients of everyday foods for many centuries. Much lower consumption of olive products is found around the world, but due to the positive effects on human health, olive products are highly appreciated today in the markets worldwide. Commercial olive production is today a multimillion dollar business in California, Australia and other southern hemisphere countries. Olive oil is the major commercial product from olives including all kinds of specialty olive oils (from certain cultivars or blends, locations and growing methods), followed by table olives and their products. Only a few raw olives are marketed, usually locally for home curing. 5.1.3 Culinary uses, nutritional value and health benefits Table olives are prepared from sound, clean, and sufficiently mature fruit classified by stage of ripeness and the processing method used. Fresh harvested olive has a bitter component (oleuropein), a low sugar content (2.6–6%) compared with other drupes (12% or more) and a high oil content (12–35%) depending on the time of year, production method, location and cultivar. These characteristics make it a fruit that (almost always) cannot be consumed directly from the tree and it has to undergo a series of processes that differ considerably from region to region, and depending on variety. The bitterness is generally removed by treatment (curing) with one of the following: dilute base of sodium or potassium hydroxide (lye), salt and water (brine), dry salt or repeatedly rinsing the fruit in water at room temperature prior to canning or packing in brine solution.

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Spanish-style green olive is a major processing method around the Mediterranean region and highly consumed. Most olives grown in California and an appreciable amount of fruit around the world are processed into California-style black-ripe for canning. These fruit are mainly used for salads, pizza, and even finger food. Olives can be sold in various sizes, whole, pitted, chopped, sliced, stuffed or as paste. After curing to remove bitterness, the olives are conserved or packed into brine and often some edible acid in small quantities. Lactic or acetic acid in the form of vinegar may be added to acidify the solution and prohibit further fermentation during storage. Various other methods of olive processing are used around the world. Olive oil is extracted with physical methods from olives after washing, crushing, shaking and centrifuging. The olive oil is stored, packed and marketed around the world for use as raw oil or for cooking. One serving of olives has only 2.5 grams of fat, which is only 3% of the total suggested fat intake per day. Olives contain 12–35% olive oil with the table olive cultivars usually containing less oil than the small-fruited cultivars for oil production. The fatty acid content of olive oils varies by cultivar, maturity, cultivation practices and growing area. Generally, based on the Committee of Codex Alimentarius, they are as follows: stearic acid (18:0), 0.5 to 5%; oleic (18:1), 56 to 83%; linoleic (18:2), 3.5 to 20%; linolenic (18:3), 0.1 to 1.5%; palmitic (16:0), 7.5 to 20%; palmitoleic (16:1), 0.3 to 3.5%; arachidic (20:0), 55% also increased the percentage of edible flesh to more than 60%. Fruit with < 55% skin yellowing showed more wound-induced respiration and ethylene production due to slicing and deseeding and fully ripe fruit were easily bruised and difficult to handle. Therefore, selecting fruit with 55–80% yellow skin, which ensures > 50% edible flesh recovery, has been recommended for production of fresh-cut papaya (Paull and Chen, 1997). Tissue softening in fresh-cut papaya is primarily due to changes in cell wall composition induced by the activities of various hydrolytic enzymes and stressrelated proteins. Wounding of 60–70% yellow fruit used to make fresh-cut product enhanced the activities of various enzymes such as polygalacturonase, α-galactosidase, β-galactosidase, lipoxygenase, phospholipase D, and ACC synthase and ACC oxidase within 24 h, and levels remained significantly higher compared with those in intact fruit during 8 days storage at 5 °C (Karakurt and Huber, 2003). The total amount of pectin in fresh-cut papaya also declined, increased in solubility and exhibited depolymerization. In addition, this study confirmed that tissue softening was due to the physiological and biochemical alterations in the cell wall and membranes rather than to microbial activity. Gene expression analysis of the fresh-cut papaya has also revealed that wounding induces the expression of proteins involved in membrane degradation, free radical generation, and enzymes involved in stress responses (Karakurt and Huber, 2007). It has been suggested that tissue softening in fresh-cut papaya can be delayed by treatment of 70–80% ripe fruit with 1-MCP (2.5 μL L−1 for 12 h) before slicing

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(Ergun et al., 2006). Softening in fresh-cut product from 1-MCP-treated fruit was significantly delayed during 6–10 days storage at 5 °C. The slices from 1-MCP treated fruit were acceptable to the sensory panel for six days while those from control fruit could only be stored for 2–3 days. The potential shelf life of fresh-cut ‘Maradol’ papaya has been suggested to be 2, 6 and 10 days at storage temperatures of 20, 10 and 5 °C, respectively. The degree of tissue softening and weight loss were also lower at 5 °C compared to 10 or 20 °C (Rivera-López et al., 2005). Storage of fresh-cut papaya at 5 °C also helped to prevent losses of soluble solids, ascorbic acid, β-carotene, and antioxidant capacity. This study also showed that slices were a better shape for fresh-cut products than cubes as the latter presented higher weight loss, lower SSC and lower overall quality. Another study on the comparison of cut shapes showed that papaya flesh cut into spheres (1.55 cm radius) showed lower weight loss, firmer texture, higher SSC and ascorbic acid and lower microbial count compared to the cubes (1.4 cm side) during 10 days storage at 4 °C (Argañosa et al., 2008). Furthermore, edible coatings have great potential to reduce problems of weight and textural losses in fresh-cut products, increasing their shelf life. The application of alginate- (2 % w/v) or gellan-based (0.5 % w/v) coating formulations containing 1% ascorbic acid on fresh-cut papaya reduced weight loss through improved water vapour resistance and delayed tissue softening during eight days storage at 4 °C (Tapia et al., 2008). González-Aguilar et al. (2009) reported that a medium molecular weight chitosan coating (0.02 g mL−1) maintained the quality of fresh-cut papaya in terms of higher colour values (L* and b*) and firmness. It showed antimicrobial activity and suppressed plate counts of mesophiles, moulds and yeasts during 14 days of storage at 5 °C. To summarize, the huge research interest in fresh-cut products has led to the development of techniques that involve minimum use of synthetic food additives which result in better retention of fruit quality. Both technological developments and consumer preferences indicate great scope for expansion of the fresh-cut papaya industry. 6.10.2 Other processed products Ripe papaya fruit can be processed into a number of other products such as pure juice, blended beverages, jam, jelly, dehydrated, fruit bars, candy, intermediate moisture and frozen products. Purée is the major intermediate product of papaya. It is further processed into products like juice, nectar, jam, jelly and leather. The slices and chunks of semi-ripe fruit can also be canned.

6.11

Conclusions

Papaya fruit is a rich source of vitamins, minerals and dietary antioxidants. The mature unripe and ripe fruit including seeds have been used in traditional medicine since ancient times. There is a great demand for papaya fruit in the fresh market and processing industry. A consistent supply of high quality fruit to the consumers

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and processors is a great challenge for papaya industry around the world. The tropical environmental conditions, where the papayas are grown, are congenial for the development of various diseases and insect-pests, and for promoting postharvest losses in fruit. The lack of cold chain, proper postharvest handling facilities, and limited market access due to phytosanitary requirements could be some of the reasons for the small share of major papaya producing countries in the world trade. Harvest maturity in papaya is a critical factor that determines fruit quality, shelf life, storage/shipping potential at low temperature, and susceptibility to mechanical injuries and diseases. Harvesting at colour break stage (10–12% yellow) is a commercial practice to ensure better postharvest life and long-distance shipping of fruit. The fruit harvested before optimum maturity fail to develop good eating quality. The delayed harvesting (>25% yellow) improves fruit quality, but limits shelf life and increases susceptibility to fruit-fly attack. The harvest maturity should therefore be determined by considering all these factors. Fruit harvested at colour break stage can be stored for 2–3 weeks at 7–13 °C temperature and 90–95% relative humidity. Fruit at advanced stages of ripeness are more tolerant to chilling conditions compared to less mature ones. The delicate nature of fruit skin predisposes it to mechanical injuries during harvest and postharvest handling operations, resulting in increased susceptibility of fruit to rots caused by wound pathogens. The marketability of fruit can be significantly increased by proper care to avoid the mechanical injuries and weight loss. MAP of papaya fruit with very low permeability films is beneficial to retard weight loss, fruit ripening and alleviate chilling injury during cold storage. The benefits associated with blocking of ethylene action by 1-MCP can be obtained only if the fruit are treated at >25% skin yellowing stage. The possibility of integration of 1-MCP into the current papaya handling protocol is limited because fruit treated at colour break stage fail to soften and produce ‘rubbery’ texture. However, the exposure of quarter- to half-ripe fruit to 1-MCP can delay the fruit softening and provide some benefits at the retail end. The phytosanitary treatments such as vapour heat, forced hot air and irradiation have been adopted commercially for fruit to be exported to countries such as the U.S.A. (mainland), Japan, Australia and New Zealand. The response of papaya fruit to these treatments varies greatly due to a number of factors including fruit maturity and growing conditions. The thermal treatments have been shown to cause some damage to fruit quality; while irradiation has been proven to be a safe technology without adverse effects on fruit quality. The postharvest diseases such as anthracnose, Rhizopus rot and stem-end rot are responsible for huge economic losses in fruit. The incidence and severity of these diseases can be reduced by integrated management practices such as orchard hygiene, preharvest and postharvest fungicide applications, packinghouse sanitation, heat treatments, and use of GRAS compounds alone or in combination with biocontrol agents. There is a great demand for fruit in the fresh-cut and processing industries. The fruit at 75% ripe stage are the most suitable for fresh-cut products, which can be safely handled at 5 °C for 5–10 days. The ‘tissue-softening’ is commonly a limiting

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factor in the stability of the fresh-cut papaya. This problem can be minimized by treatment of fruit with 1-MCP before cutting. The fruit can also be processed into a number of products such as puree, juice, jam, jelly, fruit bars, etc. The demand for healthy and nutritious fruits and their products is increasing as the consumers are adopting a healthy lifestyle. These trends present a positive outlook for the papaya industry in the near future.

6.12

References

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7 Passion fruit (Passiflora edulis Sim.) W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain and G. Fischer, National University of Colombia, Colombia

Abstract: The species Passiflora edulis (sour passion fruit), is native from Brazil and is known in two forms, the purple and the yellow passion fruit. It is a climacteric fruit that quickly respires and produces a high amount of ethylene after harvest leading to a shorter shelf life for storage and transportation. The main quality issue is shrivelling due to water loss which affects consumer purchase decisions. Skin colour can be used as a maturity index for both the purple and the yellow form. For purple passion fruit storage at 4–5 °C is optimal whereas for yellow passion fruit a higher temperature of 10 °C is recommended. Both should be stored under high relative humidity to prevent water loss and shrivelling. Key words: Passiflora edulis, passion fruit, postharvest, processing, juice.

7.1

Introduction

7.1.1 Origin, botany, morphology and structure Sour passion fruit (Passiflora edulis Sim.) is a perennial vine of the Passifloraceae family (Rodriguez-Amaya, 2003). The Passifloraceae family consists of 18 genera one of which is the Passiflora genus with 530 species of which 50–60 are edible. The highest genetic diversity in Passifloraceae species is found in Colombia, where 167 species have been found, of which 165 were native, followed by Brazil (127 species) and Ecuador (90). This confirms the Andean area to be the birthplace of the genus (Ocampo Pérez et al., 2007). The species P. edulis (sour passion fruit) in particular however, is native from Brazil and is the species that dominates in the commercial orchards (Bernacci et al., 2008). Within this species, two distinct forms can be distinguished, the purple (often referred to as P. edulis f. edulis), and the yellow (mostly referred to as P. edulis f. flavicarpa Deg.). However, officially only P. edulis is accepted and P. edulis ‘Flavicarpa’ is considered a cultivar (Bernacci et al., 2008). Both have a similar round shape with

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a leathery skin containing aromatic juicy pulp with small seeds. However, besides the difference in colour they also differ in certain other properties as will be discussed later on. The purple passion fruit is mainly cultivated in Africa and Australasia and the yellow passion fruit in South America. General names for both in Spanish are granadilla, parcha, maracuyá (mainly used for the yellow), gulupa (mainly used for the purple); in Portuguese, maracuja peroba, maracujazeiro; in French, grenadille, or couzou, adding the colour to distinguish between the yellow and purple form. The vine is woody and perennial with shallow roots and climbs with the aid of tendrils. The vines can be supported by trellises (commercial plantations) or by wires in small domestic farms (Rodriguez-Amaya, 2003) or garden walls in gardens. It can grow very fast (4.5–6 m per year) but has a relatively short life (3 to 6 years) (Morton, 1987; Rodriguez-Amaya, 2003). The leaves are evergreen, alternate and deeply three-lobed when mature. They are 7.5–20 cm long, glossy green on the upper surface, paler and dull beneath. Leaves, young stems and tendrils, especially those of the yellow form are tinged with red or purple. The plant generally begins to bear fruit in one to three years, but in Colombia purple passion fruit already starts to produce after 9–10 months. A single, bisexual flower forms at the nodes of the new growth at the same spot as the tendrils. The flower is 5–7.5 cm across and surrounded by three large, leaf like bracts and has five greenish-white sepals and five white petals (Morton, 1987; RodriguezAmaya, 2003). At the apex of the androgynophore, each flower has a central prominent style which branches out into three stigma and situated below five stamens with large anthers, making self-pollination difficult (Rodriguez-Amaya, 2003). From the basis of the androgynophore, many slender straight rays, white at the tip and purple at the base, form a corona or ‘crown’, which is probably the most recognizable feature of the flower. The fruit are nearly round or ovoid, 35 (purple) to 80 (yellow) grams on average, 4–7.5 cm in diameter with a smooth, leathery rind ranging in hue from dark-purple with faint, fine white specks, to light-yellow or pumpkin colour (Morton, 1987). The rind is 3 mm thick, wrinkles when the fruit is ripe (more in the purple than the yellow form) and adheres to a 6 mm thick white pith (Morton, 1987; Rodriguez-Amaya, 2003). Numerous (up to 250) small, hard, edible, black (purple fruit) or dark brown (yellow fruit) seeds are embedded in double-walled, membranous sacs filled with yellow-orange, pulpy juice in a cavity (Morton, 1987). The pulp has an intense fragrance and has an appealing, musky, guava-like, sub-acid to acid flavour (Morton, 1987; Rodriguez-Amaya, 2003). The purple passion fruit is subtropical and will grow and produce best at elevations of 650–2000 m. However, in Colombia, the commercial production of purple passion fruit can be found between 1400 and 2200 m above sea level (Fischer et al., 2009) and in Kenya cultivation is found up to 2500 m (Ulmer and MacDougal, 2004). The yellow passion fruit is tropical and prefers lower elevations (0–1000 m) but commercial production can be found in Colombia between 0 and 1300 m above sea level (Fischer et al., 2009). With respect to the

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production at higher altitudes, the temperature and radiance seem to have an important effect on the timing of production. However, in orchard without irrigation, water deficits also play a role (Menzel and Simpson, 1994). A temperature between 21 and 32 °C is best for development of the plant with the optimum being 26.5 °C (Rodriguez-Amaya, 2003). Depending on the region the annual rainfall should be between 600 mm (Northern Transvaal with high relative humidity (RH)) and 2500 mm (India) (Morton, 1987) and this needs to be well distributed with heavy rainfall during flowering problematic for pollination; and irrigation recommended during the dry periods (Rodriguez-Amaya, 2003). They need protection from wind and frost, although they have been known to recover from frost damage after drastic pruning (Morton, 1987). The plant is not very demanding when it comes to soil type but prefers light to heavy sandy loams (Morley-Bunker, 1999) with sufficient organic matter, few salts, and a pH in the range of 5.0 to 7.5 (Morton, 1987). Good drainage is necessary to avoid water logging and collar rot (Nakasone and Paull, 1998) but enough water needs to be available during flowering and fruiting. Since the vines are shallow-rooted they need protection which can be provided with organic mulch. 7.1.2 Worldwide importance and economic value Production of passion fruit occurs in South America, Africa, India, many countries of South-east Asia (particularly Indonesia), and the South Pacific, including Hawaii, Australia and New Zealand (Morley-Bunker, 1999). Previously, the countries covering more than 80–90% of the world production were Hawaii, Fiji, Australia, Kenya, South Africa, Papua-New Guinea and New Zealand; however, in the last two decades the production centre has shifted back to the original habitat of the plant, the Latin-American continent. The main producers for purple passion fruit are now Brazil, Ecuador and Peru, and for the yellow form, Brazil, Ecuador, Peru, Venezuela, Costa Rica, Kenya, Zimbabwe, Thailand, Malaysia and Indonesia (Isaacs, 2009). The biggest passion fruit producer in the world is Brazil where the purple form is preferred for fresh consumption and the yellow for juicing in large-scale juice extraction plants. In 2007, 664 286 ton were produced on 47 032 ha (IBRAF, 2007), mainly yellow passion fruit. Ecuador has also consolidated itself as the main juice exporter (18 000 ton in 2008) in a market strongly influenced by the seasonality of the production resulting in problems of over production and scarcity (Isaacs, 2009). Another considerable problem is the variability of the price for fresh passion fruit. In good years (2004 and 2007), prices reach above $2.5 per kg for yellow passion fruit or even $4.5 (2005), but in contrast in lesser years (2000) prices drop to $1.4 per kg. The main clients for passion fruit in Europe are Germany, Belgium, Luxemburg and the Netherlands (Isaacs, 2009). In Australia, the purple passion fruit was flourishing up to 1943 when Fusarium caused massive wilting resulting in the adaptation of yellow passion fruit as a rootstock for the production of purple passion fruit. In New Zealand, similar

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problems arose but today, mostly in the Bay of Plenty region a profitable purple passion fruit industry exporting fruit and juice has developed. After recurring disease and pest problems on larger plantations, currently commercial culture of purple passion fruit can be found in Kenya on small and isolated plantings which can be better controlled. South Africa has successfully been producing purple passion fruit since the beginning of the century without serious problems. Purple passion fruit has been produced in India for many years, while the yellow form was only introduced a few decades ago. The latter was soon preferred for its more pronounced flavour and heavier and more regular crops (Morton, 1987). In Hawaii, a yellow passion fruit industry is firmly established and Fiji has a small juice-processing industry. 7.1.3 Cultivars and genetic variability Discussion has been ongoing as to whether the purple and yellow fruit were different forms, P. edulis forma edulis (purple) and P. edulis forma flavicarpa (yellow), but at taxonomic level, the use of the name P. edulis Sim. for either colour of sour passion fruit is indicated (Bernacci et al., 2008). There are a considerable amount of cultivars available but the specification of which cultivar is used is hardly ever given. A selection of available purple cultivars in Australasian and American markets include Australian Purple or Nelly Kelly, Black Beauty, Black Knight, Edgehill, Frederick, Kahuna, Paul Ecke, Purple Giant, Purple Possum, Red Rover. In the yellow range we find: Brazilian Golden, Golden Giant, Hawaiiana, McCain, Panama Gold, ‘Noel’s Special, Sweet Sunrise. The Brazilian cultivar BRS Ouro Vermelho produces both purple and yellow fruit. In Brazil a substantial amount of breeding work is being done to improve production and quality of the fruit. For the purple passion fruit attention has gone to Roxinho-Miúdo, Paulista and Maracujá-Maçã (Meletti et al., 2005). In the yellow range, IAC-273 and IAC-277 are gaining importance for fresh consumption with the main benefit in increased productivity with an average yield of 35–45 ton ha−1 whereas the average in Brazil so far is 10–15 ton ha−1. For the juice industry, IAC-275 was introduced, having a thin rind, a totally filled internal cavity, a higher soluble solids content (SSC), more vitamin C and a yield of more than 45 ton ha−1. This cultivar is now produced in six states of Brazil, as well as in Colombia and Venezuela (Pommer and Barbosa, 2009). 7.1.4 Culinary uses, nutritional value and health benefits The purple passion fruit is typically consumed fresh because it is sweeter, while the yellow passion fruit is used for processing due to its higher juice yield. Fresh passion fruit is eaten by cutting it in two and scooping out the pulp with a spoon. The pulp is also used in fruit salads, mousse, desserts, ice cream, and yoghurt or as a topping, with or without addition of sugar. After removing the seeds and homogenizing, it is also used to make jam and sauce which is then used in desserts as flavouring for cakes, and in icing. The juice is used pure or for preparation of

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cocktails and is used in the processing industry to make juice blends. Cooking the juice with sugar makes thick passion fruit-flavoured syrup. The juicy pulp has high contents of potassium and vitamins A, B6, C and E (see Table 7.1) and carotenoids (Pruthi, 1963). In yellow passion fruit, 13 carotenoids have been identified (Mercadante et al., 1998), with ζ-carotene (1.26–12.86 μg g−1 FW) and β-carotene (2.39–13.35 μg g−1 FW) the main carotenoids available (Silva and Mercadante, 2002). Additionally, in yellow passion fruit juice substantial levels of polyphenols (435 mg l−1) have been reported (Mercadante et al., 1998). The main anthocyanin found is pelargonidin 3-diglucoside (1.4 mg 100 g−1 FW) (Pruthi et al., 1961). The predominant volatile compounds in passion fruit pulp belonged to the classes of esters (59.24%, mainly hexyl butanoate and hexyl hexanoate), aldehydes (15.27%, mainly benzaldehyde), ketones (11.70%, mainly 3-pentanone) and

Table 7.1 Nutritional characteristics of purple and yellow passion fruit. Ranges are presented. Purple

Parameter

Weight (g) Diameter (cm) Length (cm) pH Soluble solids content (%Brix) TA (%) Moisture (%) Proteins (%) Fat (%) Glucose (%) Fructose (%) Sucrose (%) Citric acid (%) Malic acid (%) Fibre (%) Ash (%) Sodium (mg 100 g−1 FW) Potassium (mg 100 g−1 FW) Calcium (mg 100 g−1 FW) Magnesium (mg 100 g−1 FW) Iron (mg 100 g−1 FW) Vitamin B6 (mg 100 g−1 FW) Vitamin C (mg 100 g−1 FW) Vitamin E (mg α-tocopherol equivalent 100 g−1 FW)

Yellow

Min

Max

Min

Max

34.49 4.35 4.68 2.97 11.9 0.5 71.83 2.2 0.07 1.93 1.95 2.67 2.58 0.22 11.84 0.47 7.08 100 6.06 16 0.6 0.236 20.9 0.05

55.86 5.57 5.37 4.64 17 5.7 72.57 3.1 0.7 2.27 2.25 3.13 3.42 0.38 13.76 1.887 30 764 53 29 1.6

85 6 7 2.8 11 2.2 55 0.7 0.2

165 8.5 11 3.15 21.4 4.5 79

30 1.12

0.5 3.8 0.4 20

40 0.8

Sources: Arjona et al. (1992), Romero-Rodriguez et al. (1994), Shiomi et al. (1996b), Silva and Mercadante (2002), Nascimento et al. (2003), Rodriguez-Amaya (2003), Leterme et al. (2006), Fonseca and Ospina (2007) and Vasco et al. (2008).

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alcohols (6.56%, mainly benzyl alcohol and 1-hexanol), the other characteristic aroma compounds for passion fruit were limonene, β-ionone and linalool (Narain et al., 2004). Additionally, the difference in flavour and aroma between the purple and yellow passion fruit can be attributed to presence or absence of certain compounds (Rodriguez-Amaya, 2003). Various parts of this plant are biologically active and extracts have been used to treat anxiety, insomnia, asthma, bronchitis, urinary tract infection (Zibadi and Watson, 2004), as a mild sedative, in the treatment of bronchial asthma, nervous gastrointestinal disorders and menopausal problems. These effects have been partially proven, leaf extract have shown antioxidant (Ferreres et al., 2007), anxiolytic (Petry et al., 2001; Coleta et al., 2006) and anti-inflammatory activity (Benincá et al., 2007; Montanher et al., 2007). Peel extract of purple passion fruit reduce blood pressure (Ichimura et al., 2006; Zibadi et al., 2007) and improves wheezing, coughing, and shortness of breath in asthma patients (Watson et al., 2008). The fruit extract accelerates healing of abdominal wall and gastric sutures (Gomes et al., 2006; Silva et al., 2006), colonic anastomosis (Bezerra et al., 2006) and bladder wounds (Gonçalves Filho et al., 2006) in the rat model. Additionally, passiflin, a protein extracted from the seeds has antifungal properties and inhibits growth of breast cancer cells (Lam and Ng, 2009) and inducing apoptosis and decreasing cell viability of MOLT-4 leukaemia lymphoma (De Neira, 2003).

7.2

Preharvest factors affecting fruit quality

7.2.1 Flowering and pollination In tropical regions flowering and production are almost uninterrupted, with two main production periods of three months. In subtropical regions, only one 6–7 months production period occurs. Long days (>10–12 h of daylight) are required to induce flowering (Rodriguez-Amaya, 2003), with day lengths of 11 h or less inhibiting flowering under natural conditions in Hawaii (Nakasone and Paull, 1998). Additionally, a reduction in irradiance below full sun will negatively affect yield and even short periods of low irradiance have residual effects during periods of full sun. Furthermore, flowering is prevented under high temperatures and low irradiance indicating an interaction between temperature and irradiance. This is an important consideration when growing passion fruit in wet tropical environments with extended cloud cover (Menzel and Simpson, 1994). Although they are hermaphrodites (containing male and female organs), passion fruit flowers are self-sterile (self-fertilization cannot happen), and yellow passion fruit flowers are even self-incompatible (self-pollination cannot occur). The different forms open at different times in the day, the flowers of the purple passion fruit from dawn until midday, the yellow open at midday and close in the evening. Three types of flowers can be found on yellow passion fruit and they are very sensitive to rain during the pollination period, with rain within 1.5 h after pollination preventing pollen germination and pollen tube growth (Morton, 1987; Rodriguez-Amaya, 2003).

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Fruit set, numbers of seed, fruit weight, and juice yield depend on the amount of pollen deposited on the stigma (Akamine and Girolami, 1959); and without seed development, no juice will form (Knight and Winters, 1962). Passion fruit are usually pollinated by large bees (Xylocopa, Centris, Epicharis, Eulaema, Bombus, Ptiloglossa). Smaller bees like honeybees (Apis spp.) and stingless bees (Trigona sp.) are too small; they will visit the flowers but cannot transfer the pollen. Wooden logs are often placed in the orchards to ensure carpenter bee nesting. Hand pollination is also used to great extent and field workers can pollinate about 600 flowers per hour (Westerkamp and Gottsberger, 2000) with high success rates. Additionally, hand pollinated flowers are said to produce larger and juicier fruit (Rodriguez-Amaya, 2003). 7.2.2 Fruit growth, development and maturation Passion fruit have a single sigmoid growth curve with accelerated fruit growth during the first 20–21 days after anthesis (DAA) (Shiomi et al., 1996b; Hernández and Fischer, 2009). Pocasangre Enamorado et al. (1995) found that in yellow passion fruit, the maximum fruit size found at 21 DAA was due mainly to rind growth. For purple passion fruit, during this period there is also high respiration and ethylene production, followed by very low production up to 70 DAA (Shiomi et al., 1996b). The titratable acidity (TA) increases during the first 60 DAA for purple (Shiomi et al., 1996b) and 63–70 DAA for yellow (Pocasangre Enamorado et al., 1995; Vianna-Silva et al., 2005) and decreases thereafter. In general, SSC in the juice increases up to harvest; however, Pocasangre Enamorado et al. (1995) observed the highest accumulation of SSC 63 DAA. During this whole period the skin stays green up to 70 DAA after colour changes rapidly within the next 20–30 days (Shiomi et al., 1996b; Vianna-Silva et al., 2005). During the final stage of fruit maturation, vitamin C and carotene content will also increase. Purple (Arjona and Matta, 1991) and yellow (Vianna-Silva et al., 2005) passion fruit are mature around 70 DAA. 7.2.3 Maturity and harvest The skin colour of passion fruit can be used as a maturity index (Pruthi, 1963); seven maturity stages have been defined, related to the changes in colour of the skin from green to purple (see Plate XIII in the colour section between pages 238 and 239) for purple passion fruit (Pinzón et al., 2007) and from green to yellow (see Table 7.2) for yellow passion fruit (Vianna-Silva et al., 2008). Pinzón et al. (2007) recommend harvesting the purple passion fruit when the index reaches 3, which corresponds with 50% green and 50% purple (see Plate XIII in the colour section), approximately 70 days after flowering (Shiomi et al., 1996b). If harvested before this stage, fruit will not develop the full purple colour. Additionally, consumers prefer a purple colour at least 80–90% of the fruit surface and less than 75% is unacceptable for markets (Arjona and Matta, 1991).

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Maturity stages of yellow passion fruit

Maturity stage

Characterization

1 2 3 4 5 6 7

Peel totally green 4.7% of peel yellow 21.3% of peel yellow 28.5% of peel yellow 65.9% of peel yellow 82.4% of peel yellow 100% of peel yellow

Source: With permission from Vianna-Silva et al., 2008.

Fruit can be harvested when the skin is partially purple (approximately 70 days after flowering) as it will then continue to develop the full purple colour after harvest (Shiomi et al., 1996b). However, fruit will not develop the full purple colour if it is harvested at an immature stage (before 70 days after flowering). Additionally, consumers prefer a purple colour at least 80–90% of the fruit surface and less than 75% is unacceptable for markets (Arjona and Matta, 1991). The SSC/TA ratio is another parameter that can also be used as a maturity or ripening index. A higher SSC corresponds to more sweetness and a higher TA to more sourness (Harker et al., 2002). Shiomi et al. (1996a) and Pongjaruvat (2008) found that eating quality of purple passion fruit improved mainly due to a decrease in acidity. This is probably because in sensory tests, sourness has been shown to overshadow the sweetness sensation, and as sourness decreases with a decrease in TA during storage, sweetness is unmasked.

7.3

Postharvest physiology and quality

7.3.1 Respiration and ethylene production Passion fruit is a climacteric fruit with a high respiration rate of 400–1890 nmol kg−1s−1 for purple passion fruit at 20–25 °C (Shiomi et al., 1996b; Schotsmans et al., 2008). Ethylene production is also high and increases with ripening from 0.03 to 9.35 nmol kg−1s−1 (Shiomi et al., 1996b). The content of 1-aminocyclopropane-1carboxylic acid (ACC) and the activity of ACC synthase are low during the initial stage of ripening while the ACC oxidase activity is already high and they all increase during ripening, especially in juice sac and seed (Shiomi et al., 1996a; Mita et al., 1998). Expression of Pe-ACS1 and Pe-ACO1 are enhanced during ripening with increased expression of Pe-ACO1 starting first and expression much higher in arils than in seeds, resulting in a much higher level of ethylene being produced in arils than in seeds or peels during ripening (Mita et al., 1998). The level of expression of the ethylene receptors Pe-ETR1 and Pe-ERS1 did not significantly change over the course of ripening, but again much higher levels were found in arils than in seeds (Mita et al., 1998).

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7.3.2 Ripening, quality components and indices The most noticeable change is in skin colour. For purple passion fruit (see Plate XIII in the colour section) the colour gradually changes from green to purple (Pinzón et al., 2007) and for yellow passion fruit (see Table 7.2) from green to yellow (Vianna-Silva et al., 2008), which makes this characteristic perfect for use as a maturity index as discussed before. In purple passion fruit, at the same time as the colour change, the weight of the pulp increases, reaching a maximum around maturity stage 4 (85–95% coloured, 15–20% green) (Pinzón et al., 2007) while the total weight decreases (Kishore et al., 2006; Pongjaruvat, 2008). This is also related to the development of shrivelling, which is maximal at full ripeness (Schotsmans et al., 2008) and negatively affects consumer and market perception. The seemingly contradictory effect of increase in pulp with decrease in total weight is due to water loss which happens mainly from the peel (Pongjaruvat, 2008) evidenced in the decrease in thickness of the skin (Kishore et al., 2006; Pinzón et al., 2007). Firmness decreases fastest in the initial stage of ripening, slowing down thereafter (Kishore et al., 2006; Pinzón et al., 2007). The pH remains stable between stages 0 and 4 at 3.0 and then increases to 3.5. The SSC increases up to stage 3 whereas the TA decreases, resulting in an increase in SSC/TA ratio (Kishore et al., 2006; Pinzón et al., 2007; Pongjaruvat, 2008). Additional changes include loss of vitamin C (42.6–34.0 mg 100 g−1) increase in reducing and total sugars and changes in the pulp colour from light yellow to pink with a perceptible increase in flavour with ripening (Kishore et al., 2006). In yellow passion fruit, as the colour changes, the pH remains stable between stages 0 and 6 at 2.6 and then increases to 3.7. SSC increases from 13.43 (totally green) to 16.3 (totally yellow), the TA increases from 5.21% to 5.37% at stage 2 and then decreases to 4.64 at stage 7. This again results in an increase in SSC/TA ratio during maturation from 2.4–2.6 at stage 0 to 3.5 at stage 7 (Vianna-Silva et al., 2008).

7.4

Postharvest handling factors affecting quality

7.4.1 Handling and grading Fruit is harvested weekly or more frequently depending on the demand. Harvest is done by hand and preferably in the early hours of the day when the fruit is cooler and not subjected to sun and increase in temperature. Pressure is applied at the abscission zone near the calyx of the fruit or using scissors. Depending on market requirements, fruit are harvested with or without stem (Hernández and Fischer, 2009). For purple passion fruit, the colour changes can be used as a guide (Shiomi et al., 1996b). In other cases, fruit is gathered from the ground as it naturally drops when it ripens (Chavan and Kadam, 1995), however this is not advised as it increased the risk of bruising and infections. Passion fruit are harvested in small plastic baskets (of 2.5 kg) or cardboard boxes. Once harvested, diseased and damaged fruit (insect damage, physiological

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or physical disorders) are removed. Fruit is further graded according to size and marketed in boxes containing three to four layers of fruit separated by newspaper to prevent deterioration (Hernández and Fischer, 2009). 7.4.2 Temperature and relative humidity The optimal reported storage conditions for passion fruit vary between 5 °C and 10 °C and 85–90% RH. Temperature markedly affects the changes during storage, with a lower temperature decreasing the weight loss of the fruits (Arjona et al., 1992; Shiomi et al., 1996b; Schotsmans et al., 2008), the respiration rate (Pongjaruvat, 2008; Schotsmans et al., 2008) and the loss of SSC (Arjona et al., 1992). For purple passion fruit storage at 4–5 °C is reported to increase the commercial life of the fruit by 50% compared with fruit stored at room temperature (Hernández and Fischer, 2009). However, for yellow passion fruit a higher temperature of 10 °C is recommended since at this temperature shrivelling and weight loss is minimal compared with lower (5 °C) and higher (15 °C) temperatures (Arjona et al., 1992). Water loss and thus weight loss and shrivelling can be decreased even more by ensuring a high RH using packaging (Pongjaruvat, 2008) or film wrap (Arjona et al., 1994a). The lower water loss will also ensure turgor pressure in the cells remains high and improve the stiffness or compression firmness of the fruit (Pongjaruvat, 2008). High RH appears to negatively affect pulp yield, however, this is due to the fact that less water is being lost from the skin thus keeping the fruit weight the same (Arjona et al., 1994a; Pongjaruvat, 2008). High RH also prevents shrivelling and toughening of the peel (Pruthi, 1963; Arjona et al., 1994b; Schotsmans et al., 2008). Although increasing RH has many beneficial effects, care has to be taken when using high RH since it can also result in increased fungal growth (Pongjaruvat, 2008). 7.4.3 Packaging The beneficial effect of packaging is already clear at higher temperatures. Wrapping purple passion fruit in ‘Vinipel’ film wrap (PVC), at ambient temperature (18 °C) preserves quality for up to 10 to 12 days. Lowering the temperature (6 °C) prolonged this beneficial effect to 24 days (16 days in cold room + 8 days shelf life) (Pachón et al., 2006). Likewise, packaging purple passion fruit in perforated HDPE of 0.03 mm thickness increased shelf life to 24 days at 5 °C while better preserving quality (SSC, TA) and nutritional value (vitamin C) of the fruit (Singh et al., 2007). Wrapping yellow passion fruit in plasticized PVC film slows down shrivelling and weight loss during 30 days of storage at 10 °C (Arjona et al., 1994b), this could be attributed to the high RH of 85% of the modified atmosphere (13% O2 and 0.5% CO2) in the packaging. Pongjaruvat (2008) also found that packaging of purple passion fruit reduced weight loss and shrivelling, slowed down the changes in colour, pH, TA, sweetness, and sourness, maintained fruit firmness, and extended shelf life. However, again it was not clear if this was due to the altered gas composition (1–4 kPa O2 and 6 kPa CO2) or purely the increase in RH.

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Care must be taken when using modified atmosphere packaging since condensation and adverse atmosphere conditions can cause disorders like an increase in fungal growth and red bleeding. 7.4.4 Controlled atmosphere storage Pruthi (1963) noted that purple passion fruit could be kept in 5% O2 and 5% CO2 for six weeks. 7.4.5 Ethylene Purple passion fruit is sensitive to exogenous ethylene as it accelerates endogenous ethylene production (Shiomi et al., 1996a) and can thus accelerate ripening. This sensitivity is not clearly present at harvest since application of 1000 ppm ethylene for 24 h did not induce earlier onset of ethylene production when applied on harvest day, but was effective when applied one day or five days after harvest (Shiomi et al., 1996a). This has to be taken into account when using MAP packaging because it can result in accumulation of ethylene thus counteracting the beneficial effects on ripening delay. Ethylene can also be used to improve colour development of fruit harvested at the mature-green stage (Arjona and Matta, 1991). 7.4.6 Waxing The application of paraffin wax coating to purple passion fruit reduced weight loss and enhanced fruit appearance for five weeks (Pruthi, 1963). This is different from findings in purple passion fruit by Dagame et al. (1991) and Pongjaruvat (2008) where adding wax on the fruit surface did not improve storage life. Pachón et al. (2006) had the same experience in purple passion fruit but stated that even though the effects of the treatment are minimal, this would be a good general practice for fruit that does not have to be transported far if only for the effect on the external appearance for the fruit going to the local markets.

7.5

Crop losses

7.5.1 Chilling injury Below 6.5 °C fruit is affected by chilling injury resulting in red discolouration on the surface (Pruthi, 1963). This was also noted in trials by Pongjaruvat (2008) who recorded red bleeding but attributed this more to development of atmospheric conditions within MAP. 7.5.2 Pathological disorders One of the most important disorders in passion fruit is woodiness or ‘bullet’ with incidences of 71.8–73.1% in commercial orchards in Brazil (Novaes and

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Rezende, 2003), which is caused by the passion fruit woodiness virus (PWV) (Inch, 1978) or by the cucumber mosaic virus. Affected leaves are stunted, curled and discoloured, while the fruits are often under-sized, misshapen, hard and dry (Griesbach, 1992). The virus is easily transmitted by mechanical means and by aphids, especially Myzus persicae Sulz. and Aphis gossypii Glover (Chagas et al., 1981). In Australia, the disorder has been successfully controlled by introducing hybrid cultivars since these are tolerant of the common strains of woodiness virus (Taylor and Greber, 1973; Inch, 1978). After massive wilting in commercial plantations of purple passion fruit, grafting on wilt-resistance seedlings of the yellow passion fruit has proven to be the only satisfactory method to control soilborne diseases such as fusarium wilt (F. oxysporum f. passiflorae) (Inch, 1978; Nakasone and Paull, 1998). The often used harvest method to gather from the ground as the fruit naturally drops when it ripens (Chavan and Kadam, 1995) also results in fruit that is highly contaminated with soil-borne pathogens. Additionally, the use of polyethylene bags to ensure high RH does not reduce fungal attack (Pruthi, 1963). However, adding a 5% Lysol solution to the polyethylene bag successfully reduced fungal attack. The common fungal attacks are by Alternaria passiflorae with circular, sunken, and brown spots on the fruit surface, and septoria blotch caused by Septoria passiflorae (Rodriguez-Amaya, 2003). Pruthi (1963) noted that during long term storage at 6.5 °C, passion fruit was attacked by white (Fusarium oxysporum), blue (Penicillium expansum), and black (Aspergillus niger and Rhyzopus nigricans) fungus. Experiments with yellow passion fruit from conventional and organic orchards started at ambient temperature (25 °C) and high RH, revealed that all fruit contracted anthracnose, caused by Colletotrichum gloeosporioides and presenting as light-brown patches that increase in size and evolve into a soft rot. Fusarium rot affected 25.5% and 19% and Phomopsis rot 11% and 2% of conventional and organic fruit, respectively (Fischer et al., 2007). Phomopsis rot can be found as a stem end rot on the passion fruit. Cladosporium herbarum and Cladosporium oxysporum cause powdery spot and fruit scab in cooler moist areas, but so far no fungicidal measures have been found. Fytosanitary actions to prevent these diseases include foliar fungicide application with Mancozeb + cupper oxychloride or thiophanate methyl, and sporadically the insecticide Fenthion. In the search for biological control measures against anthracnose, Cymbopogon citratus essential oil has been evaluated for the control of postharvest decay in yellow passion fruit but it could not prevent anthracnose in yellow passion fruit (Anaruma et al., 2010). 7.5.3 Insect pests and their control Thrips (Trips spp.) can damage plants, mainly during dry weather. Damage by thrips while feeding leads to mottled punctures on the leaves and fruit which may shrivel and drop prematurely (Ondieki, 1975).

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Mites (Tetranychus urticae) cause brown coloured abrasions on the rind because they puncture the cells and drain their contents, especially close to the stalk (Mora and Benavides, 2009). Various types of flies can attack passion fruit. In Colombia, a complex of Dasiops sp. and Hexachaeta sp. cause severe damage. They cause flower and fruit abortion by consuming the content of the ovarian or the fruit itself. The affected fruit progressively wrinkle depending on the number of larvae present in the fruit and eventually drop. When cut open, the fruit is empty and shows initiation of fungal growth (Mora and Benavides, 2009). Suggested control measures include trapping, removal of pupae and larvae by destroying fallen flower buds and fruits. Passion fruit can also be a host to Mediterranean fruit fly so all quarantine measures related to this pest will apply when exporting to countries imposing quarantine measures for Mediterranean fruit fly. Additionally, since PWV is transmitted by aphids, especially Myzus persicae Sulz. and Aphis gossypii Glover (Chagas et al., 1981), it is important to control these. Care should be taken to apply only those insecticides and acaricides which are recommended for use on fruit crops and which will not interfere with the canning quality of the juice (Ondieki, 1975).

7.6

Processing

Passion fruit juice is the third most wanted exotic flavour after mango and pineapple and can be provided as juice at 14 °Brix or in concentrated form at 50 °Brix, which is more in demand (Isaacs, 2009). Fruit for processing is collected daily or weekly and transported to the processing plant, where rotten and unfit are removed. Then the fruit are washed with strong sprays of water to remove all dirt and leaves and other substances adhering to the fruit. The entire fruit is dropped between two rotating converging cones and when it bursts open, skins are carried through the cones whereas the pulp drops into a finisher (Hui et al., 2006). In another method, rotating, circular knives slice open the fruit and all is put in a continuous basket centrifuge, or the juice, pulp and seeds are forced through the holes in the wall and the rind stays behind. Afterwards, the seeds are removed from the pulp and juice by a screened pulper followed by a screened finisher leaving only clean juice (Hui et al., 2006). The main concern is the extreme heat sensitivity of the aroma and flavour components of the juice, making pasteurization difficult. Additionally, the high starch content of the juice can cause accumulation on the surfaces of the processing equipment, affecting efficiency (Hui et al., 2006). The juice can be consumed pure or diluted into a nectar or in mixes with other fruit juices. Additionally it can be concentrated to a juice of 43.5–50 °Brix but about 39% of the volatile components are lost in the process (Shaw et al., 2001). For yellow passion fruit, research has been directed to determine the ideal maturity stage for processing, and even though some changes may occur, fruit from stage 4 onwards (see Table 7.2) are suitable for processing (De Marchi et al., 2000).

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Another important consideration in passion fruit processing is the waste production, which constitutes almost 75% of the raw material. Of this, 90% is the peel which can be used for the production of pectin (Schieber et al., 2001), which is used as a gelling agent and stabilizer. Pectin can be extracted successfully from passion fruit peel with citric acid (Pinheiro et al., 2008). Oil from passion fruit seeds is high in linoleic and linolenic acid, making passion fruit seed a valuable non-conventional source for high-quality oil (Liu et al., 2008).

7.7

Conclusions

Passiflora edulis (sour passion fruit), native from Brazil, is known in two forms, the purple and the yellow passion fruit. Both behave similarly during flowering, fruit growth, maturation and ripening but they mainly differ in colour, SSC and TA level as well as their aroma components. They are both climacteric fruit with high respiration and ethylene production. The main quality changes during storage and ripening include decrease of acidity resulting in higher apparent sweetness and weight loss resulting in shrivelling. The latter is not appreciated by consumers who prefer a smooth fruit. Another important difference is the temperature requirement during storage. Where purple passion fruit is best stored at 4–5 °C, yellow passion fruit prefers a higher temperature of 10 °C. The main market for both forms is the processing industry and most of the export consists of juice.

7.8

References

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8 Pecan (Carya illinoiensis (Wangenh.) K. Koch.) A. A. Gardea and M. A. Martínez-Téllez, Research Center for Food and Development, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico

Abstract: A native species of North America, pecans are grown in several countries around the world. The nuts are well known for their important benefits for consumers’ health, including properties to prevent heart disease. Pecan quality attributes are well defined and set the standards not only for marketing issues, but also for breeding programs as well. Because of their low respiration rates, pecans are suitable for long-term storage, providing that conditions to prevent oxidation reactions are minimized. Both kernel darkening and rancidity development are oxidative reactions, which can be prevented by proper cold storage and limited exposure to air; however cold storage by itself reduces the reaction rate significantly. This chapter describes the guidelines for the management of pecans from harvesting to storage. Key words: Carya illinoiensis, pecan, postharvest, nutrition, processing.

8.1

Introduction

Public perception about the importance of selecting appropriate foods to support healthy lifestyles dictates particular attention not only to nutritional contents, but also to all of the nutraceutical properties found in foods. The nuts of the pecan tree are particularly rich in compounds that offer such positive impacts in our body (Yahia, 2010). It is recommended that regular intake of these nuts has protective effects against several maladies related to our modern sedentary life. Endemic to North America, pecans have been the staple of natives for centuries. Today, they are also grown in many countries, and although most of the crop is still produced in its original region, their marketing is expanding. Oleic and linoleic fatty acids are the main constituents of pecan oils and their content of unsaturated lipids is ten times higher than their saturated fats, not to mention a

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wide series of other protective mechanisms related to their nutrients, micronutrients, vitamins, tocopherols, and diverse phytochemicals (Yahia, 2010). Pecan nuts, like all nuts, have very low respiration rates and quality deterioration. This chapter describes general guidelines for proper management of pecans from the moment they are harvested, through their postharvest handling and storage. 8.1.1 Origen and distribution Although native to North America, at present pecans are widely distributed in Australia, Brazil, China, Israel, Peru and South Africa; the largest acreage being found in the USA, followed by Mexico. Commercial pecan growing started in the United States, where the oldest groves are found, although Australian orchards have been under cultivation for the last forty years (Wakeling et al., 2000). The Spaniards were the first Europeans to find pecans in northern Mexico in the sixteenth century and legend has it that the birth rate of local natives was closely associated with the biannual bearing cycle characteristic of this species, implying its important role as a staple food. Pecans are a conspicuous element of the gallery forests (Beard, 1955; Sparks, 2005), typical of the semiarid regions of both Southern USA and Northern Mexico, as well as the deciduous forests of the USA east of the Mississippi. Not surprisingly, the largest diversity in native pecans is found in the USA, a situation that was considered when the United States Department of Agriculture (USDA) established a breeding and selection program that has yielded results for the last seventy years. Many of the commercially important varieties were originated from such a program, and continue to provide the industry with improved germplasm (Thompson and Grauke, 2003). So far, breeding programs in the United States continue to lead the search for improved germplasm (Sparks, 1992), and a review of the initial parameters is in continuous demand by the industry (Heaton et al., 1975). Taxonomically classified in the Junglandaceae family, pecans (Carya illinoinensis (Wangenh.) K. Koch) (USDA, 2010b) are an American species related to English walnuts (Juglans regia L.), actually a Caucasian species, and other American species such as Arizona, Southern California and Northern California walnuts and black walnut (Juglans nigra L.), whose high quality wood and veneers are highly demanded. Also, 21 other hickory species are included in this family (USDA, 2010a). 8.1.2 Production and consumption Pecan consumption in its countries of origin, the USA and Mexico, is higher than elsewhere. In the United States, almonds (Prunus amygdalus Batsh) and English walnuts (Juglans regia L.) are the nuts recording the highest consumption, followed by pecans. Pecan consumption in the United States, with a ten year average production of 114.4 M kg (Hadjigeorgalis et al., 2005), is 218 to 375 g per capita (Geisler, 2010). In Mexico, official numbers report an annual consumption of 250 g per person (Milenio, 2008), however, the inclusion of temporal inventories (like temporal imports for shelling), may be artificially increasing an otherwise more realistic figure. The United States accounts for the

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largest export and import of pecans; its top buyer being Hong Kong, while most of in-shell and shelled pecan imports are from Mexico (Geisler, 2010). Nonetheless, pecan consumption is expected to grow given an increase in plantings and an expanding market. The increase in consumption will depend on several factors, the most important of them being the extent of increasing trends in consumption of healthy foods.

8.2

Nutritional value of pecan nuts

Tree nuts are considered rich sources of different phytochemicals that may contribute to health benefits because of their antioxidant, anti-proliferative, antiinflammatory, anti-viral and hypocholesterolemic properties (Bolling et al., 2010; Yahia, 2010). Such compounds include carotenoids, hydrolysable tannins, lignans, naphtoquinones, phenolic acids, phytosterols, polyphenols and tocopherols (Bolling et al., 2010). Pecan meat is an excellent source of many nutrients and phytochemicals (Table 8.1). By contrasting those figures it is clear that, as compared with almonds and English walnuts, pecans are richer in calories, linoleic acid, some micronutrients (zinc, copper and manganese) and some vitamins (particularly vitamins A and K), as well as γ-tocopherol (Self Nutrition Data, 2010). Kernel protein content accounts for 9 g per 100 g−1 of meat, although it is considered as genotype related. Wakeling et al. (2001) found that protein content was the only significant difference between Western Schley and Wichita pecans grown in Australia as compared to higher contents found when grown in the United States. Therefore, the information below must be viewed as a reference rather than universal values, and differences due to genotype, environment and their interaction should be taken in account. Pecans are rich in mono and polyunsaturated fatty acids. According to Rudolph et al. (1992) the most abundant fatty acids in pecan kernels are: oleic>linoleic> palmitic>stearic> linolenic, although their concentration may vary with genotype, maturity and year crop (McMeans and Malstrom, 1982). Other works report up to ten different fatty acids (Senter and Hdrvat, 1976). Oleic and linoleic acids comprise from 90% (Villarreal-Lozoya et al., 2007) to 95% (Herrera, 2005) of total kernel oil content, the high oleic acid content being the source for biosynthesis of linoleic and linolenic acids, as occurs in oilseeds (Toro-Vazquez et al., 1999). It is during embryo and cotyledon expansion when fatty acids accumulate in kernels (Wood and McMeans, 1982). Another benefit for consumers’ health is that pecan oil has ten times more unsaturated than saturated fatty acids (Yao et al., 1992), besides up to 22 g and 1 g per serving of total omega-6 and total omega-3 fatty acids, respectively (Self Nutrition Data, 2010). It has been reported that consumption of pecans lowers the risk of heart disease (Yahia, 2010). Mukuddem-Petersen et al. (2005) concluded that consumption of 50 to 100 g d−1 of nuts, at least five times a week, as part of a heart-healthy diet with a total fat content of 35% of energy, significantly decreased total cholesterol and LDL-cholesterol in normo- and hyperlipidemic individuals.

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Table 8.1 Nutrients and health improving compounds present in the three most consumed nuts in the USA Nutrients in 100 grams of meat

Calories, kcal Protein, g Total fat, g Saturated fat, g Monounsaturated fat, g Polyunsaturated fat, g Linoleic acid (18:2), g Linolenic acid (18:3), g Carbohydrates, g Fiber, g Calcium, mg Iron, mg Magnesium, mg Phosphorus, mg Potassium, mg Sodium, mg Zinc, mg Copper, mg Manganese, mg Selenium, μg Vitamin C, mg Thiamin, mg Riboflavin, mg Niacin, mg Pantothenic acid, mg Vitamin B6, mg Folate, μg Vitamin A, intl. units Vitamin K, μg Vitamin E Tocopherol, α, mg Tocopherol, β, mg Tocopherol, γ, mg Tocopherol, δ, mg

Phytochemicals in 100 grams of meat

Wal

Alm

Pec

650 15 65 6

580 21 51 4

690 9 72 6

9

32

41

47

12

22

38

12

21

9

0

1

14 7 98 2.91 158 346 441 2 3.09 1.59 3.41

20 12 248 4.30 275 474 728 1 3.36 1.11 2.53

14 10 70 2.53 121 277 410 0 4.53 1.20 4.50

4.90 1.30 0.34 0.15 1.12 0.57

2.80 0 0.24 0.81 3.92 0.35

3.80 1.10 0.66 0.13 1.17 0.86

0.54 98 20 2.70 0.70 0.15 20.8 1.89

Wal Carotenoids Carotene β, μg Lutein, μg Lutein + zeaxanthin, μg Cryptoxanthin, β

0

3 8.47 1

29 17.6 17

0

9

Total phytosterols, mg 72

120

97

Stigmasterol, mg Campestrol β-sitosterol

4 5 111

3 5 89

Phytosterols

Flavonoids Catechin, mg Cyanidin, mg Delphinidin, mg Epicatechin, mg Epigallocatechin, mg Epigallocatechin gallate, mg Proanthocyanidins Monomers, mg Dimers, mg Trimers, mg 4–6mers, mg

0.13 0.21 7–10mers, mg 29 22 Polymers, mg 5 56 0

12 7.1 9

Alm Pec

1 7 64 0 2.47 0 0 0 0

7.34 6.0 7.62 23.3

2.47 0 0 0.35 2.12 0.70

6.70 9.88 6.70 0.70 5.29 2.12

8.22 18.23 10.1 44.6 9.35 27.6 42.3 107.3

5.71 39.9 21.2 84.9

89.1 235.9

3.50

25.9 1.40 0.43 0.39 0.89 24.4 0.25 0.47

Sources: Nutrients. USDA National Nutrient Database for Standard Reference, Release 16, last update 2005. International Tree Nut Council Nutrition Research and Education Foundation, September, 2003. Phytochemicals. USDA Phytochemical Study (2004), USDA Nutrient Database Standard Reference, Release 17, 2006. USDA database for the Proanthocyanidin Content of Selected Foods (2004), www.nal.usda.gov/fnic/foodcomp. All data were normalized from original units to 100 g of meat. Wal: walnuts, Alm: almonds, Pec: pecans

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A close look at the data in Table 8.1 also shows that pecans represent the highest source of antioxidants of these three species, confirming earlier findings by Villarreal-Lozoya et al. (2007), who demonstrated that phenolic compounds with high antioxidant capacity in both kernels and shells make pecan nuts an important dietary source of antioxidants. Villarreal-Lozoya et al. (2007) reported that phytochemical constituents and antioxidant capacity (ACORAC values) of pecan varieties ranged from 372 to 817 mu mol trolox equivalents g−1 defatted kernels, while total phenolics ranged from 62 to 106 mg of chlorogenic acid equivalents g−1 defattened kernels. They also reported that condensed tannins varied from 23 to 47 mg catechin equivalents g−1 defattened kernels. Phenolic compounds with high antioxidant capacity in kernels and shells indicate that pecans can be considered as an important dietary source of antioxidants. Another important consideration when determining phenolic compounds and antioxidant capacity of pecan kernels is that samples must be previously defattened and measured in the acetone fraction, since different solvents deplete the samples and allow a more precise measurement (Pinheiro do Prado et al., 2009a, b). Importantly, pecans are rich in carotenoids, flavonoids and proanthocyanidins, having high content of phytosterols as well (Bhagwat et al., 2004). All of these are associated with improving the antioxidant capacity of our body. For the reasons described above, health specialists recommend the inclusion of nuts in diets to achieve a healthier feeding style (Mukuddem-Petersen et al., 2005; López-Uriarte et al., 2009). Observational studies suggest that nut consumption is inversely associated with the incidence of cardiovascular disease and cancer (Oliver-Chen and Blumenberg, 2008). These facts may explain why nowadays pecans are receiving a wider attention from health-caring consumers. It must be emphasized also that pecans, like other nuts and almost any foodstuff, may trigger allergic reactions in susceptible individuals and specific antigens have been developed for accurate diagnosis (Venkatachalam et al., 2007).

8.3

Harvesting, handling and storage

Harvest is accomplished in different ways, and in an increasing fashion. Mechanization is becoming the most common way, varying depending on the financial resources available to growers. Figure 8.1 shows a typical sequence common to heavily mechanized operations. 8.3.1 Soil preparation Since the nuts are picked directly from the ground, soil preparation is very important and its objective is getting a surface as flat and smooth as possible. 8.3.2 Tree shaking Once the soil is prepared, the next step is getting the nuts off the tree. This is accomplished by shaking the trees with machinery specially developed for

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Fig. 8.1

Description of typical mechanized harvest operations in a commercial pecan orchard.

nut crops (see Plate XIV in the colour section between pages 238 and 239). Growers have the choice of having their own machinery or hiring a contractor. Many prefer the latter since they avoid the high investment and maintenance costs involved, as well as the problem of having to train personnel every season, not to mention the highest risk of inflicting mechanical injuries to trunks and limbs because of a careless operation or an unskilled operator. By shaking the main trunk and limbs, the nuts are separated and fall to the soil or onto canvas previously spread underneath the trees. In the latter case, the nuts are collected from the canvas and loaded directly into containers to be transported to the sorting facility (Figs 8.2–8.5 and Plate XV in the colour section). If felled directly onto the soil, then the next procedure is followed. 8.3.3 Wind row formation Wind roads are rows of nuts between the tree lines, leaving them ready to be picked by a harvester, and specially designed implements named V-rakes are connected to the front of tractors to create these wind roads of pecans.

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Fig. 8.2 Manual collection, an alternative to mechanization (courtesy of Dr Humberto Núñez).

Fig. 8.3

Nuts in a row ready for pick up (courtesy of Dr Humberto Núñez).

8.3.4 Nuts pick up and initial transport The harvester outputs the nuts into containers to be transported to the sorting facility and separates leaves and light debris by blowing them away to the sides. It must be pointed out that normally harvest should follow shuck dehiscence, but

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Fig. 8.4

Picking up of nuts and loading for transport to sorting facility (courtesy of Dr Humberto Núñez).

Fig. 8.5 Manual selection, sizing and grading of in-shell pecans (courtesy of Dr Humberto Núñez).

under particular circumstances it may be desirable to harvest as soon as the endosperms are ripe, without regard to shucks still being closed. Therefore they must be eliminated in an intermediate step, before sorting and grading can be attempted. Since a wide range of technologies are available, the above procedure is adjusted accordingly, but the final objective remains the same: getting the nuts

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off the trees and collecting and transporting them to the storage facility, as fast as possible. 8.3.5 Immediate nut management Once the nuts are in the storage facility, they are handled either in sacs or metal containers that hold up to 1000 kg of in-shell pecans. Commercial storing conditions commonly used are −13.8 to −9.4 °C and 40% relative humidity (RH). Given the necessity that nuts may be stored for up to three years (more commonly for up to 10 months) the rancidity index must stay below 0.1% of free fatty acid content. 8.3.6 Preparing nuts for processing Once the nuts are ready for process, they are tempered at ambient temperature for 24 to 36 hours, which brings some moisture back into the nuts. Before pasteurization may be attempted, the nuts must be conditioned at room temperature for 4 to 8 hours in tanks, while water is sprayed on top. Pasteurization is achieved by hot water baths with a temperature range between 71.1 to 76.6 °C and an exposure time that varies widely within the industry. Since this is considered a critical control point, it is important that if any microbial assessment is to be considered, sampling should be done right after this step. 8.3.7 Shelling At this point the nuts are ready to be shelled and this is accomplished by a two step process. First, the nuts are mechanically cracked and second, the shells are removed by aspiration. Another alternative is by running everything on water and separating materials by flotation, although this causes water intake by kernels, which has to be adjusted later on. 8.3.8 Sizing and grading Afterwards the nuts are sorted by size, and arrays of several electronic sorters guarantee a good separation. Grading according to color may be achieved through a wide spectrum ranging from manual to infrared technologies depending on the operation size and financial resources. As a final selection step, sizing is done by running the meats through screens, although it can also be done along a band and manually picked. Before packing, the meats may be screened for metal debris using magnets and metal detectors. This process may be repeated two or three times to ensure the absence of this type of physical contaminant, which may include ferrous, non-ferrous and stainless steel particles. 8.3.9 Packing A 13.6 kg box is the industry standard for packing pecans, but bags of 226.8, 453.6 and 907.2 g (8, 16 and 32 ounces, respectively) are also commonly found

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at retailers. Even when boxes are used, the meats are first bagged in food grade polyethylene bags, heat sealed under vacuum. Box dimensions are 38.7 × 28.6 × 25.7 cm (15¼ × 11¼ × 10⅛ inches) (L × W × D) and preferred construction is single-wall corrugated Kraft fiberboard, wax-coated inside to delay oil penetrations. When using boxes, palletizing standards are ten boxes per layer by five boxes high for a total of 50 boxes on a 121.9 × 101.6 cm (48 × 40 inches) standard GMA pallet. 8.3.10 Early season harvest Seed testa color is a quality attribute of paramount economical significance in the pecan industry. It is negatively affected by exposure to high temperatures, as occurs while ripenned nuts are left on the tree waiting for shuck dehiscence to start harvesting. Therefore, early season harvest is becoming popular, particularly in those places where fall temperatures are still high. Herrera (1994) found that Western Schleys grown at Las Cruces, New Mexico can be harvested up to four weeks in advance and artificially dried without deleterious effects on flavor. However, this creates a different problem as shucks must be mechanically removed from nuts, so specific equipment has needed to be designed (Verma et al., 1991). Also, nut water content must be lowered to 4% from as high as 24% (Herrera, 2005) since it has been noted that nuts with a 6% water content do not store well (LSU, 2009). Early harvest is a common practice in the southern Sonoran Desert of Mexico, which advances harvest for up to 40 days as compared with its counterparts in the Mexican highlands growing at the same latitude.

8.4

Current quality grading system

The following account summarizes the quality expected for export pecan halves and pieces in the American industry as followed by The Green Valley Pecan Company of Southern Arizona (www.greenvalleypecan.com) and is based on outlines defined elsewhere. 8.4.1

Quality standards

Microbiological A total plate count of less than 10 000 cfu g−1, yeast and mold below 1000 cfu g−1, and coliforms below 100 cfu g−1, while E. coli, Staphylococcus and Salmonella should not be detectable. Chemical To ensure minimum rancidity, a maximum free fatty acid content of 0.4% and a maximum peroxide value of 5 meq kg−1 are required. As for contaminants, on aflatoxin level of 2 ppb is set as the maximum limit.

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Physical contaminants Since shell pieces may escape detection and become a physical contaminant, the maximum standard allowed for each 45.4 kg (100 lbs) has been set at three hard shells for pecan halves, for large to medium pieces up to four hard shells and no more than five hard shells in the case of small pieces. As described before, magnets and metal detectors are used to avoid metal contaminants, both ferrous and nonferrous, as well as stainless steel pieces. Although no particular mention is made regarding insects and insect parts, it is advisable to avoid their presence and it is in the smallest pieces where their detection may become more difficult. 8.4.2 Color As for physical characteristics, nut color must be a characteristic golden or amber, while meat texture should be firm and crispy. No musky or rancid odors should be present. The high linoleic acid content of pecan kernels make them highly susceptible to becoming rancid (Herrera, 2005), thus every attempt to avoid this defect must be taken into consideration. 8.4.3 Sizing Classification for halves and pieces according to size is accomplished through screens of different sizes, and these are shown in Table 8.2. First, there are three broad categories, Halves, Pieces and Meal, and each is subdivided in Table 8.2 Size classification of pecan halves and pieces according to industry standards in the USA and equivalents in the metric system Category

Units

Nut halves Mammoth Jr. Mammoth Jumbo

per pound 200–250 250–300 300–350

per kilogram 440–550 550–660 660–770

Pieces Extra large Large Large/medium Medium Small/medium Small Midget

Screen size in inches 36/64 to 28/64 28/64 to 19/64 26/64 to 19/64 22/64 to 16/64 19/64 to 16/64 16/64 to 12/64 12/64 to 8/24

in mm 14.3 to 11.1 11.1 to 7.5 10.3 to 7.5 8.7 to 6.4 7.5 to 6.4 6.4 to 4.8 4.8 to 3.2

Meal Granule Meal

Screen size in inches 8/64 to 5/64 5/64

in mm 3.2 to 2.0 2.0

Source: The Green Valley Pecan Company (2010) (http://www.greenvalleypecan.com).

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smaller categories. For example, in descending order, nut halves are divided into Mammoth, Jr. Mammoth and Jumbo. Nut pieces are comprised by Extra Large, Large, Large/Medium, Medium, Small/Medium, Small and Midget. Finally, Meal can be either Granule or Meal. The count of units per pound of meat implies that the smaller the count, the bigger the kernel parts; therefore, the Mammoth class includes the biggest halves, while Meal includes the smallest particles, basically the finest pieces capable of going through a very small mesh.

8.5

In-shell and shelled pecans

Once harvested, pecans can be managed in-shell or shelled, depending on several factors as described below. 8.5.1 In-shell nuts Although the shell itself represents a good barrier for gas exchange, it does not prevent air from coming in contact with kernels and eventually triggering oxidation processes, leading to oil rancidity and skin darkening. It should also be taken into account that in-shell pecans use more storing space than shelled kernels, therefore in-shell pecans are less efficient in space use in the cold room and during transport. However, very often pure economic reasons are the sole basis to define if the nuts are to be shelled or not, since extra infrastructure is required, and that implies expensive facilities and equipment, as well as trained labor. Often, because individual growers do not have the resources or do not meet the volumes for a profitable cost/benefit ratio, cooperative associations are formed to make a more efficient investment. Otherwise the crop is sold to middlemen, with obvious disadvantages and repercussions for growers but without the need for further investment and the concomitant risks. Advantages associated with in-shell pecans include that they can be stored longer than shelled kernels, and that the shells are natural barriers protecting kernels from bruising and delaying kernel oxidation and rancidity (LSU, 2009), as mentioned before. 8.5.2 Shelled kernels If shelling is an option, then the nuts are sorted according to size and color and cracked open to harvest the meals, following specific schedules according to market demands. If shelling is not an option, then the nuts must be cold stored anyway to avoid quality deterioration, which, although slow, occurs anyway. Often, however, cold storage is not possible and rancidity will develop depending directly on temperature. It must be considered that shelled kernels become darker and develop red colorations quicker than in-shell pecans (Grauke et al., 1998). When temperatures are higher (warmer sites) rancidity develops quicker. Hence, the need for marketing such a crop is greater and the likeliness of getting a fair price declines drastically. From the sanitary standpoint, since shelled pecans are

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more likely to harbor pests like pecan weevil and others, avoiding transport of in-shell pecans must be part of any quarantine effort, making shelling part of an integrated pest control strategy.

8.6

Description of main quality attributes

Florkowski et al. (1992) acknowledged the complexity of communicating on quality issues in the pecan industry, so that standard grades could be related to quality attributes and prices. Quality pecans are defined by several factors, among the most important being kernel size and color, nutmeat-to-shell ratio, freedom from rancidity, and lack of defects, either physical or caused by insects. These factors, along with specific gravity and shell thickness, are useful not only to grade nuts but are also important factors for the design of handling and processing equipment (Kotwaliwale et al., 2004). Not restricted to processing, they have also been helpful in defining trait targets in breeding programs as well (Florkowski et al., 1992). Using direct gas chromatography (GC) as an objective measurement of several volatile compounds and a trained panelist to assess flavor scores as subjective variables, Forbus et al. (1980) reported that the best correlation coefficients were found when comparing flavor score vs. total volatiles (−0.95) and flavor score vs. tridecane levels (−0.93). Kernel size defines the best possible use for each product. While the biggest sizes are usually used to improve the visual appearance of the final product, the smallest are demanded for baking purposes, with a whole range of uses and demands for the intermediate sizes. Prices correspond accordingly. Kernel color is an indication of quality, since the darker colors are associated with rancidity development, the result of oxidation processes. Oxidation of endogenous leucoanthocyanidin to phlobaphe, cyanidin and delphinidin has been pointed out to be the cause of the red-brown discoloration of kernel testa (Senter et al., 1978). Kernel color is one of the parameters to estimate quality and value, before actual shelling and processing (Heaton et al., 1975), and a simplified color rating system, based on the Munsell Color System but with only six classes, was developed for the pecan industry (Thompson et al., 1996). When kept at room temperature, most color changes occur during the first 18 weeks (Kanamangala et al., 1999), therefore avoiding exposure to such conditions delays the onset of color deterioration. Kernel color transitions change from yellow to red hues and from lighter to darker values, although it changes very little in chroma. Color is also dependent upon genotype, and different years yield different colors for the same variety (Grauke et al., 1998). Therefore, environmental conditions during nut ripening, around harvest and after harvest have a decisive influence in color development. The warmer the temperature, the darker color the kernel develops. Higher elevations and latitudes (cooler temperatures) tend to produce light colored kernels, while the opposite occurs at lower elevations and latitudes where both day and night temperatures will be warmer. However, for the

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same latitude, elevation plays a key role in defining quality, and it is expected to find the lightest colored kernels at high elevations, but as a convenient trade off, lower sites may achieve an earlier ripening, as is commonly noted in Northern Mexico, where Western Schleys and Wichitas are grown along 28° NL, but with differences in elevation up to 1000 m. The nutmeat-to-shell ratio describes how much of the total crop is usable. It is the result of orchard management, as much as it is a genetic trait, and nuts from improved varieties have higher ratio than native trees, which are typically thickshelled and small. Also, careful management with appropriate technologies will result in bigger ratios. Although the current nut and kernel evaluation system was developed by the USDA-ARS, and it has been in use for decades to evaluate shelling efficiency, data suggest that there is still room for improvement and other variables should be taken into consideration (Thompson and Grauke, 2003).

8.7

Storage

An efficient strategy for pecan storage calls for a fast and effective drying after harvest, followed by cooling of nuts or kernels, in order to delay kernel quality deterioration (Heaton et al., 1982), regardless if the crop will be shelled or not. In general, benefits of low temperature storage are a better retention of fresh flavor, followed by color, aroma and texture (Herrera, 2005). A brief description of some of the recommended practices follows. 8.7.1 Nut moisture content Nut moisture content during harvest is in the order of 24%, and it should be lowered to 4%, since a 6% water content may lead to mold development and the nuts do not store well (Herrera, 2005; LSU, 2009). Besides the regular gravimetric methods to determine water content, pecan kernel moisture has also been measured by rf-impedance methods with promising results (Nelson et al., 1992). To achieve appropriate moisture content, growers may artificially induce nut dehydration by means of adding heat and dry air. When nuts are harvested early in the season, this practice is a must and is commonly done in processing facilities. However, without access to such infrastructure, a common practice is letting the nuts dehydrate while still on the tree, which leads to a late harvest season. Depending on whether this may pose a risk, since losses of quality are inherent. For example, Heaton et al. (1982) when comparing Stuart, Wichita and Schley nuts harvested in late season, found no color differences on these cultivars, but the latter has less flavor stability. 8.7.2 Appropriate temperature and humidity Having access to pecan samples stored in hermetically sealed containers for 25 years at 20 °C, Hao et al. (1989) were able to compare them with nuts kept

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under the same conditions but for only ten months. They evaluated sensory, microbial and compositional characteristics, finding that the only significant change was in texture, concluding that pecan can be stored for up to 25 years under those particular conditions. However, achieving those conditions is both difficult and costly for the industry, and appropriate adjustments must be done under commercial conditions. Studying changes in pecans stored at 0.6 °C and 75% RH for 12 months, Yao et al. (1992) did not detect changes in kernel color, oil quality, tocopherols nor conjugated diene levels. Color changes in kernels frozen for up to a year were followed by Grauke et al. (1988) finding that, compared with unfrozen controls, frozen kernels were more red in hue but could not be distinguished on the basis of lightness; also, samples frozen for 12 months had reduced chroma compared to those frozen for six months or unfrozen. Present knowledge leads extension programs to advise that in-shell pecans can be stored for longer periods than shelled nuts, because of the shell protective effect. Also, native pecans storage life can be extended from three months at 21 °C up to eight years at −18 °C (LSU, 2009). Varieties like Western Schley can be kept at 21 °C for up to four months when in-shell, but only three months when shelled, but no difference were found at −18 °C lasting between two and five years (Herrera, 2005). Differences like those may be attributed to unsaturated oil contents, which along with temperature and moisture content are the main factors defining storability (Herrera, 2005). Nonetheless, other conditions should be taken into account, like the fact that pecan pieces have shorter shelf life than halves because of their larger surface/size ratio. As a result, nutmeats may be expected to last only for one or two months at 0 °C (Herrera, 2005). 8.7.3 Packaging materials Refrigerated or frozen pecans should be placed in airtight containers (LSU, 2009). Since shells are a natural barrier protecting kernels from oxidizing faster, very often the situation calls for storing shelled kernels, which requires packaging materials of specific conditions. Dull and Kays (1988) found that kernels packaged in polyvinylidenechloridecoated cellophane packaging films with low oxygen transmission rates were of acceptable quality after six months storage at 24 °C and 60% RH. Later Kanamangala et al. (1999) found that reducing fatty acid content of kernels by partial lipid extraction, resulted in a longer shelf life. They assumed that in addition to decreasing the total amount of lipid available for oxidation, the free fatty acid lipid component that correlated with the development of rancidity was reduced by extraction, most likely the linoleic fraction (Herrera, 2005). Although interesting from the analytical standpoint, implementing a strategy like this would represent an extra task that industry must consider. Using either polypropylene plastic containers or nylon-polyethylene plastic films under vacuum, Oro et al. (2008) evaluated kernels at 23 °C for up to 150 days without significant differences between the two packages. Shelf life was estimated at 120 days, although kernel darkening was detected.

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8.8

Postharvest physiology factors affecting nut quality

8.8.1 Respiration Pecans, like all nuts, have a very low respiration rate [about 1 mL kg−1h−1 at 10 °C] (Kader, 2002; Kader et al., 2010), as dormant embryos metabolism is very low, a situation accentuated when they are artificially dehydrated after harvest. Therefore, their shelf life is not threatened because of respirationdependent anabolic reactions, but because of the lipid oxidation process leading to rancidity and skin darkening (Senter and Hdrvat, 1976; Florkowski et al., 1992; Toro-Vazquez et al., 1999; Herrera, 2005).

8.8.2 Color Kernel color is one of the most important quality attributes and develops once shuck dehiscence starts (Kays and Wilson, 1977). Kernel darkening is associated with oxidation of oils (Woodroof, 1979) and rancidity development of free fatty acids (Oro et al., 2008). The seed testa, another designation for the kernel surface, may also become dark when shucks fail to open because of mechanical damage and insect injuries, particularly those caused by sucking insects like stink and coreid bugs, whose bite can penetrate through shells (Yates et al., 1991). There are varietal differences in hemipteran kernel damage susceptibility, but interestingly, it is the females that cause most of the injuries (Dutcher et al., 2001) and dark spots develop around the feeding site. Conditions during late harvests favor kernel darkening and to avoid such problem spraying with ethylene-liberating products in conjunction with auxins used after endosperm filling cause the shucks to open allowing uniform harvests without deleterious effects on foliage (Martínez-Téllez et al., 1995).

8.8.3 Rancidity As mentioned before, along with darkening, rancidity is the other major issue causing pecan quality deterioration. Both are the result of oxidation processes. In the first case is the oxidation of leucoanthocyanidins in kernels (Senter et al., 1978), while rancidity develops when pecan oils are oxidized (Toro-Vazquez et al., 1999). Because pecan oil is so rich in fatty acids (Santerre, 1994), particularly linoleic acid (Villarreal-Lozoya et al., 2007), this makes it particularly susceptible to becoming oxidized, thus getting rancid (Herrera, 2005). Oxidation of unsaturated fatty acids results in the development of undesirable aromas and flavors as well; when this occurs nut shells will have a dark and oily appearance. Peroxide content is the major variable used to measure rancidity and most standards call for a peroxide index value 60% of production), Japan, Korea, Brazil, Italy, Spain, Israel and Turkey, with over 90% of world production in Asia. Production is increasing in countries such as China, Korea, Brazil and Spain. 9.1.3 Culinary uses, nutritional value and health benefits Consumption is mostly in Asian countries where the sweetness, subtlety of flavour and lack of acidity is (generally) more appreciated. Persimmons can be consumed

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fresh, are rarely used in cooking, or may be consumed dried. Drying fruit is the main form of processing, but is generally labour intensive, since fruit must first be peeled, then hung to dry. Astringency is lost as fruit ripen, or they can be treated to remove astringency rapidly after harvest (e.g. CO2 treatment, see later). There is a return of astringency when the latter are subjected to heating, or cooked. The high contents of tannins, polyphenols, carotenoids, ascorbic acid and sugars indicate the high potential for health benefit from persimmon consumption, and these compounds have been the subject of intensive study in the last decade. Although clinical studies still need to be conducted, diseases that are considered likely to benefit from persimmon ingestion are cardiovascular, high cholesterol, diabetes, cancer, stroke and even intoxification effects (see review of George and Redpath, 2008). The greater antioxidative activity of high versus low molecular weight tannins might indicate that astringent cultivars are likely to have superior health benefits (Gu et al., 2008), but the effect of removing astringency has not been studied in this respect. The re-solubilisation of polymerised tannin under simulated stomach conditions might make such a study superfluous. It should also be noted that this re-solubilisation might be a reason for caution in consuming excessive amounts of fruit that have had their astringency artificially removed, since the formation of phytobezoars may occur under certain conditions.

9.2

Fruit development and postharvest physiology

9.2.1 Fruit growth, development and maturation Generally, the growth, development and maturation of persimmon fruit do not differ substantially from those of most fleshy, climacteric fruit, be they from temperate deciduous trees or evergreen subtropical and tropical trees. They exhibit a double sigmoid growth curve, whether seeded or parthenocarpic, and demonstrate typical colouration and softening once they complete their growth cycle and begin to mature and ripen. A very comprehensive review of the development of nonastringent persimmons is also relevant for the astringent types (George et al., 1997). Special attention has been paid to the involvement of the calyx lobes in fruit growth and development (Yonemori et al., 1996). Removal of the calyx during stage I of the growth cycle inhibited fruit growth, indicating the importance of the contribution of assimilates produced in this organ. However, at stage III, fruit growth remained unaffected by calyx detachment, unless the scar was sealed with Vaseline®, in which case fruit growth rate decreased. Apparently, this decrease is due to inhibition of fruit respiration, which was shown to be necessary for photo-assimilate accumulation during the final fruit swell at growth stage III, required to maintain the sink strength of the fruit (Nakano et al., 1998). A unique feature of the persimmon fruit is the abundance of specified tannin cells and the varietal differences in their morphology and metabolism, resulting in the four distinct groups described above. Non-astringent cultivars contain fewer and smaller tannin cells than astringent cultivars (Itoo, 1986), have different cell wall characteristics (Gottreich and Blumenfeld, 1991; Yonemori and Matsushima,

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1987), colour and shape (Yang et al., 2005). However, the PCNA group has been developmentally distinguished from the other three groups, with regard to its tannin content. Whereas in the latter the tannin content increases during stages I and II of fruit growth, in PCNA-type fruit its accumulation ceases during stage I and the tannin concentration therefore declines as the fruit continues to grow, resulting in a loss of astringency. Moreover, the tannin composition of PCNA fruit differs in that it does not coagulate in the presence of acetaldehyde. The loss of astringency in PVNA-type cultivars is related to the presence of the seeds that produce acetaldehyde and ethanol, thus causing a coagulation of the tannin, even before the fruit ripens. The PCNA-type cultivar is supposedly a recessive mutant of the astringent type and the cessation of condensed tannin accumulation at stage I of fruit development in these cultivars was shown to coincide with the gradual disappearance of DNA sequences of nine genes involved in flavonoid biosynthesis (Ikegami et al., 2005). 9.2.2 Respiration, ethylene production and ripening The ripe persimmon produces extremely low levels of ethylene (peaks below 5 nL g−1 h−1) and because of this, its climacteric status was initially questioned (Takata, 1983). The issue was more or less resolved when it was shown that postharvest fruit softening and colouration were accompanied by ethylene synthesis (Itamura et al., 1991). In the last decade, a number of molecular studies have demonstrated the involvement of the ethylene biosynthetic pathway and signal transduction in persimmon fruit ripening (Ortiz et al., 2006; Pang et al., 2007; Zheng et al., 2005). 1-MCP (a potent inhibitor of ethylene action that binds to the ethylene receptor site and applied commercially as SmartFreshSM) has been a valuable tool in elucidating the climacteric nature of the persimmon (Harima et al., 2003; Luo, 2007). The initiation of pseudo-climacteric ethylene production in detached young fruit (stage I) and in ripened mature fruit was shown to occur in the calyx, being modulated by water stress (Nakano et al., 2002, 2003). A water stress signal activates the expression of one of the three ACC-synthase genes (Dk-ACS2) in the calyx and the ethylene produced diffuses to the other fruit tissues, inducing autocatalytic ethylene production in the fruit by stimulating the expression of all three AC-synthase and two ACC-oxidase genes. Inhibition of ethylene production in the calyx by preharvest application of nickel, delayed ACC accumulation in the fruit, reduced on-tree fruit softening and prolonged the postharvest life of ‘Saijo’ persimmons by retarding softening (Zheng et al., 2006b). Other stresses that induce climacteric ethylene production, but without calyx involvement, are de-astringency treatments and wounding. Wounding also induces Dk-ACS2 expression, which is stimulated by 1-MCP, indicating a negative feedback response to ethylene (Zheng et al., 2005, 2006a). Ethylene perception and signal transduction in persimmon have been studied in relation to the expression of three ethylene receptor genes: Dk-ETR1, Dk-ERT2 and Dk-ERS1 (Pang et al., 2007). Dk-ETR1 is constitutive at a low basal level and independent of ethylene, although probably responsible for its perception.

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Dk-ETR2 and Dk-ERS1 appeared to be regulated by ethylene during fruit development and ripening and were enhanced in response to exogenous ethylene, indicating a possible role in autocatalytic ethylene production, especially for Dk-ERS1, which was much more abundant than Dk-ETR2. This recent study suggests a possible answer to the question of differences in the ripening behaviour and sensitivity to ethylene between persimmon types and cultivars, which has so far not been addressed.

9.2.3 Cell wall metabolism and softening Persimmon fruit softening is associated with middle lamella degradation, loss of cell wall material, and cell wall separation (Shin et al., 1991). These cell wall changes result from the increasing activity of cell wall degrading enzymes common to most fleshy fruit: pectin methyl esterase, polygalacturonase, β-galactosidase and cellulase. These cause a reduction in high molecular weight carbohydrate polymers (pectin, hemicelluloses, and cellulose) and increases in soluble pectic fractions and neutral sugars. The direct involvement of these changes in fruit softening has been demonstrated by the inhibited softening incurred by gibberellins (Ben-Arie et al., 1996), 1-MCP (Luo, 2007) and heat treatment (Woolf et al., 1997; Luo, 2006), as opposed to ethylene-accelerated softening (Chang et al., 2009). However, in rapidly softening ‘Saijo’ fruit, α-L-arabinofuranosidase activity was more closely related to softening than that of the other hydrolases (Xu et al., 2004). This might possibly be a response to the CO2 treatment, since no comparison has been made between natural softening and that induced by artificial removal of astringency. Cell wall metabolism may also contribute to the natural loss of astringency concomitant with softening, because of complex formation between soluble tannin and solubilised cell wall fractions (Taira et al., 1997).

9.3

Maturity, quality at harvest and phytonutrients

9.3.1 Maturity and quality at harvest The most obvious feature of persimmon fruit maturation is the change in colour from light orange/yellow to deep orange and on to red, the result of chlorophyll degradation and carotenoid biosynthesis. The principal carotenoids are initially β-cryptoxanthin, zeaxanthin, antheraxanthin and violaxanthin (Ebert and Gross, 1985; Niikawa et al., 2007). The change to red is due to lycopene accumulation, especially after harvest. Its occurrence in fruit on the tree might be a good harvest index. However, the best objective method for assessing fruit maturity is the Hunter a value, although the Delayed Light Emission method might be more suitable for automated mechanical fruit sorting (Forbus et al., 1991). Chemical changes accompanying fruit maturation that contribute to the taste of the ripe fruit are sugar accumulation, acidity and a decline in soluble tannin. The

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predominant sugars, in almost equal amounts, are glucose, fructose and sucrose, which increase throughout fruit development, reaching a constant level prior to harvest maturity. During postharvest ripening, the reducing sugars continue to increase due to invertase activity (Zheng and Sugiura, 1990), and a concurrent decline in sucrose levels (Del Bubba et al., 2009). Acidity in persimmons is relatively low even in immature fruit (c. 1%), but does not change with ripening. Malic acid, which is predominant, increases with maturity, accompanied by a decline in citric acid (Senter et al., 1991). Succinic, fumaric, isocitric, ascorbic, gallic and quinic acids have also been identified (Daood et al., 1992). The polymerisation of tannin during maturation of PVNA cultivars is evidently due to the production of ethanol and acetaldehyde by the seeds (Yonemori and Tomana, 1983), but in PCNA cultivars the early decline in soluble tannin is as yet unexplained, although the different tannin composition (Suzuki et al., 2005) is probably involved. Tannin polymerisation also accompanies maturation of astringent cultivars, but at values of around 1% at maturity, the fruit are still highly astringent (Del Bubba et al., 2009; Taira, 1996). A possible explanation for this decline in soluble tannin might be the formation of a glycoside with soluble sugars, proposed to occur during treatment with CO2 (Ittah, 1993). The constant concentration of total sugars maintained when fruit growth ceases might indicate that part of the products of increased invertase activity interact with the soluble tannin. Fruit softening is characteristic of maturation for many fruit species and a measure of firmness can be used as an index of maturity, as a criterion for when to harvest. In general, this is also true for many persimmon cultivars (Salvador et al., 2006). However, with a number of cultivars, fruit firmness as measured with a penetrometer (Magness-Taylor) has been found to be less related to maturity than is the Hunter a colour (Del Bubba et al., 2009; Forbus et al., 1991). Other modes of assessing firmness, such as an impact (Sinclair IQ Firmness Tester) or acoustic (Aweta Firmness Sensor) response, have been found to correlate better with perceived ripeness or postharvest keeping quality. 9.3.2 Phytonutrients Phytonutrients in persimmon include, in addition to the sugars, vitamins and fibre content characteristic of most fruit, large amounts of condensed tannins, polyphenols and carotenoids (Gorinstein et al., 2000), which contribute to the high antioxidative potential of these fruit. High molecular weight tannins have a greater antioxidative activity than low molecular weight tannins (Gu et al., 2008; Kondo et al., 2004), but the effect of removing astringency on antioxidative activity is not known. Maturation and ripening are associated with a reduction in polyphenol content, which might lead to a reduced antioxidant potential. Conversely, the increase in the carotenoid content associated with ripening is likely to raise it. Although varietal differences have not generally been addressed, non-astringent cultivars were found to have higher levels of vitamins A and C than astringent cultivars (Homnava et al., 1990).

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9.3.4 Taste Persimmon overall has a subtle taste with little or no acidity and the aroma is not strong compared with that of many fruit species. Fruit with good sun exposure will tend to have best flavour (higher SSC and more volatiles/flavour). The two most important taste aspects tend to be sweetness and astringency. Higher levels of sweetness are generally preferred by consumers, and warmer growing environments will result in higher SSC content (up to or above 20%; Cristosto, 2004), while fruit in cooler environments may struggle to achieve an average of even 15% (Mowat and Collins, 2000). In astringent-type persimmons under prolonged MA storage that enables loss of astringency, flavour can become bland if CO2 levels in storage are low, or develop off-flavours if CO2 is too high. In non-astringent persimmons, a possible negative attribute that can affect repeat sales is that of ‘residual astringency’. The key factor that affects this appears to be the fruit temperature during development (Mowat and Collins, 2000), particularly during the period of 10–14 weeks after full bloom (Chujo, 1982; Jackman and Woolf, unpublished data).

9.4

Preharvest factors affecting postharvest fruit quality

9.4.1 Minerals – nutrition Studies conducted with a non-astringent cultivar (‘Fuyu’ in New Zealand) and with an astringent cultivar (‘Triumph’ in Israel) have not indicated any apparent postharvest effects of mineral status of the fruit at harvest (although the New Zealand study did not include nitrogen in the analysis). This could, however, be the result of specific environmental effects on the mineral composition and/or physiology of the fruit, since the same cultivars grown in Brazil, Spain and Australia were found to respond to preharvest calcium by producing firmer or higher quality fruit (Agusti et al., 2004; Ferri et al., 2008) and Redpath et al. (2009) found a correlation of leaf calcium content and postharvest softening rate. The keeping quality of coolstored ‘Fuyu’ was improved by preharvest sprays of calcium chloride or nitrate (0.5%) and boron (0.3%), because of reduction of skin cracks, and browning (Ferri et al., 2008). Application of 2% Ca(NO3)2 to astringent ‘Triumph’ fruit before colour break retarded colour development, fruit softening and ethylene production and reduced postharvest fruit softening and deterioration. However, the incidence of soft-blossomend fruit, which appeared to be related to low calcium levels, was not affected by orchard sprays of calcium nitrate throughout the growing season (Ben-Arie et al., 2008). Repeated heavy foliar application of calcium sprays in New Zealand was not found to reduce chilling injury following storage (Woolf and colleagues, unpublished data). Convincing data as to the ability of cultural practices to affect the mineral composition and postharvest quality of persimmon fruit are scarce. 9.4.2 Plant growth regulators The objective of preharvest application of plant growth regulators is to control fruit maturation or improve postharvest ripening and quality. Advanced maturation

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has been achieved by applying paclobutrazol (a gibberellin synthesis inhibitor), abscisic acid, ethychlozate or methyl jasmonate (presumably by stimulation of ethylene synthesis) and ethephon (an ethylene-releasing compound). These treatments enable earlier harvesting because of enhanced growth rate and fruit colouration, but may also accelerate the postharvest softening rate. This practice may be useful where limited storage/shelf life is acceptable (i.e. early season local or airfreight export markets). Paclobutrazol has been applied commercially with success, care being taken not to delay harvest from treated trees. It is applied to the soil in the spring, immediately retarding vegetative growth and the effect can last for 2–3 years. Conversely, delayed maturation is achieved by spraying GA3 (30–50 mg L−1), 10–20 days before harvest. Colour development and fruit softening are retarded, but the chief advantage of this treatment is an extended storage and shelf life. It is necessary to determine the optimum dose for each cultivar, since, although increasing the dose enhances the effect, it may be detrimental to fruit size and especially to the return bloom in the subsequent year. A similar effect can be obtained by spraying the cytokinin CPPU at a low concentration (2–10 mg L−1, ten days after full bloom (DAFB)). Combined with girdling, final fruit weight could be improved (Hamada et al., 2008). However, to the best of our knowledge, this treatment has yet to be adopted commercially. The delayed maturation induced by GA3 has been shown to increase the carbohydrate content, chiefly cellulose, together with reduced activity of PG and cellulase during fruit softening (Ben-Arie et al., 1996, 1997). It also reduces the rate of fruit respiration (Nakano et al., 1997) and the sensitivity of the fruit to ethylene ten-fold. 9.4.3 Climate and environment The persimmon is generally regarded as a crop that is highly adaptable to many soil types and conditions, as well as to a wide range of climatic conditions. Sunburn and abrasions caused by wind are easily recognised and can be dealt with to some extent, using appropriate training methods, wind-breaks (trees or artificial netting) and other methods of protection, such as net-houses or covering. Astringency is the most obvious of the fruit characteristics that is affected by climatic conditions during fruit development. As noted above, non-astringent cultivars require warmer conditions than astringent cultivars for maturation and may not lose their astringency when grown under relatively low temperatures (Mowat et al., 1997). On the other hand, excessively high temperatures may be detrimental to fruit size, partly because of accelerated maturation. Fruit can be susceptible to sunburn in mid-summer, particularly following pruning or leaf thinning. However, although net covering in a hot climate reduced the daily temperature and somewhat delayed maturation (chiefly because of a delay in colour development), it did not increase fruit size, which is positively affected only by increasing irrigation in both open and net-covered orchards. Nonetheless, net covering produced higher quality fruit because of reduced sunburn and wind abrasions, in addition to reduced bird damage (Ben-Arie et al., 2008).

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Canopy management contributes significantly to overall fruit quality. In a review of Australian persimmon management practices, Nissen et al. (2003) reported that in Australian orchards, trellised trees produce higher yields of marketable fruit than do other training systems. Trellising increased planting density, improved light interception, and structures that stabilised the tree significantly reduced fruit blemishes. Light exposure of the fruit has an effect on fruit temperature (Mowat, 2003). In Japan, Takano et al. (1991) reported that the level of light exposure had a greater effect on fruit weight, colour and soluble solids content than did crop load. Exposed fruit had higher colour and lower soluble tannins than unexposed fruit in the mid-canopy in New Zealand ‘Fuyu’ (Mowat, unpublished data). Specific leaf weight is useful as an indicator of light conditions in ‘Fuyu’ canopies in New Zealand orchards, where higher values were correlated with improved fruit quality (Mowat, 2003). 9.4.4 Calyx separation In some cultivars and growing conditions, calyx separation or ‘calyx cavity’ develops (Glucina, 1987). This disorder occurs late in the season, during the final phase of the double sigmoidal growth curve. It is thought that the fruit expands faster than the calyx, and this results in the flesh separating from the calyx tissue, resulting in potentially large gaps (up to 5 mm or more), which may even encircle the whole calyx. This leads to more rapid softening of non-stored persimmons and increased levels of chilling injury in stored fruit. Thus, commercial recommendations are to remove these fruit during packing, although detection of all but the most severe disorders can be difficult. These cavities also provide a refuge for insects such as caterpillars, mealybugs and even earwigs. The problem is more common in ‘Fuyu’, but less so in some other cultivars such as ‘Triumph’ and ‘Suruga’. Larger fruit are more likely to have calyx separation, probably because of the greater fruit expansion. It is considered to occur more on young trees, and generally declines after about 15 years. 9.4.5 Skin cracking/black blotch An additional practical and economic challenge to persimmons is the propensity for the occurrence of large or small cracking (‘crazing’) of the skin. This can occur as ‘ring cracks’ around the fruit, most often at the distal end, or as discrete brown/black patches on the skin (‘black stain’, Fumuro and Gamo, 2001; or ‘black blotch’, Woolf et al., 2008). Depending on market requirements, these may or may not be acceptable. Large cracks are evident at harvest, but smaller cracks may only become evident after harvest, or during storage, although the actual cracking is most likely to have occurred preharvest during the final stage of fruit growth (Chujo et al., 1982; Woolf et al., 2008). Factors that may increase this problem are rainfall or presence of seeds, both of which lead to increased fruit expansion, presumably placing more stress on the skin. The resulting cracks may be visible to the naked eye or microscopic (Woolf et al., 2008), and it is the latter

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ones that are likely to blacken after harvest or during storage. Thus, orchard management systems that avoid damage to the fruit skin (e.g. avoiding leaf contact with fruit; Woolf et al., 2008) or fruit bagging prior to harvest (Fumuro and Gamo, 2001) ensure development of continuous wax layers that will improve packout and final fruit quality.

9.5

Postharvest handling factors affecting fruit quality

Although there are significant differences between countries and cultivars, the maximum storage life of persimmons is generally in the order of 12–16 weeks. Typically this will only be achieved by use of a combination of treatments (such as optimised temperature, 1-MCP and MA storage) to overcome softening and/or chilling injury problems. The final limitation to long-term storage will typically be external quality due to skin browning, excessive softening or disease incidence. 9.5.1 Temperature management The standard recommended storage temperature is 0 °C (Crisosto, 2004; MacRae, 1987), and some countries recommend even lower temperatures such as −1 °C (Israel). Higher temperatures (3–8 °C) lead to increased chilling injury in ‘Fuyu’ (Collins and Tisdell, 1995), and at 5–15 °C for other cultivars (Crisosto, 2004). Since maintaining temperatures around or below 0 °C is important, determining the freezing point can be an important step in commercial temperature management. Crisosto (2004) suggests a freezing point of −2 °C and we have found freezing points as high as −1.25 °C (New Zealand) or as low as −3.2 °C (Israel), the variation being probably attributable to SSC level. 9.5.2 Physical damage An important problem with persimmons is that any puncturing or damage to the skin results in blackening that is very evident to consumers on the orange-red skin. Aside from the obvious deleterious visual effect, such damage can promote rots during storage. In some cultivars, bruising appears not to be important (‘Fuyu’ in New Zealand), but in other cultivars (‘Triumph’), careful handling at and after harvest is of major importance, to avoid the occurrence of blackened tissues beneath the skin. Fruit that have been treated with CO2 to remove astringency are especially susceptible. Therefore, the commercial recommendation is to pack the fruit prior to de-astringency treatment. 9.5.3 Water loss Unlike many crops, weight loss is not a key factor for persimmons, probably because little water loss occurs through the skin (Perez-Munuera et al., 2009), but

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Fig. 9.1 The relationship between weight loss, fruit shrivel and Alternaria decay development on ‘Triumph’ persimmons, after 14 weeks storage at −1 °C and RH levels ranging from 70 to 100%.

low RH can cause fruit shrivelling. For example, ‘Triumph’ fruit showed a linear relationship between increase in weight loss during storage and RH (Prusky et al., 1981), and the percentage of shrivelled fruit was unacceptable above 5% loss in weight, which occurred at 85% RH after 14 weeks at −1 °C (Ben-Arie and Prusky, unpublished data, Fig. 9.1). From the point of view of decay development, increased weight loss was accompanied by reduced infected area, so that optimum quality was achieved with 3–5% weight loss at 85–90% RH. However, maintenance of 90 to 95% relative humidity (RH) during storage has also been recommended (Crisosto, 2004). In terms of weight loss from the fruit, both before and during storage, no significant impacts on chilling injury have been noted for ‘Fuyu’ (Woolf, unpublished data). Softening of the tissue beneath and around the calyx after prolonged storage could possibly arise indirectly from water loss by the calyx lobe, which has been shown to trigger ethylene production (Nakano et al., 2002, 2003), as described above. Where there are cracks or punctures of the skin, water loss occurs more rapidly during storage and shelf life, and thus some shrivelling and sinking of tissue can become evident. In non-damaged fruit, the key area where weight loss may be commercially important is in the appearance of the calyx, where drying and browning of the green leafy tissue may affect retailer and consumer perceptions of freshness. 9.5.4 Atmosphere Controlled atmosphere (CA) storage Storage under low O2 of 2 to 5% delays ripening, and CO2 at 5 to 10% slows softening and can reduce chilling injury (CI) symptoms (Crisosto, 2004; Burmeister et al., 1997; Tanaka et al., 1971). The upper tolerable concentration of CO2 appears to be between 10% (Crisosto, 2004) and 20% (Haginuma, 1972),

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although there clearly are cultivar differences. Excessive exposure can result in skin browning and/or flesh browning beginning in the fruit centre. CA storage of the astringent ‘Triumph’ has the triple benefit of delaying fruit softening, retarding decay development and, if extended beyond three months, removing astringency (Guelfat-Reich and Ben-Arie, 1976; Guelfat-Reich et al., 1975). The atmosphere required to achieve these advantages is 1.0–1.5% O2 and 1.5–3.0% CO2. At higher CO2 levels, Alternaria decay control is improved, but fruit softening is enhanced and at >5% CO2, internal flesh browning occurs. The disadvantage of long-term CA storage (exceeding three months) is the very short subsequent shelf-life, due to rapid fruit softening. Below 1.0% O2, ethanol and acetaldehyde accumulation are excessive and off-flavours develop after three months at −1 °C, although astringency is completely removed (Ben-Arie, unpublished data). ‘Rojo Brillante’ storage life was extended to 30 days at 15 °C under CA (3% O2, 97% N2) because of delayed softening, thus circumventing CI, also with removal of astringency (Arnal et al., 2008). In this case, increased CO2 was of no additional benefit. Modified atmosphere storage Use of modified atmosphere (MA, or MAP) is common commercial practice in Korea, Japan and New Zealand (Kim and Lee, 2005; Kawada, 1982; MacRae, 1987). Fruit are heat-sealed in a 60-μm polyethylene (PE) bag, which generates an atmosphere of approximately 0.5–1.5% O2 and 4–8% CO2 (MacRae, 1987; Kim and Lee, 2005) and this delays and ameliorates CI symptoms, but does not eliminate them. Fruit of an entire tray (e.g. 4–10 kg) tend to be stored in one bag, but individual fruit-bags, or fruit in lots of 3–5, may also be used in Japan. An additional benefit of the MA bag system is that fruit are maintained in the MA environment during storage at the packhouse facility, during shipment/ transport (e.g. seafreight container), and during the steps through the wholesale and retail chain. This has a range of advantages other than the continual MA atmosphere, including reduced temperature fluctuation, avoiding condensation and improved food safety. A key commercial challenge is the reliability of bagsealing, where even one pin-prick sized hole can compromise the MA atmosphere and result in chilling injury development. In addition, once sealed in the MA bag, exposure to higher temperatures than the target storage temperature may result in reduced O2 and elevated CO2 concentrations, which may damage fruit (‘glassy ring’ and calyx abscission). Ethylene Persimmons are climacteric and sensitive to ethylene and thus exposure to ethylene results in increased rates of softening and reduced storage and shelf life, and therefore marketability (Takata, 1983; Krammes et al., 2005; Park and Lee, 2005; Besada et al., 2010). Besada et al. (2010) examined the effect of a wide range of concentrations and durations of ethylene exposure on shelf and storage life of ‘Fuyu’ in simulated air (non-stored) and seafreight (MA-stored) commercial scenarios. Exposure of fruit at 20 °C for one day, at even 0.2 μL L−1, resulted in

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an increased softening rate (non-stored fruit). If fruit were stored under MA for seven weeks after treatment, chilling injury was increased with ≥1 μL L−1 for 1 d, and slightly increased with ≤0.5 μL L−1 for 2 d. However, ethylene exposure of MA packed fruit during storage (0 °C), at either the beginning or end of the storage period, had either little or no influence on chilling injury (even with exposure times of seven days at 10 μL L−1). The lack of response of ‘Fuyu’ persimmons at low temperature is supported by results with ‘Triumph’, which (although this cultivar is not sensitive to CI), can be stored at −1 °C with ethylene levels up to 5 μL L−1, without any softening effect. Other treatments that will ameliorate the effects of exogenous ethylene are 1-MCP treatment. Krammes et al. (2005) showed that fruit treated with 1-MCP (0.1 and 1.0 μL L−1) were less responsive to even continuous exposure to ethylene (0.1 or 3 μL L−1) at 23 °C. Thus, although eliminating ethylene exposure before storage is critical, exposure during storage may be less important. However, Neuwald et al. (2009) reported benefits of ethylene scrubbing in terms of softening and skin browning under long-stored MA conditions. Thus, clearly commercial best practice is to minimise ethylene concentrations during storage. Anoxic tolerance of persimmons A remarkable characteristic of persimmons is their ability to tolerate nearcomplete anoxia (Tanaka et al., 1971). Storage of persimmons in flowing nitrogen (10 mm diam.), evident to the retailer at removal from storage. Rots caused by Botrytis cinerea, a wound parasite, can develop at three different sites on the fruit (Woolf et al., 2008). ‘Apex punctures’ that occur during harvest or handling due to puncturing of the skin by the ‘apex spike’ (the hard structure present at the stylar end of the fruit), enable fungal penetration. The apex spike itself can become infected

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(during flowering) and these infections develop into rots during storage. ‘Calyx rots’ (around the calyx end of the fruit) occur sporadically and we have also found these to be caused by Botrytis cinerea. Keeping the amount of Botrytis inoculum low in orchards during the growing season is key to reducing the potential for storage rots. In addition to the postharvest impact of Botrytis, infection of the petal tissue at flowering can lead to cosmetic marking of the skin that causes rejection at packing. Postharvest treatments using a hot water drench at approximately 55 °C have been shown to be effective for control of postharvest diseases in long-stored ‘Fuyu’ (Woolf et al., 2008), and similar treatments (hot water brushing) are effective on ‘Triumph’ (Ben-Arie, pers. comm.). Other causes of decay in persimmons according to Crisosto (2004) and Palou et al. (2009) are Cladosporium, Colletotrichum, Mucor, Penicillium, Phoma and Rhizopus. Many of these infections take advantage of wounding or microscopic damage to the skin (e.g. Mucor, Kwong et al., 2004).

9.8

Insect pests and their control

Insects are a significant problem for persimmons, which can host fruit fly in the subtropics, and are readily infested in temperate environments by a wide range of other pests, such as caterpillars, thrips, mealybug and scale. There is also a wide range of insects that cause significant preharvest problems, but may not be a significant problem from a postharvest perspective (e.g. various stink bugs: Halyomorpha halys, Plautia crossota stali, Riptortus clavatus, Son et al., 2009; and cut worms, Choi et al., 2008). 9.8.1 Fruit fly Fruit flies are important fruit pests that attack several cultivated species of high commercial value in subtropical and tropical areas of the world. Three species are prevalent on persimmon in different growing regions: the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), the Mexican fruit fly, Anastrepha ludens (Loew) and the oriental fruit fly, Bactrocera dorsalis (Wendel). Because of the continuity of hosts and the relatively short life cycle of the pests, their control is difficult and fruitgrowing regions that are infected have developed regional protocols for dealing with the problem. These include detailed recommendations for sanitation, weekly monitoring, pesticide-bait spray programmes, release of sterilised males and traps to kill. Sanitation recommendations include total removal and disposal of fruit from the trees and orchard ground after harvest. Monitoring with traps containing the attractant trimedlure begins around the time of colour break. Bait sprays are frequently applied from aircraft and supplemented with spot spraying in the orchards. In recent years an effective and environmentally friendly insecticide, Conserve®-SC (Spinosad; Dow AgroSciences), has replaced the organophosphate malathion as a bait spray (Stark et al., 2004). The dispersal of sterilised males is increasing and new traps to attract

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and kill have been developed. In Hawaii a multi-lure trap (three attractants) with soapy water or sticky boards to kill, and in Israel two traps – Biofeed® and Protect® – based on attractant yellow boards, bait and Spinosad, are available. In the event that a combination of all treatments is not sufficiently effective and larvae are found in infected fruit, cover sprays with the organophosphate diviphos are recommended to achieve eradication (Thomas et al., 2007). Quarantine regulations in some persimmon importing countries are very strict, with zero tolerance. Cool storage at below 1 °C for two weeks kills all stages of the fly and is generally suitable for most cultivars. For chilling-sensitive astringent cultivars, it is possible that the high CO2 treatment at a high temperature to remove astringency could also be effective. 9.8.2 Other insects In more temperate environs, the most important pests of persimmon include mealybug (e.g. Pseudococcus longispinus, P. viburni, P. calceolariae and Phenacoccus graminicola) and various leafroller and other caterpillar species (e.g. Ctenopseustis obliquana, C. herana, Cnephasia jactatana, Planotortrix octo, Stathmopoda skelloni, Sperchia intractana and the lightbrown apple moth – Epiphyas postvittana). Postharvest treatments for such species include cold disinfestation and heat treatments either by hot air (Dentener et al., 1996) or hot water (Lee et al., 2008). Other important insects include thrips (e.g. Heliothrips haemorrhoidalis, Nesothrips propinquus) and scale insects (e.g. Hemiberlesia rapax, Hemiberlesia lataniae, Aspidiotus erii, Ceroplastes pseudoceriferus and Phenacoccus aceris). Scale insects can infest fruit or calyx, and where this occurs, it tends to result in an indentation in the fruit. Finally, various mites may also be an issue (e.g. Aceria diospyri, Oribatidae, Tetranychus urticae (TSM), Orthotydeus californicus and O. caudatus). 9.8.3 Passenger or ‘hitchhiker’ pests The issue of ‘passenger’ or ‘hitchhiker’ pests, including spiders, earwigs, centipedes, slaters, and even small snails, poses a problem. They often hide under the calyx or in the calyx cavity (if present). In this location, they are difficult to detect and are well protected from any preharvest insecticides and postharvest treatments (such as brushing). Some packhouses resort to checking under each lobe of the calyx, and use an air gun to remove insects, which is clearly an expensive practice and generally only practicable for very high value markets (such as Japan).

9.9

Postharvest handling practices

9.9.1 Harvest operations Different cultivars require different harvest techniques. For many cultivars (e.g. ‘Fuyu’ and ‘Triumph’), fruit must be cut from the tree using secateurs, leaving the

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calyx attached to the fruit, since hand-pulling can injure the fruit and adjoining stem. However, other cultivars (e.g. ‘Kaki-Tipo’), may be hand-harvested (twisted) from the stem. Another factor that has a significant influence on the harvest technique is that of fruit shape and the location and structure of the ‘apex spike’ (black spike at distal end of the fruit). If the spike is prominent, it is more likely to damage other fruit during handling and packing and in this case fruit must be harvested into single-layer trays (e.g. Italy) or 20-kg crates with three layers (New Zealand) rather than larger harvest bins (350 kg, Israel). The ability to harvest by hand and not use small trays clearly has significant impacts on speed and economics, but enhances the danger of bruising while filling the bins and during transport. 9.9.2 Packinghouse practices Generally persimmons do not require any specific handling procedure other than the usual grading, sizing and packaging, adapted to the marketing outlets. Only fruit harvested into bulk bins are dumped into water to ensure gentle fruit handling. Astringent cultivars have to be treated to remove astringency. The most common method used is exposure to 80% CO2 for one to three days, depending on the cultivar. The preference for this treatment is because of the maintained fruit firmness (relative to ethanol). In Japan, the method has been refined with temperature control, shortening the time required – CTSD (controlled temperature short duration). In Italy, ‘Kaki-Tipo’ is treated with ethylene (>100 μL L−1), in spite of its softening effect, since the response to CO2 is not optimal and that market favours the softer fruit. The treatment is applied at 25–30 °C for 24–36 hours, depending on the stage of maturity, and thereafter temperature is reduced to 15 °C until the desired colour is achieved. Fruit that are intended for storage periods in excess of 8–10 weeks require treatment to inhibit Alternaria black spot development. The recommended treatment in Israel for ‘Triumph’ is a 30-second dip in 500 mg L−1 hypochlorite or Troclosene-Na. 9.9.3 Control of ripening and senescence Using refrigeration to delay persimmon ripening and senescence is limited by chilling injury (CI), which is the decisive factor in choosing the appropriate storage temperature for each cultivar. Thus, the non-susceptible ‘Triumph’ can be stored at −1 °C for four months, ‘Fuyu’ develops CI within two weeks below 8 °C (air-stored), and the highly susceptible ‘Rojo Brillante’ maintains best quality at 15 °C, but only for three to four weeks. CA storage has been shown to be beneficial in retarding both softening and black spot development, but the optimal levels need to be determined for each cultivar. Internal injury is likely to appear at higher CO2 levels, especially under MA conditions, where the build-up of CO2 is controlled by the balance between fruit respiration (affected by temperature) and the selective permeability of the

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package material. Nonetheless, with films of suitable gas transmission, the storage life of ‘Fuyu’ persimmons can be tripled at 1 °C (Cia et al., 2006). The disadvantage of both storage methods is the rapid rate of fruit softening after removal of the fruit to shelf-life conditions. This has been shown to be remediable when CA storage follows 1-MCP treatment. Persimmon fruit respond very well to 1-MCP (commercially applied by AgroFresh as SmartFreshSM) at levels in the range of 0.3–0.6 mg L−1, at both storage and ambient temperatures, either before or after storage. In addition to alleviating CI in ‘Fuyu’ and ‘Rojo Brillante’, when applied before storage at 0 °C, the treatment extends the post-storage shelf life by retarding fruit softening. However, with long-term storage, decay development generally becomes the limiting factor. Hence, there is an advantage in combining 1-MCP pre-storage treatment with CA storage. Irrespective of this, it is convenient to apply 1-MCP in combination with the CO2 treatment to remove astringency (Harima et al., 2003), either before or after storage. Similarly, use of 1-MCP treatment prior to MA storage leads to near elimination of chilling injury for ‘Fuyu’ (Kim and Lee, 2005). This is typically carried out on only a small portion of the crop destined for long-term storage, because of the cost of treatment, additional handling and delays to packing, which generally make its universal use uneconomic. It should be noted that 1-MCP does not solve all physiological disorders, or pathological problems that typically result from storage for more than ten weeks. 9.9.4 Recommended storage and shipping conditions Optimum storage temperature is generally 0 °C, but variation between cultivars exists (e.g. ‘Rojo Brillante’ (see Section 9.5.1 above)). Ethylene scrubbing is generally not used under commercial conditions, but ethylene should be avoided where possible. Some cultivars respond well to MA storage (e.g. ‘Fuyu’) but CA is rarely used commercially (see Sections 9.5.4 and 9.9.3 above).

9.10

Processing

9.10.1 Fresh-cut processing Although there is potential for persimmons to be processed for fresh-cut, either as wedges or slices, there has been little development in this area. This is possibly because of the relative ease of preparation of persimmon fruit for serving and its relatively slow flesh browning in such situations. At 5 °C (a typical storage temperature for fresh-cut products), slices of ‘Fuyu’ have a shelf life of seven days in air, and eight days in a CA (2% O2 + 12% CO2; Wright and Kader, 1997). A longer shelf life can be expected at 0 to 2 °C (Crisosto, 2004). Itamura et al. (2009) found that ‘Saijo’ showed more softening when fruit were cut into vertical wedges rather than horizontal slices, and that fruit cut into small pieces softened the most rapidly. Application of 1-MCP slowed softening, but was not completely effective.

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Use of antioxidants such as sodium ascorbate and cysteine were found to reduce browning of fresh-cut ‘Rojo Brillante’ (Peraz-Gago et al., 2009). 9.10.2 Other processing practices The most common processing of persimmons is that of drying, which has been carried out for many centuries (Testoni, 2002). Typically the skin is removed (by hand or chemically), and the fruit then air-dried. Chinese and Japanese traditionally hang fruit to dry on strings, resulting in a high value product (Sugiura and Taira, 2009). Additional processing include dried powders from purees to prepare traditional sherbets (Cortellino et al., 2009), and, of course as carried out in nearly all cultures, various alcoholic beverages (Khositashvili et al., 2008).

9.11

Conclusions

Persimmon is a challenging fruit to work with and has many unique characteristics. 1-MCP has provided a key tool for elimination of chilling injury and/or softening. Indeed, the reduction in softening and chilling injury in persimmons is something very close to a ‘silver bullet’. However, rots still remain a challenge for long-stored fruit, particularly given the desire for non-chemical solutions. There are also a number of unexplained physiological disorders that appear mainly on the fruit surface after prolonged storage, which will probably gain importance once the application of 1-MCP and effective disease control enable extension of the fruit’s storage life. The issue of residual astringency is a problem in PCNA cultivars, which needs development of a rapid, simple measure of astringency that correlates with human perception. If this tool could be used in the field and/or packhouse, this would be advantageous. There are opportunities to further research the healthfulness of persimmons. To this end, a worldwide industry initiative into funding and co-ordinating this area was made at the recent International Persimmon Symposium in Italy (Wells, 2009).

9.12

References

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Ferri V C, Rombaldi C V, Silva J A, Pegoraro C, Nora L, et al. (2008), ‘Boron and calcium sprayed on “Fuyu” persimmon tree prevent skin cracks, groove and browning of fruit during cold storage’, Ciencia Rural, 38, 2146–2150. Forbus W R, Payne J A and Senter S D (1991), ‘Nondestructive evaluation of Japanese persimmon maturity by delayed light emission’, Journal of Food Science, 56, 985–988. Fukushima T, Kitamura T, Murayama H and Yoshida T (1991), ‘Mechanisms of removal of astringency by ethanol treatment in “Hiratanenashi” kaki fruits’, Journal of the Japanese Society for Horticultural Science, 60, 685–694. Fumuro M and Gamo H (2001), ‘Effects of baggin on the occurrence of black stain on the skin of “Shinsyu” persimmon (Diospyros kaki L.) grown under film’, Journal of the Japanese Society for Horticultural Science, 70, 261–263. George A P, Mowat A D, Collins R J and Morley-Bunker M (1997), ‘The pattern and control of reproductive development in non-astringent persimmon (Diospyros kaki L.): a review’, Scientia Horticulturae, 70, 93–122. George A P and Redpath S (2008), ‘Health and medical benefits of persimmon fruit: a review’, Advances in Horticultural Science, 22, 244–249. Glucina PG (1987), ‘Calyx separation: a physiological disorder of persimmons’, Orchardist of New Zealand, 60, 161–163. Gorinstein S, Kulasek W, Bartnikowska E, Leontowicz M, Zemser M, et al. (2000), ‘The effects of diets, supplemented with either whole persimmon or phenol-free persimmon, on rats fed cholesterol’, Food Chemistry, 70, 303–308. Gottreich M and Blumenfeld A (1991), ‘Light microscopic observations of tannin cell walls in persimmon fruit’, Journal of Horticultural Science, 66, 731–736. Grant T, Macrae E A and Redgwell R J (1992), ‘Effect of chilling injury on physicochemical properties of persimmon cell wall’, Phytochemistry, 31, 3739–3744. Gu H F, Li C M, Xu Y J, Hu W F, Chen M H and Wan Q H (2008), ‘Structural features and antioxidant activity of tannin from persimmon pulp’, Food Research International, 41, 208–217. Guelfat-Reich S and Ben-Arie R (1976), ‘CA storage of “Triumph” persimmons’, Proceedings of the XIV Congress of the International Institute of Melbourne Refrigeration, 59–63. Guelfat-Reich S, Ben-Arie R and Metal N (1975), ‘Effect of CO2 during and following storage on removal of astringency and keeping quality of “Triumph” persimmons’, Journal of the American Society of Horticultural Science, 100, 95–98. Haginuma S (1972), ‘Controlled atmosphere storage of fruits in Japan’, Japan Agricultural Research Quarterly, 6, 175–180. Hamada K, Hasegawa K and Ogata T (2008), ‘Effects of CPPU and strapping on fruit size and maturity in “Hiratanenashi” Japanese persimmon’, Journal of Horticultural Science and Biotechnology, 83, 477–480. Harima S, Nakano R, Yamauchi S, Kitano Y, Yamamoto Y, et al. (2003), ‘Extending shelflife of astringent persimmon (Diospyros kaki Thunb.) fruit by 1-MCP’, Postharvest Biology and Technology, 29, 319–324. Homnava A, Payne J A, Koehler P and Eitenmiller R (1990), ‘Provitamin A (alphacarotene, beta-carotene and beta-cryptoxanthin) and ascorbic acid content of Japanese and American persimmons’, Journal of Food Quality, 13, 85–95. Ikegami A, Kitajima A and Yonemori K (2005), ‘Inhibition of flavonoid biosynthetic gene expression coincides with loss of astringency in pollination-constant, non-astringent (PCNA)-type persimmon fruit’, Journal of Horticultural Science and Biotechnology, 80, 225–228. Itamura H, Kitamura T, Taira S, Harada H, Ito N, et al. (1991), ‘Relationship between fruit softening, ethylene production and respiration in Japanese persimmon “Hirataneneshi” ’, Journal of the Japanese Society for Horticultural Science, 60, 695–701.

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Nakano M, Yonemori K, Sugiura A and Kataoka I (1997), ‘Effect of gibberellic acid and abscisic acid on fruit respiration in relation to final swell and maturation in persimmon’, Acta Horticulturae, 436, 203–214. Nakano R, Inoue S, Kubo Y and Inaba A (2002), ‘Water stress-induced ethylene in the calyx triggers autocatalytic ethylene production and fruit softening in “Tonewase” persimmon grown in a heated plastic-house’, Postharvest Biology and Technology, 25, 293–300. Nakano R, Ogura E, Kubo Y and Inaba A (2003), ‘Ethylene biosynthesis in detached young persimmon fruit is initiated in calyx and modulated by water loss from the fruit’, Plany Physiology, 131, 276–286. Nakano R, Yonemori K and Sugiura A (1998), ‘Fruit respiration for maintaining sink strength during final swell at growth stage III of persimmon fruit’, Journal of Horticultural Science and Biotechnology, 73, 341–346. Neuwald D A, Streif J, Sestari I, Giehl R F H, Weber A and Brackmann A (2009), ‘Quality of “Fuyu” persimmon during modified atmosphere storage’, Acta Horticulturae, 833, 227–238. Niikawa T, Suzuki T, Ozeki T, Kato M and Ikoma Y (2007), ‘Characterisitics of carotenoid accumulation during maturation of the Japanese persimmon “Fuyu” ’, Horticultural Research (Japan), 6, 251–256. Nissen R J, George A P, Collins R J and Broadley R H (2003), ‘A survey of cultivars and management practices in Australian persimmon orchards’, Acta Horticultuae, 601, 179–185. Ortiz G I, Sugaya S, Sekozawa Y, Ito H, Wada K and Gemma H (2006), ‘Expression of 1-aminocyclopropane-1-carboxylate synthase and 1-aminocyclopropane-1-carboxylate oxidase genes during ripening in “Rendaiji” persimmon fruit’, Journal of the Japanese Society for Horticultural Science, 75, 178–184. Oshida M, Yonemori K and Sugiura A (1996), ‘On the nature of coagulated tannins in astringent type persimmon fruit after an artificial treatment of astringency removal’, Postharvest Biology and Technology, 8, 317–327. Ozawa T, Lilley T and Haslam E (1987), ‘Polyphenol interactions: astringency and the loss of astringency in ripening fruit’, Phytochemistry, 26, 2937–2942. Palou L, Montesinos-Herrero A, Guardado A, Besada C and Del Rio MA (2009), ‘Fungi associated with postharvest decay of persimmon in Spain’, Acta Horticulturae, 833, 275–280. Pang J H, Ma B, Sun H J, Ortiz G I, Imanishi S, et al. (2007), ‘Identification and characterization of ethylene receptor homologs expressed during fruit development and ripening in persimmon (Diospyros kaki Thunb.)’, Postharvest Biology and Technology, 44, 195–203. Park Y M and Lee Y J (2005), ‘Ripening responses of “Fuyu” persimmon fruit to exogenous ethylene and subsequent shelf temperature’, Acta Horticulturae, 685, 151–156. Perez A, Ben-Arie R, Dinoor A, Genizi A and Prusky D (1995), ‘Prevention of black spot disease in persimmon fruit by gibberellic acid and iprodione treatments’, Phytopathology, 85, 221–225. Perez-Gago M B, del Rio M A, Argudo C, and Mateos M (2009), ‘Improving shelf life of cut persimmon fruit’, Acta Horticulturae, 833, 245–250. Perez-Munuera I, Quiles A, Larrea V, Arnal L, Besada C and Salvador A (2009), ‘Microstructure of persimmon treated by hot water to alleviate chilling injury’, Acta Horticulturae, 833, 251–256. Pesis E and Ben-Arie R (1984), ‘Involvement of acetaldehyde and ethanol accumulation during induced de-astringency of persimmon fruits’, Journal of Food Science, 49, 896–899. Pesis E and Ben-Arie R (1986), ‘Carbon dioxide assimilation during postharvest removal of astringency from persimmon fruit’, Physiologia Plantarum, 67, 644–648. Pesis E, Levi A and Ben-Arie R (1986), ‘Deastringency of persimmon fruits by creating a modified atmosphere in polyethylene bags’, Journal of Food Science, 51, 1014–1016.

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10 Pineapple (Ananas comosus L. Merr.) A. Hassan and Z. Othman, Malaysian Agricultural Research and Development Institute (MARDI), Malaysia and J. Siriphanich, Kasetsart University, Kamphang Saen, Thailand

Abstract: The pineapple is the third most important tropical fruit in the world after banana and citrus; the world pineapple production in 2007 was estimated at 21 008 795 tonnes. This chapter discusses various aspects of postharvest biology and technology of pineapple. The chapter is divided into 11 sections covering postharvest physiology, physical and biochemical changes during maturation and ripening, preharvest and postharvest factors affecting quality, physiological disorders, pathological disorders, insect pests and their control, postharvest handling practices, and processing. Key words: Ananas comosus, pineapple, postharvest handling, storage, physiology.

10.1

Introduction

10.1.1 Origin, morphology and structure Pineapple (Ananas comosus L. Merr.) is believed to be originated from South America, in the region encompassing central and southern Brazil, northern Argentina and Paraguay. The fruit had already been domesticated by the native South Americans before the arrival of Christopher Columbus in 1493. Currently, pineapples are grown commercially over a wide range of latitudes from approximately 30° N in the northern hemisphere to 33°58′S in the south (Malezieux et al., 2003). The word ‘pineapple’ was used by the European explorers to describe the fruit, which resembles pinecones. ‘Ananas’, the original name of the fruit, comes from the Tupi word for pine ‘nanas’, and comosus means ‘tufted’ referring to the stem of the fruit (Collins, 1968). The pineapple is an herbaceous perennial plant of the Liliopsidae (monocotyledonous). The adult plant is 1–2 m high and 1–2 m wide, and it is inscribed in the general shape of a spinning top (d’Ecckenbruge and Leal, 2003). The main morphological structures are the stem, the leaves, the peduncle, the

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Morphological structure of pineapple.

multiple fruit, the crown, the shoots and the roots (Fig. 10.1). The multiple fruit is the result from the fusion of individual fruitlets on a single stalk (Rohrbach and Apt, 1986). Multiple flowers, helically arranged along the axis each produce a fleshy fruitlet that becomes pressed against the fruitlets of adjacent flowers, forming what appears to be a single fleshy fruit. Early European experts recognized as many as 48–68 pineapple cultivars and classified them based on spininess, fruit shape and flower colour. Py et al. (1987) classified pineapple into five groups namely Spanish, Queen, Cayenne, Pernambuco and Perolera. 10.1.2 Worldwide importance and economic value Pineapple is the third most important tropical fruit in the international trade after bananas and citrus; the world pineapple production in 2007 was estimated at 21 008 795 tonnes. About 70% of the total production is consumed domestically, whereas 30% is exported. The most important producing country is Thailand producing 2 815 275 tonnes followed by Brazil (2 676 417), Indonesia (2 237 858), Philippines (2 016 462), Costa Rica (1 968 000), China (1 386 811), India (1 308 000), Nigeria (900 000), Mexico (671 131), Vietnam (470 000), Kenya (429 065),

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Colombia (342 014), Venezuela (363 075) and Malaysia (360 000) (FAO, 2009). Successful production is influenced by several factors especially low production cost, and availability of manpower and land resources. Costa Rica is the most important exporting country with an export quantity of 1 353 027 tonnes followed by the Philippines (270 054), Ecuador (99 581), Cote D’Ivoire (96 558), USA (89 269) and Panama (61 210). Other exporting countries include Honduras, Guatemala, Brazil, Mexico, Ghana and Malaysia (FAO, 2009). The USA is the largest pineapple importer totalling 696 820 tonnes in 2007, followed by Belgium (292 499), the Netherlands (200 026), Germany (167 416), Japan (165 794), Italy (142 168), United Kingdom (116 730), Spain (113 182) and Canada (102 064). The European Union is the largest export market for pineapple (FAO, 2009). For a very long time, the world production and marketing of pineapple has been dominated by the Smooth Cayenne both for fresh and processing. However, in 1996 the world’s pineapple fresh fruit industry went through a transformation when the Del Monte Corporation introduced hybrid ‘MD-2’ for the United States and European markets (Bartholomew, 2009). ‘MD-2’, produced from a cross between the PRI hybrids 58–1184 and 59–443 (Chan et al., 2003), is now grown by many companies and growers in the world and believed to be the most important pineapple cultivar for the fresh market. It is being exported to many countries including the United States, Europe, United Kingdom, Japan, Korea, Hong Kong, China, Singapore and the Middle East (Bartholomew, 2009). 10.1.3 Culinary uses and nutritional value Pineapple is produced for both fresh consumption and processing. Pineapple for fresh consumption is marketed in whole or minimally processed form with a short marketable period. Besides being consumed as desserts, fresh pineapple is also eaten as salad where some spices or sauces may be added according to taste preference. Pineapple can be cooked into various forms or used as an ingredient in cooking. Various processed products from pineapple were described by Abd Shukor et al. (1998), Collins (1968) and Dev and Ingel (1982). Fresh pineapple is a good source of carbohydrate, fibre and minerals especially Ca, P, Fe, Na and K. It also contains some vitamins including A, B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B9 (folate) and C (ascorbic acid). The nutritional content is influenced by several factors including varieties, soil, climatic condition, maturity stage and handling. Processing may result in the nutritional components being altered in the final processed products (Tee et al., 1988).

10.2

Fruit development and postharvest physiology

10.2.1 Fruit growth, development and maturation The pineapple fruit and their components, including core, flesh and shell, show similar sigmoid development (Py et al., 1987; Singleton, 1965) and the maturation period of

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fruit is influenced by several factors, including cultivars, climatic condition, altitude and cultural practices. During the maturation period, the increase in fruit weight slows down while the accumulation of dry matter speeds up as well as the soluble solids content. The peduncle itself starts to dry out. At the same time, the quantity of air in the intercellular space as well as in the locule of each fruitlet reduces progressively (Py et al., 1987). When the intercellular space or pocket of air between cells disappears late in the fruit development, the translucency appearance may occur in some cultivars. Because of this development, specific gravity of the fruit increases (Smith, 1984). Artificial flower induction substances such as ethylene and α-naphthaleneacetic acid (NAA) could delay fruit development. NAA at 100 ppm and 2-chloroethylphosphonic acid (CPA) at 200 ppm applied to the developing inflorescence less than 2.5 cm in diameter can delay fruit maturity by one to four weeks, while increasing fruit size by 25% (Bartholomew and Criley, 1983; Gortner, 1969). The Smooth Cayenne normally takes 100–150 days to develop from flowering to maturation with a shorter maturation period in lower altitude and equatorial regions. Pernambuco takes a longer developmental period, while Red Spanish and Queen take shorter time (Py et al., 1987). The first sign of pineapple maturation is around seven weeks before harvest when the development of new leaves in the crown slows down and four weeks later shell colour begins to change (Gortner, 1965). The yellow colour formation at the base of the fruit starts at around 100 days after flowering and this shell colouring is the most common criteria to judge pineapple maturity. In cooler seasons, the yellow shell colour develops well and coincides with the development of flesh colour and translucency of the flesh. However, in warmer periods, pineapple can reach maturity when it is still green, especially in Smooth Cayenne. The flatness of the eye is also used as a maturity indicator in this cultivar, but not in Queen where the eyes are prominent (Py et al., 1987). 10.2.2 Respiration and ethylene production Pineapple is a non-climacteric fruit (Dull et al., 1967) and has a moderate respiration rate around 10 to 20 ml CO2.kg−1.h−1 at 20 °C. Ethylene production rate in pineapple is low, ranging between 9 and 300 nl.kg−1.h−1. However, ethylene production is higher in more mature fruit. Internal ethylene concentration ranged from 80 to 1140 μl. l−1 with lower concentration in the upper part of the fruit (Dull et al., 1967). Cazzonelli et al. (1998) showed that during ripening, the expression of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase increased by 16 fold, while there was no increase in ACC oxidase. The study shows a significant role of ethylene in the control of pineapple ripening.

10.3

Physical and biochemical changes during maturation and ripening

10.3.1 Colour During maturation, there is no change in both the shell and the flesh colour. As ripening begins, the chlorophyll in the shell degrades resulting in the yellowing of

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the fruit without any increase in carotenoid pigment except late in the senescence stage. During shell yellowing, the flesh also turns from white to yellow in concomitance with accumulation of carotenoids (Gortner, 1965; Py et al., 1987). There is similar change in shell and flesh colour and their chemical components between fruit harvested green and those attached on the plant (Dull et al., 1967).

10.3.2 Texture Pineapple texture changes gradually from firm to soft as the fruit advances in maturity and ripeness. There are some variations in the texture of different groups of pineapple where Smooth Cayenne are fibrous, Red Spanish and Pernambuco are non-fibrous while Queen and Perolera are crispy in texture (Py et al., 1987). In the case of Queen pineapple, the core can also be consumed. These textural variations could be due to the differences in the chemical compositions of the cell wall in different pineapple groups. Textural differences can also be influenced by maturity stage and growing location (Bartolome et al., 1995). Vidal-Valverde et al. (1982) reported that hemicellulose was the major pineapple cell wall component (41.8%) followed by cellulose 33.6 % and pectin 21.2%. Lignin was found to be only 0.05%. Alcohol insoluble solid (AIS) of pineapple fruit declined with their maturity (Singleton and Gortner, 1965; Dull, 1971). The fibre content, a component of the AIS, also increased up to the onset of ripening and then decreased (Dull, 1971). They also reported that a large amount of unaccounted material, probably hemicellulose, increased during maturation and could play a major role in pineapple texture.

10.3.3 Starch Pineapple fruit does not accumulate starch (Py et al., 1987; Dull, 1971) which explains the small changes in chemical composition and taste of the fruit during ripening. The starch content is very low throughout fruit development where the highest value is less than one per cent, achieved 60 days before ripeness (Dull, 1971).

10.3.4 Sugars The major sugar components in pineapple fruits are sucrose, fructose, and glucose (Flath, 1980). During the early stage of fruit development, glucose and fructose are the major sugar component with low content of sucrose. Around six weeks prior to full ripeness, sucrose abruptly accumulates up until harvesting (Chen and Paull, 2000). The accumulation of sugars up until harvesting was suggested to be due to the high activity of the cell wall enzyme, invertase. At harvest, soluble solids content in pineapple varied a great deal depending upon maturity, season, and cultural practices. A variation from 7 to 21% soluble solids content was reported in a study covering three seasons in Australia (Smith, 1988b). Sugar

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continues to accumulate if the fruit remains attached. However, soluble solids declined when the translucent area developed higher than 50 to 60% (Bowden, 1969). After harvest, there is only a small decline in sugar or soluble solids content. High storage and handling temperature enhances the decrease in sugar content (Paull and Rohrbach, 1982). There is a gradient of sugar concentration in an individual fruit where it is highest at the base and decreases towards the top. The difference between the base and the top portions could be up to four per cent. There is also different sugar distribution in a horizontal direction, sugar content is highest in the flesh near the core and decreases outward to the shell. Sugar in the core is slightly lower than that in the flesh nearby (Miller and Hall, 1953). Soluble solids content is the most correlated parameter with eating quality and always used as a quality criterion for selecting fruit suitable for fresh market (Smith, 1988a). Under commercial practice, a minimum soluble solids content requirement of 12% is used in both Hawaii and Australia. 10.3.5 Acids The major non-volatile organic acids are malic and citric, with a ratio of about 1 to 2–3 (Chan et al., 1973). During the first half of fruit development, the acidity remains quite stable at around 0.1–0.3%, and the malic acid content remains low throughout fruit development. Citric acid increases around six weeks to a maximum at 10 days before the fully ripe stage then declines as the fruit becomes more translucent (Singleton and Gortner, 1965). After harvest, the acid content may increase, particularly at temperatures below 20 °C, but at 29 °C and higher, the acid content decreases quickly. At intermediate temperatures, the acid content remains relatively stable (Dull, 1971). At harvest, the acid content can vary between 0.28 to 1.6%, depending on season, growing conditions, maturity stage and cultivar (Py et al., 1987). Acid distribution in individual fruit is reverse to that of sugar; lowest at the bottom and increases towards the top; high in the core, lowest in the flesh and intermediate near the shell (Miller and Hall, 1953). The acid content does not correlate well with the consumer acceptance of fresh fruit. As a result, sugar to acid ratio, which varies from 5.4 to 66.4 in three seasons’ study with Smooth Cayenne, is also not related to consumer acceptance (Smith, 1988b). 10.3.6 Ascorbic acid During the first half of fruit development, ascorbic acid content in pineapple is low then increases as the fruit becomes more mature, but declines later (Singleton and Gortner, 1965). At harvest, the ascorbic acid content varies according to maturity stage. For ‘Mauritius’ pineapple, the ascorbic acid content harvested between 120 to 130 days from flower induction varies from 23 to 40 mg.100−1 g flesh (Abdullah and Rohaya, 1997). The content in an individual fruit also varies and positively correlates with acid content. It is lowest at the bottom, which may be only half of that at the top, while it is intermediate at the middle (Miller and

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Hall, 1953). After harvest, the amount of ascorbic acid increases slightly or remains relatively constant for a few days, but ascorbic acid contents decrease gradually under prolonged storage at low temperature (Paull and Rohrbach, 1982). Upon exposure to higher ambient temperature following low temperature storage, ascorbic acid contents decrease very quickly (Abdullah and Rohaya, 1997; 1983; Abdullah et al., 1985; 1986; 1996). 10.3.7 Phenolic compounds Pineapple contains phenolic compounds, the major contributor to the antioxidant potential besides ascorbic acid (Gardner et al., 2000). The phenolic compounds include p-coumaric acid, ferulic acid, caffeic acid, sinapic acid, p-coumaroyl quinic acid, p-hydroxybenzoic acid, and p-hydroxy benzoic aldehyde (de Simon et al., 1992; van Lelyveld and de Bruyn, 1977). Each phenol, except sinapic acid, increases in concentration in pineapple fruitlets affected by blackheart disorder. 10.3.8 Protein Pineapple, like many other fruits, is very low in protein but contains bromelain, a glycoprotein having protease activity commonly used in the food industry. The amount of bromelain is roughly half of the protein found in pineapple where the content is much less in the fruit than the stem (Heinicke and Gortner, 1957), and it is higher at the top of the fruit and lower in the middle and the base (Miller and Hall, 1953). Bromelain activity remains relatively high during fruit development and declines at the ripening stage (Lodh et al., 1973) along with the total protein content (Gortner and Singleton, 1965). Another enzyme that received much attention in pineapple is polyphenol oxidase (PPO). Its activity is normally low at harvest, but following chilling stress, higher activity is induced (van Lelyveld and de Bruyn, 1977; Teisson et al., 1979b). PPO activity varies between different parts of the fruit at harvest, with significantly higher levels in the skin and crown leaves but negligible in any parts of the fruit pulp (Zhou et al., 2003). PPO activities increase in pineapple fruits affected by blackheart, a low temperature-related physiological disorder (Abdullah et al., 2009), and has also been implicated in black spot infected fruitlets of pineapple caused by Penicillium funiculosum and Fusarium monoliforme (Avallone et al., 2003). Peroxidase is another pineapple enzyme where the activity decreases during fruit development and during storage (Gortner and Singleton, 1965; Teisson et al., 1979b). Most amino acids decline during the development of the fruit, and those found are alanine, aspartic acid, asparagines, glycine and glutamic acid (Flath, 1980; Kermasha et al., 1987). However, aspartic acid is only found in high amounts at the mature stage. Histidine, the sulphur-containing amino acid methionine, and cystine are present in small amounts but increase abruptly during the ripening of the fruit (Gortner and Singleton, 1965).

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10.3.9 Mineral Pineapple contains some minerals including calcium, iron, magnesium, phosphorus, potassium and zinc. Variation in mineral content observed in pineapple could depend on the type of soil where the plants were grown, the water used for irrigation and the fertilizer applied (Flath, 1980). Deficiency of molybdenum may cause high nitrate levels in fruits, which leads to detinning in canned pineapple (Chairidchai, 2000; Chongpraditnun et al., 2000). 10.3.10 Volatile compounds Similar to other fruits, pineapple aroma increases with its maturity and ripening stages. More than 200 compounds have been identified including esters, lactones, aldehydes, ketones, alcohols, carbonyl acids, hydrocarbons, phenol and sulphur compounds. Summer fruit have more volatiles, especially ethyl alcohol and ethyl acetate, than winter fruit. More volatiles are produced as the fruit become more mature on the plant as well as during ripening after harvest (Flath and Forrey, 1970). As pineapple fruit turns from green to yellow, some volatiles increase while others decrease (Umano et al., 1992). Some volatiles are bound with sugar and released during the preparation of pineapple flesh with the reaction of β-glucosidase (Wu et al., 1991). Table 10.1 lists some of the major volatiles found in pineapple. Those with asterisk are identified as major contributors to pineapple aroma. Flavourist had already made available formulas of synthetic chemicals used to imitate pineapple aroma. Among the earlier compounds used are vanillin, n-dodecanal, allyl and amyl esters, maltol, ethyl maltol and isobutylfuryl propionate (Broderick, 1975).

10.4

Preharvest factors affecting fruit quality

10.4.1 Soil Pineapple have been grown on many types of soils including organic peat soil in Malaysia (see Plate XVIII in the colour section between pages 238 and 239); volcanic ash soil in Hawaii, many Caribbean islands and parts of the Philippines; and very sandy soils found in parts of southern Queensland and northern South Africa (Hepton, 2003). Pineapples grown on different types of soil may have different postharvest quality, for example in Malaysia, the pineapple grown on mineral soil is sweeter than those grown on organic peat. However, ‘Josapine’ pineapple grown on mineral soil is more susceptible to bacterial heart rot disease. 10.4.2 Climatic condition Fruit produced in winter in sub-tropical regions is known to be of poor quality as the fruit acidity is high (Bartholomew, 2009). The winter fruits are also subject to developing blackheart, a chilling-related physiological disorder, either in the field or after harvest (Leverington, 1968). Climatic conditions influence the nutritional

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Table 10.1

Major volatiles found in pineapple

Volatiles

References

Odour description

Methyl-3-(methylthio) propanoate*

Berger et al. (1985); Teai and Claude-Lafontaine (2001); Umano et al. (1992) Berger et al. (1985); HaagenSmit et al. (1945); Teai and Claude-Lafontaine (2001); Umano et al. (1992) Ohta et al. (1987); Umano et al. (1992) Ohta et al. (1987); Rodin et al. (1965); Umano et al. (1992) Takeoka et al. (1991); Teai and Claude-Lafontaine (2001) Ohta et al. (1987); Umano et al. (1992) Umano et al. (1992) Berger et al. (1983) Berger et al. (1985) Berger et al. (1985)

Pineapple-like

Ethyl-3-(methylthio) propanoate

3-hydroxy-2-butanone 2,5-dimethyl-4-hydroxy3-(2H) furanone Ethyl-2methylbutanoate* Ethyl acetate* Butane 2, 3 diol diacetate α-patchoulene 1-(E,Z)-3,5-undecatriene 1-(E,Z,Z)-3,5,8undecatriene

Fruity, pineapple-like

Burnt pineapple

Honey-like Fruity, spicy Balsamic, spicy, pinewood Balsamic, spicy, pinewood, more fruity

* Major contributors to pineapple aroma

content of fruit including ascorbic acid (Chan et al., 1973) and the acid content fluctuates markedly and consistently according to the weather variation before harvest, where there is a two-week lag before the effects of the weather factors become obvious. Ascorbic acid content is also influenced by the amount of sunlight received during the development as fruit under strong sunlight contains higher ascorbic acid (Singleton and Gortner, 1965). 10.4.3 Cultural practices Crown removal increases fruit size and the fruit becomes more cylindrical in shape, however, they become subject to sunburn (Py et al., 1987). Chemical application such as 3-chlorophenoxyacetic acid (3-CPA) at the early stage of crown development can reduce crown size and increase fruit size and yield (Bartholomew and Criley, 1983) and the size of the crown itself can be controlled by mechanically removing the apex at least two months before harvest to allow wound healing (Py et al., 1987). The use of 3-CPA for crown control may cause injury to the base of pineapple slips and the crown causing them to be easily detached from the fruit (Abd Shukor et al., 1998). The detached areas serve as entry points for disease causing microorganisms such as Thielaviopsis paradoxa and fruits with detached crowns have shorter storage life than those with the crown intact.

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Postharvest factors affecting quality

10.5.1 Physical damage Like other horticultural commodities, physical damage on pineapple may occur at any point throughout the handling chain right from harvesting until consumption. Physical damages are caused by mechanical factors such as cuts, abrasions, compaction and impact. The damages may appear immediately after the injury took place or in many cases they only become noticeable after some time during handling or marketing. Mechanical damage may affect fruit quality in terms of poor appearance, uneven fruit ripening and shorter storage life. Damaged fruits usually have higher respiration rates and the leakage cell content leads to infection by microorganisms (Paull and Chen, 2003). 10.5.2 Temperature The recommended optimum storage temperature for pineapple is between 7 and 13 °C (Hardenburgh et al., 1986; Paull, 1997). Temperatures lower than the optimum level may induce chilling injury. More mature fruits are more adaptable to lower temperature, but lower storage temperature and a longer storage period may induce acid accumulation. Up to 35% increase in titratable acidity has been found in pineapple stored for ten days at 8 °C. Prolonged exposure to lower temperatures may cause poor organoleptic quality, but under good handling practices, maintenance of the cold chain is necessary as interruptions may cause the development of internal browning, fungal diseases and shorter storage life (Paull, 1997). Exposure to extremely high temperature above 35 °C should be avoided as it may also affect fruit quality. Exposure to high temperature speeds up the deterioration process and increases weight loss due to excessive moisture loss through the fruit surface. Extremely high temperature may result in the shell and crown becoming dry, especially when fruits are transported without refrigeration. 10.5.3 Relative humidity The recommended range of relative humidity (RH) for storage of pineapple is 85–95% (Hardenburgh et al., 1986; Paull and Chen, 2003). Higher RH reduces water loss, which helps maintain the fruit appearance and freshness, while lower RH encourages moisture loss from the surface and affects fruit appearance. Loss of moisture causes physiological weight loss, but a reduction of water loss helps in maintaining the fruit external appearance. Wrapping the fruit in a perforated polyethylene (PE) sleeve helps the maintenance of the fruit external appearance by creating a moisture barrier, which slows down moisture loss. However, storing fruits under very high RH favours the growth of microorganisms on the shell and peduncle. 10.5.4 Atmosphere There is very limited use of controlled or modified atmosphere (CA or MA) for pineapple commercially (Yahia, 1998). The recommended condition is 2–5% O2

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and 5–10% CO2 (Kader, 1992). ‘Mauritius’ pineapple stored for more than three weeks under MA in sealed PE bags at 10 °C are affected by off-odour and off-flavour development (Abdullah et al., 1985), but waxing the fruit and high humidity during cold storage would give equal benefits as demonstrated by atmosphere modification.

10.6

Physiological disorders

10.6.1 Common chilling injury Chilling injury (CI) affects fruits exposed to temperatures below the optimum level for storage for sufficient time to cause injury. The symptoms of CI in pineapple include failure of the green shell to turn yellow, yellow-shelled fruit turning a brown or dull colour, wilting, drying and discolouration of crown leaves and a breakdown of internal tissue, giving a pale watery appearance (Dull, 1971; Abdullah et al., 2008). In bad cases, severe fungal diseases might infect the fruit. Visual symptoms of CI develop faster when the fruits are transferred to higher temperatures between 20 and 30 °C following exposure to low temperature, as different parts of the fruit have different levels of sensitivity towards CI (Abdullah et al., 2002). CI can be reduced or controlled through temperature manipulations. Pre-storage preconditioning at 15 and 10 °C also allows pineapple to be stored at sub-optimal temperature. The storage life of ‘N36’ pineapple is extended from five weeks at optimal temperature of 10 °C to more than eight weeks with less chilling injury at sub-optimal temperature of 5 °C (Abdullah et al., 2008). Similar treatments can also extend storage life of ‘Josapine’ pineapple. 10.6.2 Blackheart ‘Blackheart’, also known as ‘endogenous brown spots’ and ‘internal browning’, is another temperature-related physiological disorder of pineapple and has been comprehensively reviewed by Abdullah et al. (2010). The characteristic symptom of the disorder is the development of dark spots in the flesh area close to the core. In its early stage of development, the spots appear watery but they then enlarge and turn brown as the severity of the disorder increases. In severe cases, the entire flesh and core tissue of a fruit may be visibly affected. Fruits affected by blackheart appear normal externally and its presence is only detectable once the fruit has been cut open (Akamine, 1976; Akamine et al., 1975). The lack of detectable external symptoms creates substantial problems in the marketing of fresh fruit, as they have to be examined destructively. Blackheart may occur before harvest in the field or after harvest following exposure to low temperature and has been reported in fruits stored at temperatures as low as 4 °C and as high as 21 °C (Wills et al., 1985; Smith, 1983). Thus, in addition to the chilling at temperatures below the optimum, blackheart induction may also take place at temperatures higher than the normal range that causes CI. Blackheart has been associated with an increase in polyphenol oxidase (PPO)

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activity and reduction in ascorbic acid content in affected fruits (Teisson et al., 1979a,b). However, the initial PPO activity and ascorbic acid content do not necessarily indicate fruit susceptibility to blackheart (Stewart et al., 2002; Abdullah et al., 2010; Pauziah et al., 2005). Partial control of blackheart can be achieved by preharvest applications of chemicals such as parachlorophenoxyacetic acid (PCPA), α-naphthaleneacetic acid (ANA), potassium and calcium (Abdullah et al., 2009). Harvesting fruit at an earlier maturity can delay the appearance of blackheart symptoms but they can still appear at postharvest when exposure at ambient temperature is prolonged after low-temperature storage (Abdullah and Rohaya, 1997). After harvest, blackheart can be partially controlled by several methods including thermotherapy (Abdullah et al., 1983; Akamine et al., 1975), MA packaging (Abdullah et al., 1985; Haruenkit and Thompson, 1994; Mizuno et al., 1982), surface coating (Abdullah et al., 1983; Nimitkeatkai et al., 2006; Pimpimol and Siriphanich, 1993; Rohrbach and Paull, 1982; Zaulia et al., 2007) and 1-methylcyclopropene (1-MCP) (Selvarajah et al., 2001). Development of pineapple hybrids resistant to blackheart is the most practical approach to overcome the problem and some have been successfully developed in Hawaii and Malaysia (Abdullah et al., 2010). The Pineapple Research Institute of Hawaii has successfully developed two hybrid cultivars, ‘73–50’ and ‘53–116’ from Smooth Cayenne that show significant levels of resistance to blackheart. The ‘MD-2’, a superior hybrid developed by the Del Monte Corporation, is also resistant to blackheart (Bartholomew, 2009). Research on blackheart control through molecular breeding approaches has been conducted in Australia (Graham et al., 2000; Zhou et al., 2002) and Malaysia (Abu Bakar et al., 2008). 10.6.3 Flesh translucence Flesh translucence in pineapple is regarded as a physiological disorder by Py et al. (1987) and Paull (1997). The flesh affected by translucency shows water-soaking symptoms (Paull and Chen, 2003). It occurs together with fruit ripening when the shell colour at the base of pineapple fruit of some cultivars begins to turn yellow. It may also occur in green-ripe fruit where the whole flesh is affected while the skin is still green (Py et al., 1987). In the translucent flesh, the air space is filled with liquid where highly translucent fruit has a flat taste and might be off-flavour (Bowden, 1969). This off-flavour taste could be the result of anaerobic respiration of the flesh which is blocked from exchanging gases through the intercellular network. These fruits are very fragile and easily damaged during handling and transportation and are also susceptible to disease and preharvest sunburn (Paull and Reyes, 1996). The causes of flesh translucence are not well understood, but large fruit and fruit with small crowns tend to develop more symptoms of flesh translucence. High temperature, high radiation and high nitrogen fertilizer facilitate translucent flesh development, so shading the fruit may eliminate the translucency development (Py et al., 1987; Soler, 1993). Both crown weight and flesh translucency were

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reported to be correlated with monthly average air temperature two to three months before harvest (Paull and Reyes, 1996). However, crown removal does not influence translucency occurrence (Chen and Paull, 2001). After harvest, flesh translucency increases in stored fruits and it could be reduced by waxing (Rohrbach and Paull, 1982) and thermotherapy (Akamine et al., 1975).

10.7

Pathological disorders

The most important postharvest disease in pineapple is black rot, which can be found in all production areas around the world and the disease incidence could be as high as 70% of the inspected shipments to the New York market (Cappellini et al., 1988). The disease is caused by Thielaviopsis paradoxa (de Seynes) von Hohn which infects through a wound or cracked surface. The flesh of infected fruit becomes soft and watery and later turns dark due to the growth of the fungal mycelium and its chlamydospore. Postharvest control can be achieved by careful harvest and handling to prevent wounding or bruising and treating the fruit with suitable fungicides (see Table 10.2) within six to 12 hours after harvest (Rohrbach and Schmitt, 1994). Other pineapple diseases (Table 10.2) are caused by fungi or bacteria already present on the fruit at preharvest. Infection usually occurs through wound or cracks on the surface or damage caused by insects. The incidence of these diseases after harvest is rather limited as compared to black rot, and mostly cannot be controlled after harvest (Rohrbach and Schmitt, 1994). In addition to these infectious diseases, pineapple can be damaged by yeast and bacteria trapped inside the fruit during fruit development when individual fruitlets fuse together (Rohrbach and Apt, 1986). If fruit are damaged or overripe, the yeast and bacteria start growing leading to fermentation with bubbles of gas and juice escaping through cracks on the skin. The skin turns brown and leathery and the fruit becomes spongy with bright yellow flesh (Paull, 1997). Moulds on the cut surface of the peduncle are saprophytes but give an unsightly appearance (Paull, 1997). Dipping the fruit with a fungicide listed in Table 10.2 or adding coating material to the fungicide can control the mould growth.

10.8

Insect pests and their control

No major insects attack pineapple fruit, but a butterfly, Thecla basilides (Geyer) may lay eggs on the inflorescence. The larva penetrates and digs out holes causing misshapen fruit, and the fruit reacts by exuding an amber coloured gum which makes it impossible to sell. The existence of this insect is limited to Central and South America (Py et al., 1987). The Smooth Cayenne pineapple is resistant to all tropical fruit flies, namely the Mediterranean fruit fly (Ceratitis capitata Wiedemann), the melon fly (Dacus cucurbitae Coquillett) and the oriental fruit fly (D. Dorsalis Hendel) (Macion et al., 1968; Seo et al., 1970; 1973). The cultivar is not regarded as host and therefore quarantine treatment is not required for

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© Woodhead Publishing Limited, 2011 Fusarium subglutinans (Wollenweb. & Reinking)

Light to dark brown discolouration of fruitlet, sunken fruitlet, profuse pink sporulation and exudation of gum

Yellowish, reddish brown, to very dark, dull brown discolouration of fruit tissue. Infected tissues generally become harden, granular, brittle and speckled with colour variation

Fruit turns brown or black when cooked during canning process. Uncooked may be symptomless or light pink to brown and may smell like cantaloupe

Fusariosis

Marbling

Pink disease

Through open flower by nectar feeding, insects remain latent until fruit ripening

Usually low incidence, found mostly in cool area where air temperature does not exceed 29 °C

Compiled from: Damayanti et al. (1992); Lim (1985); Rohrbach and Phillips (1992); Rohrbach and Schmitt (1994); Py et al. (1987).

Erwinia herbicola, Erwinia sp. Gluconobacter oxyden (Henneberg) de ley Acetobacter aceti (Pasteur) (Syn. Acetobacter liquefaciens)

No postharvest control

No postharvest control

No postharvest control Worldwide but epidemic in lowland tropics where temperature remains above 21 °C

Flower through South America caterpillar wound

Brazil, Hawaii, South Africa

Low temperature 8–9 °C; gamma radiation 50–250 Gy; use of fungicides within 6–12 hours after harvest such as benomyl 1200–1400 ppm, triademenol 250 ppm, imazalil 250 ppm, triademefon 500 ppm, sodium salicyl anilide 1%, o-phenylphenol, captan, salicylic acid, benzoic acid No postharvest control, endosulfan at forcing and 3 weeks after forcing

Worldwide, especially in lowland tropics

Through wounds or cracks within 8–12 hours

Unopen flower through mite injured trichome

Control

Distribution

Infection

Open flower and Acetobacter peroxydans Visser’t Hooft, Acetobacter cracks on the fruit sp. and Erwinia herbicola var. ananas (Serrano)

Penicillium funiculosum Thom, Fusarium subglutinan (Wollenweb. & Reinking)

Thielaviopsis paradoxa (de Seynes) von Höhn (Syn. Chalara paradoxa (de Seynes) Sacc.)

Soft watery flesh later turn dark from the growth of mycellium and chlamydospore

Black rot, water rot, water blister, soft rot, or Thielaviopsis fruit rot

Centre part of an individual Fruitlet core rot, leathery pocket, eye rot, interfruitlet fruitlet becomes brown to black, distorted fruit shape corking, black spot, or fruitlet brown spot

Pathogen

Symptom

Nature and control of postharvest diseases in pineapple

Name

Table 10.2

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importation into fruit fly-free countries (Paull, 1997). For other cultivars, vapour heat treatment at 44.6 °C for 8.75 hours is required in mainland United States (Armstrong, 1994). Surface insects including mealy bug, scale and mite cause some postharvest problems. These insects should be well controlled before harvest since they can easily miss detection or removal during postharvest handling, by hiding underneath the bract on individual fruitlets and in the crown. They can be removed by using a brush or water jet during the washing procedure. If these surface insects are found upon entry to the United States, the fruit must be fumigated with methyl bromide at concentrations depending on the temperature at the time of fumigation (Armstrong, 1994). Exporting pineapple to China also requires the control of surface insects besides fumigation with methyl bromide.

10.9

Postharvest handling practices

10.9.1 Harvesting Pineapple is harvested once it has already achieved its optimum maturity for consumption. A minimum total soluble solids (TSS) level of 12% is the requirement under the worldwide Codex standard for fresh pineapple (Codex Alimentarius, 2007). Changes on the skin colour and shape of the eyes can be used to estimate fruit maturity. For ‘Mauritius’, the fruit are harvested at breaker stage, i.e. 120 days after flower induction. Fruits for nearby market are harvested at a more advanced stage as customers prefer ripe pineapple. Being a non-climacteric fruit, the taste and flavour of pineapple are better developed in the tree-ripened fruit and they will not improve after harvest (Dull, 1971). During harvesting, pineapple is cut off the plant with a machete. Harvesting should be done carefully to prevent bruising, especially for large fruit. Harvested fruits are placed inside the basket on the back of workers (see Plate XIX in the colour section). When the basket is full, the fruit are piled up at the end of rows or directly loaded on to a truck, for transportation to the packinghouse as soon as possible. The use of crates while in the field is encouraged to reduce mechanical injury. In large-scale plantations, carrying fruit by hand is avoided by using a harvesting aid. In this case, harvesting crews walk between rows of pineapple following the ‘harvester’, which has a boom with a conveyer belt extended to the side. Pickers harvest the fruit and place them on the belt, but fruit is better placed by hand in the field bin upside down to avoid injury (Py et al., 1987). While in-field it is also important to leave the fruits under shaded conditions for protection from the sun. 10.9.2 Packinghouse operations Harvested fruits are prepared for the markets at packinghouses which may be located either inside or outside the farm. Packinghouse operations for pineapple may include cleaning, washing, grading, sizing, fungicide treatment, surface coating, drying and

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packaging (Abd Shukor et al., 1998; Abdullah et al., 2000). Suitable operations conducted would depend on the market, method of transportation and duration to reach the market as the operations for the domestic market are usually simpler than for the export markets. Once arrived at the packinghouse, pineapple can be unloaded by hand, dumped, sliding or submerging the whole container into a water tank to remove dirt and surface insects. A water jet or brush could also be used for cleaning. Bracts at the base of the fruit should be removed by hand, since insects could be hiding underneath, and the fruit stem is trimmed to about 5–20 mm for vertical packing. Sorting for green-ripe fruit could also be done at this stage since they sink while others float in water (Py et al., 1987). Specific gravity may be used as an index of eating quality. Smith (1988a) suggested the use of two water tanks containing water and a 2.5% salt solution to grade pineapple into three groups: floated in water, sunk in water but floated in salt solution, and those sunk in salt solution. Due to the natural progressive development of flesh translucency from the base to the top of the fruit, the angle of fruit floating in water could also be used to separate fruit with different degrees of translucency. Those that float in an upright position are most translucent, while those that float at 45 degree or lay horizontal are less translucent (Songprateep, 1990). After washing, pineapples are sorted to remove defected ones such as malformed, bruised or insect damaged. Fruit with black rot can also be removed judging from early degreening of some fruitlets. Fruit with an under- or over-developed crown could also be removed (Py et al., 1987). In Hawaii, crown to fruit size ratio should be within 0.33 to 1.5 (Paull, 1997). Large crowns could also be reduced by ‘gouging’ in which part of the crown is removed. This technique leaves a wound, may reduce overall appearance, and could cause disease development during subsequent transport or storage. Gouging can also be done in the field two months before harvest to allow proper healing (Py et al., 1987). A fungicidal treatment such as thiabendazol (TBZ) is applied by dipping or spraying to control black rot disease caused by Thielaviopsis paradoxa. In small-scale operations, pineapple is classified manually according to sizes by experienced workers and a simple balance is used to check fruit weight when in doubt. Sizing machines either by diameter or by weight are also available in large-scale operations including diverging belt and rotary weighing sizer. Under Codex standards, pineapple is classified into three classes, namely ‘Extra Class’, ‘Class I’ and ‘Class II’ according to fruit quality. Size is determined by the average weight of the fruit with a minimum weight of 700 g, except for small size varieties, which can have a minimum weight of 250 g (Table 10.3). 10.9.3 Packaging and transportation Pineapple for local markets in some developing countries are transported either in bulk without container or placed in traditional containers such as bamboo baskets. In some countries, the use of traditional baskets has been replaced with returnable plastic baskets or containers with improved features including better strength and stackable. Corrugated fibreboard cartons with specific design, dimension and capacity are most commonly used for export markets. In Hawaii, large cartons of

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Postharvest biology and technology of tropical and subtropical fruits Table 10.3 Size classification of pineapple under the Codex standard for pineapple Size code

A B C D E F G H

Average weight (+/− 12%) (in grams) With crown

Without crown

2 750 2 300 1 900 1 600 1 400 1 200 1 000 800

2 280 1 910 1 580 1 330 1 160 1 000 830 660

Source: Codex Alimentarius (2007).

20 kg containing six to ten fruits are used for surface or sea shipment, whereas smaller cartons of 10 kg containing five to six fruits are used for air shipment (Paull and Chen, 2003). Fruits in the cartons are arranged either vertically or horizontally with cushioning pads placed at the inner bottom and in between layers for protection from mechanical injury during handling and transportation. 10.9.4 Recommended storage and shipping conditions The recommended optimum temperatures for pineapple are 7–13 °C with relative humidity of 85–95% (see Sections 10.5.2 and 10.5.3). Under this condition, mature green fruit can remain fresh for four to five weeks. Fruits of more advanced maturity have shorter storage life than those of lesser maturity. The same temperatures are used for shipping pineapples in refrigerated containers. For shipping by sea, matured green fruits are stored or transported at 10 °C, whereas a temperature of 7.5 °C is used for fruits of more advanced maturity. For air shipment, fruit harvested at advanced maturity can be used and stored temporarily at 7.5 °C before being transported. MA or CA is not needed for transportation, as the benefit is minimal for storage life extension. Pineapple is compatible with many types of non-climacteric fruits and vegetables when transported under mixed load conditions. The most important consideration in mixed loads is compatibility with respect to their requirements for temperature, relative humidity, atmosphere, protection from odours, and protection from physiologically active gases, such as ethylene (Wilson et al., 1998; Mohd Salleh et al., 2008). 10.9.5 Control of ripening and senescence Storage life extension by preconditioning and storage at sub-optimal temperature are discussed in Section 10.6.1. Suitable postharvest treatments are covered in Sections 10.6.2 and 10.7 of this chapter.

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Processing

10.10.1 Fresh-cut processing Being a large size fruit and relatively hard to peel, pineapple is well suited to be prepared and sold as fresh cut or minimally processed (Siriphanich, 1994). Good handling practices for minimally processed pineapple involve the use of high quality fruits, high sanitation in preparation, good packaging and maintenance of a cold chain. The common temperatures used are 1–4 °C. Tissue injuries in freshly cut pineapple lead to a higher metabolic rate and shorter storage life than for the whole fruit. The use of very sharp knifes for cutting is necessary as fruit with fewer cuts have a lower metabolic rate than those with more cuts (Iverson et al., 1989). Fresh cut pineapple is also subjected to spoilage by microorganism. Yeast and fungi are of primary concern, while bacteria are secondary due to the low pH of the pineapple flesh. Sanitation during the preparation of fresh cut pineapple should be of primary concern for quality and safety. Newly prepared fresh cut pineapple, under careful preparation, could have as much as 105 cfu.g−1 total plate counts of microbial contamination (O’Conner-Shaw et al., 1994). The count could also vary up to 100 fold between preparations. The two most important microorganisms are Listeria monocytogenes, a saprophyte able to grow at low temperature and Escherichia coli, which is acid resistant. Contamination by microorganisms in the flesh may originate from the fruit before cutting but the level of contamination could be reduced by washing the fruits with clean and chlorinated water. With careful preparation, fresh cut pineapple can be stored for up to three weeks at 4 °C (Fadrigalan et al., 2000; Latifah et al., 1999; 2000). Powrie et al. (1990) claimed that fresh cut pineapples sealed in plastic bags and flushed with 15–20% oxygen and 3% argon can be stored for up to ten weeks at 1 °C. Another food preservation technique by using ultra-high pressure has also been studied on fresh cut pineapple (Aleman et al., 1994). However, browning can still proceed after this high-pressure treatment where PPO is relatively resistant to inactivation under high-pressure treatment (Aleman et al., 1998). The addition of ascorbic acid and storage at low temperature could delay the browning (Chen and Paull, 2001; Chen et al., 2000).

10.10.2 Other processed products Various processed products from pineapple were described by Abd Shukor et al. (1998). The products include juice, canned flesh, fruit cocktail, crushed pineapple, fruit punch, frozen pineapple, yoghurt, pineapple powder, freeze-dried pineapple, wines, sauces, jams, marmalades and confectionery. Collins (1968) has comprehensively reviewed by-products from pineapple fruit. The possible by-products include syrup from a cannery, alcohol, feed yeasts, organic acids such as citric acid and malic acid from the mill juice, and starch, protease and fibres from the plant residues of pineapples. Other pineapple by-products include bromelain, vinegar, wine and feed (Dev and Ingel, 1982).

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10.11

Conclusions

The pineapple has become one of the most established tropical fruits in world trade. The global pineapple industry continues to play very important roles for the future in meeting consumers needs and providing a good source of income and livelihood for many people. Many aspects of pineapple production and postharvesting have been studied and investigated by producing beneficial results but the vast knowledge and technologies that have been generated need further expansion in order to face new challenges. Research on the aspects of quality, safety, health and highly efficient technology, besides greater concern for environment, should be given stronger emphasis in the future.

10.12 Acknowledgements The authors wish to express their sincere thanks to Mrs Rohaya Md Atan and Mr Md Syahril Md Khalil of MARDI for their kind assistance in the preparation of the manuscript.

10.13

References

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11 Pistachio (Pistacia vera L.) M. Kashaninejad, Gorgan University of Agricultural Sciences and Natural Resources, Iran and L. G. Tabil, University of Saskatchewan, Canada

Abstract: The pistachio nut (Pistacia vera L.) is one of the most popular tree nuts in the world and is valued globally for its nutritional value, health and sensory attributes and economic importance. It is high in unsaturated fatty acids and low in saturated fatty acids, a rich source of proteins, dietary fibers, vitamins, minerals and antioxidants, and is an increasingly important nut crop consumed raw, salted or roasted. In common with other tree nuts, pistachios are rich in nutrient content and beneficial for the human diet. Careful harvesting, appropriate postharvest handling and proper processing, storage and packaging, all contribute to achieve optimum yield of high quality nuts. Pistachio nuts should be processed as soon as possible after harvest and stored in appropriate conditions to avoid mold growth and undesirable chemical reactions such as oxidative rancidity. This chapter will provide information about the botany, worldwide importance, postharvest pathology, harvesting, handling, processing and storage of pistachio nut. Key words: Pistacia vera, pistachio nut, processing, drying, roasting, aflatoxin.

11.1

Introduction

11.1.1 Origin and history The word pistachio is a loanword from the Zendor Avestan (ancient Persian language) pista-pistak (Joret, 1976) and is a cognate to the modern Persian word Peste. According to Dioskurides, the pistachio is derived from pissa (means resin) and aklomai (means to heal), i.e. a plant with healthy resin. The common name of pistachio in different languages is: Peste (Persian), Pistache (French), Pistazie (Germany), Pistacchio (Italian), Pistacho (Spanish), Pista (Indian), Pistasch (Swedish), Fustuq (Arabic) and Pisutachio (Japanese). The origins of the pistachio are Asia Minor (now Turkey), Iran, Syria, Lebanon, the Caucasus in southern Russia and Afghanistan (Zohary, 1952). It probably developed in interior desert areas because it requires long, hot summers for fruit maturation, is drought and salt tolerant, and has a high winter chilling requirement.

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Archeologists have found evidence in a dig site at Jarmo, near northeastern Iraq, that pistachio nuts were a common food as early as 6750 BC (Kirkbride, 1966; Kramer, 1982). The history of pistachio nuts reflects their ‘royal character’, endurance and pride. Especially fine pistachios are said to have been a favorite delicacy of the Queen of Sheba, who confiscated all Assyrian deliveries for herself and for her royal court (Whitehouse, 1957). Nebuchadnezzar, the ancient king of Babylon, had pistachio trees planted in his fabled hanging gardens around the 8th century BC (Brothwell and Brothwell, 1969). In the 2nd century BC, Nicander found pistachio in Susa, a village in southwestern Iran close to the border with Iraq (Joret, 1976). In the 1st century BC, Poseidonius recorded cultivated pistachio in Syria (Joret, 1976), and the nuts traveled from Syria to Italy in the 1st century AD and spread throughout the Mediterranean from there (Banifacio, 1942; Moldenke and Alma, 1952). Pistachio has been spread eastward from its center of origin and was reported in China around the 10th century AD (Lemaistre, 1959). It was introduced to USA in 1854 but commercial plantings did not develop until 1970 (Rieger, 2006). More recently pistachio has been cultivated in Australia. 11.1.2 Botany Pistachio is the only commercially edible nut among the 11 species in the genus Pistacia that all exude turpentine or mastic. Pistacia vera L. (Latin name of pistachio) is by far the most economically important and a member of the Anacardiaceae or cashew family. Other important members of this family are cashew, mango, mombins (Spondias spp.), poison ivy, poison oak, pepper tree and sumac. P. nigricans Crantz, P. officinarium Ait, P. reticulate Willd and P. terebinthus Mill are the synonyms of P. vera L. Pistachio trees are small to medium size and can grow to 12 m, but are generally smaller in the cultivation period. Leaves are compound-pinnate and generally with three and sometimes five leaflets. Their shapes vary from ovoid to oblongovoid with dark green above and paler below on entire margins and obtuse tips. The flowering behavior of pistachio trees depends on their location, which can be steppe-forests, steppe or semi-desert. Floral bud differentiation takes place before blossoming. Shoot elongation usually commences at the end of March and ends between April and May (Crane and Iwakiri, 1981). One or two axillary buds located on the new growth are vegetative. Inflorescence buds which are conspicuously larger than vegetative buds expand at the following March, and anthesis generally takes place at the end of May and after about three weeks they grow and differentiate very fast. The pistachio tree is dioecious, meaning that male and female flowers are borne on separate trees. Therefore, both male and female trees are required to produce nuts. The pistachio tree has about 13 primary branches with each bearing one terminal and five to 19 lateral flowers. The flowers are apetalous and include up to five sepals. Male flowers have five small stamens and females include a single tricarpellate, superior ovary. Since the female flowers are nectarine-free they cannot attract bees, although they may be attracted to male

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flowers for pollen. Therefore, the pollen is spread by wind. Pistachios grow on trees in grape-like clusters on first-year-old wood (see Plate XX in the colour section between pages 238 and 239). Based on location and variety, fruit development occurs at different times. For ‘Kerman’ variety following proper and successful pollination, fruit set and endocarp (nut shell) begins to enlarge in late April until May, while the kernel does not grow. During this period, the shell is very soft and sensitive to insect attacks. The shell begins to harden in June and from late June until early August the kernel grows and fills the shell. Nut ripening takes place during late August and September and the shell splits more and more along the ventral suture, hull color changes from green to red and abscission of the individual nut begins from the rachis (Hendricks and Ferguson, 1995). Fruiting takes place four to five years after transplanting but full bearing and economically significant crops happen around ten years of age. The pistachio fruit (nut) is a drupe and almost oval shape. It consists of a single seed (kernel), encased by a thin soft and edible seed coat (testa or skin), enclosed by a hard smooth inedible shell (endocarp), which is further surrounded by the fleshy hull (mesocarp and epicarp), which is also inedible (see Plate XXI in the colour section). The hull is thin and fleshy, pale green in color, with a red blush at maturity. The shell dehisces along the ventral suture with kernel growth and progresses along both sutures until physiological maturity reaches maximum size. The seeds range in color from light to dark green or greenish-yellow (called pistachio kernel green) and contain two cotyledons surrounded by a thin coating. Physiological maturity is manifested by loosening and easy separation of the hull from the shell and changing of the hull color from green to red (Crane, 1978). 11.1.3 Varieties Many cultivated varieties of pistachio are available in different countries with significant variation in their characteristics particularly in terms of size, shape, color, taste and splitting. Maggs (1973) reported that the main pistachio varieties in the world have been spread from Iran, Turkey and Syria. These varieties were obtained through seedling selection in the field. Pistachio is cultivated in different regions of Iran but Kerman province is the largest and most important pistachio growing area with much higher genetic diversity of pistachio than other regions. More than 70 varieties have been recorded in this province. ‘Ohadi’ or ‘Fandoghi’, ‘Kalle-Ghuchi’, ‘AhmadAghaei’, ‘Badami’, ‘Rezaei’ and ‘Momtaz’ are the major varieties grown in Kerman province (Fig. 11.1). ‘Ohadi’ cultivation has been increased during the last 40 years and now includes about 70% of pistachio orchards in this region. It is round-shaped with a light yellow to green kernel, bearing large bunches of green hulled and high splitting nuts. It produces attractive and good quality nuts suitable for export. Large fruit, high yield and good split percentage are the main reasons for the popularity of ‘Kalle-Ghuchi’ variety. It is also round-shaped with light green kernel (Esmail-pour, 2001).

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Fig. 11.1 Pictorial view of nut (left) and kernel (right) of five Iranian pistachio varieties; from top to bottom: ‘Akbari’, ‘Badami’, ‘Kalle-Ghuchi’, ‘Momtaz’ and ‘Ohadi’.

There are about 20 female pistachio varieties in Syria of which ‘Ashouri’ (‘Red Aleppo’), ‘Red Oleimy’ and ‘White Batoury’ are three main varieties. ‘Ashouri’ accounts for about 85% of the total pistachio area in Syria. A 40-year-old tree of ‘Ashouri’ variety produces up to 200 kg of fresh nuts per year. It is the best Syrian variety in terms of splitting (with 99%) and excellent as a table variety. ‘Ashouri’ nuts are elongated and red with dark spots and medium size (27 mm length, 15 mm width and 14.5 mm thickness) (Hadj-Hassan, 2001). In Turkey, there are eight main domestic varieties including ‘Uzun’, ‘Kirmizi’, ‘Halebi’, ‘Siirt’, ‘Beyazben’, ‘Sultani’, ‘Degirmi’ and ‘Keten Gomlegi’ and five foreign varieties from Iran including ‘Ohadi’, ‘Bilgen’, ‘Vahidi’, ‘Sefidi’ and ‘Momtaz’. Most of the harvested crop consists of ‘Uzun’ and ‘Kirmizi’ varieties. The ‘Uzun’ variety is long (19 to 21 mm) and plump; some of the nuts are half as wide as they are long with a splitting percentage of 69%. ‘Kirmizi’ is a red-hulled, thin-shelled, free-splitting, green kernel nut of medium size. All Turkish varieties except ‘Siirt’ have elongated nuts while ‘Siirt’ has ovoid nut shape. ‘Siirt’ is the best Turkish variety in terms of splitting with 92%. Domestic varieties generally have yellowish green kernels (Ak and Acar, 2001). About 20 varieties have been imported as seed from other countries to the United States and tested to develop as a local variety but the results have demonstrated that a special variety’s success in another country does not mean a successful performance in the United States. ‘Kerman’, a developed California variety, named after the main pistachio area in Iran (Kerman province) was introduced in the 1950s after testing for several years in California. Now, it is the main commercial variety grown in California consisting of about 99% of pistachio production in this state. It produces high yields of large nuts but it has a strong alternate-bearing habit and many blanks and non-split nuts. It has light greenish-yellow kernel with minimum flavor particularly after drying in commercial dryer. American consumers prefer pistachios from other countries because of better flavor and color attributes. ‘Joley’ is another female variety that was introduced from Damghan, Iran and has been planted mainly in New Mexico and a few orchards in California. It is smaller than ‘Kerman’ variety with greener kernel and better taste. It has almond-shaped nuts with high non-split percentage in some years.

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11.1.4 Uses Pistachio is cultivated for nut production and the nuts are mainly used for eating out of hand as fresh, dried, and roasted with or without salt and flavorings. The pistachio is unique in the nut trade because of shell splitting naturally before harvesting. This advantage allows pistachio nuts to be marketed extensively in-shell for fresh consumption, because their kernels can be easily separated without mechanical cracking. It also enables the processor to roast and salt the kernel without shell removal while almonds, walnuts and pecans are generally sold shelled to the industrial trade. In the United States, after roasting and salting of raw pistachio nuts, the shell is colored with a red dye to cover shell stains and blemishes and sold as ‘Red’ pistachios. Pistachio nuts are also used in pastries, cakes, ice creams, confections, baked goods, candies, sausages and desserts. Pistachio is an excellent taste enhancer and can be added to many food products to improve nutrition, color and flavor. The utilization of pistachio nuts in the producing countries are more varied than in the importer countries. In Iran, the hulls are used for fertilizer, feed for ruminants and small amounts are made into a flavorful marmalade (Mohammadi Moghaddam et al., 2009). A small amount of pistachio oil is produced for eating and use in cosmetics, while a limited amount of pistachio is also used for production of pistachio butter (Taghizadeh and Razavi, 2009). This butter, a semisolid paste, is made from ground and roasted pistachio kernels with addition of some flavorings and sweeteners. Pistachio butter is a nutritive product rich in lipids, proteins, carbohydrates and vitamins, and can be used in different food products such as cookies, ice creams and cakes. The hull is used for dyeing and tanning in India. 11.1.5 Worldwide importance and economic value World commercial production of pistachio nuts increased more than tenfold, from 47 584 tonnes in 1970 to 517 823 tonnes in 2007 (FAOSTAT, 2009). Pistachio nuts are produced commercially in 18 countries on 608 729 hectares. According to the Food and Agriculture Organization (FAO), the top six pistachio producers in 2007 were Iran at 230 000 tonnes (44.4% of the world’s production), followed by the United States (108 598 tonnes, 20.97% share), Turkey (73 416 tonnes, 14.18% share), Syria (52 066 tonnes, 10.05% share), China (38 000 tonnes, 7.34% share) and Greece (9 000 tonnes, 1.7% share). Pistachio production in Iran, Turkey, Syria, China and Greece increased 4.14, 1.56, 3.93, 1.15 and 7.14-fold, respectively from 1970 to 2007. As shown in Fig. 11.2, Iran’s production has been the key factor driving the global growth trend. However, production of the United States increased from 0 in 1970 to 108 598 tonnes in 2007, making it the second highest world producer after Iran. Alternate bearing, blanking and non-splitting are three physiological disorders that affect the fluctuation of commercial yield. Plantings have recently increased dramatically in the major producer countries of Iran, United States and Turkey. For example, pistachio production in the United States has increased from 688 bearing hectares in 1977 to 46 136 in 2007. In Iran,

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Global, Iran and United States pistachio production from 1970 to 2007.

it increased from 47 000 to 440 000 hectares during the same period. Although pistachio production has been initiated in countries such as Australia, Mexico, Argentina and South Africa, their production numbers have not reached competitive levels. Average yield per tree ranges from 2 to 22.5 kg/year. An average 3 kg of unshelled nuts yield 1 kg shelled. In 2000, world yields varied from 500 kg.ha−1 to 3037 kg.ha−1 with an average of 1117 kg.ha−1 (Kaska, 2002). Duke (2001) reported yields from 2 to 8 kg unshelled nuts per tree or 200 to 800 kg.ha−1 for 8 to 15 year old trees and 8 to 30 kg per tree or 800 to 2400 kg.ha−1 for 16 to 30 year old trees. Global pistachio export has increased from 13 531 tonnes (valued $1.36 million) in 1970 to 313 372 tonnes (worth $1.36 billion) in 2007. Iran and Turkey has been the major exporter in 1970 with 74 and 25% of world exports, respectively. Figure 11.3 shows the major exporters of pistachio nuts in 2006. According to FAO, Iran was the leading exporter of pistachio nuts in 2006 with 163 431 tons or 55% of global export followed by the United States with 48 571 tonnes or 17% of world export. Most export of Iranian pistachio is bound for Hong Kong, Germany, United Arab Emirates, Russia, Spain, Italy and India. Some of Iranian pistachio markets are also major exporter such as Hong Kong and Germany although they were among the top global pistachio importers in 2006 (Fig. 11.4). As many of these countries are not pistachio producers, it proves that trans-shipment or further processing occurs often with this commodity. Hong Kong and Germany are the major trans-shipper of pistachio nuts. In 2006, Germany imported pistachio valued at $199 million, primarily from Iran and the United States and exported pistachios valued at $106 million to other European countries.

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Fig. 11.3 The leading global exporters of pistachio nuts 2006.

Fig. 11.4 Top global importers of pistachio in 2006.

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11.1.6 Composition, nutritional value and health benefits Pistachio nuts are highly valued for their nutritional, sensory and health attributes. In addition to being high in unsaturated fatty acids and low in saturated fatty acids, they are good sources of proteins, dietary fibers, vitamins, minerals and antioxidant phytochemicals. Nutritionally, pistachio nuts are better than other tree nuts and peanut because they are lower in calories and fat content and higher in protein, carbohydrate and potassium. The composition of pistachio nut may vary depending on variety and maturity at harvest time. Tables 11.1–11.3 present the chemical composition and nutritional value, fatty acid and amino acid profiles of two varieties of pistachio nut. Mono- and poly-unsaturated fatty acids constitute more than 80% of pistachio oil. Carbohydrate analysis of pistachio has indicated the predominant sugar to be sucrose followed by raffinose, glucose, fructose, maltose and stachyose with traces of isomaltose and cellobiose (Kashani and Valadon, 1984). The globulin fraction is the major protein in the pistachio, contributing about two-third of the total protein (66%). Albumins are second in predominance to globulins, contributing 25% of the total protein, followed by glutelins (7.3%) and prolamins (2%) (Shokraii and Esen, 1988). All essential amino acids are present in pistachio where lysine is present at a high level and with only cystine in a limited amount. Pistachio nut contains substantial levels of a diverse range of phytochemicals such as carotenoids (lutein), phytosterols and phenolic compounds (flavonoids and resveratrol) in the kernel and skin. The presence of anthocyanins in pistachio nut is a unique characteristic that causes the red-purple color in the skin of the pistachio. Anthocyanins are water-soluble pigments that impart the attractive red, Table 11.1 Chemical composition of two varieties (‘Ohadi’ from Iran and ‘Kerman’ from the USA) of pistachio nut Component (unit)

Moisture (%) Oil (%) Protein (%) Carbohydrates (%) Crude fiber (%) Ash (%) Potassium (mg 100 g−1) Phosphorus (mg 100 g−1) Iron (mg 100 g−1) Calcium (mg 100 g−1) Magnesium (mg 100 g−1) Sodium (mg 100 g−1) Copper (mg 100 g−1) Energy (kcal 100 g−1)

Variety Ohadi

Kerman

2.54 57 20.8 13.8 1.93 2.6 1170 560.5 10.3 179.3 102.6 10.7 1.3 570

3.97 44.44 20.61 27.97 1.03 3.02 1025 490 4.15 107 121 1 ______ 557

Source: Shokraii (1977); USDA (2006).

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Postharvest biology and technology of tropical and subtropical fruits Table 11.2 Fatty acid profile of two varieties (‘Ohadi’ from Iran and ‘Kerman’ from the USA) of pistachio nut Amount (%)

Fatty acid

C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C18:4 C20:0 C22:0

Ohadi

Kerman

____ 13.4 2.0 1.0 49.5 31.8 Trace 2.2 _____ _____

Trace 12.59 0.52 0.90 57.48 27.93 0.57 _____ Trace Trace

Source: Shokraii (1977); Clarke et al. (1976).

Table 11.3 Amino acid profile of two varieties (‘Ohadi’ from Iran and ‘Kerman’ from the USA) of pistachio nut Percent total amino acids

Amino acid

Alanine Arginine Aspartic acid Cystine Glutamic acid Glycine Histidine lsoleucine Leucine Lysine Methionine Phenyl-alanine Proline Serine Threonine Tryptophan Tyrosine Valine

Ohadi

Kerman

4.00 9.70 8.80 2.60 20.60 4.50 2.30 4.10 7.00 5.70 1.50 4.90 3.80 5.60 3.20 1.40 2.90 5.60

5.46 1.91 9.54 1.72 22.70 5.23 1.94 4.79 8.11 11.04 2.07 4.74 4.64 3.71 3.95 _____ 2.80 6.46

Source: Shokraii (1977); Clarke et al. (1976).

blue and purple colors of various fruits and many colorful vegetables. Pistachio anthocyanins are present as glycosides of cyanidin and include cyanidin-3galactoside (major; 696 μg.g−1) and cyanidin-3-glucoside (minor; 209 μg.g−1) (Seeram et al., 2006).

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Many studies have indicated that a diet containing pistachio nut can reduce the risk of coronary heart disease (CHD). Aside from their mono-unsaturated fatty acids and fibers, pistachio nuts are rich sources of antioxidant phytochemicals, which promote heart health by inhibiting the absorption of cholesterol from the intestine through direct competition with uptake mechanisms. Recent studies have shown that a diet that incorporates pistachio nuts can reduce the total cholesterol, total cholesterol/HDL cholesterol ratio, and low density lipoprotein/ high density lipoprotein ratio significantly, and also decrease the plasma malondialdehyde, an important indicator of lipid peroxidation (Sheridan et al., 2007). Several studies have indicated that regular consumption of pistachio nuts does not lead to remarkable weight gain. The results have shown that those who eat pistachio nut more frequently are leaner and have a lower body mass index (BMI) than the infrequent nut eaters, even though their energy intake is higher (Cotton et al., 2004). It has also been proven that regular consumption of pistachio nuts lowers the blood pressure and therefore might be recommended for hypertension. They reduce the absorption of glucose and lower the blood sugar. As a result of many vitamins and minerals, they are especially recommended for children for a healthy physical and mental development. Pistachio nuts are also a good source of vitamin E which boosts the immune system and alleviates fatigue. These days, it is strongly recommended to consume foods with minimal processing in order to gain maximum health benefits. Other than drying at low temperatures and sometimes roasting, no other treatment is commonly applied to pistachio. Therefore, fatty acids, minerals, vitamins and other nutritional compounds are retained at a maximum level. Pistachios have been reported as a folk remedy for scirrhus of the liver, abdominal ailments, abscess, amenorrhea, bruises, sores, trauma and dysentery. 11.1.7 Physical, mechanical and thermal properties of pistachio nuts Physical, mechanical and thermal properties of pistachio nut and its kernel are important in the design of equipment for harvesting, handling, processing, transportation, sorting, separation, packaging and storage. Designing equipment without taking these into consideration may yield poor results. Size, shape and dimensions of pistachio nut and kernel are important in sizing, sorting, sieving and other separation processes. Densities of pistachio nut and kernel are necessary to design the equipment for processing and storage such as hullers, dryers and bins. The porosity affects the resistance to airflow through bulk pistachio nuts and packing characteristics. Physical properties also affect the hydrodynamic and pneumatic conveying characteristics of pistachio nut and kernel. During harvesting, handling, processing and storage of pistachio nut, the product exerts frictional forces on machinery components or storage structures. The magnitude of these frictional forces affects the amount of power required to

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Fig. 11.5 Schematic of three major perpendicular dimensions of pistachio. The dotted lines represent the kernel inside the nut.

convey the material. The static coefficient of friction is useful to determine the angle at which chutes must be positioned to achieve a consistent flow of material through the chute. Terminal velocity is very critical in the design of the pneumatic conveyor, transporting pistachio nut and kernel using air and separation of pistachio nut and kernel from undesirable materials such as shells, hulls, leaves, blank pistachios and small branches. The terminal velocity is affected by the density, shape, size and moisture content of pistachio nuts. Mechanical properties such as rupture force, deformation and rupture energy are used to design equipment for shelling and grinding of pistachio nut. Thermal properties of pistachio nut, in particular specific heat, are used to design a new unit operation or to analyze current processes such as drying and storage. Moisture content and variety are the most important factors affecting the physical, mechanical and thermal properties of pistachio nut and kernel. Table 11.4 describes some physical properties of pistachio nut as a function of moisture content. The mathematical relationship between physical properties and moisture content are also presented in this table. In these measurements, length, width and height have been defined as the distance from the calyx end to the stem, the maximum diameter, and the distance from the highest point to the lowest point of pistachio nut when positioned on a horizontal plate, respectively (Fig. 11.5).

11.2

Physiological disorders

Blanking, non splits and alternate bearing are the three main physiological disorders related to fruiting of pistachio nuts. Blanks are nuts without kernels and occur when the embryo fails to develop and can take place during nut setting and nut filling. Promotion of shell development from ovary tissues without successful fertilization causes blanking in nut setting phase. Blanking may also occur during kernel growth when the tree cannot provide sufficient assimilate to complete

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Length (L) (mm) Width (W) (mm) Height (H) (mm) Sphericity (φ) (%) Unit mass (M) (g) Volume (V) (cm3) True density (ρt) (kg m−3) Bulk density (ρb) (kg m−3) Porosity (ε) (%) Emptying angle of repose (θe) (°) Filling angle of repose (θf) (°) Static coefficient of friction for rubber (μ) Rupture force (N) along the length (FL) Rupture force (N) along the width (FW) Rupture force (N) along the height (FH) Rupture energy (mJ) along the length (EL) Rupture energy (mJ) along the width (EW) 58.61–42.94 37.24–25.57 42.65–35.14 69.17–46.95 40.48–28.73

6.31–35.57

FW = −0.8965 Mc + 97.24

90.31–60.57

112.31–82.59 FH = −0.9348 Mc + 118.08 6.31–35.57 256.78–182.66 EL = −2.3512 Mc + 272.63 6.31–35.57 157.46–101.39 EW = −1.7335 Mc + 170.98 6.31–35.57

5.77–39.11

5.77–39.11

5.77–39.11

5.77–39.11

l = 0.0170Mc + 12.9176 w = 0.0447Mc + 8.8088 h = 0.0384Mc + 8.6632 φ = 0.0026Mc + 0.7432 M = 0.520 + 0.011Mc V = 0.622 + 0.011Mc ρt = 858.7 + 0.13Mc ρb = 572.73 + 0.19Mc ε = 33.24–0.04Mc θe = 0.1367Mc + 25.330

Equation

(Continued)

Ew = −0.3667 Mc + 42.88

El = −0.6261 Mc + 72.75

Fh = −0.2440 Mc + 44.42

Fw = −0.3398 Mc + 38.90

Fl = −0.4946 Mc + 61.93

24.50–27.02 θf = 0.0855Mc + 24.030 0.393–0.647 μ = 0.0083Mc + 0.3505

136.23–98.84 FL = −1.0904 Mc + 143.01 6.31–35.57

5.33–34.78 5.44–34.78

5.77–39.11

θf = 0.0896Mc + 15.155 μ = 0.0044Mc + 0.4687

13.1–13.6 8.1–9.8 8.8–9.7 82.5–74.8 0.547–0.873 0.634–1.013 860–864 574–581 61.65–49.86 26.17–30.39

15.72–18.47 0.497–0.633

5.30–34.80 5.30–34.80 5.30–34.80 5.30–34.80 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.78

5.44–34.78 5.44–34.78

L = 0.0335Mc + 16.6630 W = 0.0178Mc + 11.8664 H = 0.0251Mc + 11.954 ----------------M = 0.94 + 0.019Mc V = 1.13 + 0.020Mc ρt = 857.6 + 0.29Mc ρb = 551.38 + 2.56Mc ε = 35.30–0.24Mc θe = 0.2148Mc + 20.345

16.9–17.8 12.1–12.7 12.3–12.7 79.3–79.8 1.105–1.680 1.291–1.873 860–869 573–649 60.59–47.75 21.54–28.32

Value

5.40–34.80 5.40–34.80 5.40–34.80 5.40–34.80 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.44–34.78

MC (% w.b.)

Equation

MC (% w.b.)

Value

Kernel

Nut

Some physical, mechanical and thermal properties of pistachio nut and kernel of the ‘Ohadi’ variety as function of moisture content

Property (unit)

Table 11.4

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Continued

9.8–12.0 0.705–2.567 2.4–1.1 38.26 43.54

4.00–36.30 5.12–33.86

5.40–34.80

56.35–42.28

Value

Eh = −0.4929 Mc + 59.83

Equation

S = −0.0407Mc + 3.0342

--------------- ----------------- -----------------

Vt = 0.23Mc + 10.56 3.50–36.30 9.0–10.0 Vt = 0.17Mc + 9.53 Cp = 0.9310 ln(Mc)–0.7748 --------------- ----------------- -----------------

213.92–145.07 EH = −2.1427 Mc + 226.97 6.31–35.57

5.77–39.11

MC (% w.b.)

Equation

MC (% w.b.)

Value

Kernel

Nut

MC = moisture content (% w.b.). Source: Kashaninejad et al. (2006); Razavi and Taghizadeh (2007); Razavi et al. (2007a; 2007b; 2007c; 2007d); Nazari Galedar et al. (2009).

Rupture energy (mJ) along the height (EH) Terminal velocity (Vt) (m s−1) Specific heat (Cp) (kJ kgK−1) at 25 °C Shell splitting (S ) (mm) Hull/nut ratio Shell/nut ratio

Property (unit)

Table 11.4

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development of its entire crop. Insufficient irrigation and inadequate boron leaf levels were also reported as causes of blank formation in pistachio nuts (Freeman and Ferguson, 1995). Shell splitting is a unique characteristic of pistachio nuts compared with other nuts and significantly important for pistachio quality because it affects the price and marketability of the product. Splitting is one of the maturation criteria and continues with kernel growth through maturity. Nut splitting can be reduced by water stress late in the growing season. Harvest time and boron nutrition are also important factors affecting nut splitting. Heating in the drying process will decrease the moisture content of shells and increase the splitting of nuts. Non-split nuts are usually separated after processing of fresh nuts and cracked and sold as kernels for processing into mixed nuts or ice cream. Pistachios are strongly alternate bearing and produce heavy crops every other year, fluctuating with no or little crops in ‘off’ years. Carbohydrate competition is probably the cause of this phenomenon so that carbohydrate depletion prevents floral initiation in the summer of an ‘on’ year. Inflorescence buds develop partially but abscise during heavy crop years and inhibit to produce a heavy crop in the next year. Like blank production, rootstock has a significant effect on alternate bearing. Studies indicated that blanking and shells splitting are related to ‘on’ and ‘off’ crop years. Blanking is much higher in ‘off’ years and non-split nuts are much more common in ‘on’ years, while crop load is much higher in ‘on’ years (Freeman and Ferguson, 1995).

11.3

Postharvest pathology and mycotoxin contamination

Several fungi have been identified to infect pistachios and some of them cause considerable damage to the hull and kernel. Alternaria causes black spots on the hull that are sometimes surrounded by red margins causing shell staining and mold in the kernel in early split nuts or fruits with cracked hull. Saprophytic fungi such as Alternaria, Aspergillus, Cladosporium, Fusarium and Penicillium are associated with shell staining, consequently infecting and causing decay to kernels of pistachio nuts (Michailides et al., 1995). The greatest postharvest damage of pistachio nuts is from Aspergillus flavus and Aspergillus parasiticus. These fungi produce aflatoxin. They are among the most potent mutagenic substances known to result in liver cancer. As the pistachio nuts grow on the trees, aflatoxin producing fungi can infect the kernels. However, the hull covering the shell usually remains intact and protects the kernel from invasion by molds and insects. Damaged hulls or nuts with poor protection by hulls are most prone to fungal infection. Sometimes the hull is attached to the shell and both split together. This hull rupture often referred to as ‘early splitting’, exposes the kernel to mold and insect infestations. The proportion of early split pistachio nuts is usually 1–5%, although it can be as high as 30% in some situations. The navel orangeworm (Amyelois transitella) is the major insect problem that usually infests nuts with ruptured hulls, and high levels of aflatoxin

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contamination have been reported in insect-damaged kernels. Doster and Michailides (1994) in their study on California pistachios reported that early split nuts had over 99% of the aflatoxin detected and navel orangeworm infected nuts had substantially more infection by several Aspergillus species as well as over 84% of the aflatoxin detected. Very late harvest, bird damage and cracking also result in hull rupture and infection of kernels with Aspergillus molds at low levels. In addition to increasing aflatoxin production in infected nuts after harvest, early split and damaged nuts that are not infected on the trees may become infected during harvest, transport, handling and storage. High temperature and humidity within the bulk pistachio nuts during transport and storage can provide the best conditions for infection of early split and damaged nuts. Infected nuts will provide a source of inoculum for the spread of fungi to sound nuts under inappropriate storage conditions or during inadequate processing, thus increasing the incidence and level of aflatoxin contamination. Mold contamination and aflatoxin production can be prevented to ensure that contaminated nuts do not enter the food chain (Joint FAO/WHO Food Standards Program, 2002). This prevention program should consider the different steps before and after harvest until the nuts reach the consumers. Using cultivars with lower early split nuts, reducing inoculum sources such as fallen fruits and inflorescence from trees, burying or removing pistachio litter, manipulation of irrigation, application of microorganisms or saprophytic yeasts as biocontrol agents and minimizing insect damage such as navel orangeworm are the main approaches to prevent contamination of nuts before harvest. At harvest, pistachios should not be in contact with the orchard floor to avoid infection. Delaying harvest should be avoided to prevent more aflatoxin production in the infected pistachio nuts. The nuts should be transported to the processing plant and hulled and dried as soon as possible after harvest because of high temperature and relative humidity within the bulk pistachio nuts that provide the best conditions for further contamination. If temporary storage of fresh pistachio nuts at the processing plant is necessary, they should be stored at 0 °C and lower than 70% relative humidity. Drying at high temperature will probably kill the aflatoxin-producing fungi but it has little effect on the aflatoxin already present. Drying to appropriate moisture content (5–7%) or water activity (less than 0.7) will prevent the growth of these fungi. Aflatoxin producing fungi will not be able to grow and produce aflatoxin in dried pistachio nuts stored at 25 °C and relative humidity lower than 70% for a long time. Since nuts infected by molds and contaminated with aflatoxin have some distinct physical properties such as dark stain and hull adhesion compared to sound nuts, they can be easily machine sorted.

11.4

Postharvest handling practices

11.4.1 Maturity criteria and harvest time Although pistachios are traditionally harvested when the hull separates easily from the shell, ideal harvest time and optimum maturity is determined by

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several criteria such as compositional and visible changes. Moisture content of the kernels decreases continually throughout maturation and stabilizes at full maturity, while fresh and dry weights of the kernel increase with maturity and reach a peak at harvest time. Respiration rate and total protein content decrease throughout maturation, and ether-extractable fat and total sugar content reach a peak at optimum maturity. These compositional changes coincide with shell splitting and changing from translucent to opaque, although they are invisible because the fleshy hull covers the shell in the developing nuts. Color change of the hull is a visible evidence of maturation, which is green in immature nuts and progresses to ivory to rose with optimum maturation (Labavitch et al., 1982). The percent of blank and immature fruits decrease throughout maturation and is minimal at optimum maturity. When fully mature, the nut will be separated from the hull easily when the fruit is pressed between the thumb and fingers at the hull’s distal end. Activity in the abscission zones between the nuts and the rachis is another evidence of maturation. At this status, fruit removal force will decrease and nuts will easily detach by gentle shaking (Ferguson et al., 1995). Like other fruits, maturation does not occur evenly throughout the tree. Therefore, the optimum harvest time is when the maturity criteria are observed at 70 to 80% of fruits. Based on all mentioned criteria, mid- to end of September was determined as the best harvest time for ‘Ohadi’, ‘Kalle-Ghouchi’, ‘Ahmad-Aghaei’ and ‘Badami’ varieties in Kerman province, Iran. The harvest time for these varieties may be different in other regions. Optimum harvest time is very important in maintaining nut quality; harvest should not be delayed because this will increase losses to navel orangeworm (NOW, Amyelois transitella), birds and fungi (in particular Aspergillus flavus), as well as shell staining due to breakdown of the phenolic compound-rich hull tissues. Early harvest leads to weight loss and decreases the shelf life of freshly harvested pistachios. 11.4.2 Harvest operations Pistachio trees are grown on traditional plantations and the lack of space between trees and rows necessitates harvesting by hand in Iran, Turkey and Syria. Pistachio clusters are harvested by laborers and dumped into sacks. The sacks are collected into plastic bins and transported to processing plants by trucks or trailers. In the United States, young trees (less than six years old) are hand harvested by knocking the trunk or striking the branches onto tarps spread under the trees, while mature pistachios are mechanically harvested onto a catching frame. Since orchard soils have potential to contaminate the pistachios with Aspergillus flavus, it is very important to prevent dropping the pistachios to the floor during mechanical harvesting. As well, any mechanical damage during harvesting should be avoided because pistachio hulls are fragile and susceptible to injury; shell staining will intensively increase in pistachios with damaged hulls. Pistachios also require more careful handling due to their higher moisture content at harvest than other tree nuts.

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11.4.3 Postharvest storage Shell staining and decay incidence are the major deterioration after harvest if the nuts are left in the hull for a long time, particularly at high temperatures. Most of the heating of bulk freshly harvested pistachio nuts is due to respiration. The maximum respiration rate of unhulled pistachio nuts is 125 mLCO2.kg−1.h−1 at 20 °C (Thompson et al., 1997). This level of respiration would produce a heating rate of about 0.7 °C per hour. Roughly handled, pistachio nuts can be held for at least 32 hours at 25 °C without significant increases in light or dark shell staining. At 30 and 40 °C, shell staining can occur in 24 hours and less than 16 hours, respectively, and accelerates specially beyond these time durations. Gently handled pistachio nuts with intact hulls may be held for up to 48 hours at ambient conditions without significant increase in staining. Ambient air circulation in bulk pistachio nuts or keeping them in a cold place are the best methods to prevent heat increase and retard shell staining if delays are unavoidable before processing (Thompson et al., 1997). Fresh unhulled pistachio nuts can be stored up to six weeks at 0 °C and 70–75% relative humidity without any significant effects on appearance, flavor quality, composition and hull removal. Storage at higher temperatures results in more incidence of surface molds and shell staining. An adequate air flow rate (0.1 Ls−1kg−1) through nuts during storage is essential to minimize losses. Sorting the nuts before storage to eliminate defective nuts (which are much more susceptible to decay), leaves and debris helps to increase the shelf life of fresh pistachio nuts. Hulled pistachio nuts have a shorter shelf life because the hull protects the nut from decay organisms without affecting shell quality. Hulled fresh pistachio nuts can be held for up to three weeks at the best storage conditions (0 °C and 40–50% relative humidity). Increasing the relative humidity to 90% shortens the storage of hulled pistachio nuts to 2 weeks at 0 °C, 1 week at 5 °C, 4 days at 10 °C, 2 days at 20 °C and 1 day at 30 °C. After two weeks storage at 0 °C and less than 10% relative humidity, the moisture content decreases to 7% and hulled nuts are almost completely dry. Although freezing has no significant effects on kernel texture, its influence on flavor quality eliminate it as an alternative for extending shelf life of fresh hulled nuts (Kader et al., 1978; 1979).

11.5

Processing of fresh pistachio nuts

Proper and quick processing after harvest is very important for pistachio quality and its marketability. For hundreds of years, pistachio nuts were processed manually. After harvesting the ripe pistachios, are hulled by hand. Workers perform this job so fast and skillfully that it is very difficult to see the procedure even at close observation. In some regions pistachio nuts are hulled right away after harvest, but in other regions they are dried in the hull for later hulling at a convenient time. Sometimes the pistachio nuts are immersed in water to separate the hull easily when squeezed between fingers. Pistachio nuts are then spread on

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a concrete or earth floor in the sun to dry. These processing methods usually result in nuts with stained shells and lower quality. During the last 30 years, traditional methods have extensively been improved in the leading producer countries and now pistachios are mechanically hulled and processed within a short time. Figure 11.6 indicates the processing procedures using two methods when freshly harvested pistachios arrive at the processing plant (Nakhaeinejad, 1998). Separation of blank pistachios is the main difference in these methods. Further processing of dried pistachio nuts may be accomplished immediately at harvest season or later as indicated in Fig. 11.7. 11.5.1 Hulling Hulling must be accomplished as soon as possible to reduce the chances for fungal growth and to avoid shell staining. The hull of the freshly harvested and mature pistachio nuts slip off fairly easily. Generally, different types of machines are used satisfactorily for hulling pistachios. Cylindrical hullers are more popular and economic and are used at different sizes and capacities to hull pistachios in various regions of Iran. The cylindrical huller consists of two concentric metallic cylinders and the inner cylinder rotates inside the stationary outer cylinder. The outside surface of the inner cylinder and inside surface of the outer cylinder are covered by parallel rings or slabs that are positioned at certain points. Pistachio nuts are fed continuously between the two cylinders and the hulls are separated from nuts

Fig. 11.6 Scheme processing procedures of freshly harvested pistachio nut. Left: processing by air flow tank. Right: processing by water float tank.

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Fig. 11.7

Processing procedures of dried pistachio nut.

after impacting the rings. Basically, this is a dry hulling method wherein pistachio nuts are hulled without water, an important advantage for pistachio growers and processors in dry regions. In rubber machines, the pistachios are rubbed between two rubber drums and the hulls are separated from the nuts. This machine does not damage mature pistachios but is unable to peel unripe pistachios, which are easily separated in the next stages. The abrasive peeler is another machine that produces an attractive product but is limited to a batch of nuts at a time. This small machine is suitable for small-scale production because it is unable to hull large volumes of pistachios that are being produced currently in pistachio orchards. It consists of a vertical cylinder with its inside coated by an abrasive material; a rotating disc at the bottom of the cylinder is also coated with the same abrasive. Pistachios are thrown by the centrifugal force of the rotating disc against the abrasive wall surface; the disintegrated hulls are removed from the peeler by a water stream that is introduced from the top of the cylinder. In the United States, pistachios are hulled in machines that consist of two parallel rubberized belts rotating in the same direction but at different speeds. After the hulling process, undesirable materials including hulls, branches, leaves, shells, broken nuts and kernels, blank and unripe pistachios, unpeeled pistachios and small pistachios are separated from the hulled nuts quickly to promote quality and marketability of the final product and also to avoid fungal growth. The separation of undesirable materials takes place at several stages using proper devices such as air leg, water or air flow tank, a stick tight separator and picking or inspection tables. 11.5.2 Trash and debris removal Although most of the hulls, branches and leaves are separated from the nuts in the hulling process, a small amount of hull pieces, debris and bunches remain; they

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are separated at this stage using the air leg or air flow system. The remaining trash and debris do not exceed more than one percent of total materials separated in the huller. This process is based on the capacity of an air stream to lift particles against gravity. The effect depends on air velocity and the particle moisture content, shape, size and specific gravity. This apparatus contains a vertical column and a blower at the bottom that regulates the air flow rate and velocity. The air flows upward in the column from the bottom to the top and fractionates the undesirable materials and blank pistachios from hulled nuts based on their terminal velocity. 11.5.3 Washing Shell appearance is one of the most important characteristics of pistachio quality and marketability. Hull latex extracted after the hulling process includes some components that cause blemished appearance and consequently raise the cost and time for separation of stained nuts after the drying process. Shell staining can be greatly decreased by appropriately washing the hulled nuts and removing the latex from the shell after the hulling process. As the pistachios are moved forward in a layer by a particular steel conveyor during the washing process, high pressure water is sprayed on the pistachios. In addition to cleaning the nuts and removing the latex from shells, the remaining debris and trashes are also separated. Water consumption is minimal in this washing process which is an advantage for dry regions. 11.5.4 Separation of blank pistachio nuts The kernels of blank and immature pistachio nuts are usually not fully developed and most of them are empty. Thus, the ratio of kernel to nut and the mass of 100 nuts, particularly, the specific gravity of blank and immature pistachios is lower than fully mature pistachios. Water has been used as a media for separation of blank pistachios from ripe ones for many years. When hulled pistachio nuts after the washing process are immersed in the water tank, all blank pistachios will float and most (about 60 to 80%) of the split and fully mature nuts will sink. The floaters also consist of unsplit nuts with less than 15% meat content (Woodroof, 1979). The air entrapped between the shell and the kernel of some fully split pistachio nuts reduces their specific gravity and consequently they float with blank pistachios. Separation efficiency can be improved by the installation of a stirrer or propeller in the water tank to remove the air entrapped between the shell and the kernel in the split and mature nuts. The floaters will be removed by water stream from the top of water tank and the sinkers will be taken out from the bottom of the tank employing a steel conveyor. In some processing plants or regions where enough water is not available for the separation of blank pistachios, this process is accomplished by an air flow float tank called a ‘dry tank’ machine. Blank and immature pistachio nuts, small, undersized and broken pistachios, debris and tiny trashes are separated in this machine using air flow and vibration.

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11.5.5 Drying Drying is an important operation in pistachio processing. The moisture content which is as high as 40% (wet basis) in the freshly harvested nuts is reduced to about 4–6%. Drying time is a function of many parameters including dryer air temperature, ambient relative humidity, initial moisture content of pistachio nuts, drying stage, variety and drying method. Figure 11.8 shows the drying time and behavior of pistachio nut (‘Ohadi’ variety) at different temperatures in a thin layer dryer (Kashaninejad et al., 2007). The increase in the drying air temperature decreases drying time rapidly and consequently increases the drying rate. Drying curves shown in Fig. 11.9 demonstrate that drying of pistachio nuts occurs in the falling rate period. At higher air temperatures, two distinct drying periods can be detected, namely, an initial transitional nut warm-up period wherein a slight increase in the drying rate takes place, and a falling rate period characterized by a rapid decrease of the drying rate. At lower air temperatures, the falling rate period is only detected which suggests predominance of the internal diffusion phenomenon as the mass transfer controlling process. In the falling rate period, a high initial drying rate (with higher rates at higher temperatures) is observed followed by a gradual decrease as the material approaches the dried state. Initially, the drying rate is higher because the initial water for evaporation comes from regions near the surface. As the drying progresses, the drying rate decreases with decrease of moisture content because the water to be evaporated comes from parenchymal cells within the structure and must be transported to the surface. The falling rate region is indicative of an increased resistance to both heat and mass transfer through the inner cells. Table 11.5 shows the characteristics of different commercial dryers that are used for drying of pistachio nuts. Nowadays most processors prefer to use a

Fig. 11.8 Drying pattern of pistachio nut (‘Ohadi’ variety) at different air temperatures (air velocity = 1.5 m/s, relative humidity = 20%).

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Fig. 11.9 Drying rate of pistachio nut (‘Ohadi’ variety) at different air temperatures (air velocity = 1.5 m/s; relative humidity = 20%).

Table 11.5

Characteristics of commercial pistachio dryers

Dryer type

Average air temperature (°C)

Drying time (h)

Dimensions (m)

Bed depth (cm)

First stage

Second stage

Flat bottomed bin dryer

65

-------------

8

L = 2.0 W = 1.2 H = 0.5

40

Continuous column dryer

45

40

10

L = 5.0 W = 2.0 H = 4.0

30

Continuous belt dryer

55

40

9

L = 10.5 W = 6.7 H = 6.5

30

Vertical cylindrical dryer

55

-------------

8

H = 4.0 D1 = 0.5 D2 = 1.5

50

Funnel cylindrical dryer

80

-------------

5.5

H = 3.5 D = 2.0

300

L: length, W: width, H: height, D1: internal cylinder diameter, D2: external cylinder diameter, D: diameter.

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two-stage drying process as it uses less energy and increases the uniformity of drying of the nuts compared with the single stage process. Chemical composition and quality of pistachio nuts do not change significantly during the drying process but shell splitting increases and some of the closed shells split during drying because of moisture loss. In dryers with high nut depth, the pressure exerted by nuts in the upper layers may prevent the splitting of the shells in the lower layers (Kashaninejad et al., 2003). Drying air temperatures above 80 °C cause shells to split so widely that the nut drops out. Appropriate air temperature and uniform air flow distribution is very important to prevent potential of fungal growth during the early stage of drying. In some processing plants, sun drying may be used. Pistachio nuts are spread out in a thin layer 2–3 cm thick on a concrete floor under the sun and this requires about 48 hours at temperatures near 26 °C. Sun drying should be accomplished with protective cover to prevent access by birds and rodents. Pistachio nuts are planted in regions with plenty of sunshine during the harvest season. Therefore, solar energy is an advantageous alternative for drying of pistachio nuts in order to decrease the dependence of the drying process on fossil fuels. Ghazanfari et al. (2003) dried pistachio nuts by a forced air solar dryer to 6% moisture content for 36 hours. The maximum temperature in the solar collector reported was 56 °C, which was 20 °C above the ambient temperature. When air is forced through a layer of bulk pistachio nuts, resistance to the flow (the so-called pressure drop) develops as a result of energy lost through friction and turbulence. The resistance to airflow through bulk pistachio nut is an essential parameter to optimally design the forced ventilation systems for drying and also cooling the stored bulk. As well, the uniform and proper airflow distribution can prevent fungal growth during the drying process. Figure 11.10 shows the resistance

Fig. 11.10

Pressure drop of pistachio nut at different airflow rates and moisture contents.

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of bulk pistachio nuts at various airflow rates and moisture contents. Airflow resistance across a column of pistachio nuts increases linearly with increasing depth. The pressure drop through pistachio nut beds increases more rapidly with increasing airflow rate compared with bed depth (Kashaninejad et al., 2010). Airflow rate, moisture content and fill method affect the pressure drop, however airflow rate and fill method have greater influence on pressure drop of pistachio nut than moisture content. An increase in the moisture content in the range of 4.08–38.40% (wet basis) results in a 55% increase in the pressure drop across pistachio nut beds. The dense fill increases the bulk density which results in an increase in the airflow resistance of bulk pistachio nuts by 97% than that of loose fill (Kashaninejad and Tabil, 2009). 11.5.6 Storage of dried pistachio nuts Generally, nuts may be held for a long time (up to 2–5 years) if they are stored under optimum conditions but at unfavorable storage conditions, they may become inedible even within one month because of mold growth, off-flavor, rancidity, discoloration, absorption of undesirable flavors and insect infestation. Pistachio nuts dried to appropriate moisture content (4–6%) are very stable and can be stored for up to one year at 20 °C and 65–70% relative humidity without significant losses in quality attributes (Kader et al., 1982). No differences in chemical composition and sensory attributes were observed among nuts stored at different temperatures (0, 5, 10, 20 and 30 °C) for 12 months. Nuts held at 30 °C had lower moisture content and higher sugar content and rancid flavor than those stored at lower temperatures. Long storage potential of pistachio nut is a result of high oleic acid, natural antioxidants and reduction of moisture to monolayer moisture content during the drying process. Pistachios are more stable to rancidity and have a longer storage potential than other tree nuts such as almonds, pecans or walnuts. All these nuts are high in fat content, but walnut and pecan oils have a much higher content of polyunsaturated fatty acids than pistachio oil. For longer storage of pistachio nuts, low temperatures (between 0–10 °C) are recommended. Exclusion of oxygen, insect control through fumigation, vacuum packaging or N2 injection in packages and controlled atmospheres can maintain nut quality during storage. Storage under high concentration of CO2 (98%) and reduced O2 (less than 0.5%) provides good stability in terms of fatty acid loss and formation of peroxide and free fatty acids (Maskan and Karatas, 1998). Oxygen scavenger packaging is an efficient method to eliminate the oxygen content and retard the oxidation of pistachio nut during long storage. It has been reported that pistachio nuts stored in an oxygen scavenger system have a lower hexanal content than those in vacuum and atmospheric packaging (Leufven et al., 2007). Hexanal is an indicator of oxidation progress and is applied in various products to monitor quality deterioration. Wheat starch-based edible films are alternative packaging materials for pistachio nuts or kernels to improve the shelf life. The main advantage of edible films is the reduction of synthetic packaging materials, but they also retard peroxide formation and minimize water absorption during storage. Addition of

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PEG (polyethylene glycol) to wheat starch films enhances tensile and mechanical properties of the films (Forghani, 2008). Insect infestation is a potentially important problem during storage because the fungal infections often accompany insect damage. Fumigation with methyl bromide or phosphine has been used for disinfestation. Storage of nuts at temperatures near freezing (0 °C) or in 0.5% oxygen and 10% carbon dioxide also effectively kill all insects.

11.6

Processing of dried pistachio nuts

11.6.1 Separation of split from non-split pistachio nuts Non-splitting is one of the shell defects that affects marketability and the price of processed product, therefore the non-split nuts should be separated from split nuts before selling. Although some of the closed shells split during the drying process, non-splitting may comprise up to 30% depending on the variety. Closed shell nuts are separated from the open shell ones by mechanical devices called pinpicker or needle picking drums. In this machine, raw nuts are fed into a rotating drum that is covered by tiny needles or pins. Open shell nuts are picked by needles and lifted away with drum rotation and separated at the top of the drum by a brush. Closed shells nuts that are not picked by needles pass through the bottom of the drum and are collected at the other side of the rotating drum. 11.6.2 Grading of pistachio nuts Grading requirements for pistachio nuts in the shell, shelled pistachio nuts, artificially opened pistachio nuts and non-split pistachio nuts are available and used by the industry. The basic requirements of grading should be that nuts are free from foreign materials, loose kernels, shell pieces, particle and dust, and blank nuts. The grading criteria are divided into shell and kernel defects. Shell defects include any blemish affecting the appearance, edibility and/or marketing of pistachio nuts such as adhering hull material, light or dark stained shell, nonsplitting or splitting other than the suture, deformity and/or other damage. Kernel defects include immature kernels, rancidity, mold or decay and any damage or evidence of insects. Size and degree of dryness are also important quality attributes affecting grading. 11.6.3 Salting and roasting Pistachio nuts are mostly consumed salted and roasted in-shell. Salting and roasting tremendously enhance the flavor, color and texture of pistachio nuts and increase overall palatability of the valued products. Improvement of sensory attributes of pistachio nuts during roasting is a result of non-enzymatic browning or Maillard reaction which takes place between the reducing sugars and nitrogenous compounds, in particular amino acids and proteins. Nuts become

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Roasting procedures in a continuous nut roaster.

more crumbly and brittle during the roasting process, which are typical characteristics of roasted products. Figure 11.11 shows the roasting process diagram in a continuous pistachio roaster (Dadgar, 1998). Pistachio nuts are salted by soaking in salt solution in a rotary salting machine and rotation of the drum and appropriate residence time provide uniform salting. Seyhan (2003) reported that 20% (W/V) salt solution and 20 min soaking may be used for salting of pistachio nuts. The higher concentration of salt solution results in lower moisture absorption throughout the soaking process. Other additives such as lemon juice or saffron may be added to the salt solution to enhance flavor of the roasted product. The excess salt solution entrapped between the shell and the kernel is removed by vibration to promote efficiency of the dryer. As the pistachio nuts are turned around and moved forward on the steel belt dryer, surface salt solution and the moisture absorbed during salting are evaporated. Then pre-dried pistachio nuts are fed to the top of a threelayer steel belt roaster and discharged from the bottom to the steel belt cooler. Pistachio nuts are roasted at 145 °C and cooled at ambient temperature. The outlet air of the cooler is utilized in the dryer to improve efficiency of the system. Kashani and Valadon (1983, 1984) have investigated the effect of the common roasting method (drying at 70 °C for 1 hr and roasting at 145 °C for 20 min) on components and quality of pistachio nut. After roasting, an obvious increase in fatty acids (from 2.7 to 5.5 mg.g−1) and phosphatidic acid (from 0.8 to 2.7 mg.g−1) and a slight decrease in triglycerides (from 437.6 to 434.9 mg−1g) and choline compounds took place, while most of the other lipid components did not change. Although iodine value or malonaldehyde did not change significantly, peroxide value clearly increased (from 0.73 to 1.04 meqkg−1) during roasting. Increase in the peroxide value demonstrates that some of the pistachio oil was degraded during roasting. After roasting, the total available carbohydrates, starch, dextrin, and in particular total free sugars decreased significantly. Reducing sugars such as glucose and fructose almost disappeared. No significant effect was observed in

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total protein, but about 40% of free amino acids were degraded. Some free amino acids such as cysteine, histidine, arginine, methionine and tyrosine disappeared totally. Reduction in free amino acids and reducing sugars might be a result of taking part in a Maillard reaction.

11.7

References

Ak B E and Açar I (2001), ‘Pistachio production and cultivated varieties grown in Turkey’, in Padulosi S and Hadj-Hassan A, Project on Underutilized Mediterranean Species. Pistacia: Towards a Comprehensive Documentation of Distribution and Use of its Genetic Diversity in Central & West Asia, North Africa and Mediterranean Europe, Rome, Italy, IPGRI. Banifacio P (1942), II Pistacchio: Coltivazione, Commercio, Uso, Rome, Ramo Editoriale degli Agricoltori. Brothwell D and Brothwell P (1969), Food in Antiquity: A Survey of the Diet of Early Peoples, New York, Frederik A. Praeger. Clarke J A, Brar G S and Procopiou J (1976), ‘Fatty acid, carbohydrate and amino acid composition of pistachio (Pistacia vera) kernels’, Pl Food Hum Nutr, 25 (3/4), 219–225. Cotton P A, Subar A F, Friday J E and Cook A (2004), ‘Dietary sources of nutrients among US adults, 1994 to 1996’, J Am Diet Assoc, 104, 921–930. Crane J C (1978), ‘Quality of pistachio nuts as affected by time of harvest’, J Am Soc Hort Sci, 103, 332–333. Crane J C and Iwakiri B T (1981), ‘Morphology and reproduction of pistachio’, Hort Rev, 13, 376–393. Dadgar F (1998), Salting and Roasting Pistachios in Iran, Kerman, Momtazan Industrial Co. Doster M A and Michailaides T J (1994), ‘Aspergillus molds and aflatoxins in pistachio nuts in California’, Phytopathol, 84, 583–590. Duke J A (2001), Handbook of Nuts, Boca Raton, Florida, CRC Press. Esmail-pour A (2001), ‘Distribution, use and conservation of pistachio in Iran’, in Padulosi S and Hadj-Hassan A, Project on Underutilized Mediterranean Species. Pistacia: Towards a Comprehensive Documentation of Distribution and Use of its Genetic Diversity in Central & West Asia, North Africa and Mediterranean Europe, Rome, Italy, IPGRI. FAOSTAT (2009), FAOSTAT database, FAO statistics database on the World Wide Web. Available from: http://apps.fao.org (accessed December 2009). Ferguson L, Kader A A and Thompson J (1995), ‘Harvesting, transporting, processing and grading’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 110–114. Forghani M (2008), ‘Moisture uptake, rancidity and physical properties of wheat starchbased edible films as a new package’, Int J Food Safety, 10, 65–71. Freeman M and Ferguson L (1995), ‘Factors affecting splitting and blanking’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 106–109. Ghazanfari A, Tabil L G and Sokhansanj S (2003), ‘Evaluating a solar dryer for in-shell drying of split pistachio nuts’, Dry Technol, 21 (7), 1357–1368. Hadj-Hassan A (2001), ‘Cultivated Syrian pistachio varieties’, in Padulosi S and HadjHassan A, Project on Underutilized Mediterranean Species. Pistacia: Towards a Comprehensive Documentation of Distribution and Use of its Genetic Diversity in Central & West Asia, North Africa and Mediterranean Europe, Rome, Italy, IPGRI. Hendricks L and Ferguson L (1995), ‘The pistachio tree’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 7–9.

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Joint FAO/WHO Food Standards Program (2002), Discussion paper on aflatoxins in pistachios, 34th session, Rotterdam, The Netherlands, 11–15 March. Joret C (1976), Les plantes dans l’antiquité et au moyenvâge; histoire, usages et symbolisme, Genève, Slatkine Reprints. Kader A A, Heintz C M, Labavitch J M and Rae H L (1982), ‘Studies related to the description and evaluation of pistachio nut quality’, J Amer Soc Hort Sci, 107, 812–816. Kader A A, Labivitch J M, Mitchell F G and Sommer N F (1978), Quality and safety of pistachio nuts as influenced by postharvest handling procedures, The Pistachio Association Annual Report, CA, pp. 45–51. Kader A A, Labivitch J M, Mitchell F G and Sommer N F (1979), Quality and safety of pistachio nuts as influenced by postharvest handling procedure, The Pistachio Association Annual Report, CA, pp. 45–56. Kashani G G and Valadon L R G (1983), ‘Effect of salting and roasting on the lipids of Iranian pistachio kernels’, J Food Technol, 18, 461–467. Kashani G G and Valadon L R G (1984), ‘Effect of salting and roasting on the carbohydrates and proteins of Iranian pistachio kernels’, J Food Technol 19, 247–253. Kashaninejad M and Tabil L G (2009), ‘Resistance of bulk pistachio nuts (Ohadi variety) to airflow’, J Food Eng, 90, 104–109. Kashaninejad M, Maghsoudlou M, Khomeini M and Tabil L G (2010), ‘Resistance to airflow through bulk pistachio nuts (Kalleghochi variety) as affected by the moisture content, airflow rate, bed depth and fill method’, Powder Technol., 203, 359–369. Kashaninejad M, Mortazavi A, Safekordi A and Tabil L G (2006), ‘Some physical properties of Pistachio (Pistachia vera L.) nuts and its kernel’, J Food Eng, 72, 30–38. Kashaninejad M, Mortazavi A, Safekordi A and Tabil L G (2007), ‘Thin layer drying characteristics and modeling of Pistachio nuts’, J Food Eng, 78, 98–108. Kashaninejad M, Tabil L G, Mortazavi A and Safekordi A (2003), ‘Effect of drying methods on quality of pistachio nuts’, Dry Technol, 21(5), 821–838. Kaska N (2002), ‘Pistashio nut growing in the mediterranean basin’, Acta Hort, 591, 443–451. Kirkbride D (1966), ‘Beidha: an early neolithic village in Jordan’, Archaeol, 19, 199–207. Kramer C (1982), Village Ethnoarchaelogy: Rural Iran in Archaeological Perspective, New York, Academic Press. Labavitch J M, Heintz C M, Rae H L and Kader A A (1982), ‘Physiological and compositional changes associated with maturation of “Kerman” pistachio nuts’, J Amer Soc Hort Sci, 107, 688–692. Lemaistre J (1959), ‘Le pistachier (étude bibliographique)’, Fruits 14, 57–77. Leufven A, Sedaghat N and Habibi M B (2007), ‘Influence of different packaging systems on stability of raw dried pistachio nuts at various conditions’, Iranian Food Sci Technol Res J, 3 (2), 27–36. Maggs D H (1973), ‘Genetic resources in pistachio’, FAO Plt Genet Resources Newsletter 29, 7–15. Maskan M and Karatas S (1998), ‘Fatty acid oxidation of pistachio nuts stored under various atmospheric conditions and different temperatures’, J Sci Food Agric, 77, 334–340. Michailides T, Morgan D P and Doster M A (1995), ‘Foliar and fruit fungal diseases’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 148–159. Mohammadi Moghaddam T, Razavi M A, Malekzadegan F and Shaker Ardekani A (2009), ‘Chemical composition and rheological characterization of pistachio green hull’s marmalade’, J Texture Studies, 40, 390–405. Moldenke H N and Alma L (1952), Plants of the Bible, Waltham, Chronica Botanica. Nakhaeinejad M (1998), Pistachio Hulling and Processing in Iran, Kerman, Momtazan Industrial Co. Nazari Galedar M, Mohtasebi S S, Tabatabaeefar A, Jafari A and Fadaei H (2009), ‘Mechanical behavior of pistachio nut and its kernel under compression loading’, J Food Eng, 95, 499–504.

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Razavi M A and Taghizadeh M (2007), ‘The specific heat of pistachio nuts as affected by moisture content, temperature and variety’, J Food Eng, 79, 158–167. Razavi M A, Emadzadeh B, Rafe A and Mohammad Amini A (2007a), ‘The physical properties of pistachio nut and its kernel as a function of moisture content and variety: Part I. Geometrical properties’, J Food Eng, 81, 209–217. Razavi M A, Emadzadeh B, Rafe A and Mohammad Amini A (2007b), ‘The physical properties of pistachio nut and its kernel as a function of moisture content and variety: Part II. Gravimetrical properties’, J Food Eng, 81, 218–225. Razavi M A, Mohammad Amini A, Rafe A and Emadzadeh B (2007c), ‘The physical properties of pistachio nut and its kernel as a function of moisture content and variety: Part III. Frictional properties’, J Food Eng, 81, 226–235. Razavi M A, Rafe A and Akbari R (2007d), ‘Terminal velocity of pistachio nut and its kernel as affected by moisture content and variety’, African J Agric Res, 2 (12), 663–666. Rieger M (2006), Introduction to Fruit Crops, New York, Food Product Press. Seeram N P, Zhang Y, Henning S M, Lee R, Niu Y, et al. (2006), ‘Pistachio skin phenolics are destroyed by bleaching resulting in reduced antioxidative capacities’, J Agric Food Chem, 54, 7036–7040. Seyhan F G (2003), ‘Effect of soaking on salting and moisture uptake of pistachio nuts (Pistachia vera L.) from Turkiye’, GIDA, 28 (4), 395–400. Sheridan M J, Cooper J N, Erario M and Cheifetz C E (2007), ‘Pistachio nut consumption and serum lipid levels’, J Am Coll Nutr, 26, 141–148. Shokraii E H (1977), ‘Chemical composition of the pistachio nuts of Kerman, Iran’, J Food Sci, 42, 244–245. Shokraii E H and Esen A (1988), ‘Composition, solubility, and electrophoretic patterns of proteins isolated from Kerman pistachio nuts (Pistacia vera L.)’, J Agric Food Chem, 36 (3), 425–429. Taghizadeh M and Razavi M A (2009), ‘Modeling time-independent rheological behavior of pistachio butter’, Int J Food Properties, 12, 331–340. Thompson J F, Rumsey T R and Spinoglio M (1997), ‘Maintaining quality of bulk-handled, unhulled pistachio nuts’, App Eng Agric, 13, 65–70. USDA (2006), ‘National Nutrient Database for Standard Reference’, Release 19, National Technical Information Service, USDA, Springfield, VA. Whitehouse W E (1957), ‘The pistachio nut – a new crop for the western United States’, Economic Botany 11, 281–321. Woodroof J G (1979), Tree Nuts: Production Processing Products, Westport, Conn., AVI. Zohary M (1952), ‘Amonographical study of the genus Pistacia’, Palest J Bot, 5, 187–228.

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12 Pitahaya (pitaya) (Hylocereus spp.) F. Le Bellec and F. Vaillant, Centre for Agricultural Research and Development (CIRAD), France

Abstract: While pitahaya (Hylocereus spp.) was originally domesticated by preColumbian Americans, it was still practically unknown until the mid-1990s in most parts of the world. Pitahaya is now a member of the ‘small exotic fruits’ category in many shops, though it remains a minor player. This chapter gives an initial evaluation of the advantages and disadvantages of this new fruit. Commercially, pitahaya appear to have numerous selling points; pitahaya’s fruit is attractive in shape and color, and it has very good internal properties of high interest for the food industry. Key words: Hylocereus, pitahaya, botany, agronomy, chemical composition, storage, postharvest technology, uses, markets.

12.1

Introduction

Practically unknown fifteen years ago, pitahaya1 today occupies a growing niche in the exotic fruit market as well as in the domestic markets of producer countries, such as Vietnam, Malaysia, Colombia, Mexico, Costa Rica and Nicaragua. Elsewhere, pitahaya is considered to be a new, promising fruit species; it is cultivated on different scales in Australia, Israel, and Reunion Island (Le Bellec et al., 2006). This success can be explained in part by the fruit’s appealing qualities and characteristics (attractive color and shape) and by the commercial policies of some producing and exporting countries (e.g., Vietnam, Colombia and Israel). The generic term ‘pitahaya’ includes several different species, which can often be a source of confusion. Currently, only a few species of pitahaya are commonly found on the market: yellow pitahaya (Hylocereus megalanthus Bauer), a fruit with yellow skin and white pulp, and red pitahaya (Hylocereus spp. Britt & Rose), a fruit with a red skin and either white or red pulp. These species are native to tropical 1

Different spellings are used : pitaya, pitahaya, pitajaya, pitajuia, pitalla or pithaya

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and sub-tropical America. Up to now, available publications have dealt with very specific topics on the difficulties of introducing pitahaya as a commercial fruit, the principal research topics being genetics, floral biology, ecophysiology and fruit characterization (physico-chemical composition). The aim of our work was to draw up an exhaustive list of literature currently available on Hylocereus and to group the references by discipline (uses and marketing, botany, biogeography, floral biology, agronomy, postharvesting and composition).

12.2

Uses and market

The pulp of the fruit is refreshing and possesses a texture close to that of kiwi fruit. It is much appreciated, especially if chilled and cut in halves so that the flesh can be eaten with a spoon. The juice is enjoyed as a cool drink, while syrup made of the whole fruit is used to color candy and the pulp is also used in sorbet and fruit salads. Flowers can be cooked and eaten as a vegetable. Hylocereus spp. are also used for medicinal purposes and their leaves and flowers have traditionally been used by the Mayas in Latin America as a hypoglycemic, diuretic, and cicatrizant agent (Pérez et al., 2007). The medicinal uses are increasingly sought as reported in recent studies. An aqueous extract of Hylocereus exhibited positive protective microvascular activity and wound-healing properties in diabetic rats (Pérez et al., 2005), while Pérez et al. (2007) isolated and showed properties of two triterpenes from H. undatus in the protection against increased skin vascular permeability in rabbits. Khalili et al. (2009) suggested that the consumption of red pitahaya play a role in the prevention of cardiovascular disease. Pitahaya is widely consumed in South America and Asia, but it was unknown in the European Union and North America until the mid-1990s. The fruit is still a niche product, but imports have increased considerably in the last two years and pitahaya now has its place in the displays of retailers devoted to rare exotic fruits (Le Bellec et al., 2006) and the range of supplier countries is growing rapidly. Israel, with a major cost price advantage thanks to sea transport, competes with Asian suppliers during the second half of the year. The fruit attracts two different market segments. Asian customers purchase it quite regularly, with a peak at the Chinese New Year. On this occasion, it is not usually bought for its taste, but for its fine appearance because it is displayed as an offering to ancestors. The greatest demand is for large fruits. This success can be explained in part by the fruit qualities and characteristics and also by the commercial policies of some producing and exporting countries.

12.3

Botany, origin and morphology

12.3.1 Botany and genetic Pitahaya belongs to the vine cacti of the genera Hylocereus (Berger) Britt and Rose of the botanical family Cactaceae. Hylocereus is characterized as a climbing plant

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with aerial roots that bears a large, scaly, glabrous berry (Britton and Rose, 1963). Hylocereus spp. are diploid (2n = 22) except H. megalanthus (allotetraploid, 2n = 4x = 44) (Lichtenzveig et al., 2000; Tel-Zur et al., 2004b). In Latin America, many different cultivated species and fruits are referred to as ‘pitahaya’, a generic and vernacular name that renders their botanical classification difficult. However, all pitahaya are grouped into four main genera: Stenocereus Britton & Rose, Cereus Mill., Selenicereus (A. Berger) Riccob and Hylocereus Britton & Rose (Mizrahi et al., 1997). We focused particularly on the Hylocereus species (see Plate XXII in the colour section between pages 238 and 239). There are many contradictions concerning the botanical classification of Hylocereus that are reflected in the difficulty of characterization. This is due to similar morphological characteristics and/or environmental conditions between species. For example, Britton and Rose (1963) have created a genus (Mediocactus) to classify the yellow pitahaya (actually H. megalanthus) due to a description of the morphology of a species which has a triangular stem like that of Hylocereus, and spiny fruits like those of Selenicereus. Accordingly, they classified it into a separate genus named Mediocactus, thereby implying both an intermediate morphology and an intermediate taxonomic status. Recent studies help to clarify this botanical classification (Bauer, 2003; Tel-Zur et al., 2004b). In our paper, we use Bauer’s nomenclature. Thus, there are 15 species of Hylocereus, whose ornamental value is due to the beauty of their large flowers (15–25 cm) that bloom at night (see Plate XXII in the colour section). Even if all these species can potentially produce fruits, only five are cultivated for this purpose and our study was limited to those. The characteristics of these species are presented below and summarized in Table 12.1:

•

•

H. costaricensis (Web.) Britton & Rose is characterized by vigorous vines, perhaps the most robust of this genus. Stems are waxy white and flowers are margined; the outer perianth sediments are reddish, especially at the tips; and stigma lobes are rather short and yellowish. Its scarlet fruit (diameter: 10–15 cm; weight: 250–600 g) is ovoid and covered with scales that vary in size; it has a red purple flesh with many small black seeds, pleasant texture and good taste. H. megalanthus Bauer (syn. Selenicereus megalanthus) has long, slender and green stems; not horned. The areoles are white. Its yellow fruit (diameter: 7–9 cm; weight: 120–250 g) is oblong, covered with clusters of deciduous spines, black seeds; its edible flesh has a pleasant, sweet flavor.

Table 12.1

Peel and flesh colors of Hylocereus spp.

Species

Weight

Peel color

Flesh color

Common name

H. costaricensis H. megalanthus H. purpusii H. monocanthus H. undatus H. undatus subsp. luteocarpa

250–600 g 120–250 g 150–400 g 200–400 g 300–800 g 100–480 g

Red Yellow Red Purple Rosy-red Clear yellow

Red purple White Red Red purple White White

Red pitaya Yellow pitaya Red pitaya Red pitaya Dragon fruit –

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H. ocamponis (Weing.) Britton & Rose (syn. H. purpusii) has very large (25 cm) flowers with margins; outer perianth segments are more or less reddish; middle perianth segments golden, and inner perianth segments white. It produces scarlet, oblong fruit covered with large scales (length: 10–15 cm; weight: 150–400 g); red flesh with many small black seeds; and has pleasant flesh texture though not very pronounced. H. monocanthus Bauer (including H. polyrhizus) has very long (25–30 cm) flowers with margins; outer reddish perianth segments, especially at the tips; and rather short and yellowish stigma lobes. Its scarlet fruit (length: 10–15 cm; weight: 200–400 g) is oblong and covered with scales that vary in size; it has a red flesh with many small black seeds, pleasant flesh texture and good taste. H. undatus (Haw.) Britton & Rose (see Fig. 12.1) has long and green stems, more or less horned in the age margins. Flowers are very long (up to 29 cm), outer perianth segments are green (or yellow-green) and inner perianth segments

Fig. 12.1

Fruit of Hylocereus undatus (© F. Le Bellec).

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pure white. Its rosy-red fruit (length: 15–22 cm; weight: 300–800 g) is oblong and covered with large and long scales, red and green at the tips; it has a white flesh with many small black seeds, pleasant flesh texture and a good taste. A new subspecies of H. undatus subsp. luteocarpa from Mexico has been recently described, having yellow fruit with large foliaceous scales (De Dios, 2005). Many varieties of Hylocereus exist throughout the world, selected or not by humans. The custom of regarding fruit morphology and color is often the sole criterion for defining species. For example, a few varieties of H. costaricensis are known in Costa Rica as: ‘Lisa’, ‘Cebra’ and ‘Rosa’ (Vaillant et al., 2005). Recently, morphological variation was studied in 21 pitahaya genotypes in Mexico which allowed discriminating, by vegetative criteria, four groups within the species H. undatus (Grimaldo-Juárez et al., 2007). These authors conclude: ‘The variability of this group represents greater capacity to change in response to its environment, demonstrating different phenotypes, which are selected by man as suggested for yellow, red and magenta pitahaya’. This study has not been complemented by genetic analyses; perhaps they would have discovered subspecies as described by De Dios (2005) or hybrids. Indeed, reciprocal crosses among diploid Hylocereus species and the ease of obtaining partially fertile hybrids facilitates the creation of new variety (for natural or voluntary hybridization). For examples, Tel-Zur et al. (2004b) have created many hybrids for their experiment; to overcome the problems associated with self-incompatible varieties that are grown on Reunion Island, we have easily created a hybrid H. undatus × H. costaricensis, see Fig. 12.2 that allows the pollination of these two parents (Le Bellec et al., 2004). In conclusion, few studies seek to describe and characterize pitahaya varieties. The market reduces this apparent diversity to two colors of fruits: yellow and red!

Fig. 12.2

Hybrid of H. undatus (right) × H. costaricensis (left) (© F. Le Bellec).

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12.3.2 Origin, distribution and ecology of Hylocereus Most Hylocereus species originate principally from Latin America (probably from Mexico and Colombia), with others possibly from the West Indies (Britton and Rose, 1963). In these regions, pitahaya has been cultivated for many years. Ethnobotanical studies (Mesoamerican region) indicate Hylocereus species were domesticated by pre-Columbian cultures (Casas and Barbera, 2002) and have been a food source for inhabitants. Today they are distributed all over the world (in tropical and subtropical regions), but H. undatus is the most cosmopolitan species. In their region of origin, the fruits of Hylocereus sp. are the main traditional fruit and the most widely consumed local fruit (Mizrahi et al., 1997). The Hylocereus species is at present cultivated for fruit production in Cambodia, Colombia, Costa Rica, Ecuador, Guatemala, Indonesia, Malaysia, Mexico, Nicaragua, Peru, Taiwan and Vietnam, with more recent cultivation in Australia, Israel, Japan, New Zealand, Philippines, Spain, Reunion Island and the southwestern United States (Valiente-Banuet et al., 2007, Le Bellec et al., 2006). The robustness of Hylocereus species enables them to prosper under different ecological conditions. For example, in Mexico, they are found in very rainy regions (340 to 3500 mm year) and at altitudes of up to 2750 m above sea level (Mizarhi et al., 1997). They can survive in very hot climates, with temperatures of up to 38–40 °C (Le Bellec et al., 2006); nevertheless, in some species, temperatures below 12 °C can cause necrosis of the stems (Bárcenas, 1994). Hylocereus species are semi-epiphytes and consequently usually prefer to grow in half-shaded conditions (conditions provided in nature by trees). Some species tolerate sites totally exposed to solar radiation (H. undatus, H. costaricensis and H. purpusii, for example), however, gas exchange and growth or flowering are often inhibited (Nerd et al., 2002; Andrade et al., 2006) and very hot sun and insufficient water may lead to burning of the stems. In the Neveg Desert in Israel, the most favorable conditions for growth and fruit production are found to be 30% shade for H. polyrhizus (Raveh et al., 1996), while in the French West Indies (Guadeloupe and Saint-Martin), cultivation of H. trigonus is only possible with about 50% shade (Le Bellec et al., 2006). H. undatus tolerates prolonged drought, up to six weeks, without any effect on growth (Nobel, 2006). In Mexico, the rainy season provides optimal conditions for photosynthesis in H. undatus, due to low air temperature and, small deficit of vapor pressure during the night (Andrade et al., 2006) but excess water systematically results in the abscission of flowers and young fruits (Le Bellec et al., 2006). Hylocereus species can adapt to different types of welldrained soil (Bárcenas, 1994). 12.3.3 Morphology and reproductive biology of Hylocereus Few studies have been published on the floral biology of H. undatus and H. costaricensis, the two most widely cultivated Hylocereus species in the world. Some researchers are interested in them, in some cases to study the cultivation potential of this new fruit (Weiss et al., 1994), and in other cases to study the floral biology of this species that is endemic to Costa Rica and Mexico (Castillo et al.,

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2003). The flowers of Hylocereus appear under the areoles; they are large (more or less 30 cm), in the shape of a funnel, and nocturnal. The ovary is located at the base of a long tube carrying the foliaceous scales to the exterior and there are numerous stamens on a slender anther stalk. The unusually large, tubular style is 20 cm in length and 0.5 cm in diameter; the stigmas have 24 slender lobes, and are creamy green in color. Floral growth does not depend on water availability, but on day length; in Vietnam, floral induction is often triggered using artificial light to increase day length. On Reunion Island, it has been demonstrated that the number of flowers obtained using artificial light at night is proportional to the distance between the receiving point and the light source. The floral buds can remain in the latent stage for many weeks (Le Bellec et al., 2006), and the beginning of flowering generally occurs after the rainy season (Le Bellec et al., 2006). In the southern hemisphere, H. undatus and H. costaricensis flower from November to April, and in the northern hemisphere from May to October (Weiss et al., 1994; Le Bellec, 2004). Flowering episodes are cyclic and spread out over the whole period and the number of flowering episodes or flushes depends on the species: for example, seven to eight for H. costaricensis and five to six for H. undatus. There is a period of three to four weeks between flowering flushes (Le Bellec, 2004), which makes it possible to see floral buds, flowers, young fruits and mature fruits on the same plant at the same time. The periods between the appearance of floral buds (lifting of the areole) and flowering (stage 1), and between flower anthesis and fruit harvest (stage 2) are very short: around 15 to 20 days for the first stage and 30 days for the second stage. In their native countries, pollination of flowers occurs during the night by nectar-feeding bats such as Leptonycteris curasoae and Choeronycteris mexicana (Herrera and Martinez Del Rio, 1998; Valiente-Banuet et al., 2007) or by a species of butterfly belonging to the Sphingideae family, of the genus Maduca. During the day bees (Apis melifera) pollinate flowers (Le Bellec, 2004; Valiente-Banuet et al., 2007). There seems to be no major problems connected with fruit yields in the main producing countries in Latin America and Asia (Valiente-Banuet et al., 2007). Dehiscence takes place a few hours before the complete opening of the flower. Pollen is very abundant, heavy and not powdery. Flowers open at between 20:00 and 20:30; the stigma dominates the stamens (the position of the stigma at this stage encourages allogamy). Flowers bloom only for a day and then close (whether fertilized or not) in the morning of the day after anthesis. The following day, petals become soft and then slowly dry. The lower part of a non-fertilized flower becomes yellowish and the whole flower falls off four to six days later, while the lower part of a fertilized flower remains greenish and increases enormously in volume, indicating that the fruit has set. In some countries (Israel, South Africa, Madagascar, Reunion Island and French West Indies), natural production of fruits from clones introduced from H. undatus and H. costaricensis is practically non-existent (Le Bellec et al., 2006). The autoincompatibility (Weiss et al., 1994) of the clones of these species and the absence of efficient pollinators – interspecific crossing is possible – appear to be responsible for this lack of productivity. Honeybees are very attracted to the pollen of these flowers and the repeated visits of these insects can contribute to pollination (Weiss

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et al., 1994). However, the quality of the fruits resulting from free pollination is generally lower than that of those obtained by manual cross-pollination (Le Bellec, 2004). The origin of the pollen can also influence the time lapse between pollination and harvest of the fruit (known as the phenomena of metaxenia, this was previously only observed on H. polyrhizus) (Mizrahi et al., 2004).

12.4

Cropping system

Pitahaya has only been cultivated for a short time and the first published references to serious cultivation practices date back only to around 15 years ago (Le Bellec et al., 2006). Little agronomic knowledge has been acquired from the traditional cultivation of these species in tropical America, or this knowledge has perhaps not been published. Traditional methods of cultivation have changed considerably in new production areas, as they have been adapted and improved to overcome the problems encountered there (Weiss et al., 1994). Two major pitahaya production systems are considered: the undergrowth cropping system with a well-established ecology (of the forest type, see Plate XXIII in the colour section), and the intensive system where optimum conditions for pitahaya production (shade, feeding, and irrigation) are created and managed. The undergrowth cropping system can only be effective in the natural ecological area of pitahaya. It is appropriate for plantation projects emphasizing natural production (biological production, low input, production with labels, etc.). The intensive system, on the other hand, makes it possible to enlarge the pitahaya production zone. It is particularly appropriate for projects where potential extension surfaces are limited and/or the high cost of the workforce is a limiting factor. Each system carries advantages and disadvantages. The farming of pitahaya under a natural vegetable cover that was not established for shading purposes for this same pitahaya is practiced in many areas of production (Rondón, 1998). It is probably the most used system since it is the cheapest one. This undergrowth pitahaya production method is referred to as the ‘traditional’ method, which generally provides conditions that are favorable to pitahaya production: shade, organic matter resulting from the decomposition of the leaves and branches of the vegetable cover, hygrometry, etc. However, these conditions can vary notably according to the season and undergrowth type (Andrade et al., 2006). For these reasons, regular upkeep is essential in these pitahaya plantations in order to maintain optimum growing conditions. To improve production with this method, it is possible to recreate this environment by planting tutors specifically for this culture (De Dios and Castillo Martinez, 2000). This production system allows a better control of the shade through the choice of an adapted tutor as the shade is not always adequate or at least not easily controlled. The need for water is also not always provided for. The intensive production system of the pitahaya – including artificial shade, dead tutors and an irrigation system – make it possible to meet the exact requirements of the pitahaya production. Cropping system intermediaries can also be designed. For example, pitahaya can be cultivated on dead tutors between hedges, with the trees providing

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the necessary shade. If these cropping systems are different, the specific techniques of production will not change. Only investment, labor mobilization and quantities of inputs will be different from one system to another.

12.5

Cultivation techniques

12.5.1 Multiplication and planting density Hylocereus can be multiplied naturally and very easily by cutting off the stem as soon as it touches the ground. Its sequential stem segments can develop adventitious roots, so each rooted stem segment can act as an individual unit for water uptake (Nobel, 2006). The sowing of seeds and the in vitro multiplication of young shoots of mature plants are also possible (Yassen, 2002). However, in agriculture, multiplication by cuttings is preferable, as it allows reliable reproduction of the variety. In addition, the fruiting stage is reached more rapidly with cuttings, less than one year after planting, as opposed to three years for plants grown from seed. Finally, the robustness of these species enables cuttings to be taken directly in the field; provided cuttings are at least 50 to 70 cm in length and are regularly watered in order to ensure satisfactory rooting. Given these conditions and the plant’s characteristics, around 90% of the cuttings will grow (Le Bellec et al., 2006). The distance between plants depends on the type of support used. With an artificial vertical support (see Fig. 12.3), a 2–3 m distance between planting lines is required (between 2000 and 3750 cuttings.ha−1), at a rate of three cuttings per support. With horizontal or inclined supports, the density can be

Fig. 12.3

Plant and flowers of Hylocereus costaricensis (© F. Le Bellec).

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much higher since the cuttings are planted every 50–75 cm around the production table (6500 cuttings.ha−1) or along the inclined support (6500 cuttings.ha−1) (Le Bellec et al., 2006). The height of these different types of support should be between 1.40 and 1.60 m for vertical supports and between 1 and 1.20 m for horizontal and inclined supports to facilitate management of the crop. 12.5.2 Cultivation practices Pitahaya are semi-epiphytic plants, which crawl, climb and attach naturally to any natural or artificial support they meet (trees, wood or cement posts, stone walls, etc.) thanks to their aerial roots. Growing them flat on the ground is not recommended, first because it makes cultivation more difficult (pollination, harvest, etc.), and secondly because contact with the ground causes damage to the vines. Pitahaya are thus best grown on living or dead supports (De Dios and Castillo Martinez, 2000). Many different types of support are used, but we focus on vertical supports made of wood (or cement and iron posts) and on horizontal and inclined supports (Le Bellec et al., 2006). Plant growth is rapid and continuous, though possibly with a vegetative rest period when the climatic conditions are unfavorable (such as drought and very low temperatures). When vertical and horizontal supports are used, pruning is important and the stems should be selected in such a way as to force the plant to climb over the entire support. All lateral growth and parts of the plant facing the ground should be removed, while the main stems and branch stems are kept, except those that touch the ground. Major pruning is carried out the first year after planting. Whatever the support used, the stem must be attached to it with a clip. The aim of maintenance pruning is to limit bunch growth and this should be carried out as early as the second year after planting. In practice, the extent of pruning depends on the type of support and its strength. For example, a three-year-old plant weighs around 70 kg (Le Bellec et al. 2006). Even if this weight is not in itself a problem for the different types of support, bunches may not be able to withstand violent winds. Pruning consists of removing all the damaged stems from the plant in addition to those that are entangled with one another. The postharvest pruning encourages the growth of new young shoots that will bear flowers the following year. 12.5.3 Nutrition and irrigation In natural conditions, the pitahaya feeds exclusively on the organic matter that is contained in the superficial layers of the soil. In order to create ideal conditions of production, it is important to complete this natural nutrition. Yields vary as a function of the nutritive elements supplied. The pitahaya’s root system is superficial and can rapidly assimilate even the smallest quantity of nutrients. Mineral and organic nutrition is particularly advantageous and, when combined, their effect is even more beneficial (López and Guido, 1998; Le Bellec et al., 2006). Even if pitahaya can survive with very low rainfall – many months of drought – when good quality fruits are required, a regular water supply is needed. Regular irrigation is

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important, because it enables the plant to build sufficient reserves not only to flower at the most favorable time, but also to ensure the development of the fruits. To ensure good fruit production, irrigation is often necessary, and local microirrigation is particularly recommended. In addition to the efficiency of the water supplied by this system, micro-irrigation avoids uneven and excess watering that can result in flowers and young fruits falling off the vines. 12.5.4 Weed management Weed management is an important point of the pitahaya production; the pitahaya’s root system is superficial and is particularly sensitive to competition for water. Orchards are traditionally planted on sloping grounds or in the forest; this prevents the development of weeds. Then, the use of herbicides regularly sprayed on the whole farm is a common practice. Consequently, such a practice involves some impact on the environment and the production profit (for herbicides and labor costs). Introduction of cover crops on these orchards may be an interesting alternative. A vegetative cover plant established on the inter-row can be very advantageous: it allows near total control of erosion in the event of strong rains, ensures water conservation, restores soil fertility thanks to its biological reactivation and makes it possible to limit, and even control, the proliferation of adventitious. This weed management can be supplemented by a mulching around pitahaya. 12.5.5 Pollination The lack of genetic diversity and/or the absence of pollinating agents in certain production areas means that manual cross-pollination is needed to ensure fruit setting and development (Weiss et al., 1994; Catillo et al., 2003). Manual pollination (see Fig. 12.4) is simple and this operation is facilitated by the floral characteristics of Hylocereus, as the different floral parts are very large. Finally, manual pollination may be carried out from before anthesis of the flower from 4:30 p.m. until 11:00 a.m. the next day. These manual pollinations are worth undertaking and the fruits obtained are of excellent quality (Le Bellec, 2004). Pollination is accomplished by opening the flower by pinching the bulging part. This reveals the stigmata, which are then covered with pollen with a brush. Alternatively, the anthers can be directly deposited (with minimal pressure) on the stigmata with the fingers. The pollen can be removed from a flower of a different clone (or from another species) and stored in a box until needed. The pollen removed from two flowers will be enough for around 100 pollinations with a brush. It can be stored for 3 to 9 months at −18 to −196 °C without risk of damage. Fruits obtained after pollination using pollen stored at 4 °C for 3 to 9 months are usually very small (Metz et al., 2000). The activity of bees (Apis mellifera) can make manual pollination difficult, but it must nevertheless be accomplished (Le Bellec, 2004). Bees can be extremely efficient and, after only a few hours of activity, they will have harvested all the pollen. The pollen must thus be collected before the bees arrive and manual pollination carried out the next morning as soon as the bees have left the plantation.

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Fig. 12.4

Manual pollination of Hylocereus spp. (© F. Le Bellec).

12.5.6 Harvesting Fruits from Hylocereus species are non-climacteric and have a low respiration rate when mature and after being picked (ranging between 50 and 120 mg CO2 kg−1. h−1) (Hoa et al., 2006; Nerd et al., 1999; To et al., 2002), therefore fruits should be harvested when they have attained full maturity and development is complete. Up to now the only practical harvest indexes have been the color of the epidermis and fruit firmness (To et al., 2002) which are usually assessed subjectively by fruitpickers. For both Hylocereus species (H. undatus and H. polyrhizus) it has been shown that when the color of the epidermis turns fully red, the size, fruit weight, pulp content, total soluble solids, pulp betacyanins and flavor rating reach maximum values while firmness, mucilage content, starch and total titrable acidity are at a minimum (Nerd et al., 1999). For example, in previous studies, firmness reduced rapidly from values of up to 12 kg.cm−2 at 16–20 days after anthesis to 1.2 ± 0.5 kg cm−2 at the stage when fruit epidermis is fully red (Nerd et al., 1999; To et al., 2002). This firmness value remains high and decreases only slightly during storage. Therefore, the practice of picking fruits earlier to let them better withstand transport is counterproductive as they will never develop full flavor or proper texture. In Vietnam and Mexico, this optimal maturity stage is reached within 28–31 days after anthesis for Hylocereus undatus (To et al., 2002; Yah et al., 2008), while in Israel, fruits from both Hylocereus undatus and polyrhizus grown under

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greenhouse conditions reached optimum maturity between 33–37 days after anthesis (Nerd et al., 1999). Yields vary between 5 and 30 t.ha−1, being closely related to the density of planting and practice, type of pollination, etc.

12.6

Pests and diseases

The development of the culture of pitahaya in recent years has been accompanied by the appearance of some diseases, such as anthracnose caused by Colletotrichum gloeosporioides (Palmateer et al., 2007), basal rot caused by Fusarium oxysporum (Wright et al., 2007), stems necrotic lesions caused by Curcularia lunata (Masratul Hawa et al., 2009), stem spots caused by Botryosphaeria dothidea (ValenciaBotin et al., 2003). Different viral (Cactus virus X) and bacterial (Xanthomonas sp. and Erwinia sp.) diseases are also reported in the literature and can have major consequences (Liou et al., 2004). Several factors influence the development of these diseases: rainfall, badly decomposed compost, too humid or too dry soil, successive periods of continuous rain and dryness involving asphyxiates and lack of water. On the other hand, the eradication of these diseases seems unlikely, only preventive and prophylactic measures seem suitable. The sanitary quality of plant material is dominant and determines the life of the plantation. Few pests have been recorded on Hylocereus. Ants belonging to the genera Atta and Solenopsis (Le Bellec et al., 2006) can cause major damage to the plants as well as to the flowers and fruits (see Fig. 12.5). Cotinus mutabilis perforates the stem and Leptoglossus zonatus sucks the sap, leaving stains and some deformation. Different species of aphids and scales have also been observed on fruits and flowers. Rats and

Fig. 12.5 Ant damage on fruit (© F. Le Bellec).

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birds can cause serious damage, mainly to flowers and fruits, but also to ripe fruits. The marketing of fruit may be affected by various diseases as fruit rot caused by Bipolaris cactivora (Taba et al., 2007). In some regions, pitahaya fruits are hosts of fruit fly species (Bactrocera spp.), and thus export to many markets require a disinfestation treatment (Hoa et al., 2006). Hot air treatments (46.5 °C for 20 min) (Hoa et al., 2006) and irradiation with X-rays can be successfully applied to ensure a stable visual and compositional quality during storage (Wall and Khan, 2008).

12.7

Quality components and indices

The edible part of pitahaya fruit corresponds to the mesocarp which yields a viscous juice containing many small seeds. The main physico-chemical properties of pitahaya juice (without seeds) are reported in Table 12.2. Juice contains approximately 12 ± 2% dry matter, mainly composed of reducing sugars, glucose and fructose (sucrose was only detected in traces). The amount of reducing sugars ranges from 50 to 130 g l−1 depending on varieties and cultivars (see Table 12.2). In mature fruit, a gradual increase of total soluble solids (TSS) concentration is Table 12.2

Main physico-chemical composition of Hylocereus fruit pulp

Characteristics pH-valuea Dry matter Density (20 °C) Total titratable acidsa,b Malic acid Citric acid Total soluble solidsa Protein content Lipid Glucose

Unit % g.cm−3 g.l−1 g.l−1 g.l−1 °Brix g.l−1 g.l−1

Fructose Minerals Pectin L-Ascorbic acid Dehydroascorbic acid Total vitamin C Betacyanin

g.l−1 g.l−1 mg.100 g−1 g.100 ml−1 g.100 ml−1 g.100 ml−1 mg.l−1

Total dietary fiber Total phenolics

g.100 gl−1 μM GACb equ.g−1

Hylocereus spp. 4.3–4.7 (Stintzing et al., 2003) 12 ± 1 1.04 ± 0.01 2.4 (Vaillant et al., 2005) to 3.4 (Stintzing et al., 2003) 6.2–8.2 (Esquivel et al., 2007a) 0.95–1.2 (Esquivel et al., 2007a) 7.1–10.7 1.2–1.25 1.17–1.43 30–103 (Esquivel et al., 2007a; Stintzing et al., 2003) 19–29 (Esquivel et al., 2007a) 65–136 (Esquivel et al., 2007a) 1.6–3.5 (Esquivel et al., 2007a) 1.1–3.6 (Esquivel et al., 2007a) 3.2–5.8 (Esquivel et al., 2007a) 530–717a (Esquivel et al., 2007c; Stintzing et al., 2003; Vaillant et al., 2005) 3.2 ± 0.1 (Mahattanatawee et al., 2006) 5.6–7.4 (Vaillant et al., 2005)

Notes: a Hylocereus polyrhizus. b Gallic acid equivalent.

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observed from the external section of mesocarp to the center of the fruit (Nomura et al., 2005) though TSS concentration rarely reaches more than 140 g.100 g−1 in Hylocereus species, with common values ranging generally between 8 and 13 g TSS.100 g−1 (Esquivel et al., 2007a; Vaillant et al., 2005; Yah et al., 2008). In the white flesh fruits (H. undatus), TSS content in mature fruit is slightly higher (up to 190 g TSS.100 g−1) as reported for fruits grown in temperate climate (Ming Chang and Chin Shu, 1997). Total titratable acidity is also always relatively low in pitahaya species, ranging between 2.4 and 3.4 g.L−1 according to genotype (Le Bellec et al., 2006), with malic acid as the predominant acid present in the pulp (Esquivel et al., 2007a; Nomura et al., 2005; Yah et al., 2008). Protein content varies considerably depending on methods used (from 0.3% to 1.5%) because betalain, the nitrogen-containing pigment responsible for the red color, may interfere with results. The main amino acid present in pitahaya juice appears to be proline with a remarkably high content of 1.1 to 1.6 g.L−1 in juice (Stintzing et al., 1999). Mineral content is relatively high, with potassium the most prevalent mineral in juice, and followed by sodium and magnesium (Stintzing et al., 2003). Total dietary fiber content of pitahaya fruits is reported to be 3.2 ± 0.1 g.100 g−1 (FW) (Mahattanatawee et al., 2006), a relatively high value which is probably due to mucilage, a complex polymeric substance of carbohydrate nature with a highly branched structure. Nonetheless, mucilage has been reported to be only around 0.5% of fresh pulp for mature fruit from both Hylocereus undatus and polyrhizus (Nerd et al., 1999). Pectin was reported to be only 0.27% of fresh pitahaya pulp (Mahattanatawee et al., 2006). To our knowledge, no characterization of the mucilage of Hylocereus species has been reported so far, but it can be assumed that it displays similar characteristics of other cactus species, as recently reviewed for Opuntia sp. In this case, mucilage has been characterized as a complex mixture of at least five types of polysaccharides, less than 50% of which corresponds to a pectin-like polymer. The arabinogalactan backbone is apparently predominant but other branched polysaccharides are also associated (Matsuhiro et al., 2006). Residual starch is reported even in mature fruits but concentration is below 0.5% for both H. undatus and H. polyrhizus species (Nerd et al., 1999). Hylocereus species, both white and red flesh, appear to be surprisingly poor in total ascorbic acid, ranging between 12–17 mg.100 g−1 (FW) (Nerd et al., 1999; To et al., 2002) while other cactus species, for example prickly pear, have a much higher vitamin C content which is comparable to that of citrus. Other vitamins may be present but have not been reported. Betalains is predominant in the red flesh from Hylocereus species while non-colored phenolic compounds are predominant in the white flesh of H. undatus. The red color of flesh in Hylocereus species is due to the presence of betalains, a pigment that replaces anthocyanins in fruit-bearing plants belonging to most families of caryophyllales (Stintzing et al., 2003; Strack et al., 2003). Betalains are watersoluble pigments that comprise red-purple betacyanin and yellow betaxanthins, and are an immonium conjugate of betalamic acid with cyclo-dopa and amino acids or amines, respectively. In contrast to red beet and other cactus fruits, red-purple pitahaya (H. polyrhizus) is a pure source of betacyanin as betaxanthins have not been

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detected (Strack et al., 2003), which explains the deep glowing red-purple color of the flesh. In red flesh pitahaya, the average content of total betalain ranges from 40–70 mg.100 ml−1. Structural studies on H. polyrhizus pigments reveal the presence of many betalains, but the three main betacyanins identified are betanin, phyllocactin and hylocerenin (Stintzing et al., 2006; Wybraniec et al., 2009). Betalain pigments present in red-flesh pitahaya display a red color with an absorbance peak around 536 nm (Stintzing et al., 2002). Betalains are of high commercial interest for food coloring but also for their functional properties as they present high antioxidant (Vaillant et al., 2005; Wu et al., 2006; Tesoriere et al., 2009;), anti-inflammatory (Allegra et al., 2005; Gentile et al., 2004), anti-cancer (Asmah et al., 2008), and anti-hypercholesterolemia properties (Khalili et al., 2009), reported in both chemical and cellular-based tests. Nonetheless, little is known on the real bioavailability of betacyanin (Tesoriere et al., 2004a). Betacyanins are absorbed from the digestive tract into the systemic circulation in their intact forms, yet the extent of in vivo absorption remains unknown (Frank et al., 2005) although average absorption of betalains simulated during in vitro gastro-intestinal digestion depends on the individual betalain compounds. For example, the bio-accessible fraction of betanin is only 40% in cactus fruits (O. ficus indica L. Mill.), slightly lower than for betanin from red-beet (Tesoriere et al., 2008). Pitahaya juice displays high antiradical activity; around 8–12 μmole of Trolox equivalent assessed by the ORAC method for the red flesh Hylocereus, a value very similar to beetroot (Ou et al., 2002). The white flesh Hylocereus species has a much lower ORAC value (around 3.0 ± 0.2) (Mahattanatawee et al., 2006), indicating a high participation of betacyanin compounds in the total antioxidant capacity. In most studies, a positive correlation between antioxidant capacity to total betalain content is generally observed (Esquivel et al., 2007b). Total phenolic compounds in white flesh (52.3 ± 33.6 mg GAE.100 g−1 puree) (Mahattanatawee et al., 2006). The main phenolic identified is gallic acid which is detected in various Hylocereus genotypes and tyrosine, a precursor in betalain biosynthesis (Esquivel et al., 2007b). The small granny seeds that account for about 1.3–1.5% of fruit yield 32–39% oil. The main fatty acids of pitahaya seed oil are palmitic acid (18%), oleic acid (22%), and linoleic acid (50%). The content of unsaturated fatty acids is high, around 75%, with polyunsaturated fatty acid around 50% which make the pitahaya oil comparable to flaxseed or grape seeds (Ariffin et al., 2009).

12.8

Postharvest handling factors affecting quality

As a non-climacteric crop, the quality of pitahaya fruits picked at optimum maturity tends to decrease during storage. Several factors affect fruit quality, unfortunately this knowledge is not published. Here is a review to date. 12.8.1 Temperature management Pitahaya fruits harvested close to full color stage can undergo low storage temperature up to 6 °C. However, chilling injury can occur after long period storage at 6 °C, and

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fruits present wilting and darkening of the scales and browning of the outer layer of the pulp. Fruits from Israel keep their visual acceptance and marketing quality for at least three weeks at 6 °C, two weeks at 14 °C or one week at 20 °C (Nerd et al., 1999). Throughout storage at all these temperatures, the concentration of soluble solids remained fairly constant. Fruits stored at 6 °C maintain their eating quality (flavor) for at least three weeks but deteriorated rapidly when transferred to room temperature (Nerd et al., 1999). Both varieties Hylocereus undatus and H. polyrhizus respond to storage in a similar manner (Nerd et al., 1999). During storage at 20 °C respiration rate decreases, remaining relatively low, ranging between 0.52 to 0.78 ml.CO2.kg−1.h−1, with the production rate of ethylene ranging from 0.025 to 0.091 ml.kg−1.h−1 (Nerd et al., 1999). 12.8.2 Water loss Due to scales, important thickness of peel and high mucilage content in flesh, fruit preserve high water content during storage even though water loss increases at higher storage temperature. After one week of storage at 20 °C, water loss reach only 4.2% and 3 weeks of storage at 6 °C water loss is generally reported below 6% (Nerd et al., 1999). Both species H. undatus and H. polyrhizus respond in a similar manner. 12.8.3 Atmosphere Only modified atmosphere packaging (MAP) was assessed to extend shelf life of pitahaya fruits. The shelf life of pitahaya has been extended in this case up to 35 days when stored at 10 °C, using polyethylene bags with average oxygen transmission rates of 4 l.m2.h−1 (To et al., 2002).

12.9

Processing

Pitahaya fruits can be marketed as ready-to-eat (fresh-cut) products after being peeled and/or sliced and packed in microperforated polyethylene bags. At these conditions, quality is maintained for about two weeks at either 4 or 8 °C, though an additional treatment should be implemented to prevent slices from sticking together (Goldman et al., 2005). Pure pitahaya juice is marketed in some countries and even exported. Fruits are washed, halved, and manually pulped, generally using a spoon. In Nicaragua, the pitahaya pulp obtained (with seeds) is then frozen at −20 °C, stored and directly exported to ethnic markets in the United States (Vaillant et al., 2005). Pulp can be also sieved on appropriate screens (0.5 to 1.0 mm) using a pulper with soft paddle or brushes to separate the juice from particulate matter, including seeds. However, the highly gelatinous mucilage which envelops every seed is difficult to remove by simple sieving without significantly decreasing juice yield (Esquivel et al., 2007a; Schweiggert et al., 2009). The same occurs when complete separation of mesocarp fibbers and seeds is implemented through centrifugation (Mosshammer et al., 2005). Thus, the

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compromise between juice yield and quality dictates the juicing and subsequent steps. An enzyme-assisted process for the liquefaction of pitahaya pulp can be added to degrade mucilage and make easier separation of seeds. Partial degradation of mucilage can be achieved with pulp maceration at 40 °C for two hours with very high concentration of previously selected enzymes (2000 ppm) (Herbach et al., 2007) or at 8 °C for three days with 1% ascorbic acid and 1000 ppm enzyme preparation (Schweiggert et al., 2009). The last process allows for the decrease of juice viscosity by 50%, enabling overall juice yields of 48–60% and 80% betalain recovery (Schweiggert et al., 2009), compared to 25–39% overall juice yields when no enzyme treatment is implemented. However, when compared to other fruit, the concentration of enzyme needed is extremely high, and even though the cost of enzyme can be offset by an increase of juice yields, additional research efforts are needed to develop cheaper alternatives. Traditionally, reduction of viscosity is achieved by adding ½ to ¼ (v/v) of water, sieving the slurry on cotton or synthetic cloth for the removal of seeds, and adding sugar and citric acid (TSS = 15 g.100ml−1 and pH = 3.5). The beverage is then pasteurized in glass bottles (Campos-Hugueny et al., 1986). To increase yield substantially, crushing of the whole fruit (with peel) has been also tested, not for Hylocereus species but for cactus fruits possessing similar characteristics. Cactus peel can be palatable and the mash obtained pressed using a cone screw expresser or paddle pulper fitted with appropriate screens (Mosshammer et al., 2006). An enzymatic maceration step can be implemented prior to pressing in order to increase yields, then, vacuum concentration, freezedrying or spray drying can be implemented to yield fruit juice extracts with good overall pigment retention (71–83%). Additionally, microfiltration, a membrane process, was also tested to stabilize at ambient temperature the juice but flux density was very low (825 g (vp: 300 g).

20.8.2

Control of ripening and senescence

Modified atmosphere (MA) Modified atmosphere storage has been used to extend the storage life of many perishable crops including sugar apple and atemoya. However, storing fruit in an improper atmosphere may result in some disorders. Some studies on MA storage of sugar apple and cherimoya are described below. Coating ‘Nang’ sugar apple with 0.5 and 1.0% chitosan or individually wrapping the fruit with linear low density polyethylene (LLDPE) did not delay fruit softening when the fruit was stored at 13 °C and 95% RH. Modified atmosphere packaging (MAP) with 6 μM and 15 μM PE bags, though, reduced weight loss and maintained skin and pulp colour. Fruit kept in 6 μM PE bags had a storage life of at least 18 days whereas after day 12, fruit kept in 15 μM PE bags showed skin darkening (Fig. 20.8(c, d)) after removal from the bags due to the high CO2 inside (Chunprasert et al., 2006). Fully mature and freshly harvested sugar apple (Annona squamosa L.) stored in fibreboard boxes had a shelf life of four days at ambient (27 ± 2 °C) and eight days in cool storage conditions (15 ± 2 °C). The post-harvest combination of coating with 6% waxol + 0.1% carbendazim and forced-air precooling (at 10 °C) extended shelf life up to 14 days under cool storage (Kamble and Chavan, 2005). There were reports of the synergistic effects of ethylene absorbents and MAP when used in combination to extend storage life. Sugar apple placed in PE bags containing KMnO4 had a storage life of nine days while untreated fruit could be stored for five days (Babu et al., 1990). Sugar apple packed in 0.1 mm thick polyvinylchloride (PVC) film plus KMnO4 absorbent and stored at 16 °C with 90–100% RH delayed fruit ripening (Chaves et al., 2007). MAP by individual packing in PVC film and placing the fruit in polyester trays wrapped in PVC film did not influence the skin colour of ‘Gefner’ atemoya, but it preserved pulp brightness and reduced weight loss compared to non-packed fruit. Silva et al. (2009) found that MAP and storage at low temperature effectively preserved atemoya and maintained the fruit’s appearance after 15 days of storage. Atemoya cv. ‘PR3’ fruit individually sealed in copolymer (PD-955) and

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low-density polyethylene (LDPE) bags were stored for 21 days at 15 °C or 25 °C and then were unwrapped and maintained at 25 °C for ripening. Weight loss in the packaged atemoyas was lower than in the control (non-wrapped fruit). Fruit sealed in LDPE did not ripen, probably due to development of an injurious atmosphere inside the package. Atemoyas packaged in PD-955 film stored at 15 °C had a shelf life of 17 days compared to the 13 days of the control fruit (Yamashita et al., 2002). Negative physical and chemical changes and deterioration in eating quality was delayed in ‘Pet Pakchong’ fruit wrapped with PVC film and stored at 14 °C. However, the PVC film wrapping caused abnormal ripening. Unwrapped fruit stored at 14 °C had the longest shelf life (12 days) while fruit stored at room temperature had the shortest shelf life (three days) (Oumsomniang, 2005). 1-Methylcyclopropene (1-MCP) 1-MCP is used for extension of postharvest life in many types of fresh produce, in particular climacteric or ethylene-sensitive produce. It inhibits ethylene responses by competitively binding to ethylene receptor in plant cells. 1-MCP is not only practical as vapour fumigation, but it can also be used in small volumes, making the treatment safe from the point of view of human health. It is mostly used as a pretreatment before long periods of storage. Sugar apples treated with 810 ppb 1-MCP for 12 hours at 25 °C and then stored at 25 °C for four days were firmer than the control. Both sugar apples treated with 1-MCP at 30 or 90 ppb and the control fruit ripened faster than fruit treated with 1-MCP at higher concentrations (Benassi et al., 2003). ‘African Pride’ atemoya fruit were fumigated with 25 ppb 1-MCP for 14 hours at 20 °C, treated with 100 ppb ethylene for 24 hours, then ripened at 20 °C. Fruit treated with ethylene alone generally ripened 50% faster than untreated fruit, while 1-MCP treatment alone increased the number of days to ripening by 3.4 (58%). Applying 1-MCP to the fruit prior to ethylene prevented accelerated ripening, so that the ripening time was similar to fruit treated with 1-MCP alone. However, 1-MCP treatment was associated with slightly higher severity of external blemishes in atemoya and slightly higher rotting severity in atemoya, compared to non-treated control (Hofman et al., 2001). Thus, additional precautions may be necessary to reduce disease severity associated with 1-MCP treatment. ‘Fai’, ‘Nang’ sugar apples and ‘Pet Pakchong’ atemoya were fumigated with 500 ppb 1-MCP to study fruit ripening behaviour (Noichinda et al., 2009a). Climacteric peaks at 25 °C were dramatically reduced in 1-MCP treated ‘Nang’ and ‘Pet Pakchong’ (Fig. 20.11(a)) while ethylene production peaks were slightly decreased and delayed following all 1-MCP treatments (Fig. 20.11(b)). The ripening and softening of 1-MCP treated fruit was postponed for 2–3 days (Fig. 20.12). Calcium carbide (CaC2) After harvest most sugar apples and atemoyas in Thailand are traditionally allowed to ripen naturally during transport to the consumer, usually for several days at ambient temperature. The traditional way to hasten fruit ripening is the application of CaC2 which releases acetylene (C2H2) gas to induce fruit ripening.

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Fig. 20.11 Respiration (a) and ethylene production (b) rates of non-treated (solid lines) and 500 ppb 1-MCP-treated fruit (dashed lines) of ‘Nang’ ({), ‘Fai’ (Δ), and ‘Pet Pakchong’ (×) at 25 °C.

Using CaC2 to hasten ripening effectively reduced fruit cracking and fruit weight loss during ripening in ‘African Pride’, but did not affect soluble solids, SS/TA, and vitamin C contents (Kosiyachinda and Kasiolarn, 1989; Kasiolarn, 1991). Flavonoid levels of CaC2-treated sugar apple fruits in ‘Fai’ and ‘Nang’ varieties were slightly lower than those of naturally ripened ones. As far as antioxidant activity abilities were concerned, ferrous ion chelating in both ripened groups was quite low (0.01–0.02%), whereas DPPH free radical scavenging ability, in contrast, was high at 83–92% (Noichinda et al., 2010b). Chemicals Some chemicals, such as plant growth regulators, have been applied to improve postharvest quality of sugar apples. Salicylic acid (SA) is an endogenous hormone that mediates in plant defence against pathogens. It has been reported to reduce decay and extend storage life of various fruits. Treating sugar apple with SA increased activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), decreased lipoxygenase (LOX) activity and correspondingly lowered malondialdehyde (MDA) contents in treated fruit, compared to the control. SS, total soluble sugars, softness and decay rate were significantly lowered in treated fruit, and fruit ripening was achieved after ten days of storage (Mo et al., 2008). SA has positive effects in maintaining membrane integrity and in delaying fruit ripening process.

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Fig. 20.12 Fruit firmness of non-treated (solid lines) and 500 ppb 1-MCP-treated fruit (dashed lines) of ‘Nang’ ({), ‘Fai’ (Δ), and ‘Pet Pakchong’ (×) at 25 °C.

Furthermore, several regulating substances were used to investigate their role in the respiratory climacteric and ripening of sugar apple fruit. Dipping sugar apple fruit in a solution of indole acetic acid (IAA) at concentrations between 10−4 and 10−2 M accelerated ripening (Broughton and Guat, 1979). 1-Aminocyclopropene1-carboxylic acid (ACC) and IAA enhanced the softening and electrolyte leakage of treated-fruit. Respiration of IAA-treated fruit was enhanced. In contrast, aminoethoxyvinylglycine (AVG) and 2, 4-dinitrophenol (DNP) delayed softening. Cycloheximide (CHI), which inhibits de novo synthesis of the cell proteins, caused the fruit to remain harder than the untreated fruit (Tsay and Hong, 1988). 20.8.3 Recommended storage and shipping conditions Mature sugar apple and atemoya fruits can be stored at temperatures above 13 °C to facilitate shipment to distant markets. Lower temperatures cause chilling injury

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with subsequent shrivelling and abnormal ripening (Kasiolarn, 1991; Campbell and Phillips, 1994). Pre-cooling of sugar apples by room- or forced-air cooling at 10 to 13 °C and maintaining controlled atmosphere (CA) conditions at 3–5% O2 + 5–10% CO2 can result in a storage life of four weeks (Kader, 2001; Cantwell, 2002). On the other hand, others have recommended storing sugar apple at temperatures between 15 and 20 °C (Broughton and Guat, 1979; Vishnu Prasanna et al., 2000) and with low O2 and ethylene tensions coupled with 10% CO2 and a relative humidity of 85%–90% in the storage atmosphere (Broughton and Guat, 1979).

20.9

Processing

20.9.1 Fresh-cut processing As atemoya are bigger than sugar apples and contain fewer seeds, they can be used to make fresh-cut products, before they become too soft. However, quick flesh browning is a major concern. Fresh atemoya pulp treated with 0.4–0.5% ascorbic acid and stored in MAP consisting of a 65 μM LLDPE/nylon/ LLDPE five-layer co-extruded bag at 0 °C for four weeks retained the desired creamy colour during storage and after exposure to ambient conditions for three hours. Sensory and microbiological properties of the ascorbic acid-treated atemoya pulp were acceptable throughout the storage period of four weeks (Gamage et al., 1997). 20.9.2 Other processing practices In Thailand, sugar apples are rarely processed. They are mostly consumed fresh as a dessert and are considered to be of poor quality and of little commercial importance. However, the pulp is sweet and has an excellent flavour that can be processed into many products including ice cream, sweet desserts, nectar, jelly, jam, conserves, sherbet, syrup, tarts, juice and fermented drinks (wine/liquors) (Ojha et al., 2005; Wanichkul, 2009b). Heat is commonly used to preserve processed products, but care should be taken with respect to its effect on quality, especially flavour. The flavour spectrums of sweet and flavoured pulp from mature ripe fruit of sugar apple heated to 55 °C (critical temperature) and 85 °C (pasteurization temperature) for 20 minutes each, and spray dried with skim and whole milk powders and stored for 12 months, did not differ from those in the fresh pulp. However, heating fresh pulp has the tendency to increase flavour production. Both heat treatments significantly increased the quantities of aroma compounds in the isoprenoid group such as α-pinene, β-pinene, linalool, spathulenol, cineole, limonene, α-copaene, α-farnecene and δ-cadenene, while germacrene, α-cubebene, caryophyllene were found in the 55 °C treatment and aromadendrene, ε-cadenene were found in the 85 °C heated pulp (Shashirekha et al., 2008). Freezing is an alternative method to preserve the quality of fresh produce for long storage durations. Individually quick frozen (IQF) vacuum packaged and

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non-vacuum packaged sugar apples were stored at −18 °C for 12 months. Little discolouration was observed in vacuum packaged fruit, whereas serious discolouration was found in the non-vacuum packaged control. The main phenolic compounds, catechin, chlorogenic acid, eugenol and gallic acid, were higher in the pulp packaged under a vacuum. The discolouration of the pericarp of frozen sugar apple is thought to be O2-involved browning (Wu et al., 1997).

20.10

Conclusions

Sugar apples (Annona squamosa Linn.) and the hybrid atemoyas (A. cherimola Mill. × A. squamosa Linn.) are tropical aggregate fruits with attractive appearance due to their protruding areoles. Sugar apples and atemoya contain high levels of sugars and vitamin C. While fruit softening and fruitlet separation during ripening are the main concern for some sugar apple varieties, fruit cracking and skin blackening are concerns for atemoyas. Fruit softening behaviour during ripening separates sugar apples into two groups: fruit carpel splitting and fruit carpel gelling. Enzymes associated with cell wall degradation need to be investigated to understand their participation in the softening processes. Storage temperatures above 13 °C are ideal and lower temperatures cause chilling injury. Controlled and modified atmosphere storage could effectively extend the storage life, with the optimum atmosphere being 3–5% O2 + 5–10% CO2. 1-MCP fumigation is a practical and promising technique to maintain quality of sugar apple. Sugar apple and atemoya plants can be programmed to produce fruit throughout the year by branch pruning techniques. However, due to their short postharvest shelf life and probably also due to quality problems such as fruit splitting, pulpy flesh and skin blackening and the fact that they contain multiple seeds due to their biological morphology, sugar apples are only a minor fresh commodity in international markets. Research is on-going in the areas listed above and, although there have been some promising results, further research is still needed. Fundamental research using molecular biology to understand and to control ripening is needed. Proper breeding programmes are required to satisfy consumer preferences. New cultivars are needed, with a lower calorie content but with high antioxidant levels. Qualities admired by consumers include a minimum number of seeds, firm fruit, lack of woodiness, consistent flavour, improved external shape and appearance, and lack of skin blackening. Breeding programmes and other research efforts should aim to produce fruit with these properties.

20.11 Acknowledgements We most appreciate Assoc. Prof. Dr Kavit Wanichkul and Mr Ruangsak Komkhuntod, official staff from Kasetsart University, Thailand, for providing us with both informative data and materials of sugar apple and atemoya.

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21 Tamarillo (Solanum betaceum (Cav.)) W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain, A. East, Massey University, New Zealand and A. Woolf, The New Zealand Institute for Plant & Food Research Limited, New Zealand

Abstract: The tamarillo is a subtropical non-climacteric fruit that produces fruit throughout the year, with fruit production peaking in late summer or autumn. The fruit has an attractive deep red skin and flesh, and a distinctive somewhat acidic flavour. Tamarillos are optimally stored at 3 to 4.5 °C, and 90–95% relative humidity. Lower temperatures will increase the risk of chilling injury. As the fruit mature, the colour changes from green to purple, red, amber and gold, while firmness and titratable acidity decline and the juice yield, soluble solids content (mainly sugars) and pH increase. Stem and calyx quality are important factors from a commercial marketing perspective although they do not affect flavour. Key words: Solanum betaceae, Cyphomandra, tamarillo, tree tomato, tomate de árbol, anthocyanins, stem quality.

21.1

Introduction

21.1.1 Origin, botany, morphology and structure The tamarillo (Solanum betacea, previously known as Cyphomandra betaceae) belongs to the plant family Solanaceae, genus Solanum (Bohs, 1995). The fruit are egg-shaped berries, with attractive, glossy, purple-red to golden yellow skins and orange-red to cream-yellow succulent flesh surrounding the seed locules (see Plate XXXVI in the colour section between pages 238 and 239). Other names commonly used are tree tomato, ‘tomate de palo’, and ‘tomate de árbol’. The name tamarillo was developed in New Zealand as recently as 1970 (Morton, 1987). The exact origin of tamarillo is at present unknown (Popenoe et al., 1989), but it can be found in the Andean regions of Peru, Chile, Ecuador and Bolivia (Morton, 1987) and is categorised in the same Solanaceae family as tomato, eggplant and capsicum (Sale and Pringle, 1999). The plant has spread to Central

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America and the West Indies and New Zealand (Slack, 1976). In the wild, the fruit are generally small, splotchy and yellow or pale red in colour (Popenoe et al., 1989). The large purple-red strains currently found in commercial plantings were developed by nurserymen in New Zealand around 1920, from the then existing yellow and purple strains (Sale and Pringle, 1999) that were introduced by D. Hay & Sons in 1891 (Morton, 1987). The plant is a small, fast-growing and brittle tree, with shallow roots. It grows to a height of 3–5.5 m with a single upright trunk that branches into a few lateral branches (Morton, 1987; Popenoe et al., 1989) which bear the flowers and fruit. The evergreen leaves are large (17 to 30 cm long, 12 to 19 cm wide), shiny, hairy, with prominent veins, and a pungent musky odour. The tree reaches maturity three years after planting and is commercially productive for seven to eight years (Clark and Richardson, 2002). Tamarillo has a modular growth pattern, with each module consisting of three to four leaves with a terminal inflorescence. The inflorescence has a compound structure of up to 50 pale pink or lavender flowers distributed alternately (Lewis and Considine, 1999a). The flowers have five pointed lobes, five yellow stamens and green-purple calyx (Morton, 1987) and open sequentially at two- to three-day intervals, with individual flowers closing at night and reopening each day for up to five days (Lewis and Considine, 1999a). Flowering is continual but usually peaks in late summer or autumn. Tamarillo flowers are self-pollinating but require wind or an insect pollinator to transfer the pollen. The fruit take around 21 to 26 weeks to mature from flowering and since flowering is continual, fruit are also formed year round, with a peak in late autumn and winter (April to November in New Zealand) (Sale and Pringle, 1999). Fruit do not mature simultaneously and several harvests are necessary (Morton, 1987; Popenoe et al., 1989). The fruit is egg-shaped, 4–10 cm long and 3–5 cm wide; it is pointed at both ends and has a long stalk that is left attached for marketing. The skin is smooth, thin and yellow or orange to deep red or almost purple, sometimes with dark, longitudinal stripes. The flesh has the same variation in colour as the skin, ranging from yellow to deep red, or purple. The skin is tough and has an unpleasant flavour. The fruit has a firm texture and numerous thin, nearly flat, circular, large, hard and distinctly bitter seeds in two lengthwise compartments (Morton, 1987). The pulp surrounding the seeds is soft, juicy, subacid to sweet and flavourful, whereas the outer layer of flesh is slightly firm, succulent and bland. In the outmost layers of the flesh, small, hard, irregular, ‘stones’, containing large amounts of sodium and calcium, can appear (Popenoe et al., 1989). Tamarillo is a subtropical fruit and flourishes in regions where temperatures in the growing season are between 16 and 22 °C (Popenoe et al., 1989), while frost (−2.2 °C) will kill all but the larger branches (Morton, 1987). There are no altitude limitations, as they can be found at 1100–2300 m at the equator and near sea level in New Zealand (Popenoe et al., 1989). Fertile, light, well drained soils are needed (Morton, 1987; Popenoe et al., 1989), with good drainage and irrigation, since the trees cannot tolerate drought nor standing water.

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21.1.2 Worldwide importance and economic value The tamarillo is cultivated extensively in most of South America but is mainly used for local consumption and often in a processed form; it is not promoted, resulting in lower quality fruit unsuitable for export. In Ecuador, 3000 ha produce 25 000 tonnes that are consumed within the country at a rate of approximately 1.5 kg/ capita/year (Ojeda et al., 2009). In Colombia about 120 000 tonnes of tamarillo are produced per year on 6500 ha of which the majority is locally consumed (Márquez et al., 2007), but 500 tonnes were exported in 2008 to The Netherlands, France, Canada, Germany and Spain, representing a value of circa €870 000 (Legiscomex, 2008). Infrequent reports indicate the presence of the plant in Kenya (Mwithiga et al., 2007), Uganda (Stangeland et al., 2009), Malaysia (Tee and Lim, 1991), Taiwan (Tseng et al., 2008) and Cuba (Tejeda and Cortes, 1997). Thanks to selection efforts and the development of shipping and storage techniques, tamarillo has been successfully grown in New Zealand (Janet, 2005). Commercial production is located in the north of the North Island, with about 175 growers producing 740 tonnes of fruit on 194 ha, representing a value of circa €700 000 in domestic sales and €550 000 in export sales in 2008 (Aitken and Hewett, 2008). The main export markets for tamarillo from New Zealand are the USA (mainly California), Australia, Hong Kong, Japan, Singapore, and the Pacific Islands. Tamarillo is exported fresh, packed in a cardboard box with each fruit sitting in an individual cup within a tray covered by a polyliner. 21.1.3 Cultivars and genetic variability Although named cultivars seem to exist only in New Zealand, two to four types of tamarillo are distinguished according to their skin colour: purple-red (often divided into purple and red) and yellow (often divided into amber and gold) (Popenoe et al., 1989; Sale and Pringle, 1999; Prohens and Nuez, 2000). Growers often relate the yellowish green leaf colour to the production of yellowish fruit and the purple-green foliage with the production of orangey-red fruit. In New Zealand, the red cultivar ‘Red Beau’ was the standard cultivar but it has significantly declined because of virus sensitivity, being replaced by varieties like ‘Ted’s Red’ and ‘Laird’s Large’. Other named red cultivars include: ‘Oratia’, ‘Red Delight’, ‘Kerikeri Red’, ‘Andy’s Sweet Red’, ‘Red Beauty’, ‘Red Chief’ and ‘Seccombe Red’ (Sale and Pringle, 1999). In the yellow strains, ‘Bold Gold’ is one of the most common cultivars (Sale, 2006) with other named cultivars being ‘Goldmine’, ‘Amberlea Gold’ and ‘Kaitaia Yellow’. The most serious disease affecting tamarillo in New Zealand is tamarillo mosaic potyvirus (TaMV), which results in production of blotchy, streaked unattractive fruit, limiting the production of export grade fruit. Therefore, great effort is going into the development of resistant cultivars (Cohen et al., 2000). 21.1.4 Culinary uses, nutritional value and health benefits The fruit is eaten raw or cooked and can be used as a vegetable like tomato but is also often used in desserts. The skin is always removed, being bitter.

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The red strain is preferred for fresh consumption because of its stronger, more acid flavour. Yellow fruit have a milder flavour and are preferred for canning. The nutritional characteristics (see Table 21.1) of yellow and purple-red cultivars are all within the same range, although significant differences are found between cultivars (Boyes and Strübi, 1997). The main difference between the yellow and purple-red cultivars can be found in the anthocyanin content, which is considerably higher in the purple-red cultivars (Vasco et al., 2008). Tamarillos are low in fat and carbohydrate, low in sodium, and rich in iron, potassium and

Table 21.1 Nutritional characteristics of tamarillo from New Zealand, Ecuador, Spain, Colombia and Uganda. Ranges are presented Parameter

Purple red Min

Diameter (cm) 4.6 Length (cm) 5.5 pH 3.5 Soluble solids content (°Brix) 9.4 Titratable acidity (%) 0.76 Moisture (%) 87 Proteins (%) 2.2 Fat (%) 0.08 Glucose (%) 0.454 Fructose (%) 0.615 Sucrose (%) 0.604 Citric acid (%) 0.77 Malic acid (%) 0.05 Ash (%) 0.69 0.2 Sodium (mg 100 g−1 FW) 238 Potassium (mg 100 g−1 FW) 7.3 Calcium (mg 100 g−1 FW) 14 Magnesium (mg 100 g−1 FW) 0.35 Iron (mg 100 g−1 FW) 14 Vitamin C (mg 100 g−1 FW) 1.31 Antioxidant activity FRAP (mmol 100 g−1 FW) 4.2 Antioxidant activity (μmol TROLOX g−1 FW) 81 Total phenolic content (mg GAE 100 g−1 DM) 163 Anthocyanins (mg 100 g−1 DM) 94.4 Hydroxycinnamic acids (mg 100 g−1 DM) β-carotene (mg g−1 FW) 5.1

Yellow Max

Min

7 8 3.6 13.6 1.71 92 2.2 0.6 1.4 1.412 2.5 2.7 0.53 1.26 8.9 524 26 25.4 0.9 42 1.96 10.3 187 167 96.2 5.2

3.9 5 5.6 7 3.2 3.5 9.3 12.3 1.48 4 86 88 2.4 2.5 0.05 0.72 0.5 1.7 0.7 1.6 1.125 2.979 1.02 2.5 0.07 0.32 0.7 0.82 0.06 4.96 311 440 10.4 25 16 22.5 0.22 0.6 14 33.15 2.6 81 ND 59.44 3.4

Max

6.8 125 ND 60.36 4.6

ND= not detected; where FW = fresh weight: DM = dry matter; FRAP = ferric reducing antioxidant power; GAE = gallic acid equivalents; TROLOX = 6-hydroxy-2,5,7,8-tetramethylchroman-2carboxylic acid Sources: Dawes and Callaghan (1970), Romero-Rodriguez et al. (1994), Boyes and Strübi (1997), Manzano (2005), Leterme et al. (2006), Vasco et al. (2008; 2009), Mertz et al. (2009b) and Stangeland et al. (2009).

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vitamin C (see Table 21.1), and they contribute significantly to the daily intake of vitamins A, B6 and E (Lister et al., 2005). They have a high antioxidant activity, comparable to that of mango (Stangeland et al., 2009), mainly due to the high vitamin C content but low total soluble phenolic content (< 200 mg gallic acid equivalent (GAE) 100 g−1 fresh weight (FW)), and low antiradical efficiency against the 1,1-diphenyl-2-picrylhydrazyl (DPPH•) free radical (Vasco et al., 2008). A full mineral analysis of the fruit is provided by Leterme et al. (2006) and characterisation of the combination of sugars and acids is provided by Heatherbell et al. (1975). The fruit is generally eaten by scooping the flesh from cut halves. Tamarillos can be used in any meal the same way tomatoes would be used: they are poached, fried, grilled, baked, added to stews or casseroles. They are also used to make compote, chutneys, and curries or to add taste or a decorative touch to salads or cheese platters. In Colombia, Ecuador and Sumatra, the fresh fruit are eaten less often, but they are frequently juiced or blended with water and sugar to make a fruit drink. In Ecuadorian folk medicine, the fruit, and more specifically the peel, is considered to be a cholesterol-lowering food and is used as an antimicrobial/ anti-inflammatory treatment for sore throats and inflamed gums (Vasco et al., 2009). An Argentinean community uses the boiled roots of the plant as a treatment for hepatic disorders (Hilgert, 2001).

21.2

Preharvest factors affecting fruit quality

21.2.1 Flowering and pollination In tamarillo, vegetative growth, flower production and fruit set continue over an extended period throughout the warmer months (Clark and Richardson, 2002). Flowering is continual but usually peaks in late summer or autumn, thus leading to an extended harvest period (generally three months for a given cultivar). Tamarillo flowers are self-pollinating but need wind or an insect vector to transfer the pollen. Both honey bees and bumble bees visit tamarillo flowers in New Zealand, but the effective pollination period is only three days, and pollination and fertilisation are essential for fruit development as flowers will drop prematurely if they are not pollinated. Because up to 50 flowers can be found in an inflorescence and flowers open sequentially at two- to three-day intervals, individual inflorescences have open flowers for up to 60 days, and flower buds, flowers and fruitlets can be present simultaneously in an individual inflorescence (Lewis and Considine, 1999a). Only 12% of the flowers set fruit and only 3% develop into mature fruit, and this was not improved if hand pollination was added to the natural pollination. In general, the probability of fruit set decreases with the amount of fruit that has already set in an inflorescence (Lewis and Considine, 1999b). Because of the high level of flower and fruit abscission, yield is very low (Lewis and Considine, 1999b), and a high producing orchard can yield 15 tonnes per ha, which is much lower than, for instance, apples and oranges, which can yield 70 tonnes per ha (Richardson and Patterson, 1993).

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21.2.2 Fruit growth, development and maturation Tamarillo has a double sigmoidal growth curve, with initial slow fruit growth from 20 to 45 days after anthesis (DAA), followed by an accelerated growth phase from 45 to 95 DAA, during which most of the dry matter is accumulated (Ordóñez et al., 2005). After this, growth slows down again. The fruit changes colour at about 60 DAA and soluble solids content (SSC) is maximal around 90 DAA (the red-ripe stage for red fruit), as is the reducing sugar content, with hexoses making up the main part (Ordóñez et al., 2005). Sucrose is not accumulated in tamarillo fruit. The malic acid content is low throughout maturation, whereas the citric acid content increases rapidly during the initial stage of growth, reaching a peak value around 60 DAA (Heatherbell et al., 1982). Starch accumulation is maximal (15.1 mmol kg−1) just before the fruit changes colour (55 DAA) and minimal (2.7 mmol kg−1) at fruit maturity (95 DAA) (Ordóñez et al., 2005). Interestingly, unlike tomatoes, starch accumulation is not correlated with fruit growth or SSC. The best indicator of fruit maturity for red tamarillo is the skin colour, as immature fruit are green, mature fruit are purple, and ripe fruit turn a deep red. With the exception of ‘Bold Gold’, which converts directly from green to yellow, yellow cultivars change from green to red to yellow (Sale and Pringle, 1999). Changes in colour start at the apex, with the flesh around the calyx being the last to change colour. The fruit continues to develop the red colour after harvest, with an increase in SSC and a decrease in titratable acidity (TA) (El-Zeftawi et al., 1988). The anthocyanin concentration in the flesh increases rapidly (up to 1.4 mg g−1 FW) during the early stages of fruit growth, while the anthocyanin concentration in the skin stays low (< 0.1 mg g−1 FW). This accounts for the unpleasant taste of immature tamarillo. As tamarillos mature, the anthocyanin content of the pulp substantially decreases and the content in the skin increases (Heatherbell et al., 1982). If tamarillo fruit are harvested immature, they will have a shorter shelf life, shrivel quickly during storage, and not develop the full red colour (Pratt and Reid, 1976; Sale and Pringle, 1999). Pectins decrease during fruit growth from 1% to 0.75% (Heatherbell et al., 1982). Firmness, juice content and SSC can provide useful complementary information (El-Zeftawi et al., 1988) for assessment of fruit maturity. As with many other fruits, the aroma and typical flavour are the last to develop. In total, 49 aroma and flavour components have been identified, the majority being non-terpenoid alcohols and esters and more specifically, methyl hexanoate, (E)-hex-2-enal, (Z)-hex-3-en-1-ol, eugenol, 4-allyl-2,6-dimethoxyphenol (Torrado et al., 1995), (Z)-3-hexenol, ethyl butyrate (14.8%), methyl butyrate and methyl hexanoate (Wong and Wong, 1997).

21.3

Postharvest physiology and quality

21.3.1 Respiration and ethylene production Tamarillo is a non-climacteric fruit with little respiration and ethylene production after harvest, resulting in a relatively long shelf life (Pratt and Reid, 1976; Sale

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and Pringle, 1999). The respiration rate of tamarillo (0.19–0.25 μmol CO2 kg−1s−1 at 4 °C) slowly decreases after harvest, while the ethylene production (< 0.001 nmol kg−1s−1 at 4 °C) remains low (Pongjaruvat, 2008). Both respiration rate and ethylene production increase at the onset of fruit senescence (Pratt and Reid, 1976), and during shelf life at 20 °C (Pongjaruvat, 2008). 21.3.2 Ripening, quality components and indices As the fruit ripens, its skin develops a full red (or yellow or orange) colour, firmness decreases and the stem changes in colour from green to yellow and eventually detaches. The colour development of red tamarillo fruit is commercially used to assess fruit maturity in New Zealand (Sale and Pringle, 1999). The fruit is considered to be at optimum maturity for harvest and marketing when it is purple, as the red colour will continue to develop after harvest (El-Zeftawi et al., 1988) unless the fruit is harvested when it is still too immature (Pratt and Reid, 1976). In orange tamarillos, redness (a*), yellowness (b*) and lightness (L*) of the skin all increased with ripening (Márquez et al., 2007), whereas in ripe New Zealand ‘Mulligan Red’ red tamarillos (see Fig. 21.1), a*, b*, and C* all decreased while L* remained stable (Pongjaruvat, 2008). In contrast, in Kenyan tamarillos, redness (a*) of the skin increased as yellowness (b*) and lightness (L*) decreased; and the latter correlated well with a decrease in lightness of the pulp and an increase in the SSC of the juice (Mwithiga et al., 2007). Firmness (puncture, compression) decreased as tamarillos ripened (Márquez et al., 2007; Mwithiga et al., 2007; Pongjaruvat, 2008), and firmness (puncture) could be used to predict the internal fruit quality, as its decrease corresponds to an

Fig. 21.1 Changes in colour parameters of tamarillo fruit during storage at 4 °C without shelf life (—), and with three days of shelf life at 20 °C (---) (adapted from Pongjaruvat, (2008)).

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increase in juice yield (Mwithiga et al., 2007). This decrease can probably be related to the increase of soluble pectins during maturation, while pectic acid and protopectins decrease (Heatherbell et al., 1982). The SSC of tamarillo fruit increases during ripening to 10–12 °Brix (El-Zeftawi et al., 1988; Márquez et al., 2007; Mwithiga et al., 2007), pH increases from 3.2–3.7 to 3.4–4.7 (Márquez et al., 2007; Mwithiga et al., 2007) and TA slightly declines (Manzano and Diaz, 2002; Márquez et al., 2007). These changes result in an increase in the SSC/TA ratio (Pongjaruvat, 2008) and thus a higher sensory flavour rating (El-Zeftawi et al., 1988). As the fruit ripens, the stem changes in colour from green (see Plate XXXVIIE in the colour section) to yellow (see Plate XXXVIIF in the colour section) because of accelerated water loss and chlorophyll degradation, and eventually detaches (Pongjaruvat, 2008).

21.4

Postharvest handling factors affecting quality

21.4.1 Handling and grading Because flower production and fruit set continue over an extended period, not all the fruit on a tree mature at the same time, and multiple harvests are needed. Tamarillo fruit are harvested by hand and packed with the stems attached. The healthy and intact green stems of tamarillo fruit influence consumer and marketing perception and are required to satisfy export standards (Sale and Pringle, 1999). Grading of fruit is generally done based on size, and misshapen and blemished fruit are removed. Fruit are generally packed into plastic pocket packs and placed inside polyethylene-lined single layer trays. Polyliners are essential to prevent excessive weight loss and fruit shrivelling during long-term storage, because they ensure a higher relative humidity (RH) surrounding the fruit. However, this is accompanied by a higher likelihood of fruit rots. 21.4.2 Temperature Cooling tamarillo fruit below 7 °C will slow softening, weight loss, TA reduction and colour change (Espina and Lizana, 1991; Manzano and Diaz, 2002; Pongjaruvat, 2008); however, the optimal temperature is lower, at 3 to 4.5 °C (Harman and Patterson, 1984). Temperatures below this optimal (e.g. 0–2 °C) will increase the risk of chilling injury (CI) and will cause more discolouration of the calyx and stem, while fungal decay occurs on the stem and calyx if stored above 4.5 °C (Espina and Lizana, 1991). Storage at 4 °C slows fruit metabolism, and the deterioration of the stem through a marked decrease in moisture loss and chlorophyll degradation and prevention of an increase in polyphenoloxydase activity (Pongjaruvat, 2008). The maximum storage duration will of course depend on a range of preand postharvest factors, but a storage duration of six weeks should be achieved relatively easily using optimum temperature management. Storage for up to nine weeks is possible, and the maximum generally limited by expression of

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post-storage rots, these being significantly influenced by orchard factors (Woolf and Jackman, unpublished data).

21.4.3 Relative humidity A RH between 90% and 95% is optimal for tamarillo (Harman and Patterson, 1984). Lower RH, such as when tamarillo fruit are stored in open trays (23 °C, 65% RH), will result in considerable loss of moisture (12% in 14 days) and hence a decrease in marketable weight (Márquez et al., 2007). Using polyliners in the trays and thus increasing RH will reduce weight loss to 0.3–0.5% (in 14 days) when stored at 4 °C and will retain firmness (compression) better (Pongjaruvat, 2008).

21.4.4 Ethylene Applying ethylene will accelerate fruit ripening through a stimulation of respiration, a decrease in firmness, development of red skin colour and yellow flesh colour, and an increase in the ratio of SSC to TA (Pratt and Reid, 1976; Prohens et al., 1996).

21.4.5 Modified and controlled atmosphere Little information is available regarding modified atmosphere packaging (MAP) of tamarillo. MAP (3–4 kPa O2 and 4–7 kPa CO2) delayed the development of stem yellowing, but did not improve fruit quality, and increased stem blackening and ‘bleeding’ (diffusing red pigment) in the locule (Pongjaruvat, 2008).

21.4.6 Special treatments Submersion in a citric acid solution was effective in slowing down the SSC increase and TA decrease and increasing the shelf life (30 °C and 80% RH) of fruit from six to ten days (Moreno-Álvarez et al., 2007).

21.5

Crop losses

21.5.1

Physiological disorders

Chilling injury Tamarillos are sensitive to CI at temperatures lower than 3 °C. CI symptoms include scald (brown discolouration), surface pitting, and increased susceptibility to decay (Harman and Patterson, 1984; Espina and Lizana, 1991). Deterioration of the fruit stem and calyx As mentioned previously, deterioration of the fruit stem and calyx is a problem in tamarillo, since a healthy fruit calyx (see Plate XXXVIIA in the colour section)

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and stem (see Plate XXXVIIE in the colour section) are requirements for export, and factors that are considered by importers and wholesalers, despite it being purely an aesthetic problem that does not affect the fruit flesh quality or taste. Calyx lifting (see Plate XXXVIIC in the colour section) and blackening (see Plate XXXVIID in the colour section) show up after 28 days of storage at 4 °C and increase rapidly during subsequent shelf life, whereas stem yellowing (see Plate XXXVIIF in the colour section) and blackening (see Plate XXXVIIG in the colour section) are already obvious from 14 days onwards. Physical damage and fast loss of moisture after harvest are the main reasons for these stem and calyx problems (Sale and Pringle, 1999). Physical abrasion, such as occurs during brushing during packing, can also promote browning and blackening. Additionally, the colour changes of the stem from green to yellow have been associated with accelerated chlorophyll degradation (Pongjaruvat, 2008), and stem blackening with increased polyphenol oxidase activity (Sale and Pringle, 1999; Pongjaruvat, 2008). Several treatments, such as the application of wax to the stem and MAP to reduce water loss, have been tested to reduce stem browning, with little success. Eugenol, an antibacterial additive, has been shown to delay stem dehydration browning in cherry (Serrano et al., 2005) and table grape (Valverde et al., 2005; Valero et al., 2006), keeping their stems healthy, but when tried in MAP for tamarillo it did not show the same beneficial effect (Pongjaruvat, 2008). Other Colour leaching from the locules into the pericarp can occur, making the pericarp more red. The circumstances in which this happens have not been determined, but adverse atmospheric conditions seem to be one of the elicitors. 21.5.2 Pathological disorders Fungal infections due to field contamination dramatically reduce storage life of tamarillo fruit and these have not been successfully prevented by preharvest treatments (Sale and Pringle, 1999). The common fungal attacks are bitter rots, as circular and brown-black spots caused by Glomerella cingulata, Colletotrichum acutatum, C. gleosporoides, Phoma exigua, or Diaporthe phaseolorum (Hampton et al., 1983; Blank et al., 1987; Sale and Pringle, 1999; Manning and Woolf, unpublished data), and stem-end rots, as a soft brown rot occurring around the base of the stem caused by Botrytis (Sutton and Strachan, 1971) and possibly Phomopsis (Manning and Woolf, unpublished data). Application of captafol and benomyl field sprays in combination with a prochloraz and imazalil postharvest dip has been shown to improve fruit storability (Blank et al., 1987). The use of irradiation successfully inhibited the stem-end rots during storage, but this method caused tamarillo fruit tissue to be sensitive to low temperature injury, resulting in tissue breakdown and discolouration during cold storage (Sutton and Strachan, 1971). Hot water dips (50 °C for 8 min) directly after harvest successfully remove latent infections but

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can cause damage to the stem and the wax layer of the skin, which can result in higher levels of weight loss and susceptibility to invasion of secondary fungi (Yearsley et al., 1987). The commercial application of hot water dips is difficult, as tamarillo do not float (Hampton et al., 1983). When complementing these heat treatments with a postharvest fungicide dip (such as imazalil) and waxing, fruit can be stored for eight weeks at 3.5 °C followed by seven days at 20 °C (Yearsley et al., 1987). Although the hot water dip reduces fungal rots, it cannot prevent stem discolouration. Tamarillos produce a broad-spectrum invertase inhibitory protein that has antifungal and antibacterial activity and is involved in the plant defence mechanism (Ordóñez et al., 2000; 2006). 21.5.3 Insect pests and their control Tamarillos are generally regarded as pest-resistant, although they can be attacked by green aphids and fruit flies; and greenhouse thrips can cause damage to small fruit, which results in scaring (Rheinlander and colleagues, unpublished data). Aphids need to be controlled well, especially since they often spread viruses. Good orchard hygiene, pruning and weed control are the main techniques used to avoid aphid infection. Fruit fly can present a problem when exporting to countries with quarantine restrictions, but can be controlled using dimethoate or fenthion dipping or flood spraying, or using methyl bromide fumigation; but none of these is accepted in organic production.

21.6

Processing

Tamarillo fruit process extremely well. They can be frozen or canned and can be used for a range of products including jams, pulps, purees, chutneys, and juices. There is considerable potential for combining with milk products such as yogurts. The yellow cultivars are especially preferred for processing because of their average size, good flavour and because they contain fewer anthocyanins. The last factor is important to prevent reaction with the metal of the cans, which can cause blue discolouration of the product (Portela, 1999). More recently, tamarillo wine was produced in Venezuela with chemical and organoleptic characteristics similar to those of wine made from grapes (Alvarez et al., 2007). Processing is best carried out after removing the skin layer and the seeds because of the bitter nature of these components (Belén-Camacho et al., 2004). Extraction of carotenoids and anthocyanins from this material may be useful as a source of natural food colourants (Bobbio et al., 1983) or as functional food ingredients. Duran and Moreno-Alvarez (2000) optimised solvent mixtures and application to enable high carotenoid extraction from the pericarp. Belén-Camacho et al. (2004) characterised the oil content of both red and yellow cultivar seeds in order to assess their potential as raw material for a unique oil product manufacture. Thermal processing, such as pasteurisation, is often used to preserve fruit products. Thermal treatment of yellow tamarillo nectar can result in reduced

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vitamin C and carotenoid content of the final product in comparison with that of fresh nectar (Mertz et al., 2009a). Extraction of the effective broad-spectrum invertase inhibitory protein produced by the fruit may also be a useful resource as a natural biocide for reduction of postharvest losses in horticultural products (Ordóñez et al., 2006). Tamarillo and its processed products (in the form of juice and pomace) are considered good sources of antioxidants that could be used to make nutraceutical or functional-food products (Ordóñez et al., 2010).

21.7

Conclusions

The tamarillo is a subtropical fruit from the Solanaceae family, originating probably from the Andes. Different types of tamarillo are distinguished according to their skin colour, ranging from red to yellow, but no major differences in physiology have been noted besides the presence of anthocyanins in the red types and the absence of them in the yellow types. Tamarillo has an extended flowering and fruiting period, with a peak in fruit production in late autumn and winter. It is a non-climacteric fruit with little respiration and ethylene production after harvest, but ethylene can be used to accelerate fruit ripening. Tamarillos are optimally stored at 3 to 4.5 °C, and 90–95% RH, and lower temperatures will increase the risk of chilling injury. As fruit mature, their skin colour changes, and the juice yield, SSC, pH and SSC/TA ratio increase and firmness and TA decline. Stem and calyx quality are important factors and these also represent the main quality problem and the main challenge for the future. Tamarillo fruit adapt very well to processing and can be used as a vegetable in a manner similar to tomato, but are also often used in sweet preparations.

21.8

References

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Clark C J and Richardson A C (2002), ‘Biomass and mineral nutrient partitioning in a developing tamarillo (Cyphomandra betacea) crop’, Sci Hortic, 94, 41–51. Cohen D, van den Brink R C, MacDiarmid R M, Beck D L and Forster R L S (2000), ‘Resistance to tamarillo mosaic virus in transgenic tamarillos and expression of the transgenes in F1 progeny’, Proc XXV Internat Hortic Congress, Pt 11, 43–49. Dawes S N and Callaghan M E (1970), ‘Composition of New Zealand fruit. 1. Tamarillo’, N Z J Sci, 13, 447–451. Durán M G and Moreno-Álvarez M J (2000), ‘Evaluación de algunas mezclas de solventes en la extracción de carotenoides del pericarpio de tamarillo (Cyphomandra betacea Sendt)’, Cienc Tecnol Alim, 31, 34–38. El-Zeftawi B M, Brohier L, Dooley L, Goubran F H, Holmes R and Scott B (1988), ‘Some maturity indices for tamarillo and pepino fruits’, J Hortic Sci, 63, 163–169. Espina S and Lizana L A (1991), ‘Comportamiento de tamarillo (Cyphomandra betacea (Cav.) Sendtner) en almacenaje refrigerado’, Proc Interamerican Soc Tropic Hortic, 35, 285–290. Hampton R E, Blank R H, Dance H M and Olson M H (1983), ‘Tamarillo storage rot problems’, Proc 36th N Z Weed Pest Control Conf., 121–124. Harman J E and Patterson K J (1984), Kiwifruit, tamarillos and feijoas maturity and storage effects on keeping and eating quality, Wellington, New Zealand, Agrilink Horticultural produce and practice No. 103. Heatherbell D A, Reid M S and Wrolstad R E (1982), ‘The tamarillo-chemical composition during growth and maturation’, N Z J Sci, 25, 239–243. Heatherbell D A, Surawski J R and Withy L M (1975), ‘Identification and quantitative analysis of sugars and non-volatile acids in tamarillo fruit (Cyphomandra betacea)’, Confructa, 20, 17–22. Hilgert N I (2001), ‘Plants used in home medicine in the Zenta River basin, Northwest Argentina’, J Ethnopharmacol, 76, 11–34. Janet S (2005), Tariff and Trade Barriers. Wellington, New Zealand Horticulture Export Authority. Legiscomex (2008), ‘Frutas exóticas en Colombia/Inteligencia de mercados’, www. legiscomex.com/BancoMedios/Documentos%20PDF/est_col_frutas_exot_6.pdf [accessed May 2011]. Leterme P, Buldgen A, Estrada F and Londoño A M (2006), ‘Mineral content of tropical fruits and unconventional foods of the Andes and the rain forest of Colombia’, Food Chem, 95, 644–652. Lewis D H and Considine J A (1999a), ‘Pollination and fruit set in the tamarillo (Cyphomandra betacea (Cav.) Sendt.) 1. Floral biology’, N Z J Crop Hortic Sci, 27, 101–112. Lewis D H and Considine J A (1999b), ‘Pollination and fruit set in the tamarillo (Cyphomandra betacea (Cav.) Sendt.) 2. Patterns of flowering and fruit set’, N Z J Crop Hortic Sci, 27, 113–123. Lister C E, Morrison S C, Kerkhofs N S and Wright K M (2005), ‘The nutritional composition and health benefits of New Zealand tamarillos’, Crop & Food Research Confidential Report No. 1281. Manzano J E (2005), ‘Caracterización de frutos de tomate de arbol (Cyphomandra betaceae Cav. Sendtn.) y sus relativos en zonas montañosas de Venezuela’, Proc Interamerican Soc Tropic Hortic, 48, 149–151. Manzano J E and Diaz J G (2002), ‘Características de calidad en frutos almacenados de tomate de arbol [Cyphomandra betaceae (Cav.) Sendtn.]’, Proc Interamerican Soc Tropic Hortic, 46, 68–69. Márquez C J, Otero C M E and Cortés M R (2007), ‘Cambios fisiológicos, texturales, fisicoquímicos y microestructurales del tomate de árbol (Cyphomandra betacea S.) en poscosecha’, Vitae, 14, 9–16. Mertz C, Brat P, Caris-Veyrat C and Gunata Z (2009a), ‘Characterization and thermal lability of carotenoids and vitamin C of tamarillo fruit (Solanum betaceum Cav.)’, Food Chem, 119, 653–659.

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Mertz C, Gancel A L, Gunata Z, Alter P, Dhuique-Mayer C, et al. (2009b), ‘Phenolic compounds, carotenoids and antioxidant activity of three tropical fruits’, J Food Compos Anal, 22, 381–387. Moreno-Álvarez M J, Pinto M G, García Pantaleón D and Belén-Camacho D R (2007), ‘Efecto del ácido cítrico sobre la madurez del tomate de árbol’, Rev Facultad Agron (LUZ), 24, 321–342. Morton J (1987), Tree Tomato, Fruits of Warm Climates, Miami, Florida: Morton, Julie F. Mwithiga G, Mukolwe M I, Shitanda D and Karanja P N (2007), ‘Evaluation of the effect of ripening on the sensory quality and properties of tamarillo (Cyphomandra betaceae) fruits’, J Food Eng, 79, 117–123. Ojeda A M, Bermeo S P, Bastidas A R and Muñoz C (2009), ‘Produccion y comercializacion de tamarillo (Cyphomandra betacea Sent), para el mercado internacional’, Escuela Superior Politécnica del Litoral, Quito, Ecuador. Ordóñez R M, Cardozo M L, Zampini I C and Isla M I (2010), ‘Evaluation of antioxidant activity and genotoxicity of alcoholic and aqueous beverages and pomace derived from ripe fruits of Cyphomandra betacea Sendt.’, J Agric Food Chem, 58, 331–337. Ordóñez R M, Isla M I, Vattuone M A and Sampietro A R (2000), ‘Invertase proteinaceous inhibitor of Cyphomandra betacea Sendt fruits’, J Enz Inhib Med Chem, 15, 583–596. Ordóñez R M, Ordóñez A A L, Sayago J E, Nieva Moreno M I and Isla M I (2006), ‘Antimicrobial activity of glycosidase inhibitory protein isolated from Cyphomandra betacea Sendt. fruit’, Peptides, 27, 1187–1191. Ordóñez R M, Vattuone M A and Isla M I (2005), ‘Changes in carbohydrate content and related enzyme activity during Cyphomandra betacea (Cav.) Sendtn. fruit maturation’, Postharvest Biol Technol, 35, 293–301. Pongjaruvat W (2008), Effect of Modified Atmosphere on Storage Life of Purple Passion Fruit and Red Tamarillo, Palmerston North, New Zealand, Massey University. Popenoe H L, King S R, León J, Kalinowski L S and Vietmeyer N D (1989), Lost Crops of the Incas: Little-known Plants of the Andes with Promise for Worldwide Cultivation, Washington, D.C., The National Academy Press. Portela S I (1999), ‘Fisiología y manejo de poscosecha del tamarillo (Cyphomandra betacea)’, Av Hortic, 4, 40–50. Pratt H K and Reid M S (1976), ‘The tamarillo: fruit growth and maturation, ripening, respiration, and the role of ethylene’, J Sci Food Agric, 27, 399–404. Prohens J and Nuez F (2000), ‘The tamarillo (Cyphomandra betacea): A review of a promising small fruit crop’, Small Fruits Review, 1, 43–68. Prohens J, Ruiz J J and Nuez F (1996), ‘Advancing the tamarillo harvest by induced postharvest ripening’, HortScience, 31, 109–111. Richardson A and Patterson K (1993), ‘Tamarillo growth and management’, Orchardist, 66, 33–35. Romero-Rodriguez M A, Vazquez-Oderiz M L, Lopez-Hernandez J and Simal-Lozano J (1994), ‘Composition of babaco, feijoa, passion-fruit and tamarillo produced in Galicia (NW Spain)’, Food Chem, 49, 251–255. Sale P (2006), ‘Some interesting developments and the odd hiccup in the 2006 tamarillo season’, Orchardist, 79, 52–55. Sale P and Pringle G (1999), The Tamarillo Handbook: A Guide for New Zealand Growers and Handlers, Kerikeri, New Zealand, New Zealand Tamarillo Growers Association Inc. Serrano M, Martínez-Romero D, Castillo S, Guillén F and Valero D (2005), ‘The use of natural antifungal compounds improves the beneficial effect of MAP in sweet cherry storage’, Inn Food Sci Emerg Technol, 6, 115–123. Slack J M (1976), ‘Growing tamarillos’, Agric Gazette, 86, 2–4. Stangeland T, Remberg S F and Lye K A (2009), ‘Total antioxidant activity in 35 Ugandan fruits and vegetables’, Food Chem, 113, 85–91. Sutton H C and Strachan G (1971), ‘An attempt to control Botrytis rot in tamarillos (Cyphomandra betacea (Cav). Sendt) by electron irradiation’, N Z J Sci, 14, 1097–1106.

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Tee E S and Lim C L (1991), ‘Carotenoid composition and content of Malaysian vegetables and fruits by the AOAC and HPLC methods’, Food Chem, 41, 309–339. Tejeda T and Cortes S (1997), ‘Phenological behaviour of tree tomato (Cyphomandra betacea (Cav.) Sendt), in Cuba, during initial stages of establishment’, Cultivos tropicales, 18, 43–46. Torrado A, Suárez M, Duque C, Krajewski D, Neugebauer W and Schreier P (1995), ‘Volatile constituents from tamarillo (Cyphomandra betacea Sendtn.) fruit’, Flavour Fragr J, 10, 349–354. Tseng Y H, Liou C Y, Liu S C and Ou C H (2008), ‘Cyphomandra betacea (Cav.) Sendt. (Solanaceae), a newly naturalized plant in Taiwan’, Quarterly Journal of Chinese Forestry, 41, 425–429. Valero D, Valverde J M, Martínez-Romero D, Guillén F, Castillo S and Serrano M (2006), ‘The combination of modified atmosphere packaging with eugenol or thymol to maintain quality, safety and functional properties of table grapes’, Postharvest Biol Technol, 41, 317–327. Valverde J M, Guillén F, Martínez-Romero D, Castillo S, Serrano M and Valero D (2005), ‘Improvement of table grapes quality and safety by the combination of modified atmosphere packaging (MAP) and eugenol, menthol, or thymol’, J Agric Food Chem, 53, 7458–7464. Vasco C, Avila J, Ruales J, Svanberg U and Kamal-Eldin A (2009), ‘Physical and chemical characteristics of golden-yellow and purple-red varieties of tamarillo fruit (Solanum betaceum Cav.)’, Int J Food Sci Nutr, 60, 278–288. Vasco C, Ruales J and Kamal-Eldin A (2008), ‘Total phenolic compounds and antioxidant capacities of major fruits from Ecuador’, Food Chem, 111, 816–823. Wong K C and Wong S N (1997), ‘Volatile constituents of Cyphomandra betacea Sendtn. fruit’, J Essential Oil Res, 9, 357–359. Yearsley C W, McGrath H J W and Dale J R (1987), ‘Red tamarillos (Cyphomandra betacea): post-harvest control of fungal decay with hot water and imazalil dips’, N Z J Exp Agric, 15, 223–228.

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22 Tamarind (Tamarindus indica L.) E. M. Yahia, Autonomous University of Queretaro, Mexico and N. K.-E. Salih, Agricultural Research Corporation, Sudan

Abstract: Tamarindus indica L., commonly known as tamarind, is a multipurpose long-lived tree best known for its fruit. It is indigenous to tropical Africa and exotic to Asia and Central America. India and Thailand are the major tamarind world producers, generating 300 000 and 140 000 tons annually, respectively. There are two main types of tamarind: sour (the most common) and sweet (mostly comes from Thailand). Tamarind can be eaten fresh (ripe or unripe) and it can be consumed processed into different products. In addition to the use of tamarind fruit in food it has many uses in the pharmacological industry and folk medicine. The ripe tamarind pods are susceptible to different pest and diseases, especially when grown in a big plantation. This chapter will describe the nutritional importance and the postharvest handling of tamarind. Key words: Tamarindus indica, postharvest, handling, nutrition, storage, processing.

22.1

Introduction

22.1.1 Origin, botany, morphology and structure Tamarindus indica L. (syns. T. occidentalis Gaertn, T. officinalis Hook, T. umbrosa Salisb) belongs to the family leguminaceae (syns. Fabaceae) and subfamily Caesalpinaceae. The genus Tamarindus is monotypic, i.e. it contains a single species. Commonly, Tamarindus indica is known as tamarind (the trade and English name). In Spanish and Portuguese, it is called tamarindo; in French, tamarinier, tamarinde; in Dutch and German, tamarinde; in Italian, tamarindizio; in Hindi, it is known as tamarind, tamrulhindi and it has other local names as well (e.g. ambli, imli, chinch, etc.). In the eighteenth century, Linnaeus gave it the name Tamarindus indica, inspired by the Arabic name tamar-ul-Hind, meaning date of India. Tamarind is widespread throughout the tropics and subtropics and grows in more than 50 countries in Africa, Asia and Central America. It most probably

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originated in tropical Africa (Coates-Palgrave, 1988), although there is a common belief that tamarind is native to India (Morton, 1987) where it is believed to have been introduced thousands of years ago (Hort, 1916), and to have reached Central America in the seventeenth century with the Spanish and Portuguese (Patino, 1969). According to Salim et al. (1998) in Africa tamarind is native to Burkina Faso, the Central African Republic, Chad, Eritrea, Ethiopia, Gambia, Guinea, Guinea-Bissau, Kenya, Madagascar, Mali, Mozambique, Niger, Nigeria, Senegal, Sudan, Tanzania, Uganda and Zimbabwe and exotic to Mauritania, Togo, Cote d’Ivoire, Egypt, Libya, Ghana, Zambia and Liberia. Also, tamarind is exotic to Australia, Asia (Afghanistan, China, Bangladesh, India, Indonesia, Iran, Laos, Malaysia, Nepal, Pakistan, Philippines, Myanmar, Sri Lanka, Thailand, Papua New Guinea, Cambodia, Vietnam and Brunei) and the Americas (Brazil, Colombia, Cuba, Dominican Republic, Guatemala, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Puerto Rico and southern United States of America). It is widely used in Mexico (see Plate XXXVIII in the colour section between pages 238 and 239), especially in the preparation of drinks (tamarind water, tamarind juices) and desserts. Tamarind is an evergreen or semi-evergreen bushy tree that has a dense foliage crown. It is a slow growing tree; the annual growth rate of seedlings is about 60 cm and the juvenile stage takes between four and five years, but trees can reach up to 200 years of age. The tamarind tree can reach a maximum height of up to 20–30 m, with bole 1–2 m and trunk diameter 1.5–2 m (Jambulingam and Fernandes, 1986; Stross, 1995). Leaves are bright green in color, alternate and compound with 10–18 pairs of leaflets (see Plate XXXIXA in the colour section). Leaflets are 1.2–3.2 × 0.3–1.1 cm in size, petiolate, and rounded at the apex. Flowers are bisexual, 2.5 cm wide, five-petalled, borne in small racemes, and yellow with orange or red streaks. Buds are pink with 4 sepals and 5 petals. The fruit is a curved or straight pod with rounded ends, 12 to 15 cm in length, covered with a hard brown exterior shell. Fruit pulp is brown or reddish-brown when mature and the fruit pod contains between 1 and 12 flat and glossy brown seeds. Tamarind pulp, seeds and shell are about 55%, 34%, and 11%, respectively, of the tamarind fruit (Rao and Srivastava, 1974). The seed is made up of the seed coat or testa (20–30%) and the kernel or endosperm (70–80%). The shell is light greenish or scruffy brown in color (see Plate XXXIXB in the colour section). The shell is scaly and irregularly constricted between seeds; it is also brittle and easily broken when pressed. The pulp is soft and thick (Coronel, 1991; Purseglove, 1987). The seeds are 1.6 cm long, very hard, shiny, smooth and reddish or purplish brown in color with irregular shape and are joined to each other with tough fibers (Purseglove, 1987). Tamarind pods usually contain 1–12 seeds but the Indian pods contain 6–12 seeds, and are usually longer than the African and South American pods. There are two main types of tamarind: sour (the most common) and sweet (which mostly comes from Thailand). The tamarind tree has the capability to withstand long periods of drought because of its deep tap rooting and extensive lateral rooting system, and also the ability to grow in poor soils because of their nitrogen fixing property (Felker, 1981; Felker and Clark, 1980).

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22.1.2 Worldwide importance and economic value Tamarind is economically valuable and multi-purpose insofar as almost every part of the tree has a use, but the tree is best known for its fruit and the marketability of tamarind fruit has increased consistently over the years. The tamarind major production area is in Asia, where India is considered the major producer with a production of 300 thousand tons annually (El-Siddig et al., 2006) (Tables 22.1 and 22.2). According to the spices board of India, the production area was 58 624 ha in 2006–2007 and the export was 10 200 tons. The potential for Indian export in the past 5 years shows a good market for tamarind, especially in the Gulf Countries and Europe (Kumar and Bhattacharya, 2008). Thailand is the second major producer of tamarind, with 140 thousand tons produced in 1995 (Yaacob and Subhadrabandhu, 1995), and the export amounted to about 7000 tons in 1999. Sri Lanka exported 6903 tons of tamarind in 1997. Other Asian countries produce and export tamarind but on a much smaller scale compared to India and Thailand. In the Americas, Costa Rica produces about 220 tons of tamarind annually and is considered quite a large producer. The annual production of tamarind amounts to 37 tons in Mexico and 23 tons in Puerto Rico (Bueso, 1980). The Asian tamarind is mainly exported to Asian countries, Europe and North America, while the Table 22.1 Area (hectares), production and export (tons) and values (Rs. millions) of tamarind from India Year

Area

Production

Export

Values

2002–03 2003–04 2004–05 2005–06 2006–07 2007–08 2008–09

61 958 60 629 61 624 61 084 58 624 – –

178 974 183 871 194 032 192 186 190 073 – –

– –

– – 1833.98 3078.20 3000.00 3100.00 4105.00

5 944 14 101 10 200 11 250 11 500

Source: Spices Board India, Ministry of Commerce and Industry, Gov. of India. http://www.indianspices.com/

Table 22.2 Quantities (tons) and values (RS. millions) of different commodities of tamarind exported from India Commodity

Dried Fresh Flour meal Seeds

Quantity

Value

2000–01

2001–02

2000–01

2001–02

7071.14 2278.59 572.08 2997.39

4594.58 1434.15 817.97 887.38

151.782 33.932 11.348 47.131

109.667 23.988 15.528 19.322

Source: Spices Board India, Ministry of Commerce and Industry, Gov. of India. http://www.indianspices.com/

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American tamarind is mainly exported to North America and Europe. In most of the producing countries, tamarind does not grow on a commercial scale, and fruits are collected from the wild and home gardens. Although widespread in Africa, no African country cultivates tamarind on a commercial scale and almost all of the produce is consumed locally. Similarly, most of the tamarind produced in India and Thailand is also consumed locally. The sour tamarind is the most widespread; it comprises 95% of the total world production. Thailand is the largest producer of sweet tamarind, being 30% of its crop. 22.1.3 Culinary uses, nutritional value and health benefits Tamarind fruit pulp has many uses in domestic and industrial food and medicine and is considered the most valuable part of the tree. In most tamarind-producing countries, rural households dry tamarind pods in the sun, separate pulp from the fibers, seeds and shells, and compress and pack pulp in palm leaf mats, baskets, corn husks, jute bags, earthenware pots or plastic bags. The fruit pulp is a common ingredient in curries, sauces, and certain beverages. Ripe tamarind pulp, especially the sweet tamarind, is often eaten fresh. Both sour and sweet ripe tamarind pulps are also consumed processed in desserts, pickles, jams, candy, juice, porridge and drinks. Tamarind, especially the unripe pulp, is used as a spice and sauce in many Asian cuisines. In India a pickle made from tamarind pulp is used as seasoning to prepare fish. Also, unripe fruit dipped in salt or wood ash is eaten as a snack. Tamarind juice is very popular in many countries; a refreshing drink is prepared from the pulp water extract mixed with wood ash or sugar. In Eastern Africa, porridge is prepared from pulp juice cooked with sorghum or maize. Sometimes the pulp juice is fermented into an alcoholic beverage. In Burkina Faso, tamarind pulp extract is used to purify drinking water (Bleach et al., 1991). In many Asian countries tamarind balls are made from the pulp mixed with sugar. In Thailand, the pulp is mixed with salt, compressed and packed in plastic bags. In East India, the pulp is covered with salt, rolled into balls, exposed to dew and stored in earthenware jars (Chapman, 1984; Morton, 1987), whereas in Java, the salted pulp is rolled into balls, steamed and sun-dried, then exposed to dew for a week before packing in stone jars. In Sri Lanka, the dried pulp is mixed with salt, packed in clay pots and kept in a dry place; seedless pulp is stored in plastic bags in retail shops (Gunasena, 1997). Tamarind seeds are eaten, roasted or boiled, during off-seasons and food shortages. Roasting the seeds is usually followed by decorticating the testa from the edible kernel. Roasted tamarind seeds can also be used as a substitute for coffee. The seed oil is edible and has many culinary uses. Of the tamarind seed kernel, 46 to 48% consists of a gel-forming substance, known as jellose or polyose, which has many applications in the food industry. Jellose is mainly a polysaccharide and can be used for the preservation, thickening, stabilizing and gelling of food (Gliksman, 1986; Chen et al., 1988; Kawaguchi et al., 1989). Unlike fruit pectin, tamarind seed polysaccharide is characterized by its ability to form gels over a

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wide range of pHs and gelatinizes with sugar concentrates in cold neutral aqueous solutions (Savur, 1948). Also, tamarind polysaccharides are heat resistant and are not affected by long boiling periods, while fruit pectin degrades to one-third of its original value after one hour of boiling. Tamarind kernel powder (TKP) is a more effective gelling agent when combined with other gums (Yin and Lewis, 1981). Protein concentrates have also been made from tamarind kernel powder (Rao and Subramanian, 1984) and can be used to prepare jelly, and fortified bread and biscuits (Bhattacharya, 1990; Bhattacharya et al., 1994). The shelf life of fish can be extended by using TKP as a film forming gum (Shetty et al., 1996). Tamarind fruit pulp is a good source of minerals and a rich source of riboflavin, thiamin, and niacin, but it is poor in vitamins A and C (Table 22.3). Shankaracharya (1998) found that the whole tamarind seed contains 13% crude protein, 6.7% crude fiber, 4.8% crude fat and 5.62% tannins. Also, the seed contains good phytic acid, pentose, mannose, and glucose as principal soluble sugars (Ishola et al., 1990) as well as valuable amino acids (Shankaracharya, 1998; Bhattacharya et al., 1994). Bhattacharya et al. (1994) showed that tamarind seed is rich in glutamic acid, aspartic acid, glycine, and leucine, but deficient in sulphur-containing amino acids. The edible seed kernel was reported to be rich in phosphorus, potassium, and magnesium, but has a calcium content comparable with other cultivated

Table 22.3

Nutrition constituents of tamarind pulp per 100 g

Constituent

Amount per 100 g

Energy Moisture Protein Fat Fiber Carbohydrates Invert sugars (70% glucose; 30% fructose) Ash Calcium Phosphorus Iron Sodium Potassium Vitamin A Thiamine Riboflavin Niacin Ascorbic acid Tartaric acid

115–216 calories 28.2–52 g 2.40–3.10 g 0.1 g 5.6 g 51.5–67.4 g 30–41 g 2.9–3.3 g 35–170 mg 54–160 mg 1.3–10.9 mg 24 mg 116–375 mg 15 I.U. 0.16 mg 0.07 mg 0.6–0.7 mg 0.7–3.0 mg 8–23.8 mg

Data derived from: Morton (1987); Khairunnuur et al. (2009); Khanzada et al. (2008)

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Mineral content of tamarind pulp, seed, kernel, and testa

Mineral mg100 g−1

Pulp

Seed

Kernel

Testa

Calcium Phosphorus Magnesium Potassium Sodium Copper Iron Zinc Nickel Manganese

81.0–466.0 86.0–190.0 72.0 62.0–570.0 3.0–76.7 21.8 1.3–10.9 1.1 0.5 –

9.3–786.0 68.4–165.0 17.5–118.3 272.8–610.0 19.2–28.8 1.6–19.0 6.5 2.8 – 0.90

1200.0 – 180.0 1020.0 210.0 – 80.0 100.0 – –

100.0 – 120.0 240.0 240.0 – 80.0 120.0 – –

Data derived and adapted from: Gunasena and Hughes (2000), Khanzada et al. (2008); Khairunnuur et al. (2009)

legumes (Table 22.4) (Bhattacharya et al., 1994; Khairunnuur et al., 2009). The seed is also rich in palmitic (14–20%), oleic (15–27%) and linoleic (36–49%) fatty acids (Andriamanantena et al., 1983; Khairunnuur et al., 2009). Tamarind fruits are known for their medicinal properties and have been used as herbal medicine in tamarind-producing countries (Jayaweera, 1981). Tamarind pulp is used to treat conditions such as intestinal ailments and skin infections which the pulp juice is used as a gargle to treat sore throats. Tamarind pulp also has uses as an anti-inflammatory (Rimbau et al., 1999) and has anti-bacterial, anti-fungal and molluscicidal properties as well (Imbabi et al., 1992). Tamarind pulp extract is used to cure malaria fever, alleviate sunstroke and as a digestive agent, and in the pharmaceutical industry, tamarind pulp is a common ingredient in cardiac and blood sugar reducing medicines. Tamarind seeds are considered a famine food, rich in protein. After removing the testa, which contains tannin and other anti-nutritional factors, they are consumed to prevent undesirable effects such as depression, constipation, and diarrhea (Rao and Srivastava, 1974; Khairunnuur et al., 2009). The seed was reported to have anti-diabetic effects (Rama Rao, 1975; Maiti et al., 2004) and to treat dysentery, ulcers and bladder stones (Rama Rao, 1975). Seeds have also shown anti-oxidant activity (Osawa et al., 1994; Luengthanaphol et al., 2004; Khairunnuur et al., 2009). Shimohiro (1995) reported that the quality of food was improved by adding the polysaccharide hydroxylates or xyloglucan oligosaccharides of tamarind seeds, which are known to have hypolipidemic effects. The tamarind seed coat was reported to be rich in procyanidin, which is known to have an anti-obesity effect (Koichi et al., 1997; Osumu et al., 1997), while a reduced-calorie food can be prepared using the cellulase hydrolysate of a tamarind polysaccharide (Whistler, 1991; Singer, 1994). Patil and Nadagoudar (1997) reported that polysaccharides derived from tamarind kernel powder were found to be suitable substitutes for corn steep liquor in the production of penicillin. The glucosyl transferase inhibitor, extracted from tamarind husks, was found to

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have an anti-dental caries effect (Tamura et al., 1996) and tamarind kernel powder is an ingredient of several cosmetic preparations.

22.2

Fruit growth and ripening

22.2.1 Fruit growth, development and maturation Tamarind fruit goes through growth, maturation and ripening stages before being ready for harvesting. Tamarind pulp shows a change in color during the different developmental stages; in the case of sweet tamarind, the pulp color changes from yellowish green at the half-ripe stage, and to reddish brown at the fully-ripe stage. Also, the pulp shrinks due to loss of moisture and becomes sticky, the immature pods have green and tender shells and the seeds are soft and whitish. As the pods mature, the shell develops into a brown color, the pulp turns sticky and brown or reddish-brown, and the seeds become harder and darker. When fully ripe, the shells become brittle and easily broken. Fruit ripening is characterized by an increase in the total acidity, sugars and alcohol insoluble materials of the pulp (Hernandez-Unzon and Lakshminarayana, 1982b). Total ash, phenolics and pectins increase in the peel but decrease in the pulp. 22.2.2 Respiration, ethylene production and ripening Tamarind fruit is non-climacteric (Yahia, 2004); it produces little or no ethylene and there is no large increase in CO2 production. The maximum CO2 production occurs four weeks after fruit set and gradually declines thereafter (HernandezUnzon and Lakshminarayana, 1982b). The pods reach the ripening stage in 8–10 months after flowering while the fruit is fully ripe when up to half of its original water content is dehydrated. Dehydration begins 203 days after fruit set and may continue to the 245th day (Chaturvedi, 1985). Fruit pods are harvested green for flavoring, and ripe for processing. The fruits of the sweet type are also harvested at two stages, half-ripe and fully-ripe.

22.3

Maturity and quality components and indices

A tamarind tree takes more than seven years to start fruiting and 10–12 years to produce economically appreciable amounts of fruits. Tamarind fruit growth is a typical sigmoid type (Hernandez-Unzon and Lakshminarayana, 1982a). The fully ripened fruits can remain on the tree until the next flowering period without showing any significant deterioration in quality (Rama Rao, 1975); however, they can be subjected to bird and insect attack. The physical separation of the peel from the pulp results from the loss in water content. It is recommended that fruit be harvested when the moisture content is less than 20% to facilitate the separation of the shell from the pulp. Pods from the same tree do not reach maturity at the same time, which makes selective harvesting a necessity.

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Preharvest factors affecting fruit quality

22.4.1 Rainfall The tamarind tree is well adapted to semiarid tropical conditions and grows well with an evenly distributed mean annual rainfall of 500–1500 mm (FAO, 1988; Jama et al., 1989; Hocking, 1993). In areas where annual rainfall is less than 500 mm, the trees are usually located near the water table or along water courses. The minimum annual rainfall which tamarind can tolerate is 250 mm and the maximum is up to 4000 mm in well-drained soil (Duke and Terrell, 1974). Tamarind grows well under wet conditions but does not flower (Allen and Allen, 1981; Morton, 1987) as dry weather is important for flowering and fruiting. It produces more fruit when subjected to a fairly long annual dry period (Allen and Allen, 1981; von Maydell, 1986) as a deep and extensive root system helps the tree to grow in very dry areas and withstand up to six months of drought (Coronel, 1991). This can be observed in the north and south dry zones of Sri Lanka, where there is a prolonged dry season of over 4–6 months. In dry zones the bearing ability of tamarind is comparatively less than those grown in intermediate rainfall areas as a sharp drop in rainfall and air temperature increases the curving of tamarind pods due to the low moisture content. Tamarind is usually evergreen but may shed its leaves in very dry conditions during the hot/dry season (Morton, 1987).

22.4.2 Temperature Tamarind grows within an annual temperature range of 33–37 °C and at a minimum temperature of 9.5–20 °C. Older trees can withstand temperatures as high as 47 °C and as low as −3 °C without serious injury (Verheij and Coronel, 1991). Tamarind may not survive in an altitude higher than 2000 m (Roti-Michelozzi, 1957; Dale and Greenway, 1961; Brenan, 1967; FAO, 1988; Jama et al., 1989), probably because of the low temperature rather than the altitude itself. It is very sensitive to fire and frost and requires protection when small (Troup, 1921; NAS, 1979) and is a light-demanding tree. The strong and pliant branches and deep and extensive root system make the tree wind-resistant (Coronel, 1986) and it is therefore known as the hurricane-resistant tree (NAS, 1979; von Maydell, 1986; von Carlowitz, 1986).

22.4.3 Soil The tamarind tree can grow in a wide range of soils and has no specific soil requirement (Chaturvedi, 1985; Sozolnoki, 1985; Galang, 1955). The tamarind tree has the ability to grow in poor soils because of its nitrogen fixing capability (Felker, 1981; Felker and Clark, 1980) and it can grow on rocky soil too. In India and Thailand, tamarind has been reported to grow on sodic and saline soils and on degraded land as well (Anon, 1991; Nemoto et al., 1987). Old tamarind trees have been found growing close to the sea (NAS, 1979; Pongskul et al., 1988;

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Anon, 1991). Pot experiment results showed that tamarind can grow in soil containing up to 45% exchangeable sodium (Dwivedi et al., 1996). El-Siddig et al. (2004a, 2004b) found a slight delay in emergence, but no effect on seedling growth, with up to 30 mM NaC1 salinity, while Gebauer et al. (2001) reported that tamarind seedlings can tolerate salinity up to 80 mM NaCl. It prefers soils that favor the development of a long tap root (Galang, 1955; Kelly and Cuny, 2000; Rao et al., 2000). Tamarind does not withstand low water-drainage soil (Relwani, 1993; Vogt 1995). The optimum pH is slightly acidic, 5.5–6.8 (FAO, 1988), though it also grows well in alkaline soils (Singh et al., 1997, quoted from Rao et al., 1999). It has been suggested that the association of tamarind with anthills and termite mounds may be due to a preference for slight lime content (Jansen, 1981) and aerated soil (Dalziel, 1937; Eggeling and Dale, 1951; Irvine, 1961; Allen and Allen, 1981).

22.5

Diseases and pests and their control

Tamarind fruits are subject to pests and diseases but are usually very tolerant to pathogens and insects, except in large plantations, because of their low moisture content and high content of acids and sugars. Also, the high phenolic content in the peel makes the fruit highly resistant to attacks from pathogens. Pulp separated from peel has good keeping quality but is subject to various molds in refrigerated storage. There are more than fifty insect pests that have been reported to attack tamarind in India (Joseph and Oommen, 1960; Senguttavan, 2000). These pests attack the tamarind tree at different growth stages; in the nursery as seedlings, and in the field once mature. They also attack different parts of the tree including stem, bark, branches, leaves, flowers and fruits. Fruits are attacked at different stages of ripening before and after harvesting. All these pests and diseases are of different economic importance, causing reduction in fruit production to different extents. In humid climates, fruit are readily attacked by beetles and fungi, and should therefore be harvested before they are fully ripe. The most serious pests of the tamarind are hard scale insects that suck the sap of the buds and flowers and accordingly reduce fruit production (Butani, 1978). The most important of these is the oriental yellow scale insect (Aonidiella orientalis). These scale insects can be controlled by removing the affected parts of the tree at an early stage while serious infestation can be controlled effectively using pesticides such as Diazinon or Carbosulphan at 0.1% solution (Butani, 1979). The mealy-bugs Nipaecoccus viridis and Planococcus lilacinus suck the sap of leaflets, causing defoliation, and may feed on young fruits; Chionaspis acuminata-atricolor and Aspidiotus spp suck the sap of twigs and branches. Mechanical control of mealy bugs can be achieved by removing the infected parts, but when serious infestations take place, chemicals such as Diazinon or Carbosulphan at 1% solution can be sprayed (Butani, 1979). Caterpillars, Thosea aperiens, Thalarsodes quadraria, Stauropus alternus, and Laspeyresia palamedes;

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the black citrus aphid, Toxoptera aurantii; the white fly, Acaudaleyrodes rachispora; thrips, Ramaswamia hiella subnudula, Scirtothrips dorsalis, and Haplothrips ceylonicus; and cow bugs, Oxyrhachis tarandus, Otinotus onerotus, and Laptoentrus obliquis, and other predators attack tamarind leaves or flowers. Other important pests that attack tamarind include fruit borers such as larvae of the cigarette beetle, Lasioderma serricorne, also of Virachola isocrates, Dichocrocis punctiferalis, Tribolium castaneum, Phycita orthoclina, Cryptophlebia (Argyroploca) illepide, Oecadarchis sp., Holocera pulverea, Assara albicostalis, Araecerus suturalis and Aephitobius laevigiatus. The fruit borer Aphomia gularis, the tamarind beetle Pachymerus (Coryoborus) gonogra and the tamarind seed borer Calandra (Sitophilus) linearis attack ripening pods before and after harvest. The rice weevil Sitophilus oryzae, rice moth Corcyra cepholonica, and the fig moth Ephestia cautella infest the fruits during storage. The borer Rhyzopertha dominica infests tamarind seeds during storage. Larvae of the groundnut bruchid beetle are serious pests that attack the fruit and seed in India while Bacterial leaf-spot is caused by Meliola tamarindi. Rots attacking the tree include saprot (Xylaria euglossa) brownish saprot (Polyporus calcuttensis), and white rot (Trametes floccosa). The tamarind tree is also susceptible to nematodes (e.g. Xiphinema citri and Longidorus elongates) that attack the roots of older trees. Other minor pests in India include lac insect and bagworms.

22.6

Postharvest handling factors affecting quality

22.6.1 Temperature management Storage for long periods under poor conditions, such as exposure to extremes of temperature and humidity, causes gradual changes in color from brown or yellowish-brown to black colors (FAO, 1989). Also, high temperatures cause pulp to lose moisture and become sticky and curved. 22.6.2 Water loss Drying the fruits in the sun for 3–4 days is used to remove excess moisture and prevent the growth of molds. However, severe dehydration associated with sharp water loss causes curving of the fruits which are considered of lower quality compared to straight pods (Yahia, 2004). 22.6.3 Physical damage The main problem with fresh sweet tamarind is the damage caused by packaging, which deteriorates the fruit quality and reduces the amount of consumable fruit. Also harvesting the fruits, which is usually done by shaking the branches, might result in fruit damage. A better quality of fruit could be obtained by using scissors to harvest the fruits, especially in the case of the sweet tamarind type.

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Postharvest handling practices

22.7.1 Harvest operations Pod yield stabilizes at about 15 years and continues for up to 50 or 60 years. Tamarind fruits are mature and ready for harvesting when a hollow and loose sound is produced by finger pressing, as the pulp shrinks with maturity and the shell becomes brittle. Also, the change in testa color might indicate the maturity of the fruit. However, it is not always easy to determine whether the fruits are ready for harvesting, as the testa color only changes slowly as the pods mature. Individual fruits on the same tree also mature at different times, making selective harvesting necessary. Pods are harvested at different stages of ripeness, according to how they are going to be used. Immature green fruits are usually harvested earlier for flavoring. In most countries, the sour tamarind ripe fruits are usually gathered by shaking the branches and collecting the fruits that have fallen; the remainder of the fruit is left to fall naturally when ripe. Sweet tamarind fruits tend to gain higher market prices, and therefore are carefully picked by hand. To avoid damaging the pods and to increase the marketability of both sweet and sour types, harvesting by clipping should be practiced (Coronel, 1991). Pickers should not knock the fruits off the tree with poles, as this will damage developing flowers and leaves. Generally, the fruits are left to ripen on the tree before harvesting, so that the moisture content is reduced to about 20%. If unharvested, the pods may remain hanging on the tree for almost one year after flowering and sometimes until the next flowering period (Chaturvedi, 1985), and eventually will fall naturally. Fruits for immediate processing are often harvested by pulling the pod away from the stalk, which is left with the long, longitudinal fibers attached. Beetles and fungi readily attack ripe fruit in humid climates, and therefore they should be harvested before they are fully ripe.

22.7.2 Packinghouse practices One of the most important operations in a packing line is sorting for maturity, color, shape, size, and defects. The efficiency and effectiveness of sorting govern the quality standard of the packing lines and product (Office of Thai Agricultural Commodity and Food Standard, 2003), which in turn determines the marketability of the product. Manual sorting continues to be the most prevalent method used, although it is costly in terms of labor and time. Also, the lack of trained labor is one of the reasons that manual sorting may become inefficient and cause damage. One of the most practical and successful techniques for nondestructive quality evaluation and sorting of agricultural products is the electro-optical technique, which judges the optical properties of the product (Chen, 1996). This technique, which can be used to detect color uniformity, shape, size, external defects, foreign materials, and disease, has been used for postharvest grading for a wide variety of agricultural products including tamarind. Jarimopas et al. (2008) proposed packaging in a sleeve design, 15 cm in diameter by 20 cm in height, containing a mixture of 5 mm foam balls and sweet tamarind inserted vertically. This packaging

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imparts 15 to 16% of the damage of conventional packaging and costs half the price. 22.7.3 Control of ripening and senescence Tamarind fruit, as a non-climacteric (Yahia, 2004), will not ripen any further after harvest. The flavor, juice, sugars and some other contents remain unchanged. No information is readily available on techniques for controlling tamarind ripening. 22.7.4 Recommended storage and shipping conditions The high soluble solids content to titratable acidity (SSC : TA) and the low water content of tamarind fruit contributes to its long storage-life. Tamarind can be stored with the shell, or as a separated dry pulp, and tightly packaged pods can be stored at 20 °C for several weeks. The pulp of mature tamarind is commonly compressed and packed in palm leaf mats or plastic bags and stored at 20 °C for a significant period when processed into paste. It can be frozen and stored for one year, or refrigerated for up to six months. Under dry conditions the pulp remains good for about one year, after which it becomes almost black. In humid weather, especially, the pulp becomes soft and sticky as pectolytic degradation takes place and moisture is absorbed (Lewis and Neelakantan, 1964a; Anon, 1976). During storage, the dry, dark-brown pulp becomes soft, sticky, and almost black. The pulp can be stored for a longer period after drying or steaming. According to the research findings of CFTRI (Central Food Technological Research Institute, Mysore, India), the pulp could be preserved well for 6–8 months, without any treatment, if it is packed in airtight containers and stored in a cool dry place (Shankaracharya, 1997). The tamarind kernel powder is liable to deterioration during long storage, particularly in a moist environment; thus a dry place in moisture proof containers is preferred, after suitable fumigation. The powder may be mixed with 0.5% of sodium bisulphite before packing to prevent enzymic deterioration (Anon, 1976).

22.8

Processing

22.8.1 Processing of tamarind pulp Fresh-cut processing is not an industrial practice: it is usually carried out on a smaller scale when the fruits are intended to be eaten immediately. Fresh-cut tamarind is processed to make tamarind balls mixed with sugar after removing the shells, seeds and fibers. In Asia, the immature green pods are often eaten dipped in salt as a snack. In the Bahamas the unripe pods are roasted in coal, peeled back and the sizzling pulp is dipped in wood ash and eaten. In processing factories, tamarind pulp is separated from the fiber and seed, then mashed with salt before being packed into bags and if tamarind is intended to be stored for a long period, drying or freezing is required. To preserve tamarind,

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the fruit are shelled, layered with sugar in boxes or pressed into tight balls and covered with cloth and kept in a cool and dry place. For shipment, tamarinds may be shelled, layered with sugar in barrels and covered with boiling syrup. East Indians shell the fruit and sprinkle them lightly with salt as a preservative. In Java, the salted pulp is rolled into balls, steamed and sun-dried, then exposed to dew for a week before being packed in stone jars. In India, the pulp, with or without seeds and fibers, may be mixed with salt (10%), pounded into blocks, wrapped in palm-leaf matting, and packed in burlap sacks for marketing. To store for long periods, the blocks of pulp may be first steamed or sun-dried for several days. During pre-processing, fresh tamarind fruit is subjected to sun-drying or small scale dehydrators are sometimes used. The dry fruit is cracked, the pulp and fibers are separated and the seeds are removed. Pods can be store for several weeks at 20 °C. Also, pulps can be stored for 4–6 months at 10 °C by packing in high density polythene. Mixing with salt can extend the storage period to one year. Tamarind juice is usually prepared by boiling tamarind pulp in water and filtering the juice to remove the pulp before pouring into bottles and sealing. Tamarind concentrate is easily dispersible in water, and can be used for many purposes, such as in ketchups, sauces, soft drinks, dairy products and as a souring agent. It is prepared by soaking the tamarind pulp in water and boiling, separating fine and pulpy matter using a filter, then pressing the residue and mixing this with the extract. The filtered extract is concentrated by evaporating it in a vaccum, filling containers, cooling and sealing, and storing in airtight plastic or glass bottles or cans, in the dark, for over a year. Tamarind is often further processed into drinks and sweets or packaged into more convenient forms for export. In some parts of India, it is made into a jelly by mixing with water and sieving. It is then compressed into moulds and can be cut like cheese when required. 22.8.2 Processing of tamarind seed The hard, brown outer testa has to be completely removed from the kernel to prevent it from causing undesirable effects such as depression, constipation, and gastrointestinal inflammation, so the testa is separated from the kernels by either roasting or soaking the seed in water. Washing the seeds helps to remove the adhering pulp and to float away partially hollow infected seeds. When roasting, the temperature and duration of heating should be controlled to avoid the development of any undesirable characteristics in the isolated gum (Anon, 1976). The parched seed is then fed into a grain cleaner to remove the testa and dirt (Whistler and Barkalow, 1993). Very white tamarind kernel powder can be obtained by hydrating the seeds at room temperature for 24 hours, drying in the shade for 24 hours and then sand roasting at 125–175 °C for 3–8 minutes. Different processing methods to remove the testa were reported by Kumar and Bhattacharya (2008).

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Conclusions

The intrinsic value of raw tamarind can be further enhanced through value addition activities and there is a good market for these processed products both in the domestic as well as in international markets.

22.10

References

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Rimbau V, Cerdan C, Vila R and Iglesias J (1999), Antiinflammatory activity of some extracts from plants used in the traditional medicine of North-African countries, Phytotherapy Research, 13(2), 128–132. Senguttuvan T (2000), Insect pest associated with three semi arid fruits under agroforestry, Insect Environment, 6(2), 78. Shankaracharya NB (1998), ‘Chemical and Technological Aspects of Tamarindus Indica Fruit.’, Proc. Nat. Sym. on Tamarindus indica L, Tirupathi (A.P.), organized by Forest Dept. of A.P., India, 27–28 June, 1997, pp. 226–30. Tsuda T, Fukaya Y, Ohshimo K, Yamamoto A, Kawakishi S and Osawa T (1995a), Antioxidative activity of tamarind extract prepared from the seed coat (Japanese), J Japanese Food Sci Technol (Nippon-Shokuhin-Kogyo- Gakkaishi), 42, 430–435. Tsuda T, Watanabe M, Ohshima K, Yamamoto A, Kawakishi S and Osawa T (1994), Antioxidative components isolated from the seeds of tamarind (Tamarindus indica L.), J Agric Food Chem, 42, 2671–2674. von Maydell HJ (1986), Trees and Shrubs of Sahel. Their Characteristics and Uses, Deutsche Gesellschaft für Technische Zusammenarbeit, Eschborn, Germany. Yaacob O and Subhadrabhandu S (1995), The Production of Economic Fruits in South East Asia, Oxford University Press, 133–142. Yahia EM (2004), ‘Date’, in: U.S. Dept. Agric. Agric. Handbook #66: (http://www.ba.ars. usda.gov/hb66/index.html).

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23 Wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry) and related species Z.-H Shü, Meiho University, Taiwan, C.-C. Shiesh and H.-L. Lin, National Chung-hsing University, Taiwan

Abstract: The wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry), belongs to Myrtaceae and has been commercially planted in many countries, such as Taiwan, Thailand, Indonesia and Malaysia. There are two major parts in this chapter: the first part introduces the origin, biology and preharvest cultural practices; the second part deals with postharvest handling and storage. The fruit of the wax apple is fragile, non-climacteric with a short shelf life. Water loss is a big problem for wax apple storage so to keep the moisture and decrease the perishing process, modified atmosphere packaging with temperatures between 10 to 12 °C is recommended for the storage of wax apple fruits. Key words: Syzygium samarangense, wax apple, postharvest, handling, storage.

23.1

Introduction

23.1.1

Origin, botany, morphology and structure

Origin and worldwide importance The wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry; other names are Java apple, wax jambu and water apple), which belongs to the Myrtaceae, is native to the Malaysian Archipelago and to the Andaman and Nicobar islands where the trees grow in coastal rainforests (Morton, 1987). Other species with similar fruits for fresh consumption that are commercially important are the water apple Syzygium aqueum, the rose apple Syzygium jambos, and the Malay apple Syzygium malaccense (Nakasone and Pall, 1988). All these species have spread throughout the tropical areas of the world. The fruit of Syzygium jambos, the rose apple, is relatively round to oval shaped and has the scent of a rose (Morton, 1987).

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The flower and fruit of Syzygium malaccense, the Malay apple, are the most beautiful of those of the four species. The fruit of the water apple (Syzygium aqueum) is very similar to that of the wax apple (Syzygium samarangense), but it is smaller and insipid. The fruit of the wax apple is larger and sweeter (Shü and Paull, 2008; see Plate XL in the colour section between pages 238 and 239) and since it is the most delicious, it has been commercially planted in many countries, such as Taiwan, Thailand, Indonesia and Malaysia (Shü et al., 2008, 2009). Most research focuses on Syzygium samarangense since it is the only species commercially planted on a large scale among the four important freshly consumed species. The introduction of the biology, production and postharvest technology of the present article are thus based primarily on Syzygium samarangense. Biology The tree of the wax apple can grow to a height of 5–15 m depending on environmental conditions (Young, 1951), with flowers appearing in March in south Taiwan and fruits ripening in May under natural conditions. Fruits vary greatly in size, shape and skin color. The fruit size can be as small as about 4.3 cm long and 4.7 cm wide to more than 5.2 cm long and 5 cm wide (bell-shaped) or 7 cm long and 4 cm wide (elongated). Fruit mass ranges from 28 g to 100 g to the jumbo sized of more than 200 g per fruit. Fruit shape ranges from round to bell-shaped, oval or elongated and skin color diverges from white to pale green to dark green, pink to red to deep red. The fruit of wax apple are sweet when eaten fresh or cooked. Therefore they are better for eating than the Malay apple and other species in the same genus. A small percentage of the fruit is used for sauces, jams and jellies. Wax apple trees are tropical and cannot tolerate temperatures below 7 °C, preferring temperatures above 18 °C (Kuo, 1995; Huang et al., 2005). Fruits of wax apples prefer warm temperatures for normal growth and development as low temperatures impede fruit growth and red color development, while high temperatures accelerate fruit growth and ripening but inhibit red color development. The flesh is juicy, fragrant, crisp and sweet. Water content of the fruit is 92.9%, protein 0.35%, carbohydrate 6%, crude fiber 0.46% and ash (minerals) 0.21% (Shü and Paull, 2008). Flowering and fruiting ‘Pink’ is the leading cultivar, representing 85% of the planted areas in Taiwan (Shü et al., 2007; Wang, 2006). Flowers appear in March in south Taiwan and fruits ripen in May under natural conditions (Young, 1951). However, ‘Pink’ blooms and sets fruit almost year-round after flower forcing (Shü et al., 1996; Wang, 1991). As a result, fruits at different growing stages could be found in different orchards, on different trees and even on the same tree. The wax apple is a heavy producer on well-fertilized good soils and can produce more than 200 clusters per tree, with 4–5 fruits in each cluster when mature (see Plate XLI in the colour section). Average fruit weight of the ‘Pink’ variety is about 100 g, however a single fruit of ‘Big Fruit’, mutants of ‘Pink’, weighs from 150 g to more than 200 g (Chiu, 2003).

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Postharvest biology and technology of tropical and subtropical fruits

Climates and soils Wax apples prefer full sunlight for normal growing and fruiting, although they tolerate shade (Wang, 1991), and the best growing temperature for wax apple is around 25 °C. Temperatures under 8 °C may cause severe damage, both on the fruits and leaves. The wax apple can be grown on very wide range of soils from sandy to clayey and from acid to alkaline. However, for best fruit quality, fertile, wet and slight alkaline soils are preferred. Cultivars The wax apple, being planted commercially, has many cultivars. ‘Pink’ has been the leading cultivar in Taiwan, but other important cultivars in Taiwan are ‘Black King Kong’, ‘Light Red’, ‘Dark Red’, ‘Green’, ‘White’, and ‘Malacca’ (Shü et al., 2007). The major wax apple cultivars in Thailand are ‘Ma Mieaw’, ‘Nam Dokmai’, ‘Gam Hmam’, ‘Kaeg Dam’ and ‘Thub Thim Chan’. There are four cultivars grown in Malaysia, namely, ‘Pale Green’, ‘Dark Red’, ‘Light Red’ and ‘Green’ (Shü et al., 2008). Indonesia has the most abundant varieties, where wax apples are mostly grown as backyard trees covering an area of a couple of villages in a district, also known as ‘centers of production’. The largest centers of production are in Java and Madura Island. The most popular local cultivars are ‘Citra’, ‘Cincalo’, ‘Lilin Merah’, ‘Camplong’, ‘Kaget’, and ‘Semarang Prada’ (Shü et al., 2008). Propagation The wax apple can be propagated using seeding, cutting, grafting or air-layering (the most commonly used method). Most often air-layering is practiced during warm and wet seasons when wax apple trees grow rapidly. The bark, together with the vascular cambium, on two- to three-year-old healthy branches are removed (girdled) first for air-layering practice. The remaining wood (secondary xylem) are covered with wetted sphagnum moss and then covered with a plastic film to keep the moisture. It takes about one month to initiate new roots from the abaxial sides of the barks where girdles were taken. The rooted branches are removed from the mother plants when roots are well developed and brown in color (Wang, 2006). Planting The wax apple trees can be planted from 5 m × 5 m to 7 m × 8 m depending on different management systems. Avoid overcrowding of the trees and branches since this may cause self-shading, extra pest control practices, and branch die-back which reduces yield and produces low-quality fruits (Wang, 2006). Training and pruning Canopy size is important for wax apple tree management and fruit quality. Usually good quality wax apple fruits are located at the lower parts of the canopy, either

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on the big branches or on the truck. Adequate canopy size control is extremely important for keeping fruit quality high since commercial wax apple trees bear fruits two to three times per year (Wang, 2006). Suitable training to keep the tree at medium size (averaging about 3 m high) is important since it saves labor on pruning, bagging, spraying, thinning fruits or harvesting. Besides, shorter trees are more resistant to strong wind damage. For wax apple tree production there are mainly three training systems, namely bald-cut, semi-bald cut and evergreen, with heavy, medium and light pruning practices, respectively, used in Taiwan (Fig. 23.1a, b; Shü et al. 2007; Wang, 2006).

Fig. 23.1

Evergreen (a) and bald-cut (b) training systems (courtesy of Chi-cho Huang).

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Postharvest biology and technology of tropical and subtropical fruits

Fertilization Adequate fertilization is very important for high yield and quality fruits. The amount of fertilizer to apply varies depending on tree age, size, vigor, yield, soil property and growing stages. Although experience is important, soil and leaf diagnosis are recommended for adequate fertilization (Wang, 2006). Off-season production 1. Advantages Normal flowering and harvesting periods for wax apples are from March to July and from May to September in Taiwan. Both the quality and price of the fruits produced during the normal harvesting periods are not acceptable to many consumers and farmers. Off-season production for wax apples means shifting the harvesting from summer to winter. Fruit quality and price are much more favorable for fruits produced in winter than in summer because winter fruits, due to a longer growing season and fewer pests, are bigger, crispier, sweeter, juicier, seedless and thicker in flesh (Wang, 2006). Nitrogen control, water logging, root pruning, trunk injury and canopy shading are commonly used methods of off-season production. Fruit quality improvement The quality of the wax apple fruit is closely related to the season and growing region. For example, the fruit produced in summer has greater weight and volume, while the fruit produced in winter has more total soluble solids concentration and hardiness (Chen, 2006; Lo, 2008). Wax apple fruits from Linbian have the darkest red color in summer, while fruits from the Liugui and Chaozhou areas in Taiwan have the darkest red color in winter (Chen, 2006). Position on the tree also influences quality of wax apple fruits, with the fruit on the lower trunk being heaver while the upper inner fruits have the reddest color (Shü, 1999). Anthocyanin and total soluble solids concentrations (SSC) were greater in the 20 °C treated discs when a skin disc in vitro culture system was used to study the effects of temperatures on fruit quality of wax apple (Pan and Shü, 2007). Among the 18 combinations, light/20 °C/6% sucrose gave the highest SSC and anthocyanin content, while dark/20 °C/6% sucrose produced the largest diameter (Shü et al., 2001). Sucrose at various concentrations enhanced the red color of the cultured fruit discs (Liaw et al., 1999). Fruit discs from the rapid growth stage to the red stage, i.e. from 4 to 8 weeks after anthesis, had greater anthocyanin induction potential than the other stages when cultured with 6% sucrose (Chang et al., 2003). Wax apple fruits treated with N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU, a synthetic cytokinin) had greater fruit volume, weight and flesh thickness than that of the control (Shü and Yeh, 1998). Manganese sulfate sprays at 1.5% or 2.0% four times at an interval of 14 days for three weeks after petal fall increased anthocyanin concentration (Lee, 2003).

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23.1.2 Worldwide importance The wax apple has been planted as a backyard tree or only consumed either locally or domestically in some areas, but planted on a commercial scale for decades in others. In recent years wax apple fruits have been treated as an international trading commodity, and have been shipped to China, Hong Kong, Singapore, Canada and other foreign markets from Taiwan. Thailand has been sending wax apple fruits to China as well. However, before the perishable problems are solved, there is little potential for wax apple fruits to become a large international trading commodity. 23.1.3 Culinary uses, nutritional value and health benefits Wax apple fruits are primarily consumed fresh. The nutritional value of the fruit is as follows (for every 100 g): calorie 34 Kcal, water 90.6 g, crude protein 0.5 g, crude fat 0.2 g, carbohydrate 8.6 g, crude fiber 0.6 g, dietary fiber 1.0 g, ash 0.2 g, vitamin B1 0.02 mg, vitamin B2 0.03 mg, vitamin B6 0.03 mg, niacin 0.03 mg, vitamin C 6.0 mg, sodium 25 mg, potassium 340 mg, calcium 28 mg, magnesium 13 mg, phosphorus 35 mg, iron 1.5 mg, zinc 0.2 mg (http://www.doh.gov.tw/Food Analysis/). The genus of Syzygium comprises more than 500 species occurring in the tropics and subtropics. Some of the species, such as S. aromaticum, S. cordatum, S. cumini, S. jambolanum, S. jambos and S. samarangense, have been reported to have medical usage, such as diabetes or glucose tolerance impairment (Kelkar and Kaklij, 1996; Nagaraju and Rao, 1989, 1997; Prince et al., 1998; Rao and Rao, 2001; Stanely Mainzen et al., 1998; Teixeira et al., 1997; Thammanna et al., 1994; Toda et al., 2000), as well as inflammation (Chaudhuri et al., 1990; Kim et al., 1998; Muruganandan et al., 2001). They have also been used as anticonvulsant and sedative (De Lima et al., 1998), as antihypertensive (Bhargava et al., 1968), antimicrobial (Djadjo Djipa et al., 2000), against herpes virus (Kurokawa et al., 1998) and as an inhibitor of histamine release (Kim et al., 1998). An anti-inflammatory activity from Syzygium jambos leaf extracts was reported by Slowing et al. (1994a, b). The bark, leaves and roots of Syzygium cordatum are used for tuberculosis, diarrhea, stomach and respiratory complaints management in South Africa (Van Wyk et al., 1997). Syzygium alternifolium seed powder can be used for fevers and skin diseases (Thammanna et al., 1990). The antioxidant property of Syzygium cumini is well known (Prince et al., 1998) and juices of the fruits are stomachic, astringent and diuretic (Nadkarni and Nadkarni, 1976). Syzygium jambos extract has remarkable analgesic effects (Ávila-Peńa, 2007). Four cytotoxic and eight antioxidant compounds identified in the fruits (Simirgiotis et al., 2008) and four flavonoids, showing inhibitory potency on peripheral blood mononuclear cells (PBMC), were isolated from the leaves of Syzygium samarangense (Kuo et al., 2004).

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23.2

Postharvest biology and technology of tropical and subtropical fruits

Fruit development and postharvest physiology

23.2.1 Fruit growth, development and maturation The kinetics of fruit growth of the wax apple indicates single sigmoid curves. The firmness of the fruit decreases at late stages of fruit development while fruit color turns red gradually as the anthocyanin content increases. The chlorophyll concentration increases during early fruit development, then decreases and maintains a constant level until harvest, while total soluble solids of the fruit increase with fruit development. The concentrations of free amino acids and soluble protein of wax apple fruits are at their highest 20 days after full bloom, then diminished abruptly (Shü et al., 1998). 23.2.2 Respiration, ethylene production and ripening Both the fruits of wax apple (Akamine and Gao, 1979; Chiang, 2005; Hwang, 1998) and Malay apple (Basanta, 1998) are non-climacteric fruits. The respiration rate for the wax apple is steady at 65–75 ml CO2.kg−1.hr−1 and without a respiration peak at 25 °C (Liao et al., 1983). The rate reduces or increases when temperatures are reduced or increased, respectively; for example, respiration rate reduces to 15–25 ml CO2 kg−1.hr−1 at 5 °C and in summer increases to 1.5 times that of the respiration rate in winter (Horng, 1988). Wax apple fruits produce low concentration of ethylene (