Green food processing techniques : preservation, transformation and extraction 9780128154434, 0128154438, 9780128153536

Table of contents :
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1. Green Food Processing: concepts, strategies and tools 2. Ultrasound technology for processing, preservation and extraction 3. Supercritical fluid processing and extraction of food 4. High hydrostatic pressure processing of foods 5. High pressure homogenisation in food processing 6. Ohmic heating for preservation, transformation and extraction 7. Pressure hot water processing of food and natural products 8. Instant Controlled pressure drop technology in food processes 9. Membrane separation in food processing 10. Enzyme-assisted food preservation, transformation and extraction 11. Use of Magnetic Fields as a Nonthermal Technology for food processing 12. Extrusion in processing and extraction of food 13. Gas-assisted mechanical processing 14. Mechanochemical assisted processing: A novel, efficient, eco-friendly technology 15. Encapsulation Technologies for Active Food Ingredients and Food Processing 16. Essential Oils for Preserving Perishable Foods: Possibilities and Limitations 17. Food Irradiation --
From Research to Commercial Application 18. Pulsed light as new treatment to maintain physical and nutritional quality of food products 19. Pulsed Electric Field in processing of food products 20. Cold plasma in food processing<
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Green Food Processing Techniques

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Green Food Processing Techniques Preservation, Transformation and Extraction

Edited by

Farid Chemat GREEN Extraction Team, INRA, UMR408, Avignon University, Avignon, France

Eugene Vorobiev Sorbonne Universite´s, Universite´ de Technologie de Compie`gne, Laboratoire de Transformations Inte´gre´es de la Matie`re Renouvelable, Centre de Recherches de Royallieu, Compie`gne Cedex, France

Academic Press is an imprint of Elsevier 125 London Wall, London EC2Y 5AS, United Kingdom 525 B Street, Suite 1650, San Diego, CA 92101, United States 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom Copyright © 2019 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: http://www.elsevier.com/ permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-12-815353-6 For Information on all Academic Press publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Charlotte Cockle Acquisition Editor: Nina Rosa de Araujo Bandeira Editorial Project Manager: Vincent Gabrielle Production Project Manager: Nilesh Kumar Shah Cover Designer: Matthew Limbert Typeset by MPS Limited, Chennai, India

Contents

List of Contributors Biography Preface 1

2

Green food processing: concepts, strategies, and tools Francisco J. Barba, Elena Rosello´-Soto, Krystian Marszałek, ˇ c, ´ Anet Reˇzek Jambrak, Jose M. Lorenzo, Danijela Bursac´ Kovacevi Farid Chemat and Predrag Putnik 1.1 Introduction 1.2 High hydrostatic pressure 1.3 Supercritical carbon dioxide 1.4 Electrotechnologies 1.5 Laser ablation and radiofrequency 1.6 Ultrasound 1.7 Microwaves 1.8 Nanotechnology 1.9 Solar energy 1.10 Challenges with experiential methodology, theory, and statistical calculations 1.11 Strategy, challenges, and perspectives Acknowledgments References Further reading Ultrasound technology for food processing, preservation, and extraction Boutheina Khadhraoui, Anne-Sylvie Fabiano-Tixier, Philippe Robinet, Re´mi Imbert and Farid Chemat 2.1 Ultrasound: principle and influencing factors 2.1.1 Principle 2.1.2 Influencing factors 2.2 Ultrasound techniques 2.2.1 Ultrasound techniques at laboratory scale 2.2.2 Ultrasound techniques at industrial scale 2.3 Applications 2.3.1 Ultrasound in transformation and processing of food

xv xxi xxiii 1

1 2 3 5 7 7 8 9 10 11 12 13 13 21

23

23 23 27 34 34 36 37 37

vi

3

4

Contents

2.3.2 Applications of ultrasound in preservation of food 2.3.3 Applications of ultrasound in extraction 2.4 Comprehension of ultrasound-induced mechanisms 2.5 Future trends References Further reading

40 42 42 51 51 56

Supercritical fluid processing and extraction of food Renata Vardanega, Grazielle Na´thia-Neves, Priscila C. Veggi and M. Angela A. Meireles 3.1 Introduction 3.2 Principle, procedures, and influencing factors 3.2.1 Principle 3.2.2 Procedures 3.2.3 Influencing factors 3.3 Application in extraction of food ingredients 3.3.1 Extraction of essential oil 3.3.2 Extraction of carotenoids 3.3.3 Extraction of spices 3.3.4 Extraction of anthocyanins 3.4 Applications in transformation and processing of food 3.4.1 Particle formation 3.4.2 Extrusion 3.4.3 Fractionation 3.5 Applications in food preservation 3.6 Environmental impact 3.7 Upscaling and its application in industry 3.8 Future trends 3.9 Conclusion References

57

High hydrostatic pressure processing of foods Maria Tsevdou, Eleni Gogou and Petros Taoukis 4.1 Introduction 4.2 Fundamental principles of high pressure process 4.3 The effect of high pressure on food quality and safety attributes 4.3.1 The effect of high pressure on microorganisms 4.3.2 The effect of high pressure on enzymes 4.3.3 The effect of high pressure on nutritional characteristics of foods 4.3.4 The effect of high pressure on the shelf life of food products 4.4 High pressure technology in combination with other processes and hurdles 4.4.1 High pressure
assisted extraction

57 58 58 59 62 64 65 66 67 68 68 68 69 69 70 71 73 77 78 78 87 87 88 91 91 97 102 108 110 110

Contents

vii

4.4.2

Application of high pressure in combination with antimicrobials and plant extracts 4.4.3 Application of high pressure in combination with osmotic dehydration 4.4.4 Application of high pressure in combination with enzyme pretreatment 4.5 Industrial applications of high pressure 4.6 High pressure process design and evaluation 4.6.1 High pressure processing impact evaluation 4.6.2 Development of pressure
temperature
time indicators 4.7 Economical and environmental aspects of high pressure application in the food industry 4.7.1 Economical aspects of high pressure 4.7.2 Environmental aspects of high pressure References 5

6

High-pressure homogenization in food processing Dominique Chevalier-Lucia and Laetitia Picart-Palmade 5.1 Introduction 5.2 Dynamic high pressure principle and equipment 5.3 High pressure homogenization processing as greener extraction processing 5.4 Dynamic high pressure processing as greener submicron emulsion processing 5.5 Dynamic high pressure processing as greener preservation processing 5.6 Conclusion References Ohmic heating for preservation, transformation, and extraction Rui M. Rodrigues, Zlatina Genisheva, Cristina M.R. Rocha, Jose´ A. Teixeira, Anto´nio A. Vicente and Ricardo N. Pereira 6.1 Introduction 6.1.1 Fundamentals of ohmic heating 6.1.2 Present status: commercial and novel applications 6.2 Food processing and preservation 6.2.1 Thermal processing of foods 6.2.2 Nonthermal effects: cellular matrices, microorganisms, and enzymes 6.2.3 Transformation of macromolecules 6.3 Extraction of biocompounds 6.3.1 Electroheating 6.3.2 Nonthermal effects in extraction processes 6.3.3 Combining ohmic heating with other extraction techniques

112 112 112 113 114 118 119 122 122 123 124 139 139 141 144 146 149 152 153 159

159 159 162 164 164 166 173 175 176 178 179

viii

7

8

9

Contents

6.4 Future perspectives Acknowledgments References

182 182 183

Pressure hot water processing of food and natural products Merichel Plaza, Marı´a Castro-Puyana and Marı´a Luisa Marina 7.1 Introduction 7.2 Fundamentals of pressurized hot water extraction 7.3 Instrumentation 7.4 Applications in the extraction of food ingredients from foods and natural products 7.5 Hydrolysis reactions during pressurized hot water extraction 7.6 Food quality and safety using pressurized hot water extraction 7.7 Environmental impact 7.8 Conclusions and future trends Acknowledgments References

193

Instant controlled pressure drop as new intensification ways for vegetal oil extraction Cherif Jablaoui, Amal Zeaiter, Kamel Bouallegue, Bassam Jemoussi, Colette Besombes, Tamara Allaf and Karim Allaf 8.1 Introduction 8.2 Phenomenological analysis and intensification ways of solvent extraction process 8.3 Material and method 8.3.1 Raw material 8.3.2 Phenomenological approach of solvent extraction procedure 8.3.3 Main intensification ways 8.3.4 Assessments and characterization 8.4 Results and discussion 8.4.1 Oil yields issued from differently assisted operations of solvent extraction 8.4.2 Kinetics of vegetal oil extraction 8.4.3 Impact on oil quality 8.4.4 Specific new desolventation ways 8.5 Conclusion References Membrane separation in food processing Wafa Guiga and Marie-Laure Lameloise 9.1 Overview of membrane separation processes in food industry 9.1.1 Pressure-driven membrane technologies 9.1.2 Electrically driven membrane technology 9.1.3 Vapor pressure gradient membranes

193 194 197 199 208 209 213 214 215 215

221

221 221 224 224 225 228 231 232 232 233 238 242 243 243 245 245 245 248 250

Contents

9.2

10

11

ix

Theoretical aspects in membrane separation 9.2.1 Key parameters in membrane separation 9.2.2 Transport theory 9.2.3 Concentration polarization 9.2.4 Membrane fouling 9.3 Membrane materials and modules 9.3.1 Materials 9.3.2 Module geometries 9.3.3 Innovations in material manufacturing 9.3.4 Configurations 9.3.5 Separation process performances enhancement techniques 9.3.6 Membrane cleaning 9.4 Membrane applications in food processing 9.4.1 Contribution and interest of membranes in the processes of food industry 9.4.2 Purification 9.4.3 Concentration/extraction 9.4.4 Separation and integrated processes 9.4.5 Effluent treatment 9.5 Conclusion References

250 250 252 254 256 257 257 258 260 261

Extrusion Virginie Vandenbossche, Laure Candy, Philippe Evon, Antoine Rouilly and Pierre-Yves Pontalier 10.1 Introduction 10.1.1 Extrusion 10.1.2 Twin-screw extruder 10.2 Extrusion cooking 10.2.1 Process 10.2.2 Flours 10.2.3 Proteins 10.2.4 Other applications 10.2.5 Mechanical fractionation 10.3 Expression 10.4 Extraction 10.4.1 Lignocellulosic residues 10.4.2 Green plants 10.4.3 Oil extraction References Further reading

289

Gas-assisted oil expression from oilseeds Houcine Mhemdi and Eugene Vorobiev 11.1 Introduction

264 267 268 268 270 273 275 277 281 282

289 289 290 293 293 293 294 295 296 297 301 302 306 308 311 314 315 315

x

Contents

11.2

Conventional extraction methods of seed and nut oils 11.2.1 Mechanical expression (pressing) 11.2.2 Solvent extraction 11.2.3 Supercritical fluid extraction 11.3 Gas-assisted mechanical expression 11.3.1 Fundamentals of gas-assisted mechanical expression technology 11.3.2 Applications of gas-assisted mechanical expression technology 11.3.3 Advantages and limitations of gas-assisted mechanical expression technology 11.4 Conclusion References 12

13

Encapsulation technologies for polyphenol-loaded microparticles in food industry ´ Danijel D. Milinci ˇ c, ´ Mirjana B. Peˇsic, ´ Duˇsanka A. Popovic, ˇ ´ Zivoslav Ana M. Kaluˇsevic, Lj. Teˇsic´ and Viktor A. Nedovic´ 12.1 Introduction 12.2 Matrices for polyphenol-loaded microparticles production and their application in food 12.2.1 Polysaccharide-based carrier for phenolic compounds 12.2.2 Protein-based carrier for phenolic compounds 12.2.3 Lipid-based carrier for phenolic compounds 12.3 Techniques for polyphenol-loaded microparticles production and applications 12.3.1 Spray-drying 12.3.2 Freeze-drying 12.3.3 Fluid bead coating 12.3.4 Extrusion methods 12.3.5 Emulsification process 12.3.6 Complex coacervation 12.3.7 Encapsulation in liposomes 12.3.8 Molecular inclusion 12.4 Conclusion Acknowledgment References Further reading Essential oils for preserving foods Chahrazed Boutekedjiret, Amina Hellal, Anne-Sylvie Fabiano-Tixier, Maryline Abert-Vian and Farid Chemat 13.1 Extraction processes of essential oils: from tradition to innovation 13.1.1 Essential oils: definition, localization, and composition 13.1.2 Essential oils: recovery methods

317 317 318 318 319 319 321 328 330 330

335

335 336 337 346 348 349 349 351 351 352 353 354 354 355 355 356 356 367 369

369 369 371

Contents

13.1.3 Devices of essential oils extraction 13.1.4 Innovative techniques 13.2 Essential oils as antimicrobials 13.2.1 Applications in meat-based foodstuffs and seafood products 13.2.2 Applications in dairy products 13.2.3 Applications in vegetables and fruits 13.2.4 Applications to cereal products 13.3 Essential oils as antioxidant agents in food products 13.3.1 Chemical lipid oxidation 13.3.2 Antioxidant activity 13.3.3 Inhibition of lipid autooxidation 13.3.4 Radical-scavenging tests 13.4 Future trends References 14

15

Pulsed light as a new treatment to maintain physical and nutritional quality of food Tatiana Koutchma 14.1 Introduction 14.2 Mode of action of pulsed and pulsed ultraviolet light 14.3 Advantages and disadvantages of high-intensity light pulses 14.4 Factors affecting interaction between high-intensity pulses and materials 14.5 Microbial inactivation mechanism 14.5.1 Photochemical effect 14.5.2 Photothermal effect 14.5.3 Photophysical effect 14.6 High-intensity light pulses for food preservation 14.7 Pulsed light effects on quality, enzymes, and functionality 14.8 Pulsed light sources and equipment 14.9 Conclusion References Pulsed electric field in green processing and preservation of food products Eugene Vorobiev and Nikolai Lebovka 15.1 Introduction 15.2 Impact of pulsed electric field on cell tissue and biosuspensions 15.3 Food processing with pulsed electric field 15.3.1 Upstream processing 15.3.2 Downstream processing 15.4 Conclusion References

xi

373 374 375 375 377 377 378 378 379 379 381 384 386 387

391 391 391 393 394 394 394 395 395 395 396 400 400 401

403 403 405 406 410 413 426 426

xii

16

17

Contents

Cold plasma for sustainable food production and processing N.N. Misra and M.S. Roopesh 16.1 Introduction 16.2 Cold plasma fundamentals 16.2.1 Plasma sources 16.2.2 Plasma chemistry 16.3 Antimicrobial action of plasma species 16.4 In-package cold plasma: a dry, green, and resource-efficient process 16.5 Cold plasma for water treatment 16.6 Cold plasma for sustainable food production 16.7 Energy efficiency and process cost 16.8 Conclusion References

431

Microwave technology for food applications Alice Angoy, Syle`ne Brianceau, Franc¸ois Chabrier, Pascal Ginisty, Wahbi Jomaa, Jean-Franc¸ois Rochas, Alain Sommier and Marc Valat 17.1 Introduction: approach adopted in this chapter 17.2 Principle, influencing factors, induced mechanisms 17.2.1 Introduction 17.2.2 Some theoretical aspects of microwaves 17.2.3 An insight into the principles of dielectric heating 17.2.4 Heat and mass transfer in food processing 17.2.5 Associated metrology 17.2.6 Pros and cons of dielectric heating in food processing 17.3 Techniques at laboratory and industrial scale 17.4 Pre- and postprocessing and coupling 17.4.1 Pretreatment 17.4.2 Posttreatment 17.4.3 Coupling 17.5 Applications in transformation, food processing, and preservation 17.5.1 Pasteurization
sterilization 17.5.2 Drying 17.5.3 Microwave with convective drying 17.5.4 Microwave vacuum drying 17.5.5 Thawing and tempering 17.5.6 Microwave frying 17.6 Applications in extraction of food ingredients 17.6.1 Extraction principle 17.6.2 Microwave-assisted extraction principles 17.6.3 Microwave-assisted extraction techniques

455

431 433 434 435 437 438 440 442 445 446 446

455 456 456 456 458 461 462 464 464 464 464 466 466 467 467 469 472 473 473 474 475 475 476 477

Contents

17.7

Environmental impact 17.7.1 Introduction 17.7.2 Goal and scope 17.8 Regulation and security 17.8.1 Hazard analysis and critical control points approach 17.9 Upscaling and its applications in industry 17.10 Future trends Acknowledgments References Further reading 18

Solar as sustainable energy for processing, preservation, and extraction Laila Mandi, Soukaina Hilali, Farid Chemat and Ali Idlimam 18.1 Instrumentation 18.1.1 Thermal solar energy 18.1.2 Photovoltaic energy 18.2 Solar energy in food process engineering 18.3 Solar extraction 18.4 Solar cooking 18.5 Solar drying systems 18.6 Solar pasteurization 18.7 Environmental impacts using solar energy 18.8 Hazard analysis and critical control points and hazard and operability considerations using solar energy References Further reading

Author Index Subject Index

xiii

481 481 483 486 487 489 489 491 491 498

499 499 499 499 500 500 502 506 507 508 508 509 511 513 545

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List of Contributors

Maryline Abert-Vian Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France Karim Allaf Laboratory of Engineering Science for Environment LaSIE—UMRCNRS 7356, University of La Rochelle, La Rochelle, France Tamara Allaf ABCAR-DIC Process, La Rochelle, France Alice Angoy IFTS, Agen, France Francisco J. Barba Nutrition and Food Science Area, Preventive Medicine and Public Health, Food Sciences, Toxicology and Forensic Medicine Department, Faculty of Pharmacy, University of Valencia, Vale`ncia, Spain Colette Besombes Laboratory of Engineering Science for Environment LaSIE— UMR-CNRS 7356, University of La Rochelle, La Rochelle, France Kamel Bouallegue Laboratory of Engineering Science for Environment LaSIE— UMR-CNRS 7356, University of La Rochelle, La Rochelle, France; University of Gabes, Gabe`s, Tunisia Chahrazed Boutekedjiret Laboratory of Science and Technology of Environment, Ecole Nationale Polytechnique, Alger, Alge´rie Syle`ne Brianceau Agrotec, Agen, France Laure Candy Laboratory of Agro-Industrial Chemistry, Toulouse University, INRA, INPT, Toulouse, France Marı´a Castro-Puyana Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, University of Alcala´, Alcala´ de Henares, Madrid, Spain Franc¸ois Chabrier Agrotec, Agen, France Farid Chemat Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France

xvi

List of Contributors

Dominique Chevalier-Lucia IATE, University of Montpellier, CIRAD, INRA, Montpellier SupAgro, Montpellier, France Philippe Evon Laboratory of Agro-Industrial Chemistry, Toulouse University, INRA, INPT, Toulouse, France Anne-Sylvie Fabiano-Tixier Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France Zlatina Genisheva CEB
Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal Pascal Ginisty IFTS, Agen, France Eleni Gogou Laboratory of Food Chemistry & Technology, School of Chemical Engineering, National Technical University of Athens, Athens, Greece Wafa Guiga Cnam, UMR 1145 Food Process Engineering, Paris, France Amina Hellal Laboratory of Science and Technology of Environment, Ecole Nationale Polytechnique, Alger, Alge´rie Soukaina Hilali Faculty of Sciences Semlalia, University Cadi Ayyad, Marrakech, Morocco Ali Idlimam Laboratory of Solar Energy and Medecinal Plants, Teacher’s Training College, Marrakech, Morocco Re´mi Imbert Laboratoires Arkopharma, Laboratoire d’e´tude des substances naturelles, Carros, France Cherif Jablaoui Laboratory of Engineering Science for Environment LaSIE— UMR-CNRS 7356, University of La Rochelle, La Rochelle, France; National Agronomic Institute of Tunisia (INAT), University of Carthage, Tunis, Tunisia Anet Reˇzek Jambrak Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia Bassam Jemoussi Laboratory of Supramolecular Chemistry ISEFC, University Virtual-Tunisia, Tunis, Tunisia Wahbi Jomaa Bordeaux University, Bordeaux, France Ana M. Kaluˇsevi´c Department of Food Technology and Biochemistry, Faculty of Agriculture, University of Belgrade, Belgrade, Serbia; Institute of Meat Hygiene and Technology, Belgrade, Serbia

List of Contributors

xvii

Boutheina Khadhraoui Laboratoires Arkopharma, Laboratoire d’e´tude des substances naturelles, Carros, France; Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France Tatiana Koutchma Agriculture and Agri-Food Canada (AAFC), Guelph Research and Development Center, Guelph, ON, Canada Danijela Bursa´c Kovaˇcevi´c Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia Marie-Laure Lameloise AgroParisTech, UMR 1145 Food Process Engineering, INRA, Universite´ Paris-Saclay, Massy, France Nikolai Lebovka Sorbonne Universities, University of Technology of Compiegne, Laboratory TIMR, Research Center of Royallieu, Compiegne, France; Institute of Biocolloidal Chemistry Named After F.D. Ovcharenko, NAS of Ukraine, Kyiv, Ukraine Jose M. Lorenzo Meat Technology Center of Galicia, Parque Tecnolo´gico de Galicia, San Cibrao das Vin˜as, Ourense, Spain Laila Mandi National Center for Studies and Research on Water and Energy, University Cadi Ayyad, Marrakech, Morocco Marı´a Luisa Marina Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, University of Alcala´, Alcala´ de Henares, Madrid, Spain Krystian Marszałek Prof. Wacław Da˛browski Institute of Agricultural and Food Biotechnology, Department of Fruit and Vegetable Product Technology, Warsaw, Poland M. Angela A. Meireles LASEFI/DEA/FEA (School of Food Engineering), UNICAMP (University of Campinas), Campinas, Brazil Houcine Mhemdi TIMR Laboratory (UTC/ESCOM, EA 4297, TIMR), Research Center of Royallieu, Compiegne, France Danijel D. Milinˇci´c Department of Food Technology and Biochemistry, Faculty of Agriculture, University of Belgrade, Belgrade, Serbia N.N. Misra Department of Food Science & Human Nutrition, Iowa State University, Ames, IA, United States Grazielle Na´thia-Neves LASEFI/DEA/FEA (School of Food Engineering), UNICAMP (University of Campinas), Campinas, Brazil

xviii

List of Contributors

Viktor A. Nedovi´c Department of Food Technology and Biochemistry, Faculty of Agriculture, University of Belgrade, Belgrade, Serbia Ricardo N. Pereira CEB
Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal Mirjana B. Peˇsi´c Department of Food Technology and Biochemistry, Faculty of Agriculture, University of Belgrade, Belgrade, Serbia Laetitia Picart-Palmade IATE, University of Montpellier, CIRAD, INRA, Montpellier SupAgro, Montpellier, France Merichel Plaza Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, University of Alcala´, Alcala´ de Henares, Madrid, Spain Pierre-Yves Pontalier Laboratory of Agro-Industrial Chemistry, University, INRA, INPT, Toulouse, France

Toulouse

Duˇsanka A. Popovi´c Department of Food Technology and Biochemistry, Faculty of Agriculture, University of Belgrade, Belgrade, Serbia Predrag Putnik Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia Philippe Robinet Laboratoires Arkopharma, Laboratoire d’e´tude des substances naturelles, Carros, France Cristina M.R. Rocha CEB
Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal Jean-Franc¸ois Rochas Waves Concept, Lyon, France Rui M. Rodrigues CEB
Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal M.S. Roopesh Department of Agricultural, Food & Nutritional Science, University of Alberta, Edmonton, AB, Canada Elena Rosello´-Soto Nutrition and Food Science Area, Preventive Medicine and Public Health, Food Sciences, Toxicology and Forensic Medicine Department, Faculty of Pharmacy, University of Valencia, Vale`ncia, Spain Antoine Rouilly Laboratory of Agro-Industrial Chemistry, Toulouse University, INRA, INPT, Toulouse, France

List of Contributors

xix

Alain Sommier I2M, Bordeaux, France Petros Taoukis Laboratory of Food Chemistry & Technology, School of Chemical Engineering, National Technical University of Athens, Athens, Greece Jose´ A. Teixeira CEB
Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal ˇ Zivoslav Lj. Teˇsi´c Faculty of Chemistry, University of Belgrade, Belgrade, Serbia Maria Tsevdou Laboratory of Food Chemistry & Technology, School of Chemical Engineering, National Technical University of Athens, Athens, Greece Marc Valat Bordeaux University, Bordeaux, France Virginie Vandenbossche Laboratory of Agro-Industrial Chemistry, Toulouse University, INRA, INPT, Toulouse, France Renata Vardanega LASEFI/DEA/FEA (School of Food Engineering), UNICAMP (University of Campinas), Campinas, Brazil Priscila C. Veggi School of Chemical Engineering, Federal University of Sa˜o Paulo (UNIFESP), Diadema, Brazil Anto´nio A. Vicente CEB
Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal Eugene Vorobiev Sorbonne Universities, University of Technology of Compiegne, Laboratory TIMR, Research Center of Royallieu, Compiegne, France; TIMR Laboratory (UTC/ESCOM, EA 4297, TIMR), Research Center of Royallieu, Compiegne, France Amal Zeaiter Laboratory of Engineering Science for Environment LaSIE—UMRCNRS 7356, University of La Rochelle, La Rochelle, France; Doctoral School of Science and Technology, Lebanese University, Beirut, Lebanon

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Biography

Farid Chemat is a full professor of Chemistry at Avignon University, director of GREEN Extraction Team (innovative techniques, alternative solvents, and original procedures for green extraction of natural products), codirector of ORTESA LabCom research unit Naturex-AU, and scientific coordinator of “France EcoExtraction” dealing with dissemination of research and education on green extraction technologies. He received his engineer diploma from the University of Blida, Algeria (1990) and his PhD degree (1994) in process engineering from the Institut National Polytechnique of Toulouse, France. After periods of postdoctoral research work with industries (1995
97), he spent 2 years (1997
99) at the University of Wageningen, The Netherlands. In 1999 he moved to the University of La Re´union, France DOM and since 2006 holds the position of professor of Food Chemistry at the University of Avignon, France. His research activity is documented by more than 200 scientific peer-reviewed papers, and about the same number of conferences and communications to scientific and industrial meetings, 10 books, 40 book chapters, and 10 patents. His main research interests have focused on innovative and sustainable extraction and processing techniques. He is nominated as High Cited Researcher (HCR) in 2018. Eugene Vorobiev is a full professor of Chemical Engineering and a head of the Laboratory for Agro-Industrial Technologies at the Compiegne University of Technology, France. He received his PhD degree in Food Engineering (1980, Ukraine) and his Dr. Habil in Chemical Engineering (1997, France). His main research interests are focused on mass transfer phenomena, theory and practice of solid/liquid separation, and innovative food technologies (especially electrotechnologies). He has published more than 300 scientific peer-reviewed papers; he is the author of 19 patents, and several books and book chapters. He is a member of editorial board in several international journals (“Separation and Purification Technology,” “Innovative Food Science and Emerging Technologies,” “Food Engineering Reviews,” and “Agricultural and Food Chemistry”). He was awarded by Gold Medal of the Filtration Society (2001) and he is a Laureate of the Price for the innovative technique for the environment (Ademe, 2008, 2014). He was a chairman of several international conferences.

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Preface

Food processing even preservation, transformation, or extraction is a dynamically developing area in fundamental and applied research even in academia and industry, and this takes an important place in manufacturing processes. Challenges and drivers launched by the environment protection, competitiveness of the globalized market, and more recently as requests by consumers and society strongly require innovations that break away from the past rather than simple continuity. Green Food Processing could be a new concept to meet the challenges for the future of humanity on this strategic 21st century, to protect both the environment and consumers, and in the meantime, enhance competition of industries to be more ecologic, economic, and innovative. This green approach should be the result of a whole chain of values in both senses of the term: economic and responsible, starting from the production and harvesting of food raw materials, processes of preservation, transformation, and extraction together with formulation and marketing. Green Food Processing could respond to these challenges of this 21st century for enhancing shelf life and nutritional quality of food products, to reduce energy and unit operations for processing, eliminating wastes and byproducts, reduction of water use in harvesting, washing and processing, use of naturally derived ingredients, the need of standardization, and more important, eliminating hunger, food insecurity, and malnutrition worldwide. This book was prepared by a team of reputed international researchers and professionals composed of chemists, biochemists, chemical engineers, physicians, and food technologists with an objective to provide an actual picture of current knowledge on Green Food Processing techniques used in research academic laboratories and in industrial scale. It is aimed for professional from industry, academicians engaged into food engineering, and graduate level students. We wish to thank sincerely all authors who have collaborated in the writing this book. We hope to express them our scientific gratitude for agreeing to devote their competence and time to ensure the success of this book. We are totally convinced that this book is the starting point of new discipline and for future collaborations in Green Food Processing between research, industry, and education. Farid Chemat1 and Eugene Vorobiev2 1

2

Avignon University, Avignon, France, University of Technology of Compie`gne, Compie`gne, France

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Green food processing: concepts, strategies, and tools

1

Francisco J. Barba1, Elena Rosello´-Soto1, Krystian Marszałek2, ˇ c´ 3, Anet Rezek ˇ Jambrak3, Jose M. Lorenzo4, Danijela Bursac´ Kovacevi 5 3 Farid Chemat and Predrag Putnik 1 Nutrition and Food Science Area, Preventive Medicine and Public Health, Food Sciences, Toxicology and Forensic Medicine Department, Faculty of Pharmacy, University of Valencia, Vale`ncia, Spain, 2Prof. Wacław Da˛browski Institute of Agricultural and Food Biotechnology, Department of Fruit and Vegetable Product Technology, Warsaw, Poland, 3 Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia, 4 Meat Technology Center of Galicia, Parque Tecnolo´gico de Galicia, San Cibrao das Vin˜as, Ourense, Spain, 5Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France

1.1

Introduction

Food processing is among the different areas relevant to GREEN chemistry, particularly interesting for processes of preservation, transformation, bio-refining, and extraction (Putnik, Lorenzo, et al., 2018). GREEN concepts can be applied to various raw materials for food production, including fresh fruits (Lorenzo et al., 2018; Putnik, Bursa´c Kovaˇcevi´c, Herceg, Pavkov, et al., 2017), vegetables (Montesano, Rocchetti, Putnik, & Lucini, 2018), medicinal and aromatic plants (Vincekovi´c et al., 2017), and food industrial by-products (Putnik, Bursa´c Kovaˇcevi´c, Reˇzek Jambrak, et al., 2017). Judging by the literature, this seems to be one of the most promising areas, from both academic and industrial point of view (Bursa´c Kovaˇcevi´c, Barba, et al., 2018; ˇ Putnik, Barba, Spani´ c, et al., 2017). Food processing of fruits and vegetables (Putnik, Bursa´c Kovaˇcevi´c, Herceg, Roohinejad, et al., 2017; Repaji´c et al., 2015), fats and oils (Domı´nguez et al., 2018), sugar, dairies (Musina et al., 2017), meats (Domı´nguez et al., 2017), coffee and cocoa, meals, and flours affects a complex mixture of nutrients and bioactive compounds, such as carbohydrates, proteins, lipids, minerals, vitamins, and polyphenols. This also involves other compounds, such as fibers (Cukelj et al., 2016), aromas, pigments, antioxidants, and organic and mineral compounds which are involved with production. Before food products can be consumed, they have to be processed (even at minimal levels) and preserved to avoid microbial contamination and to ensure extended shelf life (Putnik, Bursa´c Kovaˇcevi´c, Herceg, & Levaj, 2017c). Moreover, it is of particular

Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00001-X © 2019 Elsevier Inc. All rights reserved.

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Green Food Processing Techniques

interest to reuse the wastes and by-products from agri-food industry, in order to obtain high-added value compounds (Fidelis et al., 2018). Later they can be used as potential food additives and/or nutraceuticals, among other applications (Putnik, Lorenzo, et al., 2018). For instance, tremendous efforts have been made to develop and apply new sustainable “green and innovative” techniques in processing, pasteurization, and extraction (Barba et al., 2017). In comparison to conventional ones, they involve reduced processing time, less solvent and energy consumption, as well as reduced emissions of CO2 for diminishing the carbon footprint (Misra, Koubaa, et al., 2017). Among the most common, innovative green and nonthermal technologies are high-pressure processing (HPP), supercritical carbon dioxide (SCCD), and electrotechnologies, for example, pulsed electric fields and high-voltage electrical discharges (HVED) (Bursa´c Kovaˇcevi´c, Maras, et al., 2018; Poojary et al., 2017). Solar food processing is another emerging technology providing good quality foods at low or no additional fuel costs (Eswara & Ramakrishnarao, 2012). Nonconventional energy sources, such as microwaves and ultrasound, have been also recognized as green processing intensification methods for various purposes in food processing (Djekic et al., 2018). Moreover, nanotechnology, laser ablation, and radiofrequency have been considered as attractive “green” alternatives, which can be successfully used in the food sector (Chellaram et al., 2014; Cheng et al., 2017; Salazar, Garcia, Lagunas-Solar, Pan, & Cullor, 2018; Singh et al., 2017).

1.2

High hydrostatic pressure

In this line, high hydrostatic pressure (HHP) also known as “high-pressure processing” consists of subjecting the materials to pressures as high as 1400 MPa, although 600 MPa is the maximum pressure used at industrial level. This environment-friendly technology has been identified as an alternative to thermal processing that could extend the shelf life and improve the safety of foods. Another advantage of HPP applications over thermal treatments implies minimal changes of fresh food characteristics like flavor, aroma, nutritional, and bioactive value (Huang, Wu, Lu, Shyu, & Wang, 2017). Over the past few years, the number of industries that uses HPP to pasteurize liquid foods has grown considerably. Usually, employed pressures are between 300 and 600 MPa, exerted for 1
15 minutes at room temperature to achieve this process (Barba, Esteve, & Frı´gola, 2012). Nowadays, there are more than 300 sets of HPP equipment that have been operating for mass production worldwide but mostly in North America (54%), Europe (25%), and Asia (12%) (Huang et al., 2017). Moreover, the use of HPP combined with high temperature to inactivate bacterial spores has been proposed by several authors (Borda, Bleoanca, & Turtoi, 2013). In addition, different applications for this technology are currently being investigated, such as reducing the allergenicity and contaminants in food products, inactivating enzymes present in fruits and/or vegetables, and valorizing food matrices

Green food processing: concepts, strategies, and tools

3

¨ nu¨r et al., 2018; Putnik, Bursa´c (Barba, Terefe, Buckow, Knorr, & Orlien, 2015; O Kovaˇcevi´c, et al., 2018; Rastogi, Raghavarao, Balasubramaniam, Niranjan, & Knorr, 2007). In addition to that, HPP is useful even for engineering and manufacturing food-grade emulsions (Gharibzahedi et al., 2018). This technology is useful for both fresh products and food waste and by-products.

1.3

Supercritical carbon dioxide

SCCD, also known as high-pressure carbon dioxide or dense phase carbon dioxide, is a technique commonly used in food technology. It is mainly utilized for extraction (Fig. 1.1), microbial and enzyme inactivation, or even for drying. Batch and continuous systems are the two main SCCD options, which are already available. In batch system, often used for food preservation, samples are placed inside a thermostatted pressure chamber, while carbon dioxide is pumped at optimal pressure into the chamber for a specified time. In continuous system, the carbon dioxide flows through the chamber at elevated pressure and temperature. This system is used for extraction and drying operations. From an economical point of view, recirculation of carbon dioxide as well as application of special moisture absorber for drying processes is required. SCCD is usually tested for preservation of liquid foods, such as fruit juices, beer, and milk (Damar & Balaban, 2006). Furthermore, in the food industry it is used for decaffeination of coffee, removal of alcohol from wine and beer, decreasing the amount of fat in meat, enrichment with lipid-soluble vitamins, and production of spice extracts by “green” extractions (Abd Hamid, Ismail, & Abd Rahman, 2018; Hashemi et al., 2018; Wo´zniak, Marszałek, Ska˛pska, & Je˛drzejczak, 2017). The first application of SCCD has been implemented in large scale for extraction processes. Carbon dioxide (above the critical point of 31.1 C and 7.38 MPa) is

Figure 1.1 Examples of supercritical carbon dioxide equipment.

4

Green Food Processing Techniques

characterized by high diffusion coefficients and very low viscosity. From this point of view, rates of the extraction can be accelerated in comparison to traditional extraction with solvents. The density of carbon dioxide can be altered by the temperature and pressure changes. Many properties of carbon dioxide are correlated with the density; therefore the selectivity of extraction can be achieved by application of the proper process parameters (Wo´zniak, Marszałek, & Ska˛pska, 2016). Food preservation under SCCD gives promising results which can be used in food industry (Ferrentino & Spilimbergo, 2011). The combined effect of pressure, heating with modification of product pH, is used for physical disruption of microbial cells, extraction of intracellular compounds, and structural changes in tissue enzymes. The most often used parameters for SCCD generally include pressures below 60 MPa, treatment time no longer than 30 minutes, and temperatures below 65 C. An important advantage of this technique is the possibility of microorganism and tissue enzymes inactivation under pressures even lower than 10 times of typical HPP treatment (Marszałek, Ska˛pska, Wo´zniak, & Sokołowska, 2015; Marszałek, Wo´zniak, Kruszewski, & Ska˛pska, 2017). It was reported that the initial pH in treated products has the biggest influence on microbial cell destruction (Chen et al., 2010), whereas it was noted that SCCD treatment was effective in killing vegetative forms of pathogenic and spoilage bacteria, yeasts, and molds in different kinds of products (Damar & Balaban, 2006). The effectiveness of microbial as well as enzymes inactivation is highly dependent on the matrix, treatment conditions, kind of microorganisms, enzymes, and type of the system used. The microbial inactivation achieved under SCCD ranged from 2 to 12 logs, using pressures below 50 MPa and temperatures between 5 C and 60 C. The mechanism of fruit and vegetable tissue enzymes’ inactivation is still unclear. The most possible hypothesis is that process parameters influence conformational changes of the enzymes that are not native to raw materials’ pH (Marszałek et al., 2018). The impact of SCCD on the activity of tissue enzymes in strawberry, apple, carrot, celery, and beetroot products has been reported (Chen et al., 2010; Marszałek, Kruszewski, Wo´zniak, & Ska˛pska, 2017; Marszałek, Krzy˙zanowska, Wo´zniak, & Ska˛pska, 2016, 2017). Different research groups tested the influence of SCCD technique at pressures up to 60 MPa, time up to 30 minutes, and temperature up to 65 C. It was proved that the inhibition of polyphenol oxidase could be possible at the temperatures of 45 C and 65 C and pressures of 10
60 MPa even for 10-minute treatments in fruit products. The total inhibition of the same enzymes in vegetable products has not been achieved at similar process parameters; however, 70% inactivation was observed. This phenomenon could be attributed to the decrease of natural pH of treated product, due to carbon dioxide dissolution (Marszałek et al., 2016). In the last two decades, supercritical drying has attracted growing interests for its increasing applications in food technology. Supercritical drying is also well known as supercritical organic solvent drying, supercritical gas drying, supercritical mixture solvent drying, supercritical gas extraction drying, and supercritical fluid
assisted spray drying (Zheng et al., 2011). Supercritical drying is generally dependent on the thickness and weight of the sample, and these factors significantly

Green food processing: concepts, strategies, and tools

5

influence the drying kinetics. Moreover, plant tissues are affected by high variability that can also affect the process conditions required for processing. This includes pressures and treatment times needed to achieve a satisfactory drying process kinetic. Monitoring of the product moisture is the most important factor during drying, but the nature of SCCD allows measuring of the weight loss between the beginning and the end of the drying process. Using offline measurements as indicator of drying can be inconvenient since it can lead to waste of product and therefore to an increase of entire cost of the process. The online analysis of product parameters, such as water removal, inside a high-pressure vessel is very challenging (Michelino et al., 2017).

1.4

Electrotechnologies

Electrotechnologies such as pulsed electric fields and HVED have attracted the attention of both researchers and the agri-food industries. Being delineated as a potential tool to exploit the waste generated during the food production process, electrotechnologies are possible to be used on diverse collection of the products and stages of production, for example, from their initial production to the final use by the consumer (Giacometti et al., 2018). By means of the electrical pulses, it is possible to reuse the by-products generated during the processing of the food, as well as the products, which are not finally consumed and are wasted in the supermarkets. The same is possible to the value products generated, for example, after harvesting of grapes or oil crops, among other products (Lorenzo et al., 2018). Electric pulse generators used at very high electric fields can allow the inactivation of microorganisms in liquid foods (Putnik, Barba, Lorenzo, et al., 2017), while low electric fields can be used for the extraction of compounds (Gabri´c et al., 2018; Koubaa et al., 2018). Such molecules have value from the nutritional point of view (e.g., bioactive compounds and proteins) and can be used for different purposes. Among many, they are useful as food additives and/or nutraceuticals since this process allows the selective extraction of intracellular compounds (Granato, Nunes, & Barba, 2017; Pue´rtolas, Koubaa, & Barba, 2016). HVED is an advantageous and promising green technique. The main advantages of HVED are low treatment temperature and preservation of thermolabile food compounds. Historically, HVED has been used to reduce microbial contamination of food (Knorr et al., 2011). Further, it is possible to apply it in initial stages to the waste recovery process and during the pasteurization of the initial matrix (Bursa´c Kovaˇcevi´c et al., 2016; Herceg et al., 2016). This technology has the industrial upscale potential, but only if it is possible to lower the high implementation costs since it is currently quite expensive. This technology is based on the physiochemical process that occurs when electrical discharges encounter water, causing consequential release of energy, which fragments the cellular tissues (Boussetta & Vorobiev, 2014). High-voltage discharge in liquids results with a rupture of the cellular tissues, which greatly

6

Green Food Processing Techniques

improves extractions of valuable components from plant material as well as various by-products and causes electroporation. It means that the formation of pores occurs due to electromechanical compression of membrane. The efficiency of this process relies on the fact that large amounts of energy are released in the treated medium in the form of a plasma discharge generated between the submerged electrodes. Example of prototype device is shown in Fig. 1.2, which is used for generating HVED and constructed by Impel group. HVED can be used for different applications, such as elimination of organic chemical impurities from water, and as previously mentioned for electric pulses, for the extraction of bioactive compounds present in different food matrices. Most of the HVED extractions today were carried out on soybeans, fennel, potatoes, stevia, flax seeds, papaya, and polyphenols from the grape skin (Misra, Martynenko, et al., 2017; Putnik, Bursa´c Kovaˇcevi´c, Reˇzek Jambrak, et al., 2017; Vincekovi´c et al., 2017).

Figure 1.2 High-voltage electrical discharge generator (IMP-SSPG-1200, Impel group, Zagreb, Croatia).

Green food processing: concepts, strategies, and tools

7

Some of the researches are related to the extraction of polyphenols, proteins, and oils from plant sources. The use of “green” solvents is driven by the trends that are focused on finding solutions that will minimize the use of toxic chemicals, as selection for usage of the solvents is directed toward intensifying the process of extraction and cost-effective production of high-quality extracts. Besides electrotechnologies (Mari´c et al., 2018; Pateiro et al., 2018; Putnik, Bursa´c Kovaˇcevi´c, Reˇzek Jambrak, et al., 2017), others attracting much interest as “green” processing alternatives are laser ablation (Panchev, Kirtchev, & Dimitrov, 2011); radiofrequency (Manzocco, Anese, & Nicoli, 2008); ultrasound (Hashemi et al., 2018; Rosello´-Soto et al., 2015); microwaves (Bouras et al., 2015; Koubaa et al., 2016; Sahin et al., 2017); supercritical fluid extraction (Rosello´-Soto et al., 2018); gas-assisted mechanical expression (Koubaa et al., 2015; Koubaa, Lepreux, Barba, Mhemdi, & Vorobiev, 2017); enzyme-assisted extraction (Zhu et al., 2018); and solar energy (Afzal, Munir, Ghafoor, & Alvarado, 2017).

1.5

Laser ablation and radiofrequency

Laser ablation allows improving the heat and mass transferring processes. It has been used to recover macromolecular substances from plants and has good prospects for extracting pectins and aromatic substances and obtaining edible matrices (Panchev et al., 2011). Radiofrequency drying is a process which improves heat transfer as compared to conventional hot air drying. In this process, the water is evaporated in situ at relatively low temperatures (,80 C). This is achieved by combining different physical mechanisms, such as dipole rotation and the conductive effects that accelerate and uniformly heat the wet material (Piyasena, Dussault, Koutchma, Ramaswamy, & Awuah, 2003). The drying by radiofrequency allows the reduction in the time and space for process as well as the improvement in the biomaterial quality. One good example is preservation of the sweetness of the apple derivatives in comparison with the traditional blanching (Manzocco et al., 2008). In addition, this technology also has other advantages such as the compatibility with other processing techniques, in both different stages and continuity (Zhao, Flugstad, Kolbe, Park, & Wells, 2000).

1.6

Ultrasound

Modern food processing research targets ultrasound-based technologies that are able to preserve highest possible quantities of native biologically active compounds in fresh foods (Putnik & Bursa´c Kovaˇcev´c, 2017). Historically speaking, ultrasound has been tested and used for different applications, such as for prevention of browning in fruits (Putnik, Bursa´c Kovaˇcevi´c, Herceg, & Levaj, 2017a, 2017b) and for

8

Green Food Processing Techniques

aromatization of olive oil with basil (Veillet, Tomao, & Chemat, 2010). In addition, this was the main extraction procedure for extraction of essential oils (Giacometti et al., 2018) and fibers from food waste, for example, pectin, and pretreatment for various extractions (Putnik, Lorenzo, et al., 2018). This fueled recent interests in exploitation of the waste and by-products from the food industry (Soria & Villamiel, 2010). Moreover, in the food industry, ultrasound technology found its usage in various processes such as freezing, cutting, drying, tempering, bleaching, sterilization, and extraction (Chemat, Zill-e, & Khan, 2011). In particular, ultrasonic processing of liquid foods could result with several benefits, including enhanced emulsification, improved homogenization, fat globule size reduction, and improved microbial stability (Paniwnyk, 2017). Scale-up limitations of ultrasonic processing, including food and beverage processing, has been lately reviewed (Peshkovsky, 2017). Normally, processing equipment operates at frequencies between 20 kHz and 1 MHz (Vilkhu, Mawson, Simons, & Bates, 2008). The most frequently used solvents with ultrasound-assisted extraction (UAE) are water, ionic liquids, ethylene glycol, and glycerol (Lupacchini et al., 2017); thus this technology strongly supports the concept of “green chemistry.” This process is based on the phenomenon of cavitation induced by ultrasound waves, which induces the disruption of cellular tissue in extraction material (Zhu et al., 2017). Consequently, it fosters penetration of the solvent into source material, thus facilitating the extraction of target compounds, for example, valueadded bioactives. The interest for enhancing extraction of components from plant material has led to the increased awareness about UAE. Therefore, the most of literature that is concerned with this technology points out the advantages of ultrasound over conventional extraction (Chemat, Rombaut, Sicaire, et al., 2017; Tiwari, 2015). This includes improved efficiency, application of harmless solvents (e.g., labeled as GRAS), and lower energy utilization. For instance, it was shown that UAE of dried rosemary produced threefold more rosmarinic and carnosic acid than conventional alternative (Bellumori et al., 2016). Similar was documented for sage extracts where additional benefit was shortening of the extraction time and reduction of solvent consumption (Bilgin, Sahin, Dramur, & Sevgili, 2013).

1.7

Microwaves

The microwave technology is considered as one of the most promising food processing technologies. It has been used as a unit operation for various industry applications such as heating, drying, thawing, baking, blanching, pasteurization, digestion, puffing and foaming, and solvent extraction. In particular, scalability under both batch and continuous conditions, possibility for combination with other unit processes and good consumer acceptance, made microwave processing a significant technology. Particularly, it is useful for the optimization of manufacturing

Green food processing: concepts, strategies, and tools

9

processes in a less centralized system (Ahmed & Ramaswamy, 2007; Chemat, Rombaut, Meullemiestre, et al., 2017). The main advantages of microwave usage over conventional technologies include higher heating rates, reduced processing time, more uniform heating, the usage of lower processing temperatures, safe and easy handling, low maintenance, and energy saving (Perino-Issartier, Maingonnat, & Chemat, 2010). However, microwave power is commonly used for extraction of valuable compounds for food production. In short, thermal technique generates heat by utilization of the microwaves from dipole rotation and ionic conduction of solvent molecules (Lovri´c, Putnik, Bursa´c Kovaˇcevi´c, Juki´c, & Dragovi´c-Uzelac, 2017). Generated heat disrupts hydrogen bonds in extraction material, and damages cellular structures and releases the target compounds to the matrix, hence facilitating the extraction. Advantages associated with this type of extraction over conventional options include reduced time and expenditure of solvents, while at the same time extraction yields are improved (Chemat & Cravotto, 2013). Extraction parameters include type and the microwave power, polarity of the solvent, particle size, physiochemical attributes of extraction material, the time and temperature of extraction, and sample-to-solvent ratios (Chemat & Cravotto, 2013; Dai & Mumper, 2010). Appropriate selection of the solvent will define absorption of microwave power, that is, its heating and degree of penetration to the extraction material. The most appropriate solvents for the extraction are those with the highest microwave absorption capacity or those with high dielectric constants and dielectric loss constants. Some examples are water, ethanol, acetone, methanol, 2-propanol, and acetonitrile (Khoddami, Wilkes, & Roberts, 2013). Since microwave extraction is a thermal technique, there is obvious peril of degradation of thermally unstable compounds if extraction time is not set appropriately. This might be a difficult task as lengths of microwave extractions tend to be rather short in comparison to the conventional alternatives. Therefore, right chemometric optimization of all relevant parameters is crucial for selection of the solvent, use of microwave energy, and economic production of target compounds (Granato et al., 2018).

1.8

Nanotechnology

Nanotechnology is the study, design, creation, synthesis, manipulation, and application of materials, devices, and functional systems through the control of matter and the exploitation of phenomena and properties of a matter at a nanoscale. The food industry has already used nanotechnology to develop nanoscale ingredients to improve some sensory characteristics of food, such as color, texture, and flavor (Kessler, 2011; Morris, Woodward, & Gunning, 2011). Recent review highlights the current uses and future applications of nanotechnology in the food industry and the area of functional foods, including nanoemulsion, nanocomposites, nanosensors, nanoencapsulation, and food packaging (Thiruvengadam, Rajakumar, & Chung, 2018).

10

Green Food Processing Techniques

Moreover, some of the extracts obtained from the recovery process may contain compounds sensitive to temperature, light, etc. Therefore there is a need for nanoand micro-encapsulation or solubilization according to the physicochemical characteristics of the bioactives. Nanoencapsulation allows: (1) the reduction of the reactivity of the bioactives with environmental factors, such as light, O2, and humidity; (2) increase of solubility; (3) masking undesirable flavors and smells; (4) increase in bioavailability; (5) conversion of liquids to solids; (6) release control; (7) ease of handling/storage; and (8) incorporation into food. There are different commercial nanoencapsulation systems such as NanoCeuticals Supplements—RBC Life Sciences (Germany) consisted of nanoclusters technology. Those are nano-sized powders able to improve organoleptic properties and increase bioavailability. Super Nano Green Tea (China) are nanometric particles (200 nm) used for increased bioavailability. Nano-Selenium Rich Black Tea (China) allows an increase in the bioavailability of selenium. Nano Gold edible gold (Taiwan) are nanometric particles (0.5
100 nm) of gold obtained by physical methods.

1.9

Solar energy

The use of solar energy for food processing dates back to ancient civilizations (Egyptians and Phoenicians, Jews and Arabs, Indians and Chinese, Greeks and Romans, and even Mayas and Aztecs) when food processing and preservation have first played an important role in nutritional, aesthetic, and spiritual applications (Fig. 1.3). It is surprising that solar distillation of aromatic and medicinal herbs is not used nowadays, as many scientific books report the use of solar energy even for extraction, distillation, drying, and preservation (French, 1651).

Figure 1.3 Solar distillation (French, 1651).

Green food processing: concepts, strategies, and tools

11

Solar energy is among the most promising renewable energy resources as it is freely and abundantly available in many regions of the world, thus being a green energy to be taken into account in future years (Afzal et al., 2017).

1.10

Challenges with experiential methodology, theory, and statistical calculations

One of the main problems with correct economic evaluation of the any industrial process is the standardization of comparisons among different techniques. For instance, even though there is a slew of studies that compare various extractions (Giacometti et al., 2018), few of them really offer objective mathematical value of measurement expressed in SI units (such as measurements for pressure, temperature, time, etc.). This is not surprising due to employment of various processing parameters for different technologies. For instance, some extractions are short (HVED), others are long (conventional), some rely on heat (microwave), others on pressure (HPP), and so on. Hence, one is faced with the challenge to compare strength of electric field against microwave power, pressure, etc. Indeed, it is even very difficult to separate and quantify various influences that drive extractions within the same process as the case with HPP where extraction is driven by both heat and pressure. To help tackle this methodological problem, there is one attempt reported on high-pressure recovery of anthocyanins from grape skin pomace (Putnik, Bursa´c Kovaˇcevi´c, et al., 2018). In this study, authors mathematically formulated and evaluated the extraction rate that objectively measures the milligrams of target compound in a gram of a dry matter that is extracted per minute of time. In other words, this extraction rate measures the “velocity of extraction” and can be applied to almost any extraction that has two most common parameters, such as the time and the amount of extracted compound. This is a useful approach as foundation for other types of comparisons as economic profitability. For any extraction, it is crucial to accurately measure influence of independent parameters. In case of an HPP, the first step is to determine the accurate influence of pressure and temperature for entire extraction. This should account for entirety of processing, and in the case of the HPP extraction should include all stages of pressurizing, namely (1) come-up time or compression (gradual increase of pressure/temperature to achieve target setting); (2) hold time or constant (high pressure (HP) target settings); and (3) decompression (gradual decrease of pressure and temperature toward the atmospheric values). However, most of the current research calculates influence for HPP based on target settings for the pressure, temperature, and time that were imputed in command console of the HPP equipment. Research showed that this significantly differs from the influences that are really exerted in the cylinder for compression of the HPP equipment (Putnik, Bursa´c Kovaˇcevi´c, et al., 2018). Mainly due to the fact that for a different HPP pressure target settings from console, different compression/expansion times will be needed to achieve

12

Green Food Processing Techniques

them (together with different changes in temperature due to Amontons’ law). In addition, alteration in the temperature occurs due to adiabatic compression that modifies heating and heat exchange between the sample and pressure-transmitting fluid during come-up and hold time, hence affecting the extraction (Zhang, Barbosa-Canovas, & Balasubramaniam, 2011). Objective measurement can be assessed by measuring the area under the curves (AUCs) with Riemann sums for each batch of samples, for both pressure and temperature curves (Dupont, 2009). Subsequently, with AUCs for pressure (MPa min) and temperature ( C min), it is possible to calculate the abovementioned extraction rates, separate influences of temperature and time on extraction (Putnik, Bursa´c Kovaˇcevi´c, et al., 2018), and conduct normal chemometric comparisons as previously explained (Granato et al., 2018). Finally, it is important to note that for any multivariate comparisons (e.g., as for heat and pressure), it is best to use the highest number of independent variables in a single comparison in order to avoid inflation of the type 1 errors and false-positive findings, commonly known, as misleading results (Granato et al., 2018).

1.11

Strategy, challenges, and perspectives

In recent years, food industry is rapidly adapting nonthermal food processing, like nonthermal plasma, pulsed electric field, HHP, and high-intensity ultrasound. These nonthermal techniques tend to save production resources and are effective at room (or at slightly elevated) temperature. This in turn reduces negative heat effects on the nutrient composition and improves food quality. In addition to that, the abovementioned technologies are often more selective, faster, and sustainable than conventional alternatives. Based on current customers’ needs to get high-quality (functional) foods, it is crucial to engineer products by adding bioactive compounds, commonly isolated from the plants or economic food raw materials and food by-products. Modern society and expansion of environmental consciousness request that food production be done in an eco-friendly manner and with minimal burden on environment. Hence, the focus is on extraction methods that are crucial segment of modern food production. In this sense, these nonthermal techniques are considered “green” extractions because conventional and often toxic organic solvents can be replaced by the “green” alternatives. Taking into account the versatility of these technologies and target chemicals, one of the key points for promotion and further exploitation of such technologies at an industrial level is to select the fit technology for the right food process. Moreover, it is of great importance to optimize processing conditions to obtain most economic production. In addition, it is necessary to have the right equipment in order to have reliable processing conditions for obtaining reproducible products and maintenance of quality control.

Green food processing: concepts, strategies, and tools

13

One of the main obstacles for omnipresent application of the advanced technologies in food industry is the price of their implementation and perception that they are impractical to implement. Hence, all stakeholders should contribute their share of efforts in order to harvest the benefits of application of the advanced technology to a food production, while funding donors should have strategy to finance projects that promote the application of “green” technologies in food processing. One good example is a GREENVOLTEX project (high-voltage discharges for green solvent extraction of bioactive compounds from Mediterranean herbs) that is funded by Croatian Science Foundation. The focus of a GREENVOLTEX is to use natural and bio-derived solvents for extraction. The goal is to develop, implement, and promote the use of safer, “greener” technologies and sustainable industrial solvents. The plants used in the project are leaves from olive, sage, rosemary, oregano, and thyme, all extracted by HVED technology for production of functional foods. In future, hopefully, projects as this one will expedite the implementation of more efficient technology for broader food operations.

Acknowledgments F.J. Barba and J.M. Lorenzo would like to acknowledge the EU Commission for the funds provided by the BBI-JU through the H2020 Project Aquabioprofit (Grant Agreement no. 790956) “Aquaculture and agriculture biomass side stream proteins and bioactives for feed, fitness, and health promoting nutritional supplements.” Moreover, F.J.B. and J.M.L. would like to acknowledge Generalitat Valenciana for the financial support (IDIFEDER/2018/046 Procesos innovadores de extraccio´n y conservacio´n: pulsos ele´ctricos y fluidos supercrı´ticos) through European Union ERDF funds (European Regional Development Fund). P. Putnik, D. Bursa´c Kovaˇcevi´c, and A. Reˇzek Jambrak wish to thank Croatian Science Foundation for support through the funding of the project: “High voltage discharges for green solvent extraction of bioactive compounds from Mediterranean herbs (IP-2016-06-1913).”

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Barba, F. J., Putnik, P., Bursa´c Kovaˇcevi´c, D., Poojary, M. M., Roohinejad, S., Lorenzo, J. M., & Koubaa, M. (2017). Impact of conventional and non-conventional processing on prickly pear (Opuntia spp.) and their derived products: From preservation of beverages to valorization of by-products. Trends in Food Science & Technology, 67, 260
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331. Thiruvengadam, M., Rajakumar, G., & Chung, I.-M. (2018). Nanotechnology: Current uses and future applications in the food industry. 3 Biotech, 8(1), 74. Available from https:// doi.org/10.1007/s13205-018-1104-7. Tiwari, B. K. (2015). Ultrasound: A clean, green extraction technology. Trends in Analytical Chemistry, 71, 100
109. Available from https://doi.org/10.1016/j.trac.2015.04.013. Veillet, S., Tomao, V., & Chemat, F. (2010). Ultrasound assisted maceration: An original procedure for direct aromatisation of olive oil with basil. Food Chemistry, 123(3), 905
911. Available from https://doi.org/10.1016/j.foodchem.2010.05.005. Vilkhu, K., Mawson, R., Simons, L., & Bates, D. (2008). Applications and opportunities for ultrasound assisted extraction in the food industry—A review. Innovative Food Science and Emerging Technologies, 9, 161
169.

Green food processing: concepts, strategies, and tools

21

Vincekovi´c, M., Viski´c, M., Juri´c, S., Giacometti, J., Bursa´c Kovaˇcevi´c, D., Putnik, P., . . . Reˇzek Jambrak, A. (2017). Innovative technologies for encapsulation of Mediterranean plants extracts. Trends in Food Science & Technology, 69, 1
12. Available from https://doi.org/10.1016/j.tifs.2017.08.001. Wo´zniak, Ł., Marszałek, K., & Ska˛pska, S. (2016). Extraction of phenolic compounds from sour cherry pomace with supercritical carbon dioxide: Impact of process parameters on the composition and antioxidant properties of extracts. Separation Science and Technology, 51(9), 1
8. Available from https://doi.org/10.1080/ 01496395.2016.1165705. Wo´zniak, Ł., Marszałek, K., Ska˛pska, S., & Je˛drzejczak, R. (2017). The application of supercritical carbon dioxide and ethanol for the extraction of phenolic compounds from chokeberry pomace. Applied Sciences, 7(4), 322. Available from https://doi.org/10.3390/ app7040322. Zhang, H. Q., Barbosa-Canovas, G. V., & Balasubramaniam, V. M. (2011). ). Nonthermal Processing Technologies for Food. UK: John Wiley & Sons Ltd. Zhao, Y., Flugstad, B., Kolbe, E., Park, J. W., & Wells, J. H. (2000). Using capacitive (radio frequency) dielectric heating in food processing and preservation—A review. Journal of Food Process Engineering, 23, 25
55. Zheng, S., Hu, X., Ibrahim, A.-R., Tang, D., Tan, Y., & Li, J. (2011). Supercritical fluid drying: Classification and applications. Recent Patents on Chemical Engineering, 3(3), 230
244. Available from https://doi.org/10.2174/1874478811003030230. Zhu, Z., Guan, Q., Koubaa, M., Barba, F. J., Roohinejad, S., Cravotto, G., . . . He, J. (2017). HPLC-DAD-ESI-MS2 analytical profile of extracts obtained from purple sweet potato after green ultrasound-assisted extraction. Food Chemistry, 215, 391
400. Available from https://doi.org/10.1016/j.foodchem.2016.07.157. Zhu, Z., Li, S., He, J., Thirumdas, R., Montesano, D., & Barba, F. J. (2018). Enzyme-assisted extraction of polyphenol from edible lotus (Nelumbo nucifera) rhizome knot: Ultrafiltration performance and HPLC-MS2 profile. Food Research International, 111, 291
298.

Further reading Lorenzo Rodriguez, J. M., Munekata, P., Putnik, P., Bursa´c Kovaˇcevi´c, D., Muchenje, V., & Barba, F. (2018). Sources, chemistry and biological potential of ellagitannins and ellagic acid derivatives. In Atta-ur-Rahman (Ed.), Studies in Natural Product Chemistry. Elsevier.

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Ultrasound technology for food processing, preservation, and extraction

2

Boutheina Khadhraoui1,2, Anne-Sylvie Fabiano-Tixier2, Philippe Robinet1, Re´mi Imbert1 and Farid Chemat2 1 Laboratoires Arkopharma, Laboratoire d’e´tude des substances naturelles, Carros, France, 2 Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France

2.1

Ultrasound: principle and influencing factors

2.1.1 Principle Ultrasound (US) is mechanical waves that have the property to spread in elastic medium such as liquids (Cravotto & Cintas, 2006; Pingret, Fabiano-Tixier, & Chemat, 2013a). The ultrasonic wave is mainly characterized by four physical parameters, namely, the frequency (Hz), the ultrasonic power (W), the wavelength (cm), and the ultrasonic intensity (UI) (W/cm2). It is worth mentioning that the UI is directly related to the ultrasonic power [UI 5 P/S; P: power (W) and S: the emitting surface (cm2)] (Pe´trier, Gondrexon, & Boldo, 2008; Pingret et al., 2013a). As illustrated in Fig. 2.1, US frequency is above the human hearing range (from 16 Hz to 20 kHz), it ranged between 20 kHz and 10 MHz. Giving this large range of frequencies, two zones can be distinguished: (1) diagnostic US and (2) power US (Fig. 2.1). High frequencies (from 2 to 10 MHz) and low ultrasonic power (P , 1 W) are applied in the case of diagnostic US essentially used for therapeutic purposes such as medical imaging. In this power range, there is no destructive effect into the medium. The desired effect is only to characterize the medium by measuring the submitted modification of the ultrasonic wave during its propagation (Mason, Paniwnyk, & Chemat, 2003; Pe´trier et al., 2008; Pingret et al., 2013a). Power US is characterized by low frequencies (from 20 to 100 kHz) and high ultrasonic power (P . 1 W) (Pe´trier et al., 2008). Contrarily to diagnostic US, high power promotes physical and chemical effects by creating sufficient interaction between the ultrasonic wave and the elastic medium. This frequency range is widely valorized in several fields such as food processing and the extraction of natural products. Physical impacts are essentially observed at low frequencies (from 20 to 100 kHz). The extended range of power US frequencies (up to 2 MHz) is used in sonochemistry (Mason et al., 2003). Different chemical impacts can be observed in this frequency range mainly formation of radicals.

Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00002-1 © 2019 Elsevier Inc. All rights reserved.

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Green Food Processing Techniques

Audible zone: sounds

Infrasound

Ultrasound

Frequency

16 Hz

10 MHz

20 kHz Low 20 kHz frequency 100 kHz

High frequency

Very high 2 MHz frequency 10 MHz

Frequency

Low pow er

1W

Extended power range (20 kHz to 2 Mhz) High power

Power

Figure 2.1 Frequency and power ranges of sound.

US-induced impacts can be attributed to the cavitation phenomenon referring to bubble formation, growth, and implosion during its propagation into an elastic medium (Bermu´dez-Aguirre & Barbosa-Ca´novas, 2011; Cravotto & Cintas, 2006; Pingret et al., 2013a; Pingret, Fabiano-Tixier, & Chemat, 2013b). The benefit of the cavitation phenomenon is mainly to concentrate acoustic energy in small volumes (bubbles) converting acoustic energy in extreme physical conditions of temperature and pressure (Louisnard & Gonza´lez-Garcia´, 2011). While passing through an elastic medium, a spatial and temporal variation of acoustic pressure is induced into the medium (Fig. 2.2). An oscillatory movement can be therefore observed on the surface (Kentish & Ashokkumar, 2011). The medium constitutive molecules undergoing a succession of compression and rarefaction phases can be displaced from their equilibrium position (Laugier, 2007). During the compression phase (negative acoustic pressure), intermolecular distance is significantly reduced leading to the possible collision with the surrounding molecules. During the rarefaction phase (positive acoustic pressure), intermolecular distance increases dramatically (Pingret et al., 2013a; Vyas & Ting, 2018). Voids are then created between the constitutive molecules once their cohesive forces are exceeded by a higher ultrasonic power. These bubbles are formed from vapors or gas initially present in the elastic medium. It is important to consider that at low acoustic pressure bubbles are rapidly dissolved in the elastic medium. However, at high pressures, bubbles are more unstable (also called transient bubbles). Their size

Ultrasound technology for food processing, preservation, and extraction

25

Figure 2.2 Compression and rarefaction cycles induced by a sound into an elastic wave and the resulting cavitation phenomenon.

undergoes the same periodic fluctuations as acoustic pressure (Vyas & Ting, 2018). As described in Fig. 2.2, they grow remarkably during the rarefaction phase by rectified diffusion. Vapors and/or gases entering bubble are partially expelled during the compression phase resulting in a final increase in bubble size after many cycles of rarefaction/compression phases. Indeed, the amount of transferred gas depends on bubble surface. Internal diffusion during the rarefaction phase (larger diameter)

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predominates over the external transfer of the compression phase (smaller diameter). In other words, the exchange is not balanced between the two phases, the volume of the bubble increases with each cycle until reaching a critical size. At this stage, bubbles will collapse during a compression cycle (Mason et al., 2003; Pingret et al., 2013a; Vyas & Ting, 2018; Wu, Guo, Teh, & Hay, 2013). Bubble implosion results in the creation of hot spot with extreme conditions of temperature (up to 5000K) and pressure (up to 5000 atm) which explains their extremely high physical and chemical reactivity (Fig. 2.2) (Bermu´dez-Aguirre & Barbosa-Ca´novas, 2011; Chemat, Tomao, & Virot, 2008; Gonza´lez-Garcia, 2011; Louisnard & Pingret et al., 2013a; Vyas & Ting, 2018; Wu et al., 2013). In the case of homogeneous cavitation, bubbles occur in homogeneous liquids and collapse symmetrically (Mason et al., 2003). Bubbles implosion generates powerful shock waves and shear forces into the surrounding medium resulting in the increase in mass transfer and the chemical reactivity of the medium (Chemat et al., 2008; Mason et al., 2003; Soria & Villamiel, 2010; Vyas & Ting, 2018). A second type of cavitation can be defined namely the heterogeneous cavitation (Mason et al., 2003). US can be applied in the case of heterogeneous liquid
liquid reactions involving two immiscible liquid phases, which are often limited by the transfer of a reagent from one phase to the other. In this case, cavitational collapse will create very fine emulsions increasing dramatically the interfacial contact and thus enhancing the reaction between the different liquid phases (Mason et al., 2003). Acoustic cavitation may also occur into heterogeneous liquid medium/solid particles or agglomerates. Suspended particles are forced into rapid motion which can be accompanied by interparticle collisions. A noticeable reduction in the particles size can be observed in this case (Laugier, 2007; Mason et al., 2003). Heterogeneous cavitation in solid surface-liquid systems reactions is one of the most common cases of US application. While occurring at or near a solid surface, the bubble collapse is asymmetric generating microjets and shock waves directed toward the solid surface (Fig. 2.3) (Chemat et al., 2008; Kentish & Ashokkumar, 2011). This asymmetric implosion can be explained by the resistance of the solid surface to the liquid flow (Mason et al., 2003). Solid surface properties are of a great importance and should then be taken into consideration since they influence the US efficiency. Solid surfaces can be broadly divided into four groups: (1) soft solids, (2) friable solids, (3) hard solids, and (4) porous solids (Laugier, 2007). Soft solids have the ability to absorb and thus to attenuate the acoustic wave with no significant US impact. As for friable solids, microjets are able to break solid particles increasing active zone and mixing effect. In the case of hard solids, US microjets are not powerful enough to break these solids. However, they are able to remove some contaminants and/or deposits on the solid which explains the widespread area of US application for surfaces cleaning. Concerning porous solids, the benefit of US owes to its ability to accelerate mass and heat transfer by increasing the shear forces and diffusion into the solid pores. US may therefore have a highly considerable effect on the porous solid surface which can be deeply deformed or induced detexturation (Laugier, 2007). The last case of heterogeneous solid
liquid cavitation can be useful for extraction of food

Ultrasound technology for food processing, preservation, and extraction

27

Figure 2.3 Heterogeneous cavitation: collapse near a leaf surface.

ingredients and natural products from fruit and vegetables. Fig. 2.3 presents the evolution of cavitation bubbles when generated at the vicinity of a leaf surface. Cavitation bubble generated close to the plant leaf surface grows by rectified diffusion and collapses when reaching a critical size. Liquid jets of extremely high temperature and pressure are generated and targeted at the leaf surface (Awad, Moharram, Shaltout, Asker, & Youssef, 2012; Chemat & Khan, 2011; Mason et al., 2003; Veillet, Tomao, & Chemat, 2010; Wu et al., 2013). These microjets are able to detexture leaf cuticle and external membrane layers promoting release of cellular content and providing an excellent diffusion of solvent in extraction medium (Chemat, Rombaut, Meullemiestre et al., 2017; Mason et al., 2003; Paniwnyk, Cai, Albu, Mason, & Cole, 2009; Rombaut, Tixier, Bily, & Chemat, 2014; Toma, Vinatoru, Paniwnyk, & Mason, 2001; Veillet et al., 2010; Wang & Weller, 2006).

2.1.2 Influencing factors The most important parameters that can influence US in the food processing are presented in this section. These parameters can be divided into four groups: (1) acoustic wave intrinsic parameters, (2) shape and size of ultrasonic reactors, (3) cavitation bubble characteristics, and (4) medium physical parameters.

2.1.2.1 Acoustic wave intrinsic parameters The parameters intrinsically related to the ultrasonic wave such as the frequency (f), the amplitude of acoustic pressure (λ), the ultrasonic power (P) and the resulting UI have a determinant effect on the cavitation bubble and thus the cavitation phenomenon. These parameters are resumed and described in Table 2.1. US frequency is an

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Green Food Processing Techniques

Table 2.1 The principle parameters influencing the cavitation phenomenon. Parameter

Unit

Description

Frequency (f)

Hz

Period (P)

s

Wavelength (λ)

cm

Amplitude (A) Celerity (C)

dB or Pa m/s

The number of cycles per seconds which is determined by the source of USs The time of one cycle. It is the reciprocal of the frequency (1/f) The length (distance) of one cycle which is determined by both the source of USs (with a given frequency) and the medium (with a given propagation velocity) The height of the wave

Ultrasonic power (P)

W

Represents how fast the wave is passing through the medium. Propagation velocity is dependent on the medium and is related to the stiffness of the medium and something called the bulk modulus (directly related to the stiffness of the medium), therefore, denser materials also have a faster propagation velocity Can be measured by calorimetric method. The effective US power is calculated according to the following equation:

P 5 m  Cp 

UI

W/cm2

dT dt

(2.1)

where Cp is the heat capacity of the solvent at constant pressure (J/g/ C), m is the mass of solvent (g), and dT/dt is the temperature rise per second The UI is directly related to the ultrasonic power. It can be calculated according to the following equation:

UI 5

P S

(2.2)

where UI is the ultrasonic intensity (W/cm2), P is the US power (W), and S is the emitting surface of the transducer (cm2) UI, Ultrasonic intensity; US, ultrasound.

important parameter which has to be chosen and optimized. This parameter impacts the bubble population (size, number, distribution, etc.) (Wood, Lee, & Bussemaker, 2017). The bubble characteristics at different frequencies (20, 205, 358, 618, 1071 kHz) are presented in Table 2.2. Bubbles are much smaller and their implosion is much more rapid at higher ultrasonic frequency [Eq. (2.5)]. Lower frequencies generate larger bubbles. For example, at 20 kHz, the bubble size is estimated to be 15 times of that generated at 358 kHz. Consequently, bubble collapse will be more violent with higher localized temperatures and pressures (Chemat, Rombaut, Meullemiestre et al., 2017; Leong, Ashokkumar, & Kentish, 2011; Mason, Chemat, & Vinatoru, 2011).

Ultrasound technology for food processing, preservation, and extraction

29

Table 2.2 The values of maximal bubble radius (Rm) and its collapse time (τ), as a function of ultrasonic frequency (f) in air-saturated water and at ultrasonic intensity of 10 W/cm2. Frequency (kHz)

Maximal diameter of pulsating bubble (μm)

Collapse duration (μs)

20 205 358 618 1071

150 17.5 10.0 5.8 3.3

5 1.6 0.9 0.5 0.3

When US frequency increases, there are more collapse events per unit time, and then, cavitation bubbles will collapse much more rapidly (Table 2.2). This is because the length of rarefaction phase (during which cavitation bubbles grow) is inversely proportional to the ultrasonic frequency (Chemat, Rombaut, Sicaire et al., 2017), which explains the very low size of bubbles at high frequencies compared to that at low frequencies. The resonance size is thus inversely related to the applied frequency. It should also be noted that, when applying high frequencies, the amount of energy released during implosion is minimum (Carrillo-Lopez, Alarcon-Rojo, Luna-Rodriguez, & Reyes-Villagrana, 2017), and the cavitation phenomenon is more difficult to be observed. Larger amplitudes and intensities are thus required to generate cavitation. Low frequencies privilege the physical effects instead of the chemical ones while the sonochemical effects are dominant at high frequencies (Kentish & Ashokkumar, 2011). This is because the number of the generated active bubbles is higher. Nevertheless, it is worth mentioning that chemical effects are generally more dominant at intermediate frequencies (200
500 kHz) than at very high frequencies. For example, the formation of radicals OH is more important at 358 kHz compared to that at 1062 kHz (Kentish & Ashokkumar, 2011). Very high frequencies applied for diagnostic US (f . 2 MHz) are considered as nondestructive, because rarefaction is too short to induce cavitation but simply pass through it (Kentish & Ashokkumar, 2011; Pingret et al., 2013a). Ultrasonic power has the most important effect on cavitation phenomenon. The increase in power increases US impacts. However, this parameter has to be optimized to respect physical limit and to minimize processes cost. Physical limit consists on bubble shielding layer which can be formed on the surface of the emitting source at high ultrasonic power (Kentish et al., 2008; Laugier, 2007). This gas layer reduces the ultrasonic wave propagation velocity into the medium and thus reduces its effects (Kentish & Feng, 2014). Working in pulsations mode can reduce the formation of this bubble shielding (Laugier, 2007). The UI, which is directly related to the ultrasonic power (Table 2.1), has also an important impact on US efficiency. The increase in the UI has the same influence as that of the ultrasonic power. To achieve cavitation threshold, a minimum value of UI is required (Vyas & Ting,

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Green Food Processing Techniques

2018). Relatively high UI are required (UI . 10 W/cm2) to achieve transient cavitation. In this case, cavitation bubbles grow very quickly and then implode violently without exceeding few cycles (Mason et al., 2003; Wood et al., 2017). In the case of low UI (1
3 W/cm2), bubbles are stable. They oscillate around their equilibrium position with a small amplitude (Mason et al., 2003). However, an optimal UI value has to be chosen in order to limit the bubble shielding formation which disturb the ultrasonic wave propagation. This value depends on the medium properties, the presence of saturating gas, and the temperature. For example, UI should be increased when working at high frequencies or when working with liquids of high viscosity (Santos, Lodeiro, & Capelo-Martı´nez, 2009). Therefore this parameter has to be studied for optimization depending on the medium properties and also on the desired effect since the increase of UI generally results in an increase of sonochemical effects (Chemat, Rombaut, Sicaire et al., 2017; Mason et al., 2003). As for the pressure amplitude, it has also an effect on the formation and implosion of cavitation bubbles. With the increase in the pressure amplitude, bubbles collapse will be more violent (higher pressure and temperature). It should be emphasized that high amplitudes can lead to rapid deterioration of the ultrasonic transducer, which results in liquid agitation instead of cavitation and in poor transmission of the US through the liquid media (Chemat, Rombaut, Sicaire et al., 2017). The amplitude should also be increased when working with liquids of high viscosity (Santos et al., 2009).

2.1.2.2 Cavitation bubble characteristics The nature and the importance of the chemical and/or physical impacts related to the propagation of the ultrasonic wave through the medium are closely dependent on the dynamics, location, and number of cavitation bubbles. The dynamics of a transient cavitation bubble is expressed by Eq. (2.3) of Rayleigh
Plesset (Lauterborn & Kurz, 2010). "


 #

3k d2 R 3 dR 2 2θ R0 2θ 2 Pk 2 Pa 1 Pv 2 ρ R 2 1 5 Ph 2 Pv 1 dt 2 dt R0 R R (2.3) where ρ is the solvent density, R is the radius of bubble, Ph is the hydrostatic pressure, Pa is the acoustic pressure, Pv is the vapor or gas pressure, Pk is the critical pressure of bubble nucleation, k 5 Cp/Cv is the ratio of specific heats, and θ is the parameter that depends on the viscosity and superficial tension of the liquid. The integration of Eq. (2.3) allows the calculation of the size of a bubble [Eq. (2.4)], as also the time of implosion [Eq. (2.5)] as a function of US frequency (Pingret et al., 2013a):
   4 2 1=2 2ðPA 2Ph Þ 1=3 R0 5 ð PA 2 Ph Þ 11 3Wa ρPA 3Ph

(2.4)

Ultrasound technology for food processing, preservation, and extraction

31

where Wa 5 2πf ti D0:915R0

rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ρ ðPh 1 Pa 2 Pv Þ

(2.5)

According to Eq. (2.4), the bubble radius (R0) is inversely related to the ultrasonic frequency (f). As f increases, the bubble radius decreases, which is in coherence with the Table 2.2 presented in Section 1.2.1. In the case of low frequencies, bubbles radius increases which privileges US physical impacts. The duration of collapse is also inversely related to the ultrasonic frequency. When increasing f, the collapse duration and thus the bubble reactivity decreases.

2.1.2.3 Medium physical parameters The medium presents intrinsic characteristics that need to be taken into account and to be chosen in order to achieve the US desired physical and/or chemical impacts. The medium physical parameters such as viscosity, surface tension, and vapor pressure will impact the cavitation threshold (Blake threshold) according to the equation below (Kentish & Ashokkumar, 2011): 4 P B 5 P0 2 Pv 1 ρ 3

sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2ρ 3ðP0 1 2ðρ=R0 Þ 2 Pv ÞR0 3

(2.6)

where R0 is the initial nanobubble radius, PB is the bubble pressure, P0 is the system pressure, Pv is the vapor pressure and σ is the surface tension. To induce cavitation phenomenon into a liquid medium, negative pressure during rarefaction phase has to exceed the cohesive forces between the constitutive molecules (Fig. 2.2). When working with liquids with high viscosity and/or high surface tension, the cavitation threshold increases remarkably [Eq. (2.6)]. The viscosity can influence the propagation of the ultrasonic wave by increasing its absorption and thus reducing ultrasonic active zone (Laugier, 2007). In this case, the amplitude and thus the UI should be increased. Liquids with low vapor pressure facilitate propagation of the ultrasonic wave and promote effects of cavitation phenomenon (Chemat, Rombaut, Sicaire et al., 2017). A liquid is able to cavitate when the pressure above the liquid (the sum of hydrostatic and acoustic pressures) is below the liquid’s vapor pressure, which depends on the liquid temperature (Kentish & Ashokkumar, 2011). The cavitation phenomenon is more difficult to induce in pure liquids (Chemat, Rombaut, Meullemiestre et al., 2017; Pingret et al., 2013a). The presence of gas nuclei initiates the formation of cavitation bubbles. Both nucleation and cavitation phenomena are controlled by the liquid gas content (Vyas & Ting, 2018). In the absence of gas nuclei, the negative pressure during the rarefaction phase should be increased to break up the cohesive forces of the liquid. However, when the liquid medium is saturated with gas, the acoustic pressure required to induce cavitation phenomenon is low from 1 to 2 bar.

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Green Food Processing Techniques

The gas composition can also influence the bubble reactivity and more specifically its chemical reactivity. For example, the presence of oxygen privileges the formation of radicals OH (Mason et al., 2003; Wood et al., 2017). Moreover, the nature and the partial pressure of the bubble gas influence the reached temperature and pressure during the implosion. High partial pressure decreases temperature and pressure values. Similarly, the presence of gases with low polytropic coefficient and high thermal conductivity results in lower temperature and pressure. The polytropic coefficient depends on the gas nature; temperatures and pressures reached with monoatomic gases (such as argon) are higher than that reached with diatomic ones (such as oxygen) (Laugier, 2007). The gas heat capacity should also be taken into account. Gases with low heat capacity (xenon, argon, etc.) are more adapted to US application (Laugier, 2007). Temperature is an important parameter which strongly impacts the liquid’s properties. When increasing temperature, we decrease of both viscosity and surface tension, and we increase the liquid’s vapor pressure (Chemat, Rombaut, Sicaire et al., 2017). A rise in vapor pressure increases vapors flow entering into the bubble cavity. Numerous cavitation bubbles are thus formed and will grow very quickly and collapse less violently diminishing then the cavitation efficacy. The main influencing parameters and the favorable conditions for ultrasonic cavitation are resumed in Table 2.3. G

2.1.2.4 Shape and size of ultrasonic reactors Besides the parameters mentioned above, the shape and size of ultrasonic reactors are important for the propagation of the ultrasonic wave mainly its reflection on the reactors walls. It is thus crucial to optimize the choice of ultrasonic reactors. For example, in the case of ultrasonic bath, it is important to take into account the shape and the thickness of the vessel that is critical for the acoustic wave reflection. The shape of the reaction vessel is critical. A flat-bottom vessel such as a conical flask seems to be the best choice to minimize the waves’ reflection (Lorimer & Mason, 1987). Minimal vessel thickness is also advanced to reduce attenuation (Santos et al., 2009). To maximize the energy transferred to the elastic medium, the ultrasonic bath dimensions must be optimized. In the case of ultrasonic probe, the shape and the diameter must also be optimized. The stepped probe gives the highest amplitude magnification (Pingret et al., 2013a). Nevertheless, the exponential probe shape is more adapted to microapplications. Moreover, the distance between the wall of the container and the ultrasonic probe must be kept at the minimum without touching the container. It should be emphasized that the composition of the probe emitters is also of a great importance. Quartz, pyrex, and other new materials are recommended to avoid the corrosion related to titanium alloy (Cravotto et al., 2008; Pingret et al., 2013a).

Ultrasound technology for food processing, preservation, and extraction

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Table 2.3 Summary of the influence of different parameters on acoustic cavitation. Parameter

Involved properties

Effects

Favorable conditions

Ultrasonic intensity

Acoustic pressure

Optimum value/cavitation threshold vs bubbles shielding

Frequency

Acoustic pressure Period Wavelength Gas content Polytropic coefficient Solubility in the medium Conductivity Chemical reactivity Viscosity Vapor pressure

Cavitation threshold Bubbles number and size Cavitation threshold Duration of collapse Reaction zone Nucleation Cavitation threshold Intensity of cavitation events Specific reactions

Dissolved gas

Temperature

Hydrostatic pressure

Gas solubility Density

Liquid

Vapor pressure

Surface tension

Viscosity Bulk liquid temperature

Immiscible liquid phase

Solid constituents

Surfactants and electrolytes

Cavitation threshold Intensity of cavitation events

Cavitation threshold Intensity of cavitation events Cavitation threshold Intensity of cavitation Rate of chemical reaction Size of the nuclei (cavitation threshold) Transient threshold Intensity of collapse Rate of reaction Threshold/nucleation Almost all physical properties Interfacial cavitation Number of bubbles per unit volume Reaction kinetics Cavitation threshold/ nucleation, attenuation of sound intensity Cavitation threshold Reaction kinetics

Should be adapted to the desired impacts (physical vs chemical impacts) Low solubility Gases with higher polytropic coefficient and lower thermal conductivity (monatomic gases)

Should be adapted to the desired application (thermolabile active compounds, physiochemical and organoleptic properties, etc.) Low hydrostatic pressure

Liquids with low vapor pressure

Low surface tension

Low viscosity Optimum value exists Generally lower temperature preferable

Depends on nature of the system

Low concentrations

Case study of each system necessary to ascertain exact nature of the effect

34

2.2

Green Food Processing Techniques

Ultrasound techniques

The choice of the US equipment is of a great importance whether at the laboratory scale or at the industrial scale. In this section, we briefly describe the main types of sonoreacters applied in the food processing field. All US techniques are composed of a transducer which generates the US power and an emitter which irradiates this US power (Pingret et al., 2013a). Three types of US transducers can be distinguished: mechanical converters, magnetostrictive transducers, and piezoelectric converters (Laugier, 2007). In the case of mechanical transducers, the US power is generated from a mechanical vibration resulting from a fluid circulation (liquid whistle). As for magnetostrictive and piezoelectric transducers, the US power is generated by converting electrical energy into sound energy by vibrating mechanically at ultrasonic frequencies (Laugier, 2007). The piezoelectric transducer is the most commonly type used in US reactors. It is based on a crystalline ceramic material that responds to electrical energy (Pingret et al., 2013a). Piezoelectric transducers have several advantages. They are small, inexpensive, with a wide range of shapes. Moreover, they offer better electroacoustic conversion than magnetostrictive and mechanical ones (Laugier, 2007). Different US equipment has been developed for both laboratory and industrial scales. The most commonly used techniques at both scales are detailed in this section.

2.2.1 Ultrasound techniques at laboratory scale For laboratory scale, two different types of US equipment are most commonly used: the ultrasonic bath and the probe-type US equipment. These two systems have several differences (shape, efficiency, purpose, etc.). However, both systems are based on a transducer as a source of US power (Pingret et al., 2013a). The selection of the suitable technique should be based both on the characteristic properties of these equipment and on the desired purpose. As presented in Fig. 2.4A, the ultrasonic bath consists of a stainless steel tank with one or more ultrasonic generally transducers bonded to the base. The majority of ultrasonic baths operate at a frequency of around 40 kHz. They have many advantages such as their low cost, their availability, and the possibility to treat many samples at the same time. However, this system presents several shortcomings including the attenuation of the ultrasonic power by the liquid contained in the bath and the glassware containing the sample as well as its low reproductivity compared with the probe-based systems (Chemat, Rombaut, Sicaire et al., 2017). This limits their applications to cleaning purposes. REUS (Contes, France) has recently developed a new reactor which operates at 25 kHz with a capacity of 0.5
3 L and an intensity of 1 W/cm2. This new system has a double-jacket envelope allowing the temperature control (Fig. 2.4B). Contrarily to the ancient bath system, the REUS ultrasonic reactor is very efficient and reproducible.

Ultrasound technology for food processing, preservation, and extraction

35

Figure 2.4 Commonly used ultrasonic systems [(A) US bath, (B) US reactor with stirring, (C) US probe, (D) continuous sonication with US probe]. US, Ultrasound.

As for horn systems (or probes), they are attached to a horn tip known as sonotrode (Fig. 2.4C). Most of developed sonotrode systems operate at 20 kHz. There are different probes designs with different lengths, diameters, and probe shapes. It should be emphasized that the probe shape is an important parameter which has to be carefully selected. This choice should be made according to the desired

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Green Food Processing Techniques

application and to the sample volume. For example, small emitting surfaces are more efficient in the case of small volumes. The possibility to change the probe tip and thus the emitting surface and the resulting UI represents the major advantage of this system. Moreover, their piezoelectric transducers are bonded to the probe which is directly immersed in the liquid medium. This ensures a minimal ultrasonic energy loss and higher UI compared with the other ultrasonic systems. Another horn-based system called cup-horn system has been developed. In this system, the ultrasonic probe is immersed from below contrarily to the sonotrode system described above. Recently some continuous-flow apparatuses have also been developed (Fig. 2.4D). This system provides a mixture of the pumped sample at atmospheric or high pressure to conduct manosonication. It can also be used to conduct manothermosonication owing to the presence of a double mantle to circulate water for controlling the temperature (Fig. 2.4D).

2.2.2 Ultrasound techniques at industrial scale Both the types of devices for high power US (bath and probe systems) are widely used industrially. The selection of the US system will depend on the desired purpose. Both continuous and batch US systems were developed at industrial scale. REUS company has developed reactors from 30 to 1000 L (Fig. 2.5): 30
50 L for pilot scale and 500
1000 L for industrial scale. Pump systems, coupled to these reactors, allow samples filling into the ultrasonic bath, the stirring, and samples

Figure 2.5 Industrial ultrasonic batch equipments: 50, 500, and 1000 L (REUS—www. etsreus.com).

Ultrasound technology for food processing, preservation, and extraction

37

Figure 2.6 Industrial ultrasonic continuous equipments (Hielscher—www.hielscher.com).

recovery after US application. Continuous systems have a great potential in the treatment of large amounts with a restrictive volume of reactor, thus providing a maximum power per volume. Hielscher has continuous systems of a wide range of power, from 50 to 400 W for analytical purposes and from 500 to 16,000 W at industrial scales (Fig. 2.6). Ultrasonic baths with large radiating surface and an agitation system have been also developed for industrial applications.

2.3

Applications

The uses of US have increased exponentially in all fields including medical nondestructive scanning, surface cleaning, environmental decontamination, food industry, etc. (Majid, Nayik, & Nanda, 2015). Especially in the past few decades, more attention has been paid to US application for food processing (cleaning, cutting, cooking, etc.), preservation (inactivation of microorganisms and enzymes) and extraction of food ingredients. Some of these potential applications are summarized in Fig. 2.7, and they will be briefly discussed in this section.

2.3.1 Ultrasound in transformation and processing of food US-assisted surface cleaning is a long-established technique which is widely used in food industry (Kentish & Feng, 2014). The ultrasonic cleaning efficiency is closely dependent on the applied frequency. Frequencies of 20
35 kHz have been

38

Green Food Processing Techniques

Figure 2.7 US applications in food processing, preservation, and extraction. US, Ultrasound.

reported to be more appropriate for cleaning heavy and large size components. Higher frequencies (60
80 kHz) are recommended for cleaning delicate surfaces such as optics (Awad, 2011). Power US has been also used for enhancing transformation processes like, degassing, drying, crystallization, cleaning, etc.

Ultrasound technology for food processing, preservation, and extraction

39

Table 2.4 Examples of ultrasound (US) application in transformation and food processing. Process

Product

Treatment conditions

Reference

Cutting

Cheese

Arnold, Leiteritz, Zahn, and Rohm (2009)

Degassing

Milk

Guillotine sonotrode, 40 kHz, cutting velocity: 2500 mm/min, amplitude: 12 μm 20 kHz, pulsed US (1 s/ 1 s), 20 C, 3 min

Emulsification

Cheese aroma

Crystallization and freezing Cooking

Milk fat Meat

Drying

Carrot

Filtration

Industrial wastewater

Ultrasonic probe, 20 kHz, 120
200 W, 50 C 20 kHz; 5, 20, 30, and 50 W; 5 and 10 s pulses Tekmar sonic disrupter, 20 kHz, 1 kW Stepped-plate transducer, 20 kHz; 155 and 163 dB; 60 C, 90 C, and 115 C Ultrasonic transducers integrated to the membrane module, 27, 40, and 200 kHz, 10 s, ambient temperature

Villamiel, Verdurmen, and de Jong (2005) Mongenot, Charrier, and Chalier (2000) Martini, Suzuki, and Hartel (2008) Pohlman, Dikeman, Zayas, and Unruh (1997) Gallego-Jua´rez, Rodriguez-Corral, Ga´lvez Moraleda, and Yang (1999) Kyllo¨nen, Pirkonen, Nystro¨m, NuortilaJokinen, and Gro¨nroos (2006)

(Charoux, Ojha, O’Donnell, Cardonic, & Brijesh, 2017; Chemat & Khan, 2011; Jambrak, 2012; Majid et al., 2015). This wide range of US applications is related to the wide range of frequencies and power. Table 2.4 presents some examples of US application in transformation and food processing. Ultrasonic cutting is a sizereduction unit operation in which ultrasonic vibrational energy is combined with the mechanical effect of conventional blade (cutting knife) (Kentish & Feng, 2014). US cutting provides better results compared to conventional techniques (less aggressive technique, undisturbed product, etc.). US-assisted degassing is a well-known application which can be obviously visible when applying US on an aqueous solution in an ultrasonic bath. In the food industry, this method can be used to degas carbonated beverages (beer, sodas, etc.) before bottling to preserve their organoleptic properties. However, ultrasonic degassing uses may be limited to liquid products with low viscosity where the propagation of the ultrasonic wave is easy contrarily to viscous food products (melted chocolate, fruits syrups, etc.) (Chemat & Khan, 2011). Power US has also been proved to be effective in the formation of emulsions. This method is widely used in food industry, like the preparation of mayonnaise and ketchup. This method provides more homogenous droplets size compared to conventional techniques. Moreover, it ensures better sanitary environment contrarily to conventional

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Green Food Processing Techniques

homogenizers and microfluidizers. Interestingly, US can also be used to promote the separation of oil/water phases (Kentish & Feng, 2014). Power US is also used in sonocrystallization and freezing. It has been shown to enhance the nucleation of crystals from solution. The main advantages of US application include a faster nucleation, smaller crystals sizes, at lower solids concentrations and/or higher temperatures, or without the need for the addition of seeding agents or antisolvents (Kentish & Feng, 2014). As for US cooking, it provides greater cooking speed, moisture retention, and energy efficiency. This method was mainly used for meat cooking, and it has been shown to improve the textural properties of the cooked meat compared to that of the conventionally cooked meat (Chemat & Khan, 2011; Kentish & Feng, 2014). Ultrasonic drying can be an alternative to overcome the shortcomings of conventional techniques particularly the use of high temperatures which can cause the degradation of food nutritional and organoleptic properties (color, taste, etc.) (Chemat & Khan, 2011). This technique has been used in the case of many food products such as powdered milk, cheese, meat, vegetables. As for ultrasonically assisted filtration, it has been used for the treatment of industrial wastewater that is generally considered difficult to process (Chemat & Khan, 2011).

2.3.2 Applications of ultrasound in preservation of food Microorganisms and enzymes are the major causes of food deterioration. Microorganisms growth in food products lead to the degradation of food qualities and may also cause health problems. Enzymes, present naturally in food, break down the nutrients, for example, the breakdown of fats by lipases or of proteins by proteases (Chemat & Khan, 2011). Power US has been reported to inactivate microbial population and to affect the enzymatic activity. This method has been applied in many food products (juices, dairy products, water, meat, etc.). Some examples of US application for food preservation are presented in Table 2.5. However, US efficiency is highly dependent on the resistance level of the treated microorganisms/ enzymes. Spores appear to be more resistant than vegetative forms (Mason et al., 2003). Gram-positive bacteria are more resistant than Gram-negative bacteria. Their higher resistance to the ultrasonic field could be explained by the thickness and the constitution of their cell walls (cross-linking of peptidoglycan and teichoic acid) (Ojha, Mason, O’Donnell, Kerry, & Tiwari, 2017). Viruses have a high resistance level (Kentish & Feng, 2014). As for enzymes, they are reported to be inactivated by US due to a depolymerization effect. However, the effectiveness of this depolymerization varies (Mason et al., 2003). To reach a higher inactivation rate, it is recommended to use US in combination with heat (thermosonication) or pressure (manosonication) or both (manothermosoncation) (Chemat & Khan, 2011; Jiranek, Grbin, Yap, Barnes, & Bates, 2008). As presented in Table 2.6, the combination of heat and US is more efficient in killing spores than sonication. Manothermosonication is much more efficient since it is able to kill spores and to inactivate enzymes (Table 2.6).

Ultrasound technology for food processing, preservation, and extraction

41

Table 2.5 Experiences using ultrasound in food preservation. Microorganism

Medium

Treatment conditions

Reference 

Sonication, 33 kHz, 25 C, 60 min Sonication, 20 kHz, 44 C, 30 min

Gani et al. (2016)

Milk

Thermosonication 1 pulse electric field, 24 kHz, 400 W, 55 C, 2.5 min

Escherichia coli

Phosphate buffer

Pichia fermentans

Tomato juice

Sonication Manosonication Thermosonication Manothermosonication 20 kHz, 100 W, 40 C
61 C, 100
500 kPa, 0.25
4 min Sonication, 20 kHz, 0.33
0.81 W/mL, 2
10 min

Noci, WalklingRibeiro, Cronin, Morgan, and Lyng (2009) Lee, Zhou, Liang, Feng, and Martin (2009)

Salmonella enterica, serovar Enteritidis

Water

Peroxidase

Watercress

Lysosyme

Phosphate buffer

Pectinesterase

Lemon

Phenol oxidase and peroxidase

Fresh-cut apple

Bacteria, yeast and mold count Alicydobacillus acidoterrestris spores, Saccharomyces cerevisiae Listeria innocua

Strawberry Apple juice (commercial and natural)

Thermosonication, 24 kHz, 52 C
58 C, 2
10 min Thermosonication, 20 kHz, 125 W, 40 C
92.5 C, 0
2 min Manothermosonication, 20 kHz, 60 C
80 C, 200 kPa Thermosonication, 20 kHz, 40 C
90 C, 63 min Sonication 1 ascorbic acid 40 kHz

Ferrario, Alzamora, and Guerrero (2015)

Adekunte, Tiwari, Cullen, Scannell, and O’Donnell (2010) Cabeza et al. (2010)

Cruz, Vieira, and Silva (2006)

Manas, Munoz, Sanz, and Condon (2006) Kuldiloke, Eshtiaghi, Zenker, and Knorr (2007) Jang and Moon (2011)

Table 2.6 Effects of ultrasound (US) in combination with heat and pressure. Inactivation by/of

Vegetative cells

spores

Enzymes

US alone US and heat (TS) US and heat and pressure (MTS)

1 1 1

2 1 1

2 2 1

TS, Thermo-Sonication; MTS, Mano Thermo Sonication.

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Green Food Processing Techniques

2.3.3 Applications of ultrasound in extraction Natural products such as plant primary (proteins, sugars and lipids) and secondary metabolites (antioxidants, essential oils, pigments, etc.) are widely used in food industry. Before such substances can be used as food ingredients, they have to be extracted from their containing matrices. Conventional techniques of solid
liquid extraction present various shortcomings (degradation of active thermolabile compounds, use of huge quantities of energy, water and petroleum solvents, generation of large quantities of waste, etc.). US-assisted extraction (UAE) is considered as a “new” alternative technology which can overcome these shortcomings. Many studies showed the positive contribution of power US in terms of extraction yields, selectivity, reduced solvent consumption, and waste/CO2 emissions (Mason et al., 2011). Table 2.7 summarizes some examples of US application in extraction of natural ingredients (flavors and fragrances, antioxidants, lipids, metals, etc.). The number of companies using US, as a technique for the extraction of food ingredients, has increased significantly. Arkopharma is a French company specialized in food supplements based on plant extracts. This company has recently started to use US instead of conventional maceration. For this company, ultrasound is an effective technology which provides better yields of extraction, enhances the selectivity, and reduces time and temperature. The number of companies using US, as a technique for the extraction of food ingredients, has increased significantly. Arkopharma is a French company specialized in food supplements based on plant extracts. This company has recently started to use US instead of conventional maceration. Their ultrasonic reactor (REUS, France) is presented in Fig. 2.8. For this company, US was proved to be an effective technology which provides better yields of extraction, enhances the selectivity and alloys the use of moderate temperatures. Compared to conventional procedure, US provides a performances gain about 73% for all tested medicinal plants (Fig. 2.9).

2.4

Comprehension of ultrasound-induced mechanisms

This section aims to understand the mode of action of US in the most common applications for food processing, food preservation, and for the extraction of food ingredients. Even though each process application has its particularities, US-related impacts are generally attributed to the cavitation phenomenon and the resulting mechanical and sonochemical effects. The generated impacts are closely dependent on the medium where the cavitational bubbles are generated. In the case of homogeneous liquid systems, there are three active zones where US may have an important impact on this homogeneous system. These zones are presented in Fig. 2.10. As shown in Fig. 2.10, the imploding bubble itself can be considered as a sonoreactor with highly extreme conditions of temperatures and pressures. Any species entering to the cavitational bubble during its collapse would be submitted to these

Table 2.7 Examples of ultrasound (US) application in extraction. Natural ingredient

Matrix

Analyte

Treatment conditions

Reference

Flavors and fragrances

Vanilla

Vanillin

Sharma et al. (2006)

Greek saffron

Safranal

US horn, 20 kHz, 750 W, 25 C, EtOH or EtOH/ H2O 1
2 min Batch, 35 kHz, 25 C, H2O: Et2O. 5 3 10 min

Carvone-rich plants Extra virgin olive oil

Flavor compounds Polyphenols

Green tea Cocos nucifera

Polyphenols, amino acid, and caffeine Phenolic compounds

Red raspberries Citrus peel Pomegranate peel

Anthocyanins Phenolics Antioxidants

Tomato pomace

Nannochloropsis spp. microalgae

Carotenoids (all-translycopene, bcarotene) Antioxidants (carnosic acid, ursolic acid) Phenolic compounds and chlorophylls

Palm-pressed fiber

Phospholipids

Trichosporon oleaginosisus yeast and oleaginous fungus (SkF5)

Lipids

Antioxidants

Rosemary

Lipids

DMSO, Dimethylsulfoxide.

US probe, 20 kHz, 200 W, 70% EtOH US horn, 20 kHz, 400 W, n-hexane, amplitude 10%, duty cycle: 30%, flow rate: 2.4 mL/min Batch, 40 kHz, water US cleaning bath, 25 kHz, 150 W, EtOH/H2O (50/50), pH 6.5 US horn, 22 kHz, 650 W, 1.5 M HCl-95% ethanol US cleaning bath, 60 kHz, 80% methanol US probe (20 kHz, 1.267 cm2) Pulse 5 5 s on, 5 s off, 25 C, 60 min ratio: water/peel, 50/1 (w/w) US probe (20 kHz, 13 mm), 25 C, t . 10 min, hexane/ethanol (50:50, v/v) US bath, 150 W, US reactor, US probe (1 kW), EtOH/H2O, 90/10 (v/v), 40 C, 30 min US probe, 24 kHz 100
400 W, T , 60 C, t , 30 min, m 5 250 g suspended in ethanol and DMSO US probe, 24 kHz, 400 W, hexane
isopropanol
water US horn (520 kHz, 40 W) US bath (50 Hz, 2800 W), T 5 25 C, t 5 15 min, solvent: chloroform/methanol (1:2, v/v)

Kanakis, Daferera, Tarantilis, and Polissiou (2004) Da Porto and Decorti (2009) Ruiz-Jime´nez and Luque De Castro (2003) Xia, Shi, and Wan (2006) Rodrigues, Pinto, and Fernandes (2008) Chen et al. (2007) Ma, Chen, Liu, and Ye (2009) Pan, Qu, Ma, Atungulu, and McHugh (2012) Luengo, Condo´n-Abanto, ´ lvarez, and Raso Condo´n, A (2014) Jacotet-Navaro et al. (2015) Parniakov et al. (2015)

Chua et al. (2009) Zhang, Yan, Tyagi, Drogui, and Surampalli (2014)

44

Green Food Processing Techniques

Figure 2.8 Ultrasonic reactor used by Arkopharma (Carros, Grance).

Figure 2.9 An example of food supplements commercialized by Arkopharma obtained by (A) conventional maceration and (B) ultrasound-assisted extraction.

Ultrasound technology for food processing, preservation, and extraction

45

Figure 2.10 Sites of chemical reactions in aqueous medium subjected to acoustic cavitation according to the hot spot theory.

extreme physical conditions. The chemical reactivity of the bubble should also be taken into consideration. A noticeable production of radicals is mainly observed in the case of aqueous medium where the extreme conditions (P, T) are able to cause the rupture of O
H bond and the dissociation of water into hydroxyl radicals (OH and H ) and hydrogen atoms according to the following reaction below: H2O!OH 1 H (Chemat et al., 2008; Mason et al., 2003; Wood et al., 2017). These radicals can contribute to some secondary reactions such as the generation of H2O2 in the presence of oxygen and thus suggesting the necessity to control the composition of dissolved gases. Moreover, OH radicals are strongly oxidative, implying that any chemical species dissolved in the aqueous solution can be subject to chemical interactions with these radicals. Sonochemical effects are also privileged at the bubble
liquid interface where temperature and pressures are also high. The rapid collapse of bubbles generates also high shear forces into the surrounding medium. At this zone, mechanical effects predominate (Cravotto & Cintas, 2006; Vyas & Ting, 2018; Wu et al., 2013). Bubbles formation is at the origin of many applications in food processing such as degassing of liquid products containing gases as a mixed condition, such as dissolved oxygen, carbon dioxide, and nitrogen gas (Chemat & Khan, 2011). As for heterogeneous liquid
liquid systems, the major impact of US owes to its ability to form fine emulsions related to the high shear forces resulted from US application. These shear forces have long been considered as the main physical impact of USs creating turbulence and oscillations within the liquid (Kentish & Feng, 2014; Leong et al., 2011; Vilkhu, Mawson, Simons, & Bates, 2008). This mechanism has been valorized in the creation of emulsions and in the mixing of complex solutions (Ashokkumar, 2011; Mason, Paniwnyk, & Lorimer, 1996). However, for most of US potential applications, we are in presence of heterogeneous solid
liquid systems (cleaning, drying, cooking, inactivation of

G

G

G

G

G

46

Green Food Processing Techniques

microorganisms and/or enzymes, solid
liquid extraction, etc.). In the case of heterogeneous cavitation, microjets of extremely high pressure and temperature are directed toward solid surface (Fig. 2.3). Solid
liquid systems may take the form of liquid solution with small particles in suspension. When subjected to an ultrasonic field, suspended particles decrease in size. An efficient dispersion of these particles is also noticed owing to their rapid motion and the high shear forces generated into the medium during the ultrasonic wave propagation. This is commonly used for solid dispersion into solvent and for the enhancement of their solubility (Chemat, Rombaut, Sicaire et al., 2017). Shear forces, generated by acoustic streaming, are also at the origin of US-assisted cleaning, since they allow the removal of particles from solid surfaces (Kentish & Feng, 2014). US has been also proved to enhance mass and heat transfer. Diffusion at the solid
liquid boundary is significantly increased when applying US. These effects are related to the rapid contraction/rarefaction cycles generated during the ultrasonic wave propagation as well as the resulting shear forces (Kentish & Feng, 2014). These effects resulted in the application in many food processes such as cooking and drying. Concerning the inactivation effect of US, enzymes can be affected through three possible mechanisms which can act individually or combined (1) thermal inactivation (hot spot theory), (2) free radicals, and (3) mechanical forces (shear forces and shock waves) (Cravotto & Cintas, 2006). Ojha et al. (2017) have proposed a “sonoporation” mechanism behind the ultrasonic microbial inactivation. The different possible interactions of cavitational bubbles with cell membrane are presented in Fig. 2.11. Sonoporation mechanism is defined as the formation of cavities or pores on cell membrane due to sonication (Ojha et al., 2017). Interestingly, according to this study, US can have positive or negative effects on microorganisms depending on the sonoporation level. A low level of sonoporation, US has been reported to enhance mass transfer of substrates or reagents across cell membrane and removal of by-products of cellular metabolism and thus improves microbial growth. However, higher level of sonoporation causes irreversible physical disruption of cell membrane leading to the leakage of cellular content and the cell death (Ojha et al., 2017). This implies that the optimization of US parameters is of a great importance and should be adapted to desired purpose. Solid
liquid extraction represents one of the most common US applications in the food field. The controlling mechanism of UAE is generally attributed to mechanical, cavitation, and thermal effects during bubbles collapse (Awad et al., 2012; Chemat & Khan, 2011; Veillet et al., 2010). This results in disruption of cell walls, particle size reduction, and enhanced mass transfer across cell membranes (Chemat, Rombaut, Meullemiestre et al., 2017; Vinatoru, 2001; Vilkhu et al., 2008). Shear forces and the resulting interparticle collisions have also been reported to accelerate the diffusion of matrix-contained compounds (Mason et al., 2003). Shirsath et al. have defined cell disruption and breaking as the major mechanism of action of US when applied on plant solid
liquid extraction. As presented in Fig. 2.12, US generates cracks into plant cell walls. These cracks increase the

Ultrasound technology for food processing, preservation, and extraction

47

Figure 2.11 Mechanism of sonoporation involving various stages.

permeability of plant tissues and thus enhance the solvent penetration into the inner plant tissues as well as the release of their contained compounds (Shirsath, Sonawane, & Gogate, 2012). However, US mode of action appear to be a much more complicated process than that proposed by Shirsath et al. Indeed, completely

48

Green Food Processing Techniques

Figure 2.12 The mechanism of cell wall disruption (A) breaking of cell wall due to cavitation, (B) diffusion of solvent into the cell structure.

different physical impacts can be observed, depending on US parameters and the nature of plant matrices. These different mechanisms were recently summarized in a review published by Chemat, Rombaut, Sicaire et al. (2017). As explained in this review, in the case of solid
liquid UAE, the implosion of cavitational bubbles generate extreme conditions of pressure and temperature and microjets toward the plant surface. Depending on their structure, cell walls can be slightly or highly impacted. The induced impacts can then range from removing small particles or structures from the surface (erosion) to creating pores (sonoporation) or even deep fractures within the raw material (fragmentation). These different mechanical impacts were previously reported by many researchers. The first US mechanism to be reported is local erosion which has been firstly shown by Degrois, Gallant, Baldo, and Guilbot (1974) on starch grains where numerous pits have been identified on the surface after US application (Degrois et al., 1974). This effect was also observed in the case of boldo leaves (Petigny, Pe´rino-Issartier, Wajsman, & Chemat, 2013) and black tea leaves (Both, Chemat, & Strube, 2014). Concerning sonoporation, it was mainly noticed in the biological field where the shock waves and the extremely high physical conditions can disrupt cellular structures of living cells (microorganisms, spores, enzymes, etc.) and lead to the cell lysis. For instance, Meullemiestre, Breil, Abert-Vian, and Chemat (2016) have observed US-induced pores on wet yeast surface subjected to US. As for fragmentation of friable solids, it was reported by several authors. This mechanism can be attributed to the shock waves created into the liquid and the interparticle collisions of particles forced to very rapid motion (Chemat, Rombaut, Sicaire et al., 2017). Induced impacts, namely, erosion, sonoporation, and fragmentation, enhance solvent penetration to inner structures and in meantime favor the release of targeted compounds (Assamia, Pingret, Chemat, Meklatia, & Chemat, 2012; Liu, Zeng,

Ultrasound technology for food processing, preservation, and extraction

49

Sun, & Han, 2013; Petigny et al., 2013; Rajewska & Mierzwa, 2017; Soria & Villamiel, 2010). Furthermore, strong shear forces seem to further accelerate exchange between raw material and the surrounding liquid. Shear forces and turbulences result from the propagation of cavitation bubble within the fluid. This mechanism is of great interest in several applications such as mixing or emulsification. These four mechanisms result in “the increase of depth and velocity of penetration of solvent within plant inner structures,” referring to the ultrasonic capillary effect (Chemat, Rombaut, Sicaire et al., 2017). This mechanism is associated to the increase in the swelling index and the rehydration of plant material which enhances the extraction performances. A total detexturation was reported in the case of caraway seeds subjected to US field (Chemat, Lagha, Ait Amar, Bartels, & Chemat, 2004). In this case, cell structures were completely deformed and altered. Most of studies dealing with the USinduced mechanism proposed a single physical mechanism behind the US observed effects. Nevertheless, a study recently published by Khadhraoui et al. (2018) proved that US impacted Rosemary leaves not by a single mechanism but by a chain detexturation mechanism where six physical impacts occurred in a special order: local erosion, shear forces, sonoporation, fragmentation, capillary effect, and detexturation. This special order is presented in Fig. 2.13. Local erosion of some branches of nonglandular trichomes was firstly noticed after 10 min of US application. Removal of hairs continued during the treatment leading to their total abrasion after 20 min of US treatment. Shear forces, generated by the propagation of ultrasonic waves, resulted in deformations on the smooth heads of glandular trichomes of abaxial and adaxial surfaces. This mechanical effect was firstly noticed after 15 min of US application. Shear forces weakened glandular trichomes envelopes generating microfractures and hence promoting access to their chemical content. This physical impact was identified as sonoporation mechanism observed after 20 min of US application. Several deep cracks were then observed on the adaxial cuticular layer and on epidermal cells. This implied that 30 min of US caused the fragmentation of Rosemary leaf. Even though this effect seemed to be mainly localized at the surface, it caused disturbances within the inner tissues, particularly the palisade and spongy parenchyma cells. These different mechanisms (erosion, sonoporation, and fragmentation) contributed to better yields of extraction by increasing the surface area contact between water and leaf components. Overall, these openings and disruptions improved solvent penetration to inner structures which hydrated the leaf and swelled it. This sonocapillary effect was noticed after 40 min of treatment. Meanwhile, contained components were expelled and forced to migrate to the surrounding water. Twenty additional minutes of US treatment led to the total detexturation of Rosemary leaf. Cells shrinkage was remarkably observed (Fig. 2.13). Significant degradation of cell walls was also noticed. Inner tissues appeared to have been dramatically damaged and completely emptied of their contents.

50

Green Food Processing Techniques

Figure 2.13 Chain reaction mechanism of rosemary leaf detexturation during US treatment. AC, Adaxial cuticle; AE, adaxial epidermal cells; BC, abaxial cuticle; BE, abaxial epidermal cells; GT, glandular trichomes; NGT, nonglandular trichomes; US, ultrasound.

Ultrasound technology for food processing, preservation, and extraction

2.5

51

Future trends

US in food processing is increasingly efficient at directly transferring knowledge into technology for commercial development. US makes use of physical and chemical phenomena that are fundamentally different from those applied in conventional processing, preservation, and extraction techniques. US systems developed to date clearly indicate that this technology offers net advantages in terms of yield, selectivity, operating time, energy input, and preservation of thermolabile compounds.

References Adekunte, A. O., Tiwari, B. K., Cullen, P. J., Scannell, A. G. M., & O’Donnell, C. P. (2010). Effect of sonication on colour, ascorbic acid and yeast inactivation in tomato juice. Food Chemistry, 122(3), 500
507. Arnold, G., Leiteritz, L., Zahn, S., & Rohm, H. (2009). Ultrasonic cutting of cheese: Composition affects cutting work reduction and energy demand. International Dairy Journal, 19, 314
320. Ashokkumar, M. (2011). The characterization of acoustic cavitation bubbles—An overview. Ultrasonics Sonochemistry, 18(4), 864
872. Assamia, K., Pingret, D., Chemat, S., Meklatia, B. Y., & Chemat, F. (2012). Ultrasound induced intensification and selective extraction of essential oil from Carum carvi L. seeds. Chemical Engineering and Processing, Process Intensification, 62, 99
105. Awad, S. B. (2011). High-power ultrasound in surface cleaning and decontamination. In H. Feng, G. Barbosa-Canovas, & J. Weiss (Eds.), Ultrasound technologies for food and bioprocessing. Food engineering series (pp. 545
558). New York: Springer. Awad, T. S., Moharram, H. A., Shaltout, O. E., Asker, D., & Youssef, M. M. (2012). Applications of ultrasound in analysis, processing and quality control of food: A review. Food Research International, 48, 410
427. Bermu´dez-Aguirre, D., & Barbosa-Ca´novas, G. (2011). Power ultrasound to process dairy products. In H. Feng, G. Barbosa-Canovas, & J. Weiss (Eds.), Ultrasound technologies for food and bioprocessing (pp. 445
466). New York: Springer. Both, S., Chemat, F., & Strube, J. (2014). Extraction of polyphenols from black tea
conventional and ultrasound-assisted extraction. Ultrasonics Sonochemistry, 21, 1030
1034. Cabeza, M. C., Ca´rcel, J. A., Ordo´n˜ez, J. A., Cambero, I., De la Hoza, L., Garcia, M. L., & Benedito, J. (2010). Relationships among selected variables affecting the resistance of Salmonella enterica, serovar Enteritidis to thermosonication. Journal of Food Engineering, 98, 71
75. Carrillo-Lopez, L., Alarcon-Rojo, A., Luna-Rodriguez, L., & Reyes-Villagrana, R. (2017). Modification of food systems by ultrasound. Journal of Food Quality, 2017, 1
12. Charoux, C. M. G., Ojha, K. S., O’Donnell, C. P., Cardonic, A., & Brijesh, K. (2017). Applications of airborne ultrasonic technology in the food industry. Journal of Food Engineering, 208, 28
36. Chemat, F., & Khan, M. K. (2011). Applications of ultrasound in food technology: Processing, preservation and extraction. Ultrasonics Sonochemistry, 18(4), 813
835.

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902. Cruz, R. M. S., Vieira, M. C., & Silva, C. L. M. (2006). Effect of heat and thermosonication treatments on peroxidase inactivation kinetics in watercress (Nasturtium officinale). Journal of Food Engineering, 72, 8
15. Da Porto, C., & Decorti, D. (2009). Ultrasound-assisted extraction coupled with under vacuum distillation of flavour compounds from spearmint (carvone-rich) plants: Comparison with conventional hydrodistillation. Ultrasonics Sonochemistry, 16(6), 795
799. Degrois, M., Gallant, D., Baldo, P., & Guilbot, A. (1974). The effects of ultrasound on starch grains. Ultrasonics, 12, 129
132. Ferrario, M., Alzamora, S. M., & Guerrero, S. (2015). Study of the inactivation of spoilage microorganisms in apple juice by pulsed light and ultrasound. Food Microbiology, 46, 635
642. Gallego-Jua´rez, J. A., Rodriguez-Corral, G., Ga´lvez Moraleda, J. C., & Yang, T. S. (1999). A new high intensity ultrasonic technology for food dehydration. Drying Technology, 17 (3), 597
608. Gani, A., Baba, W. N., Ahmad, M., Shah, U., Khan, A. A., Wani, I. A., . . . Gani, A. (2016). Effect of ultrasound treatment on physico-chemical, nutraceutical and microbial quality of strawberry. LWT—Food Science and Technology, 66, 496
502. Jacotet-Navaro, M., Rombaut, N., Tixier-Fabiano, A. S., Danguien, M., Bily, A., & Chemat, F. (2015). Ultrasound versus microwave as green processes for extraction of rosmarinic, carnosic and ursolic acids from rosemary. Ultrasonics Sonochemistry, 27, 102
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449. Jiranek, V., Grbin, P., Yap, A., Barnes, M., & Bates, D. (2008). High power ultrasonics as a novel tool offering new opportunities for managing wine microbiology. Biotechnology Letters, 30(1), 1
6. Kanakis, C. D., Daferera, D. J., Tarantilis, P. A., & Polissiou, M. G. (2004). Qualitative determination of volatile compounds and quantitative evaluation of safranal and 4hydroxy-2,6,6-trimethyl-cyclohexene-1-carboxaldehyde (HTCC) in Greek saffron. Journal of Agricultural and Food Chemistry, 52, 4515
4521. Kentish, S., & Ashokkumar, M. (2011). The physical and chemical effects of ultrasound’. In H. Feng, G. Barbosa-Canovas, & J. Weiss (Eds.), Ultrasound technologies for food and bioprocessing (pp. 1
12). New York: Springer. Kentish, S., & Feng, H. (2014). Applications of power ultrasound in food processing. Annual Review of Food Science and Technology, 5, 263
284. Kentish, S., Wooster, T. J., Ashokkumar, M., Balachandran, S., Mawson, R., & Simons, L. (2008). The use of ultrasonics for nanoemulsion preparation. Innovative Food Science and Emerging Technologies, 9, 170
175. Khadhraoui, B., Turk, M., Fabiano-Tixier, A., Petitcolas, E., Robinet, P., Imbert, R., . . . Chemat, F. (2018). Histo-cytochemistry and scanning electron microscopy for studying spatial and temporal extraction of metabolites induced by ultrasound. Towards chain detexturation mechanism. Ultrasonics Sonochemistry, 42, 482
492. Kuldiloke, J., Eshtiaghi, M., Zenker, M., & Knorr, D. (2007). Inactivation of lemon pectinesterase by thermosonication. International Journal of Food Engineering, 3(2), 1
8. Kyllo¨nen, H., Pirkonen, P., Nystro¨m, M., Nuortila-Jokinen, J., & Gro¨nroos, A. (2006). Experimental aspects of ultrasonically enhanced cross-flow membrane filtration of industrial wastewater. Ultrasonics Sonochemistry, 13, 295
302. Laugier, F. (2007). Les ultrasons en proce´de´s polyphasiques: Transfert gaz-liquide et re´action liquide-liquide (Title of doctor of science). L’institut national polytechnique de Toulouse. Lauterborn, W., & Kurz, T. (2010). Physics of bubble oscillations. Reports on Progress in Physics, 73(10), 73
88. Lee, H., Zhou, B., Liang, W., Feng, H., & Martin, S. E. (2009). Inactivation of Escherichia coli cells with sonication, manosonication, thermosonication, and manothermosonication: Microbial responses and kinetics modelling. Journal of Food Engineering, 93, 354
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Pingret, D., Fabiano-Tixier, A. S., & Chemat, F. (2013a). Ultrasound-assisted extraction. In M. A. Mauricio, & M. J. Rostagno (Eds.), Natural product extraction: Principles and applications (pp. 89
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16. Wang, L., & Weller, C. L. (2006). Recent advances in extraction of nutraceuticals from plants. Trends in Food Science and Technology, 17, 300
312.

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Wood, R. J., Lee, J., & Bussemaker, M. J. (2017). A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions. Ultrasonics Sonochemistry, 38, 351
370. Wu, T. Y., Guo, N., Teh, C. Y., & Hay, J. X. W. (2013). Theory and fundamentals of ultrasound. In T. Y. Wu, N. Guo, C. Y. Tech, & J. X. W. Hay (Eds.), Advances in ultrasound technology for environmental remediation. Briefs in molecular science (pp. 5
12). Dordrecht: Springer. Xia, T., Shi, S., & Wan, X. (2006). Impact of ultrasonic-assisted extraction on the chemical and sensory quality of tea infusion. Journal of Food Engineering, 74, 557
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261.

Further reading Nikitenko, S., & Chemat, F. (2015). Ultrasound in process engineering: New look at old problems. In M. Poux, P. Cognet, & C. Gourdon (Eds.), Green process engineering from concepts to industrial applications (pp. 145
165). New York: CRC press.

Supercritical fluid processing and extraction of food

3

Renata Vardanega1, Grazielle Na´thia-Neves1, Priscila C. Veggi2 and M. Angela A. Meireles1 1 LASEFI/DEA/FEA (School of Food Engineering), UNICAMP (University of Campinas), Campinas, Brazil, 2School of Chemical Engineering, Federal University of Sa˜o Paulo (UNIFESP), Diadema, Brazil

3.1

Introduction

The demand for natural food products has increased in recent years due to the increase in population and change in eating habits of modern consumers. This has driven industries to develop not only healthier products but also green processes to ensure the obtainment of products with functional properties without harming the environment. For a long time, food processing has been performed using conventional methods, which generally produce low yields, use large volumes of organic and toxic solvents, require long processing times, and use high temperatures that degrade heat-sensitive compounds, all of which contribute to the increased cost of the final product and the lowered sensory quality and nutritional value (Chemat et al., 2017; Sa´nchez-Camargo, Iba´n˜ez, Cifuentes, & Herrero, 2017). One of the green food processing techniques is the use of supercritical fluids. Currently, the most widely used supercritical fluid in the food, flavor, beverage, and cosmetics/personal care industries is carbon dioxide (CO2) (Attard et al., 2018). This is because supercritical carbon dioxide (scCO2) presents several unique features that make the processes attractive from different points of view: it allows the efficient extraction of food ingredients free of organic solvent; it can be used for food preservation through microbial and enzymatic inactivation; it is an ecofriendly solvent that makes the process sustainable; it is cheap and thus contributes to the economic feasibility of the processes. Further advantages of scCO2 can be found in Fig. 3.1. In this regard, this chapter discusses some of the most important green food processing technologies that use scCO2, including extraction, transformation, and food preservation. The environmental impact of these technologies and their scalability are also discussed.

Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00003-3 © 2019 Elsevier Inc. All rights reserved.

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Figure 3.1 Supercritical CO2 for green food processing.

3.2

Principle, procedures, and influencing factors

This section provides information about the supercritical principle, followed by a description of the procedures involved in some of the main processes using supercritical fluids; finally, the factors that affect the performance of these processes are discussed. Further information covering the advantages and applications of each process are provided in Sections 3, 4, and 5.

3.2.1 Principle Supercritical fluid processing is based on the use of supercritical fluids as an alternative to organic solvents (Chemat et al., 2017). A fluid is in the supercritical state when it reaches a pressure and temperature above its critical point; at this state, there is no sudden change in its properties (Brunner, 2005) since there is no separation between the liquid and gaseous phases, and therefore there is no surface tension (Sa´nchez-Camargo et al., 2017). The main interesting characteristics of supercritical fluids are the following: its viscosity is like that of the gases, its density is similar to that of liquids, and its diffusivity is between those of the liquid and gaseous states, which favors the extraction of intracellular compounds. It is noteworthy that small variations in solvent density lead to large changes in the dielectric constant, solubility parameter, and partition coefficient (Attard et al., 2018), which result in the enhanced mass transfer rate of solutes during extraction (Ameer, Shahbaz, & Kwon, 2017). Therefore supercritical fluids often provide optimum conditions for

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both experiments and processes, making them ideal, clean solvents for processing of natural materials (Chemat et al., 2017). Although several fluids have been used in supercritical conditions, carbon dioxide is by far most attractive and has been most widely used in food applications. This is because carbon dioxide has mild critical conditions (Tc 5 31 C and Pc 5 7.38 MPa), is available in large quantities, is nontoxic, nonflammable, and cheap, is relatively inert to several media, and is a gas at atmospheric pressure (Attard et al., 2018; Chemat et al., 2017; Da Silva, Rocha-Santos, & Duarte, 2016). Because of these characteristics, the European Food Safety Authority and the United States Food and Drug Administration have assigned CO2 as a generally recognized as safe solvent. Even though scCO2 behaves as a rather weak “nonpolar” solvent, some compounds have a low degree of solubility in scCO2, making CO2 unfavorable to use alone (Pereira & Meireles, 2010). To overcome this limitation, it is often common to add a polar cosolvent (also called modifier) to improve the solubility and recovery rates of polar substances. The most effective polar modifiers are usually acetonitrile, acetone, methanol, ethyl ether, ethanol, and water (Xu et al., 2017). However, due to its low toxicity, ethanol has been reported to be a better modifier than the others (Khaw, Parat, Shaw, & Falconer, 2017; Machado, Pereira, Nunes, Padilha, & Umsza-Guez, 2013; Xu et al., 2017).

3.2.2 Procedures 3.2.2.1 Extraction Among the possible applications for supercritical fluid processing, supercritical fluid extraction (SFE) is by far most widely used at the industrial scale. For the SFE, the required equipment comprise a solvent tank, a pump to pressurize the fluid, an extraction vessel with controlled temperature where the solid material is placed in a restrictor to maintain the high pressure inside the system, and a trapping vessel (Iban˜ez, Mendiola, & Castro-Puyana, 2012). A typical SFE process from solids comprises two main processing steps: extraction of the soluble substance from the raw material in the supercritical solvent and separation of the extract from the solvent. The solid material is placed in the extraction vessel, forming a fixed bed. The extraction conditions are maintained by operating a pressure release valve and temperature controllers attached to the extraction vessel. Thus the supercritical solvent flows uniformly through the bed of solid particles until the desired extraction conditions are reached. The solvent and matrix are maintained in contact during a specified period to reach the equilibrium composition (Ameer et al., 2017; Brunner, 2005). In the separation step, the solvent power is reduced, and the compounds of interest dissolved in the fluid are trapped during decompression (Ameer et al., 2017). The possibility of manipulating the operational conditions of temperature and pressure is one of the most important advantages of the SFE process because it enables the selective extraction and precipitation of target compounds. Therefore the proper conditions to be used depend on the specific compound or compound family to be recovered.

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3.2.2.2 Particle formation In addition to extraction, supercritical fluids have also been used for the transformation and preservation of foods, which will be further discussed in Sections 4 and 5. Particle formation using supercritical fluids have also reached the industrial scale with several different techniques based on different principles according to the role of scCO2 in the process (Fig. 3.2); these techniques are classified as follows: solvent, antisolvent, solute, or cosolvent. The description of these techniques can be found in several papers that review the fundamentals of the different techniques (Cocero, Martı´n, Mattea, & Varona, 2009; Gomes, Santos, & Meireles, 2012; Knez, ˇ Hrnˇciˇc, & Skerget, 2015; Reverchon, Adami, Cardea, & Porta, 2009; Silva & Meireles, 2014; Temelli, 2018; Weidner, 2009). When scCO2 acts as a solvent, the active compound or mixture containing the active compound and a wall material are first solubilized in the supercritical fluid

100

Polyphenols

80

Temperature (°C)

Phospholipids

60

Carotenoids

Triterpenoids Mono-, di-, and triglycerides

40

Diterpenes Sterols/FFA

Tc Phenolics

20

Terpenoids

Pc 10

20

30

40

100

Pressure (MPa)

Figure 3.2 Temperature and pressure conditions for extraction of different classes of compounds. Tc, CO2 critical temperature; Pc, CO2 critical pressure. Source: Adapted from Attard, T. M., Bukhanko, N., Eriksson, D., Arshadi, M., Geladi, P., Bergsten, U., . . . Hunt, A. J. (2018). Supercritical extraction of waxes and lipids from biomass: A valuable first step towards an integrated biorefinery. Journal of Cleaner Production, 177, 684
698.

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and then rapidly expanded in a container at atmospheric pressure using a suitable nozzle. The sudden pressure change causes an abrupt reduction in the solvent power of CO2, and the dissolved material precipitates (Silva & Meireles, 2014). For the processes where scCO2 acts as an antisolvent, the active material is first dissolved in an organic solvent and then placed in contact with the scCO2, which is miscible with the organic solvent and immiscible with the active material. Dissolution of the antisolvent in the organic solvent leads to an expansion of the liquid and a reduction in solvent power and solute solubility, resulting in the precipitation of the active material (Temelli, 2018). In the case of scCO2 as a solute or cosolvent, it is first solubilized in the liquid phase, and then the mixture is depressurized through a nozzle to ambient conditions. This process does not require the active substance to be dissolved in scCO2 because it exploits the cooling phenomenon that occurs due to the Joule
Thomson effect during depressurization through a nozzle, which causes the formation of solid particles (Silva & Meireles, 2014).

3.2.2.3 Extrusion Extrusion assisted by scCO2 (SCFX) has been considered a revolutionary technology for the polymer industry because it allows decreased processing temperature and thus the use of heat-sensitive components (Chauvet, Sauceau, & Fages, 2017). SCFX has been used to promote textural modifications in food matrices. Extruded materials have a porous interior with a smooth external surface. Because scCO2 is soluble in many molten polymers and acts as a plasticizer, its presence in the extruder permits a decrease in the processing temperature to values lower than those of the conventional process (Balenti´c et al., 2017; Chauvet et al., 2017). The basic procedure is described as an injection of pressurized CO2 in the barrel of an extruder. CO2 acts as a removable plasticizer in the metering zone of the extruder, where it modifies the rheological behavior of the melt. Moreover, scCO2 acts as an expansion agent when it suddenly reaches atmospheric pressure at the die exit (Park, Behravesh, & Venter, 1998). This pressure quench is responsible for the supersaturation in the metastable melt phase, leading to the nucleation and growth of CO2 bubbles, and eventually, the final porous 3D structure (Chauvet et al., 2017). It is therefore possible to control pore generation and growth by controlling the operating conditions (Sauceau, Fages, Common, Nikitine, & Rodier, 2011).

3.2.2.4 Fractionation Fractionation can be achieved in the supercritical extraction process from solid matrices (during or after the extraction) or in countercurrent columns operated with supercritical fluids, like liquid
liquid extraction. These strategies can be used when mixtures of several families of compounds are required, and they show different solubilities in scCO2. It takes advantage of the fact that the scCO2 solvent power is easily changed with pressure and temperature (Fornari, Vicente, Va´zquez, Garcı´aRisco, & Reglero, 2012; Reverchon & De Marco, 2006).

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For fractional extraction, the selection of scCO2 power can be explored by adjusting the operational conditions to obtain the selective extraction of the compounds of interest, reducing the coextraction of undesired compounds to a minimum. The extraction can be performed in successive steps that increase CO2 density to obtain the fractional extraction of the soluble compounds contained in the plant matrix. In this way, the most soluble compounds are extracted during the early step, while substances with decreasing solubility in scCO2 are extracted in the successive steps. For a successful extraction, not only does the solubility of the compounds to be extracted and/or of the undesired compounds need to be taken into account, the mass transfer resistance due to the structure of the raw material and specific location of the compounds to be extracted also play an important role (Reverchon & De Marco, 2006). Extract fractionation can also be obtained by operating the extraction in a single stage and the separation step using sequential separators set at different temperatures and decreasing pressures (Pereira & Meireles, 2010). The objective of this operation is to induce the selective precipitation of different compound families as a function of their different saturation conditions in scCO2 (Reverchon & De Marco, 2006). Liquid fractionation achieved by supercritical fluids is generally performed in countercurrent columns operated in continuous mode. Briefly, the feed solution is introduced in the middle or on the top of the column while the supercritical fluid is introduced at the bottom of the column. After an appropriate time of contact between the feed solution and the supercritical fluid, the extract enriched with the target compounds is recovered at the top of the column, and the residual solution (raffinate) is recovered at the bottom.

3.2.2.5 Preservation The preservation of foods by supercritical technology is achieved due to specific properties of scCO2, which enable the inactivation of microorganisms and enzymes. Low viscosity and intermediate diffusivity, combined with the absence of surface tension in the scCO2, allow its rapid penetration into the cells and particles under pressure into a rector chamber, where the food is placed and maintained under determined conditions of temperature and pressure until the end of the process. After the processing time, the CO2 is released and separated from the food material (Chemat et al., 2017; Guimara˜es, Silva, De Freitas, De Almeida Meireles, & Da Cruz, 2018).

3.2.3 Influencing factors Each supercritical process has its own complexities and requires a solid understanding of the thermodynamic and transport phenomena involved for the design and control of product properties and the optimization of each process. However, some characteristics are crucial to be optimized in all the processes, mainly those related to the properties of supercritical fluids. The fluid temperature and pressure are the

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key parameters that govern supercritical processes and affect the thermodynamic and transport properties (de Melo et al., 2014). These parameters directly affect the solvation power since they act on the solvent density. Therefore by controlling the temperature and pressure, the solvation power can be modified. At constant temperature, increasing the pressure results in an increase in the fluid density and solvation power. Moreover, at constant pressure, an increase in temperature reduces the solvent density and its solvation power (Pereira & Meireles, 2010; Talmaciu, Volf, & Popa, 2015). When supercritical fluids are used as a solvent in extraction processes, in addition to the fluid properties, the aspects related to the solid matrix, solute, sample pretreatment, and the dynamic factors also play important roles in process optimization (Talmaciu et al., 2015; Shilpi, Shivhare, & Basu, 2013; Talmaciu et al., 2015). The solid features involve the sample and particle size (and distribution), porosity, nature of matrix, sample conditions (such as the moisture content), and extractable compounds. The important solute characteristics are solubility, volatility, polarity and molecular weight and solute concentration in the solid matrix. The dynamic factors comprise the extraction time, solvent flow rate, solvent-to-feed ratio (S/F), and characteristics of the bed geometry (length to extractor diameter ratio, L/D) (Panza & Beckman, 2004). The particle formation processes add one more challenge to the optimization procedure, knowledge of the nucleation-growth kinetics, which is also crucial for the design and control of particle properties. Furthermore, in all of the processes presented in Fig. 3.3, the phase boundaries need to be crossed in order to form solid particles not only in the supercritical and liquid phases but also in the gas-expanded liquid and solid phases involved, which makes the phase diagrams crucial for the

Figure 3.3 Role of scCO2 in the particle formation techniques.

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success of the processes (Temelli, 2018; Weidner, 2009). In addition, temperature, pressure, nozzle diameter and type (T-mixer or coaxial), depressurization rate, CO2 and feed solution flow rates, and solute concentration have remarkable effects on the formation and size distribution of the particles formed and need to be optimized (Machado et al., 2018; Osorio-Tobo´n, Carvalho, Rostagno, Petenate, & Meireles, 2016). SCFX is a complex process, and it is important to take into consideration process features related to the geometry of the die and the pressure drop induced by the die in addition to the temperature of the process and the concentration of CO2, which acts as a nucleating agent mainly affecting foam density and expansion properties (Chauvet et al., 2017; Park, Baldwin, & Suh, 1995). Finally, the preservation process is mainly affected by the temperature and pressure conditions, along with the processing time and scCO2 volume ratio (Ceni et al., 2016; Silva, Alvarenga, Bargas, Sant’ana, & Meireles, 2018).

3.3

Application in extraction of food ingredients

Ingredients are added during the manufacture of a food product with the purpose of modifying its physical, chemical, biological, or sensory characteristics. In addition to concerns related to consumer welfare, industries have increasingly been developing their production processes on the pillars of sustainability, with minimal damage to the environment. In this sense, the use of supercritical fluids for the extraction of food ingredients has become an excellent option since in addition to obtaining extracts free of organic solvents, it is a clean technology that presents little or no aggression to the environment. The efficient use of scCO2 in the extraction of a range of compounds has been proven by several authors. In addition to scientific research, scCO2 has been widely used in industries such as the extraction of hops and decaffeination of coffee (Attard et al., 2018). However, certain classes of compounds are not easily extracted with scCO2. Due to its low polarity, scCO2 is widely used to extract nonpolar compounds. For the extraction of polar compounds, it is necessary to use polar cosolvents (water, ethanol, methanol, acetone, or water mixed with ethanol) or very drastic extraction conditions to achieve the analyte of interest, which may not be an economically viable option. In addition to polarity, the high content of water present in some raw materials makes extraction with scCO2 difficult (Attard et al., 2018; Chemat et al., 2017; Soquetta, Terra, & Bastos, 2018; Zulkafli, Wang, Miyashita, Utsumi, & Tamura, 2014). In addition to polarity and moisture content, the solubility of CO2 is also affected by the molecular weight of the molecules; the higher the molecular weight is, the lower the solubilities of the compounds are in scCO2 (Attard et al., 2018). Fig. 3.3 illustrates the conditions (pressure and temperature) for the extraction of several classes of compounds. Briefly, the extraction process with supercritical fluids involves five stages: (1) pressurizing; (2) heating or cooling; (3) extraction; (4) separation between solvent

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and extract; and (5) solvent recycling (Albarelli, Santos, Cocero, & Meireles, 2018). In the process of SFE from solid matrices, the supercritical fluid continuously passes through the bed of particles and dissolves the solute, and the solvent is fed into the extractor and distributed evenly within the fixed bed. As the solvent flows through the plant material, the mass of the solute is transferred from the solid phase to the fluid phase, and the concentration of the solute in the solid and fluid phases varies continuously throughout the extractor. In general, the amount of solute is small, and the solute/solvent mixture barely reaches the equilibrium condition. The solutes are dissolved by the solvent and transferred by diffusion to the external surface; then, the solute/solvent mixture exits the extractor and passes through the precipitator, where they are finally separated (Veggi, 2013).

3.3.1 Extraction of essential oil The extraction of oils using SFE with scCO2 has been widely used to recover essential oils since it does not produce substantial thermal degradation or organic solvent contamination (Priyanka & Khanam, 2018). The use of essential oils in the food industry is extremely interesting as they can inhibit microbial growth, act as natural antioxidants by increasing the shelf-life of food products, and provide flavors to certain food products (Silva, Zabot, Na´thiaNeves, Nogueira, & Meireles, 2018). Many plant matrices have been used to obtain essential oils via SFE: Citrus limon, Pinus pinaster, Quercus ilex, Oenanthe crocata, Citrus aurantium, Origanum vulgare, Cuminum cyminum, Pelargonium graveolens, Lavandula officinalis, Thymus satureioides, Aloysia citrodora, Cymbopogon citratus, Lavandula stoechas, Mentha spicata, Thymus vulgaris, Thymus maroccanus, Eucalyptus polybractea, Rosa damascene, Rosmarinus officinalis, Matricaria recutita, Chenopodium ambrosioides, Psidium guajava, Valeriana officinalis, Eugenia caryophyllata, and Cinnamomum zeylanicum (Asbahani et al., 2015). Essential oils are composed of lipophilic substances that contain volatile components responsible for the aroma of plants, and this characteristic of essential oils contributes to their easy extraction by scCO2 (Fornari et al., 2012). According to a review by Fornari et al. (2012), the extraction of essential oils using scCO2 can be performed under moderate conditions of pressure (9
12 MPa) and at temperatures ranging from 35 C to 50 C. The extraction of essential oil from M. spicata by SFE was performed by Shrigod, Hulle, and Prasad (2017). In this study, the authors showed that the highest yield of essential oil (1.4%) was obtained at 48 C and 15.1 MPa. In another study, the highest recovery (4.57%) of essential oil from Leptocarpha rivularis also occurred at low pressure (10.8 MPa) and at a temperature of 52 C (Uquiche, Cirano, & Millao, 2015). However, the best condition for obtaining essential oil from Algerian Rosemary (3.5%) was at a higher pressure (22 MPa) and a lower temperature (40 C) (Zermane, Larkeche, Meniai, Crampon, & Badens, 2016). This shows that depending on the characteristics of the raw material used, high pressures must be applied since some compounds are present inside the cells and are difficult to be removed.

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3.3.2 Extraction of carotenoids Carotenoids are natural lipophilic pigments responsible for the yellow, orange, and red colors. They are the most diverse and widespread pigments found in nature, and more than 700 carotenoids have been identified (Gong & Bassi, 2016; Prado, Veggi, & Meireles, 2014). However, only α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein, and zeaxanthin are important to human health. Among the identified carotenoids, β-carotene plays the most important role in human health since it is the precursor of vitamin A (Prado, Veggi, & Meireles, 2014). In addition to contributing to color and acting as natural antioxidants, carotenoids have functional properties, such as protection against lung, head, neck, and prostate cancers, modulation of the immune system, growth factors and intracellular signaling pathways, regulation of cell differentiation, cell cycle and apoptosis, and photoprotection against UV radiation (Saini & Keum, 2018). All these positive attributes make carotenoids an interesting application in food products since modern consumers are increasingly concerned about the origin of products and have been searching for more natural sources. The major sources of natural carotenoids are colorful fruits, dark-green leafy vegetables, and unicellular microalgae. They can also be found in fungi, bacteria, microalgae, yeast, and industrial waste (Saini & Keum, 2018). The extraction of carotenoids can be performed using organic solvents, such as chloroform, hexane, isopropanol, methanol, methylene chloride, and diethyl ether. However, on the basis of environmental and health safety issues, these solvents have been increasingly rejected (Saini & Keum, 2018). Therefore the use of supercritical fluids for carotenoid extraction with or without a cosolvent has been increasingly gaining attention. In a review on the methods for the extraction of carotenoids, Saini and Keum (2018) observed that the key parameters for the efficient extraction of carotenoids using scCO2 are temperature (40 C
60 C), pressure (300
400 bar), time (30
120 min), CO2 density (solvent power), CO2 flow rate (1
5 mL/min) and cosolvent concentration (5%
25% v/v). The extraction of carotenoids from Scenedesmus almeriensis was investigated by Macı´as-Sa´nchez, Fernandez-Sevilla, Ferna´ndez, Garcı´a, and Grima (2010), and the best pressure and temperature for pigment recovery were 40 MPa and 60 C, respectively. The yields obtained by these authors were 1.5 mg β-carotene/g dry microalgae and 0.05 mg lutein/g dry microalgae. scCO2 with ethanol as a cosolvent was used to extract carotenoids from persimmon fruits (Diospyros kaki L.). In this study, yields of 15.5 6 0.6, 17 6 2, and 33 6 3 μg/g of xanthophylls in the forms of alltrans-lutein, all-trans-zeaxanthin, and all-trans-β-cryptoxanthin, respectively, were obtained from persimmon powder. The extraction conditions employed for xanthophyll recovery were 30 MPa, 60 C, 25% (w/w) ethanol, 3 mL/min flow rate, and 30 min. In this same study, nonoxygenated carotenoid was also obtained in the form of all-trans-β-carotene using 10 MPa, 40 C, 25% (w/w) ethanol, 1 mL/min flow rate, and 30 min of extraction time, with an extraction yield of 11.2 6 0.5 μg/g of persimmon powder (Zaghdoudi et al., 2016).

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3.3.3 Extraction of spices Herbs and spices are plant substances that act as seasoning agents for food. These aromatic and pungent plant substances have been widely used in cooking as condiments and in candies, cosmetics, fragrances, and medicines to provide aroma, flavor, and color (Mukhopadhyay, 2007). In addition to these characteristics, herbs and spices have antioxidant and antibacterial activities. Therefore they can be added to food systems to prevent their degradation, mainly oxidation (Coelho & Palavra, 2015). Spices can be obtained from various plant parts, such as bark, buds, flowers, fruits, leaves, rhizomes, roots, seeds, stigmas and styles or the entire tops of plants. Herbs are hardwood spices; some, such as dill and coriander, can be used as spices and aromatics herbs (Coelho & Palavra, 2015). Many plant matrices have been used to obtain spices via SFE: Piper nigrum, Ocimum basilicum, Carum carvi, Elettaria cardamomum, Apium graveolens, C. zeylanicum, Syzygium aromaticum, Coriandrum sativum, C. cyminum, Foeniculum vulgare, Allium sativa, Zingiber officinale, Myristica fragrans, Mentha piperita, Capsicum annuum or frutescens, R. officinalis, Satureja montana, Crocus sativus, T. vulgaris, Thymus zygis, Thymus serpyllum, Curcuma longa, and Vanilla planifo´lia (Coelho & Palavra, 2015). Among herbs and spices, ginger (Z. officinale), garlic (A. sativa), and turmeric (C. longa L.) are medicinal agents and functional foods. Therefore diets that include these natural compounds have been recognized for their ability to reduce the risk of chronic diseases, such as cancer and cardiovascular diseases (Bravi, Perretti, Falconi, Marconi, & Fantozzi, 2017; Leal et al., 2003). Ginger has an aromatic characteristic and can therefore be used as a flavoring agent in food products (Leal et al., 2003). Garlic is a natural antioxidant used mainly as a condiment in food (Bravi et al., 2017). Turmeric is used to impart flavor and yellow color in food formulations, such as curry (Leal et al., 2003). The conditions for the extraction of spices can vary greatly according to the raw material used since spices have different characteristics. In a review by Mukhopadhyay (2007), the conditions of spice extraction using scCO2 ranged from 15 to 30 MPa for pressure and from 40 C to 60 C for temperature. The extraction of ginger oil from Z. officinale was investigated by Salea, Veriansyah, and Tjandrawinata (2017). The optimum extraction conditions using scCO2 were 15 MPa, 35 C, and 15 g/min. In this study, the highest oil yield was 3.10%, and the highest content of 6-gingerol in ginger oil was 20.7%. A yield of 19 g/kg of garlic was obtained from the extraction of dried garlic flakes (Allium sativum) using scCO2 at 30 MPa and 55 C for 4 h (Del Valle, Glatzel, & Martı´nez, 2012). The extraction of turmeric (C. longa L.) oil and ar-turmerone using scCO2 was performed by Carvalho, Osorio-Tobo´n, Rostagno, Petenate, and Meireles (2015). In this study, the optimum extraction conditions for obtaining highest yields of turmeric oil (6.9 kg extract/100 kg dry raw material) and ar-turmerone (1.14 kg extract/100 kg dry raw material) were 60 C and 25 MPa.

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3.3.4 Extraction of anthocyanins Anthocyanins are plant-derived compounds belonging to the phenolic compounds group (Ca´ssia et al., 2016). In addition to having natural red, blue, and purple pigments, anthocyanins play an important role in human health. Anthocyanins have antioxidant, antimicrobial, antiviral, antiinflammatory, and anticancer properties and can also help in the treatment of Alzheimer’s disease and diabetes (Heinonen et al., 2016). Due to all these properties, the extraction of anthocyanins by means of green technologies has been recently applied in food products by the food industries. For efficient extraction of anthocyanins (compounds of polar characteristic), it is necessary to use cosolvents. The most commonly used cosolvents for anthocyanin extraction are ethanol, methanol, aqueous ethanol, aqueous acidic methanol, and aqueous acidic ethanol (Heinonen et al., 2016; Paes, Dotta, Barbero, & Martı´nez, 2014; Seabra, Braga, Batista, & De Sousa, 2010). However, hydroalcoholic mixtures can obtain high yields of anthocyanins. For instance, the highest content of monomeric anthocyanin (22 mg C3RE/g) was obtained from juc¸ara (Euterpe edulis Mart.) residues using an acidified hydroethanolic mixture (concentration of 10% w/w) as a cosolvent at 20 MPa and 60 C (Garcia-Mendoza et al., 2017). In another study, the highest levels of anthocyanins (808 mg/100 g) were extracted from blueberry (Vaccinium myrtillus L.) using a mixture of water and ethanol as a cosolvent at 20 MPa and 40 C (Paes et al., 2014).

3.4

Applications in transformation and processing of food

Among the supercritical fluid applications, extraction is assuredly the most consolidated and widespread technique not only at the laboratory scale but also at the industrial level. The focus today is to insert these techniques into different industrial processes. Apart from the extraction applications, supercritical fluids have also been explored for food transformation that aims to preserve the sensorial, safety, and quality properties of food products. Particle formation, extrusion, and fractionation are some of the pressurized fluid-based processes that have been used to achieve food preservation as well as to improve its availability in the human body.

3.4.1 Particle formation Particle formation techniques based on supercritical fluids have been mainly developed over the past two decades, motivated by the fact that particles with controlled properties and functionalities can be obtained (Temelli, 2018). Although these techniques have been developed with a focus on pharmaceutical products, their application in food science has increased due to the great potential of the unique properties related to the solvent power of supercritical CO2 (Rodrı´guez-Meizoso & Plaza,

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2015). The particles obtained by these techniques can be single-component or multi-component composite systems. The term, micronization, refers to particle formation of single components resulting in microparticles or nanoparticles with a large specific surface area, whereas composite systems refer to micro/nanosized spheres or capsules where an active compound is coated with a shell material (Temelli, 2018). Recent examples of successful applications of the pressurized fluid-based process for particle formation in the food industry include single-component products, such as chocolate obtained by particles from gas saturated solutions (PGSS), lecithin powders obtained by supercritical antisolvent (SAS), and concentrated powders with standardized levels of various extracts of herbs and spices (rosemary, pepper, ginger, cinnamon, etc.) (Weidner, 2009).

3.4.2 Extrusion The advantages of introducing scCO2 in the barrel of the extruder are not only related to the changes in the rheological properties of the material inside the extruder but also to the role of scCO2 as an expansion agent. The diminution of viscosity limits the mechanical stresses, allowing a decrease in operating temperatures of the standard extrusion process. Therefore it becomes easier to handle molecules with limited thermal stability (Chauvet et al., 2017; Sauceau et al., 2011). Furthermore, SCFX results in products with dual texture (porous interior with smooth external surface) controlled by varying the number and size of cells. Reactive extrusion is also possible via pH control in the barrel through the formation of carbonic acid (Balenti´c et al., 2017). In 1992, Rizvi and Mulvaney patented a technology for producing highly expanded starch in which scCO2 was used as an expansion agent to reduce viscosity (Rizvi & Mulvaney, 1992). Afterwards, the process was extended to other applications. Currently, SCFX is mainly used to obtain starchy, fibrous, and proteinaceous extruded products, such as breakfast cereals, snack foods, pasta, chocolate and confectionery, coffee, leavened dough and bread, and milk protein and whey protein crisps, with improved properties and better nutritional quality compared to those from conventional extrusion (Balenti´c et al., 2017). These applications were recently reviewed by Sauceau et al. (2011) and Chauvet et al. (2017).

3.4.3 Fractionation Fractionation using scCO2-based processes has been achieved in different manners, and it is mainly used for fractionating aroma by removing waxes from the volatile fraction or for fractionating lipids from oils. The fractional extraction, or sequential extraction, has been used to improve the use of raw materials as well as to increase the purity of the fractionated products. Sequential scCO2 extraction used for exploring scCO2 selectivity was recently performed to recover nonpolar compounds, such as tocols, unsaturated fatty acids, and carotenoids, from passion fruit bagasse. This process was carried out in three steps with the following operational conditions: 60 C

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and 17 MPa; 50 C and 17 MPa; and 60 C and 26 MPa. At these conditions, tocols were recovered only in the first step; the second step extracted fatty acids without tocols and with a low carotenoids content; and the third step yielded a high concentration of carotenoids (Vigano´ et al., 2016). As scCO2 is, in fact, a good solvent for lipophilic (nonpolar) compounds, several authors have used liquid solvents, such as ethanol and water, to improve the solvent power of scCO2; thus the extraction of more polar compounds, such as anthocyanins (Paula, Paviani, Foglio, Sousa, & Cabral, 2013; Seabra et al., 2010), saponins (Bitencourt, Queiroga, Montanari Junior, & Cabral, 2014), and phenolic compounds (Garmus, Paviani, Queiroga, & Cabral, 2015), has been enabled. However, this strategy presents some drawbacks because the increased solvent power also results in lower selectivity; subsequently, a step to eliminate the liquid solvent is required since the solvents are liquid at atmospheric pressure and are collected together with the extract (Reverchon & De Marco, 2006). As previously mentioned, the fractionation of extracts after the extraction is achieved in the separators operating at decreasing pressures is also an efficient manner to separate the compounds. This procedure has been applied with success to SFE for fractionating essential oils, such as waxes and oleoresins, from heavier compounds (Della Porta, Taddeo, D’urso, & Reverchon, 1998; Reverchon, 1992; Reverchon, Daghero, Marrone, Mattea, & Poletto, 1999; Sima´ndi et al., 1999, 2000).

3.5

Applications in food preservation

Another promising application of supercritical technology is the preservation of food. With increasing demand for food production, industries have been increasingly concerned with the need to apply sustainable techniques to prolong the shelflife of foods to guarantee that their sensory quality and safety. For a long time, the inactivation of microorganisms in food products was achieved by thermal processes (Perrut, 2012). However, this kind of processing promotes the thermal degradation of heat-sensitive products with functional properties and causes undesirable organoleptic changes. Thus the combination of high pressures and CO2 has emerged as an effective alternative for the destruction of microorganisms to preserve food without affecting nutritional value or organoleptic attributes (Amaral et al., 2017; Garcia-Gonzalez et al., 2007). Different gases can be used to inactivate microorganisms: N2, CO2, N2O, Ar, and tetrafluoroethane. However, according to reviewed by Garcia-Gonzalez et al. (2007), the experiments carried out with CO2 sterilized microorganisms with a higher efficiency than the experiments carried out with other gases. Moreover, in the same review, it was proved that CO2 in the supercritical state is more efficient for microbiological and enzymatic inactivation than CO2 in the liquid and gaseous states. This is because in the supercritical state, CO2 easily penetrates the cells (cell membrane modification) and extracts intracellular components (removal of vital

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constituents from cells and cell membranes), resulting in an increase in the perturbation of the biological systems (Garcia-Gonzalez et al., 2007). High hydrostatic pressure processing (HHP) for pest control and sterilization of food has already been used in Japan as an alternative to heat treatment. However, this process requires high pressures (400
800 MPa) and long exposure times to achieve efficient sterilization, which make the cost incompatible with most markets (Perrut, 2012). On the other hand, scCO2 technology is as efficient as HHP but uses lower pressures (10
20 MPa), which helps to reduce operating costs; thus this technology is feasible on an industrial scale (Amaral et al., 2017). The efficiency of the microbial and enzymatic inactivation by scCO2 is affected by several factors, including: G

G

G

G

Pressure: The activity of an enzyme decreases with CO2 pressure level (Hu, Zhou, Xu, Zhang, & Liao, 2013). However, pressures above 20 MPa do not significantly improve inactivation. A medium pressure range (8
15 MPa) is adequate. In addition, a rapid pressure cycle increases the inactivation rate (Perrut, 2012). Temperature: A temperature of 60 C should not be exceeded because higher temperatures affect the quality of the food. Higher temperatures stimulate CO2 diffusivity and accelerate the molecular collisions between the applied CO2 and the target enzymes (Hu et al., 2013). However, for efficient microbial inactivation, temperatures below 40 C are not recommended (Perrut, 2012). Time: Long times have been shown to decrease the activity of investigated enzymes (Hu et al., 2013). pH: Enzymes and microorganisms are typically more sensitive to acidic environments (Hu et al., 2013; Perrut, 2012).

3.6

Environmental impact

Concerns about climate change, global warming, and scarcity of resources needed to supply future generations have propelled the development of sustainable processes instead of only highly productive processes (Herrero & Iban˜ez, 2018; Vardanega, Prado, & Meireles, 2015). In this sense, supercritical technology is key to developing a new, sustainable society since processes involving supercritical fluids minimize the environmental impact through the elimination of toxic residues and promote the better utilization of byproducts (Knez et al., 2014). In addition to the well-known eco-friendly characteristic of supercritical fluids, the proposal to utilize supercritical fluid-based processes in biorefineries has gained special attention because these processes can also reduce the environmental impacts related to energy generation and solid residue accumulation. The biorefinery concept supports a green production platform in which different processes are integrated to convert biomass into energy and a variety of products, mainly biofuels and added-value coproducts, in a sustainable manner (Cherubini, 2010). Supercritical fluid-based processes have demonstrated to be an ideal clean technology that can be used as part of a holistic biorefinery process for the recovery of bioactive compounds from different biomasses, that is, not only “fresh”

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vegetable matrices but also agri-food residues and wastes. Several recent review papers addressed the utilization of subcritical and supercritical fluid technologies for agri-food residue valorization (Herrero, Cifuentes, & Iban˜ez, 2006; Herrero & Iban˜ez, 2018; Vardanega et al., 2015; Vigano´, Machado, & Martı´nez, 2015). The main processes involved in biorefineries are scCO2 extraction that has been widely used for recovering bioactive compounds, such as phenolics and fatty acids (Benelli, Riehl, Smania, Smania, & Ferreira, 2010; Farı´as-Campomanes, Rostagno, & Meireles, 2013; Seabra et al., 2010; Vigano´ et al., 2016), and subcritical and supercritical water hydrolysis with or without the assistance of scCO2 to obtain monosaccharides from lignocellulosic wastes (Forster-Carneiro, Berni, Dorileo, & Rostagno, 2013; Mayanga-Torres et al., 2017; Prado, Forster-Carneiro, et al., 2014; Prado, Vardanega, et al., 2017; Prado, Lachos-Perez, Forster-Carneiro, & Rostagno, 2016). Organosolv treatment assisted by scCO2 has also been used for the production of nanocellulose (Albarelli, Paidosh, Santos, Mare´chal, & Meireles, 2016). Although supercritical fluids-based processes, especially scCO2 extraction, have recently been reported as environmental friendly and are considered a mature technique, systematic studies regarding the environmental issues related to these processes are still scarce, and the literature presents only a few studies on the analysis of the environmental impacts of scCO2 processes. Life cycle assessment (LCA) is an interesting tool to disclose the impacts of scCO2 processes in a wide range of categories and has been used for this purpose. An LCA was performed to compare the environmental impact of the water extraction and particle formation online processes to other green processes, such as scCO2 extraction and pressurized hot water extraction, for obtaining antioxidant compounds from rosemary leaves (Rodrı´guez-Meizoso et al., 2012). By analyzing all categories of the LCA, it was clear that the solvents employed in all the processes have no important impact mainly because they are green and are used in very small volumes. In contrast, the electricity production demonstrated a significant effect in all the environmental categories studied. Even the processes using CO2, which contributes to the global warming potential, are influenced more by the amount of CO2 from the production of electricity needed for heating and pumping than by the amount of CO2 used for the extraction. The environmental impacts of caffeine extraction from coffee beans using scCO2 was also evaluated through an LCA approach (De Marco, Riemma, & Iannone, 2018). The analysis considered the whole chain of caffeine production from agricultural production to caffeine purification. It was demonstrated that agricultural stages, transportation, and extraction have the most effect on the environmental categories studied. The great impact of the agricultural step is mainly due to the use of fertilizers and to the diesel consumption for planting/harvesting operations, while the impact of the extraction step is due to the electrical energy generation. Considering the importance of fertilizers and electricity sources, the authors proposed an improved scenario where the amount of fertilizer was reduced and a portion of the electricity was substituted by electricity produced by photovoltaic panels, reaching a global reduction in impact of 14.6% with respect to the base case (De Marco et al., 2018).

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LCA was also employed to analyze the environmental impact of microalgae oil acquisition using different extraction techniques, including scCO2 extraction, CO2expanded fluid extraction, and conventional extraction using organic solvents (chloroform, methanol, dichloromethane, isopropanol, and cyclohexane) (Wang et al., 2016). Considering the solvents used in each extraction method, it was observed that the extraction techniques using scCO2 presented a significantly lower environmental impact compared to the conventional extractions using organic solvents due to the harmful nature of these compounds. However, when energy consumption was included in the analysis, the environmental impact changed significantly. Extraction methods that required an intense energy input, such as scCO2 extraction, suffered greatly from the propagation of the environmental impact from electricity generation, in contrast to what was observed for the conventional extractions that were less sensitive to the consideration of energy consumption (Wang et al., 2016). A study comparing the potential environmental impact of three extraction processes to recover essential oils from citronella (Cymbopogon winteriana) and lemongrass (Cymbopogon citrus) was performed by Moncada, Tamayo, and Cardona (2014). The processes evaluated were water distillation, scCO2 extraction, and solvent extraction, and considered two scenarios: (1) without any level of energy integration and (2) with full energy integration. The results demonstrated that the least harmful process was fully integrated water distillation followed by scCO2. The carbon footprint analysis demonstrated that water distillation without energy integration was the most harmful process due to the energy required to heat the water to its bubble point. A similar effect occurs with scCO2 extraction because the external energy required for the compression of CO2 leads to a higher carbon footprint. Considering all of these aspects, it is shown that the heat integration strategy should be considered in the design of cleaner processes. Based on the examples, using scCO2 to replace organic solvents is an excellent alternative to reduce the environmental impact of extraction processes. However, the energy consumption of scCO2 extraction processes remains a very important environmental issue. Apparently, the adoption of renewable power sources is necessary to reduce the environmental impact of scCO2 processes, as demonstrated by Wang et al. (2016). These authors reported that the environmental impact of scCO2 extraction can be reduced to one-third when solar energy is applied and to onefourth when wind is applied. However, while the adoption of renewable energy is a promising way to reduce the environmental impact, the cost of this type of energy is also an important issue for the industry since the use of renewable energy can be up to sixfold more expensive than the current power sources (Wang et al., 2016).

3.7

Upscaling and its application in industry

For years, the industrial application of scCO2-based processes was limited to mainly extraction and fractionation of natural products for food and pharmaceutical purposes; this was because the investment cost was high and these processes were

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considered unfamiliar operations (Mohamed & Mansoori, 2002; Rizvi, 1994). Nevertheless, significant development in the field has led to lower equipment costs, and scCO2 technology has proven to be viable at the industrial scale (Brunner, 2005). As mentioned, among the scCO2 applications developed, the SFE process is used most extensively, especially in the food and beverage industry, for obtaining caffeine, fats, flavor oils, and essential oils (Djas & Henczka, 2018). Perrut (2002) estimated that approximately 100 industrial-scale SFE units were under operation in the early 2000s and this number increased to 300 units in 2009 (Chemat et al., 2017); more recently, Del Valle (2015) indicated that there are probably more than 150 industrial-scale SFE units with a capacity of more than 500 L operating around the world. Particle formation plants have also been found at the industrial scale but are few. According to the Natex Prozesstechnologie GesmbH manufacturer (www.natex.at), there are powder generation plants with a capacity of 150/300 kg/h operating at pressures of up to 35 MPa in different food companies in Germany; Nateco2 (www. nateco2.de) has also been applying the PGSS technology (capacity not known) for producing free-flowing powders from liquefied substances to be used in the food industry; Ceapro Inc. (www.ceapro.com) has been scaling up the PGX technology (pressurized gas-expanded liquid) for obtaining dried and impregnated products. The main industrial food applications of particle formation techniques include particles with standardized contents of extracts from herbs and spices, soybean lecithin, chocolate powders, and solid lipid particles (Temelli, 2018; Weidner, 2009). However, despite the potential advantages of the scCO2 processes, more recent applications of extrusion are still new, and further development is necessary to enable better understanding and process control prior to industrial scale-up (Sauceau et al., 2011). Regarding the scaling procedure, many studies have addressed the selection of scale-up criteria for SFE; however, the scale-up of other applications remains scarce. Only a few works have reported the scaling up of particle formation processes, and the criteria for these purposes are not well established. Kurniawansyah, Mammucari, Tandya, and Foster (2017) processed para-coumaric acid using the atomized rapid injection solvent extraction process and reported that the scale-up can be achieved simply by maintaining the antisolvent/solvent ratios and pressure differentials while increasing the batch volumes. Several authors have proposed the scale-up of the SAS process to pilot scale. Thiering, Dehghani, and Foster (2001) and Muthukumaran and Chordia (2003) stated that, theoretically, to increase the nozzle size, classical dimensionless scaleup considerations should be used. This includes adjusting the flow rate and other variables to maintain the Reynolds, Weber, and other relevant dimensionless number constants. This characterizes the spray dynamics and jet breakup. As jet hydrodynamics are limiting, the simplest scale-up option is a modular design where nozzle characteristics are identical to those at the laboratory scale and the atomization chamber is increased to accommodate more nozzles. On the other hand, Adami (2007) maintained a constant solution/antisolvent feed ratio when scaling up nalmefene HCl and proved that these parameters could also be applied to other

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compounds. However, few examples of successful application of SAS at the pilot scale of micrometric particle production have been found in the literature. Although publications on SFE cover a broad range of applications, each raw material requires specific processing parameters as well as scale-up criteria for production to be successfully moved from laboratory scale to industrial scale, which remains a challenge for new applications (Stoica, Dobre, Stroescu, Sturzoiu, & Pˆarvulescu, 2015). In general, to predict scale-up performance, certain criteria need to be taken into account: constant kinetic parameters, empirical equations based on geometry, and complex mathematical models (Prado, Veggi, & Meireles, 2017). Based on these studies, several criteria have been proposed and analyzed in the literature. According to Clavier and Perrut (2004), the easiest method for scaling up SFE processes is to keep one or both ratios of QCO2/F and S/F constant, where QCO2 is the solvent flow rate, F is the feed mass in the extractor, and S is the solvent mass required for the extraction. The application of specific criteria depends on the type of mechanism that controls the extraction. In processes that are limited by internal diffusion, the amount of time the feed is in contact with the solvent is the determinant factor, which is described by the solvent residence time (tRES). By adopting the QCO2/F constant, the tRES is conserved. Thus, when extraction is limited by internal diffusion, the QCO2/F ratio should be kept constant; when extraction is limited by solubility, S/F should be kept constant; and when both limitations are relevant, QCO2/F and S/F should be kept constant. Studies applying the constant QCO2/F criterion (and consequently preserving the tRES) have been frequently investigated in scale-up studies for several vegetable matrices. Mezzomo, Martı´nez, and Ferreira (2009) evaluated several criteria for scaling up the SFE of peach (Prunus persica) almond oil and selected the QCO2/F criterion as the best because they observed that convection was the dominant mass transfer mechanism while diffusion was the limiting factor. The same criterion also produced excellent results for the SFE of Colombian blueberry (Vaccinium meridionale Swartz) (Lo´pez-Padilla et al., 2016). de Melo et al. (2014) found a similar extraction yield and triterpenic acid concentration when maintaining the QCO2/F ratio in the scale-up of the SFE of Eucalyptus globulus bark. Aguiar, Visentainer, and Martı´nez (2012) successfully used the QCO2/F constant to perform the scale-up of the SFE of striped weakfish wastes. The QCO2/F constant was also evaluated for the SFE of clove buds (Eugenia caryophyllus) and vetiver roots (Chrysopogon zizanioides), and the authors of the study observed that this criterion presented good reproducibility for the SFE of clove buds but did not show satisfactory results for the SFE of vetiver roots (Martı´nez, Rosa, & Meireles, 2007). The criterion of a constant S/F ratio has also been adopted for the scale-up of different matrices (Prado et al., 2012; Prado, Prado, & Meireles, 2011; Salea et al., 2017; Zabot, Moraes, & Meireles, 2014; Zabot, Moraes, Petenate, & Meireles, 2014). The use of the constant S/F criterion for the reproduction of the overall extraction curves at different scales resulted in slightly higher yields as the SFE process of grape seeds (Vitis vinifera L.) increased from laboratory (0.29 L) to pilot scale (5.15 L) (Prado et al., 2012). Assuming the same criterion, Salea et al. (2017)

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successfully scaled up the SFE process of ginger (Z. officinale var. Amarum) to recover ginger oil in a commercial scale unit (50 L). Another important factor that should be taken into account in the scaling up of SFE processes is the bed geometry dimension, since it is very important in SFE and influences the overall yield of extract composition (Zabot, Moraes, & Meireles, 2014). In this approach, the ratio of vessel bed height (H) to vessel bed diameter (d) is useful and should be maintained as follows: (H/d)extractor1 5 (H/d)extractor 2. Joki´c et al. (2012) verified the influence of the extractor size on soybean oil extraction using different extractor volumes (0.2 and 5 L) and a similar geometry and mass transfer mechanism as those involved in the extraction using a constant QCO2/ F. According to the authors, the mass transfer coefficient in the fluid phase increased with the increase in extractor size while the mass transfer coefficient in the solid phase was independent of extractor size. Ferna´ndez-Ponce et al. (2016) considered the criteria of geometry and dynamic factor to scale up the SFE of mango leaves (Mangifera indica). First, the geometric relation of H/d was kept constant. Then, the dynamic criteria, S/F, QCO2/F, and QCO2 3 d/F, were evaluated, showing that QCO2 3 d/F was the best approach for this raw material. This study suggested that solubility is not the only limiting factor in the SFE of mango leaves and that diffusion plays an important role in this case. The influence of bed geometry at a constant S/F ratio was investigated for the SFE of clove buds (E. caryophyllus) (Zabot, Moraes, Petenate,et al., 2014) and rosemary leaves (R. officinalis) (Zabot, Moraes, & Meireles, 2014). The evaluated H/d values were 7.1 and 2.7 for 1 L extraction vessels. For rosemary extraction, the H/d ratio presented a pronounced influence, suggesting that the S/F criterion is not suitable for the scale-up of this raw material. However, bed geometry presented no significant influence on the extraction of clove bud oil, validating the S/F criterion for the scale-up of this raw material. Other authors have also verified that different bed geometries have no influence on scale-up when the S/F ratio is constant. Prado et al. (2012) observed that by using two bed extraction sizes (H/d values of 2.31 and 5.94) while keeping the S/F ratio constant, they were able to reproduce the extraction curves for grape seed extraction. Paula et al. (2016) evaluated the QCO2/F criterion while varying the bed geometry ratio (H/d) from 1.86 to 5.2 to scale up the SFE of rosemary-of-field (Baccharis dracunculifolia) leaves and found similar kinetic behaviors for all bed geometries studied. When SFE parameters such as temperature and pressure must be held constant, another possibility to scale up the production is to keep the dimensionless numbers, such as Reynolds number (Re, a value in fluid mechanics representing laminar vs turbulent flow properties and thus inertial vs viscous forces, respectively), constant (Reverchon, Adami, & Caputo, 2006). Casas et al. (2009) evaluated the scale-up of the SFE of sunflower (Helianthus annuus L.) leaves by keeping the H/d ratio constant and changing the QCO2 3 d/F ratio and Re. The authors concluded that it is important to keep both ratios constant to obtain similar extraction yields at laboratory and pilot-plant scales. Lo´pez-Padilla, Ruiz-Rodriguez, Reglero, and Fornari (2017) developed a new specific correlation among the dimensionless Schmidt

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number (Sc), CO2 mass flow, bed geometry, and the supercritical mass transfer coefficients (kYA) for scaling up the SFE of marigold (Calendula officinalis). The correlation was derived by using constant values of the bed porosity and mean particle size of the marigold raw material. Furthermore, several studies in the literature have evaluated the scale-up process using mathematical modeling as a risk-reducing strategy by allowing the operator to define and control the limiting factors that govern the SFE process (Del Valle et al., 2004; Ferna´ndez-Ponce et al., 2016; Han, Cheng, Zhang, & Bi, 2009; Kotnik, ˇ Skerget, & Knez, 2007; Passos, Coimbra, Da Silva, & Silva, 2011). However, no single scale-up criterion can be successfully applied to all systems (Lo´pez-Padilla et al., 2016). Recently, De Andrade Lima, Charalampopoulos, and Chatzifragkou (2018) mentioned that the SFE of carotenoids from carrot peels is a potentially scalable process solely by increasing the feed mass and keeping all the optimized conditions constant.

3.8

Future trends

This chapter describes the status of scCO2-based technologies for food processing and extraction and demonstrates their great potential to produce high-quality products in a more environmentally friendly way. However, despite the advantages of using scCO2, extraction is still the most widespread scCO2 application at the industrial scale, while only a few other applications have been used at a large scale. In this sense, operators are required in the future to extend the use of scCO2 in the food industry, as highlighted in this section. Recent papers have addressed the importance of improving the knowledge of the scale-up and the economic and environmental assessment of scCO2-based technologies to enable a reliable comparison with the conventional processes to support the establishment of the real advantages of these technologies (Herrero & Iban˜ez, 2018; Temelli, 2018). While the future directions for scCO2 extraction point to some advanced aspects of the technology, such as integration and intensification of different processes, other areas still lack fundamental understanding of the behavior of the complex systems needed to establish the technical feasibility of the processes at the laboratory scale prior to industrial application. As demonstrated through the chapter, improved energy supply for supercritical processes is also a key factor since the energy requirement has been shown to be the main contributor of environmental impact associated with the supercritical technology. In this sense, the application of LCA tools needs to be increased to offer a better understanding of the environmental issues and to determine the energetic bottlenecks of the processes. According to the available literature, energetic integration can be a promising alternative for improving the environmental performance of supercritical processes. Thus more information related to these energetic aspects is crucial for establishing the eco-friendly status of the technology. Another promising trend is the development of integrated/intensified processes in biorefinery platforms based on the supercritical technology. The biorefineries

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aim to produce multiple product streams, including energy, biofuels, and highadded-value products, from renewable feedstock with little or no waste (Herrero & Iban˜ez, 2018; Vardanega et al., 2015). The utilization of the whole biomass associated with the production of high-added-value products helps promote the economic feasibility of the supercritical biorefineries since the raw material acquisition costs are the main contributors to the cost of manufacturing of products obtained by supercritical processes (Carvalho et al., 2015; de Aguiar, Osorio-Tobo´n, Silva, Barbero, & Martı´nez, 2018; Zabot, Moraes, & Meireles, 2018). Undoubtedly, the economic analysis can be considered fundamental for the industrial establishment of biorefinery platforms and as a part of an integrative approach to address the concerns of supercritical technologies, including scalability and environmental issues.

3.9

Conclusion

In this chapter, a survey of the established and more recent applications of scCO2 for obtaining products useful for food and pharmaceutical industries was provided. Among them, SFE is by far the most widespread scCO2 application, with several industrial plants operating around the world for a wide variety of compounds. In addition, it was demonstrated that other applications have emerged in the fields of food transformation and preservation, resulting in products that have elevated quality and are completely safe for human consumption. Although scCO2 processes are claimed as green, their real environmental impact has not yet been disclosed in the literature and is pointed out as a challenge for the upcoming years since scCO2 processes are an excellent alternative to achieve the sustainable production requirements present in the strategic plans of the future development of modern society.

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129.

High hydrostatic pressure processing of foods

4

Maria Tsevdou, Eleni Gogou and Petros Taoukis Laboratory of Food Chemistry & Technology, School of Chemical Engineering, National Technical University of Athens, Athens, Greece

4.1

Introduction

Nonthermal processing has evolved as one of the more prolific fields of research and applications in food engineering. Among the nonthermal technologies, prominent position as far as research and certainly with regard to industrial implementation is high-pressure (HP) processing. HP has successfully advanced through all technology readiness levels (TRL) reaching TRL9. HP can in many cases achieve the results of thermal processing with regard to food safety and control of qualityrelated parameters without the unavoidable detrimental side effects induced by high temperature. The overall objective is to produce products of superior quality in terms of sensorial, nutritional, and biofunctional properties. The most successful commercial applications can be classified as nonthermal pasteurization where HP has replaced conventional thermal pasteurization or allowed pasteurization of products not amenable to heat processing, achieving optimization of quality, and shelf life extension. Beyond nonthermal pasteurization and HP
high-temperature (HPHT) or pressure-enhanced sterilization, current HP research is also focusing on aspects that are mainly related to targeted structural modification of food macromolecules, biofunctionality, and green processing and sustainability. The commercial success of HP processing can be mainly attributed to the ability to produce fresh-like food products with superior nutritional value and extended shelf life when compared with the respective thermally treated food products. These two basic aspects of HP-processed food products successfully fulfill both consumers’ demand for fresh-like foods and the food industry requirement for shelf life extension. Compared to the conventional thermal processes, potential energy and environmental benefits could also factor in the adoption of the HP technology. Although the main tangible goal in HP processes is food quality optimization and shelf life prolongation, HP microbial safety risk control is an important additional benefit. Vegetative pathogenic bacteria, such as Escherichia coli, Listeria monocytogenes, and Salmonella, can be inactivated at the HP conditions normally applied in industrial processing. In contrast, bacterial spores exhibit increased pressure and temperature resistance requiring intense HP process conditions. HP processing is thus classified as HP pasteurization, HPHT, and pressure-assisted thermal sterilization (PATS) depending on the pressure
temperature combination. Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00004-5 © 2019 Elsevier Inc. All rights reserved.

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HP pasteurization processes are usually performed in the pressure domain of 300
650 MPa either at room temperature or at temperatures in the range of 10 C
30 C. HPHT and PATS processes involve treatment of foods at the pressure domain of 600
1400 MPa at elevated temperature ranging from 70 C to 130 C (Barbosa-Canovas & Juliano, 2008).

4.2

Fundamental principles of high pressure process

Application of HP for food treatment and preservation was introduced in the advent of the 20th century (Hite, 1899). However, only after 1990, research intensified, focusing on producing safe and stable food products without the adverse effect of high-temperature processing on quality and sensory attributes (Grant, Patterson, & Ledward, 2000). Products using the HP technology, mainly fruit preparations, salad dressings, and sauces, started being commercially available in the Japanese, American, and European market (Tewari, Jayas, & Holley, 1999). At the turn of the 20th century, products such as guacamole, shelled oysters, fruit juices, and poultry products were introduced in the United States (Meyer, 2000). HP pasteurization, replacing thermal pasteurization, can lead to products of extended shelf life while preserving thermally labile flavors, nutrients, color, and texture (Fonberg-Broczek et al., 1999). Inactivation of most vegetative pathogenic and spoilage microorganisms can be achieved in the 200
600 MPa range at process temperatures of 5 C
45 C. Sterilization, that is, inactivation of spores such as Clostridium botulinum and Bacillus could only be achieved through synergies of elevated heat and pressure (Ahn, Balasubramaniam, & Yousef, 2007). Bacterial spore inactivation without heat requires pressures exceeding 800 and up to 1700 MPa far exceeding current industrial equipment design. HPHT or PATS involves the use of initial chamber temperatures of 60 C
90 C, and through internal adiabatic heating at pressures above 600 MPa, process temperatures can reach 90 C
130 C. In this high-temperature short-time process, both pressure and compression heat contribute to the process’s lethality. Instantaneous and volumetric adiabatic temperature increase, in combination with HP, accelerates spore inactivation in low-acid media (Leadley, 2005), the main advantage being the shorter processing time than equivalent conventional thermal processing (Matser, Krebbers, Van Den Berg, & Bartels2004) that can result in higher quality and nutrient retention in selected products. HPHT processing achieved superior retention of flavor components in fresh basil; texture in green beans; and color in carrots, spinach, and tomato puree (Krebbers et al., 2002, 2003). Vitamins C and A, heat-labile nutrients, were less affected in HPHT processing than conventional retorting (Matser et al., 2004). In analogy to the classic thermal processing, processes of food and the related phenomena that are being studied, optimized, and innovated since Pasteur set the foundations; the substantial research activity of the recent years and the growth in HP technology application is expected to continue for the foreseeable future. Scientific, technological, and technical issues should be thoroughly explored for

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89

each food-related action and component before HP industrial application. Food industry expects fully substantiated and validated answers regarding the applicability and the benefits of HP, as a physical process for better preservation of target food products. Optimization of the conditions (safety, quality retention, nutritional value, and consumer acceptability being the main criteria) leads to efficient design and reliable control of the process. The systematic study of the technical parameters, that would allow for the use of the scientific achievements in a controlled and effective industrial process, is based on the kinetic study and modeling of the destructive reactions of several factors that lead to spoilage or degradation of quality and functional properties of the food, during the HP treatments (Hendrickx & Knorr, 2002). Stoforos, Crelier, Robert and, Taoukis (2002) expanded on the conventional thermal processing equations to outline the mathematical basis for the modeling and design of the HP process. The rate of deterioration of an index affected by the HP process is a function of pressure and temperature conditions. Assuming that the deterioration is described by a first-order reaction, 2

dC 5 kC; dt

k 5 f ðT; P; . . .Þ

(4.1)

where C is the concentration (or activity or population, etc.) of the HP sensitive index (e.g., number of microorganisms/mL, g/L, etc.), k is the reaction rate constant at constant conditions of the process (min21), t is the time of the treatment (min), T is the temperature during the HP treatment (K), and P is the pressure (MPa). Integrating Eq. (4.1) leads to lnðCÞ 2 lnðCo Þ 5

ð tb

2 kdt

(4.2)

ta

where Co is the initial concentration and subscripts a and b refer to the initial and the final condition, respectively (in this case the beginning and the end of the process). To calculate the integral of Eq. (4.2) the effect of pressure and temperature on the reaction rate is introduced using the Arrhenius (Eq. 4.3) and Eyring (Eq. 4.4) equations: 
 Ea 1 1 2 k 5 kTref exp 2 Tref R T   Va P 2 Pref k 5 kPref exp 2 T R

(4.3)



(4.4)

where Tref and Pref denote a reference temperature and a reference pressure, respectively, Ea (J/mol) and Va (mL/mol) are the activation energy and volume, respectively, and R is the universal gas constant (8.314 J/(mol K)).

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Green Food Processing Techniques

Using Eqs. (4.3) and (4.4) in Eq. (4.2), assuming that the activation energy and volume depend on the pressure and the temperature, respectively, Eq. (4.2) is finally expressed as follows:  ln

    ðt 
  C E a ð PÞ 1 1 Va ðT Þ P 2 Pref 2 2kref exp 2 5 2 dt Co R T Tref R T 0

(4.5)

This equation forms the basis for the modeling of the HP treatment (e.g., for the determination of an equivalent time of treatment, the calculation of the F-value), similarly to the methodology for conventional thermal treatments. Eq. (4.5) can accordingly be expanded for nth order phenomenon (Eq. 4.6) if Eq. (4.1) is expressed as dC/dt 5 kCn: 12n CA12n 2 CAo 5 ð n 2 1Þ

ðt  0




 E a ð PÞ 1 1 Va ðTÞ ðP 2 Pref Þ 2 2 kref  exp 2 dt 2 R T Tref R T (4.6)

The quantification of the effect of the process parameters and the postprocessing handling, storage, and distribution conditions on the shelf life of products allows for the optimization of the design of the overall chain. Based on the described principles, in order to develop a successful HP-processed food product the following stepwise approach would be required. First, the effect of HP on the safety and quality determining indices such as vegetative pathogens, spoilage microorganisms, and deteriorative enzymes should be studied and kinetically modeled in simulant systems of the food product in question. Based on this quantitative information, the parameters of optimal HP process can be estimated, then testing and validation of the sensorial and nutritional quality of the actual food product after HP processing. Comparative shelf life testing against conventionally processed products, to assess the advantage in the real food chain, coupled with consumer acceptance tests complete a reliable HP product and process development scheme. Process deviations have to be taken into account in any industrial manufacturing process. Pressure and temperature monitoring and control during processing needs to be validated to assure the efficiency of the process. Process validation requires validation of the process impact on the selected process index, as described above, taking into account the potential impact of such deviations. In general the high hydrostatic pressure is in principle assumed to be uniform, and not affected by geometry or uniformity of the processed food product. This has been theoretically questioned (Karwe, Maldonado & Mahadevan, 2015; Minerich & Labuza, 2003) but is accepted in practice. Process time is fixed, taking into account come up time and time for release of pressure. On the other hand, temperature nonuniformity could be expected in HP processes due to adiabatic heating during the pressure buildup and to heat transfer phenomena during the treatment holding.

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Consequently, HP process nonuniformity would mainly lie in potential temperature gradients inside the HP vessel. These issues are discussed in Section 4.6.

4.3

The effect of high pressure on food quality and safety attributes

4.3.1 The effect of high pressure on microorganisms The application of HP in food products in order to inactivate the pathogenic and/or spoilage microflora has been the key objective of a significant number of research studies the past three decades. In general, it is well established that prokaryotic cells exhibit higher resistance to pressure than eukaryotic cells. Thus yeast and molds show higher pressure sensitivity than bacteria. Regarding bacterial spores, these are the most resistant in physical changes induced by HP, since pressures exceeding 800 MPa, usually in combination with elevated temperatures, may be needed to obtain an adequate level of inactivation. When investigating microorganisms’ inactivation in more detail, higher resistance to pressure of Gram-positive microorganisms (e.g., Bacillus, Listeria, Staphylococcus, and Clostridium) compared to Gram-negative microorganisms (e.g., Pseudomonas spp., Salmonella spp., Yersinia enterocolitica, and Vibrio parahaemolyticus), has been attributed to their thicker peptidoglycan layer (Considine, Kelly, Fitzgerald, Hill, & Sleator, 2008). Moreover, the growth phase of cells plays an important role to their resistance to pressure; cells of the stationary phase are more resistant to physical changes caused by HP than cells in the exponential phase, while this also depends on the growth temperature. In addition the resistance of bacteria to HP is also affected by the morphology of the cells, with rod-shaped bacteria being the most sensitive and sphericalshaped bacteria the most resistant to HPs (Daryaei, Yousef, & Balasubramaniam, 2016). Although the exact mechanism that is responsible for vegetative cells death under HP has not been fully described, it is well recognized that there are several intrinsic and extrinsic factors that are influenced by different food constituents and may alter the sensitivity of microorganisms to pressure. As a result, the pressure effects on microorganisms’ inactivation are multifaceted, and different mechanisms related to cell death can occur simultaneously when HPs are applied (Georget et al., 2015). Smelt, Hellemons and, Patterson (2001) reported that the cell death of vegetative microorganisms due to pressure-induced effects is related to: (1) protein and enzyme unfolding, including partial or complete denaturation; (2) cell membranes undergoing a phase transition and change of fluidity; (3) disintegration of ribosomes in their subunits; and (4) intracellular pH changes related to the inactivation of enzymes and membrane damage. The inactivation of microorganisms under HP conditions usually can be described by first-order kinetic models; however, because of the complexity of the microorganisms’ HP inactivation, the first-order model may not be always suitable to describe the phenomenon. In particular, initial lag phase (shoulder)

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Green Food Processing Techniques

and/or “tailing” patterns for extended processing time may occur during microbial inactivation under HP conditions, and consequently other kinetic models such as the Weibull, log-logistic, and modified Gompertz or Baranyi models are used (Daryaei et al., 2016; Georget et al., 2015). Similarly to the kinetic parameters that describe thermal inactivation of microorganisms, microbial inactivation under HP can be described by (1) the decimal reduction time (D-value), which is defined as the treatment time at constant pressure
temperature conditions required to reduce the microbial count by one-log cycle, (2) thermal resistance constant (zT), which is defined as the temperature increase required for 90% decrease in D-value at constant pressure, and (3) pressure resistance constant (zP), which is defined as the pressure increase required for 90% decrease in D-value at constant temperature. Bacterial vegetative cells, yeasts, and molds can usually be inactivated when pressures of 400
600 MPa are applied, without the need of combined thermal treatment (Katsaros, Alexandrakis, & Taoukis, 2014). However, studying and modeling of the inactivation of spores under HPs encounters many difficulties that are mainly associated with the lack of knowledge concerning the mechanistic impact of HP in combination with elevated temperatures on bacterial spores, as well as the difficulties when the appropriate surrogates must be selected. Clostridium spores (C. sporogenes and C. perfringens), Bacillus spores (Bacillus amyloliquefaciens), and Geobacillus stearothermophilus spores are reported as the most appropriate surrogates, due to their high thermo- and baroresistance (Table 4.1). The inactivation mechanism of bacterial spores under high-temperature
HP (HTHP) conditions is partially different from one of the bacterial vegetative cells. The differences between these mechanisms are related to the inactive metabolism, the presence of multiple protective layers, small acid-soluble proteins protecting the DNA, and the low water content in spores (Georget et al., 2015). The inactivation of bacterial spores, in contrast to that of vegetative cells, is achieved in at least two steps. During the first one, pressures up to 600 MPa combined with temperatures up to 60 C are applied in order spores germination to be achieved. In the following step, pressures above 600 MPa and up to 1200 MPa combined with temperatures above 60 C and up to 120 C are applied for the full inactivation of the spores (Reineke et al., 2011). However, it is well recognized that the majority of the proposed HTHP conditions have been conducted in simple systems such as buffers and/or broth systems (Table 4.2), and that the application of these conditions in real food products may significantly affect their efficiency due to the food constituents, for example, proteins, polysaccharides, lipids, etc., which have a baroprotective role to spores inactivation (Sevenich, Rauh, & Knorr, 2016). Foodborne pathogens and spoilage microorganisms of food products are generally inactivated when pressures at the range of 200
600 MPa at ambient temperature are applied, with the exception of some strains for which full inactivation might require higher temperatures that do not exceed 40 C (Table 4.3). Katsaros, Tsevdou, Panagiotou, and Taoukis (2010) developed a single multiparameter model (Eq. 4.7) to describe the effect of pressure and temperature process conditions on the D-values of lactobacilli. This equation takes into account the effect of pressure on the zT-value and the effect of pressure on the zP-value.

Table 4.1 Inactivation of selected bacterial spores in different growth media under high-temperature high-pressure (HTHP) processing. Bacterial spores

Growth medium

HTHP conditions

Log10 reduction

References

Buffer (pH 7.0) Buffer (pH 7.0) Buffer (pH 7.0) Buffer (pH 7.0) Buffer (pH 7.0)/Crab meat Mashed carrots Mashed carrots Mashed carrots

50 C/758 MPa/5 min 40 C/827 MPa/10 min 75 C/750 MPa/10 min 75 C/1200 MPa/10 min 75 C/827 MPa/20 min

4.5 5.0 5.6 .6.0 .3.0

80 C/600 MPa/1 s 80 C/600 MPa/60 min 80 C/600 MPa/12 min

.5.5 ,3.0 .5.0

Reddy et al. (1999) Reddy et al. (1999) Lenz, Reineke, Knorr, and Vogel (2015) Lenz et al. (2015) Reddy, Solomon, Tetzloff, and Rhodehamel (2003) Margosch et al. (2004) Margosch et al. (2004) Margosch et al. (2006)

Buffer/Beef broth

70 C/700 MPa/3 min

Meat balls in tomato puree Egg patties Egg patties

90 C/700 MPa/30 min

.4.5

105 C/700 MPa/4 min 110 C/700 MPa/5 min

6.0 6.0

Clostridium botulinum Type E Type E Type E Type E Type A Type B nonproteolytic Type B proteolytic Type A

Surrogates Geobacillus stearothermophilus G. stearothermophilus G. stearothermophilus Clostridium sporogenes PA3679

5.0

Rovere et al. (1998) Krebbers et al. (2003) Ahn, Lee, and Balasubramaniam (2015) Koutchma, Guo, Patazca and, Parisi (2005)

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Green Food Processing Techniques

Table 4.2 Decimal reduction times (D-values, min) of selected bacterial spores under high-temperature high-pressure processing at 105 C. Strain

600 MPa

700 MPa

750 MPa

Clostridium botulinum Type: Giorgio-A C. botulinum Type: 69-A C. botulinum Type: Clovis-A C. botulinum Type: 429-A C. botulinum Type: OS3-A C. botulinum Type: TJI-A Clostridium sporogenes Type: PA3679 Bacillus amyloliquefaciens

2.22 1.91 2.22 1.54 1.11 1.60 2.35 1.33

2.28 1.67 2.22 2.00 1.67 1.33 1.48 NA

2.22 1.33 1.67 0.95 1.82 1.25 1.29 NA

NA, Not available information. Source: Adapted from Wan, J., & Anderson, N. (2015). Considerations in validation of new food processing technologies for regulatory acceptance and industrial applications. In 2015 International nonthermal processing workshop. November 12
13, 2015, Athens, Greece (Wan & Anderson, 2015).

Tsevdou and Taoukis (2011) and Tsironi, Maltezou, Tsevdou, Katsaros, & Taoukis (2015) also used this model to describe the inactivation kinetics under HP conditions of the probiotic bacterium Bifidobacterium lactis BB12 and Pediococcus spp., respectively (Table 4.4). 0 1 2:303  T  Tref 1 1 A D 5 Do  exp 2  exp½ 2AðP 2 Pref Þ  @ 2 T Tref ZT  

#21 ð2:303  R  T Þ=ZP ðP2Pref Þ  1 T R "



(4.7)

where Do is the decimal reduction time at reference pressure
temperature conditions (Pref, Tref), zT is the thermal resistance constant ( C), zP is the pressure resistance constant (MPa), A is the parameter that expresses the effect of pressure on the zT-value, B is the parameter that expresses the effect of temperature on the zP-value, and R is the universal gas constant. Multipulses HP (mpHP) has been studied for the successful inactivation of foodborne pathogens, spoilage microbiota, and microbial spores’ inactivation in a number of food products, including fruit juices, meat, and dairy products. According to Buzrul (2014), there are five different patterns of mpHP: (1) the mpHP treatment that consists of three successive single-pulse HP treatments, (2) the mpHP treatment without holding time that is, treatment consists of three successive compressions, followed by decompression, (3) the mpHP treatment that consists of only one compression and decompression periods but the pressure during holding time period is not constant, (4) the mpHP treatment that consists of two pulses at different levels of pressure, and (5) the mpHP treatment in which shapes of the pulses look like sinusoidal waves. In these processes the factors affecting the rate of microbial

Table 4.3 Decimal reduction times (D-values, min) of selected bacterial strains under several HPP conditions. Microorganism

Food product

Pressure (MPa)

Temperature ( C)

D-value (min)

Reference

Listeria monocytogenesa

Minced beef muscles Fresh pork chops Milk

360 350 600

n.d. 25 Ambient

Carlez, Rosec, Richard, and Cheftel (1993) Mussa, Ramaswamy, and, Smith (1999) Dogan and Erkmen (2004)

Fish slurry White prawn muscles Raw milk cheese Mango juice Whole bovine milk Ovine milk Cheddar cheese Milk Peach juice Orange juice Egg Carrot juice

350 400 300 300 300 450 350 600

Ambient 30 25 Ambient 20 2 20 25

300 300

5 40

5.00 8.52 2.43 1.52 0.87 4.16 5.10 3.60 5.23 3.70 20.0 33.0 1.66 1.22 0.68 3.80 7.90

Cashew apple juice Milk Peach juice Orange juice Milk Orange juice Orange juice

400 600

n.a. 25

300

25

300

25

1.21 3.19 1.50 0.83 9.21 1.50 1.97

300

20

1.07 8.70

Staphylococcus aureusb Escherichia coli

Total aerobic count

Salmonella typhimurium Lactobacillus plantarum Lactobacillus brevis Pediococcus spp. a

Sea bream fillets

Ramaswamy, Zaman and, Smith (2008) Das, Lalitha, Joseph, Kamalakanth, and Bindu (2016) Shao, Ramaswamy and, Zhu (2007) Hiremath and Ramaswamy (2012) Erkmen and Karata¸s (1997) Gervilla, Sendra, Ferragut, and Guamis (1999) O’Reilly, O’Connor, Kelly, Beresford, and Murphy (2000) Erkmen and Dogan (2004)

Dong-Un (2002) Van Opstal, Vanmuysen, Wuytack, Masschalck and, Michiels (2005) Lavinas, Migue, Lopes and, Valentemesquita, (2008) Erkmen and Dogan (2004)

Erkmen (2009) Katsaros et al. (2010)

Tsironi et al. (2015)

As adapted by Baptista, I., Rocha, S. M., Cunha, A., Saraiva, J. A., & Almeida, A. (2016). Inactivation of Staphylococcus aureus by high pressure processing: An overview. Innovative Food Science & Emerging Technologies, 36, 128
149. As adapted by Possas, A., Pe´rez-Rodrı´guez, F., Valero, A., Garcı´a-Gimeno, R. M. (2017). Modelling the inactivation of Listeria monocytogenes by high hydrostatic pressure processing in foods: A review. Trends in Food Science & Technology, 70, 45
55.

b

Table 4.4 Parameters of the multiparameter equation (Eq. 4.7) that describes the decimal reduction time (D-value, min) of selected bacteria at any combination of pressures and temperatures. Parameters

Lactobacillus plantarum

Lactobacillus brevis

Pediococcus spp.

Bifidobacterium lactis BB12 at pH 4.8

B. lactis BB12 at pH 6.5

Do (min) zT ( C) zP (MPa) A (MPa21) Tref ( C) Pref (MPa) R2

1.32 6 0.11 18.8 6 1.30 95 (constant) 20.013 6 0.002 30 300 0.977

3.42 6 0.51 23.8 6 1.40 95 (constant) 20.009 6 0.001 30 300 0.951

4.98 40.5 135 (constant) 20.006 30 300 0.998

1.72 6 0.04 26.8 6 1.7 90 (constant) 0.003 6 0.000 30 300 0.983

281 6 19.7 22.9 6 3.50 140 (constant) 0.002 6 0.000 25 200 0.957

Source: Adapted from Katsaros, G. I., Tavantzis, G., & Taoukis, P. S. (2010). Production of novel dairy products using actinidin and high hydrostatic pressure as enzyme activity regulator. Innovative Food Science & Emerging Technologies, 11(1), 47
51; Katsaros, G. I., Tsevdou, M., Panagiotou, T., & Taoukis, P. S. (2010). Kinetic study of high pressure microbial and enzyme inactivation and selection of pasteurisation conditions for Valencia orange juice. International Journal of Food Science & Technology, 45, 1119
1129; Tsevdou, M., & Taoukis, P. (2011). Effect of non-thermal processing by high hydrostatic pressure on the survival of probiotic microorganisms: Study on Bifidobacteria spp. Anaerobe, 17(6), 456
458; Tsironi, T., Maltezou, I., Tsevdou, M., Katsaros, G., & Taoukis, P. (2015). High-pressure cold pasteurization of gilthead seabream fillets: Selection of process conditions and validation of shelf life extension. Food & Bioprocess Technology, 8, 681
690.

High hydrostatic pressure processing of foods

97

inactivation include pressure, temperature, pulse number and pulse holding time, pulse shape, and compression and decompression rates. The majority of the studies related to mpHP treatment indicate that the achieved inactivation of viruses, yeasts, and bacterial cells, fungal and/or bacterial spores is significantly higher than that achieved with single-pulse HP. However, there are questions with regard to mpHP feasibility, being a more expensive and difficult to control technology that could potentially be considered in the cases where HTHP treatment is required.

4.3.2 The effect of high pressure on enzymes HP application is very effective in enzyme inactivation (Hendrickx & Knorr, 2002) and involves a series of events like formation and/or disruption of numerous interactions, changes in the native structure of enzymes by folding or unfolding. Pressure-induced enzyme inactivation has also been attributed to pressure-induced changes in substrate
enzyme interactions. The effect of HP on food endogenous enzymes is linked to a series of food quality attributes (Hendrickx & Knorr, 2002). Several studies are focused on modeling the inactivation/activation kinetics of enzymatic activity in the pressure domain of 100
1000 MPa for a wide range of food enzymes including polyphenol oxidases (Buckow, Weiss, & Knorr, 2009; Moralesde la Pen˜a, Salinas-Roca, Escobedo-Avellaneda, Martı´n-Belloso, & Welti-Chanes, 2018), pectin methylesterases (PMEs) (Alexandrakis, Kyriakopoulou, & Katsaros, 2014; Boulekou, Katsaros, & Taoukis, 2010; Guiavarc’h, Segovia, Hendrickx, & Van Loey, 2005; Katsaros, Alexandrakis, & Taoukis, 2016; Ly Nguyen, Van Loey, Smout, Verlent et al., 2003; Ly Nguyen, Van Loey, Smout, Ozcan et al., 2003; Polydera, Galanou, Stoforos, & Taoukis, 2004; Plaza et al., 2007), peroxidases (Garcia-Palazon, Suthanthangjai, Kajda, & Zabetakis, 2004; Terefe, Yang, Knoerzer, Buckow, & Versteeg, 2010), cysteine proteases (Katsaros, Katapodis, & Taoukis, 2009a,b), and aminopeptidases (Giannoglou et al., 2018). The HP conditions based on such modeling can be calculated to achieve controlled inactivation or increase of activity of enzymes necessary in the context of HP pasteurization but also in the cases where selective modulation of enzyme activity is sought to improve products. Examples of the latter are cheese maturation acceleration by affecting starter culture enzymes (Giannoglou et al., 2016), increased tomato juice viscosity at lower Brix (Andreou, Dimopoulos, Katsaros, & Taoukis, 2016), enzymatic debittering of citrus juices (Gogou, Orfanoudaki, Tsimogiannis, & Taoukis, 2016) or control of proteolysis in cheeses made with plant “rennet” ingredients (Katsaros, Tavantzis, & Taoukis, 2010). HP enzyme inactivation often follows first-order inactivation kinetics (Eq. 4.7). However, different heat and/or pressure resistance behavior has been observed for different enzymes or different isoenzymes. The existence of two isoenzymes exhibiting different pressure resistance has been mathematically described by the development of a biphasic model signifying the coexistence of at least two isoenzymes, a pressure-resistant and pressure-labile one. In the case of fractional conversion model (Eq. 4.8), first-order inactivation is applied taking into account a nonzero residual activity upon prolonged processing.

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Green Food Processing Techniques

The inactivation of enzymes can often be described by a first-order kinetic model but in the case of the fractional conversion model for all pressure
temperature conditions, Eq. (4.8) could be used:
ln

A 2 Af Ao 2 Af

 52k  t

(4.8)

where A is the enzyme activity after processing for a treatment duration t, Af is the residual activity after processing, Ao is the initial activity, t is the processing time (min), and k is the inactivation rate constant (min21). This kinetic equation can model effectively the loss of enzyme activity during processing, describing a first-order inactivation of the pressure-labile isoenzyme and the presence of a baroresistant enzyme fraction largely unaffected by the process pressure or temperature. PME is a representative case of a plant origin enzyme that has been thoroughly studied in terms of HP inactivation kinetics by several research groups. PME is present in fruit and vegetable processing, which mainly affects fruits/ vegetables texture and fruits/vegetables juice rheological properties lowering their viscosity by destabilization of clouds. A significant number of publications are describing the synergistic effect of pressure and temperature on PME activity for a wide range of fruits and vegetables and their products including citrus-based foods (Alexandrakis, Katsaros, & Stavros, 2013; Guiavarc’h et al., 2005; Polydera et al., 2004; Sampedro, Rodrigo, & Hendrickx 2008; Van den Broeck, Ludikhuyze, Van Loey, & Hendrickx, 2000b), tomato-based foods (Plaza et al., 2007; Rodrigo et al., 2006; Stoforos et al., 2002; Van den Broeck, Ludikhuyze, Van Loey, & Hendrickx, 2000a; Verlent, Hendrickx, Verbeyst, & Van Loey, 2007), peach (Boulekou et al., 2010), strawberry (Cano, Herna´ndez, & De Ancos, 1997; Ly Nguyen et al., 2002), pepper (Castro, Saraiva, & Lopes-da-Silva, 2008; Castro, Van Loey, Saraiva, Smout, & Hendrickx, 2006), carrot (Balogh, Smout, Ly Nguyen, Van Loey, & Hendrickx, 2004; Ly Nguyen et al., 2002b; Sila et al., 2007), banana (Ly Nguyen et al., 2002a; Ly Nguyen, Van Loey, Smout, Verlent et al., 2003), apple (Riahi & Ramaswamy, 2003), persimmon (Katsaros, Taoukis, Katapodis, & Boulekou, 2005), and sea buckthorn (Alexandrakis et al., 2014). The comparison of published results indicates that PME-specific origin, fruits/vegetable variety, and cultivars result in different inactivation kinetics (Katsaros et al., 2016). It has been established that PMEs pressure resistance can vary by several orders of magnitude ranging from pressure-sensitive types such as orange juice (Valencia cv.) PME to highly barotolerant ones such as persimmon juice PME (Hachiya cv.). As depicted in Table 4.5, PMEs from different sources and varieties show different inactivation kinetics in HP treatments. In general, when pressure is combined with mild heating, a synergistic effect of pressure and temperature with regard to enzyme inactivation is expected. However, when pressure is combined with high temperatures ( . 70 C), an antagonistic effect of pressure and temperature may be observed. Polydera et al. (2004) studied the HP

Table 4.5 High-pressure inactivation rate constant of pectin methylesterase in different fruit sources and varieties. Fruit

Persimmon

Orange

Orange

Blood orange

Tangerine

Peach

Strawberry

Apricot

Raspberry

Variety

Diospyros

Navel

Valencia

Sanguinello

Optanik

Everts

Camarosa

Bebekou

Inactivation rate constant kPref ;T ref (min21) Pref (MPa) Tref ( C)

0.016

1.760

1.590

1.345

0.083

0.154

0.048

0.070

Rubus idaeus 0.041

600 50

600 50

200 40

500 30

200 30

600 50

800 65

600 65

600 50

Source: Adapted from Katsaros, G., Alexandrakis, Z., & Taoukis, P. (2016). Kinetic assessment of high pressure inactivation of different plant origin pectin methylesterase enzymes. Food Engineering Reviews, 9, 170
189.

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Green Food Processing Techniques

inactivation of orange juice (Navel cv.) PME and found a synergistic effect of pressure and temperature on this enzyme under HP processing conditions, except in the high-temperature
low-pressure region where an antagonistic effect was noted. Boulekou et al. (2010) investigated the inactivation of endogenous PME peach pulp under HP (100
800 MPa) combined with moderate temperature (30 C
70 C). HPHT acted synergistically on PME inactivation, except at the temperature of 70 C at 100
600 MPa, where P and T acted antagonistically. Pressure stability of enzymes is largely varied dependent on the type of enzyme, the presence of other enzymes, type of substrates, ionic strength, pH, nature of the medium in which the enzyme is dispersed, pressure, temperature, and treatment time (Cheftel, 1991; Irwe & Olsson, 1994). The multiparameter model given in Eq. (4.9) can be used to express the enzyme inactivation rate constant as a function of temperature and pressure process conditions, taking into account the dependence of both activation energy and activation volume on pressure and temperature, respectively, allowing the quantitative estimation of the HPHT conditions needed to achieve adequate enzyme inactivation in the target food system. 1  0 Ea;Pref 2 B  ðP 2 Pref Þ 1 1 A kP;T 5 kref P;T  exp 2 @ 2 R T Tref # Va;Tref 1 A  ðT 2 Tref Þ  ðP 2 Pref Þ 2 RT " 

(4.9)

where kref P;T is the inactivation rate constant at reference HP processing conditions (min21), Ea is the activation energy (kJ/mol), Ea;Pref is the activation energy at Pref (kJ/mol), Va is the activation volume (mL/mol), and Va;Tref is the activation volume at Tref (mL/mol). Effectively the selection of the optimal process conditions should take into account the simultaneous sufficient inactivation of the two target indices that is, microorganisms and enzymes. Katsaros et al. (2010) as case study modeled and calculated the required HP process conditions for the cold pasteurization of Valencia orange juice. Both the most barotolerant microorganisms that is, lactic acid bacteria (LAB) and PME appeared to be inactivatable at pressures above 300 MPa. Valencia orange PME is one of the most pressure-labile PME enzymes (Table 4.5) and hence the general rule that treatment for adequate PME inactivation is sufficient for juice pasteurization might not apply. Thus a selection of an adequate moderate HPHT process condition, effective for the inactivation of both factors, is necessary for the process design of the pasteurization of Valencia orange juice. For pasteurization, inactivation of 90% of PME and a 7D reduction of the most resistant LAB was applied as process target (Fig. 4.1). The required processing times for pasteurization of Valencia orange juice PME at different process pressures at 25 C and 30 C are shown in Fig. 4.2. Processing at 25 C requires longer times for the inactivation of LAB species up to 250 MPa, while

High hydrostatic pressure processing of foods

101

Figure 4.1 Required processing time for the inactivation of PME and LAB as a function of pressure at 25 C and 30 C. Dashed lines represent a 7D LAB reduction and solid lines represent 90% PME inactivation. Black lines show processing at 25 C, gray lines show processing at 30 C. LAB, Lactic acid bacteria; PME, pectin methylesterase.

Figure 4.2 World growth of the food industry use of high-pressure processing technology. Source: Tonello, S. (2018). Commercial applications of HP & irradiation. In IFT-EFFoST 2018 international nonthermal processing workshop. Sorrento
Salerno, Italy.

for higher pressures the process time for the inactivation of PME is longer. At 30 C the respective pressure, at which the PME process time exceeds the time required for microbial inactivation, is 300 MPa. The cross of PME and LAB curves for processing at 25 C (250 MPa pressure for 34 min) and 30 C (310 MPa pressure for 4 min) would be the required process condition to ensure the targeted PME and LAB inactivation.

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Green Food Processing Techniques

4.3.2.1 High pressure
assisted enzymatic protein hydrolysis Although HP processing is mainly used to inactivate deteriorative enzymes in order to extend food shelf life, other enzyme-related applications have been researched. One of the more recent findings in literature is focused in improving the efficiency of enzymatic hydrolysis of plant-based food proteins such as lentil (Garcia-Mora, Pen˜as, Frias, Gomez, & Martinez-Villaluenga, 2015), flaxseed (Franck et al., 2018), and whey proteins (Ambrosi, Polenta, Gonzalez, Ferrari, & Maresca, 2016). Enhanced enzymatic hydrolysis under HP conditions is considered to be induced via HP-induced partial protein unfolding which further facilitates access for the involved enzymes to protein cleavage sites. Cleavage sites enhanced access is expected to lead to an increase of enzyme activity, thus to an enhanced degree of hydrolysis (Bonomi et al., 2003). Several studies showed that HP-assisted enzymatic hydrolysis induced generation of bioactive peptides (BPs) due to an HPinduced enhancement of peptide release. According to a recent study of Franck et al. (2018), an HP-assisted enzymatic hydrolysis could be used to improve hydrolysis kinetics of flaxseed proteins. HP-induced enzymatic hydrolysis could lead to a greater proportion of low-molecular-weight peptides (,10 kDa), which is usually correlated with an increase in bioactivity (Lozano-Ojalvo, Pe´rez-Rodrı´guez, PablosTanarro, Lo´pez-Fandin˜o, & Molina, 2017; Zeece, Huppertz, & Kelly, 2008). HPinduced enzymatic hydrolysis of a wide range of plant-based food proteins could lead to a new application domain of HP that involves a simultaneous pressurization and enzymatic hydrolysis as a viable process to produce bioactive hydrolysates, increasing the efficiency of enzymatic hydrolysis, improving BP yields, and enhancing protein digestibility. More information on BPs and HP is provided in the next section.

4.3.3 The effect of high pressure on nutritional characteristics of foods Besides the advantages of extending shelf life of food products, HP is considered a processing method that leads to maintenance or improvement of the functional content of foods, thus enhancing the nutritional value of the processed foods without the need of addition of nutrients and allowing the increase of nutrients intake (Huang, Wu, Lu, Shyu, & Wang, 2017). In the following sections a review of the effect of HP on the nutritional value of foods is presented, taking into consideration a wide range of nutrients as well as the changes induced by HP processing that leads to increased bioavailability and bioaccessibility of functional food ingredients, and reduced activity of certain allergens.

4.3.3.1 Polyphenols and antioxidant capacity of foods Carotenoids, flavonoids, and polyphenols are the most studied bioactive compounds (BACs) of food products. At present, research on the effect of HP technology on BACs is related to its feasibility to become an environment-friendly extraction

High hydrostatic pressure processing of foods

103

method aimed to the reduction of the required energy and use of organic solvents. This potential application of HP will be discussed in more details in Section 4.4. With regard to the retention of L-ascorbic acid (vitamin C), several studies have been conducted. The study of HP on the loss of vitamin C in orange, apple and apple purees, citrus juice, carrots, tomato, strawberries, and strawberry purees showed no significant difference in vitamin C content after HP processing as compared to unprocessed samples. However, vegetables are reported to exhibit lower retention of vitamin C compared to fruits after HP treatment (Mahadevan & Karwe, 2016). In general, L-ascorbic acid remains mostly unaffected after HP when processing is conducted at low or mild temperatures (,60 C) and decreases when HPs in combination with high temperatures are applied. A comparative study of the effect of HP and thermal pasteurization on the vitamin C content of fresh Navel orange juice during storage showed that the rate of vitamin C loss of HP-treated orange juice was lower compared to conventionally pasteurized juice at refrigeration temperatures. Thus the benefit in HP-treated food products with regard to degradation of vitamin C extends to postprocessing storage at low temperatures (Polydera et al., 2004) throughout the achieved extended shelf life.

4.3.3.2 Bioactive peptides BPs usually sized from 2 to 23 amino acids are inactive within the native protein sequence but may be released by enzymatic hydrolysis or fermentation through the action of digestive proteases or proteolytic starter cultures, respectively. Once they are released, they exhibit biological activity, that is, antimicrobial, antihypertensive, antidiabetic, antithrombotic, and immunomodulatory activities (Korhonen, 2009). The largest category of BPs precursors include milk and egg proteins, followed by meat, marine, and plant proteins that also have high protein content and thus are sources of high value-added ingredients (Bah, Bekhit, Carne, & McConnell, 2015; Lafarga & Hayes, 2014). The effect of HP on BPs is directly related to the pressure-induced unfolding of food proteins, and hence exposure of their active sites to enzymes, leading to improvement of protein susceptibility to fermentative or direct enzymatic hydrolysis. As a result, HP pretreatment of food proteins or simultaneously to protein hydrolysis can be a practical tool for the production of BPs from a large variety of food proteins. Recently, Marciniak, Suwal, Naderi, Pouliot and, Doyen (2018) collected all data related to HP application and its effect on the production of BPs from various foods in the last 15 years (Table 4.6).

4.3.3.3 Minerals content The main minerals, important for human growth and metabolism and often prone to deficiency, include calcium, phosphorous, potassium, magnesium, iron, and zinc. Even if humans consume products that comprise the above nutrients, these minerals may be in inadequate proportions in foods, or their bioavailability and bioaccessibility might be compromised. It is well established that HP does not affect minerals;

Table 4.6 Examples of the effect of high-pressure (HP) application on the production of bioactive peptides (BPs) from various protein sources. Protein source

Milk

HP conditions

Enzyme used for hydrolysis

Results

Reference

β-lg

100
300 MPa/10
20 min (S)

Pronase and α-chymotrypsin

Increased rate of hydrolysis Best hydrolysis rate at 100 MPa

β-lg B

150
450 MPa/15 min (P)

β-lg

600 and 800 MPa/10 min (S)

Trypsin, chymotrypsin, and protease from Bacillus licheniformis Pepsin

β-lg

400 and 600 MPa/10 min (P)

Trypsin

Bovine serum albumin

100
500 MPa/15
25 min (S)

Trypsin and α-chymotrypsin

Whey protein isolate

300 MPa/15 min 25 C (S)

Trypsin

Increased rate of hydrolysis at 300 and 450 MPa. Increased production of specific peptides Total hydrolysis at 1 min at 600 and 800 MPa Peptides generated were ,1.5 kDa Modification of peptide profile at both 400 and 600 MPa Improvement of peptide yield 400 MPa generated more BPs Decreased digestibility at .400 MPa Increased rate of hydrolysis at 400 MPa Increased rate of hydrolysis

Izquierdo, Alli, Go´mez, Ramaswamy, and Yaylayan (2005) Knudsen, Otte, Olsen, and Skibsted (2002)

αs-CN

200 and 600 MPa/5 and 15 min (S) 2 3 2.5 min or 3 3 5 min (S)

Pepsin
pancreatin

Casein

25
200 MPa/15
120 min (S)

Elastase, flavourzyme

400 MPa/30 min/37 C (S)

Savinase, thermolysin, and trypsin Pepsin

Whey proteins

Higher ferric-reducing antioxidant bioactivity Single cycle 200 and 600 MPa more efficient. Antihypertensive properties at 600 MPa/5 min Antioxidant activity at 600 MPa/15 min Increased degree of hydrolysis, DPPH and superoxide radical scavenging capacity, and antiinflammatory activity using flavourzyme and trypsin (100 MPa
1 h)

Increase in ,10 kDa peptide content (50%) and total absence of allergen

Zeece et al. (2008)

Boukil, Suwal, Chamberland, Pouliot, and Doyen (2018) De Maria, Ferrari, and Maresca (2017) Blayo, Vidcoq, Lazennec, and Dumay (2016) Hu et al. (2017)

Bamdad, Shin, Suh, Nimalaratne, and Sunwoo (2017)

LozanoOjalvo et al. (2017)

Egg

Plant

Meat

Ovalbumin

200
400 MPa/60 min (S)

Chymotrypsin and trypsin

Production of antihypertensive peptide

Ovalbumin

400 MPa (S)

Pepsin

Isolated pea protein

200
600 MPa/5 min/24 C (P)

Alcalase

Sweet potato

100
300 MPa/30
60 min/57 C (S)

Alcalase

Pregerminated black soybean

50
150 MPa/12
24 h/57 C (S)




Pork

600 MPa/6 min (P)

Lysosomal enzymes

Bovine collagen

600 MPa/15 min (P)

Alcalase, collagenase, thermolysin, proteinase K, pepsin, and trypsin

Difference in peptide profile (specifically at acidic pH) Best ACE-inhibitory activity at 600 MPa and low enzyme concentration. HHP increased renininhibitory activity at low enzyme concentration. 200 MPa increased the generation of low-molecular-weight peptide Increase in degree of hydrolysis, antioxidant activity and ,3 kDa peptide content HHP treatment increased ,3 kDa peptides, free amino acid content, and antiinflammatory activity (150 MPa) Increased cathepsin activity. Change in peptide pattern. Enhancement of proteolytic fragments Improvement in degree of hydrolysis for all enzymes. Increased ACEinhibitory activity with Alcalase and collagenase

Quiro´s, Chicho´n, Recio, and Lo´pez-Fandin˜o (2007) Lo´pez-Expo´sito et al. (2008) Chao, He, Jung, and Aluko (2013)

Zhang and Mu (2017)

Zhao, Huo, Qian, Ren, and Lu (2017)

Grossi, Gkarane, Otte, Ertbjerg, and Orlien (2012) Zhang, Olsen, Grossi, and Otte (2013)

P, Pretreated by HP and digested at atmospheric pressure; S, simultaneous HP and enzymatic hydrolysis; DPPH, 2,2-diphenyl-1-picrylhydrazyl; ACE, angiotensin-converting-enzyme; HHP, High hydrostatic pressure. Source: Adapted from Marciniak, A., Suwal, S., Naderi, N., Pouliot, Y., & Doyen, A. (2018). Enhancing enzymatic hydrolysis of food proteins and production of bioactive peptides using high hydrostatic pressure technology. Trends in Food Science & Technology, 80, 187
198.

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however, it affects the food matrix and, consequently, HP could potentially increase their bioavailability and bioaccessibility. Briones-Labarca, Munoz, and Maureira (2011) reported that HP treatment resulted in an improved mineral content of apples when treated at 500 MPa for 2
10 min, leading to an increase in up to 303% for Ca, 11% for Fe, and 28% for Zn, due to the HP-induced damage of plant cell walls, and thus to release of the minerals into the extracellular phase. Lopez-Fandino, la Fuente, Ramos and Olano (1998) also observed an increased content of Ca, P, and Mg in the milk serum when bovine, ovine, and caprine milk was treated at 400 MPa. Regnault, Dumay and, Cheftel (2006) also reported an increased content of Ca and P in milk serum phase 2 h after treating raw skim milk at up to 300 MPa. Zobrist, Huppertz, Uniacke, Fox and, Kelly (2005) observed 12% increase in Ca21 after HP treatment and incubation of milk at 30 C for 15 min, but they reported that the Ca21 content was decreased after 4 h of storage at 20 C. Cilla et al. (2011) studied the effect of HP on the bioavailability of milk minerals and reported that HP treatment at 400 MP and 36 C for 5 min led to increase in Ca and P bioaccessibility and P bioavailability of milk-based fruit beverages. However, they found that Ca solubility and Caco-2 uptake decreased, indicating that even though calcium was in a solubilized form, and thus bioavailable, there might be other factors that affect its uptake.

4.3.3.4 Allergenicity The most common allergens are related to bovine milk (β-lactoglobulin, α-lactalbumin), eggs (ovalbumin), apples (Mal d 1), nuts (Ara h 1), sesame, fish and shellfish (parvalbumins, tropomyosin, arginine kinase, etc.), soy products (Gly m 1-8), and wheat (prolamins and glutelins). Allergenicity of food products may be modified during food processing or even food storage and can either increase or decrease. Since HP affects structural changes in proteins, it has been explored as a process that could modulate food product allergenicity. HP processing of foods may lead to direct decrease of protein allergenicity by unfolding the native structure, or by exposing new regions including allergen epitopes that are further attacked and removed by hydrolytic enzymes. HP has been reported to diminish the allergenic potential of a number of food products (Huang et al., 2014), including fruits, nuts, milk, fish, and soy (Table 4.7). Rastogi (2013) reported that HP treatment in the range of 100
300 MPa in combination with selected proteinases can be considered an effective tool to remove the allergenic activity of whey protein hydrolysate, and thus allowing its use in hypoallergenic infant formulas.

4.3.3.5 Low-sodium products One of the advantages of the application of HP processing in the meat industry is related to the reduction of the salt content in meat products. HP treatment of meat products, such as ham, sausages, etc., may lead to up to 50% reduction in the salt without any defects in terms of sensory acceptance. This potential application of

High hydrostatic pressure processing of foods

107

Table 4.7 Effect of high pressure (HP) treatment on allergens in different foods. Food allergen source

HP conditions

Main observations

Apple

600 MPa/RT/5 min

Structural alteration of Mal d 1 detected by circular dichroism and FTIR Hyposensitization of patients against apple allergy after 3 weeks of immunotherapy with HPtreated apple samples IgE-binding capacity of Mal d 1 was not affected

600 MPa/RT/5 min

400
800 MPa/ 60 C/10 min 150
700 MPa/ 20 C/10 min 400
700 MPa/ 80 C/10 min

Celery

Soybean

Milk

700 MPa/20 C/ 60 min 700 MPa/115 C/ 10 min 100
1200 MPa/ 30 C/5 min 500 MPa/50 C/ 10 min 700 MPa/118 C/ 10 min 300 MPa/40 C/ 15 min 200
600 MPa/ 25
68 C/ 10
30 min

100 MPa/RT/ 20 min

500 MPa/40 C/ 30 min

Minor changes in structure and allergenicity of Mal d 1b; Mal d 3 unaffected Immunoreactivity of Mal d 3 was reduced by 50%
60%. Mal d 1b only showed minor structural and immunoreactivity changes. Changes were attributed to aggregation and heat during treatment 30% decrease of immunoreactivity of Mal d 3. No significant reduction of Mal d 3 75% loss of Mal d 1 and Api g 1 reactivity Mal d 1 irreversibly unfolds at pressures of 150
250 MPa as detected in vitro by FTIR No significant change of Api g 1 allergenicity; however, structural changes observed CD Some changes and reduction of Api g 1 allergenicity Treatment resulted in a significant decrease in allergenicity of soybean sprout proteins while the nutritional value was largely retained The antigenicity of β-lactoglobulin increased with an increase in pressure and holding time, but decreased with increasing treatment temperature. Antigenicity of β-lg in milk increased up to 14fold after treatment at 600 MPa/25 C/10 min compared to untreated milk HP treatment of milk in the presence of chymotrypsin and trypsin accelerated the proteolysis of β-lg, resulting in a rapid decrease of allergenic potential. However, some hydrolysates retained some residual IgE-binding properties that could be traced to the preferential release Tryptic and chymotryptic hydrolysis of β-lg and α-lactalbumin (α-la) under HP significantly decreased residual immunochemical reactivities compared to atmospheric pressure hydrolyzed controls (Continued)

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Table 4.7 (Continued) Food allergen source

HP conditions

Main observations

Prawns

600 MPa/25 C/ 10 min 100
300 MPa/ 20 C/10
60 min 150
700 MPa/ 20
80 C/10 min 500 MPa/37 C/ 10 min

King prawn tropomyosin reactivity was reduced by 63% as detected by ELISA and IgE assays No change of the allergenicity of silver carp allergens was detected by IgE immunoblotting Treatment did not affect structure and allergenicity of Ara h 2, 6 HP treatment alone had no effect on major peanut allergens. However, HP at 500 MPa combined with polyphenol oxidase induced a major reduction of peanut allergens and IgE binding HP treatment did not change allergenicity and IgE-binding capacity of almond proteins Amandin immunoreactivity was undetectable by ELISA in almond milk after all HP treatments. However, this was likely due to the loss of protein solubility (up to 75%), rather than the epitope destruction by HP HP markedly decreased the antigenicity of sesame proteins, especially at 400 and 500 MPa and pH 7 and 10 possibly due to unfolding proteins into a more tightly packed structure obscuring the allergen epitopes

Silver carp Peanuts

Almonds Almond milk

Sesame

600 MPa/4
70 C/ 5
30 min 450 and 600 MPa/ 30 C/ 0.5
10 min

100
500 MPa/RT/ 10 min

FTIR, Fourier-transform infrared spectroscopy; RT, room temperature; IgE, immunoglobulin E; CD, circular dichroism. Source: Adapted from Barba, F. J., Terefe, N. F., Buckow, R., Knorr, D., & Orlien, V. (2015). New opportunities and perspectives of high pressure treatment to improve health and safety attributes of foods. A review. Food Research International, 77, 725
742.

HP, besides the fact of reducing meat products microflora, is based to the changes caused in meat proteins structures, and thus their texture, giving the opportunity to the meat industry to produce healthier products (Barba, Terefe, Buckow, Knorr, & Orlien, 2015).

4.3.4 The effect of high pressure on the shelf life of food products In order to comply with consumer demands for healthy and less processed food products, HP processing has been employed over the last decades, mainly as an alternative to thermal pasteurization of foods. Thermal pasteurization can inevitably induce defects on the quality, for example, texture, color, flavor, nutritional value, and sensorial attributes of foods, which HP processing can potentially alleviate while extending the shelf life of food products.

High hydrostatic pressure processing of foods

109

A wide range of foods, including plant and animal origin food products, have been studied, and their shelf life have been investigated and modeled in order to quantitatively validate the shelf life extension potential that HP provides. In this context, in Table 4.8, the shelf life of a wide range of food products treated at various HP conditions is presented. All experiments were conducted to temperatures up to ambient temperature, in order to be in accordance to the conditions that are used industrially. The mentioned shelf life periods are estimated based on the limits that were set for either microbiological, sensorial, or biofunctional (e.g., retention of vitamin C, viability of probiotic bacteria, etc.) characteristics of the tested products. HP processing extended the shelf life of studied food products from 50% up to sixfold, as compared to products

Table 4.8 Shelf life (days) of a variety of plant and/or animal origin high pressure (HP) treated as compared to untreated food products (representing own experimental data). Food product

HP conditions (MPa/min)

Storage temperature ( C)

Estimated shelf life (days)

Shelf life of untreated product (days)

Bratwurst sausages

600/5

Sea bream fillets

600/5

Pork ham

500/5 600/5 600/5

0 5 10 15 0 5 10 15 4

120 70 26 15 37 27 17 10 67 163 .200 162 62 50 238 164 40 163 147 112 187 109 64 39 35

27 20 14 7 11 7 4 3 20 20 37 21 19 16 140a 104a 20a 184a 110a 76a 88b 58b 39b 26b 20

Turkey ham

Russian RTE deli salad

600/5

Cheese-based RTE deli salad

600/5

Navel orange juice

600/5

Probiotic dairy beverage

200
300/10

a

0 5 10 15 0 5 15 0 5 15 0 5 10 15 4

Values in brackets indicate the shelf life (days) of products containing preservatives. Values in brackets indicate the shelf life (days) of conventionally pasteurized products.

b

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that were conventionally pasteurized or products that contained common preservatives used in the food industry (e.g., nitrates or potassium sorbate). Overall it can be argued that HP processing can be efficiently applied for the manufacture of healthier and clean labeled foods, with superior quality and biofunctional characteristics.

4.4

High pressure technology in combination with other processes and hurdles

HP technology has been effectively applied in combination with other hurdle factors mainly in order to reduce the microbial load of the food products, and thus to extent their shelf life. Such preservation factors include the use of natural compounds or plant extracts, osmotic dehydration, and other novel processes, such as enzyme treatment, pulsed electric fields, and ohmic heating (Bermu´dez-Aguirre, Corradini, Cando˘gan, & Barbosa-Ca´novas, 2016). With regard to the use of antimicrobials, several studies have established that the use of natural antimicrobials, plant extracts, and organic acids, when used combined with HP, is capable to achieve high microbial inactivation, without the need of applying heat, and consequently without the negative effects of thermal treatment on the product quality.

4.4.1 High pressure
assisted extraction The use of HP processing for assisting the extraction of intracellular compounds (referred to as HPE) (Murthy, Prasad, Ismail, Shi, & Jiang, 2016; Shouqin, Junjie, Changzhen2004) is an emerging trend, compared to the technology’s already long existence. The first recorded use of HP extraction was by Shouqin et al. (2004) who discussed the application of HP for the extraction of essential components from herbs. HPE involves mixing the solid plant material with the solvent, applying the pressure and releasing. After pressure release the solid is removed, and the target compound is recovered from the solvent. In this sense the extraction time coincides with the pressure holding time. This approach has been followed by several authors for the extraction of valuable compounds from biomass such as ginsenosides from ginseng (Lee et al., 2011; Shouqin, Ruizhan, & Changzheng, 2007), polyphenols and caffeine from tea leaves (Jun, 2009; Jun, Deji, Ye, & Rui, 2011; Xi et al., 2009), anthocyanins from grape by-products (Corrales, Garcı´a, Butz, & Tauscher, 2009; Corrales, Toepfl, Butz, Knorr, & Tauscher, 2008), carotenoids from tomato waste (Strati, Gogou, & Oreopoulou 2015), pectins from orange peel (Guo et al., 2012), flavonoids from propolis (Shouqin & Jun, 2005), and polyphenols from Maclura pomifera fruits (Altuner, Islek, C¸eter, & Alpas, 2012). The main advantages advocating the use of HP extraction are increased extraction yields and shorter processing times compared to conventional extraction techniques, the use of mild temperatures allowing the recovery of thermolabile compounds, the lower energy consumption compared to thermal extraction, and in some cases the extraction selectivity.

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111

Concerning the higher extraction yields achieved, the improved extraction observed by HP treatment has been mainly attributed to the disruption of cellular structures. Although proteins and cell structures are affected by pressure, the structure and biological activity of compounds remain unaffected (Do¨rnenburg & Knorr, 1993; Lopes, Valente Mesquita, Chiaradia, Chiaradia, & Fernandes, 2010). HP induces profound changes in the molecular organization inside the cells. Prestamo and Arroyo (1998) observed the collapse of cells, the loss of turgor, and the presence of intercellular fluid in HP cauliflower and spinach. Similar results were obtained by Xi et al. (2009) who studied the structure of pressure-treated tea leaves with SEM and TEM. Perrier-Cornet, Mare´chal, and Gervais (1995) observed a leakage of intracellular solutes during the pressure holding time when treating yeast cells. Do¨rnenburg and Knorr (1993) observed an increased release of pigments from cultured cells of Chenopodium rubrum and Morinda citrifolia at pressures exceeding 50 MPa. Shimada et al. (1993) observed leakage of proteins, amino acids, and metal ions from yeast cells for treatment pressures up to 600 MPa. Disruption of cellular organelles such as the vacuole, the mitochondria, and the nuclear envelope was also observed at pressures exceeding 400 MPa. Such structural alterations are responsible for the increased extractability of target compounds. Apart from cellular disruption, Shouqin et al. (2004) have also proposed the increased solvent permeation and the increased solute solubility under HP as possible driving forces for the increased extractability, while Corrales et al. (2009) suggested that the decrease in the polarity of water under HP (Fernandez, Goodwin, Lemmon, Levelt Sengers, & Williams, 1997) may be responsible for the improved extraction yields of compounds such as flavonols and anthocyanins. HP extraction also proves to be an environment-friendly technique. This stems from the fact that the yield increases achieved can lead to lower solvent consumption and the implementation of lower extraction temperatures. More importantly, the main difference between pressurizing and heating an aqueous system lies in that the specific work required to pressurize water up to 800 MPa does not exceed 55 kJ/kg (Toepfl, Jayas, & Holley, 2006), while the heating of water requires approximately 42 kJ/kg for every 10 C of temperature increase. In some cases, HP extraction also offers the benefit of selective extraction while keeping the extraction of impurities low (Shouqin et al., 2004). Corrales et al. (2008) studied the HP extraction of anthocyanins from grape by-products and found that the extraction yield for each compound was dependent on their chemical structure with acrylated anthocyanin glucoside extraction being favored by HP. Guo et al. (2012) found an increase in pectin viscosity extracted from citrus peels that depended on applied pressure. Apart from the approach where the extraction takes place concurrently with the pressurization, it is also possible to take advantage of the cellular disruption caused by HP. In this sense, HP treatment is applied as a pretreatment to cells or plant tissues, with a subsequent extraction step necessary to obtain the compounds of interest. Andreou et al. (2017) applied HP processing (200
600 MPa, 1
5 min) as a pretreatment on whole olive fruits with the aim of increasing olive oil yield in a subsequent centrifugation step. HP treatment increased both the olive oil yield and

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its oxidative stability, which was attributed mainly to the increase in the total phenolic compounds extracted due to pressure treatment. Dimopoulos, Limnaios, Tsantes, Andreou, and Taoukis (2018) applied an HP pretreatment on yeast suspensions following an autolysis procedure in order to increase the yield of yeast extract. In this case HP affected both cellular permeability and proteolytic enzyme activity, thus leading to accelerated yeast extraction with higher yields.

4.4.2 Application of high pressure in combination with antimicrobials and plant extracts Akdemir Evrendilek and Balasubramaniam (2011) reported that a 5-log reduction in Listeria innocua and L. monocytogenes was achieved, when yoghurt was fortified with mint essential oils and HP treated at 600 MPa for 5 min. Similar results with the added advantage of increasing shelf life of the product for up to 60 days were also observed in the case of combined use of bacteriocins and HP: (1) at 500 MPa for 5 min for the inactivation of Listeria spp. in cheese (Arque´s, Rodrı´guez, Gaya, Medina, & Nunez, 2005), (2) at 200
400 MPa for 10 min for the inactivation of L. monocytogenes and Salmonella enteritidis in cooked ham (Liu et al., 2012), and (3) at 500 MPa for 10 min for the inactivation of E. coli O157:H7 in dry-cured ham (De Alba, Bravo, & Medina, 2013).

4.4.3 Application of high pressure in combination with osmotic dehydration The effect of HP in addition to osmotic dehydration has been studied on sliced (Nunez-Mancilla et al., 2013) and fresh-cut cubes (Dermesonlouoglou et al., 2017) of strawberry fruit, fresh-cut tomatoes (Dermesonlouoglou et al., 2017), and chicken breast fillets (Andreou, Tsironi, Dermesonlouoglou, Katsaros, & Taoukis, 2018). Results have shown that HP treatment at 600 MPa for 5 min of osmotically dehydrated food products leads to an increase in shelf life for up to 10 and 7 months at 5 C in the case of fresh-cut strawberry cubes and fresh-cut tomatoes, respectively, compared to the commercial shelf life of respective available products, usually in the range of 1 week (Dermesonlouoglou et al., 2017, 2017). With respect to animal origin food products, ready to cook, osmotically dehydrated and HPtreated chicken breast fillets exhibited reduced microbial load and improved texture and color, resulting in an increase in the shelf life of the products to 25 days when stored at 5 C as compared to 6-day shelf life of the untreated fillets (Andreou et al., 2018).

4.4.4 Application of high pressure in combination with enzyme pretreatment In several food products such as meat, poultry, fish pastes (e.g., surimi), pasta, bakery, and dairy products, pretreatment with the microbial transglutaminase (TGase)

High hydrostatic pressure processing of foods

113

(mTGase, EC 2.3.2.13) enzyme has been widely used, in order to achieve better texture and sensory characteristics. TGase is a transferase that catalyzes the reaction between the c-carboxyamide groups of peptide bound glutamyl residues (acyl donor) and several primary amines including ε-amino group of lysine, leading to protein cross-linking through the formation of both inter- and intramolecular isopeptide bonds (Motoki & Seguro, 1998). Enzyme pretreatment in many cases is combined with HP processing, since both processes have a great impact on the food proteins functionality, thus their combination results in products with enhanced techno-functional properties due to the formed strengthened protein networks. Most research on the combined effect of mTGase and HP on food quality characteristics is focused on fish pastes such as surimi, where it is shown that as compared to thermal treatment, the HP process results in increase in mTGase affinity to proteins, leading to products with better physicochemical characteristics and firmer gel structure (Cando, Borderı´as, & Moreno, 2016; Herranz, Tovar, Borderias, & Moreno, 2013; Zhu, Lanier, Farkas, & Li, 2014). Similar results were observed with respect to the combined application of mTGase and HP in chicken meat (Trespalacios & Pla, 2007a,b), dry-cured ham (Fulladosa, Serra, Gou, & Arnau, 2009), and porcine plasma (Fort, Kerry, Carretero, Kelly, & Saguer, 2009). With regard to dairy products, studies have shown that both the simultaneous TGase treatment under HP conditions (Anema, Lauber, Lee, Henle, & Klostermeyer, 2005) and/or the subsequent to HP processing TGase treatment (Tsevdou et al., 2013; Tsevdou, Eleftheriou, & Taoukis, 2013) of milk are capable to cause extensive denaturation of whey proteins and dissociation of micelles, reforming new intra- and intermolecular cross-links and thus leading to strengthened networks with contiguous protein molecules. As a result, yoghurt-making properties of milk, and consequently, whey separation phenomena, postacidification, textural and rheological attributes, sensory characteristics, and flavor evolution and release, in either set or stirred yoghurt final products, are improved.

4.5

Industrial applications of high pressure

Since the early 1990s the first commercially available HP-treated product (jam) was launched in the Japanese market, followed by a great number of various products that were marketed in North America and Europe. From this point the implementation of HP technology in industrial scale, as well as the continuous consumer demand for fresh-like, clean labeled, and healthy food products, became a key factor for the evolution and development of high-performance and stable production operation HP units. The continuing evolution on HP equipment technology led various manufacturers in the United States, Spain, the United Kingdom, Japan, and China to develop the capability of producing HP equipment. HP equipment manufacturers, such as Avure, Resato International, Stansted Fluid Power, Baotou, Kobelco, and Toyo Koatsu, produce laboratory HP equipment with capacities ranging from 0.3 to 10 L

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in order to meet different experimental needs. Avure and Hiperbaric, which have gained most of the market shares (only Hiperbaric’s market share is higher than 50%), developed industrial-scale HP devices with a maximum volume of 525 L and an annual production capacity of approximately 60 million tons (Balasubramaniam, Farkas, & Turek, 2008). By 2017 the number of industrial machines in production reached 422, mostly located in North America and Mexico (54%), Europe (25%), Asia (12%), and Oceania (6%). The categories of food products that are HP processed include meat (25%), juices and beverages (20%), fruits and vegetables (20%), toll processing (23%), seafood (5%), ready meals (4%), and dairy (1%) products (Fig. 4.2). In Table 4.9 the main HP machines manufacturers along with their equipment characteristics are presented. There are two types of industrial HP equipment, either the horizontal or the vertical one (Fig. 4.3). Most of the machines that are used in commercial applications are of the horizontal type due to the facility of loading and unloading containers in the production line. In general the cost of a full set of an HP equipment ranges between US$0.5 and 2.5 million, depending on the characteristics of the provided equipment, that is, capacity, operating parameters, level of automation, etc. In 2015 the global market for HP foods was estimated at about US$9.8 billion, and this amount is expected to exceed US$50.0 billion in 2025 (Huang et al., 2017). According to data presented by Tonello (2018), the global HP food production in 2017 based on global production equipment capacity and average production conditions in different food sectors was estimated to be about 1.5 million tons. In August 2018, Hiperbaric launched the Bulk technology in HP equipment (Fig. 4.4). The company presented two new industrial machines, Hiperbaric 525 Bulk, consisted of one vessel of 525 L, and Hiperbaric 1050 Bulk, with two vessels of 525 L, in which beverages are processed in bulk before packaging. These machines can deliver up to 10,000 L/h, being the world’s largest productivity of an HP processing equipment, since a 90% of vessel filling can be achieved. These machines will give the extra opportunity of further reducing both the processing costs and energy requirements, and they may fit into existing large beverages production lines, while at the same time, will allow the use of any kind of packaging after HP treatment (information available from blog.hiperbaric.com).

4.6

High pressure process design and evaluation

HP processing of food products is a process that has been implemented industrially in the last few years. Although applications are successful and promising for delivering high quality, safe food with extended shelf life design, optimization, and evaluation of HP processes is still under consideration. The development of reliable tools to evaluate the impact of HP processing is a very interesting research field that a lot of research groups worldwide have addressed. A lot of published data have proven that temperature nonuniformity is expected during HP processes (pasteurization and sterilization). Two promising tools in evaluating temperature

Table 4.9 Main manufacturers of laboratory- and industrial-scale HP equipment and their characteristics. Company

Country

Services

Equipment size (L, MPa)

Mitsubishi Heavy Industries, Ltd. Kobe Steel, Ltd. ABB Pressure Systems Flow International Corporation

JP




JBT—Avure Technologies Inc. ACB Pressure System

US/SE FR

Resato International Elmhurst Research Inc.

NL US

Engineered Pressure Systems Inc. Hiperbaric

BE/US

Manufacturing and developing advanced HPP food processing pressurizers and test systems Commercializes HP food processor for production use, and HPP equipment for R&D Design and manufacture of innovative HPP equipment for scientific research institutes Design and manufacture of advances high-pressure equipment. Offered a safe and reliable hot and cold isostatic presses Manufactures vertical and horizontal oriented HPP equipment batch systems Development of wide range of high pressure equipment, including HYPERBAR pasteurizers. Specialize on manufacture HPP components Specialized in the design and manufacture of high-pressure components Delivers advanced high-pressure food processing equipment, joined with total science, process technology, and engineering support Offers cold, hot, warm isostatic presses, also research, manufacturing, testing

Stansted Fluid Power Ltd.

UK

MULTIVAC

DE

Uhde High Pressure Technologies Baotou Kefa Co. Ltd

DE

55
525 L 600 MPa 10 mL
5 L Up to 1400 MPa Single; 55
350 L Tamdem; 2x350 L 600 MPa


CN

Fresher Evolution HPP

US

UNIPRESS

PL

Designs, manufactures, and markets HPP equipment all over the world. Also is the first company that is launching HPP bulk equipment Offers laboratory and pilot plant instruments for R&D applications in HPP and bioscience Offers package design and packaging films. Also develops HPP process that reduces damage to packaging materials and provides industrial single and tandem automated packaging lines Develops and constructs the overall system of plants, from testing to handling, including designs and supplies all the essential HP components Design and development and sales of HPP equipment for industrial and scientific research institutes Designs and patents a basket antirotational feature that prevents product falling on the floor Designing advanced HPP lab units for research institutes

JP SE US/SE

ES/US

130 L—392 MPa 600 MPa 600 MPa 600 MPa 50
420 L Up to 700 MPa Up to 1400 MPa 22 L 689 MPa 100
900 MPa

30
300 L 600 MPa 175
525 L 600 MPa 1.5 L 500 MPa

BE, Belgium; CN, China; DE, Germany; FR, France; JP, Japan; NL, Netherlands; PL, Poland; SE, Sweden; UK, United Kingdom; US, United States. Source: Adapted from Elamin, W. E., Endan, J. B., Yosuf, Y. A., Shamsudin, R., Ahmedov, A. (2015). High pressure processing technology and equipment evolution: A review. Journal of Engineering Science & Technology Review, 8, 75
83.

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Figure 4.3 Horizontal (A) and vertical (B) type of HP industrial equipment. HP, High pressure. Source: JBT—Avure Technologies Inc. website.

Figure 4.4 HP bulk technology equipment. HP, High pressure. Source: blog.hiperbaric.com.

nonuniformity and its impact in food safety and quality attributes were thoroughly described: development of heat transfer models and pressure
temperature
time indicators (PTTIs). The uniformity of the HP process is under consideration. Studies have demonstrated that during an HP process the adiabatic heat (during buildup) and the heat loss through the HP vessel wall (during holding time) can cause temperature gradients in the processing unit and the processed products (Delgado, Rauh, Kowalczyk, & Baars, 2008; Denys, Van Loey, & Hendrickx, 2000; Otero, Molina-Garcia, & Sanz, 2000). It has been recognized that pressurization and depressurization during the pressure buildup and at the end of the pressure holding time induces a temperature change due to compression and expansion in both the food and the pressure-transmitting fluid. The magnitude of these temperature changes depend on HP process conditions (pressure and temperature applied), rate of compression/decompression, composition of the food, and more specifically on the water content and type of pressure-transmitting fluid.

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117

One important aspect when designing and evaluating an HP process is to identify the thermal effect implied by the pressure treatment. During compression, temperature changes in the sample, and the pressurizing fluid is expected to be different due to the different thermophysical properties of the food sample and the pressuretransmitting fluid. Two methods for temperature uniformity assessment and evaluation in HP processes have been proposed by Grauwet et al. (2012); computational thermal fluid dynamics modeling and simulation of temperature fields, and the use of PTTIs. Expected temperature changes and gradients during HP processes are linked to heat transfer phenomena taking place between the treated food-pressuretransmitting fluid and the pressure vessel wall and pressure surrounding equipment. The aforementioned heat transfer phenomena lead to temperature gradients inside the HP-treated products. This means that HP treatments of food products take place at temperatures different from the initial HP vessel temperature, and this temperature difference is not homogeneous within the HP vessel, resulting in HP-treated food products treated at a pressure in combination with quite different treatment temperatures (Otero, Molina, & Sanz, 2002). Heat transfer phenomena taking place during HP processes have been mathematically modeled by several researchers (Denys, Ludikhuyze, Van Loey, & Hendrickx, 2000; Knoerzer, Juliano, Gladman, Versteeg, & Fryer, 2007; Otero, Ramos, Elvira, & Sanz, 2006; Smith, Knoerzer, Ramos, et al., 2014; Smith, Mitchell, Ramos, 2014). Numerical heat transfer models can be used in conjunction with computational fluid dynamics by several authors (Denys, Ludikhuyze, et al., 2000; Denys, Van Loey, et al., 2000; Ghani & Farid, 2007; Hartmann & Delgado, 2002, 2003; Hartmann et al., 2003, 2004; Infante, Ivorra, Ramos, & Rey, 2009; Juliano, Knoerzer, Fryer, & Versteeg, 2008; Knoerzer et al., 2007; Otero, Ramos, de Elvira, & Sanz, 2007) to predict temperature along with flow distributions within the HP vessel. In most of these works, HP process uniformity was further evaluated in terms of enzyme and/or microbial inactivation distribution in food products and/or system models. In the case of tomato paste, Denys, Van Loey, et al. (2000) confirmed the satisfactory prediction of temperature profiles and gradients during HP processing by means of heat transfer modeling approach enabling process uniformity evaluation. Furthermore, heat transfer model can be combined with inactivation kinetics to serve as a useful tool to evaluate enzyme inactivation uniformity during batch HP processing of foods. Smith et al. (2014) recently published a work where they evaluated the temperature differences taking place during HP processes in vertical and horizontal HP equipment based on developed heat transfer models. As it was demonstrated, horizontal and vertical flows inside a solvent food, undergoing an HP process, are different. This flow difference leads to different temperature distributions, which is potentially challenging for the food manufacturing industry as long as uniformity of HP effects on enzymatic and/or microbial inactivation is required. In this point, it has to be noted that most industrial-scale available HP units have a horizontal orientation. Smith et al. (2014) developed a horizontal heat transfer model by adapting an existing vertical one developed by Infante et al. (2009).

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In general, numerical simulations available through the developed heat transfer models can be coupled with kinetic models of a food quality and/or safety attribute. This approach can serve as an effective tool to evaluate possible nonuniform inactivation of selected quality and/or safety food attribute when subjected to temperature gradients within the HP treatment vessel. Rauh, Baars and, Delgado (2009) explored this approach to evaluate nonuniform inactivation of food quality
related enzymes; α-amylase, lipoxygenase, and polyphenol oxidase. Enzymes (Bacillus subtilis α-amylase and soybean lipoxygenase) showing different pressure/temperature resistance and different inactivation kinetics were used to evaluate the extent of temperature nonuniformity during HP processes and respective impact to the final target enzymes that is, α-amylase, lipoxygenase, and polyphenol oxidase. Published results confirmed that temperature gradients can lead to remaining enzyme activity gradients, which are expected to be broader for enzymes with higher temperature sensitivity that is, enzymes characterized by inactivation kinetics with strong temperature dependence. The effect of varying temperature in HP treatment impact could be alternatively assessed through the development of proper mathematical modeling strategy where temperature variations within the treatment time are taken into consideration. Gogou, Katapodi, Christakopoulos, and Taoukis (2010) proposed a kinetic modeling approach for HP processing evaluation based on the effective temperature concept instead of constant nominal temperature for given HP treatments. The specific approach has been evaluated in several cases of enzyme inactivation (tyrosinase, xylanase, and lipase). It has been demonstrated that it is feasible to develop inactivation kinetic models at nonisothermal condition-isobaric HP processes taking into account the actual temperature history during HP treatments instead of the initial vessel temperature. As expected, difference between the effective temperature and initial vessel temperature values was found to be more pronounced at the higher pressure domain due to increased adiabatic heating phenomena.

4.6.1 High pressure processing impact evaluation The traditional approach of modeling the inactivation kinetics of microorganisms and enzymes under HP has been based on the assumption that inactivation kinetics follows first-order kinetics. Based on this assumption, an analogy between the lethal effect of HP and thermal processes can be alleged. In literature, there are available a lot of kinetic models describing the effect of pressure on the inactivation parameters either in terms of DP and zP values (Eq. 4.10) or in terms of rate constants (k) at specific isobaric pressure conditions and corresponding activation volume values (Va); a term used to describe pressure dependence of inactivation kinetics (Eq. 4.11) in analogy with activation energy (Ea) used to describe the corresponding temperature dependence (Eq. 4.12). DP 5 DPref  10ðPref 2PÞ=zP

(4.10)

High hydrostatic pressure processing of foods



kP 5 kPref

Va P 2 Pref  exp 2  R T

119





kT 5 kTref


 Ea 1 1 2  exp 2  T Tref R

(4.11)

(4.12)

where kP is the inactivation rate constant at pressure P; kT is the inactivation rate constant at temperature T; Pref is the reference pressure; kPref is the inactivation rate at Pref; Tref is the reference temperature; kTref is the inactivation rate at Tref; Va is the activation volume; Ea is the activation energy, and R is the universal gas constant. The above equation kinetics should only be applied to experimental findings only when isothermal and isobaric conditions can be achieved. Several published studies (De Heij et al., 2003; Koutchma, Guo, Patazca, & Parisi, 2005; Stoforos & Taoukis, 1998; Rovere, Gola, Maggi, Scaramuzza, & Miglioli, 1998) have demonstrated that a linear model is suitable to predict the microbial inactivation of G. stearothermophilus and C. sporogenes PA3679 considered as classical surrogates in thermally assisted HP process (when processed at isobaric and isothermal conditions during holding time). Consequently, the approaches used in thermal processing can be applied for HP process evaluation. Pflug’s concept (Pflug & Zeghman, 1985) can be adapted for determining the F-value for the HP pasteurization and sterilization of foods. FPref ;Tref 5

1 kref P;T

  2 ln A=A0 kðT; PÞ  dt 5 kref P;T 0

ðt

(4.13)

4.6.2 Development of pressure
temperature
time indicators In analogy to time
temperature integrators (TTIs) for thermal processes (Hendrickx et al., 1995; Maesmans et al., 1994) the use of PTTIs has been proposed for impact evaluation of HP processes (Van der Plancken, Grauwet, Indrawati, Van Loey, & Hendrickx, 2008). Components with an irreversible change, dependent on both pressure and temperature, which may be correlated to the changes of a target quality/safety attribute undergoing the same HP process are considered to be good candidates for PTTI development. Van der Plancken et al. (2008) have defined PTTI as a small, wireless device that shows a pressure, temperature and time dependent, easily and accurately measurable, irreversible readout to the HP treatment. A PTTI ideally should display a sensitivity of its kinetic parameter to both small differences in temperature and in pressure. Enzymes and microorganisms are considered to be good candidates for the development of PTTI systems. For a candidate PTTI to be used in evaluating HP processes, its temperature and pressure sensitivity should be similar to the respective temperature and pressure sensitivity of the HP

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Green Food Processing Techniques

process target. The HP process target can be either an enzyme or microorganisms (spoilage and/or pathogens) in the case of HP pasteurization. In the case of HP sterilization processes the target is the more thermotolerant spores. Pressure is assumed to be constant and uniform, while temperature is on the one hand not constant (due to adiabatic heating and heat transfer phenomena) and on the other hand has been reported be nonuniform. In order to evaluate the efficiency and validity of a PTTI a validated kinetic model is a prerequisite. Several researchers have proposed different systems to be used as PTTIs; the proposed PTTIs are summarized in Table 4.10. Although most of the proposed PTTI systems are enzymes, other systems like powdered copper tablet (Minerich & Labuza, 2003), microorganisms like C. sporogenes (Koutchma et al., 2005) and starch (Bauer & Knorr, 2005) have also been investigated to be used as PTTIs with the aim to be used as HP process evaluation tools. The successful and reliable use of any proposed PTTI system is expected only when pressure and temperature dependence of the PTTI is similar to the process target (i.e., endogenous enzyme, spoilage, or pathogen microorganism) pressure and temperature dependence; the PTTIs response can be reliably used for HP process impact evaluation. Enzymes are considered to be good candidate PTTIs both for HP pasteurization and HPHT processes where pressure is combined with elevated temperature target in the sterilization of food. In an HPHT process, food products are subjected at HP combined with elevated temperatures including product preheating, adiabatic heating during pressure buildup, pressure holding possibly accompanied by heat exchange between components with a different compression heat, and finally temperature decrease during pressure release accompanied with subsequent cooling (Barbosa-Canovas & Juliano, 2008). For an enzyme-based PTTI to be applicable in HPHT processes, it must be assured that the candidate enzyme is thermotolerant enough to undergo intense HP conditions combined with temperatures exceeding 80 C. The use of thermo- and piezotolerant enzymes as PTTIs can ensure that the PTTI response, remaining enzyme activity, after the HPHT process can be assayed within the respective detection limits in order to be used to determine the impact of the process. Thermotolerance of enzymes can be further enhanced by means of pH adjustment or water activity decrease. Xylanase is another enzyme, which has been considered to be a good candidate for PTTI development (Gogou, Katapodis, & Taoukis, 2010; Vervoort et al., 2011). Xylanases originating from thermophilic microorganisms have been earlier proposed (Gogou et al., 2010) as TTIs for thermal processes due to their enhanced thermal resistance. Gogou et al. (2010) demonstrated that the use of the proposed xylanase-based PTTI allows the prediction of the temperature history of isobaric
nonisothermal HP treatments. The prediction of temperature history during HP processes is essential for processing optimization and quality control of the final food product. According to the results of this study, the effective temperature concept was satisfactorily applied in the laboratory scale HP equipment. The application of the proposed concept in commercial size equipment is of practical interest. Separate enzyme-based PTTIs can be used to estimate the

Table 4.10 Candidate pressure
temperature
time indicators (PTTIs) for high-pressure (HP) process evaluation.

HP treatments at ambient and/or moderate temperature (HP pasteurization processes)

HP treatments at elevated temperature (HPHT processes)

HPHT, High pressure
high temperature.

PTTI system: PTTI response

Pressure domain (MPa)

Temperature domain ( C)

Reference

Bacillus subtilis α-amylase: remaining enzyme activity Milk alkaline phosphatase: remaining enzyme activity Starch: degree of gelatinization Coenzyme Q(0): Q(0) degradation B. subtilis α-amylase: remaining enzyme activity

250
550

25
55

100
800

10
60

100
700 400
800

29
57 40, 80

Ludikhuyze, Van den Broeck, Weemaes and, Hendrickx (1997) Claeys, Van Loey, and Hendrickx (2003) Bauer and Knorr (2005) Ferna´ndez Garcı´a et al. (2009)

400
600

10
40

Bacillus amyloliquefaciens α-amylase: remaining enzyme activity Thermomyces lanuginosus β-xylanase: remaining enzyme activity Ovomucoid system: residual trypsin inhibitor activity

150
680

10
45

100
600

50
70

400
700

99
111

Thermotoga maritima β-xylanase: remaining enzyme activity Clostridium sporogenes: color

500
700

99.4
113.8

Grauwet, Van der Plancken, Vervoort, Hendrickx and, Van Loey (2010); Grauwet, Van der Plancken, Vervoort, Hendrickx and, Van Loey (2011) Vervoort et al. (2011)

600
800

91
108

Koutchma et al. (2005)

Grauwet, Van der Plancken, Vervoort, Hendrickx and, Van Loey (2009a) Grauwet, Van der Plancken, Vervoort, Hendrickx and, Van Loey (2009b) Gogou, Katapodis & Taoukis (2010)

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Green Food Processing Techniques

effective temperature of a given HP process for product units in representative locations in the vessel. Usually in commercial batch processes, HP treatment is applied to packaged food products. A PTTI can be part of the packaging allowing the effective temperature estimation for specific processed products. An approach based on the estimation of the process effective temperature from the PTTIs response can be used in order to evaluate process impact on the target attribute.

4.7

Economical and environmental aspects of high pressure application in the food industry

4.7.1 Economical aspects of high pressure When implementing HP technology, the main costs are related to the equipment supply and installation. The costs of purchasing industrial-scale HP unit range from US$500,000 to over US$2.5 million, depending on the equipment volume capacity and the extent of automation selected, representing about 80% of the total investment for this HP technology. According to Elamin, Endan, Yosuf, Shamsudin, and Ahmedov (2015), this cost can be analyzed as follow: pressure vessel and its components 50%
60%, pumping system 30%
35%, and controlling system with 10%
15%. In addition, the processing costs of HP technology can be summarized as 65%
75% for depreciation, 2%
3% for energy requirements, 22%
33% for maintenance, and 10%
40% for labor costs, depending on HP system automation. The cost per amount of treated product could be considered still high for HP. Hernando-Sa´inz, Ta´rrago-Mingo and, Purroy-Balda (2008) estimated that the cost of HP-treated ready-to-eat meats is between US$0.08 and US$0.22/kg product, under some specific processing conditions (585 MPa, 3 min, and 50% of filling vessel). According to Bermu´dez-Aguirre and Barbosa-Ca´novas (2011), the cost of HP treatment ranges from US$0.05 to US$0.5 per liter or kilogram depending on the selected processing conditions, including process pressure and time, number of cycles, percentages of vessel filling, etc., and lower than the cost of thermal processing (Wang, Huang, Hsu, & Yang, 2016). Later, Koutchma (2014) also reported the same range of cost per amount of treated product, indicating that the technological evolution in HP equipment has led to the reduction of the cost of the treated food products in recent years, making more products accessible to consumers. Although HP technology has been commercialized since the 1990s, the number of installed industrial machines is not very high, as there are only few companies that could support that kind of high capital investment. This is the reason why small food processors have not implemented HP technology in their plant facilities. As a result, major manufacturers of HP equipment decided to market their services rather than their equipment, by offering a charge payable permission toll system to small food processors, in order them to apply a particular treatment to their food products without the need to purchase a full HP unit (Elamin et al., 2015).

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123

4.7.2 Environmental aspects of high pressure Besides the advantages of the cold in-pack pasteurization that leads to elimination of postcontamination, and the minimal effects on nutritional characteristics of food products, HP is considered to be an environment-friendly technology. This is attributed to the fact that HP conducts pressure instantly, functions evenly and for shorter processing times than thermal pasteurization consuming comparatively lower energy, and thus contributes to the protection of the environment. Moreover, inpack pasteurization during HP ensures that the equipment is not polluted and, in addition, the sterilization of packaging with either H2O2 or other chemical agents is not required; therefore HP processing results in a reduction of chemical amounts in the liquid effluents of the industry (Wang et al., 2016). Regarding the required energy, several studies have shown that novel technologies, including HP, reduce the required energy and water consumption. In particular, since HP is applied at much lower temperatures than the ones are used in heat pasteurization processes, the reduction of the total energy consumption in the food industry is estimated to about 25%
30%. The energy requirements at HP processes concern the power needed only for pressure buildup, as a following cooling process is not necessary due to the decompression that decreases the temperature of the food product. And it is worth noticing that cooling systems are usually responsible for 50% of the total energy usage in the food processing (Probst, Frideres, Pedersen, & Amato, 2015). Even in the cases where a combined application of HP and heat may be needed, like for the sterilization of cans, it is reported that the specific energy required could be reduced from 300 to 270 kJ/kg when applying the HP instead of conventional sterilization. This energy may be further reduced to 242 kJ/kg, if a two-vessel system or pressure storage is used, which is equivalent to an additional energy saving of about 20% (Toepfl et al., 2006). With respect to water, in HP industrial applications, it is used as a medium for pressure buildup. This water is normally recycled since it is not in contact with the food, allowing a minimum water consumption. Taking into account that the use of boilers and/or steam generators is eliminated during HP processing, wastewater in the industry is also reduced (Pereira & Vicente, 2010). Another issue related to the environment-friendly character of HP processing concerns the selection of the packaging materials used in this technology. As already mentioned, HP process, like other novel technologies, is applied after the product has been packaged. Several studies have reported that the environmental impact of food products is also influenced by the type of packaging and materials. The packages and/or pouches used for HP are preferable from an environmental viewpoint, as they are light in composition; and hence, the impact of transport on the overall sustainability of the product is reduced (Davis, Moates, & Waldron, 2009; Probst et al., 2015). Last but not least, the environmental impact of HP processing is strongly related to the reduction of food wastes. As it is generally recognized, HP is capable of significantly extending the shelf life of the food product, due to the reduction of pathogenic and spoilage microorganisms and the inactivation of enzymes that are

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responsible for food degradation. The increase in food products shelf life is directly related to the amounts of foods that are disposed not only as manufacturing leftovers but also of them that come from retail due to short shelf life, as well as of those that are discarded in household level. According to statistical data, about 100 million tons of food were discarded in the countries of the EU in 2014, with a per capita waste generation to be amounted for about 95
115 kg/year, needing the usage of around 5% of total energy in the EU food system (Aganovic et al., 2017; Probst et al., 2015). Consequently, the extension of foods’ shelf life through the application of HP and thus the reduction of food waste, mostly when seasonal and/ or easily spoiled products are involved, is of great importance for energy savings in the entire food chain and therefore contributing to environmental protection. Conclusively, HP as a novel food processing technology has an important environmental impact considering that its implementation as a food production process may result in substantial water and energy savings, in efficient use of packaging material, and will allow a significant reduction of food wastes due to the extended shelf life of the processed products.

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High-pressure homogenization in food processing

5

Dominique Chevalier-Lucia and Laetitia Picart-Palmade IATE, University of Montpellier, CIRAD, INRA, Montpellier SupAgro, Montpellier, France

5.1

Introduction

Conventional homogenization processing (pressure up to 50 MPa) was developed in food sector during the last few decades and is now implemented in many food processes. But its development has been recently enhanced by the challenge to ensure the availability of sufficient, safe, nutritious, tasty, and convenient food to the rapidly expanding and more affluent population while achieving sustainability. In fact, the homogenization processing was invented and patented in 1899 by Auguste Gaulin with the aim to reduce and homogenize the size of milk fat globules slowing the fat globule gravity separation and, consequently, extending the milk shelf life (Gaulin, 1899, 1904). This technical discovery, called homogenizer by A. Gaulin, was presented at the 1900 World Fair in Paris which significantly contributed to the development of the homogenization processing at moderate pressure (20
50 MPa) first in the food sector and then in cosmetics and pharmaceutical industries. The general target of conventional homogenization was to disperse nonmiscible phases but also fragment particles in dispersions, stabilize emulsions, and/or develop products with specific rheological properties. In dairy industry, for example, milk previously heated at 60 C
70 C is homogenized being forced under moderate pressure (20
50 MPa) through a narrow opening. The different physical phenomena induced by the resulting pressure drop such as turbulence, shear, and cavitation lead to the fat globule disruption from 1
8 μm in raw milk to 0.3
0.8 μm in conventionally homogenized milk as shown in Fig. 5.1 (Walstra & Jenness, 1984). New opportunities for homogenization processing at higher nominal pressure level were made possible from the 1990s to 2000s due to the progress in high pressure technology such as the development of high pressure intensifiers and the conception of more resistant materials to high pressure. Concurrently, sophisticated homogenization valves have been developed with seats and needles built in ceramic or coated with artificial diamond. Homogenization was therefore possible at high pressure level [up to 150
200 MPa, high pressure homogenization (HPH)] and even at ultra high pressure level [from 250 to 400 MPa, ultra high pressure homogenization (UHPH)]. The HPH and UHPH processes are also known as dynamic high pressure. The advantage to homogenize at high or ultra high pressure level is

Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00005-7 © 2019 Elsevier Inc. All rights reserved.

Green Food Processing Techniques

Gravity separation

Fat globule size

140

High pressure

Ultrahigh pressure

Figure 5.1 Diagrammatic representation of the influence of homogenization processing on the fat globule size and gravity separation according to the pressure level of homogenization. The three ranges of pressure related to conventional homogenization, high pressure homogenization, and ultra high pressure homogenization are represented in order to compare them.

illustrated in Fig. 5.1 taking as example milk fat globule size: the higher pressure is applied, the smaller the fat globules are obtained (Thiebaud, Dumay, Picart, Guiraud, & Cheftel, 2003). Compared to other homogenization processes (laminar or turbulent rotor
stator systems, jet dispersers, membrane or ultrasonic systems), dynamic HPH delivers the highest potential energy of emulsification (ΔP/volume unit of processed fluid) (Schubert, Ax, & Behrend, 2003). As dynamic high pressure was developed to mechanically homogenized emulsions, this process was also implemented to mechanically disrupt cells and consequently recover intracellular biomaterial (Keshavarz, Moore, & Dunnill, 1990). Concurrently to the technical driver, for a little more than a decade, sustainability is also a driver contributing to the development of dynamic high pressure in not only food but also pharmaceutical, cosmetics, biotechnology, and chemical sectors. This processing, as a nonthermal technology, can be considered as a green food processing since its major objective is to process food products ensuring the safety and quality, while limiting the impact on key nutritional and organoleptic parameters and limiting energy, water, and time consumption (Chemat et al., 2017). In this chapter, technological aspects of dynamic high pressure processing will be first presented to explain this continuous processing dedicated to liquid and characterized by the combination of physical, hydrodynamic, and thermal effects. Then, three eco-friendly applications of dynamic high pressure in food sector will be developed to demonstrate that this mechanical processing dedicated to disruption phenomena is a clean and green processing. These eco-friendly applications are: (1) the extraction of natural compounds by disrupting cells or suspended particles, (2) the designing of extremely stable submicron emulsions by reducing the droplet size, and (3) the nonthermal stabilization of liquid foods by inactivating microorganisms and/or enzymes.

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5.2

141

Dynamic high pressure principle and equipment

Dynamic high pressure is a nonthermal mechanical technology dedicated to liquid products. Fig. 5.2A presents a schematic representation of a high pressure homogenizer and Fig. 5.2B proposes the pressure and temperature of the treated liquid. Overall, this processing is composed of two main processing steps: a pressurization step of the processed liquid [Fig. 5.2, (1) and (2)] followed by an extensive pressure drop [Fig. 5.2, (3)] carried out in the disruption system characterized by a specific geometry depending on the equipment manufacturer. This disruption system is a narrow valve with a characteristic dimension of 10
100 μm. The liquid to be treated is brought to high pressure in few seconds using a high pressure generator composed of one or more pressure intensifiers. A single intensifier system is characterized by a pulsating mode due to the pressure and the volume stream fluctuations over time-scale, resulting in a pulsation of the stresses on the processed liquid (Ko¨hler & Schuchmann, 2011). The association of several pressure intensifiers limits the pulsating mode imposed by a single intensifier and allows to establish a quasi-continuous flow.

(A)

Unhomogenized liquid

First stage HP valve (3)

Second stage LP valve (4)

(3’)

(4)

(1)

(1)

(2)

Homogenized liquid

Intensifier

HP pump

(B)

Figure 5.2 (A) Schematic representation of a high pressure homogenizer. (B) Pressure (-) and temperature (--) of the treated liquid during dynamic high pressure processing: (1) feeding of unhomogenized liquid to the intensifier, (2) pressurization step, (3) and (30 ) pressure drop, and (4) cooling.

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During dynamic high pressure processing, sample is subjected to high pressure as in isostatic high pressure processing. In both the technologies, pressure is uniformly applied and pressure induces some compression of aqueous samples (e.g., a 10% decrease in water volume at 300 MPa) but there is no shearing effect or biomolecule covalent bond reduction due to pressurization at the pressure levels applied. Comparing to dynamic high pressure, isostatic high pressure is operated up to 700 MPa in a batch or semibatch mode with process holding time usually in the order of 5
30 min at ambient, low, or mild temperature and liquid or solid food products in their packaging can be processed (Dumay, Chevalier-Lucia, & Lo´pezPedemonte, 2010). The major difference between dynamic high pressure and isostatic high pressure is that dynamic high pressure processing is a continuous process combining pressurization and homogenization, the latter generating shear forces, turbulence, and cavitation when the processed liquid passes throughout the disruption system. Once the liquid has been pressurized, a large pressure gradient is applied in a very short time (milliseconds) by forcing the liquid through the HP valve [Fig. 5.2B, (3)]. The pressure drops from high pressure down to atmospheric pressure inducing a significant increase of the fluid velocity associated with intense shear rates. Rapid increase in fluid velocity and intense velocity gradients take place and were evaluated to reach up to 200
250 m/s and up to 107
109 s21, respectively, in the case of a convergent HP valve with sharp angles (Floury, Bellettre, Legrand, & Desrumaux, 2004). Donsı`, Annunziata, and Ferrari (2013) evaluated a mean velocity from 120 to more than 400 m/s in the case of an orifice gap. In the same time, the kinetic energy is partially converted into heat inducing a short-life heating phenomenon during less than 1 s [Fig. 5.2B, (3)]. The fluid temperature measured immediately at the HP valve outlet increases linearly with the homogenization pressure by 0.1 C
0.2 C per 100 MPa, due to the partial conversion of mechanical energy into heat but also to shear effects. For example, a total jump in temperature by 0.17 C
0.21 C per MPa was therefore measured when processing milk or oil-in-water (O/W) emulsions (Corte´s-Mun˜oz, Chevalier-Lucia, & Dumay, 2009; Datta, Hayes, Deeth, & Kelly, 2005; Picart et al., 2006; Thiebaud et al., 2003). The mechanical energy dedicated to the particle dispersion and the energy dissipated as thermal energy to process different emulsion formulations were evaluated to be 37%
59% and 63%
41% of the total energy input (ΔP), respectively (Corte´s-Mun˜oz et al., 2009). Dynamic high pressure is however recognized as a nonthermal or mild thermal processing since the temperature increase is limited in the amplitude and can be easily controlled by a cooling system located just after the HP valve [Fig. 5.2B, (4)]. After the valve gap, the fluid flows in the chamber where turbulences, cavitation, impacts between particles and against walls occur, as well as recirculation. Fig. 5.3 proposes a summarized presentation of the different physical phenomena occurred in the upstream side, inside, and in the downstream of the disruption system. A multistage configuration is implemented for a number of homogenizers as in Fig. 5.2 consisting in adding a second valve (called low pressure valve) applying a pressure gradient generally as 10% of the high-pressure gradient.

High-pressure homogenization in food processing

Upstream side of the valve

In the valve gap

Pressurisation

Pressure drop (ΔP) Fluid velocity increase  Intense shear rates Elongational stress  Short-life heating

143

Downstream side of the valve

Turbulences  Cavitation  Impacts  Recirculation

Figure 5.3 Synthesis overview of the different physical phenomena occurred in the upstream side, inside, and in the downstream of the disruption system. (A)

(B)

(C)

High pressure (up to 400 MPa)

High pressure

High pressure

v v

v

v

Interaction chamber

v

v

Low pressure

Low pressure

Interaction chamber

Microchannels

vv v

v v

Seat

v

v v Seat

Orifice with a fixed size (100–200 µm)

Gap (few µm)

Impact Body

v

Piston

Low pressure

Figure 5.4 Schematic representations of three different valve geometries: (A) sharp-angle piston HP valve, (B) orifice HP valve, and (C) microfluidizer Y chamber.

Concerning the disruption system, different types of geometrical devices have been designed by manufacturers for (ultra) high pressure homogenizers. They have developed systems characterized by two parameters influencing the disruption efficiency of the process: the specific flow path and gap size. The piston valve and orifice valve (Fig. 5.4A and B) are proposed by Avestin (Canada), APV (United Kingdom), Bee International (United States), GEA Niro Soavi (Italy), Stansted Fluid Power (United Kingdom), and Ypsicon (Spain). The system called

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microfluidizer is marketed by Microfluidics (United States) (Fig. 5.4C). In the case of the piston-gap homogenizer (Fig. 5.4A), the pressurized liquid is forced through a micrometering piston valve adjustable to control the operating pressure at a constant flow rate. Different designs are available for the piston, such as sharp-angle or Y-shape. In the case of an orifice valve characterized by a fixed gap (Fig. 5.4A), the operating pressure is regulated by varying the flow rate. Concerning the microfluidizer disruption system also called counter jet disperser (Fig. 5.4C), the pressurized fluid is forced at a speed up to 400 m/s into a fixed-geometry interaction chamber (Y single- or multiple-slotted chamber) and is divided into two microchannels or bores with a diameter around 300
500 μm. The two fluid streams from the two opposite directions are then collided. The operating pressure is regulated by means of the flow rate as in the case of an orifice valve system. Particular attention will be paid below to the piston-gap homogenizer in this chapter since this technology is at present time the most available at pilot and industrial scale. Only few recent studies have been focused on the comparison of the disruption efficiency of the different geometries (Donsı` et al., 2013). This aspect will be treated in the following subsections dedicated to dynamic high pressure applications.

5.3

High pressure homogenization processing as greener extraction processing

The development of marketable functional foods and nutraceuticals enriched with bioactive micromolecules or macromolecules is of major significance to the food sector. Bioactive substances are particularly prized for their biological activity such as antimicrobial or antioxidant activity and also for their nutritional properties. In recent years, the market demand for bioactives from natural sources has been boosted due to the increasing concerns of consumers about health, safety, naturalness, and also environment and sustainable development (Murphy, McDonnell, & Fagan, 2014). Consequently, the extraction of bioactive molecules from plant tissues, microorganisms, microalgae, and macroalgae has been a growing focus of attention of researchers and manufacturers. Conventionally, cell disruption to release bioactive compounds from the inside cell is performed by physical methods based on mechanical (grinding and milling) or thermal treatments, or by chemical methods. Alternative cell disruption techniques are at present time investigated in food sector (Liu, Ding, Sun, Boussetta, & Vorobiev, 2016; Poojary et al., 2016) and a particular attention is drawn to dynamic high pressure concerning the ecoextraction of valuable bio-compounds from different types of biomass recognized as natural resources (Safi et al., 2017). The disruption of cell membrane by dynamic high pressure is due to the combination of turbulence, high pressure shear, recirculation, and cavitation phenomena but also impingements on the low pressure chamber and allows the nonselective release of the intracellular fluid and also cellular organelles (Middelberg, 1995). The sustainability benefit of dynamic high pressure

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is based on its ability to mechanically disrupt cells under solvent and reagent-free conditions limiting waste to be reprocessed and also without heat treatment. The disruption of microbial cells using conventional homogenization was early investigated in order to extract internal constituents, and particularly intracellular enzymes, from microorganisms (Chisti & Moo-Young, 1986). Several pioneering studies implemented with this objective using conventional homogenizers working at pressure up to 55 MPa have focused on the investigation of the major processing factors causing cell disruption (Brookman, 1974; Chisti & Moo-Young, 1986; Engler & Robinson, 1981). The influence of the process parameters, particularly the operating pressure, the number of passes, and the valve seat geometry on the disruption rate, was highlighted. The application of higher pressure levels, even if it was not technically possible at this period, was considered as an option to increase the degree of disruption while decreasing the number of passes. More recently, with the development of dynamic high pressure equipment working at high pressure ( . 80 MPa), this processing was updated as mechanical pretreatment in the development of sustainable alternatives to conventional disruption of organism cell membrane processing in biofuel sector (Halim, Harun, Danquah, & Webley, 2012; Velazquez-Lucio et al., 2018) and in food processing (Liu et al., 2016; Poojary et al., 2016; Preece, Hooshyar, Krijgsman, Fryer, & Zuidam, 2017; Safi et al., 2017). Concerning these applications, the pressure level applied is mainly not higher than 150 MPa and the gap width of the valve is a limiting technological parameter linked to the size of particles to disrupt. In the microalgae biorefinery, a significant activity consists in developing operation units less costly in the downstream process where the key step is the cell disruption consisting in breaking or weakening the cell wall integrity. First studies were carried out at low concentrated algal dispersions (,5%, w/w dry basis) and have concluded that the energy consumption of dynamic high pressure processing was significantly higher than the potential energy output of algal-derived biodiesel (Coons, Kalb, Dale, & Marrone, 2014). The dynamic high-pressure technology efficiency to disrupt membrane cell is influenced by operating parameters such as pressure level, number of passes (Liu et al., 2016; Shene, Monsalve, Vergara, Lienqueo, & Rubilar, 2016; Spiden et al., 2013), but also by the physical properties of the cell suspension, the macrostructure of cell wall and the age of the culture (Safi et al., 2014; Shene et al., 2016; Spiden et al., 2013). Spiden et al. (2013) have compared the rupturability of three different microalgae (Nannochloropsis sp., Chlorella sp., and Tetraselmis sp.) and a microorganism model difficult to disrupt (Saccharomyces cerevisiae) using dynamic high pressure processing (up to 150 MPa and up to 10 passes). Significant differences of rupture were observed between these four types of cells and the pressure required to achieve rupture of 50% of the cells per pass was estimated to be 17, 107, 138, and B200 MPa for Tetraselmis sp., Chlorella sp., S. cerevisiae, and Nannochloropsis sp., respectively. Such differences could be taken into account to select a disintegration pretreatment for microalgae for industrial process design. Shene et al. (2016) homogenized Nannochloropsis sp., recognized as highly resistant to disruption, at high pressure (up to 230 MPa, up to six passes) and observed

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that the extraction yield of hydrosoluble components was dependent on the operating process parameters that were not observed for the extraction yield of lipids. Yap, Dumsday, Scales, and Martin (2015) investigated the influence of the feed concentration (0.1%
25%, w/w dry basis) on flow rate, power draw, and cell disruption efficiency for Nannochloropsis sp. suspensions homogenization by dynamic high pressure (30
150 MPa). The efficiency of HPH was independent of the homogenizer feed concentration and solely dependent on the pressure level. Concerning the energy consumption, Safi et al. (2017) have quantified the specific energy input based on the inlet pressure, the number of passes, and the pump efficiency expressed per unit of treated biomass for the disruption of Nannochloropsis gaditana treated at a high concentration (100 g/L). They demonstrated that the energy input was correlated to the protein yield. In the same time, dynamic high pressure processing was concurrently compared to pulsed electric field (PEF), bead milling, and enzymatic treatment. In this study, dynamic high pressure was the processing characterized by the lower specific energy input related to the obtained protein yield and an energy cost per unit of released protein evaluated between 0.15 and 0.25 h/kg (compared to 2
20 h/kg in the case of PEF). Dynamic high pressure (150 MPa, 1
10 passes) was also compared to electrically based disruption techniques by Grimi et al. (2014) concerning the disintegration of the same microalgae. Grimi et al. (2014) evaluated that dynamic high pressure required the highest power consumption compared to pulsed electric field, high voltage electrical discharge and ultrasonication. However, dynamic high pressure was the most effective process to extract hydrosoluble components (ionic components, proteins, small molecular weight organic compounds) and also pigments (chlorophylls or carotenoids). Dynamic high pressure processing was also evaluated to up-cycle by-products or coproducts from food processing (Griffin et al., 2016, 2018). In the case of particle size reduction, called nanosizing, dynamic high pressure is applied to reduce the particle size and so increase the exchange surface and consequently the particle activity. By nanosizing bioactive plant material, HPH could be an alternative less time-consuming and costly compared to the conventional protocol requiring extraction, fractionation, and isolation (Griffin et al., 2016). Despite the extraction yield obtained by dynamic high pressure processing, a specific drawback has to be highlighted: this processing induces a total cell disruption and is consequently characterized by a poor selectivity, and downstream processing is required in the case of a high purity objective concerning a target bioactive.

5.4

Dynamic high pressure processing as greener submicron emulsion processing

The primary objective of HPH processing was historically to convert two (or more) immiscible liquids (oil and aqueous phases most often in food applications) into a stable colloidal dispersion composed of droplets dispersed within the continuous

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phase (McClements, 2015). Emulsion is thermodynamically unstable, and different physicochemical mechanisms, such as gravitational separation, flocculation, coalescence, Ostwald ripening, and phase separation, take place and destabilize the colloidal system (McClements & Jafari, 2018). Consequently, the distribution of droplet size is a key feature of emulsion processing since the droplet size determines shelf life stability but also has an impact on the rheological and transport properties of emulsions. When a coarse dispersion of oil in an aqueous phase in the presence of emulsifier is homogenized by dynamic high pressure, oil droplets can be deformed and disrupted to obtain submicron (droplet size below 1 μm) or nanodroplets (droplet size below 200 nm). These submicron or nanoemulsions are characterized by a narrow size distribution greatly reducing aggregation and gravitational separation phenomena during storage, and consequently contribute to a longer shelf life (Tadros, Izquierdo, Esquena, & Solans, 2004). Besides, particular attention is paid at present time to incorporate hydrophobic bioactive compounds in submicron or nanoemulsions to protect and deliver them in foods (Salvia-Trujillo, SolivaFortuny, Rojas-Grau, McClements, & Martin-Belloso, 2017). As nanosized droplets have a higher surface area compared to conventional emulsion droplets, the functionality and absorption of the hydrophobic bioactive compound entrapped in the oil nanodroplets could be improved (Salvia-Trujillo, Qian, Martı´n-Belloso, & McClements, 2013). A greater emphasis has been placed below on emulsions processed at pressure higher than 200 MPa with the aim of obtaining nanoemulsions. Different types of O/W emulsions have been processed by dynamic high pressure (P $ 200 MPa): bovine whole milk, a natural emulsion (D’Incecco, Rosi, Gabassi, Hogenboom, & Pellegrino, 2018; Hayes, Fox, & Kelly, 2005; Hayes & Kelly, 2003; Picart et al., 2006; Thiebaud et al., 2003), soymilk (Cruz et al., 2007; Mukherjee, Chang, Zhang, & Mukherjee, 2017), model emulsions prepared with food-grade ingredients and stabilized by vegetable proteins (Donsı`, Sessa, & ´ vila, Escriu, & Trujillo, 2015), whey proteins (Corte´sFerrari, 2012; Ferna´ndez-A Mun˜oz et al., 2009; Floury, Desrumaux, & Lardie`res, 2000; Hebishy, Zamora, Buffa, Blasco-Moreno, & Trujillo, 2017; Lee, Lefe`vre, Subirade, & Paquin, 2009), or caseinate (Rodarte, Zamora, Trujillo, & Juan, 2018). Several studies have investigated the influence of the processing parameters of dynamic high-pressure processing, such as homogenization pressure level, recycling, one- or two-stage homogenization, initial temperature of the processed fluid, and also the influence of the sample formulation, in order to optimize the manufacturing of kinetically stable nanomicron/submicron emulsions (Donsı` et al., 2012; Dumay et al., 2013; Zamora & Guamis, 2015). The droplet size decreased with increasing homogenization pressure, and therefore the pressure drops across the high pressure valve during a single-stage dynamic high pressure processing. Besides, the particle size distribution was gradually but significantly shifted toward smaller values with the pressure increase. Fat globules size distribution of untreated raw whole bovine milk displayed a main peak with a maximum at B3 μm and a small shoulder at B0.6 μm (Picart et al., 2006). The d4.3 index associated with the size distribution in this case was B3.8 μm (Picart et al., 2006). UHPH at pressure $ 200 MPa induced the disappearance of the main peak

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Green Food Processing Techniques

(B3 μm) characterizing the untreated raw whole milk, and induced a bimodal distribution characterized by a main peak at 0.16 μm and a minor peak at 0.63 μm. The d4.3 index was reduced down to 0.189 μm at 300 MPa (single pass, singlestage) with B93% of the total fat globule volume with a diameter ,0.36 μm (Picart et al., 2006). Similarly, for soymilk, the d4.3 index decreased from 0.55 μm (untreated soymilk) to 0.13 μm at 200 MPa (Cruz et al., 2007). This trend was also observed in the case of model emulsions (Corte´s-Mun˜oz et al., 2009; Ferna´ndez´ vila et al., 2015; Hebishy et al., 2017). However, an increase of droplet/globule A size at 250
300 MPa was in some cases observed indicating an overprocessing, which could be attributed to predominating recoalescence phenomena over droplet/ globule disruption when the energy input increased, or when the concentration of surfactant was no more sufficient to cover the newly created O/W interface (Donsı` et al., 2012; Jafari, Assadpoor, He, & Bhandari, 2008). An insufficient cooling at the outlet of the high pressure valve could also induce the denaturation of proteins ´ vila used as emulsifiers and, consequently, lead to droplet aggregation (Ferna´ndez-A et al., 2015; Hayes et al., 2005). Depending on the mechanical forces involved in droplet splitting in the HP valve (first stage) and the subsequent thermal energy dissipated through the HP valve (i.e., materialized by the temperature jump), it could be useful or not to operate the LP valve (second stage) to limit droplet reaggregation and coalescence (Hayes et al., 2005; Hayes & Kelly, 2003; Picart et al., 2006; Tesch & Schubert, 2002). The design and geometrical characteristics of the disruption system could also influence the efficiency of the emulsification processing by affecting the droplet disruption efficiency. Few studies have however compared the efficiency of different geometries to produce kinetically stable submicron emulsions with homogenizers working at similar homogenization pressure levels and with similar formulation. Donsı` et al. (2012) proposed a comparison between four different configurations of homogenization chamber (three orifice valves and one piston valve) in order to identify the difference of efficiency of these systems. Regarding the emulsification efficiency, there was no significant difference according to the four geometries, but the energy density and the emulsifier properties were key factors. Recycling emulsion through the homogenizer once, twice, or more allows to improve dynamic high pressure efficiency in oil droplet disruption by increasing the residence times of the fluid in the HP valve. Consequently, several successive passes in the homogenizer at moderate high pressure (B200 MPa) decreased both the mean diameter and the width of droplet size distribution. Particularly, 2 2 3 homogenization passes at 200 MPa generated monomodal size distribution with a peak maximum at 138 nm in the case of model emulsions containing 15% 2 45% (w/w) vegetable oil and stabilized with whey proteins (Corte´s-Mun˜oz et al., 2009). In addition to the process parameters, emulsion formulation strongly influences high pressure efficiency. Particularly, increasing the viscosity of the untreated fluid could favor the droplet disruption through higher extensional stress in the valve gap (laminar flow) and also weaken recoalescence phenomena through collisions between droplets and/or impacts against the chamber walls at the HP valve outlet (turbulent or transitional flow) (Corte´s-Mun˜oz et al., 2009; Diels, Callewaert,

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Wuytack, Masschalck, & Michiels, 2005). Besides providing kinetically stable emulsions, dynamic HPH also allows to produce emulsions with a large range of flow behaviors (i.e., from highly fluid to highly thick samples) when combining the pressure level of homogenization and the oil volume fraction. The emulsion viscosity was generally increased with the homogenization pressure and the number of homogenization passes since these two process parameters induced an increase in the oil droplet number (Corte´s-Mun˜oz et al., 2009; Floury et al., 2000; Hebishy et al., 2017). Furthermore, for peculiar homogenization conditions (200 2 225 MPa), O/W model emulsions stabilized by whey proteins showed a remarkable stability against coalescence because of sufficiently small droplets without (or with limited) protein denaturation (Corte´s-Mun˜oz et al., 2009; Hebishy et al., 2017). Concerning the improvement of solubility and functionality of hydrophobic bioactive food ingredients, only few studies have investigated this point for submicron or nanoemulsions processed by dynamic high pressure. For instance, Benzaria et al. (2013) processed by dynamic high pressure (200 MPa, two passes) emulsions stabilized with whey proteins and loaded with retinyl-acetate and evaluated the cellular uptake of retinyl-acetate through TC7-cell monolayers over 24 h of exposure time. The behavior of nanosized fat droplets (135 nm) obtained by dynamic high pressure was compared to the one of micelles of retinyl-acetate prepared using Tween 80 as surfactant (B100 nm). Micelles of retinyl-acetate showed faster retinyl-acetate uptake and turnover of retinyl-acetate into retinol than observed for the nanosized droplets. Nevertheless, nanosized droplets stabilized with whey proteins displayed higher physical stability against coalescence than did retinyl-acetate micelles stabilized with Tween 80 (Benzaria et al., 2013). In fact, there is now a need for further studies to elucidate the real benefits of nanoemulsions processed by dynamic high pressure.

5.5

Dynamic high pressure processing as greener preservation processing

The potentialities of (U)HPH as an alternative technique to thermal pasteurization has been widely investigated for the last 15 years. A large number of studies have shown the efficacy of (U)HPH for the inactivation of most spoilage and pathogenic microorganisms (Dumay et al., 2013; Patrignani & Lanciotti, 2016; Zamora & Guamis, 2015). The mechanisms involved in microbial inactivation by high hydrostatic pressure (HHP) are not yet fully elucidated. However, the high pressure and high-velocity gradients that accompany turbulence, cavitation, and/or shock against the walls of the HP valve are believed to cause mechanical ruptures or at least alterations of the cell membrane, and thus a degree of microbial inactivation (Kleinig & Middelberg, 1998; Middelberg, 1995). The main critical parameters of microbial inactivation by HHP can be classified into three groups: (1) treatment conditions, (2) characteristics of microbial strains,

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and (3) composition of the medium. The main critical treatment conditions for microbial inactivation by HHP are the product inlet temperature, the temperature reached at the HP valve, the pressure, and the number of passes in the HP valve. These parameters are independent of each other except for the temperatures reached at the HP valve which are related to the homogenizing pressure and the product inlet temperature. When the homogenization pressure and/or the number of passes increase, microbial inactivation increases. For pressure levels of 100
200 MPa, multipasses homogenization is generally needed to sufficiently reduce the microbial load. It has also been demonstrated that for low pressure levels (100
200 MPa) and moderate temperature at the HP valve (60 C
65 C), microbial inactivation could mainly be explained by mechanical disruption, while for higher pressure or temperature levels, the thermal effect becomes predominant (Donsı`, Ferrari, Lenza, & Maresca, 2009; Picart et al., 2006; Thiebaud et al., 2003). Gram-negative bacteria are more sensitive to HHP than Gram-positive bacteria. Wuytack, Diels, and Michiels (2002) studied the inactivation by HHP of five strains of Gram-positive bacteria and six strains of Gram-negative bacteria introduced into PBS buffer (pH 7.0). After one pass to 300 MPa (Emulsifier Emulsiflex C5 Avestin, Ti 5 25 C), a reduction from four to six logarithmic cycles was obtained for all Gram-negative strains, but only from one to two logarithmic cycles for those of Gram-positive. Differences in wall composition, and in particular in peptidoglycan content, may be responsible for the different HHP sensitivities observed for Gram-positive and Gram-negative strains. Indeed, the peptidoglycan layers constitute the skeleton of the bacteria wall and give it its rigidity. The wall of the thicker Gram-positive strains is composed of about 40 layers of peptidoglycans compared to only one to five for Gram-negative strains. The resistance of yeast and fungi against HHP treatments is intermediate between Gram-negative and Gram-positive bacteria. The limited efficiency of HHP treatments observed for the inactivation of some strains, even at high pressure or recycling levels, could be due to the existence of a differential spectrum of cellular resistance within the same microbial population (Donsı` et al., 2009). Inactivation of bacterial spores by HHP is difficult to achieve in the same operating conditions than for vegetative cells. Feijoo, Hayes, Watson, and Martin (1997) only destroyed 53% or 68% of Bacillus licheniformis spores introduced into an ice cream mix after HHP treatment at 100 MPa (HP valve T 5 71 C) or 200 MPa (HP valve T 5 88 C), respectively. Homogenization at higher inlet temperatures and/or pressures can be used to reach very high temperatures in the HP valve for a very short time (few seconds, HTST treatment) resulting in higher spore inactivation rates close to those required for sterilization (Georget, Miller, Callanan, Heinz, & Mathys, 2014; Sevenich & Mathys, 2018). Georget, Miller, Aganovic, et al. (2014) observed a reduction of five or two logarithmic cycles for Bacillus subtilis or Geobacillus stearothermophilus spores in PBS after HHP treatment at 300
350 MPa (HP valve T . 145 C). Amador-Espejo, Herna´ndez-Herrero, Juan, and Trujillo (2014) also obtained high reduction rates (B5 log cycles) of different bacterial spores inoculated in milk after HHP treatments at 300 MPa (Tin 5 85 C and HP valve T 5 140 C).

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The physicochemical properties (fat content, pH, NaCl, viscosity, etc.) of the medium also play an important role in microbial inactivation by HHP. The various studies carried out on the influence of fat on microbial inactivation, particularly in milk, have produced contradictory results showing either a protective (Kheadr, Vachon, Paquin, & Fliss, 2002; Vachon, Kheadr, Giasson, Paquin, & Fliss, 2002) or unprotective effect (Brin˜ez, Roig-Saugue´s, Herna´ndez Herrero, & Guamis Lo´pez, 2006). Microbial inactivation is likely to increase as the pH of the medium decreases (from pH 7 to pH 4, for example). By influencing shear forces and/or cavitation, the viscosity of the medium could also have effects on microbial inactivation by HHP. For the same reasons, the concentration and physicochemical nature of the biopolymers present in the treated liquid should also be considered. Recently, Coccaro, Ferrari, and Donsı´ (2018) investigated the correlations between the inactivation of Lactococcus lactis occurring in the HP valve with the main fluid dynamic phenomena (turbulence, elongational and shear stresses, and cavitation). They observed that low viscosity and turbulence, together with the elongational stresses appear to be the controlling factors of cell break-up, whereas at higher viscosities, the shear stresses become increasingly important. The occurrence of cavitation is only slightly affected by viscosity, and mainly depends on the velocities reached in the homogenization valve (Coccaro et al., 2018). In parallel to microbial inactivation, (U)HPH treatment can modulate the activities of endogenous enzymes from animal, microbial, or plant resources (Aguilar, Critianini, & Sato, 2018; Dumay et al., 2012; Zamora & Guamis, 2015). Depending on process parameters and medium characteristics, (U)HPH can induce inactivation, stabilization, or activation of enzymes (Aguilar et al., 2018). However, (U)HPH treatments above 200 MPa combining to moderate inlet temperature (B40 C
50 C) have been reported to lower or to completely inactivate the activity of enzymes involved in milk spoilage such as lactoperoxidase, plasmin, alkaline phosphatase or lipase; or in plant-based beverages such as lipoxygenase in soymilk, pectin methylesterase (PME), and polyphenol oxidase in apple or citrus juices (Aguilar et al., 2018; Zamora & Guamis, 2015). Lacroix, Fliss, and Makhlouf (2005) obtained physically stable orange juice after HPH at 170 MPa while the PME activity was only reduced by 20%. These results were attributed to the reduced size of the substrate or modification to its structure after HPH, making it less available to react with the enzyme. Several studies have demonstrated that UHPH ( . 200 MPa) combined or not with mild temperatures allowed the microbial and physicochemical stabilization of different beverages with a better preservation of sensorial and nutritional qualities than conventional thermal treatments: milk (Pereda, Ferragut, Quevedo, Guamis, & Trujillo, 2007), soymilk (Cruz et al., 2007; Poliseli-Scopel, Hernandez-Herrero, Guamis, & Ferragut, 2012; Poliseli-Scopel, Hernandez-Herrero, Guamis, & Ferragut, 2014), almond milk (Ferragut et al., 2015), citrus, or apple juices (Donsı` et al., 2009; Suarez-Jacobo et al., 2012; Velazquez-Estrada, Hernandez-Herrero, Guamis-Lopez, & Roig-Sagues, 2012). It has also been demonstrated that antioxidant activity, vitamin C, L-ascorbic acid, phenolic components, carotenoids, and flavonoids in fruit juices or beverages

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were preserved after (U)HPH treatments (Suarez-Jacobo et al., 2011; VelazquezEstrada et al., 2012; Zamora & Guamis, 2015). Furthermore, increasing the number of passes at moderate pressure level could be an energy-saving strategy to stabilize juices. Maresca, Donsı´, and Ferrari (2011) observed that three homogenization passes, at 150 MPa and 25 C, were also effective for the stabilization of the endogenous microbial load of fresh Annurca apple juice. The treated apple juice showed a minimum shelf life of 28 days under refrigerated conditions, during which the natural qualities of the fresh juice were completely preserved. Very few studies concern the evaluation of the sustainability of UHPH process even though it can be noticed that this process can pasteurize liquid foods while preserving sensorial and nutritional qualities particularly by limiting the exposure to high temperature. The sustainable alternative of UHPH compared to classical processing was recently studied by Valsasina et al. (2017) in the case of sterile milk production. They compared the environmental impacts of UHPH technology to those of a conventional thermal treatment [ultra high-temperature treatment (UHTH) and homogenization [using life cycle assessment (LCA). At a pilot scale, a lower energy consumption was established for UHPH compared to UHTH with consequently a significantly lower carbon footprint for UHPH. Electricity production was evaluated as the main input in the LCA for UHPH as for UHTH. However, by introducing an energy recovery to the UHPH equipment, as already developed for UHTH, a significant improvement of the LCA of UHPH could be obtained. UHPH being available currently only at a pilot scale, the evaluation of LCA at industrial scale has to be carried out by upscaling approaches confirming the results obtained at pilot scale (Valsasina et al., 2017). The main drawback concerning the potentialities of UHPH to stabilize liquid foods at industrial scale concerns equipment development (pumping and intensifier and valve) that must ensure the current flow capacity of production lines. This is the main challenge of the equipment furnishers. Recently, Sevenich and Mathys (2018) listed the main benefits and limitations of (U)HPH for food sterilization. They pointed out that (U)HPH is a continuous process that could be easily implemented in existing production lines; it offers a two-in-one process combining two energy-consuming processes (sterilization and homogenization/disintegration), and it preserves the overall nutritional quality of products. In return, (U)HPH needs aseptic filling line after sterilization, nonpumpable, or viscous products cannot be processed, at an industrial scale, energy recovery needs to be applied to compete with UHT systems in terms of efficiency and environmental sustainability (Sevenich & Mathys, 2018).

5.6

Conclusion

The development of dynamic high pressure in the food sector is an ongoing process. This processing is recognized as green processing conforming to the consumer requirements for minimally processed foods. Dynamic high pressure has the

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advantage to achieve several eco-friendly applications based on the combination of physical, hydrodynamic, and thermal effects: extract bioactive compounds with a strong interest as food ingredients, process submicron, and nanoemulsions characterized by a high degree of stability, and also stabilize without thermal treatment liquid foods by inactivating microorganisms and/or enzymes. Another advantage is that dynamic high pressure at P $ 200 MPa is a two-in-one homogenization technology allowing a concomitant reduction of microbial load and of emulsion droplet size. However, the change of scale from laboratory to industrial scale equipment is one challenge for this processing even if some manufacturers propose at present time pilot plant homogenizers.

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639. Spiden, E. M., Yap, B. H. J., Hill, D. R. A., Kentish, S. E., Scales, P. J., & Martin, G. J. O. (2013). Quantitative evaluation of the ease of rupture of industrially promising microalgae by high pressure homogenization. Bioresource Technology, 140, 165
171. Suarez-Jacobo, A., Ru¨fer, C. E., Gervilla, R., Guamis, B., Roig-Sagues, A. X., & Saldo, J. (2011). Influence of ultra-high pressure homogenisation on antioxidant capacity, polyphenol and vitamin content of clear apple juice. Food Chemistry, 127, 447
454. Suarez-Jacobo, A., Saldo, J., Ru¨fer, C. E., Guamis, B., Roig-Sagues, A. X., & Gervilla, R. (2012). Aseptically packaged UHPH-treated apple juice: Safety and quality parameters during storage. Journal of Food Engineering, 109, 291
300. Tadros, T. F., Izquierdo, P., Esquena, J., & Solans, C. (2004). Formation and stability of nano-emulsions. Advances in Colloid and Interface Science, 108, 303
318. Tesch, S., & Schubert, H. (2002). Influence of increasing viscosity of the aqueous phase on the short-term stability of protein stabilized emulsions. Journal of Food Engineering, 52, 305
312. Thiebaud, M., Dumay, E., Picart, L., Guiraud, J. P., & Cheftel, J. C. (2003). High-pressure homogenization of raw bovine milk. Effects on fat globule size distribution and microbial inactivation. International Dairy Journal, 13, 427
439. Vachon, J. F., Kheadr, E. E., Giasson, J., Paquin, P., & Fliss, I. (2002). Inactivation of foodborne pathogens in milk using dynamic high pressure. Journal of Food Protection, 65, 345
352. Valsasina, L., Pizzol, M., Smetana, S., Georget, E., Mathys, A., & Heinz, V. (2017). Life cycle assessment of emerging technologies: The case of milk ultra-high pressure homogenisation. Journal of Cleaner Production, 142, 2209
2217. Velazquez-Estrada, R. M., Hernandez-Herrero, M. M., Guamis-Lopez, B., & Roig-Sagues, A. X. (2012). Impact of ultra high pressure homogenization on pectin methylesterase activity and microbial characteristics of orange juice: a comparative study against conventional heat pasteurization. Innovative Food Science & Emerging Technologies, 13, 100
106. Velazquez-Lucio, J., Rodriguez-Jasso, R. M., Colla, L. M., Saenz-Galindo, A., CervantesCisneros, D. E., Aguilar, C. N., . . . Ruiz, H. A. (2018). Microalgal biomass pretreatment for bioethanol production: A review. Biofuel Research Journal, 17, 780
791. Walstra, P., & Jenness, R. (1984). Milk fat globules. In P. Walstra, & R. Jeness (Eds.), Dairy chemistry and physics (pp. 254
278). New York: Wiley. Wuytack, E. Y., Diels, A. M. J., & Michiels, C. W. (2002). Bacterial inactivation by highpressure homogenisation and high hydrostatic pressure. International Journal of Food Microbiology, 77, 205
212. Yap, B. H. J., Dumsday, G. J., Scales, P. J., & Martin, G. J. O. (2015). Energy evaluation of algal cell disruption by high pressure homogenization. Bioresource Technology, 184, 280
285. Zamora, A., & Guamis, B. (2015). Opportunities for ultra-high-pressure homogenisation (UHPH) for food industry. Food Engineering Reviews, 7(2), 130
142.

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Ohmic heating for preservation, transformation, and extraction

6

Rui M. Rodrigues, Zlatina Genisheva, Cristina M.R. Rocha, Jose´ A. Teixeira, Anto´nio A. Vicente and Ricardo N. Pereira CEB
Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal

6.1

Introduction

Today ohmic heating (OH) technology finds a vast number of applications in food biotechnology and modern organic chemistry. Since its first application in 1800s, a growing body of technological and scientific evidences has been established widening up innovative applications regarding the thermal and nonthermal processings in food processes and bioprocesses. Why OH has been able to struggle over these years? Its ability to generate heat inside a given material brings several processing advantages, such as fast and uniform (volumetric) heating, increased energy efficiency ( . 90%), controllable heating rate, and to attain high temperatures in a very short time. There is also the possibility to in situ monitor heating process and electrical changes (such as electrical conductivity) due to the interaction of an electrical current within the medium. More recently, the nonthermal effects provided by the electrical variables—electric field (EF) and electric frequency—of this technology have been discussed, as well as novel and commercial applications. These aspects will be thoroughly discussed in the following sections.

6.1.1 Fundamentals of ohmic heating The passage of electric current through a semiconductive material results in motion of charged particles, either the electrons flow or ions and other charged molecules present on the matrix move between electrodes. This motion of charges and increase in kinetic and vibration energy result in generation of heat through a phenomenon described by the Joule’s law and known as Joule heating or OH. Fig. 6.1 illustrates the energy transference phenomena occurring during OH. OH will occur regardless of the current type (direct or alternating) or other parameters such as frequency and wave shape. However, these factors are demonstrated to influence heating rates, diffusion and chemical stability of the process (Ramaswamy, Marcotte, Sastry, & Abdelrahim, 2016; Yildiz & Guven, 2014). During OH the electrodes contact directly the product electrolysis and electrode erosion are major issues; thus alternating current is exclusively used in OH applications due to the polarity exchange and electrolytic reactions control. Increase in the Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00006-9 © 2019 Elsevier Inc. All rights reserved.

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Figure 6.1 Ohmic heating scheme and its energy transference phenomena occurring in liquid and solid phases.

electric frequency results in the reduction of the Faraday reactions, effectively eliminating them at values above 15
20 kHz. The increase in the EF strengths will result in the increase of conductivity and heating rates. The voltage gradients applied during OH usually are comprehended between 1 and 1000 V/cm, falling under the specifications of moderate electric fields (MEF). The differentiation between OH and MEF is merely a question of the predominant or intended effect, OH being a process where the main effects are thermal, whereas in MEF the prime or the desired effects arise from the presence of the EF. Despite this formal distinction, in practical applications, no strict differentiation between thermal and electric effects can be achieved, and both effects occur simultaneously. However, it is important to highlight that despite OH being a common technological or commercial term, the dissipation of heat is always a result of applying MEF through a conductive material. A fundamental factor concerning OH design and applications is electric conductivity, being the heating deposition rate directly proportional to the square of EF strength and electrical conductivity. The electric conductivity of a product is

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dependent on the composition, structure, and temperature and increasing (usually linearly) with the increasing temperature. In foodstuff and biological materials the conductivity range is usually between 0.1 and 10 S/m (Jaeger et al., 2016; Sakr & Liu, 2014). These values are sufficient for a successful application of OH, but electrical conductivity can be controlled by adjusting the water content or through the addition of salt and acids. When dealing with particulate products, some additional factors have to be taken into account. Differences in conductivity between the continuous phase and the particles have to be considered well as the particles size, shape orientation and concentration. These factors have been subjected to several studies, and their impact can be minimized through product adjustments (e.g., allow conductivity equilibration by diffusion or adjust conductivity in one of the phases) and by equipment’s design (Knirsch, dos Santos, de Oliveira Soares Vicente, & Penna, 2010). OH is a versatile process once it can be operated in batch or continuous mode, as well as several geometries of the heater and the electrodes can be adopted according to the process and product specifications. Equipment design and geometry considerations are particularly critical for the continuous process, where the occurrence of death zones or simply the different flow velocities on the surface and interior zones of the heater will result in nonuniform heating of the product. Usually these problems are overcome by applying heating sections in series or by increasing the turbulence of the flow either by controlling the flow speed and geometry or by including mixers on these sections. Several advantages can be attained from the application of OH when compared with other thermal processing techniques as the conventional plate-and-frame heat exchangers or other new techniques, such as microwave or radiofrequency heating. The main advantage of OH arises from the volumetric heating, as the heat is rapidly and uniformly generated on the product. Even electromagnetic heating technologies create limitations in heating the product uniformly in addition to the complex control, characterization, and versatility of the process. The low dependence of thermal diffusion also means that the process can operate under low shear, making the process suitable for shear sensitive products. Uniform heating eliminates problems frequent in heat exchangers where the product heating is dependent on the convection and conduction of heat through of hot surfaces that often lead to local overprocessing and the occurrence of fouling. In this sense, OH results not only in products with better quality as it allows longer operation periods but also in reduced cleaning and maintaining costs due to the reduced fouling. The heat deposition is dependent on the electric power supplied, implying high and easy control of the heating rate and the temperature reached. It also means few limitations on these parameters, allowing, for example, high temperatures and short heating (HTST principle) times, positively impacting the properties and quality of the product. The conversion of electric into thermal energy results in high energetic efficiencies (i.e., .90%) that are significantly higher than the ones obtained by traditional heating methodologies (Silva, Santos, & Silva, 2017). The use of electric energy also results in a cleaner (at least locally) and more sustainable process, once it is

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less dependent on fossil fuels, opposed to conventional heating that relies almost exclusively on the burning of fuels (Pereira & Vicente, 2010). Comparing with the electromagnetic heating technologies, there is no restriction on the electromagnetic signal applied, and their containment/isolation is simpler. OH equipment can be easily scaled by changing the power input and adding/removing modules in series. Yet there are still some drawbacks on the implementation of OH technology. Technically, its application is only restricted by the electrical conductivity of the products to be treated. Highly conductive products or containing highly conductive particles can impair heating control due to impracticable current densities. In some particular conditions, arching phenomena may take place, resulting in product deterioration and equipment damage (Sakr & Liu, 2014). On the contrary, low-conductive products, such as the ones containing low amounts of water and/or electrolytes and fat-based or containing large fat globules, may impair the passage of electric current and thus OH effect takes place. Economic reasons stand as the major impairment for the dissemination of the technology. For low-scale production the costs of OH equipment can be relatively high when compared to the conventional alternatives. However, these costs tend to decline as technology spreads out, with improvement in the production techniques as well as the development of new equipment and technological components, particularly energy sources. Although electricity is more expensive than fossil fuels, the trend is to be reversed rapidly for this situation in the light of increased environmental awareness. In addition the increased energetic efficiency, reduction/elimination of boilers, water use, wastewater disposal, and lower maintenance costs can contribute to reduce significantly the overall process costs. The technological and economic viability of process should be made case-by-case depending on the type of food product and processing objectives through studies performed at pilot or semiindustrial scale. Other impairment to the application of OH can rely on the reluctance of food companies to adopt new technologies mainly due to the lack of knowledge or simply by the nuisance to replace well-established and traditional processes.

6.1.2 Present status: commercial and novel applications The working principles of OH in food processing have been exploited more than a century ago (Ramaswamy et al., 2016). However, the lack of fundamental knowledge and proper technology impaired the development and implementation of the technology. Over the last few decades, OH reemerged and now is seen as one of the “emerging high-potential technologies for tomorrow” (De Vries et al., 2018). To get here, much has been contributed to the level of technological advances in power supply technology (e.g., allowing higher power capacity and the use of high frequencies that eliminate the electrolytic problems), as well as applied and fundamental research. Continuous OH demonstrated to be an effective method to process food products at HTST conditions. The process is suitable for high viscous products and particulates, as well as solid liquid mixtures, such as fruits and derivatives, vegetables,

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dairy products, egg products, algae, syrups, sauces, and ready-to-eat dishes. Its implementation on the existing aseptic lines is straightforward and manufacturers, such as Alfa Laval, Raztek, Emmepiemme, INDAG IPS, APV Baker, or Yanagiya, produce OH equipment at industrial scale (see Table 6.1). Most of these industrial applications aim at the pasteurization or the sterilization of products; however, other successful applications have been developed. Yanagiya’s tofu production equipment uses OH to induce soymilk coagulation. The company produces several units from the tabletop to large industrial scale. Batch operation, despite the low incidence, has been the focus of some applications. The development of food containers with the integration of an OH device aiming to space missions has been tested (Jun & Sastry, 2005). Therefore the industrial implementation of OH in the food processing sector is steadily growing since the 1990s. As a result of this, several products processed by OH are now on the market worldwide (see Table 6.2). OH also has several niche applications in another areas of knowledge, such as chemical and biological engineering. The potential of OH has been identified and applied to disinfect sludge, where the fast, homogeneous, and efficient heating demonstrated advantages on the process (Murphy, Powell, & Morrow, 1991; Table 6.1 Ohmic heating equipment manufacturers, product specifications, and potential applications. Supplier

Power (kW)

Operational parameters

Applications

Alfa Laval

60
300

400 V; 20 kHz

Fruits and derivatives, vegetables, prepared foods, cheese, liquid eggs, ready-to-eat dishes, sauces, and juices

Raztek

NA

Emmepiemme

30
600

4
12 kV; 50 Hz 25 kHz

INDAG High Power Heating System (IPS) APV Baker

NA

NA

75
300

50 Hz

Yanagiya Kasag

NA NA

NA NA

Fruits and derivatives, vegetables, dairy products, egg products, algae, syrups, sauces, and ready-to-eat dishes Liquid products including chunks and highly viscous foodstuffs Fruit preparations and dressings with high fruit content (also sterile, for pH-neutral products) Tofu production Caramel, vanilla, or chocolate sauces; convenience food with vegetables and meat; soups; ketchup; salsa sauces; and all foodstuffs which can be pumped

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Table 6.2 Examples of available commercial food products processed by ohmic heating. Company

Brand

Product

Country

National Egg Inc. Walmart Sicoly Campbells

GoldEgg/Jaune Dore´ Great value Sicoly Liebig

Liquid egg and egg whites Liquid egg and egg whites Processed fruits Vegetable side dishes

Canada United States France France

Yin, Hoffmann, & Jiang, 2018). Applied to the wastewater from surimi production, the coagulation of proteins by OH facilitates protein removal and thus reducing the biological oxygen demand (Kanjanapongkul, Tia, Wongsa-Ngasri, & Yoovidhya, 2009). On a modeling study, OH showed potential to increase the heating rates in polymer electrolyte fuel cells, thus reducing significantly their start-up time (Singdeo, Dey, & Ghosh, 2011). A new area of interest for OH is the organic synthesis. OH allowed faster and more uniform heating and induced increase in the dynamics/mobility of charged species resulting in higher reaction yields and shorter reaction times than external heating (oil bath) and microwave heating (Pinto et al., 2013). Several examples of OH application in this area resulted in advantages, such as increased yields, selectivity, the use of less catalyst and its reutilization, and cleaner reaction mixtures (Do Cardoso et al., 2015; Pinto, Vera, Silva, Santos, & Silva, 2015). Along with these advantages and higher levels of energetic and operation efficiencies in waterbased systems, OH brings environmental and economic benefit, thus opening interesting perspectives on its use as a tool in organic synthesis applications (Silva et al., 2017).

6.2

Food processing and preservation

6.2.1 Thermal processing of foods The thermal processing of foods has as its main objectives the reduction or elimination of enzymatic and microbial activities and the change or promotion of certain organoleptic and nutritional properties in foods. To fulfill these specific objectives, several thermal processing operating units are industrially established and classified as blanching, pasteurization, sterilization, and cooking, among others. OH is a versatile thermal processing method, so it is possible to implement and attain advantages in a large range of operations and applications. The use of OH as a blanching method brings several advantages to the process and positively impact the quality of the products. Typical blanching involves the immersion of fresh products in hot water or their contact with steam for a determined period of time. These processes are limited by diffusional problems, so large volumes of water or steam are required for the necessary energy transfer to take place. In addition the time required to the whole foodstuff to reach the needed

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temperature can impose process limitations and cause overcooking on the external surface of a food, leading to nutritional and organoleptic deterioration (Richter Reis, 2016). To minimize these problems, particle size reduction is used, but this solution involves additional preparations and also results in organoleptic changes on the products. Once OH can achieve extremely fast heating rates and generate heat directly inside the food products, the diffusional problems are reduced, as it is the time required to perform the blanching. The use of OH only requires a continuous phase on the interstitial space between the food particles and the electrodes (Sensoy & Sastry, 2004a,b), thus only a fraction of fluid is needed when compared to the conventional methods. All this result in a faster, more effective, and energyefficient process. The application of OH on blanching is well reported in literature, and its advantages are clear. The blanching of pea pure was performed through OH and water bath (Icier, Yildiz, & Baysal, 2006). By using voltage gradients of 30 V/cm and above, peroxidase inactivation was faster than by water bath, resulting in a faster blanching and an increased color quality of the final product. OH blanching is applied to pumpkin under the same thermal conditions as a conventional blanching, allowing to reduce the necessary time to achieve an adequate enzyme inactivation while maintaining the food color (Gomes, Sarkis, & Marczak, 2018). On the blanching of artichoke heads, Guida et al. (2013) reported enzymatic inactivation in shorter times compared with the conventional blanching. Furthermore, they reported less color, textural and nutritional loss on the ohmic-treated samples. On another study of artichoke products, OH blanching, performed at 85 C, presented an identical inactivation as conventional at 100 C, thus retaining higher amounts of vitamin C and phenolic compounds (Icier, 2010). OH presents a great alternative to conventional heat exchange pasteurization and sterilization methods due to its fast and homogeneous heating, resulting in advantages as fouling reduction and maintenance of nutritional and organoleptic properties (Cappato et al., 2017; Knirsch et al., 2010). In fact, pasteurization was the first and still predominant commercial application of OH technology (Schler, Tikvah, & Lipshtat, 2002; Varghese, Pandey, Radhakrishna, & Bawa, 2012). The best reported example of OH concerns to the pasteurization of dairy and egg products (Jaeger et al., 2016; Ramaswamy et al., 2016; Yildiz & Guven, 2014). On these particular cases, protein denaturation is one of the major issues causing fouling and product deterioration (Cappato et al., 2017; Icier & Bozkurt, 2011). In the processing of these kind of products, OH particularly contributes to the absence of hot surfaces, reduced diffusional problems and processing time, ensuing operational advantages as well as similar or improved product quality (Icier & Bozkurt, 2011; Pereira, Martins, & Vicente, 2008; Roux et al., 2016; Sun et al., 2008). OH technology can also bring processing advantages to other sensitive foods as infant formulas and baby food. The application of OH on the ultrahigh temperature processing of infant formula presented promising results regarding color retention and vitamin C degradation when compared with steam injection technique, (Roux et al., 2016). On another study involving the sterilization of baby food has shown that OH affects less the nutritional quality of the product, contrary to the

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conventional method (Mesı´as, Wagner, George, & Morales, 2016). The application of OH also demonstrated to reduce the formation of harmful compounds as furan (i.e., 70%
90% reduction) and other compounds resultant from fatty acids oxidation and Maillard reaction in vegetable- and meat-based baby food (Hradecky, Kludska, Belkova, Wagner, & Hajslova, 2017). Juice processing is another successful example of OH implementation (Ramaswamy et al., 2016). OH proved to preserve carotenoid profile during the pasteurization of citrus juices (Achir et al., 2016), improved sensory profile, comparable to fresh juice, as well as an increase in the shelf life of orange juice (Leizerson & Shimoni, 2005a,b). Applied to high viscous foods as pepper paste, continuous OH demonstrated to achieve similar microbial reduction in shorter processing time and to obtain a higher consistency index, when compared to the conventional heating method (Cho et al., 2017). Other food processing operations have exploited the advantages of OH on their process parameters. Tomato pealing was successfully tested through OH, resulting not only in a successful pealing in a shorter period but also reducing the use of chemicals and residues production (Wongsa-Ngasri & Sastry, 2015). The production of tomato paste using OH has also shown a promising application. It was found that the increasing voltage results in a shorter time to the water content reduction while improving values of color criteria, pH, and energy consumption (Torkian Boldaji, Borghei, Beheshti, & Hosseini, 2015). Meat processing is another example of successful OH application. The cooking of hamburger patties by a combination of OH and plate heating was reduced by half while maintaining the intended quality para¨ zkan, Ho, & Farid, 2004). On the precooking of meatballs a successful meters (O reduction of contaminant microorganisms and higher cooking yields was accomplished by OH (Sengun, Turp, Icier, Kendirci, & Kor, 2014). Cooking meatballs with OH resulted significantly in firmer and more even in microstructure, as well as brighter color and lower moisture contents than their conventionally cooked equivalents (Engchuan, Jittanit, & Garnjanagoonchorn, 2014). Whole meats, such as turkey, beef muscle, or shrimp, were cooked using OH where its potential to yield a higher quality product and reduce cooking time was demonstrated (Lascorz, Torella, Lyng, & Arroyo, 2016; Zell, James, Cronin, & Morgan, 2010a,b). The OH prospective in thawing meat and fish products has been also established, ¨ mit, 2015; Liu resulting in lower thawing times and lower weight loss (Duygu & U et al., 2017). Other examples, such as rice cooking and bread baking, were successfully tested using OH technology, demonstrating the operational flexibility and potential of this technology (Gally, Rouaud, Jury, & Le-Bail, 2016; Kanjanapongkul, 2017).

6.2.2 Nonthermal effects: cellular matrices, microorganisms, and enzymes Together with the technical and operational advantages of OH compared to other thermal methods as heat exchange, the nonthermal effects inherent to the

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167

application of an external EF play an important role. Table 6.3 shows examples of the nonthermal effects of OH regarding microbiological inactivation, protein functionalization, among others. The electropermeabilization of cells resultant from the exposure to an EF is a well-reported effect (Mahniˇc-Kalamiza, Vorobiev, & Miklavˇciˇc, 2014; Pucihar, Kotnik, & Miklavˇciˇc, 2009) and has been recognized on OH research and industrial applications. This is certainly advantageous on several processes as pasteurization where the conjugation of electrical and thermal effects results in increased inactivation kinetics (Park & Kang, 2013; Sastry, 2008). In the context of pasteurization the predominant effect of OH is thermal by nature, but the presence of nonthermal effects can result in a less processing time or lower temperatures required to ensure intended inactivation levels, thus supporting even more the processing advantages reported in the earlier section. Several works report the additional effect of electropermeabilization during OH, generally resulting in increased inactivation effects. Park and Kang (2013) reported some additional bacterial inactivations (i.e., Escherichia coli, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes) between 55 C and 60 C. It was also found that the additional electrical effect is dependent on factors, such as frequency and electrical conductivity of the product (Kim, Choi, & Kang, 2017; Lee, Ryu, & Kang, 2013). Particularly interesting is the results of the application of OH on the inactivation of spores where higher lethality is systematically observed (Baysal & Icier, 2010; Somavat, Hussein, Chung, Yousef, & Sastry, 2012; Somavat, Hussein, & Sastry, 2013). Nonthermal effects in spore lethality were also found to be dependent on parameters, such as voltage (i.e., EF applied) and electric frequency. Overall, the inactivation effects under OH have been evaluated in several matrices as fluid, viscus, and particulate foods, presenting increased inactivation of broad-spectrum organisms (i.e., bacteria, spores, yeast, and phage) (Baysal & Icier, 2010; Kim et al., 2017; Lee et al., 2013; Pereira, Martins, Mateus, Teixeira, & Vicente, 2007; Sun et al., 2008; Yoon, Lee, Kim, & Lee, 2002). The electropermeabilization during OH is considered to be mild, and its inactivation effects are mostly dependent on the synergy with thermal effects. But these nonthermal effects can be effective by themselves. By using EF up to 280 V/cm, Machado, Pereira, Martins, Teixeira, and Vicente (2010) have demonstrated the success of MEF to inactivate E. coli at room temperature. OH has proved to influence the growth and metabolic activities of microorganisms when heat generation is kept at sublethal levels and the EF strength was relatively low. The effect of MEF in Lactobacillus acidophilus demonstrates to be mostly significant during the lag period, which decreased up to 94%, and shown to be dependent on electric frequency and harmonics (Cho, Yousef, & Sastry, 1996; Loghavi, Sastry, & Yousef, 2008, 2009). These results confirm the permeabilization effect of MEF and prove that they can occur in living and viable cells. The use of electrostimulation was also tested in yeast cells. The application of MEF in recombinant Saccharomyces cerevisiae significantly reduced the lag phase duration and increased biomass yield. However, the increase in EF intensity

Table 6.3 Nonthermal effects if ohmic heating (OH) in several applications. Product

Conditions

Effects

References

Inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in buffered peptone water and apple juice E. coli ATCC 25922 in buffer solution

55 C
60 C 30 and 60 V/cm 20 kHz sine wavea

Electroporation caused cell damage resulting in additional bacterial inactivation at sublethal temperatures

Park and Kang (2013)

Changes at the cell membrane and inactivation Inactivation of bacteria and phage increased with the reduction of frequency

Machado et al. (2010)

Geobacillus stearothermophilus spores

121 C, 125 C, and 130 C 60 and 10 kHza

Bacillus coagulans spores in tomato juice

95 C, 100 C, 105 C, and 110 C 13 V/cm 60 and 10 kHza 60 C
80 C 25
40 V/cm 60 Hza

Inactivation increased with increased frequency No dependence of waveform Higher lethality for spores treated with OH EF strength affects inactivation at lower temperatures Accelerated spores inactivation. 10 kHz presented higher efficacy the 60 Hz at 121 C Accelerated inactivation spores

Lee et al. (2013)

Alicyclobacillus acidoterrestris spores in orange juice

, 25 C 50
280 V/cm 50 Hz 47.7 V/cm 0.06, 0.2, 0.5, and 1 kHz 70 C and 80 C for buffered peptone water and tomato juice, respectively 90 C 12.5 V/cm 60
20,000 Hz sine, square, and sawtooth waveform 70, 80, and 90 C 30
50 V/cm 50 Hza

Enlarged periplasmic space and uneven cell wall induced by OH Increased inactivation dependent on electric field strength Better color and vitamin C retention OH shortened the decimal reduction time

Lee, Sagong, Ryu, and Kang (2012)

Enhancement of exuded intracellular material with OH Increased EF strength and frequency resulted in increased effects

Yoon et al. (2002)

Pathogens and MS-2 phage in buffered peptone water and tomato juice

Inactivation

E. coli O157:H7 and S. enterica serovar Typhimurium in salsa

E. coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in orange juice and tomato juice

E. coli in goat milk and Bacillus licheniformis in cloudberry jam Saccharomyces cerevisiae in phosphate buffer

55
80 C 20
54 V/cm 50 Hza 20
100 C 10, 15, and 20 V/cm 60 Hz, 600 Hz, 6 kHz, and 60 kHza

Kim et al. (2017)

Baysal and Icier (2010)

Somavat et al. (2012)

Somavat et al. (2013)

Pereira et al. (2007)

(Continued)

Stimulation

Table 6.3 (Continued) Product

Conditions

Effects

References

Lactobacillus acidophilus in fermentation broth

30 C, 35 C, and 40 C 15 and 40 V/cm 60 Hza

Cho et al. (1996)

L. acidophilus in fermentation broth

30 C and 37 C 1 V/cm 54, 60, and 90 Hza

L. acidophilus in fermentation broth

30 C 2 V/cm 45, 60, 1000, 10,000 Hza 30 C 0.5
2 V/cm 50 Hza

Lag period decreased by 94%. OH did not change the generation time, decrease in maximum growth Shorter lag phase No lag phase reduction was found for highfrequency harmonics Higher permeabilization at lower frequencies

Lag phase reduction Increased biomass yield

Castro et al. (2012)

Enhancement permeabilization at a moderate temperature. Increase of the EF treatment time resulted in an increase damage degree Induced permeabilization related with temperature-induced changes in the cell membrane structure Increased leaching of solute from fresh cellular material and no changes previously dried cellular materials. Chloroplast compression in fresh leaves cells Accelerated the mass transfer in the apple samples Diffusion increases, cell wall damage induced by OH Improved mass transfer and lower losses of phenolic components Enhancement of water and sugar transfer

Lebovka et al. (2008)

Improved mass transfer

Moreno et al. (2012)

Permeabilization of vegetable cells

S. cerevisiae in fermentation broth Potato tissues

50 C 30
80 V/cm 50 Hza

Potato and apple tissues

22 C
50 C 40
100 V/cm 50 Hz

Black tea and mint leaves

70 C and 80 C 0
125 V/cm 50, 500, and 5000 Hza

Apple in 65% (w/w) sucrose

30 C, 40 C, and 50 C 13 V/cm 60 Hza 40 C 0
17 V/cm 60 Hza 30 C, 40 C, and 50 C 13 V/cm 60 Hza 65 C and 80 C 35 V/cm 50 Hz 30 C 9.2, 13, and 17 V/cm 60 Hz

Apple in 45%
65% (w/w) sucrose Blueberries in 65% (w/w) sucrose Strawberries is sucrose solutions Strawberries in 65% (w/w) sucrose

Loghavi et al. (2008)

Loghavi et al. (2009)

Lebovka and Praporscic (2005)

Sensoy and Sastry (2004a,b)

Moreno et al. (2011) Simpson et al. (2015) Moreno et al. (2013) Allali et al. (2010)

(Continued)

Table 6.3 (Continued) Product

Conditions

Effects

References

Polyphenoloxidase, lipoxygenase, pectinase, alkaline phosphatase, and β-galactosidase Polyphenoloxidase in grape juice

60 C
78 C 20
90 V/cm 50 Hza

Increased inactivation in polyphenoloxidase and lipoxygenase

Castro et al. (2004)

60 C, 70 C, 80 C, or 90 C 20
40 V/cm 50 Hz 50 C
80 C 50 Hz Variable voltagea

Critical deactivation temperature decreased with EF increase Change in kinetic parameters, no change in inactivation mechanisms Peroxidase is more susceptible to EF effect Inhibition of enzyme activity in a shorter processing time Peroxidase increased activity at 60 C and enhanced inactivation 80 C Enzyme activity is field strength and temperature dependent (lower temperatures activation occurs while at higher temperatures inactivation is induced). The EF inactivation increases with increasing field strength Pectin methylesterase activity is influenced by EF at frequencies up to 60 Hz Enhanced activity between 1 and 60 Hz and slight inhibition at higher frequencies

Icier et al. (2008)

Enzyme activity

Alkaline phosphatase, pectin methylesterase, and peroxidase in milk and fruit and vegetable juices

Polyphenol oxidase in sugarcane juice Peroxidase and polyphenol oxidase in sugarcane juice

80 C 24, 32, and 48 V/cm 50 Hza 60 C, 70 C, 75 C, and 80 C 3.57
4.39 V/cma

Pectin methylesterase in tomato homogenate

65 C
95 C 5, 8, and 10.5 V/cm 60 Hza

Pectin methylesterase and polygalacturonase in tomato homogenate α-Amylase

65 C 0.4 V/cm 0
1 MHza 60 C 1 V/cm 1 Hz
1 MHza

Jako´b et al. (2010)

Saxena et al. (2016)

Brochier and Domeneghini (2016) Samaranayake and Sastry (2016a)

Samaranayake and Sastry (2016b)

Samaranayake and Sastry (2018)

(Continued)

Table 6.3 (Continued)

Functionality change

Product

Conditions 

Surimi

Up to 90 C 13.3 V/cm 60 Hza

Salmon plasma protein on Pacific whiting surimi Surimi

60 C
90 C 12.62 V/cm 10 kHza 75 C
90 C 6.7 and 16.7 V/cm 10 kHza

WPI dispersion

90 C 4
22 V/cm 50 Hza

Aggregation and gelation of WPI dispersion

85 C 4
22 V/cm 25 kHza

Aggregation of WPI dispersion

90 C 6 and 12 V/cm 25 kHza

Pretreatment of WPI dispersion for cold gelation mediated by Fe21

90 C 0
10 V/cm 25 kHz

WPI dispersion for protein film formation

85 C 10 V/cm 50 Hza

Effects

References

Lower proteolytic activity and lower free sulfhydryl concentration. Improved shear stress and hear strain resultant form continuous gel structure Increase gel strength

Yongsawatdigul et al. (1995)

Minimized proteolysis, lower total sulfhydryl concentration, and increased water retention Changes in thermodynamic and kinetic parameter of whey protein denaturation Lower aggregation and aggregate size, reduction of free sulfhydryl groups, formation of gels with distinctive mechanical properties and microstructure Lower aggregation and aggregate size, reduction of free sulfhydryl groups, and change in aggregates shape Changes in particle size distribution, physical stability, rheological behavior, and microstructure of the gels Protein conformational changes, lower aggregation and concentration of free sulfhydryls. Films were thinner, less permeable to water vapor and presented the same mechanical properties of conventional films

Tadpitchayangkoon et al. (2012)

Fowler and Park (2015)

Pereira et al. (2011)

Rodrigues et al. (2015)

Pereira et al. (2016a)

Pereira et al. (2017)

Pereira et al. (2010)

(Continued)

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Table 6.3 (Continued) Product

Conditions 

Chitosan film formation solutions

60 C 50
200 V/cm 50 Hza

Chitosan film formation solutions

60 C 100 and 200 V/cm 50 Hza

Starch and chitosan film formation solutions

70 C 7.6 V/cm 25 kHza

Protein
lipid film formation from soymilk

85 C Variable voltage 50 Hza

Effects

References

Increased field strength positively influenced water vapor, oxygen and carbon dioxide permeability. Also more uniform film surface is induced Higher crystallinity, more uniform surface, and increase of the tensile strength and elongation at break of the films Decreased permeability to water vapor in chitosan-based films and more hydrophobic surface Increased hydrophilic in starch films with lower tensile strength and Young’s modulus Higher yield, film formation rate, and protein incorporation

Souza et al. (2009)

Souza et al. (2010)

Coelho et al. (2017)

Lei et al. (2007)

a

Conventional heating control.

resulted in plasmid instability causing the reduction of β-galactosidase production (Castro, Oliveira, Domingues, Teixeira, & Vicente, 2012). Vegetable cells are bigger as they have weaker cell walls than bacteria and spores, making them more susceptible to the electropermeabilization. In this sense the electroporation mechanism of tissue damage by MEF and particularly during OH are well described. These effects have been studied in a variety of foodstuffs and also dissociated from thermal effects, but their conjugation with moderate temperatures potentiates their efficiency (Lebovka, Kupchik, Sereda, & Vorobiev, 2008; Lebovka & Praporscic, 2005). A successful application of the thermoelectric permeabilization can also be found in field of osmotic dehydration. The application OH can result in the increase of the diffusion of sucrose into apple samples by inducing changes on the cell wall, thus reducing the dehydration time (Moreno et al., 2011; Simpson et al., 2015). OH is advantageous on assisting osmotic dehydration and vacuum impregnation processes, resulting also in higher enzyme inactivation, microbial stability, and physical properties of apple (Moreno et al., 2013). Similar results were obtained by the application of OH in strawberries, where increase in water and sugar flux is observed as well as better physical properties (Allali, Marchal, & Vorobiev, 2010; Moreno et al., 2012). On the application to

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blueberries, mass transfer was improved, and the drying time reduced contributing to lower losses of phenolic components (Moreno et al., 2016). The influence of OH on food enzymes has also been subjected to several studies, on their majority dealing with inactivation kinetics, where aforementioned thermal and electric effects of OH are also pointed out. Overall, the kinetic parameters show an enhanced inactivation of enzymes when subjected to OH, but the inactivation mechanisms remained the same (Castro, Macedo, Teixeira, & Vicente, 2004; Icier, Yildiz, & Baysal, 2008; Jako´b et al., 2010; Saxena, Makroo, & Srivastava, 2016). Recent studies point toward a more complex effect of the EF and electrical frequency on enzyme activity. It verified an increased peroxidase inactivation rate at 80 C, contrasting to 60 C where the activity was increased (Brochier & Domeneghini, 2016). At intermediate temperatures, no effects were noticed, which suggests specific actions of the EF for different temperatures. When pectin methylesterase activity in tomatoes was studied under OH form 5 to 10.5 V/cm, similar effects were found—that is, enzyme activation was promoted at lower temperatures, while accelerated inactivation was observed at higher ones, being the effects greater at higher EFs (Samaranayake & Sastry, 2016a). In addition, while applying a residual voltage, the effects of electric frequency in pectin methylesterase were found to be frequency dependent, being significant at low frequencies (,60 Hz) but negligible for higher ones (100 Hz
1 MHz) (Samaranayake & Sastry, 2016b). On further studies the α-amylase activities were determined in situ with the application of a low EF (1 V/cm, 1 Hz
1 MHz) at 60 C and compared with a conventional control treatment. It was demonstrated that significant nonthermal effects were dependent on the frequency. For low frequencies (1
60 Hz), activity enhancement up to 41% was achieved, while for higher frequencies, the effect was negligible or resulted in slight inhibition (Samaranayake & Sastry, 2018). The presence of nonthermal effects associated with OH, as thermal and electropermeabilization can enhance microbiological inactivation and influence enzymatic activity, thus presenting interesting advantages on several processes. Furthermore, the possibility of tune these effects brings up exciting possibilities to control and model the behavior of cells and foodstuff, opening new perspectives of application in food biotechnology.

6.2.3 Transformation of macromolecules As a result of the unique operational advantages (e.g., fast and homogeneous heating and fine temperature control), the potential of OH on the transformation and functionalization of food ingredients has been addressed. For the last decades the influence of OH has been addressed on products, such as dairy, soy, and fish proteins, as well as in several isolates or purified macromolecules. The application of OH on the gelation of surimi has maximized the gel functionality due to its fast and homogeneous heating (Yongsawatdigul, Park, Kolbe, Abu Dagga, & Morrissey, 1995). OH also leads to lower proteolytic activity and lower free sulfhydryl concentration, resulting in the formation of stronger gels than water bath heating. OH parameters, such as EF strength and heating rate, also

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influences the microstructural and mechanical properties of surimi gels (Fowler & Park, 2015; Tadpitchayangkoon, Jae, & Yongsawatdigul, 2012). A significant work has been developed on the denaturation and functional properties of whey proteins. It was demonstrated that OH influences the denaturation and aggregation pathways of whey protein isolate (WPI) solutions (Pereira, Teixeira, & Antonio, 2011; Rodrigues et al., 2015). OH and its EF contribute to lower denaturation levels and to decrease the concentration of free sulfhydryl in whey protein domains, as well as to reduce the size of protein aggregates. These factors have resulted in the formation of a weaker gel with a more uniform microstructure. In the preparation of WPI aggregates at pH 3 the reduction in aggregates’ size and free sulfhydryl was equally verified, and the morphology of the aggregated proteins changed toward to a fibrillar shape under EF effects. These changes were also found to be potentiated by the increased EF strength and heating rate (Pereira, Rodrigues, Ramos, et al., 2016a). The effect of adjusting the EF strength during OH in the preparation of cold-set gels mediated by iron addition leads to gels with distinctive microstructural and physical properties (Pereira et al., 2017). The consistency index was inversely proportional to EF intensity, while shear thickening behavior was observed when EF intensity was increased. Furthermore OH resulted in a more uniform and compact fine-stranded microstructure of the gels. The influence of OH on the unfolding and aggregation mechanisms of whey proteins, during heat denaturation, was studied on the formation of protein films (Pereira, Bartolomeu, Cerqueira, Teixeira, & Vicente, 2010). In this case, OH caused conformational changes in the proteins rearrangements during denaturation leading to less protein aggregation, which in turn resulted in thinner films with lower permeability to water vapor and similar mechanical properties to the controls. The application of OH in the production of polysaccharide films was assessed on a few works. The treatment of chitosan film formation solutions through OH at increasing EF strengths resulted in the increase of gas barriers properties. Also, the microstructure of the films presents higher order with the increase in EF (Souza et al., 2009). X-ray diffraction and SEM unveiled that chitosan films treated with OH also had higher crystallinity on the structure and uniform surface, resulting in well-improved mechanical properties (Souza et al., 2010). The OH treatment of starch and chitosan film forming solutions reinforced with microcrystalline cellulose has also influenced properties, such as hydrophobicity, gas permeability, and mechanical strength of the produced films (Coelho et al., 2017). The production of protein
lipid films from soybean milk using OH has resulted in differentiated physical properties of the films influencing their formation. The yield, film formation rate, and protein incorporation were higher under OH, also resulting in higher rehydration capacity (Lei, Zhi, Xiujin, Takasuke, & Zaigui, 2007). Overall, the use of OH has revealed the potential to influence the properties of macromolecules and to impact their functionality. The possibility of control parameters, such as heating rate, EF strength, or electric frequency, leads to the prospect of using OH as a tool to enhance and develop new functionalities in food and biotechnology.

Ohmic heating for preservation, transformation, and extraction

6.3

175

Extraction of biocompounds

Solid
liquid extraction processes have been widely applied to different food matrices. Traditional applications include vegetable oils, sugars, fruit extracts or infusions, but a wide variety of different aims can be found, which targets to concentrate bioactive fractions (usually extracts rich in antioxidants, such as phenolic compounds or carotenoids, where a wide variety of bioactive properties can be found), to extract an undesired compound (e.g., caffeine from coffee), or to get improved technological properties, such as coloring, flavoring, or texturizing extracts. These processes usually involve the use of high amounts of solvents (not always environmental friendly) as well as heat and stirring, which can be high energy demanding. Concerns with processes sustainability have driven the search for new and greener extraction processes (Chemat, Vian, & Cravotto, 2012). These processes were first aimed at the analytical scale (Armenta, Garrigues, & de la Guardia, 2015), but the concept of green chemistry was further extended to larger scales by several groups, including the American Chemical Society that launched the Design Principles for Sustainable & Green Chemistry & Engineering, focused on three main pillars: (1) resource efficiency, (2) minimal/zero hazards and pollution, and (3) holistically system design (using life cycle thinking). In this context, different approaches are available to meet the green(er) and sustainable extraction challenges, mainly focusing on raw materials, reducing energy, time, and solvents consumption, and using alternative solvents, while improving overall extraction efficiency (yield and selectivity), thus ensuring a safe and high-quality extract (Ameer, Shahbaz, & Kwon, 2017; Chemat et al., 2012). OH is an obvious possibility when considering extraction sustainable processes, as referred in Section 6.1, it allows almost instantaneous and uniform heating, thus reducing processing times while preserving nutritional, functional, and structural properties of the extracts; it also allows heating at comparable rates both phases in solid/liquid mixtures (provided that solid and liquid have similar electrical conductivities), avoiding local hot spots and excessive degradation; energy conversion efficiency is improved when comparing to traditional heating systems; in addition, a cell permeabilization effect is expected, thus boosting extraction yield (Pereira & Vicente, 2010; Rocha et al., 2018). Furthermore, aiming at the utmost reduced solvent usage or zero solvent, it can be also considered a pretreatment prior to extrusion or pressed-assisted extraction processes. Two main drivers are present in OH extraction processes: (1) thermal effects, allowing tissue softening, while increasing solutes solubility and mass transfer coefficients; (2) electropermeation effects, associated with matrix reorientation and cell membrane damage (both reversible or irreversible), facilitating solutes release from the food matrix and diffusion/leaching toward the solvent. Electrical conductivity is the most important property to be controlled in order to allow effective electric heating and permeation effects of the solid/liquid mixture, though the frequency of alternating current may be an important player in permeation effects

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(Aamir & Jittanit, 2017). The cell membrane structure will be determinant in the matrix sensitivity to the electropermeation effect. For instance, it has been described that apple tissues present higher plant tissue damage than potato tissues when submitted to OH at MEF (,100 V/cm), probably due to the differences in tissue structure, cell size, and air cavities (Lebovka & Praporscic, 2005). Albeit the mentioned benefits, this methodology may have limitations. For instance, the application of EFs can cause secondary phenomena such as electrochemical reactions (Pataro et al., 2014) that may be beneficial or harmful (e.g., induce degradation) to the extraction of a given biocompound. Another limitation is that, as the electric behavior of the biocompounds can differ dramatically, like in some cases, the electric effect may stabilize the target compound inside the matrix, hampering its extraction. It is thus important to obtain a fundamental understanding of the impact of MEF on the biocompounds to be extracted. Though some work has been made, particularly for proteins (Pereira et al., 2016a; Pereira et al., 2011, 2018), the information about the impact of moderate fields in different types of biomolecules is still scarce.

6.3.1 Electroheating Thermal effects of OH have been considerably explored in extraction processes. The use of EFs to replace traditional heating has been used in solid
liquid extraction processes both with water and with organic solvents (mainly ethanol and water/ethanol mixtures, but not exclusively). As in all solid
liquid extraction processes, the ratio solvent to matrix, solid particles’ size, mixing profiles, solvent choice, and extraction temperatures/times are critical parameters to be optimized. Phenolic compounds are the most referred group when dealing with bioactive compounds solvent extraction from natural sources. OH extraction is no exception. In fact, OH has been used in the extraction of flavonoids, and in particular anthocyanins, with similar or increased extraction yields and extracts quality. Examples of OH-assisted extraction of phenolic compounds include extraction from black rice bran (Loypimai, Moongngarm, Chottanom, & Moontree, 2015), colored potato (Pereira et al., 2016b), tropical plants (Khajehei et al., 2017) or black (fermented) tea leaves, and dried and fresh mint leaves (Sensoy & Sastry, 2004a,b). In this last case, experiments were conducted at 80
1000 V or at 210 V using electrical frequencies ranging from 50 to 5000 Hz. Higher extraction yields occur at lower frequencies, probably mainly due to a higher permeation effect (Sensoy & Sastry, 2004a,b). Furthermore, increased yields occurred only for fresh leaves, and not for the dried ones, which means that pretreatments may have a strong impact on the OH efficiency. Though reduced energy consumptions and higher yields are reported, high EFs may also lead to anthocyanins degradation. For instance, Sarkis, De´bora, Tessaro, and Marczak (2013) reported increased anthocyanins degradation in blueberries pulp for voltages higher than or equal to 200 V when compared to traditional heating (no indication about the EF strength was given), though less

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177

degradation than in the traditional process occurred for lower voltages (Sarkis et al., 2013). Anthocyanins degradation was also reported by Pereira et al. (2016b), for EFs above 20 V/cm, though high-temperature short-time OH treatments can lead to high anthocyanins extraction yields without compromising the extracts quality. Water-soluble polysaccharides may also be extracted using OH technology. In fact, pectin has been successfully extracted from orange juice waste using an EF of 15 V/cm, at 90 C during 30 min, with comparable galacturonic acid content and esterification degree, and increased emulsifying ability (Saberian, Hamidi-Esfahani, Gavlighi, & Barzegar, 2017; Saberian, Hamidi-Esfahani, Gavlighi, Banakar, & Barzegar, 2018). OH has been applied to the extraction of oils from seeds or arils and cereal brans, where EFs lower than 140 V/cm and frequencies of 1 and 60 Hz were used (Lakkakula, Rao, & Walker, 2004). Hexane is a typical solvent for solid
liquid extraction in this case. As hexane has a strong apolar character, it unsuitable for electrical processes, even though the used matrices are conductive enough. Therefore in these cases, OH has been applied mainly as a pretreatment. Nevertheless, Aamir and Jittanit (2017) reported a successful extraction of Gac aril oil using high solid-to-solvent ratios and humidified solid samples to increase the overall solid/liquid mixture conductivity (Aamir & Jittanit, 2017). Hydrodistillation is commonly applied to the extraction of essential oils. Plant material is immersed in water and heated, releasing and vaporizing the target essential oil which passes then through the condenser. This process is high energy consuming. ohmic-assisted hydrodistillation is probably the most referred application of OH to extraction processes and uses the electric heating to replace conventional heating (Gavahian & Farahnaky, 2018). It has been applied to the recovery of different essential oils from different aromatic plants, including thyme, damask rose, oregano, citronella grass, myrtle, peppermint, Pulicaria undulata, Prangos ferulacea, and eucalyptus leaves (Damyeh & Niakousari, 2016, 2017; Gavahian, Farahnaky, & Farhoosh, 2015a; Gavahian, Farahnaky, Farhoosh, Javidnia, & Shahidi, 2015b; Gavahian, Farahnaky, Javidnia, & Majzoobi, 2012, 2013; Gavahian, Lee, & Chu, 2018; Gavahian et al., 2011; Hashemi et al., 2017; Manouchehri, Saharkhiz, Karami, & Niakousari, 2018). Operating voltages ranges from 0 to 415 V, but applied EFs are rarely mentioned. The reported results indicate higher extraction yields, but the most significant increase appears in processing times, which can be up to six times faster (Al-Hilphy, 2014; Almohammed et al., 2017; Damyeh & Niakousari, 2016, 2017; Gavahian et al., 2015a,b; Gavahian et al., 2012, 2013, 2011; Hashemi et al., 2017; Manouchehri et al., 2018), when compared to traditional hydrodistillation systems, also leading to significantly reduced energy consumptions. Similar extract composition and bioactivities are usually reported, with no significant adverse effects in the characteristics of essential oils. Nevertheless, electrodes corrosion leading to extract contamination by metal ion migration has also been referred (Gavahian et al., 2018), which means that frequency and electrodes composition should be optimized and controlled to avoid this issue.

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Most common electrode materials for hydrodistillation applications include titanium, platinum, and stainless steel (Gavahian & Farahnaky, 2018).

6.3.2 Nonthermal effects in extraction processes MEF and its ease of controlling internal heat generation allow electric treatments at sublethal temperature conditions (,45 C). According to Rocha et al. (2018), MEF are only slightly used for the extraction of added value compounds. However, MEF are enlarging their place in the applications for valorization of bioresources. Electric fields were successfully used for the extraction of carotenoids and lipids from Heterochlorella luteoviridis (Jaeschke, Menegol, Rech, & Domeneghini, 2016). MEF were used as a pretreatment step, followed by a diffusive step. Before the extraction experiments the electrical conductivity of the samples was adjusted to 500 S/cm, using a solution of NaCl (2 g/L). This procedure allowed the application of relatively high voltages without increasing the temperature above 35 C. For the pretreatment process, 25% of ethanol was used with voltage set at values between 0 and 180 V (60 Hz of frequency), for 10 min, while the temperature was maintained below 35 C. For the diffusive step, ethanol concentrations varied from 25% to 75%, the temperature was maintained at 30 C for 50 min. It was observed that carotenoid extraction increased with increasing electrical field strength, while the MEF effect did not influence the lipid extraction. The authors have concluded that the voltage intensity (0
180 V) used may not be enough to promote structural changes on the cell membrane to enhance the extraction. MEF were used to enchase the extraction of pectin from the peel of passion fruits (Oliveira et al., 2015). To observe only the EF effects the experiments using MEF were conducted in temperature not higher than 50 C. Preliminary studies showed that traditional extraction of pectin begins at temperatures above 50 C. The voltage used for the experiments were 30, 50, and 100 V, for extraction time of 15 min, and with pH of 2 and temperature of 45 C. The results showed that the pectin yield increased with increasing the voltage. The pectin yield was 4.98/100 g of peel d.m. at 30 V and increased to 6.20/100 g of peel d.m. at 100 V. It was concluded that MEF is an efficient, time-saving, and eco-friendly method for the extraction of pectin from the peel of passion fruits, especially for pectin with a high esterification degree and galacturonic acid content higher than 65/100 g of pectin. However, the extraction yield of MEF was lower than that of the conventional extraction. The authors concluded that there is a need of further studies and that the utilization of MEF like a pretreatment step, during the conventional heating, can be an alternative to increase the obtained yields. In other studies the influence of MEF was studied, eliminating thermal effects as a variable by matching the temperature histories of conventional and MEF-treated samples. MEF of 80 V were applied to a fresh mint leaves, and the heating was stopped when the temperature at the center of the stirred solution reached 80 C (Sensoy & Sastry, 2004a,b). The authors concluded that MEF enhanced the leaching of solute from fresh cellular material compared with heating alone. Different EFs were also studied for the extraction of anthocyanins from purple-fleshed sweet

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179

potato (Vu, Han, & Nguyen, 2013). The applied EFs had different strengths 10, 20, and 30 V/cm (60 Hz). To match the thermal histories of the studied treatments the electrical conductivities of the solvents were adjusted using NaCl. The endpoint temperatures were set at 50 C and 70 C. Authors concluded that MEF treatment could be an alternative to conventional extraction at mild temperature conditions to efficiently extract anthocyanins and total phenolic content from plant tissues. It was also concluded that, for the different EFs strengths used, there were not any significant changes in concentrations of anthocyanins and total phenolic compounds at both 50 C and 70 C.

6.3.3 Combining ohmic heating with other extraction techniques OH can also be part of an integrated process of extraction either as pretreatment or in combination with other processing techniques, such as pulsed EFs (PEF) and ultrasounds (US). Table 6.4 indicates examples of the use of OH in extraction procedures either as pretreatment or in combination in other techniques. Pereira et al. (2016b) used OH as a pretreatment of colored potato followed by a conventional heating for the extraction of anthocyanins and polyphenols. In this case, OH was used to open the pores of the cell wall (electroporation) by combining EF effects with temperature. This pretreatment allowed to enhance the diffusional extraction of target compounds at room temperature. Different EFs were used from 0 to 200 V/cm, at temperatures ranging from 30 C to 100 C and treatment times from 1 s to 10 min. One of the best pretreatment conditions was attained when high temperature (100 C) and EF (200 V/cm) were combined and applied in about 1 s as kind of a temperature pulse. The authors concluded that the conjugation of electric treatment with elevated temperatures presents an interesting alternative for extraction processes, particularly as a first step or pretreatment. Moreover, it was showed that OH can influence both washing and diffusion of extractable anthocyanins and polyphenols. Fig. 6.2 shows the effects of OH on leakage of intracellular components from purple potato. OH was also used for the pretreatment of apple slices for the extraction of apple juice (Wang & Sastry, 2002). Low electrical current and voltage were used (40 V/cm and 60 Hz), so that the achieved temperature of the apples to be between 40 C and 50 C. The authors concluded that ohmic pretreatment provided an increasing juice yield and decreasing input work. OH was also used as a pretreatment for the extraction of oil from rice bran (Nair et al., 2012). The rice bran was pretreated for different time periods (1, 2, and 3 min) with different current values (5, 15, and 20 A) and with different concentration of sodium chloride (1, 0.1, and 0.01 M). After that, the samples were subjected to an extraction with solvent. It was found that ohmically heated rice bran with 1 M sodium chloride solution and with a current value of 20 A for 3 min gave maximum oil extraction. Moreover, the pretreatment with OH reduced the extraction time by about 70%
75% and gave maximum quantity of oil extracted when compared to bran that was not pretreated. OH proved to be an efficient way to minimize the solvent extraction time and energy consumption in the extraction of oil from rice bran. In another study, OH was used to stabilize the rice

Table 6.4 The use of ohmic heating (OH) in extraction of different types of food molecules of interest. OH-based technology

Matrix

Process

Solvent

Application

Reference

OH

Solvent extraction Solvent extraction

Water Water

Phenolic compounds Phytochemicals

Pereira et al. (2016a,b)

OH

Fruits and vegetables Plant leaves

OH

Fruit seeds/arils

n-Hexane

Carotenoids/oil

OH

Orange wastes

Solvent extraction Solvent extraction

Water

Ohmic-assisted hydrodistillation

Aromatic plants

Distillation

Water

Water-soluble polysaccharides Essential oils

OH-pretreatment

Black rice bran

Solvent extraction

OH-pretreatment

Cereal bran

MEF-pretreatment

Microalgae

MEF

Fruit residue

MEF

Leaves

OH-pretreatment

Rice bran

OH-stabilization

Rice bran

OH-pretreatment

Plant

Solvent extraction Solvent extraction Solvent extraction Solvent extraction Solvent extraction Solvent extraction Solvent extraction

PreAnthocyanins treatment: water; extraction of water
ethanol mixture 1:1 Hexane Oil

OH combined with ultrasound POH

Vegetable

OH-pretreatment

Fruit

POH-pretreatment

Fruit residue

Sugar beet

MEF, Moderate electric field; POH, pulsed ohmic heating.

Solvent extraction Solvent extraction

Solvent extraction

Ethanol

Khajehei et al. (2017) and Sensoy and Sastry (2004a,b) Aamir and Jittanit (2017) Saberian et al. (2017)

Damyeh and Niakousari (2016, 2017); Gavahian, et al. (2015a,b); Gavahian et al. (2012, 2013, 2018, 2011), Manouchehri et al. (2018), and Hashemi et al. (2017) Loypimai et al. (2015)

Lakkakula et al. (2004) Jaeschke et al. (2016)

Water

Carotenoids Lipids Pectin

Water

Soluble solids

Water

Oil

Sensoy and Sastry (2004a,b) Nair et al. (2012)

Water

Oil

Lakkakula et al. (2004)

Water

Oil

Water

Inulin

Pootao and Kanjanapongkul (2016) Khuenpet et al. (2017)

Water

Juice

Preporcic et al. (2005)

Water Extraction Ethanol

Juice

Wang and Sastry (2002) El Darra et al. (2013)

Phenolic compounds

Oliveira et al. (2015)

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181

Figure 6.2 Microscopic pictures of purple potato cells showing leakage of intracellular components and corresponding pictures of potato slices (inserts) after ohmic heating pretreatment, followed by diffusional extraction in water at room temperature: (A) untreated; (B) 90 C for 5 min at 25 kHz and 20 V/cm; and (C) 100 C for 1 s at 25 kHz and 200 V/cm.

bran with current of 1 or 60 Hz and an EF strength of 100 V/cm (Lakkakula et al., 2004). In this study, OH was found to be a successful method for stabilizing rice bran, especially when using low frequency of alternating current. OH was also used for the pretreatment of extraction of anthocyanins from rice bran (Loypimai et al., 2015). An alternating current of 50 Hz with different levels of electrical field strengths (between 50 and 200 V/cm) was used. The OH gave a higher yield of anthocyanins than that obtained by steam-assisted solvent extraction methods. Oil palm fruits were also ohmic heated using various heating conditions (temperature: 60 C
100 C; voltage: 0
150 V; heating time: 2
10 min). Increasing the voltage, temperature, and heating time significantly increased the oil yield. The maximum yield of 46.07% w/w was obtained by OH the sample at 100 C for 8 min using a voltage of 150 V (Pootao & Kanjanapongkul, 2016). OH can also be combined with PEF technology through pulsed ohmic heating (POH) that basically consists in increasing the temperature with the application of electric pulses of relatively high intensity ( . 1 kV/cm). Preporcic et al. (2005) applied POH to extract juice from sugar beet cuts. OH (60 V/cm, 50 Hz) was used to attain different temperatures (30
70 C) that were maintained during a fixed time (10
30 min). With the increase in OH duration (up to 20 min) and temperature (up to 60 C), a noticeable enhancement of mechanical extraction occurs. It was concluded that the parts of cell membranes were already destroyed by the 10 min OH. However, OH was more power consuming, compared to PEF. Nevertheless, a synergetic effect was observed when using OH (60 C) and PEF treatments, as the juice yield increased (until 87.5%). Synergy effect was also observed in respect to polyphenol extraction when POH was combined with moderate diffusion temperature (50 C) and 30% ethanol (El Darra, Grimi, Vorobiev, Louka, & Maroun, 2013). In other cases, OH was used with other type of extraction methods such as US. The combination of these two methods was used for the extraction of inulin from Jerusalem artichoke tuber (JAT) powder (Khuenpet, Fukuoka, Jittanit, & Sirisansaneeyakul, 2017). The US was used in two different ways: (1) the application of ultrasonic to the JAT powder solution before OH and (2) the application of ultrasonic after OH of the JAT powder solution. The conditions of OH were as follows: 15 or 20 V/cm, temperature of 85 C for 30 min. It was found that the combination of ultrasonic in either after or before OH did not raise the extraction yield

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from JAT powder. Moreover, the application of OH itself could not increase the inulin extraction yield comparing with the conventional heating. According to the authors, the explanation is that the extraction temperature and time are the key factors influencing to the inulin extraction yield from JAT powder more than the heating methods used. Moreover, the raw material for the inulin extraction was in powder; hence, the effect of the ohmic method on the permeabilization in the cell structure would not be apparent. Despite the contradicting results, all studies proved that when OH is used, there is diminishing of the energy cost for heating up, as well as the investment cost.

6.4

Future perspectives

Today, OH technology finds a vast number of applications in several field of sciences, such as food technology, chemical engineering, and biotechnology. OH as thermal processing technique can replace traditional heating bringing competitive advantages on operation times, heating effectiveness, end product quality (both in organoleptic and nutritional aspects), energetic efficiency, maintenance costs, and environmental impact. There is now a growing body of evidence that shows that OH is not limited to thermal operation units, such as pasteurization or sterilization operations units, and its nonthermal effects on the inactivation of certain microorganism and enzymes. The possibility of a fine-tune control of processing parameters, such as heating rate, EF applied, as well electric frequency, places OH as a promising tool to enhance and develop new functionalities or to transform important macromolecules, such as proteins, polysaccharides, and enzymes. In a moment where concerns with environmental awareness is growing, OH is also seen as sustainable and green extraction method, allowing to reduce the usage of water and chemical solvents due to its direct way of heating and unique synergy between the thermal and the electrical effects on permeabilization of vegetable tissues (i.e., electroporation). The easiness to create and adapt OH principle to certain niche applications allowed to increase the number of OH manufactures, as well as the variety and flexibility of the available commercial equipments. OH will continue to consolidate its position as reduced thermal preservation technology with an expected increase in the number of food products commercially available. But it can also be prospected that development of bioprocessing applications—aiming functionalization/transformation and extraction—of value-added molecules will start to expand rapidly. Currently, the combination of OH with other novel nonthermal processing technologies started to being investigated with exciting results.

Acknowledgments This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norte. R. Rodrigues is grateful to FCT grant (SFRH/BD/110723/2015).

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161. Available from https://doi. org/10.1016/j.cep.2017.03.025. Saberian, H., Hamidi-Esfahani, Z., Gavlighi, H. A., Banakar, A., & Barzegar, M. (2018). The potential of ohmic heating for pectin extraction from orange waste. Journal of Food Processing and Preservation, 42(2), e13458. Sakr, M., & Liu, S. (2014). A comprehensive review on applications of ohmic heating (OH). Renewable and Sustainable Energy Reviews, 39, 262
269. Available from https://doi. org/10.1016/j.rser.2014.07.061. Samaranayake, C. P., & Sastry, S. K. (2016a). Effect of moderate electric fields on inactivation kinetics of pectin methylesterase in tomatoes: The roles of electric field strength and temperature. Journal of Food Engineering, 186, 17
26. Available from https://doi. org/10.1016/j.jfoodeng.2016.04.006.

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Samaranayake, C. P., & Sastry, S. K. (2016b). Effects of controlled-frequency moderate electric fields on pectin methylesterase and polygalacturonase activities in tomato homogenate. Food Chemistry, 199, 265
272. Available from https://doi.org/10.1016/j.foodchem.2015.12.010. Samaranayake, C. P., & Sastry, S. K. (2018). In-situ activity of α-amylase in the presence of controlled-frequency moderate electric fields. LWT—Food Science and Technology, 90 (October 2017), 448
454. Available from https://doi.org/10.1016/j.lwt.2017.12.053. Sarkis, J. R., De´bora, P. J., Tessaro, I. C., & Marczak, L. D. F. (2013). Effects of ohmic and conventional heating on anthocyanin degradation during the processing of blueberry pulp. LWT—Food Science and Technology, 51(1), 79
85. Available from https://doi. org/10.1016/j.lwt.2012.10.024. Sastry, S. (2008). Ohmic heating and moderate electric field processing. Food Science and Technology International, 14(5), 419
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338. Available from https:// doi.org/10.1016/j.lwt.2016.04.015. Schler, J., Tikvah, P., & Lipshtat, O. (2002). United patent. Group 111111(12). Sengun, I. Y., Turp, G. Y., Icier, F., Kendirci, P., & Kor, G. (2014). Effects of ohmic heating for pre-cooking of meatballs on some quality and safety attributes. LWT—Food Science and Technology, 55(1), 232
239. Available from https://doi.org/10.1016/j. lwt.2013.08.005. Sensoy, I., & Sastry, S. K. (2004a). Extraction using moderate electric fields. Journal of Food Science, 69(1), 7
13. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/ j.1365-2621.2004.tb17861.x/abstract. Sensoy, I., & Sastry, S. K. (2004b). Ohmic blanching of mushrooms. Journal of Food Process Engineering, 27(1), 1
15. Retrieved from http://www.scopus.com/inward/ record.url?eid 5 2-s2.0-1942535829&partnerID 5 tZOtx3y1. Silva, V. L. M., Santos, L. M. N. B. F., & Silva, A. M. S. (2017). Ohmic heating: An emerging concept in organic synthesis. Chemistry—A European Journal, 23(33), 7853
7865. Retrieved from http://doi.wiley.com/10.1002/chem.201700307. Simpson, R., et al. (2015). Diffusion mechanisms during the osmotic dehydration of Granny Smith apples subjected to a moderate electric field. Journal of Food Engineering, 166, 204
211. Available from https://doi.org/10.1016/j.jfoodeng.2015.05.027. Singdeo, D., Dey, T., & Ghosh, P. C. (2011). Modelling of start-up time for high temperature polymer electrolyte fuel cells. Energy, 36(10), 6081
6089. Available from https://doi. org/10.1016/j.energy.2011.08.007. Somavat, R., Hussein, M. H. M., Chung, Y. K., Yousef, A. E., & Sastry, S. K. (2012). Accelerated inactivation of Geobacillus stearothermophilus spores by ohmic heating. Journal of Food Engineering, 108(1), 69
76. Available from https://doi.org/10.1016/j. jfoodeng.2011.07.028. Somavat, R., Hussein, M. H. M., & Sastry, S. K. (2013). Inactivation kinetics of Bacillus coagulans spores under ohmic and conventional heating. LWT—Food Science and Technology, 54(1), 194
198. Available from https://doi.org/10.1016/j.lwt.2013.04.004. Souza, B. W. S., et al. (2009). Effect of moderate electric fields in the permeation properties of chitosan coatings. Food Hydrocolloids, 23(8), 2110
2115. Available from https:// doi.org/10.1016/j.foodhyd.2009.03.021.

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Souza, B. W. S., et al. (2010). Influence of electric fields on the structure of chitosan edible coatings. Food Hydrocolloids, 24(4), 330
335. Retrieved from http://linkinghub.elsevier.com/retrieve/pii/S0268005X0900215X. Sun, H., Kawamura, S., Himoto, J-I., ItoH, K., Wada, T., & Kimura, T. (2008). Effects of ohmic heating on microbial counts and denaturation of proteins in milk. Food Science and Technology Research, 14(2), 117
123. Retrieved from http://joi.jlc.jst.go.jp/JST. JSTAGE/fstr/14.117?from 5 CrossRef. Tadpitchayangkoon, P., Jae, W. P., & Yongsawatdigul, J. (2012). Gelation characteristics of tropical surimi under water bath and ohmic heating. LWT—Food Science and Technology, 46(1), 97
103. Available from https://doi.org/10.1016/j.lwt.2011.10.020. Torkian Boldaji, M., Borghei, A. M., Beheshti, B., & Hosseini, S. E. (2015). The process of producing tomato paste by ohmic heating method. Journal of Food Science and Technology, 52(6), 3598
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2317. Vu, N.T., Han, B.N., & Nguyen, L.T. (2013). Moderate electric field (MEF) assisted extraction of anthocyanins from purple-fleshed sweet potato. In: 13th ASEAN food conference, September 9
11, 2013. Wang, W. C., & Sastry, S. K. (2002). Effects of moderate electrothermal treatments on juice yield from cellular tissue. Innovative Food Science and Emerging Technologies, 3(4), 371
377. Wongsa-Ngasri, P., & Sastry, S. K. (2015). Effect of ohmic heating on tomato peeling. LWT —Food Science and Technology, 61(2), 269
274. Available from https://doi.org/ 10.1016/j.lwt.2014.12.053. Yildiz, H., & Guven, E. (2014). Industrial applications and potential use of ohmic heating for fluid foods. Bulgarian Chemical Communications, 46, 98
102. Retrieved from http://bcc.bas.bg/BCC_Volumes/Volume_46_Special_B_2014/BCC-46-B-98102.pdf. Yin, Z., Hoffmann, M., & Jiang, S. (2018). Sludge disinfection using electrical thermal treatment: The role of ohmic heating. Science of the Total Environment, 615, 262
271. Available from https://doi.org/10.1016/j.scitotenv.2017.09.175. Yongsawatdigul, J., Park, J. W., Kolbe, E., Abu Dagga, Y., & Morrissey, M. T. (1995). Ohmic heating maximizes gel functionality of pacific whiting surimi. Journal of Food Science, 60(1), 10
14. Retrieved from http://doi.wiley.com/10.1111/j.1365-2621.1995. tb05595.x. Yoon, S. W., Lee, C. Y. J., Kim, K. M., & Lee, C. H. (2002). Leakage of cellular materials from Saccharomyces cerevisiae by ohmic heating. Journal of Microbiology and Biotechnology, 12(2), 183
188. Zell, M., James, G. L., Cronin, D. A., & Morgan, D. J. (2010a). Ohmic cooking of whole beef muscle—Evaluation of the impact of a novel rapid ohmic cooking method on product quality. Meat Science, 86(2), 258
263. Available from https://doi.org/10.1016/j. meatsci.2010.04.007. Zell, M., James, G. L., Cronin, D. A., & Morgan, D. J. (2010b). Ohmic cooking of whole turkey meat—Effect of rapid ohmic heating on selected product parameters. Food Chemistry, 120(3), 724
729. Available from https://doi.org/10.1016/j. foodchem.2009.10.069.

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Pressure hot water processing of food and natural products

7

Merichel Plaza, Marı´a Castro-Puyana and Marı´a Luisa Marina Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, University of Alcala´, Alcala´ de Henares, Madrid, Spain

7.1

Introduction

Current society standards demand the protection of the environment and the development of sustainable processes. In this sense, it is important that the food industry develops faster, less toxic, and more environmentally sustainable processing technologies. Then, an extraction technique shall accomplish as many of the 12 principles of green chemistry as possible (see Fig. 7.1) (Anastas & Kirchhoff, 2002). From these 12 principles, 7 of them can be taken out for a green extraction chemistry (they are marked inside boxes in Fig. 7.1). As a consequence, one of the main factors to be considered when proposing to change from a current extraction method to a greener one is the choice of solvent. The degree of environmental impact changes according to the type of solvent used, because it depends on the way natural resources are harvested, energy usage, and emissions to air and water from the production and use of solvents, transportation, and disposal or recycling (Turner & Iba´n˜ez, 2011). In this sense, water can be considered as a potentially green solvent since it is nontoxic to health and the environment and is the safest and least expensive solvent. The fact that water is one of the few “green” solvents capable of tuning their properties by changing the temperature has contributed to an exponential growth in the number of publications using pressurized hot water extraction (PHWE) as a “green” extraction technique in the last 10 years (see Fig. 7.2). PHWE (also called subcritical water extraction and superheated water extraction) is based on the use of water subjected to high enough temperatures (usually above its boiling point) and pressures to keep the water in the liquid state. Therefore water in liquid state as a solvent at temperatures above its boiling point (100 C, 0.1 MPa) and below its critical point (374 C, 22.1 MPa) is employed in PHWE (Plaza & Turner, 2015). The fundamentals of PHWE and its instrumental requirements are described in this chapter together with some of its recent (years 2016
present) key applications to recover high-added value compounds from plants, foods, and food by-products. The applications of PHWE found in the literature generally deal with extractions at analytical scale and to a lesser extent on a pilot scale. However, industrial applications have not been found mainly because of the absence of industrial systems and the need for more economic studies (Turner & Iba´n˜ez, 2011). That is why PHWE Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00007-0 © 2019 Elsevier Inc. All rights reserved.

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Figure 7.1 The 12 principles of green chemistry. Source: Reprinted with permission from Anastas, P. T., & Kirchhoff, M. M. (2002). Origins, current status and future challenges of green chemistry. Accounts of Chemical Research, 35, 686
694.

Figure 7.2 Number of research articles published in the last 10 years (from 2009 to present) grouped by period of 2 years dealing with pressurized hot water extraction from Scopus database (keywords: “Subcritical water extraction” or “Pressurized hot water extraction”).

applications discussed in this chapter are mainly at analytical scale. In addition, the use of pressurized hot water to achieve hydrolysis reactions and the food quality and safety using this extraction technique are considered. Finally, the environmental impact of PHWE as well as an outline of future trends on PHWE are addressed.

7.2

Fundamentals of pressurized hot water extraction

As mentioned above, the principle of PHWE relies on the use of water at high pressures and temperatures, always below its critical point, to keep water in the liquid

Pressure hot water processing of food and natural products

195

state during the whole extraction process. The use of these elevated temperatures and pressures usually allows to achieve faster extractions with yields normally higher than those obtained at normal conditions. Under high temperature and pressure, the different physical and chemical properties of water change dramatically as it can be seen in Table 7.1 (Plaza & Turner, 2015). Parameters, such as extraction temperature, pressure, time, and the addition of an organic solvent or the water flow rate, have an influence on PHWE. Among them, the temperature shows the highest effect on extraction efficiency and selectivity. One of the most relevant effects produced by the increase in temperature is the weakening of hydrogen bonds which results in a lower dielectric constant (also named as relative static permeability, ε) (Ong, Cheong, & Goh, 2006). As Table 7.1 shows, this value decreases from 78.5 at 25 C to 14.1 at 350 C, that is, the water polarity decreases when increasing the temperature reaching similar values than common organic solvents, such as ethanol or methanol, at room temperature (see Fig. 7.3) (Castro-Puyana, Herrero, Mendiola, & Iba´n˜ez, 2013a). This means that PHWE can be used, depending on the temperature, to extract polar to Table 7.1 Chemical and physical properties of water at different temperatures and pressures. Property

T 5 298K (25 C, 0.1 MPa)

T 5 373K (100 C, 0.1 MPa)

T 5 473K (200 C, 1.5 MPa)

T 5 623K (350 C, 17 MPa)

Dissociation constant, Kw pKw Relative static permittivity, εr Dipole moment Specific heat capacity, Cp (J/g/K) Heat of vaporization, Hv (kJ/mol) Density (g/cm3) Dynamic viscosity, η (mPa s) Surface tension (dyn/cm) Self-diffusion coefficient, D (m2/s)

1.0 3 10214

5.6 3 10213

4.9 3 10212

1.2 3 10212

13.99 78.5

12.25 55.4

11.31 34.8

11.92 14.1

1.85 4.18

1.85 4.22

1.85 4.51

1.85 10.1

44.0

40.7

35.0

15.6

0.997 0.891

0.958 0.282

0.865 0.134

0.579 0.067

72.0

58.9

37.6

3.7

2.3 3 1029

8.6 3 1029

23.8 3 1029

N/A

Source: Reprinted with permission from Plaza, M., & Turner, C. (2015). Pressurized hot water extraction of bioactives. Trends in Analytical Chemistry, 71, 39
57.

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Green Food Processing Techniques

Figure 7.3 Variation of the dielectric constant of water as a function of the temperature. The figure shows the values corresponding to some common organic solvents at room temperature. Source: Reprinted with permission from Castro-Puyana, M., Herrero, M., Mendiola, J. A., & Iba´n˜ez, E. (2013a). Subcritical water extraction of bioactive components from algae. In H. Domı´nguez (Ed.), Functional ingredients from algae for food and nutraceuticals. Woodhead Publishing Limited, Cambridge, pp. 534
560.

medium polar and even nonpolar compounds. Moreover, an increase in temperature (1) favors analyte diffusion since diffusivity of water at 200 C is around 10 times higher than at 25 C, (2) improves mass-transfer kinetics by disrupting intermolecular forces, (3) decreases the viscosity which favors a better penetration of matrix particle, and (4) decreases the surface tension enabling the water to better wet the sample (Castro-Puyana, Marina, & Plaza, 2017; Herrero, Castro-Puyana, Mendiola, & Iba´n˜ez, 2013). For a deeper knowledge about the effect of increasing the temperature on PHWE, readers are referred to Plaza and Turners’s review (Plaza & Turner, 2015). In spite of the advantages of increasing the temperature, it should be also taken into account that the extraction could be less selective (because an increase in the temperature increases not only the solubility of the analyte but also the solubility of other compounds in the matrix), the compounds can be degraded (higher temperatures should be only considered for thermostable compounds), and chemical reactions can occur, such as hydrolysis and oxidation, which may give rise to the formation of toxic compounds (see Section 7.6) (Gilbert-Lo´pez, Plaza, Mendiola, Iba´n˜ez, & Herrero, 2017; Teo, Tan, Hong Yong, Hew, & Ong, 2010). Extraction pressure is a necessary requisite in PHWE since it permits the water to be in its liquid state when high temperatures are employed. Even though it is logical to think that an increase in the pressure may help to improve the extraction

Pressure hot water processing of food and natural products

197

efficiency (it can permit a better penetration of the water in the sample matrix), the truth is that it is recognized for many raw materials (grinded and pretreated correctly) that no significant effect is observed when increasing the pressure (Turner & Iba´n˜ez, 2011). Regarding the extraction time, it starts once the extraction cell that contains the sample is filled with water at the desired values of temperature and pressure to carry out the extraction. Along with the kind of sample to be extracted, the type of extraction is a critical factor in the selection of the extraction time. Usually, the static mode is the most employed type of extraction. Here, a certain amount of water is maintained in contact with the sample for a given time. During this time, the compound still bound to the matrix and the water phase, in which the components are already solubilized, could achieve an equilibrium. After reaching this point, the extraction efficiency will not increase and the degradation of different compounds may take place more easily (Castro-Puyana et al., 2013a). When PHWE is performed under the dynamic mode, in which the water continuously flows into the extraction cell, the equilibrium is avoided so that it is theoretically more favorable for a complete extraction. In this extraction mode, another parameter that must be taken into consideration is the flow rate since it influences the time needed to complete the extraction. Basically, the flow rate should permit the solubilization of the analyte in water by means of a short contact time between it and the sample. Although working at continuous flow with a high water flow rate is a way to diminish degradation and chemical reactions of the analytes, it also implies a dilution of the obtained extract which could be not adequate for its analytical determination (Gilbert-Lo´pez et al., 2017). The addition of organic or inorganic solvents, surfactants, or additives can be used to improve the extraction efficiency since they may facilitate the analyte solubility in water and change the properties of the matrix and the desorption of the analytes (Borisova, Statkus, Tsizin, & Zolotov, 2017; Gilbert-Lo´pez et al., 2017). Besides the above mentioned parameters, there are others that can also have influence on the extraction efficiency by PHWE, for instance, the physical state of the sample. In fact, the matrix should be treated before PHWE and the particle size can affect the mass transfer (a better accessibility of the water to the analyte is achieved by larger surface area per unit mass). Moisture content and solvent-tosample ratio in static extraction should also be considered to obtain a higher extraction yield (Gilbert-Lo´pez et al., 2017).

7.3

Instrumentation

The basic instrumental setup for PHWE is simple. As can be seen in Fig. 7.4, it consists of a water container, a pump for transporting the water, an oven containing the extraction cell, a valve or restrictor to keep the pressure inside the system, a vessel to collect the extract, and an inert gas, as nitrogen, to purge the system once the extraction is over. Usually, the working temperatures and pressures range from

198

Green Food Processing Techniques

Figure 7.4 Basic scheme of a PHWE system. PHWE, Pressurized hot water extraction.

room temperature to 200 C, and from 35 to 200 bars, respectively. It is important to take into consideration that the water employed to carry out the extraction should be degassed, generally by using ultrasound or a helium purge, not only to eliminate the oxygen and avoid the oxidation of the extracted compounds but also to prevent cavitation in the pump and corrosion in connecting lines (due to the use of water at high temperature). The basic above mentioned instrumentation may differ depending on whether a static or a dynamic mode is used to perform the extraction. The former is a batch process with one or several extraction cycles with the replacement of solvent in between. Basically, the different steps involved in the extraction procedure in the static mode are (1) preheating, in which the thermal expansion of the water takes place causing an increase in the pressure (the desired pressure is kept by the valve by releasing solvent), (2) extraction during a selected time (5
30 min) once the values of temperature and pressure are reached, (3) solvent replacement when extraction cycles are employed, (4) system purge, it means that after the last cycle, the extraction cell is purged with an inert gas to remove the remaining solvent from the cell to the collection vessel, (5) depressurizing the system at atmospheric conditions (Turner & Iba´n˜ez, 2011). In dynamic PHWE the water is continuously pumped (at a selected flow rate) through the extraction cell. Due to the need to control the water flow rate, this mode requires a more sophisticated high-pressure pump along with a pressure restrictor rather than a static open/close valve. Working in the dynamic mode may avoid thermal degradation of compounds because water is continuously flowing through the sample at a certain fluid velocity that improves the efficiency of the extraction avoiding the excessive heating of the sample (Herrero, Mendiola, Castro-Puyana, & Iba´n˜ez, 2012). Till now, there are not many dynamic systems commercially available. In any case, readers interested in building their own PHWE system to perform both dynamic and static extractions are referred to Turner and Iba´n˜ez (2011) where a complete description of how to build your own system is shown.

Pressure hot water processing of food and natural products

7.4

199

Applications in the extraction of food ingredients from foods and natural products

Nowadays, there is an increasing interest in developing environmentally sustainable applications with the basic idea of isolating bioactive or health-promoting compounds present in foods and natural products for later use as food ingredients. There is a clear trend of increase in the number of relevant publications dealing with the extraction using PHWE in the last years (see Fig. 7.2). Furthermore, the extraction of bioactive compounds from plants and natural sources has been addressed in deep in several reviews (Castro-Puyana et al., 2017; Herrero et al., 2013; Lachos-Pe´rez et al., 2017; Plaza & Turner, 2015; Teo et al., 2010; Zakaria & Kamal, 2016). Table 7.2 summarizes some of the PHWE applications reported in the last 3 years (from 2016 to present). Many of them are related with the extraction of phenolic compounds; mono-, di-, and triterpenes; polysaccharides; and proteins with bioactive properties that can be used to improve human health. Phenolic compounds are classified into different classes according to the number of phenol rings that they contain and to the structural elements that bind these rings to one another. The main groups are phenolic acids, phenolic alcohols, flavonoids (flavonols, flavones, isoflavones, flavonones, anthocyanidins, and flavanols), stilbenes, and lignans (D’Archivio et al., 2007; Manach, Scalbert, Morand, Re´me´sy, & Jime´nez, 2004). They have an important role in the prevention of several pathologies associated with the oxidative stress, such as cancer, and cardiovascular and neurodegenerative diseases (Abbas et al., 2017). Phenolic compounds have different relative polarity and different stability depending on their chemical structure. This should be taken into account for the selection of the most adequate parameters giving rise to appropriate extraction conditions. The parameters mainly affecting PHWE of phenolic compounds are temperature and extraction time, aside from structural characteristics that affect the solubility of these bioactive compounds in the extraction solvent. As it is described in Section 7.2, the dielectric constant of water decreases when the temperature increases, which means that the water properties can be changed, resulting in an enhancement on the solubility of the compounds of interest, an improvement of water diffusivity, and a decrease in water viscosity. Then, water can have a better penetration into the matrix and faster mass transfer of the analytes. Phenolic compounds have been extracted by PHWE from different matrices, such as plants and different types of food and agrofood-industry by-products. As can be observed in Table 7.2, in many works, a higher antioxidant capacity and total phenolic content have been noticed in the extracts obtained at temperatures over 160 C and at longer extraction times (15
30 min), compared to the extracts obtained at lower temperatures and shorter extraction times (Munir, Kheirkhah, Baroutian, Young Quek, & Young, 2018; Pavlic et al., 2016; Zakaria, Mustapa Kamal, Harun, Omar, & Siajam, 2017). In many of these studies, only the total phenolic compounds and the total antioxidant capacity were measured. This can affect the trueness of the results because these assays do not provide so much information

Table 7.2 The most remarkable applications in pressurized hot water extraction published in the period 2016
present. Compounds of interest/bioactivity (method of analysis)

Temperature ( C)

Pressure (MPa)

Static/ Time/Flow Dynamic rate

Others

References

Vine shoot wastes

Phenolic compounds (HPLC
DAD) Antioxidants capacity (FRAP, DPPH) Antimicrobial activity

150

4.0

Static

40 min

Moreira et al. (2018)

Pistachio (Pistacia vera L.) hulls

Phenolic composition (HPLC
MS) Antioxidant capacity (DPPH, ABTS, FRAP)

150
170

6.9

Dynamic

Chlorella sp. microalgae

Total phenolic content (FC) Antioxidant capacity (DPPH) Phenolic acids (HPLC
DAD) Total phenolic content (FC) Total flavonoid content (aluminum chloride method) Antioxidant capacity (DPPH) Flavonoids (HPLC
DAD) Total phenolic content (FC) Antioxidant capacity (FRAP, DPPH) Phenolic composition (HPLC
DAD)

163




Static

4 mL/min total volume 120 mL 5 min

Frequency of the vibrational platform: 3 Hz


Zakaria et al. (2017)

170
230

3.0

Static

30 min

20 wt.% microalgae concentration


160

1.0

Static

30 min

Agitation rate 3 Hz

Nastic et al. (2018)

Total phenolic content (FC) Total flavonoid content (aluminum chloride method) Antioxidant capacity (DPPH, TEAC, and reducing power assay) Chlorogenic acids and flavonoids (UHPLC
MS)

201.5

20.0

Static

15.8 min




Pavlic et al. (2016)




Hamany Djande, Piater, Steenkamp, Madala, and Dubery (2018) Cvetanovı´c et al. (2018)

Raw material

Phenolic compounds

Waste onion

Mountain germander (Teucrium montanum L.) Sage (Salvia officinalis L.)

Moringa oleı´fera leaves Chamomile ligulate flowers

Phenolic composition (HPLC
DAD
MS) Antioxidant capacity (DPPH, OH, ABTS)

Ersan et al. (2018)

Munir et al. (2018)

30 min 100

6.9

Dynamic

100

3.0
4.0

Static

3 mL/s total volume 25 mL 30 min

Stirring process

Immature fruit

Momordica foetida

Cocoa powder, chocolate, and nibs Black tea

Defatted orange peel Plantago major and Plantago lanceolata

Morus nigra L. fruits

40
45 min/ 1.2 mL/ min 5 mL/s total volume 50 mL 3 min







Dynamic

24.5 min/ 12 mL/ min 10 mL/min




Lachos-Pe´rez et al. (2018)

10.0

Static

20 min




Mazzutti et al. (2017)

Sequential extractions (25, 50, 100, 150, and 200) 120

15.0

Dynamic

60 min/ 2 mL/ min




Koyu, Kazan, Kurtulus Ozturk, YesilCeliktas, and Zeki Haznedaroglu (2017)

170




Dynamic




Wang et al. (2018)

90

10.3

Static (1 cycle)

55 min/ 3 mL/ min 5 min

Modifier: 15% ethanol combined with resin purification process

Mariotti-Celis et al. (2018)

Total phenolic content (FC) Antioxidant capacity (ORAC) Cytoprotective activity (cell viability) Flavonoids (UHPLC
MS)

100

1.0
1.5

Dynamic

250

6.9

Dynamic

Phenolic composition (HPLC
DAD
ECD
CAD, HPLC
FLD, HPLC
MS)

125

10.3

Static

Epicatechins (HPLC
UV/vis) Theophylline (HPLC
UV/vis) Caffeine (HPLC
UV/vis) Flavanones (HPLC
UV) Total phenolic content (FC) Antioxidant capacity (DPPH, FRAP, and ORAC) Total phenolic content (FC) Total antioxidant capacity (DPPH and ABTS) Phenolic compounds: plantamajoside, verbascoside, and isoverbascoside (HPLC
MS)

160

0.8

Dynamic

150

10.0

200

Lycium ruthenicum Murr.

Total phenol content (FC) Total flavonoid content (aluminum chloride method) Total anthocyanin content (pH differential method) Qualitative and quantitative determination of anthocyanins (UHPLC
DAD
MS) Total anthocyanin content (pH differential method) Anthocyanins (HPLC
DAD and UHPLC
MS)

Vitis vinifera “Carme´ne`re” pomace

Proanthocyanidins (HPLC
FLD)

Total phenolic content (FC)





Heng, Katayama, Mitani, Ong, and Nakamura (2017) Khoza et al. (2016)

Plaza, Oliveira, Nilsson, and Turner (2017) He et al. (2018)

(Continued)

Table 7.2 (Continued) Raw material

Compounds of interest/bioactivity (method of analysis)

Temperature ( C)

Pressure (MPa)

Static/ Time/Flow Dynamic rate

Others

References

Pueraria lobata

Isoflavones (HPLC
UV) Puerarin 30 -methoxypuerarin Daidzein Daidzin

120 120 140 160 200




Static

45 min

Liquid:solid ratio: 1:15

Zhang, Liu, et al. (2018)

Total antioxidant capacity (DPPH) Total phenolic content (FC) Total flavonoid content (aluminum chloride method) Phytochemical (HPLC
MS) Shanzhiside methyl ester (iridoids glycosides)

200

10.0

Static

20 min




Ko et al. (2017)

Steviol glycosides: stevioside and rebaudioside A (HPLC
UV)

160

10.3

Static (3 10 min cycles)




Kovacevic et al. (2018)

Saponins (colorimetric assay and MS)

195

10.3

Static (1 cycle)

1 min




Gil-Ramı´rez et al. (2018)

Total saponins (colorimetric assay)

207

4.35

Static

15 min

Total phenolic compounds (FC) Total antioxidants (ABTS) Phenolic compounds (HPLC
DAD) Total ginsenosides (colorimetric assay) Total phenolic content (FC) Total sugars (phenol-sulfuric acid method) Total proteins (Bradford assay) Antioxidant capacity (ABTS, DPPH) Ginsenosides (UHPLC
MS)

Solid/Liquid ratio: 0.04 mg/mL Agitation speed: 199 rpm

Saravana, Getachew, et al. (2016), Saravana, Cho, et al. (2016)

200 200 200 180 200 160

6.0

Static (2 20 min cycles)




Zhang, Zhang, et al. (2018)

Monoterpenes Phlomis umbrosa Turcz

110

1 min

Diterpenes Stevia rebaudiana Bertoni leaves

Triterpenes Quinoa stalks (Chenopodium quinoa Wild.) Ginseng (Panax ginseng Meyer)

Ginseng roots (Panax ginseng C.A. Mey)

Polysaccharides Saccharina japonica

Fucoidan

127

8.0

Static

11.98 min

Pomelo(Citrus grandis (L.) Osbeck) peels Ganoderma lucidum

Low methoxyl pectin

120

3.0

Dynamic

ß-Glucan

155
160

5.0

Static

20 min/ 1 mL/ min 92 min

Polysaccharides Fructooligosaccharides Beta-ecdysone

115 120 120

0.2 12.0

Static Static

1h 5 min 15 min





Proteins (SDS
PAGE)

50

15.0

Static

5 min




Laminaria japonica Brazilian ginseng roots

Modifier: 0.1% NaOH Solid/ liquid ratio: 0.04 g/mL Agitation speed: 300 rpm


Saravana et al. (2018)




Benito-Roma´n, Alonso, Cocero, & Goto (2016) Gao et al. (2017) Vardanega et al. (2017)

Liew et al. (2018)

Proteins Sambucus nigra L. branches (elderberry)

Salplachta and Hohnova´ (2017)

ABTS, 2,20 -Azinobis-(3-ethylbenzothiazoline-6-sulfonate); CAD, charged aerosol detector; DAD, diode array detector; DPPH, α-diphenyl-β-picrylhydrazyl; ECD, electrochemical detector; FC, Folin
Ciocalteu assay; FLD, fluorescence detector; FRAP, ferric reducing ability of plasma; HPLC, high-performance liquid chromatography; MS, mass spectrometry; OH, hydroxyl radical scavenging activity; ORAC, oxygen radical absorbance capacity; SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis; TEAC, Trolox equivalent antioxidant capacity; UHPLC, ultra-high performance liquid chromatography; UV, ultraviolet; vis, visible.

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about what phenolic compounds are in the extracts. It is well known that, for instance, the Folin
Ciocalteu (FC) method may overestimate the content of phenolic compounds when there are other compounds with reducing groups present that can also transfer electrons to molybdenum, being nonspecific to phenolics (Karadag, Ozcelik, & Saner, 2009). Neoformation of unwanted antioxidant compounds at elevated temperatures during PHWE can happen, and it might affect the trueness of the data of these assays (see Section 7.6). Therefore more advanced analytical techniques are necessary to quantify phenolic compounds as well as other bioactive compounds. One example was the work presented by Mazzutti, Salvador Ferreira, Herrero, and Iba´n˜ez (2017). They carried out the extraction of bioactive compounds from Plantago major and Plantago lanceolata by PHWE employing different extraction temperatures (25 C
200 C). When the obtained extracts were characterized in terms of total antioxidant capacity (α-diphenyl-β-picrylhydrazyl radical scavenging and Trolox equivalent antioxidant capacity assays) and total phenol content (FC assay), the highest levels were obtained at 200 C. They noticed that the high antioxidant capacity and phenolic content could be correlated not only to the amount of phenolic compounds (verbascoside, isoverbascoside, and plantamajoside) analyzed by more advanced analytical techniques like high-performance liquid chromatography coupled to mass spectrometry detection (HPLC
MS) but also to the neoformation of antioxidants due to the reactions promoted at high temperature (Mazzutti et al., 2017). The use of dynamic extractions could prevent the unwanted reaction promoted at high temperatures (see Section 7.6). For instance, the extraction temperature (100 C
300 C) was tested in the optimization of PHWE of flavonoids from Momordica foetida, while the pressure (6.9 MPa) and flow rate (5 mL/s until a total volume of 50 mL of extract collected) were kept constant in all extractions (Khoza et al., 2016). The ultra-high performance liquid chromatography-quadrupole time of flight mass spectrometry (UHPLC
qTOF
MS) analysis of PHWE extracts showed that temperatures between 150 C and 200 C were optimal for the extraction of flavonoid molecules. Therefore when PHWE was carried out in static mode, the optimal temperatures to extract flavonoids were lower than the ones in dynamic mode (Table 7.2). Thus the extraction temperature is one of the most important parameters in order to be successful in the extraction of phenolic compounds by PHWE, but other parameters associated with temperature, such as contact and residence time, are also demonstrated to have adverse effects. A high enough water flow rate decreases the residence time for the analytes in the hot water, enhances the extraction rate of the analytes if the kinetics is limited by the solubility in the solvent, and may minimize the unwanted chemical reactions during PHWE (Plaza & Turner, 2015). However, a too high water flow rate will lead to unnecessary extract dilution and may necessitate a concentration step after PHWE. If the extraction kinetics is mainly limited by desorption and diffusion inside the pores of the sample matrix, then a higher flow rate will not improve the extraction rate (Liu, Sandahl, Sjoberg, & Turner, 2014; Plaza & Turner, 2015). Therefore the flow rate is a parameter that needs to be optimized on a dynamic mode of PHWE. For instance, the extraction temperature (120 C
180 C) and water flow rate

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205

(6
18 mL/min) were optimized in order to extract flavanols and methylxanthines from black tea by PHWE (He et al., 2018). The extraction of flavanols enhanced continuously as the flow rate increased at 140 C, reaching maximal values at 160 C and 12 mL/min. However, the flow rate had a negative effect on theophylline extraction at both 140 C and 160 C. High temperatures and low flow rates (long residence time) were positive for theophylline extraction, being the optimal extraction conditions at 180 C and 6 mL/min (He et al., 2018). Depending on the type of phenolic compounds to be extracted, the optimal extraction conditions can notably change. For example, four different isoflavones were extracted by PHWE from Pueraria lobata (Zhang, Liu, et al., 2018). With an extraction time of 45 min, the extraction yields of puerarin, 30 -methoxypuerarin, and daidzin reached the highest levels at extraction temperatures of 120 C, 140 C, and 200 C, respectively (Table 7.2). However, the extraction yield of daidzein remained constant from 100 C to 160 C and increased sharply when the extraction temperature exceeded 160 C. At 160 C, daidzin degraded and produced daidzein, so the extraction yield of daidzein increased obviously. Moreover, puerarin, 30 methoxypuerarin, and daidzin were degraded and produced various compounds due to hydrothermal reactions at higher temperatures. The maximal extraction yields of the total isoflavones were obtained by response surface methodology at extraction times of 45 min and extraction temperatures of 120 C (Zhang, Liu, et al., 2018). As this study showed, each isoflavone presented a different optimum extraction temperature which must be considered when PHWE is carried out. On the other hand, the use of acids in order to modify water and enhance extraction efficiency in some applications is needed for some compounds. For example, anthocyanins, an important type of phenolic compounds, are extracted most efficiently using acidified water and temperatures between 60 C and 80 C (Plaza & Turner, 2015). However, these compounds can also be extracted with neat water. Wang et al. (2018) optimized a dynamic PHWE of anthocyanins from Lycium ruthenicum Murr. with neat water by response surface methodology combined with Box
Behnken design. They studied the effect of extraction temperature (110 C), time (30
90 min), and flow rate (1
3 mL/min). The optimal extraction conditions were at temperatures of 170 C, times of 55 min, and flow rates of 3 mL/min. PHWE was more efficient for the extraction of anthocyanins than the use of conventional extraction methods with hot water or methyl alcohol. In summary, Table 7.2 shows that PHWE conditions mostly employed to achieve the extraction of phenolic compounds were extraction temperatures ranging from 90 C to 150 C and extraction times of 1
30 min (Castro-Puyana et al., 2017; Cvetanovı´c et al., 2018; Mariotti-Celis et al., 2018; Mazzutti et al., 2017; Moreira et al., 2018; Plaza, Abrahamsson, & Turner, 2013; Plaza & Turner, 2015; Zhang, Liu, et al., 2018). In addition, other PHWE application is the extraction of mono-, di-, and triterpenes. For instance, the PHWE of monoterpene shanzhiside methyl ester of the iridoids glycosides from Phlomis umbrosa Turcz with biological and pharmaceutical activities was studied (Ko, Lee, Nam, & Chung, 2017). The PHWE of this monoterpene decreased with increasing temperatures, and the optimal extraction conditions

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were 110 C for 1 min because the melting point of shanzhiside methyl ester was relatively low (see Table 7.2). The extraction yield of shanzhiside methyl ester in PHWE was higher compared with the yields obtained with conventional extraction methods employing methanol, ethanol, and hot water at boiling point (Ko et al., 2017). Among the most well-known alternatives to sucrose are steviol glycosides (steviosides), which are diterpene glycosides extracted from the leaves of Stevia rebaudiana Bertoni (family Asteraceae). These compounds are approximately 300 times sweeter than sucrose. Kovacevic et al. (2018) revealed a clear influence of all PHWE parameters, especially temperature, on the extraction of steviol glycosides. Hence, the highest contents of stevioside and rebaudioside A by PHWE were achieved at 160 C for 10 min using three extraction cycles (Kovacevic et al., 2018). However, another study found optimal conditions that yielded the highest recovery for steviol glycosides at 100 C for 4 min using one extraction cycle (Jentzer, Alignan, Vaca-Garcı´a, Rigal, & Vilarem, 2015). Similar optimal extraction conditions were obtained in the first study about the dynamic extraction of steviosides by PHWE (Teo, Tan, Yong, Hew, & Ong, 2009) with an optimum temperature of 100 C and optimum extraction time of 15 min at constant flow rate of 1.5 mL/min. PHWE has demonstrated that it is a successful technique to extract steviosides from S. rebaudiana Bertoni (Jentzer et al., 2015; Teo et al., 2009). On the other hand, saponins are triterpenes glycosides which have potential value in brewing, cosmetics, and detergent production due to their foaming properties at low concentrations. Also, they are used as fungicide product, due to their antibiotic and antifungal properties, and these compounds have several other reported biological activities (Gil-Ramı´rez et al., 2018). Saponins were extracted using PHWE from quinoa stalks (Gil-Ramı´rez et al., 2018) and ginseng (Saravana, Getachew, et al., 2016). The greatest content of saponins was achieved at the extraction temperature of 195 C and 207 C, respectively. However, the extraction times were shorter for the extraction of saponins from quinoa stalks (1 min) than from ginseng (15 min). These compounds were less sensitive to the temperature, therefore, elevate extraction temperatures (c.200 C) but with short extraction times (1
15 min) can be employed on PHWE of saponins (Table 7.2). Different types of polysaccharides have been obtained from different natural products, foods, and food by-products by PHWE. For example, low methoxyl pectin was extracted from pomelo peel using PHWE in a dynamic mode (Liew, Teoh, Tan, Yusoff, & Ngoh, 2018). The effect of pressure and temperature was investigated by a face-centered central composite design, and the optimal operating conditions were 120 C and 30 bar (Table 7.2). The effect of the pressure in the PHWE of low methoxyl pectin was insignificant while the temperature played a significant role. The degradation of pectin was suggested at high temperature and/or prolonged extraction times (Liew et al., 2018). Moreover, fucoidan was extracted from the brown macroalgae Saccharina japonica by PHWE (Saravana et al., 2018). Fucoidan is a characteristic compound of the brown macroalgae that has shown several bioactivities (Jhamandas, Wie, Harris, Mac Tavish, & Kar, 2005). In order to

Pressure hot water processing of food and natural products

207

determine the optimal extraction conditions of fucoidan, a desirability function method was applied and the best extraction conditions were 127.01 C, 80 bar, 11.98 min, solid
liquid ratio of 0.04 g/mL, and 300 rpm of agitation speed (Table 7.2). A 0.1% NaOH was employed in all extractions because in a previous work, higher extraction yields of fucoidan were observed under these conditions (Saravana, Cho, Park, Woo, & Chun, 2016). Under all these suggested conditions, fucoidan yields obtained by experimental extractions were closely related with the predicted values, which suggested that the employed method could be effectively used to extract fucoidan from S. japonica (Saravana, Cho, et al., 2016). On the other hand, bioactive polysaccharides were extracted by PHWE from other brown macroalgae called Laminaria japonica and similar extraction temperature (115 C) but longer extraction times (1 h) were used (Gao, Lin, Sun, & Zhao, 2017). PHWE was applied for isolation of prebiotic carbohydrates, such as fructooligosaccharides from Brazilian ginseng roots (Vardanega, Carvalho, Santos, & Meireles, 2017). It was observed that at temperatures above 120 C for 15 min, the prebiotic carbohydrate content decreased. As it is described in Section 7.6, fructooligosaccharides were degraded at higher temperatures due to caramelization and Maillard reactions (Vardanega et al., 2017). In general, the optimal extraction conditions to achieve the highest content of polysaccharides were medium temperatures ranging from 115 C to 127 C for times from 12 min to 1 h (see Table 7.2). PHWE was optimized for an efficient extraction of proteins from elderberry (Sambucus nigra L.) branches (Salplachta & Hohnova´, 2017). This extraction technique demonstrated to be suitable and reproducible at low extraction temperatures of 50 C, pressure of 15 MPa, and 5 min of extraction time. PHWE has been coupled to other techniques to increase the efficiency on the extraction of antioxidant compounds or to obtain dry extracts, thus avoiding freeze-drying step. For example, water extraction and particle formation online (WEPO) is a process that combines PHWE with particle formation online using supercritical CO2 as a dispersant and hot nitrogen for drying the produced fine droplet. The WEPO process was employed for the extraction of antioxidants from rosemary leaves (Herrero, Plaza, Cifuentes, & Iba´n˜ez, 2010; Rodrı´guez-Meizoso et al., 2012) and for the extraction of quercetin derivatives from onion waste (Andersson, Lindahl, Turner, & Rodriguez-Meizoso, 2012). On the other hand, PHWE with in-site particle generation in hot air assistance was successfully used to isolate phenolic compounds from black carrot (Uzel, 2017). The later system generated the nebulization of extracts and dried the droplet of extracts with compressed air while WEPO used supercritical CO2 and hot nitrogen, respectively, avoiding the oxidation of bioactive compounds. In addition, the coupling of PHWE with enzymatic reactions to hydrolyze flavonol glycosides has also been reported successfully (Lindahl et al., 2010; Lindahl, Liu, Khan, Nordberg Karlsson, & Turner, 2013). This process was shown to be a faster, more accurate, and greener method to achieve hydrolysis compared to conventional acidcatalyzed hydrolysis (Lindahl et al., 2010).

208

7.5

Green Food Processing Techniques

Hydrolysis reactions during pressurized hot water extraction

In the last few years, there is an interest to have valuable compounds from biopolymers (biomass) from plants, waste, and by-products from the agriculture or food industries. Water at high temperature changes its physical properties, such as its self-ionization and pH. Thus water has a lower pH and higher ion strength at high temperature, which originates that hydronium ions (H3O1) can act as catalysts in hydrolysis reactions (Plaza & Turner, 2015). The biopolymers (such as hemicellulose, cellulose, lignin, proteins, among others) may react with water at high temperature, being not necessary long reaction times and presenting high conversion rates (Rogalinski, Liu, Albrecht, & Brunner, 2008). The compounds produced are several and can be changed to a great extent by modifying processing conditions. For instance, Sereewatthanawut et al. (2008) investigated the production of value-added proteins and amino acids from deoiled rice bran by hydrolysis in subcritical water in the temperature range between 100 C and 220 C for 0
30 min. The results suggested that pressurized hot water could effectively be used to hydrolyze deoiled rice bran to produce useful proteins and amino acids. The amounts of protein and amino acids produced were higher than those obtained by conventional alkali hydrolysis. The yields generally increased with temperature and hydrolysis time. However, thermal degradation of the product was observed when hydrolysis was carried out at a higher temperature for an extended period of time. Therefore the highest yields of proteins and amino acids were obtained at 200 C for 30 min (Sereewatthanawut et al., 2008). Moreover, Rogalinski et al. (2008) investigated the hydrolysis kinetics of different kinds of biopolymers, such as starch, cellulose, and proteins, in a continuousflow reactor with water in subcritical conditions. They observed that hydrolysis kinetics in pressurized hot water enhanced with increasing temperature. Also, if the water is acidified with carbon dioxide, it led to a hydrolysis rate enhancement of the investigated substrate. The rate constants of the hydrolytic conversion were determined for the resulting monomers (glucose and amino acids), and the values were found to strongly depend on the type of bond. Peptide bonds in proteins exhibited a much higher stability compared to the ß-1,4- and ß-1,6-glycosidic linkages in cellulose and starch, respectively. Furthermore, the complex reaction behavior of the produced amino acids and their different thermal stabilities lead to the relatively low yields. However, they found that the produced glucose was unstable at high temperatures and different secondary degradations and isomerization products were detected, such as pyruvaldehyde, levoglucosan, and 5-hydroxymethylfurfural (HMF) (Rogalinski et al., 2008). Traditionally, lignin has been considered as a low-value by-product of the pulping industry. Nowadays, lignin has been suggested as a valuable source of chemicals if it would be broken into smaller molecular units (Cocero et al., 2018). For example, hydrothermal conversion of lignin was conducted in PHWE at subcritical temperature of 300 C
370 C and residence times of 0.5
10 s at a pressure of

Pressure hot water processing of food and natural products

209

25 MPa producing different phenolic compounds such as vanillin, catechol, guaiacol, eugenol, among others (Yong & Matsumura, 2013). Despite existing work achieved and its potential, the applications of pressure hot water technology to carry out hydrothermal reactions need to be studied in deep. A particular challenge is that hydrolysis conditions, rates, and yield of the produced compounds depend on the characteristics of the residues, composition, and structure of cell wall and the type of the monomer present in the biopolymer. As a result, the hydrolysis reaction by pressurized hot water should be studied individually for each raw material which represents a new technological challenge (Lachos-Pe´rez et al., 2017).

7.6

Food quality and safety using pressurized hot water extraction

The degradation of analytes (bioactive compounds) from natural sources at high temperatures is a generally found issue. Indeed, if the temperature increases above a particular value, different thermolabile compounds are lost. Therefore the degradation is an unwanted event consequence of the use of high temperatures, and different strategies should be applied in order to avoid this phenomenon. For instance, rapid temperature decrease after the extraction/hydrolysis reaction and/or employing dynamic extractions instead of static with a carefully selection of temperature and times may avoid the degradation of thermolabile compounds (Liu et al., 2014; Monrad, Srinivas, Howard, & King, 2012). Extraction and degradation processes are usually happening at the same time. Thus in order to select the best extraction conditions and to minimize degradation reactions, a deep study of extraction and degradation rates during PHWE is needed (Petersson, Liu, Sjoberg, Danielson, & Turner, 2010). There are different works in the literature aimed to study the degradation of products and kinetics of some analytes under PHWE. For instance, Khuwijitjaru, Suaylam, and Adachi (2014) investigated the degradation of the phenolic caffeic acid in pressurized hot water within the temperature range of 160 C
240 C following a first-order kinetics model. Caffeic acid degraded quickly at these high temperatures producing hydroxytyrosol, protocatechuic aldehyde, and 4-vinylcatechol. However, there are analytes such as benzoic acid that are more stable at high temperatures remaining stable at temperatures up to 300 C (Lindquist & Yang, 2011). However, the degradation of benzoic acid derivatives (anthranilic acid, salicylic acid, and syringic acid) increased with rising temperature, and the acids become less stable with longer heating times. They showed very mild degradation at 150 C, severe degradation at 200 C, and their complete degradation at 250 C (Lindquist & Yang, 2011). Anthranilic acid, salicylic acid, and syringic acid in high-temperature water underwent decarboxylation to form aniline, phenol, syringol, and benzene, respectively. There are phenolic compounds more sensitive to high temperature. For instance, the thermal degradation of the flavonoid quercetin was observed at

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Green Food Processing Techniques

temperatures greater than 100 C (Srinivas, King, Howard, & Monrad, 2010). Also, the degradation rate constants of silymarin (flavonoids mixture of taxifolin, silychristin, silidianin, silibinin, and isosilibinin) extracted from Silybum marianum ranged from 0.0104 min21 at 100 C for silychristin to a maximum of 0.0840 min21 at 160 C for silybin B (Duan et al., 2009). The degradation rates are different depending on the analyte under study, and it should be considered when PHWE is carried out. On the other hand, the natural extracts obtained from edible sources are usually considered as safe for human consumption, because these extracts are collected from natural matrices, and toxic organic solvents are not used in the process. However, this may not be necessarily the case since water is a strong source of hydronium (H3O1) and hydroxide (OH2) ion at high temperatures because the water dissociation constant (Kw) increases from 10 3 10214 at ambient temperature (25 C) to 4.9 3 10212 at 200 C (see Table 7.1) (Plaza & Turner, 2015). H3O1 and OH2 can catalyze reactions, including hydrolysis of polysaccharides and proteins into smaller molecules (i.e., oligosaccharides, monosaccharides, peptides, and amino acids) which are more sensitive to react with each other (Sereewatthanawut et al., 2008). For instance, it has been detected that Maillard, caramelization, and thermo-oxidation reactions may occur during PHWE in glycation model systems (Plaza, Amigo-Benavent, del Castillo, Iba´n˜ez, & Herrero, 2010a) and natural samples (Plaza, Amigo-Benavent, del Castillo, Iba´n˜ez, & Herrero, 2010b). As a consequence of these reactions, new compounds with different structures and chemical properties are formed that might entail some toxicity issues. Then, PHWE extracts proposed for human consumption as a food additive must be carefully studied not only in terms of bioactivity but also in toxicity terms. HMF is an intermediate compound formed through Maillard and/or caramelization reactions (Durling, Busk, & Hellman, 2009) and, therefore, is widely produced during food processing and storage, and also during cooking, being frequently found in foods rich in carbohydrate, such as dried fruits, bakery products, malt, fruit juices, coffee, among others. That is why HMF has been sometimes selected as an indicator for monitoring the heating processes in the food industry. The dietary intake of HMF is at the mg/kg level, far above than other food toxicants but more studies are required in order to determine average, medium, and maximum intake for different populations and sections of the population. In any case, its presence in food has generated concerns on its safety and toxicology. HMF is considered as probably or potentially carcinogenic to humans or might be metabolized by humans to potentially carcinogenic compounds (Capuano & Fogliano, 2011). For example, HMF is known to be converted in vivo to 5-sulfooxymethyl furfural which is a genotoxic compound (Capuano & Fogliano, 2011). At high temperatures and pressures, decomposition of oligosaccharides and polysaccharides might happen so natural products, food, and food by-products, which have high amount of inulin, hemicellulose, cellulose, lignin, fructose, glucose, sucrose, and also other carbonyl groups as polyphenols and ascorbic acid, are potential sources for the formation of HMF during PHWE (Hata, Wiboonsirikul, Maeda, Kimura, & Adachi, 2008; Pourali, Asghari, & Yoshida, 2010). It has been

Pressure hot water processing of food and natural products

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shown that the extraction temperature is one of the most important parameters affecting HMF formation during PHWE, but extraction time is also a critical parameter to take into consideration (Kanmaz, 2018). Different studies have shown that HMF formation happens at high extraction temperatures (c.200 C) during PHWE of apple by-products (Plaza et al., 2013), grape pomace (Mariotti-Celis et al., 2018; VergaraSalinas, Vergara, Altamirano, Gonzalez, & Pe´rez-Correa, 2015), pistachio hulls (Ersan, Guclu Ustundag, Carle, & Scheweiggert, 2018), olive leaves (Herrero, Castro-Puyana, et al., 2012), and cocoa shells (Jokic, Gagic, Knez, Subaric, & Skerget, 2018). There are specific researches aimed to monitor the formation of HMF using a wide range of temperatures (from 25 C
50 C to 200 C) during PHWE of bioactive compounds from olive leaves (Herrero, Castro-Puyana, et al., 2012) and apple by-products (Plaza et al., 2013). Both works enabled to conclude that HMF was only formed at extraction temperatures higher than 112 C
125 C, and its concentration in the extracts strongly increased above 175 C, being maximum at the highest tested temperature of 200 C. In addition, the formation of furfural, other indicator of Maillard reaction, was studied during PHWE of apple by-products (Plaza et al., 2013) observing the same tendency than for HMF. Furfural was detected at temperatures of 112 C and substantially increased along with higher temperatures. In addition, in order to optimize the extraction of flavonols in apple by-products and minimize the formation of unwanted compounds derived from Maillard and/or caramelization reactions, Plaza et al. (2013) used a desirability function response surface, considering maximum antioxidant capacity and minimal formation of brown color, giving an optimum of 125 C and 3 min. These extraction conditions correlated well with the obtained optimal extraction conditions to get the highest amount of flavonols (120 C and 3 min), thus a desirability function is a good method for finding optimal extraction conditions minimaxing the formation of unwanted compounds during the extraction (Plaza et al., 2013). Therefore the higher the temperature, the more unwanted compounds, so-called contaminants, will be extracted, leading to lower selectivity and increasing the need for further cleanup steps after PHWE. For example, Mariotti-Celis et al. (2018) employed an integrated process of hot pressurized liquid extraction-resin purification (RP) in order to obtain a purified polyphenol extract from Vitis vinifera pomace, free of reducing sugars, and HMF. They achieved extracts free from HMF and reducing sugars and with similar polyphenol content and proanthocyanidins oligomeric distribution as those obtained using conventional maceration and RP with acetone, without significantly reducing the yields of polyphenols (Mariotti-Celis et al., 2018). On the other hand, Vergara-Salinas et al. (2015) characterized two PHWE extracts from grape pomace obtained at 100 C and 200 C. The HPLC chromatogram of the extracts obtained at 200 C, measured at 280, 365, and 320 nm, showed peaks that could not be found in the chromatogram obtained with the extracts at 100 C (see Fig. 7.5). These peaks might correspond to either compounds formed by thermal degradation or other reactions or new compounds extracted from the sample leading to lower selectivity of the extraction method. It is generally difficult to be sure which compounds are native from the natural matrix and which are artifacts (Liu et al., 2014; Petersson et al., 2010).

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Figure 7.5 The chromatograms of the extracts from grape pomace obtained by PHWE at 100 C (GPE100, left) and 200 C (GPE200, right), at different wavelengths evidences of their different profile due to the different extraction conditions. PHWE, Pressurized hot water extraction. Source: Reprinted with permission from Vergara-Salinas, J. R., Vergara, M., Altamirano, C., Gonza´lez, A., & Pe´rez-Correa, J. R. (2015). Characterization of pressurized hot water extracts of grape pomace: Chemical and biological antioxidant activity. Food Chemistry, 171, 62
69.

Besides the effects of extraction temperature (50 C
200 C), the effect of extraction time (5
45 min) and the material type (artichoke leaves, lemon peel, and flaxseed meal) on the formation of HMF during static PHWE were studied (Kanmaz, 2018). The effect of temperature in the presence of HMF in PHWE extracts was similar to the works described earlier. However, the effect of time revealed that HMF formation could increase from 1.4 to 4.5 times from 15 to 45 min at 180 C.

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Also, the matrix affected the extraction being the optimal conditions for the formation of HMF in lemon peel and artichoke leaves at 180 C and 45 min while in flaxseed meal were 200 C and 15 min (Kanmaz, 2018). However, Jokic et al. (2018) observed that the concentration of HMF and furfural in PHWE extracts of cocoa shells obtained at 220 C for 15 min was maximal. However, at higher temperatures than 220 C and longer extraction times, the concentration of HMF and furfural decreased, and the main products present on the extracts were organic acids (such as levulinic, lactic, and formic acid) obtained from HMF. Therefore other parameters to take into account besides the temperature in order to minimize the formation of HMF in PHWE are the time and the type of matrix. In summary, regarding food quality and safety, the aspects described earlier should be closely studied in each case, because they will strongly depend on the matrix extracted, as well as the PHWE conditions used. In any case, a toxic effect on the health of these neoformed compounds cannot be completely discarded.

7.7

Environmental impact

Certainly, there are many aspects to take into account for claiming the “greenness” or “sustainability” of an extraction process, including the amount of waste generated, toxicity and environmental concern of all chemicals used, energy and electricity used in the extraction process, as well as in the production of the chemicals, and the safety of the extraction method (Castro-Puyana, Mendiola, Iba´n˜ez, 2013b). Thus in order to consider PHWE as a “green” or “sustainable” extraction process, data on true environmental impact should be calculated based on good input data (Turner, 2013). Then, tools, such as the Environmental, Health, and Safety performance factor (EHS) and life cycle assessment (LCA), are needed to assess the environmental sustainability of an extraction process (Capello, Fisher, & Hungerbu¨hler, 2007; Pennington et al., 2004). EHS method is focused on the identification of potential hazards of chemicals, whereas LCA takes into account the environmental impact of a process during all life cycle (e.g., from harvesting of raw material to the disposal of solvent). One of the main advantages of LCA compared to other, more simplified methods for the calculation of environmental impact is that a more accurate picture is presented. Then, a LCA of the all extraction process should be required to declare that “PHWE is more sustainable than other extraction process employing an organic solvent.” For instance, water is claimed as the greenest solvent because it is safe to health and environment and to work with, besides, its transportation is achieved by an already built infrastructure, which implies that water has a minimum environmental effect (Castro-Puyana et al., 2017). Furthermore, in terms of extraction processes, it is not needed to carry out the pretreatment of drying the raw material before the extraction. However, cleanup and/or concentration steps could be needed to be implemented in the extracts. These steps will require energy and therefore the extraction process will have a great environmental impact. Therefore more studies such as LCA should be conducted to

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calculate energy usage, raw data input, and release to air and water during an extraction process. Even if the metric tools described earlier give the greenness of the solvents used in an extraction process, they are scarcely used. There are only two works in the literature which showed from a life cycle point of view how good is PHWE for the environment (Ekman et al., 2013; Rodrı´guez-Meizoso et al., 2012). Real measurements of the environmental impact of extraction process are needed in order to select the best extraction process.

7.8

Conclusions and future trends

In this chapter, it is shown that water at high temperature and pressure is an attractive solvent, increasing mass transfer and the solubility of many interesting compounds from plants, foods, and food by-products. However, there is no available commercial analytical PHWE system. For instance, there are commercial pressurized liquid extraction systems that they are developed for the extraction with organic solvents. In order to carry out PHWE, the instrument should be built with high-quality steel alloy and improve preheating of the solvent as well as the possibility that temperature and pressure range going close to the critical point of water (374 C and 22.1 MPa). On the other hand, there is a PHWE system available at preparative scale, which was designed to achieve temperatures up to 300 C and flow rates of 100 mL/min. Nevertheless, there are some issues such as the risk of clogging of tubing because of caramelization reactions as well as the need for an appropriate degassing system for water required to be addressed in commercial PHWE systems. There are no industrial systems because of the need for more economic studies, but nowadays an effort is being made in their development. Taking into account the applications discussed in this chapter, it is envisioned that the new trend is to develop new platforms able to perform from a sustainable environmental point of view different operation steps, such as pretreatments
extractions
reactions
transformations, in a more integrated way. For instance the development of processes that combine PHWE with particle formation to obtain dry extracts or with enzymatic reactions to carry out catalysis. Other trend is to combine extraction with cleanup to improve the selectivity on the process by adding selective sorbent materials in the extraction cell. In addition, there is an increased interest still no studied in depth to obtain high-valuable compounds from biomass by using environmentally sustainable techniques such as PHWE. There are different drawbacks that can be associated to PHWE, mainly in terms of degradation of thermolabile compounds and/or associated reactions that can take place at elevated temperatures. These drawbacks should be considered at the time of optimizing a PHWE process because they can affect different issues related to food quality and safety. In addition, the environmental impact assessment should be studied. For example, LCA should be conducted in order to claim that PHWE is more sustainable than other extraction process employing an organic solvent.

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Acknowledgments Authors thank financial support from the Comunidad of Madrid (Spain) and European funding from FEDER program (project S2013/ABI-3028, AVANSECAL-CM). M.C.P. thanks the Spanish Ministry of Economy and Competitiveness (MINECO) for her “Ramo´n y Cajal” contract (RYC-2013-12688). M.P. thanks the University of Alcala´ for her postdoctoral contract.

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127.

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

8

Cherif Jablaoui1,2, Amal Zeaiter1,3, Kamel Bouallegue1,4, Bassam Jemoussi5, Colette Besombes1, Tamara Allaf6 and Karim Allaf1 1 Laboratory of Engineering Science for Environment LaSIE—UMR-CNRS 7356, University of La Rochelle, La Rochelle, France, 2National Agronomic Institute of Tunisia (INAT), University of Carthage, Tunis, Tunisia, 3Doctoral School of Science and Technology, Lebanese University, Beirut, Lebanon, 4University of Gabes, Gabe`s, Tunisia, 5 Laboratory of Supramolecular Chemistry ISEFC, University Virtual-Tunisia, Tunis, Tunisia, 6 ABCAR-DIC Process, La Rochelle, France

8.1

Introduction

Extraction is one of the most common unit operations used in food and pharmaceutical industries to recover and purify plant-based ingredients, such as edible oil, phytochemicals, flavors, and fragrances (Liu, 2012). Conventional extraction processes are based on the use of a suitable solvent to dissolve and remove the desired compounds from the interior of the plant tissues. The yields and kinetics of extraction depend on several factors such as the nature of the solvent (Hensarling & Jacks, 1983), the particle size, properties, and structure (Kadi, Meziane, & Lamrous, 2006), and the operative conditions such as pressure and temperature (Ferna´ndez, Perez, Crapiste, & Nolasco, 2012). The most widely used solvent for extracting edible oils from vegetable sources is hexane, which is highly available at low cost, with low boiling temperature, which facilitates its separation from oil and its recovery (Serrato, 1981).

8.2

Phenomenological analysis and intensification ways of solvent extraction process

Numerous empiric models have been used to examine both ratio and kinetics of extraction. They usually permit to explore the scaling-up but without extending the analyses toward a fundamental identification of the processes and boundaries. Conversely, phenomenological modeling has the advantage to recognize the specific processes at different conditions and identify the transfer resistance of each Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00008-2 © 2019 Elsevier Inc. All rights reserved.

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operation at each step. By addressing the highest resistance, the intensification may be performed for improving the whole unit operation. In the specific cases of solvent extraction (SE), phenomenological modeling is mainly achieved through an effective comparison between the external interaction and the internal transfers. Indeed, the operation begins by the solvent interacting with the specific ingredient at the sample surface. This “washing/starting accessibility” stage mainly depends on the mass convection, which is function of the relative velocity, viscosity, dissolubility, and saturation level of the concerned ingredient, etc. It normally produces a gradient within the grain between the core and the surface usually resulting in adequate internal diffusion of both solvent and the ingredient it dissolves. This initial “washing” stage is normally characterized by its rapidity and short duration, starting at the beginning of process (Bouallegue, Allaf, Besombes, Younes, & Allaf, 2015). The second diffusional phase due to the oil concentration gradient behaves the solvent penetration to the depth of the particles, desolventation, and diffusion. It should normally be a slow phase according to a diffusional mechanism and some studies describe it as coupled washing/diffusion (CWD) phenomenological model. For adequate agitation of the solvent through a mechanical way (dynamic maceration) and/or specific ultrasound (US) agitation within the surrounding medium, and far from the saturation level of dissolving, the whole operation would usually be characterized by a negligible external resistance (NER), and the extraction kinetics should reveal and be revealed by the internal diffusion process. Thus the first process intensification should concern some macroscopic pretreatments of the plant-based material such as grinding/crushing of the grains in order to increase the interaction surface and reduce the internal diffusion distance. It is worth noticing that such a “pretreatment” does not imply notable nor significant internal diffusivity. The most widespread way to increase the diffusivity is to use its well-known correlation with temperature. Indeed, from the properly said definition of temperature as the average density of kinetic energy of the translational isotropic random microagitation, the thermal microagitation is the principal reason that causes the liquid/solid or liquid/liquid diffusion interaction. The higher the temperature and, thus, the higher the microscopic translational random microagitation, the higher the diffusivity. Arrhenius-type normally leads to identify the activation-energy of this correlation. However, the boiling temperature and the thermal degradation possibly triggered during the operation practically constraint a highest temperature level of the extraction process. Recently, since 1998, another means of increasing diffusion during a SE process has been associated with appropriate macroscopic texturing using instant controlled pressure drop (DIC). This results in greater porosity and better tortuosity of the new textured matrix with a perfectly controlled generation of broken-wall cells. The SE process then becomes more efficient both in terms of yields and kinetics, with greater starting accessibility δYs and higher effective diffusion Deff. A microwave treatment (Rombaut, Tixier, Bily, & Chemat, 2014) during the extraction can bring some broken-wall cells, as well as the cavitation produced by US-assisted SE (Pan, Qu, Ma, Atungulu, & McHugh, 2011). Since US has the

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specificity to allow the interaction between waves and the material to increase the agitation of the material pores, the solute motion within solvent in each full-insolvent-pore does not become limited to the Fick-type diffusion but performed by a possible solute mass convection; this greatly contributes increasing the effective diffusivity (Mason, 1996). DIC texturing involves a high-temperature/short-time (HTST) treatment of the product prior to an abrupt pressure drop (decompression) toward a vacuum (Ben Amor & Allaf, 2009). It systematically results in an autovaporization possibly leading to a controlled expansion that grants the refinement of the matrix microstructure. Hence, the technological aptitude of DIC-treated plants versus numerous transformation operations (drying, extraction, chemical, enzymatic transformations, etc.) is generally enhanced through the solid
fluid interaction. Moreover, since DIC is a HTST thermal treatment generally performed at a treatment pressure of the saturated-dry steam usually limited at 400
800 kPa, ending by a final vacuum level of 4
5 kPa as absolute pressure, an instant cooling is achieved toward a final product temperature lower than 33 C. Expander and extrusion also use a flash depressurization from the same level of treatment steam pressure but ending by an atmospheric pressure, which means a final temperature of 100 C. Thus DIC is distinguished by much less severe conditions, while allowing much greater amount of autovaporized water. Indeed, as defined by (Allaf and Allaf, 2014), the DIC generates by autovaporization a quantity of vapor much higher than expander or extruder:    md cp;d 1 Wcp;H2 O Tt 2 Tf mv 5 L

(8.1)

where md is the mass of the dry material, while cp,d and cp;H2 O are the specific heats of the dry material and the water, respectively. W is the dry water content, while Tt and Tf are the treatment temperature and the final equilibrium temperature after depressurization, respectively. The difference in temperature just before and right after the pressure drop reflects the amount of vapor produced. It is for the expander and DIC 150 C 2 100 C 5 50 C and 150 C 2 33 C 5 117 C, respectively. Thus a similar report must be acquired for the amounts of vapor generated. Consequently, for an initial humidity of 10% and specific heats of 1.2 kJ/kg/K for the dry matter and 4.18 kJ/kg/K for water, the generated vapor by expander, puffing, or extrusion is 3.6 against 8.4 g vapor/100 g dry basis (db) for DIC. Thus compared to expander, the DIC generates 235% more vapor; the expansion ratio and porosity should become twice higher when the seeds are textured by DIC than by expander. Thus compared to expanding and puffing/extrusion, DIC is the most effective texturing operation while it is capable of preserving the molecular profile of compounds, even for numerous heat-sensitive ingredients. By achieving expanded plant materials, the interaction surface between the product and the fluid increases. Such coupled high porosity and tortuosity result in higher effective diffusivity. Besides, depending on the treatment conditions, DIC can be

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controlled to induce perfectly controlled broken cell walls; this may imply greater ingredient availability and thus possibly higher extraction yields. Since the two operations of DIC as a pretreatment texturing way and US assisting the properly said extraction process from the porous material are both particularly simple from technical point of view without real strains at industrial level and/or economic limitations, it has been worth analyzing the combination of their contribution at laboratory, pilot, and industrial scales. One of the most interesting queries to seek would be to identify the possibility of a synergistic DIC/US mixture to, consequently, allow the researchers and engineers to adjust the extraction procedures to fulfill the best strategic conditions. Based on these studies, we assumed that a coupling between an DIC texturing and a US-assisted extraction should synergistically improve SE. The objective of this study was to verify this hypothesis by determining the influence on extraction kinetics such as the effective diffusivity Deff (m2/s) and the starting accessibility δYs (g oil/g db), determined using the phenomenological CWD modeling for NER extraction conditions.

8.3

Material and method

8.3.1 Raw material 8.3.1.1 Sunflower: two types or varieties Two varieties of sunflower (linoleic and oleic) were supplied by Presse de Gascogne (LA CHICOUE 32430 COLOGNE, France). Some part of these grains was hulled (or husked), and sequentially, their humidity was adjusted at about 6% using a drying airflow of 40 C and 3 m/s. Their oil content was measured using the n-hexane Randall method (55 C for 6 h). Yields, quality, and kinetic parameters of n-hexane extraction by dynamic maceration were a comparative study, which was achieved between an untextured and DIC-textured grains submitted to a conventional dynamic maceration and a USassisted operation. The impact was then determined through a comparative study of yields and quality of the oil extracted, and kinetic parameters at negligible external resistance NER conditions. After an adequate optimization of DIC texturing, saturated-dry steam pressure was 700 kPa for 85 s and 540 kPa for 85 s for linoleic and oleic, respectively.

8.3.1.2 Soybean Various samples of American soybeans were supplied by Carthage Grain. These grains were sequentially exposed to crushing, flattening, and expanding, and systematically, their humidity was adjusted at about 11% using a drying airflow of 40 C and 3 m/s. The soy oil content was assessed by the n-hexane Randall method at 55 C for 6 h. The DIC treatment conditions of cracked, flaked, and expanded soybeans were 550 kPa for 120 s, 490 kPa for 96 s, and 200 kPa for 20 s, respectively.

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

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A comparative study of solvent oil extraction was achieved between these industrially cracked, flaked, and expanded soybeans, and the DIC-textured beans submitted all to a conventional dynamic maceration and a US-assisted operation. The impact was then defined through yields and kinetic parameters for NER conditions, as well as the quality of the extracted oil.

8.3.1.3 Rapeseed pressing cake The two varieties of rapeseed had similar moisture content of about 10%
12% and oil content of 0.4356 and 0.4252 g oil/g db were provided by the Tunisian Company Carthage Grains. The optimized DIC factors for both varieties Jura and Pioneer were the saturated-dry steam pressure of 700 kPa for 65 s and for 120 s, respectively, the rapeseeds were dried in an airflow at 45 C and 0.3 m/s to reach a moisture content of about 6%. Subsequently, all the treated samples underwent an oil cold-pressing extraction. The oil cake was subsequently subjected to a solvent (n-hexane) extraction operation. A comparative study was achieved between a conventional dynamic maceration and a US-assisted operation, both performed with untextured raw material and DIC-textured material. The comparative study was detailed in terms of yields and quality of the oil extracted, as well as kinetic parameters.

8.3.2 Phenomenological approach of solvent extraction procedure From a technological point of view, processes of extraction and separation/refining by solvent are based on the dissolution of a specific molecule. The solvent must be defined according to the solute (polarity . . .). On the other hand, when the SE relates to a structured (porous) material, the motion of the solvent (liquid) in the solid material has the main purpose of carrying with it one or more compounds or molecules. Depending on these properties, the solvent is capable of dissolving the molecules that promote their extraction by forming the solvent
solute complex. During extraction, when the process is performed under Negligible External Resistance (NER) conditions, the extraction rate (1) starts depending on the interaction between the solvent and the external surface, and (2) is continued by diffusion of the solvent within the solid porous matrix and/or solvent
solute complex as a function of the driving force of a concentration gradient inside the solid, reaching the exchange surface and vanishing within the surrounding medium by diffusion or by mass convection (e.g., dynamic maceration).

8.3.2.1 Basis of the coupled washing/diffusion phenomenological kinetic model The extraction kinetics generally expresses the amount of extracted molecule expressed in g/g db as a function of extraction time or per unit of time Y 5 f(t).

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Green Food Processing Techniques

The specific study of vegetable oil extraction by n-hexane in Negligible External Resistance (NER) conditions allows determining the solvent
solute diffusivity from experimental data. This requires removing the data related to the short duration initial phase of interaction between the particle surfaces and the solvent relative to the starting accessibility δYs expressed in (g oil/g db) (Ferna´ndez et al., 2012). Then, in the second phase, since the highest resistance of the SE turns out to be correlated and limited by the solvent/solute diffusion within the solid matrix, with an overall transfer driving force of the solute concentration gradient can follow Fick law with an effective diffusivity Deff (m2/s) as described in the phenomenological modeling defined by (Ben Amor & Allaf, 2009). The most general function revealing the Fick law is done by Mounir, Allaf, Berka, Hassani, and Allaf (2014):
 ρs ~ ρs ð~ v m Þ 5 2 Deff r vs 2 ~ ρm ρf

(8.2)

where ρs , apparent density of solvent/solute (kg/m3); ρm , apparent density of the solid matrix of the porous medium (kg/m3); ~ v s , absolute average velocity of the solvent in the solid matrix of the porous medium (m/s); ~ v m , absolute mean velocity of the solid matrix (m/s); Deff , effective diffusivity of the solvent in the solid matrix of the porous medium (m2 /s). Deff is a function of the solvent properties and temperature and also of particle shape and size, and structural characteristics (porosity, tortuosity, etc.). Deff can be assumed as a constant for the whole extraction process only when we can assume the homogeneity of structure and temperature, and when there is no changing in shape and/or size, structure, porosity, tortuosity, shrinkage, breaking of cell walls, etc. during this unit operation process: (Deff 5 constant, vm 5 0, and ρm 5 constant): ~ s ρs~ v s 5 2 Deff rρ

(8.3)

conservation of mass and continuity lead to the establishment of a relationship of Fick’s law
type concentration versus time:   @ρs ~  ~ ρs 5 r Deff r @t

(8.4)

and, by embedding the effective diffusivity Deff as a constant (Mounir & Allaf, 2008), Eq. (8.4) becomes    @ρs ~ ρs ~ r 5 Deff r @t

(8.5)

The standard Crank solutions depend on the form (spherical, cylindrical, plate, etc.); it allows defining from the part of concerned experimental data, the effective diffusivity Deff (m2 /s) (Paiva, 1972). Indeed, the most known procedure is

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

227

1. To get t0 as a time value selected as a time value able to be considered as incontestably belonging to the stage for what the SE is limited by the diffusion  process. 2. To compute the experimental values of ðYlim 2 Y Þ= Ylim 2 Yt0 versus (t 2 t0) where Y is the oil yield at time t; Ylim is the maximum oil yield reached when t ! tN; Yt0 is the oil yield at t 5 t0.

For a relevant use of the CWD model to determine the values of δYs and Deff, it is advisable to follow the following five-C method: 1. To check the validity of the assumptions admitting Deff as a constant, 2. To concept analytical or numerical solutions of the differential diffusion equation [Eq. (8.4) or Eq. (8.5)], 3. To compare the difference between the modeled CWD values and the experimental results (by decreasing the extraction time from the reference point t0 till the origin t 5 0, the CWD model should deviate more and more from the experimental values), 4. To consider the theoretical value Y0 of the calculated yield at the origin of time t 5 0 via the diffusion model CWD, 5. To compute the initial accessibility, δYs (g oil/g db) is the difference between Y0 and the initial yield Yini at (t 5 0); δYs is obviously calculated as:

δYs 5 Yo 2 Yi 5 Y0

(8.6)

8.3.2.2 Intensification methodology and experimental Protocol The current research work was to study and compare the two types of intensification ways of the vegetable oil extraction in the cases of three oleaginous grains. They are (1) the structural pretreatment mainly performed by DIC, and (2) the impact of US on the mass transfer of the properly said SE. The study aimed at defining the most general integration of DIC texturing followed by extraction by dynamic maceration assisted or not by US. As illustrated in Fig. 8.1 our scientific study was based on comparing the oil extraction yields Ylim and kinetic parameters of effective diffusivity Deff and starting accessibility δYs, issued from the phenomenological CWD model. Indeed, Zhang et al. (2008) have mentioned a significant improvement of yields and kinetics by inserting US-assisted SE. They accorded the reasons of this behavior to the cavitation and also the agitation the US can bring within the material (Zhang et al., 2008). Separately, Mounir and Allaf (2014) have proven the ability of DIC texturing to cause significant impacts on the technological ability of plant-based materials versus SE. The case of oleaginous grains versus oil extraction has a particularly high technological and economic impacts. By increasing both porosity and tortuosity, as well as possibly getting higher number of broken-wall cells, DIC was able to significantly increase availability and extraction rate, through greater yields, diffusivity, and starting accessibility (Mounir, Schuck, & Allaf, 2010). Here, the three types of oleaginous materials were used in order to establish a general comparative study of

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Green Food Processing Techniques

Cracked;flaked; and/or expanded

Un textured

Sunflower seeds linoleic or oleic

Rapeseed Jura or Pioneer

Soybeans

DIC

Un textured

textured

Coldpressing cake

DIC textured

First Coldpress oil

Un textured

DIC textured

Grinded

SE

HPLC;GC analyses

US-SE

Solvent extracted

Oil

Statistic Analyses of yields and kinetics

Figure 8.1 Diagram of experimental protocol of the current study including soybean, sunflower, and rapeseed oil extraction mainly using DIC texturing and/or US-assisted SE (US-SE) as intensification ways. DIC, Instant controlled pressure drop; SE, solvent extraction; US, ultrasound. 1. the effect of materials with different oleaginous grains of cracked, flaked, and expanded pretreated soybeans, raw sunflower seeds, and cold-pressing cake of rapeseeds versus conventional SE (CSE), 2. the effect of DIC texturing as a structural pretreatment of SE, 3. the effect of a simple conventional US-SE, 4. the effect of coupling the DIC pretreatment with US-assisted SE.

The amounts of yields and kinetic parameters were considered as basis of the process performance of this comparison. On the other hand, the comparison study of these different intensification ways of extraction has also concerned the extracted oil quality. This was performed by chromatographic analysis to determine the fatty acid profiles and the tocopherol content.

8.3.3 Main intensification ways 8.3.3.1 Instant controlled pressure drop technology The DIC technology has been defined, patented, and developed by Allaf, Louka, Parent, Bouvier, and Forget (1999). This technology is well known based on a fundamental study of expansion and has targeted huge number of industrial applications in response to issues of controlling and improving quality, coupled with

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

229

Instant opening– largesection valve Lowtemperature air compressor

Treatment vessel

Saturated dry steam generator

Steam trap

Large-volume vacuum tank

Water-ring vacuum pump

Figure 8.2 Schematic diagram of DIC laboratory-scale unit: (A) treatment vessel; (B) vacuum tank; (C) large-section instant opening valve; (D) water-ring vacuum pump; (E) Saturated steam generator with condensed water trap. DIC, Instant controlled pressure drop.

higher process performance revealed through the yield, the kinetics, and the reduction of energy costs. The DIC unit used in our study (Fig. 8.2) was a laboratorytype facility (Medium Pressure MP-DIC unit), which is characterized, as any DIC unit, by a very fast connection (in some 20 ms) between the reduced-volume treatment vessel and a (100
130 times greater volume) vacuum tank. DIC treatment is a HTST (up to 160 C, during some tens of seconds) followed by an instant pressure drop toward the vacuum (about 5 kPa), which causes autovaporization and product cooling. The abrupt pressure drop can induce a whole swelling of the product and a possible controlled destruction of cell walls; other volatile compounds can also be released. During the exceptionally short time of pressure drop (dozens of milliseconds), the thermodynamics of instantaneity should elucidate this process greatly; the anisotropic translational random microagitation should greatly contribute to the abrupt cooling, modify the glass transition, and improve the phase separation (Figs. 8.3 and 8.4).

8.3.3.2 Ultrasound-assisted solvent extraction 8.3.3.2.1 Physical parameters Ultrasonic US treatment involves subjecting a material to the effect of mechanic wave acting on liquid or possibly gas medium, generally at frequencies above 20 kHz for a definite period of time. Usually, the intensity of the US wave defines two sectors of ultrasonic applications: 1. Low intensity or else called diagnostic US assessment: It is largely used as analytical techniques in the medical field, with frequencies exceeding 100 kHz and a generated energy lower than 1 W/cm2.

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Green Food Processing Techniques

DIC treatment

Expanding treatment

Temperature level of heating by saturated dry steam (°C)

125

175

Treatment temperaure 100 to 170°C

150

Treatment pressure 0.6 MPa

100 D

B 75 50

Temperature drop due to the pressure drop

Temperature level of heating by saturated dry steam (°C)

C

25 Ambient temperature

Equilibrium temperature at the vacuum pressure of 3–5 kPa

Treatment pressure 0.6 MPa

125

D’

100 B

Equilibrium temperature After pressure-drop

75 E’ 50

Cooling stage from 100°C towards the ambient temperature

25 Ambient temperature

E

A 0

C Treatment temperaure 100 to 240°C

150

Temperature drop due to the pressuredrop

175

A 0

Time (s)

Time (s)

Sunflower linoleic seeds

Sunflower oleic seeds

Soybeans (cracked)

Soybeans (cracked/flaked/ expanded)

Rapeseed Jura pressing meal

Yields: 16.33g oil/g db; 113%

Yields: 15.93g oil/g db; 110%

Yields: 15.12g oil/g db; 105%

Yields: 14.76g oil/g db; 100%

Yields: 16.67g oil/g db; 112%

Yields: 15.89g oil/g db; 107%

Yields: 15.62g oil/g db; 103%

Yields: 1485g oil/g db; 100%

Yields: 24.94g oil/g db; 120%

Yields: 23.48g oil/g db; 113%

Yields: 24.64g oil/g db; 119%

Yields: 22.43g oil/g db; 108%

Yields: 23.98g oil/g db; 116%

Soybeans (cracked/flaked)

Yields: 24.64g oil/g db; 119%

Yields: 22.52g oil/g db; 109%

Yields: 21.25g oil/g db; 103%

Yields: 24.29g oil/g db; 117%

Yields: 22.47g oil/g db; 108%

Yields: 23.51g oil/g db; 113%

Yields: 20.71g oil/g db; 100%

Yields: 48.84g oil/g db; 117%

Yields: 46.99g oil/g db; 113%

Yields: 45.24g oil/g db; 108%

Yields: 41.74g oil/g db; 100%

Yields: 49.41g oil/gdb; 119%

Yields: 46.44g oil/g db; 112%

Yields: 41.52g oil/g db; 100%

Yields: 44.89g oil/g db; 108%

Figure 8.3 Different stages of DIC and expanding treatments: (A) to place the product in treatment vessel, at atmospheric pressure, and establishing a first vacuum stage for expanding and DIC, respectively; (B) to inject saturated-dry steam increasing pressure and temperature till the treatment level; (C) to maintain the high pressure/high temperature for dozens of seconds; (D) to abruptly drop the pressure toward a vacuum (3
5 kPa) for DIC and toward atmospheric pressure; for expanding, (E) to release the system from the vacuum toward the atmosphere pressure (for DIC) and to perform a cooling stage from 100 C toward an almost ambient temperature, for expanding. DIC, Instant controlled pressure drop.

Rapeseed pioneer pressing meal

Figure 8.4 Compared effects of various oleaginous materials versus different intensification of n-hexane SE processes, which are the CSE, US-SE, DIC-SE, and DIC-US-SE. CSE, Conventional solvent extraction; DIC-SE, instant controlled pressure drop pretreatment solvent extraction; DIC-US-SE, instant controlled pressure drop pretreatment ultrasoundassisted solvent extraction; SE, solvent extraction; US-SE, ultrasound-assisted solvent extraction. 2. Power US: Its frequencies must be below 100 kHz with a specific energy greater than 10 W/cm2. A wide range of these US applications affect the processed material by generating a huge cavitation impacts and/or a simple effective agitation (Mason, 1997).

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231

8.3.3.3 Ultrasound techniques for extraction US-SE was performed by a CPX3800H series US model, equipped with an automatic adjustment of all the parameters, such as the temperature which can reach 69 C, the treatment time up to 99 min and the frequencies of about 40 kHz; the power was selected to be 150 W, which means 3.6 W/g of the mixture solvent and seeds-in-solvent (Rombaut, Tixier, Bily, & Chemat, 2018).

8.3.4 Assessments and characterization 8.3.4.1 Measure of moisture content To determine the moisture content of the material, cups of 2
3 g are placed in an oven at a temperature of 105 C for 24 h (weight stabilization). Moisture is expressed in g H2O/g db. For convenience, these measurements were duplicated with an infrared analyzer (Mettler Toledo LP-16 IR Dryer/Moisture Analyzer with Mettler Toledo PE360 Balance—Bishop International Akron, OH-USA).

8.3.4.2 Randall extraction The dosage of oil of various oleaginous samples was carried out by Randall (velp-148) extraction technique. After milling, 3 g of powder was placed in a 30 3 80 mm cellulose cartridge. An amount of 40 mL of n-hexane was placed in the extraction chamber where the solvent temperature was kept almost constant at 55 C for 6 h. The system implies continuous washing cycles excluding the immersion phase and is related to a condensation recovery system. The oil yields were expressed in g oil/g db:   Mass of extracted oil Y g oil=g db 5 Mass of dry matterðdbÞ

(8.12)

8.3.4.3 Dynamic maceration A quantity of 3 g of powder was placed in a 100-mL vial with 40 mL of n-hexane. The flasks were placed in a bath with a stirring system of 200 rpm and a temperature of 55 C. For each sample the solution was filtered using PTFE filters (0.2 μm), and the solvent was evaporated by injecting a nitrogen stream at 40 C.

8.3.4.4 Sieving instrument Sieving was achieved in a vibratory sieve shaker Analysette 3 Pro from C2M technology (Florange, France) for the coarse grinding with sieves of 2000
1400
1000
800
600
200
71 μm, and the fine grinding of 800
600
560
400
280
200
140
100
71 μm. The vibration amplitude of sieving was fixed at 1.2 mm.

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8.3.4.5 Gas chromatography conditions The different portions of free fatty acids were determined by an Agile gas phase chromatography 19091S-433 (Kyoto, Japan) equipped with a column (HP-5MS 30 m 3 350 μm 3 0.25 μm). The oven temperature was set to increase from 155 C to 230 C with a rhythm of 45 C/min. The final phase was defined by a temperature stabilized at 240 C for 50 min. The mobile phase (the carrying gas) was helium flux with a speed of 37 cm/s. A total of 15 μL of oil samples were put in a vial with 20 μL 2,3,5-trimethylhydroquinone (TMH) and 1 mL of methanol
chloroform solution (50/50). Split mode (1/200) was set up automatically to inject 1 μL of each sample. The fatty acids were identified from their peaks using the internal program library, while their concentration ratios were calculated by integrating the correspondent peaks.

8.3.4.6 Liquid chromatography analysis For liquid chromatography assessment, a Shimadzu system was used equipped with two distribution pumps (LC-10AD), an Altimma RPC-18 separation column (250 3 4.6 mm 5 μm Associates Inc.), a FL/FR-10AXL detector and an automatic injector (25 μL/samples). An acetonitrile/methanol solution (75/25) was the mobile phase, which was injected at a flow rate of 1 mL/min. The column temperature stabilized at 250 C and the fluorescence detector set at 298 nm for excitation and 344 nm for emission wave. Total separation time was 40 min. Retention times and the calibration range of the standard α, β, and γ were used for the identification and determination of the different concentrations of tocopherol fractions.

8.4

Results and discussion

8.4.1 Oil yields issued from differently assisted operations of solvent extraction With the objective of comparing the impacts of the differently intensified n-hexane SE processes, which are the CSE, US-SE, DIC pretreatment (DIC-SE), and DICUS-SE, each oleaginous was studied with the same conditions of grinding. The extraction trials were triplicated. The yield measurements were performed using the Randall SE (55 C; 160 min). It should be emphasized that, whatever the products we considered, the same evolution of increase in yields was observed according to the envisaged processes. Thus systematically, with respect to the CSE, the increase in yields was successively observed with US-SE, followed by SE of DIC-textured materials, to achieve the maximum yield by combining DIC pretreatment with US-assisted SE. They successively were, for the original materials from 108% to 113%, 112% to 119%, and

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

233

117% to 120%, respectively, and for cold-pressing cake, from 103% to 105%, 107% to 110%, and 112% to 113%, respectively. It is also worth noticing that DIC, alone and significantly better when combined with USs, has resulted in the greatest improvement in oil extraction efficiencies. Thus in comparison with the case of expander, it is obvious that DIC has been the most effective in breaking cell walls. Indeed, the increasing order of oil yield should have revealed that DIC has generated many more broken-wall cells than both ultrasonic cavitation and expander autovaporization taken out separately or even coupled.

8.4.2 Kinetics of vegetal oil extraction The main objective of this part of the study was to evaluate the impact of coupled DIC texturing as a pretreatment with ultrasonic as intensification way of n-hexane extraction technique in terms of kinetics and rate. This approach was based on the development of extraction kinetics from different oilseeds possibly after an expander treatment and from cakes issued from cold pressing of the two different varieties of rapeseeds indicated earlier.

8.4.2.1 Time to obtain the equivalent oil yields as conventional solvent extraction For each type of the oleaginous materials, experiments of extraction kinetics were performed for 160 min using the dynamic maceration, attended or not by US. The evolution of yields always expressed in g oil/g db (not including water content) was enunciated as a function of the time: W 5 f(t). Henceforth, the impacts of DIC pretreatment and US on n-hexane extraction kinetics were evaluated relatively to conventional oil extraction of each raw material. As shown in Fig. 8.5 and Table 8.1, whatever the nature and variety of the product, and even after modification of the structure by expanding, the set of extraction kinetics separately justified the both operations of US and DIC to significantly intensify the SE technique. However, systematically, the highest impact was reported with an evident synergistic effect when these both intensification technologies DIC and US were coupled. Thus the comparison of kinetics was carried out for the following oil extraction processes of: (1) CSE, (2) US-SE, (3) DIC texturing as a structural pretreatment prior to the SE (DIC-SE), and (4) coupled DIC texturing/ DIC-US-SE/US-SE. The times required for reaching similar yields was, respectively, CSE tA 5 160 min US-SE tB 5 106 6 24 min DIC-SE tC 5 65 6 34 min and DIC/US-SE tD 5 41 6 25 min This allows positing that, by coupling adequate DIC texturing and US-SE, the time of the operation becomes about four times less than the CSE operation.

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Figure 8.5 Compared kinetics of (A) CSE, (B)US-SE, (C) DIC-SE, and (D) Coupled DIC/ US-SE of various oleaginous samples. CSE, Conventional solvent extraction; DIC/US-SE, instant controlled pressure drop texturing/ultrasound-assisted solvent extraction; DIC-SE, instant controlled pressure drop texturing as a structural pretreatment prior to the solvent extraction; US-SE, ultrasound-assisted solvent extraction.

Table 8.1 Impact of instant controlled pressure drop (DIC) treatment and ultrasound treatment on extraction kinetics: Yields done by Randall, 55 C; 160 min; kinetics done by dynamic maceration (DM) related by coupled washing diffusion (CWD) phenomenological model with (Deff and δYs) as model factors and equivalent time (min) to get the same yields equivalent to the conventional solvent extraction. RM

Type of technology

Oil yields Randall, 55 C; 160 min

Crushed soybeans

Flaked soybeans

Expanded soybeans

Sunflower linoleic

Crushed CSE Crushed 1 US DIC textured DIC textured 1 US Flaked CSE Flaked 1 US DIC textured DIC textured 1 US Expander textured CSE Expander textured 1 US DIC textured DIC textured 1 US Untextured CSE Untextured 1 US DIC textured DIC textured 1 US

Kinetic CWD model of solvent oil extraction DM Diffusivity Deff

Time for getting equivalent yields

R2 of CWD model

Starting accessibility δYs

(g oil/ 100 g db)

(%)

(10210 m2/s)

(%)

(g oil/ 100 g db)

(%)

(min) ¤(%)

(%)

20.71 22.47 23.51 24.29 21.25 22.52 23.98 24.64 22.43

100 108 114 117 100 106 113 116 100

0.032 0.043 0.055 0.073 0.017 0.019 0.034 0.047 0.027

100 134 172 228 100 112 200 276 100

12.4 13.4 17.7 18.6 14.9 16.9 19.6 20.3 16.6

100 108 143 150 100 113 132 136 100

tA 5 160 ¤ 100 tB 5 112 ¤ 70 tC 5 75 ¤ 47 tD 5 48 ¤ 30 tA 5 160 ¤ 100 tB 5 108 ¤68 tC 5 40 ¤ 25 tD 5 27 ¤ 17 tA 5 160 ¤ 100

86.57 93.67 95.45 98.71 95.55 96.96 98.48 97.08 98.64

23.48

105

0.03

111

19.2

116

tB 5 101 ¤ 63

98.96

24.64 24.94 41.52 44.89 46.44 49.41

110 111 100 108 112 119

0.065 0.083 0.09 0.15 0.18 0.47

241 307 100 167 200 522

20 20.9 33.6 34.6 39.7 38.4

120 126 100 103 118 114

tC 5 47 ¤ 29 tD 5 28 ¤ 18 tA 5 160 ¤ 100 tB 5 86 ¤ 54 tC 5 40 ¤ 25 tD 5 20 ¤ 13

97.52 99.32 99.42 98.27 99.36 91.22 (Continued)

Table 8.1 (Continued) RM

Type of technology

Oil yields Randall, 55 C; 160 min

Sunflower oleic

Rapeseeds Jura

Rapeseeds Pioneer

Untextured CSE Untextured 1 US DIC textured DIC textured 1 US Cold-pressing cake CSE Cold-pressing cake 1 US DIC cold-pressing cake DIC 1 US coldpressing cake Cold-pressing cake CSE Cold-pressing cake 1 US DIC cold-pressing cake DIC 1 US coldpressing cake

Kinetic CWD model of solvent oil extraction DM Diffusivity Deff

Time for getting equivalent yields

R2 of CWD model

Starting accessibility δYs

(g oil/ 100 g db)

(%)

(10210 m2/s)

(%)

(g oil/ 100 g db)

(%)

(min) ¤(%)

(%)

41.74 45.24 46.99 48.84 14.85

100 108 113 117 100

0.09 0.14 0.23 0.31 0.038

100 156 256 344 100

33.9 37.3 39.3 42.4 7.4

100 110 116 125 100

tA 5 160 ¤ 100 tB 5 68 ¤ 43 tC 5 35 ¤ 22 tD 5 18 ¤ 11 tA 5 160 ¤ 100

94.61 98.55 92.56 87.30 97.21

15.62

105

0.045

118

8.5

115

tB 5 128 ¤ 80

97.86

15.89

107

0.05

132

11

149

tC 5 118 ¤ 74

92.77

16.67

112

0.069

182

12.3

166

tD 5 63 ¤ 39

97.08

14.76

100

0.048

100

6.1

100

tA 5 160 ¤ 100

98.79

15.12

102

0.048

100

8.1

133

tB 5 140 ¤ 88

99.38

15.93

108

0.066

138

9.5

156

tC 5 102 ¤ 64

98.78

16.33

111

0.088

183

10.1

166

tD 5 83 ¤ 52

96.81

CSE, Conventional solvent extraction; DIC, instant controlled pressure drop; US, ultrasound; RM, raw-material.

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

237

8.4.2.2 Kinetic parameters defined from coupled washing/ diffusion phenomenological model Fig. 8.5 shows the experimental data, generally triplicated of the variation of oil yields versus time according to the type of materials. These data were used to identify the main kinetic parameters issued from the CWD phenomenological model. It is worth noting that CWD stipulates a first washing stage followed by a constant diffusivity second diffusional stage. Table 8.1 brings together the values of R2, effective diffusivity Deff (m2/s) and starting accessibility δYs (g oil/g db). The values of R2 should reveal the validity degree of the NER and constant diffusivity hypotheses. Established over 160 min, the results obtained from the DIC-treated oleaginous seeds all have exhibited the highest increase in the extraction yield, the lowest extraction time, the most significant improvement in both mean effective diffusivity Deff and starting accessibility δYs.

8.4.2.2.1 Effect of flash depressurization by expander and instant controlled pressure drop pretreatments on extraction kinetics In the case of flaked soybeans results, it was possible to perform the rapid depressurization of optimized expander pretreatment. This resulted in increasing yields from 0.2125 to 0.2243 g oil/g db, effective diffusivity from 0.017 to 0.027 m2/s, and starting accessibility from 0.149 to 0.166 g oil/g db. However, much deeper modifications were observed in DIC flash depressurization. Henceforth, DIC pretreatment allowed reducing the effective extraction time to a quarter compared with the expander (46 against 160 min). Fig. 8.3 can easily justify such a much deeper impact of DIC than expander with, as example, the amount of vapor autovaporized with 8.4 g vapor/100 g db for DIC as against 3.6 g vapor/100 g db caused by the expander system. Although the flash depressurizations by expander and DIC both result in oilseed pretreatment prior to the SE, it is possible to easily distinguish the difference in intensification provided by each of these two operations. Thus both operations obviously bring an intensification of the extraction phenomenon through a modification of the technological ability such as porosity, tortuosity, and the number of brokenwall cells of the different materials. However, the DIC stands out as being the lowest severe operation, ending in a much lower temperature level (30 instead of 100 C); with no need of an additional final cooling stage; creating a much higher swelling rate; needing a much lower energy cost.

8.4.2.2.2 Intensification effect induced by ultrasound technique The well-known effect of US as able to significantly intensify the SE kinetics was confirmed by the huge experiments presented in the present chapter. Accordingly, the extraction time defined as the time required for getting an equivalent oil yield,

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varied between 140 and 68 min (with an average value of 106 6 24 min) against 160 min for CSE. This means a relative time value of about 66% 6 23%. The phenomenological CWD model based on the assumption of a constant diffusivity was applied for the US-SE operations for crushed, flaked, and expanded soybeans, as well as linoleic sunflower seeds and oleic sunflower seeds, cold-pressing cake rapeseeds Jura and Pioneer. The values of R2 were 93.67%, 96.96%, 98.96%, 98.27%, 98.55%, 97.86%, 99.38%, respectively. This has been a great proof of the validity of our constant diffusion hypotheses. Subsequently, it is much more plausible that the impact of the US is not the result of a continuous structural change during the 160-min SE. The US is intensifying SE not through a gradual generation of new broken-wall cells by some cavitation (and cell explosion) but rather through its impact in stirring the solvent into the matrix pores. US applied to nontextured seeds improved the extraction kinetics through higher effective diffusivity Deff by 128% 6 25% (134%, 112%, 111%, 167%, 156%, 118%, and 100%), and starting accessibility δYs by 114% 6 9% (108%, 113%, 116%, 103%, 110%, 115%, and 133%).

8.4.2.2.3 Impact of coupling instant controlled pressure drop with ultrasound technique on solvent extraction kinetics In the current study the greatest intensification was obtained by coupling DIC texturing prior to a US-SE. The statistical analysis based on the P value confirms their significant and synergistic effect on greatly increasing yields, kinetics, starting accessibility, and effective diffusivity. Texturing by DIC technology applied under optimal conditions of operating parameters (pressure and treatment time) followed by US-assisted extraction allows a maximum of oil yield of 115% 6 3% (117%, 116%, 111%, 119%, 117%, 112%, and 111%). The effective diffusivity increased by 292% 6 118% (228%, 276%, 307%, 522%, 344%, 182%, and 183%), while the effective diffusivity enlarged by 140% 6 21% (150%, 136%, 126%, 114%, 125%, 166%, and 166%). This implied a highly reduced extraction equivalent time of 26% 6 15% (30%, 17%, 18%, 13%, 11%, 39%, and 52%). The set of phenomenological modeling results confirm the hypothesis of a constant diffusivity during the diffusional phase of extraction kinetics. This allows us to impute the effect of DIC texturing to a change in the technological aptitudes of the previously swelled with broken-wall cell materials. By cons, the effect of US would result from the phenomenon of microagitation within the pores during the extraction and not provided by a gradual cavitation which seems, in our cases, negligible.

8.4.3 Impact on oil quality With these differently DIC-treated soybeans, sunflower seeds, and rapeseeds, the oil composition study (Tables 8.2
8.4, respectively) shows a highly satisfying preservation of the oil quality whatever the DIC pretreatments and US-SE ways.

Table 8.2 Variation of fatty acids profiles and content for different tocopherols fractions in soybean oil. Crushed soybean oil

C16: 0 C18: 0 C18: 1 C18: 2 C18: 3 C22: 0 Beta Gama Alpha Total toco

Flattened soybean oil

Expanded soybean oil

RM

RM 1 US

DIC

DIC 1 US

RM

RM 1 US

DIC

DIC 1 US

RM

RM 1 US

DIC

DIC 1 US

11.0 4.55 24.1 53.0 6.95 0.42 183.3 301.7 33.56 518.5

11.0 4.49 24.0 53.0 7.15 0.41 161.6 303.8 32.92 498.2

11.0 4.50 24.0 52.8 7.07 0.52 182.3 335.9 34.96 553.2

11.0 4.54 24.0 53.0 7.05 0.41 172.8 301.0 33.03 506.7

11.0 4.51 23.8 53.1 7.12 0.44 176.2 298.2 38.10 512.4

11.0 4.55 24.0 52.9 7.03 0.41 179.6 289.7 35.87 505.2

10.9 4.53 24.8 52.4 7.10 0.39 194.1 311.3 37.43 542.9

11.0 4.51 24.0 53.0 7.11 0.41 166.1 288.8 35.76 490.6

10.8 4.46 24.0 53.1 7.19 0.41 182.0 290.1 36.23 508.3

11.0 4.53 24.1 52.9 7.09 0.41 187.7 309.0 38.39 535.1

11.0 4.50 23.9 53.0 7.19 0.42 183.9 285.9 36.69 506.5

11.0 4.51 24.1 52.9 7.08 0.41 167.9 274.6 31.25 473.8

CSE, Conventional solvent extraction; DIC, instant controlled pressure drop; SE, solvent extraction; US, ultrasound.

Table 8.3 Variation of fatty acids profiles and content of different tocopherols fractions in rapeseed oil. Compounds

C16:0 C18:0 C18:1 C18:2 C18:3 C22:0 Beta Gama Alpha Total tocopherol

Rapeseed Jura

Rapeseed PR72

CSE-RM

SE-US

DIC-SE

DIC 1 US-SE

CSE-RM

SE-US

DIC-SE

DIC 1 US-SE

4.69 1.86 60.56 3.05 20.38 9.46 8.48 309.6 115.2 433.3

4.66 1.86 60.22 3.34 20.46 9.47 8.66 331.4 123.5 463.6

4.76 1.83 60.03 3.33 20.66 9.39 6.97 296.4 116.5 419.9

4.69 1.86 60.12 3.34 20.46 9.47 9.31 323.7 151.2 484.2

3.88 2.70 65.10 2.91 16.17 7.95 5.09 297.2 93.5 395.8

3.80 1.93 66.45 2.17 15.97 7.78 5.35 310.3 114.0 429.6

3.79 1.90 66.99 2.09 16.54 7.92 6.01 301.4 97.9 405.3

3.80 1.93 66.33 2.08 15.86 7.71 5.07 304.9 114.0 423.9

CSE, Conventional solvent extraction; DIC, instant controlled pressure drop; SE, solvent extraction; US, ultrasound.

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

241

Table 8.4 Variation of fatty acids profiles and content for different (linoleic and oleic) sunflower seed oils. Acide gras

RM

RM 1 US

DIC

DIC 1 US

RM

RM 1 US

DIC

DIC 1 US

C16:0 C18:0 C18:1 C18:2

6.75 4.35 24.14 63.28

6.82 4.45 24.58 63.21

6.57 4.209 23.45 63.99

6.77 4.45 25.39 63.39

3.93 2.14 89.77 2.58

3.79 2.18 90.24 2.4

3.88 2.13 89.5 2.54

3.76 2.27 90.04 2.65

The different soybean oils all were characterized by a dominance of the unsaturated fraction (84.06%) that includes oleic C18:1, linoleic C18:2, and linolenic acid C18:1 at 24.1%, 53.01%, and 6.95%, respectively. The saturated fatty acid family shows dominance for palmitic acid C16:0 (11%). Similar ascertainment was observed on the content for different tocopherol fractions (Table 8.2). The presence of the gamma-, beta-, and alpha-tocopherol fractions had the same values of 301.7, 183.3, and 33.56 μg/g oil, respectively. Regarding the two types of rapeseeds (Jura and Pioneer), the chromatographic analysis shows a similarity of composition either for the distribution of fatty acid profiles or the content of different fractions of tocopherols expressed in μg/g oil (Table 8.3). Rapeseed oil contains approximately 83.99% of unsaturated fatty acids; C18:1 oleic acid, C18:2 linoleic acid, and C18:3 linolenic acid at 60.56%, 3.05%, and 20.38%, respectively. On the other hand, the various DIC treatments of rapeseeds and different intensifications of SE allowed also, preserving oil contents of gamma-, alpha-, and beta-tocopherols (Table 8.3), at about 309.6, 115.2, and 8.48 μg/g oil, respectively. This means 433.3 μg/g of total tocopherol well known as an important antioxidant of oils. For sunflower oil extraction (Table 8.4), the composition of saturated and unsaturated fatty acids, including palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), and linoleic acid (C18:1) was significantly preserved for CSE, US-SE, DIC-SE, and DIC-US-SE of both linoleic and oleic varieties. GC gas chromatographic results show that there is no change in the fatty acid content of DIC-assisted textured samples with nontextured (RM) samples. The study of the quality of extracted oils shows a similarity of composition in terms of the distribution or profiles of the main fatty acids as well as for the tocopherol contents. This confirms the possible very weak degradation of the product quality after the different unit operations of grains pretreatment before triturating and oil extraction. Hence, the best intensification way of the n-hexane extraction of vegetal oil, an integration of DIC texturing coupled with US-assisted extraction is highly recommended as it allows obtaining high oil yield levels, low extraction time, and satisfying preservation of the quality.

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8.4.4 Specific new desolventation ways

Initial hexane concentration in the cake 250 200 150 56.3 ppm 100

42.4 ppm

50

1.36 ppm

0

Hexane concentration in Camelina oil Initial hexane level of 104 ppm 3000

1820 ppm

2500 2000 1500 1000 500 0

Normelimite290ppm Limit standard of 290 ppm 200 ppm

Residual hexane concentration (ppm)

Residual hexane concentration in camelina cake Hexane concentration in cake of rapeseed

Residual hexane concentration (ppm)

Residual hexane concentration (ppm)

Residual hexane concentration (ppm)

Desolventation process is a crucial stage of refining both oil and cake issued from SE operations. The use of instant autovaporization has been defined for various applications of swelling, microbiological decontamination, and essential oil extraction. Two types of DIC can be performed; the first involves coupling pressure and temperature of saturated-dry steam, while the second called multiflash autovaporization (MFA). However, stands out as independently involving compressed air and treatment temperature. Both DIC and MFA include as the main stage the instant pressure drop, which usually is achieved in less than dozens of milliseconds. MFA was used in the specific field of oil industry as a refining step of deodorization. It allowed reaching greatly more relevant results than airflow or high-temperature conventional processes. By deeply reducing the severity of the operation, deodorization was carried out without inducing thermal degradation, while involving lower energy consumption (Fig. 8.6). In the current case of desolventation, a nonoptimized operation coupling airflow evaporation , MFA, and DIC was used for both solid (cake) and liquid (oil) with initially high n-hexane concentration. In both case, the standard required by the industry collaborating with our laboratory was identified as 290 ppm. The difference between DIC and MFA is located at the heating and high-pressure sources: initial hexanelevel: 450 ppm

400

Caméline

300

Limit standard: 290 ppm 100 ppm

200

83.4 ppm

4.3 ppm

100 0

Initial hexane level of104 ppm

Hexane concentration of rapeseed oil

3000 2500

1640 ppm

2000 1500 1000

Limit 290 ppm 100 ppm

500 0

Figure 8.6 Nonoptimized operations of desolventation of oil and cake obtained by solvent extraction of rapeseeds and Camelina seeds. The processes involved in these operations were (A) the AFE (up to 24 h), (B) the MFA of treatment air pressure of P 5 0.45 MPa, at ambient temperature, and t 5 27 s/cycle for up to 600 cycles, and, for cakes (solids) (C) DIC operated at 0.3 MPa, a processing time of 15 s/cycle and for a number of cycles up to five cycles. AFE, Airflow evaporation; DIC, instant controlled pressure drop; MFA, multiflash autovaporization. The processing conditions were selected from preliminary trials, based on the thermodynamic data of hexane volatility.

Instant controlled pressure drop as new intensification ways for vegetal oil extraction

G

G

243

Instant Controlled Pressure Drop DIC implicated the saturated-dry steam pressure at P 5 0.3 MPa for a processing time t 5 15 s, and a number of DIC cycles up to 5 operations. MFA implied an air pressure of P 5 0.45 MPa, at ambient temperature, and t 5 27 s/cycle, with numerous treatment cycles (50
600 cycles),

The values of residual hexane of the cakes of rapeseeds and Cameline, and the oils of rapeseeds and Camelina, reached 1.36, 4.3, 200, and 100 ppm, respectively.

8.5

Conclusion

Conducted on the study of the intensification of oilseed extraction processes in the vegetable oil industry, this work confirms the high potential of DIC technology coupled with US-assisted extraction on improving extraction kinetics such as the effective diffusivity Deff (m2/s) of the solvent used and the starting accessibility δYs (g oil/g db). Compared with conventional extraction and based on the CWD phenomenological model, the study of extraction kinetics variation as a function of the intensification processes showed that a treatment with DIC applied under optimum conditions (t, P) is at the origin of an improvement explained by a modification of the technological ability generated by a texturing. This study confirms the effectiveness of ultrasonic treatments on the intensification of oil extraction phenomena from oleaginous grains. Based on the assumption of constant diffusivity, the US technology’s effect is explained rather by a microagitation and not by cavitation (and blast cells) which remains negligible. All the results have concluded that a better extraction is achieved due to the coupling of DIC texturing technology followed by US-assisted extraction. This work has shown quality preservation of the extracted oil confirmed by a similarity or a slight nonsignificant variation in the composition of free fatty acids and the content of different fractions of tocopherols. Further research works with adequate DIC-MFA equipment shall improve the operations of MFA/DIC desolventation to reach dozens of times lower residual hexane than standard requirements.

References Allaf, T., & Allaf, K. (2014). Instant controlled pressure drop (D.I.C.) in food processing. New York: Springer. Allaf, K., Louka, N., Parent F., Bouvier, J.-M., Forget, M. (1999). Method for processing phytogenic materials to change their texture, apparatus therefor & resulting materials; Application no.: 08/592417. Publication no.: 5,855,941. USA; No.: EP0776164B1. US5855941. Ben Amor, B., & Allaf, K. (2009). Impact of texturing using instant pressure drop treatment prior to solvent extraction of anthocyanins from Malaysian Roselle (Hibiscus sabdariffa). Food Chemistry, 115(3), 820
825.

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Bouallegue, K., Allaf, T., Besombes, C., Younes, R. B., & Allaf, K. (2015). Phenomenological modeling and intensification of texturing/grinding-assisted solvent oil extraction: case of date seeds (Phoenix dactylifera L.). Arabian Journal of Chemistry. Ferna´ndez, M. B., Perez, E. E., Crapiste, G. H., & Nolasco, S. M. (2012). Kinetic study of canola oil and tocopherol extraction: Parameter comparison of nonlinear models. Journal of Food Engineering, 111(4), 682
689. Hensarling, T. P., & Jacks, T. J. (1983). Solvent extraction of lipids from soybeans with acidic hexane. Journal of the American Oil Chemists’ Society, 60(4), 783
784. Kadi, H., Meziane, S., & Lamrous, O. (2006). Kinetic study of oil extraction from olive foot cake, Grasas y Aceites (Espan˜a). Liu, K. (2012). Soybeans: Chemistry, Technology, and Utilization. Springer. Mason, T. J. (1996). Sonochemistry: Uses of ultrasound in chemistry and related disciplines. Ultrasound angioplasty (pp. 25
54). Boston, MA: Springer. Mason, T. J. (1997). Ultrasound in synthetic organic chemistry. Chem. Soc. Rev. 26(6), 443
451. Mounir, S., & Allaf, K. (2008). Definition of three-stage spray drying by inserting the instant controlled pressure drop (DIC) technology in the classical spray drying process. Journal of Drying Technology, 26(4), 452
463, Special issue on Non-conventional Drying Techniques. Mounir, S., & Allaf, K. (2014). DIC-assisted hot air drying of post-harvest paddy rice. In T. Allaf, & K. Allaf (Eds.), Instant controlled pressure drop (D.I.C.) in food processing (pp. 45
55). New York: Springer. Mounir, S., Allaf, T., Berka, B., Hassani, A., & Allaf, K. (2014). Instant controlled pressure drop technology: From a new fundamental approach of instantaneous transitory thermodynamics to large industrial applications on high performance
high controlled quality unit operations. Comptes Rendus Chimie, 17(3), 261
267. Mounir, S., Schuck, P., & Allaf, K. (2010). Structure and attribute modifications of spraydried skim milk powder treated by DIC (instant controlled pressure drop) technology,”. Dairy Science & Technology, 90(2
3), 301
320. Paiva, M. (1972). Me´thode nouvelle de re´solution de l’e´quation de transport de matie`re dans un milieu he´te´roge`ne avec diffusion (application au transport des gaz dans le poumon humain). Biophysik, 8(4), 280
291. Pan, Z., Qu, W., Ma, H., Atungulu, G. G., & McHugh, T. H. (2011). Continuous and pulsed ultrasound-assisted extractions of antioxidants from pomegranate peel. Ultrasonics Sonochemistry, 18(5), 1249
1257. Rombaut, N., Tixier, A.-S., Bily, A., & Chemat, F. (2014) Green extraction processes of natural products as tools for biorefinery. Biofuels, Bioproducts and Biorefining, 8(4), 530
544. Wiley Online Library [Online]. Available: ,https://onlinelibrary.wiley.com/ doi/full/10.1002/bbb.1486. Accessed 19.06.18. Rombaut, N., Tixier, A.-S., Bily, A., & Chemat, F. (2018). Green extraction processes of natural products as tools for biorefinery. Biofuels, Bioproducts and Biorefining, 8(4), 530
544. Serrato, A. G. (1981). Extraction of oil from soybeans. Journal of the American Oil Chemists’ Society, 58(3), 157
159. Zhang, Z.-S., Wang, L.-J., Li, D., Jiao, S.-S., Chen, X. D., & Mao, Z.-H. (2008). Ultrasoundassisted extraction of oil from flaxseed. Separation and Purification Technology, 62(1), 192
198.

Membrane separation in food processing

9

Wafa Guiga1 and Marie-Laure Lameloise2 1 Cnam, UMR 1145 Food Process Engineering, Paris, France, 2AgroParisTech, UMR 1145 Food Process Engineering, INRA, Universite´ Paris-Saclay, Massy, France

9.1

Overview of membrane separation processes in food industry

The basic principle of membrane separation processes is the use of a semipermeable material as an interface to separate solutes. Based on the driving force and the type of membrane, there are several families of membrane processes used in food industry in the liquid phase (Table 9.1). Membranes are generally characterized by (1) a low thickness (100
200 μm maximum) in order to ensure low resistance to permeate flow and (2) the use of tangential flow (cross-flow) in order to limit particles or solute concentration or deposition at the surface and maintain high permeate flux for a longer duration before fouling (Fig. 9.1). Dead-end filtration (transversal flow) is encountered at lab scale for analytical purposes or in the case of easy filtrations with low fouling as for example in drinking water [ultrafiltration (UF) with hollow fiber membranes].

9.1.1 Pressure-driven membrane technologies The common basis for pressure-driven membrane separation techniques is particle size difference, even though other properties of the solutes and physical
chemical interactions (electrostatic, H-bond, π
π, etc.) with the membranes may play an important role, especially for tight and dense membrane separations. Fig. 9.2 presents particle sizes associated to each of the four techniques: microfiltration (MF), UF, nanofiltration (NF), and reverse osmosis (RO). MF. With membrane pore sizes ranging from 0.1 to 10 μm, MF is commonly used to remove insoluble particles (typically particles responsible for turbidity) and microorganisms such as yeasts or bacteria. It uses relatively low transmembrane pressure (TMP from 0.1 to 5 bar) associated with high tangential velocity: a typical set of parameters is 0.5 bar—5 m/s. MF favorably competes with centrifugation, or with conventional depth filtration, a discontinuous operation that requires consumable media such as cartridges, cellulose sheets, filter-aid precoats, and possibly preceded by flocculation/coagulation steps with chemical aids. Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00009-4 © 2019 Elsevier Inc. All rights reserved.

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Table 9.1 Classification of membrane technologies according to driving force and membrane type. Driving force

Concentration gradient Electrical potential gradient Pressure gradient Vapor pressure gradient

Membrane type Porous

Dense

Dialysis Electro-ultrafiltration MF, UF, NF Osmotic evaporation Membrane distillation

Forward osmosis Electrodialysis Reverse osmosis Pervaporation

MF, Microfiltration; NF, nanofiltration; UF, ultrafiltration.

Figure 9.1 Dead-end and cross-flow filtration—permeate flow and cake thickness change with time.

UF concerns membranes with pores ranging approximately from 3 to 100 nm. Separation is also based on particle size, preferably expressed as molar mass because it mainly addresses macromolecules separation. The molecular weight cutoff [MWCO, in g/mol or Da (Dalton)] is defined as the molar mass of the smallest molecule rejected at 90%. The range covered is 5000
500 3 103 g/mol. The applied pressure generally ranges from 0.5 to 9 bar, but a typical set of parameters is 4 bar—4 m/s. The separation of proteins by the UF has driven a spectacular development of membranes in dairy industry, and subsequently in numerous other sectors of food industry. The UF (together with the MF) is also efficient for colloids, a family of particles difficult to remove because of their very small size (1 μm
1 nm) and their stability (electrical repulsion).

Membrane separation in food processing

247

Figure 9.2 Approximate particle sizes and pressure-driven separation processes.

NF separation can be used to separate low-molecular-weight solutes (down to 200 g/mol) and needs consequently higher applied pressures (4 to 20
30 bar). Although it is still a matter of discussion, most NF membranes are considered (nano)porous membranes with pore radius between 0.5 and 1
2 nm; however, there is little difference, regarding MWCO, between the loosest RO membranes and the tightest NF membranes which can then be assimilated to dense membranes. A specificity of NF membranes, due to the material used, is the presence of superficial charge (also been evidenced in the UF at a lesser extend). Depending on the pH of the solution, lower or higher than the isoelectrical point (pHi) of the membrane, membrane surface is either positive or negative (3 , pHi , 5). Thanks to Donnan exclusion phenomenon, this enables to separate multivalent ions such as calcium, magnesium, or sulfate from monovalent, offering, for example, an environmentfriendly alternative to ion-exchange (IE) softening. Applications concern the concentration of small organic molecules and simultaneous elimination of ions and have been growing since the 1990s. RO as a dense membrane technique differs from the previous ones. Its principle is presented in Fig. 9.3. It is mainly based on the difference of solubility and diffusion of water and solutes in the membrane material, which results in favoring water transfer compared with solute transfer. The applied pressures are high (up to 75 bar) because of the osmotic pressure to be overcome. In dilute solutions, osmotic pressure π is calculated by the van’t Hoff equation: π5

X i

Ci 3 R 3 T

(9.1)

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Green Food Processing Techniques

Figure 9.3 Principle of reverse osmosis.

where Ci is the molar concentration of each dissociated solute i, R the ideal gas constant, and T the temperature (K). In the last few decades the quasiunique application of RO was seawater desalination, as an alternative to conventional distillation. In food industry, application of RO is for preconcentrating solutions ahead of thermal concentration and more recently for the recovery of process water from effluents.

9.1.2 Electrically driven membrane technology Electrodialysis (ED) is an electrically driven membrane technology based on ionexchange (IE) membranes and an electric field. In the most common configuration, homopolar cation-exchange membranes (ideally permeable to cations only) and anion-exchange membranes (permeable to anions only) are alternately disposed, determining two-compartment cells. Electromigration of the ions and permselectivity of the membranes result in the transfer of the ionic species from the feed (diluate) to the concentrate compartment of the cell (Fig. 9.4). At last, ED allows to separate ionic from nonionic species, finding applications for demineralization of liquid streams (whey demineralization is a historical example) or for the recovery and concentration of ionized species (recovery of organic salts from fermentation). Compared with classical demineralization schemes using cation-exchange and anion-exchange resins, ED has the outstanding advantage of needing no regeneration, no chemical reactant and producing no waste, except of course for cleaning steps. In the 1980s the availability of bipolar membranes (BMs) has extended the scope of applications. BMs present a cation-exchange side and an anion-exchange side. Submitted to an

Membrane separation in food processing

249

Figure 9.4 Principle of homopolar electrodialysis.

Figure 9.5 Different configurations of electrodialysis including bipolar membranes for the conversion of salt into conjugated base or acid.

intense electric field (four to five times higher than homopolar membranes), they provoke water dissociation into H1 and OH2 and their separation on the respective sides. Combination of bipolar and homopolar membranes in different configurations (Fig. 9.5) allows the recovery of pure acid and/or base from their conjugated salts. It offers smart solutions to hard-to-solve problems, such as the fate of saline wastewaters arising from IE regeneration. They are also associated to a primary homopolar step in novel schemes for the recovery of organic acids from fermentation broth (Bailly, Roux-de Balmann, Aimar, Lutin, & Cheryan, 2001; Lameloise & Lewandowski, 2012; Lameloise, Matinier, & Fargues, 2009; Roux-de Balmann, Bailly, Lutin, & Aimar, 2002). To perform ED the conductivity of the solution must be at least 8
10 mS/cm although systems have recently been developed to deal with less conductive solutions (Lutin & Bailly, 2006). Therefore when complete demineralization is required (like in the current whey demineralization process), ED should be completed with IE for energy purposes.

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9.1.3 Vapor pressure gradient membranes Osmotic evaporation (OE) (also called osmotic distillation) uses a hydrophobic microporous membrane to separate and put into contact two liquids with different water activities (aw). Pore diameter and material are chosen in order to prevent the wetting of the membrane by liquid so that its pores remain full of air. Because of the aw difference, a gradient of partial pressure of water appears spontaneously through the membrane generating a driving force for water transport from the compartment with the higher aw (solution to be concentrated) to the other (generally a brine). The interest of this technology is to concentrate liquids without heating and allowing to better preserve the quality. Although the process was patented in the 1990s, it is still in development and not yet available at commercial scale. It is currently still limited by low permeate flow at high concentration and the management of the brine. Membrane distillation (MD) is rather close to OE. It also uses microporous hydrophobic membranes to separate two liquid streams at different temperature. The driving force is the vapor pressure difference between the two solution
membrane interfaces due to the existing temperature gradient (Jiao, Cassano, & Drioli, 2004). In pervaporation the selective transfer through a dense membrane is accompanied by the evaporation of permeate, which is collected after condensation. The driving force results from the creation of partial vacuum in the permeate side. In food industry, pervaporation found its main application for the dehydration of ethanol.

9.2

Theoretical aspects in membrane separation

The theoretical aspects developed below essentially concern pressure-driven processes that are, with ED, the most commonly used in food process applications.

9.2.1 Key parameters in membrane separation TMP. Pressure-driven membrane separations are ensured by the application of a pressure gradient between feed and permeate side (PP) of the membrane. To take into account the possible difference of pressure between the feed inlet (PF) and the retentate (PR) outlet, TMP is calculated, considering a linear variation, as TMP 5

P F 1 PR 2 PP 2

(9.2)

Permeate flux (JP). It represents the permeate flowrate (QP) reported to the unit membrane surface: JP 5

QP A

(9.3)

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251

Rejection. The rejection (R) of a component is calculated on the basis of its concentration in permeate (CP) and in retentate (CR) and expressed as a percentage:
 CP Rð%Þ 5 1 2 3 100 CR

(9.4)

It expresses the separation efficiency for a given component. Conversely, a transmission rate (Tr) is calculated as follows: Tr ð%Þ 5

CP 3 100 CR

(9.5)

Membrane selectivity φ toward two components i and j, a useful parameter for membrane choice in fractionation applications, can be defined as follows: φ5

Tri Trj

(9.6)

Permeability to solvent and permeability to solutions. In pressure-driven processes, membrane permeability to solvent (generally water in food applications) is measured as the slope of water flux variation versus TMP (Fig. 9.6). In the presence of solutes, membrane permeability to solution is often lowered as solute concentration increases. The critical flux, when the relation between permeate flux and TMP deviates from linearity, is associated to a change from a reversible to an irreversible fouling. A limiting flux can be identified above which the increase of TMP does not improve any more the permeate flux. This limiting flux increases with tangential velocity.

Figure 9.6 Pure solvent and permeate fluxes variation with TMP. TMP, Transmembrane pressure.

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9.2.2 Transport theory For pressure-driven processes, convective transport is dominant in the case of porous membranes (MF, UF). Diffusive mechanisms prevail in the case of dense membranes (RO and some tight NF). Both mechanisms are illustrated in Fig. 9.7. For decades, mixed convective
diffusive mechanism has been discussed to describe dense membrane transport mechanisms but, currently, diffusive models based on Fick’s law are widely used and considered predictive enough for simple and diluted mixtures. The most commonly used models to describe the fluxes of permeate or solutes and the solutes retentions, namely, pore-flow model and solution-diffusion model, are presented further.

9.2.2.1 Pore-flow model Due to their heterogeneity in structure, composition, and thus in separation mechanisms (e.g., molecular sieving, adsorption), no single theory unifies till now the description of the transport mechanisms in microporous membranes. The general behavior is described with the Darcy law, expressing solvent flux (Jw) as a function of TMP, solution viscosity (μ), and membrane resistance (Rm): Jw 5

TMP Rm 3 μ

(9.7)

where 1=ðRm 3 μÞ 5 LP membrane permeability to solvent often expressed in L/h/m2/bar.

Figure 9.7 Molecular motion depiction through dense and porous membranes. (A) Porous membrane. (B) Dense membrane.

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In the presence of solute, additional resistances due to different phenomena such as building up of a cake on the top surface of the membrane, fouling or concentration polarization (see further) should be considered. They can be classified into reversible resistance Rrev (can be suppressed through rinsing) or irreversible resistance Rirrev (needs chemical or mechanical cleaning). JP 5

TMP ðRm 1 Rrev 1 Rirrev Þ 3 μ

(9.8)

where Rm 1 Rrev 1 Rirrev 5 Rtot ðtotal resistanceÞ Osmotic pressure can modify the effective pressure and must be taken into account for process sizing and performances prediction. Permeate flux becomes JP 5

ðTMP 2 ΔπÞ Rtot 3 μP

(9.9)

where Δπ is the osmotic pressure gradient between feed (or retentate) and permeate.

9.2.2.2 Solution-diffusion model This model suggests that solutes first dissolve into the membrane material then diffuse inside it, according to the Fick’s diffusion law. Solute flux (Js) is thus expressed as JS 5

D3K 3 ðCR 2 CP Þ δ

(9.10)

where D is the diffusion coefficient of the considered solute inside the dense membrane material, K its partition coefficient between the membrane material and the solvent, and δ the membrane thickness.D 3δ K 5 B is the solute permeability constant. Permeate flux is generally expressed as JP 5 A 3 ðTMP 2 ΔπÞ

(9.11)

where A is the membrane permeability to permeate, that is, assumed to be equal to membrane permeability to water for diluted solutions, and lower for concentrated solutions. From Eqs. (9.4), (9.10), and (9.11) the rejection R can be written as R 5 100 3

A 3 ðTMP 2 ΔπÞ A 3 ðTMP 2 ΔπÞ 1 B

(9.12)

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According to this model, the rejection increases with effective pressure, which is indeed commonly observed in NF and RO. This model is commonly used one to describe solute transport in dense membranes and seems relevant as long as concentrations are low and solute diffusion coefficients are not modified by mutual diffusion. Maxwell
Stefan diffusive transport equation can replace Fick’s law for high concentration solutions and multicomponent systems. It is more complex but useful for fundamental investigations of membrane transport behavior.

9.2.3 Concentration polarization Concentration polarization is specific of most membrane separation processes. Due to the semipermeability of the membrane to one or more solute the flux of these solutes undergoes a discontinuity between the membrane and the fluids in contact. This leads to an accumulation (or a depletion) of the solute at the vicinity of the membrane, as illustrated in Fig. 9.8, in the case of a pressure-driven membrane process: the concentration gradient in the feed side between the bulk solution (Cf) and the interface (Cm) leads to a back-diffusion phenomenon that equilibrates with the permeation in the filtration direction. Their balance fixes the thickness δD of the diffusion boundary layer, which is as more important as turbulence is low near the membrane surface. It concretely results in an additional resistance layer to the transfer, causing a flux decay. The observed (measured) rejection rate (Robs 5 1 2 Cp/Cf) may be lower than the real rejection rate (Rreal 5 1 2 Cp/Cm): differences up to 20% have been evidenced (De´on, Dutournie´, & Bourseau, 2007). The higher osmotic pressure in the polarization layer

Figure 9.8 Hydrodynamic and diffusion boundary layers in cross-flow filtration mode.

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also contributes to decrease the effective TMP and therefore the permeate flux. Finally, the accumulation of solutes can in some cases lead to precipitation or formation of a gel (case of proteins) and irreversible fouling. Similar phenomena are observed in ED, where concentration polarization could lead to no more ions available at the membrane surface in the dilute compartment to carry the electric current. This results in high voltage drop across the polarization layer and an electric field
enhanced water dissociation, with detrimental pH local variations. Working below a maximal limiting current is therefore of utmost importance (Strathmann, 2016). The polarization layer can be described by the film model through a balance in the polarization layer between permeation and diffusion: JP 3 CP 5 JP 3 Cx 2 D 3

dCx dx

(9.13)

The resolution of Eq. (9.13) gives JP 5


 D Cm 2 CP 3 ln δD Cf 2 CP

(9.14)

which can also be written as ln

1 2 Robs 1 2 Rreal JP 5 ln 1 Robs Rreal k

(9.15)

with D=δD 5 k (m/s) is the apparent transfer coefficient in the polarization layer. k Depends on the fluid properties and on geometric and hydrodynamic characteristics. It can be approached through empirical correlations between dimensionless numbers (Table 9.2). Different correlations are available in the literature for various membrane geometries (flat, tubular, etc.) and various flow regimes. One commonly used is the Chilton and Colburn correlation for turbulent flow (Aimar, Bacchin, & Maurel, 2010): Sh 5 0:023 3 Re0:89 3 Sc1=3

(9.16)

Table 9.2 Dimensionless numbers used to characterize mass transfer. Sherwood (Sh) sh 5

k3d d 5 D δD

Reynolds (Re) Re 5

ρ3u3d μ

Schmidt (Sc) Sc 5

μ ρ3D

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For laminar flow the following approximation can be used (Aimar et al., 2010):
 dH 1=3 Sh 5 1:86 3 Re 3 Sc 3 L

(9.17)

It is also possible to estimate k and Cm (or Rreal) from Eq. (9.15) by plotting ln [(1 2 Robs)/Robs] versus JP for experiments at different velocities.

9.2.4 Membrane fouling The fouling of membranes can occur through different mechanisms as presented in Fig. 9.9A. G

G

At the top surface (external fouling) by the formation of a cake or a gel, especially when solutions contain proteins and polysaccharides; or by adsorption and electrostatic interactions at the membrane surface, which is the major fouling phenomenon of EI membranes (Lin Teng Shee, Angers, & Bazinet, 2008). In the MF and UF the deposition of microorganisms on the membrane surface can provoke biofouling by the formation of a biofilm. Due to the concentration polarization, oversaturation of a solute concentration can lead to crystallization and/or precipitation at the membrane surface. Inside the membrane thickness (internal fouling) by adsorption or adhesion. This mainly depends on the affinity between solutes and membrane materials. However, pore blocking can also occur due to the membrane morphology and solute conformation. Internal pore blocking can also occur when aggregates form between small molecules inside pores, for example, between phenolic compounds, peptides, and polysaccharides.

Fouling acts like additional resistance layers to mass transfer, resulting in permeate flux decline (Fig. 9.9B). A rapid decay is observed before the flux stabilizes at a constant low value independent from time, in a steady-state running. Preventing and limiting membrane fouling is a challenging issue, since membrane cleaning and replacement represent 20%
30% of operating costs in pressuredriven processes and 40%
50% in ED processes (Persico & Bazinet, 2018). There

Figure 9.9 Membrane fouling mechanisms (A) and resulting permeate flux decrease (B).

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are numerous studies on the characterization of membrane fouling by solutes such as proteins and peptides in the UF and MF (Persico & Bazinet, 2018; Suwal, Doyen, & Bazinet, 2015), using conventional methods (hydrodynamic studies) or innovative characterization techniques (microscopic and spectroscopic analyses).

9.3

Membrane materials and modules

9.3.1 Materials Membrane materials are chosen considering their mechanical properties, chemical stability, and the MWCO they allow. Organic polymeric membranes. Most materials used in membrane separation processes are organic polymeric ones. Cellulose acetate was the primary polymer used for manufacturing hydrophilic organic membranes. With low cost and a large panel of pore sizes, it was used to prepare the MF, UF, NF, and RO membranes. Nevertheless, its limited resistance to temperature and pH (30 C
40 C, 3 , pH , 8) currently restricts applications to specific fields (drinking water). It can be advantageously replaced by polyacrylonitrile. For hydrophobic membranes, polysulfone, polyethersulfone, poly(vinylidene fluoride), polyamide, polypropylene, or polytetrafluoroethylene are generally encountered. Polyamide constitutes the active layer of more than 95% of RO membranes. Hydrophilic membranes are less prone to fouling than hydrophobic ones. Mineral membranes. The first mineral membranes derived from the nuclear technology (isotopic enrichment of uranium) and appeared in the laboratories for food applications in the 1970s. They were followed by ceramic membranes in the mid1980s. They are currently constituted of ultrathin metal oxide particles (ZrO2, TiO2, and Al2O3) fixed on macroporous metal, carbon, or ceramic supports. Due to manufacturing limitations, they are essentially available for the MF and UF. They have outstanding thermal, chemical, and mechanical stability and long shelf life (up to 10 years, depending on applications and utilization). Being far more expensive than polymeric membranes (for 1 m2 installed the cost range is 2300
7500h for mineral ones compared with 300
750 for organic ones), their use is restricted to cases where their properties are necessary or to high added value productions. Besides, membrane-manufacturing processes are diverse and can lead either to isotropic or anisotropic materials (Fig. 9.10). Isotropic membranes present a homogeneous structure along their thickness. Most of them are microporous membranes. In order to increase membrane selectivity and maintain high water permeability the selective tight layer must be thin. Consequently, most of membranes are anisotropic: one face presents a high porosity to allow high permeability, and the other is tight and corresponds to the targeted cutoff. In addition, some membranes are composite: they are composed of one or two porous support layers, responsible of the mechanical properties of the material, and one selective layer that is very thin to preserve the highest possible permeabilities.

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Figure 9.10 Membrane material structures. Source: From Baker, R. W. (2012). Membrane technology and applications. Newark, CA: A John Wiley & Sons, Ltd., Publication.

9.3.2 Module geometries Membranes can adopt the form of flat sheets, tubular modules, hollow fibers, or spiral-wound modules. The main features of these different geometries are presented in Table 9.3. Tubular membranes are commonly used in food industry. Due to high compactness and low cost, spiral wound (Fig. 9.11) modules are also widely used in food industry although their cleaning may be questionable in some applications.

Table 9.3 Comparison between different industrial module types. Geometries Flat sheet

Spiral wound

Tubular

Hollow fiber

Membranes

Organic, disks, or rectangular sheets

Organic

Advantages

Flexibility; low energy consumption; good performances (flux); reusable membranes

Compactness; low dead volume; low energy consumption; low cost

Organic: monotubular. Mineral: mono- or multitubular systems Low fouling Easy cleaning Possible treatment of viscous mixtures

Drawbacks

Weak thermal resistance; fouling; high cost

Performances (flux); inadequate to high viscosity mixtures; low thermal resistance; important pressure drop; dead zones; fouling; difficult cleaning

Important dead volume High energy consumption High cost Weak thermal resistance of plastic components (org. membranes)

Organic with active layer inside or outside Compactness Low dead volume Low energy consumption Good mechanical properties Low cost Difficult treatment of viscous products Weak thermal resistance of plastic components Fouling

Source: From Daufin, G., Rene´, F., & Aimar, P. (1998). Les se´parations par membrane dans les proce´de´s de l’industrie alimentaire. Lavoisier Tec et Doc. Paris. 1998.

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Figure 9.11 Schematic representation of a spiral-wound membrane. Membrane is represented unfolded. Spacers on both feed side and permeate side are not represented. The flows (arrows) are in reality perpendicular to the plan of the figure. Feed flows parallel to the collecting tube, whereas permeate flows more or less helicoidally before rejoining it.

9.3.3 Innovations in material manufacturing Process performances can be improved by modifying polymers, materials, and module configurations. Innovations in polymer and material manufacturing result either from new combinations of existing materials or from new material conception. As an example of innovative material combinations, the UF PVDF (PolyVinyliDeneFluoride) membranes can be modified to improve their pHdependent response. The decrease of PVDF concentration and the addition of poly (ethylene glycol) methacrylate as copolymer were demonstrated to be efficient at a laboratory scale (Yang et al., 2017). The obtained material showed improved water flux and pH-dependent responses to bovine serum albumin (BSA) separation. Another example concerns cellulose acetate membranes that can be surface coated with chitin nanocrystals to obtain tailored surface characteristics (Goetz, Jalvo, Rosal, & Mathew, 2016). Typically, the obtained membranes present a superhydrophilic surface while the original material is rather hydrophobic. This structural modification also modifies the mechanical properties of the final material: it significantly improves the tensile strength and E-modulus but decreases the strain. The structural modification also induces a reduction of biofouling and improves the resistance to fouling by BSA or humic acid. Conceiving and designing new materials is a challenging strategy. Among the emerging materials, ultrafast molecular separation membranes are being investigated (Cheng et al., 2018). Innovations in nanoscience and nanotechnology help to formulate very thin selective layers. For example, high loads of carbon nanotubes in polymeric RO led to very thin films allowing high water permeabilities. In addition, the obtained materials show a high resistance to chlorine degradation, a main issue in RO membrane aging (Ortiz-Medina et al., 2018).

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Another structural parameter that modifies the permeate flux is membrane porosity. The development of inorganic nanotubes and nanofibers of few nanometers in diameter allows the design of high porosity membranes without modifying their pore sizes (cutoff) or mechanical properties. The addition of carbon nanotubes is, for example, tested in composite membranes. Another example of modified NF membranes consists in γ-Al2O3 hollow microspheres introduction into interlayers to improve water permeability (Fu et al., 2018). Finally, graphene oxide laminar membranes present a significantly higher resistance to organic solvents and are used in organic solvent mixtures treatment and desalination (Li, Cui, Japip, Thong, & Chung, 2018). Safety of materials in contact is critical for food applications. Manufacturing of membrane separation materials and modules must obey strict rules. No dead zones can be accepted in the module conception, because they favor microbial development. The modules must be easy to clean and even to sterilize in some cases. The used materials, adhesives, and containers must obey the legislation on food contact materials (Daufin, Rene´, & Aimar, 1998) (example of the legislation CE no. 1935/ 2004 for the European community).

9.3.4 Configurations Membrane implementation must fulfill several conditions that are sometimes contradictory: (1) ensure a high tangential velocity all along the membrane (in spite of the continuous extraction of permeate) and (2) maintain a sufficient TMP along the membrane, therefore, a low pressure drop, which may be contradictory with a high tangential velocity. Besides, other parameters have to be considered: energy consumption and membrane area should be minimized. The quality of the product (which can be impacted by residence time or shear rate) should be preserved. Membranes must be used in conditions that ensure a long shelf life: cleaning frequency and conditions have to be carefully selected.

9.3.4.1 Batch configuration Fig. 9.12A presents the simplest configuration that can be implemented, for example, in a concentration purpose. Retentate is recycled until the achievement of a given concentration factor FC (final concentration in the tank divided by initial concentration) or a given volume reduction ratio VRR (initial volume divided by final volume). FC and VRR are equal only in the case of a fully rejected solute. This system is suitable for small productions or pilot-scale experiments. However, to get high flowrate and high pressure a volumetric pump (expensive) is often necessary. Moreover, most pumping energy is lost through the return to the tank. Therefore a recycling loop is generally implemented: a part of the retentate is recycled back to the inlet of the membrane module through a second pump (Fig. 9.12B). This so-called circulation pump works under high flowrate and low pressure drop, whereas the feed pump works under low flowrate and high pressure.

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Figure 9.12 Batch filtration configuration: simple batch (A); with a recycling loop (B).

Figure 9.13 Fed-batch membrane separation configuration.

Apart from reducing the energy expense and allowing to control separately TMP and velocity, this system reduces the detrimental effects of fouling by allowing high velocities along the membrane. In the fed-batch variant the tank is fed continuously so that the volume remains constant (Fig. 9.13).

9.3.4.2 Continuous mode Continuous membrane separation device is the most relevant mode for industrialscale applications. The elementary configuration shown in Fig. 9.14A is typical of water desalination units by RO. In these applications where high water recovery yield are expected the retentate from the first stage becomes the feed to the second one, and so on, giving rise to pyramidal or so-called Christmas tree configuration. In the MF or UF applications, recycling loops are implemented (C) as discussed

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Figure 9.14 Continuous membrane separation device. Single pass (A); RO two-stage system (B); with recycling loop (C); with recycling loop and multistage (D). RO, Reverse osmosis.

earlier and generally organized in multistage devices (D), where the retentate is concentrated from stage to stage and permeate recovered at each stage. This strategy offers the possibility of adapting membrane area and module geometry to the characteristics of the retentate at each stage (flowrate and viscosity) and to minimize global membrane area. Due to an increased complexity the number of stages is generally limited to three. The global volume reduction ratio, VRR, of the installation is related to final retentate (R3 in Fig. 9.14): VRR 5

QF QR3 1 QP 5 QR3 QR3

(9.18)

9.3.4.3 Diafiltration Diafiltration is useful to purify two species, A completely rejected by the membrane (RA 5 1) and B nonrejected (RB 5 0). Indeed, A cannot be recovered purely in the retentate because B distributes equally between the permeate and the retentate; reversely, recovery of B in the permeate is poor due to the large quantity lost in the retentate. Diafiltration consists in replacing progressively the “lost” solvent in permeate by an equivalent volume of fresh solvent, generally water in food applications. In Fig. 9.15 where diafiltration is presented in the context of a batch configuration, this results in depleting the content of the tank from the non- or low rejected solute (B) without changing the concentration of the totally rejected solute (A). The content of the tank is called a diavolume (DV), and the amount of solvent added is often expressed in DVs. Diafiltration can be operated sequentially

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Figure 9.15 Diafiltration in batch configuration.

(the addition of a DV is followed by the extraction of an equivalent volume of permeate) or continuously (the volume in the tank does not change). Diafiltration can also be used within a continuous system as presented in Fig. 9.14. The main drawback of diafiltration is the high solvent consumption resulting in diluted permeate. It should therefore be restricted to the purification of a largely rejected solute and not to the recovery of nonrejected solutes. Countercurrent diafiltration, in multistage devices, can lead to a significant reduction of diafiltration solvent consumption (Lipnizki, Boelsmand, & Madsen, 2002). Considering Fig. 9.15, mass balance on the solute B is V0

dCF 5 2 QP CP dt

(9.19)

After integration and considering the definition of the retention rate the following relation is obtained: CR 5 C0 3 eð2Q 3 t 3 ð12RB ÞÞ=V0

(9.20)

where RB 5 0 (nonrejected solute): CR 5 C0 3 e2VD =V0 with VD 5 Q 3 t 5 pure solvent volume added during the operation. For example, with VD/V0 5 3 the concentration of the nonrejected solute is reduced by 95%.

9.3.5 Separation process performances enhancement techniques Temperature. For many viscous mixtures the higher the temperature, the lower the viscosity, and consequently, the better the mass transfer through the membrane. For

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this reason, many MF and UF operations in food industries are performed at 40 C
50 C (Atra, Vatai, Bekassy-Molnar, & Balint, 2005). There are limits to temperature increase: it can lead to a chemical modification of solutes (protein mixture gelation or precipitation), of membrane material [oxidation, swelling leading to ¨ stergren, 2008)]. It also increases selectivity modification (Nilsson, Tr¨aga˚rdh, & O the risk of microbial growth. Consequently, high temperature filtration processes cannot be performed for long times, and this can be avoided by increasing the total filtration surface area (Dewettinck & Trung Le, 2011). Cross-flow velocity. The increase of cross-flow velocity generally leads to the reduction of cake or surface gel formation, thanks to a better turbulence. For similar TMP values, higher cross-flow velocity leads to higher permeate flux. It can also contribute to shift the critical flux toward higher TMP. However, limiting the cake formation can lead to quicker internal fouling. In addition, in membrane bioreactor (MBR) applications, high cross-flow velocities can lead to cell disruption due to excessive shear rates. TMP. As shown in Fig. 9.6 permeate flux increases linearly with TMP until reaching first the critical flux and then the limiting flux. Generally, it is considered that between these two fluxes (Bacchin, 2004), there is a transition between local fouling phenomena to a general irreversible fouling of the membrane. It is generally accepted that the critical flux, which approximately corresponds to two-thirds of the limiting flux, is the optimum operating condition. The critical flux can correspond to very low TMP values, especially for micro- or ultrafiltered polydisperse suspensions, where internal adsorption can occur very quickly, at high cross-flow velocities (Dewettinck & Trung Le, 2011). Uniform TMP system (UTP). To limit fouling in the MF especially, it is sometimes necessary to maintain simultaneously a low TMP all along the module and a high tangential velocity. Suppliers have developed systems in which TMP is maintained constant by creating a pressure drop on the circuit of the permeate, equivalent to the pressure drop on the retentate side (Alfa Laval, APV). This pressure drop can be achieved, for example, by circulating the permeate through a pump. This is currently used in the Bactocatch milk debacterization process by the MF. However, these solutions lead to increase the operating and capital costs. Other solutions have been developed, where the mean porosity of the support increases progressively along the membrane in the direction of the flow (ceramic graded permeability modules) or where the thickness of the selective layer decreases along the membrane length (Dewettinck & Trung Le, 2011). Cross-flushing, backwashing, and backflushing. When the main fouling factor is the formation of a loose and noncompact cake, cross-flushing (the feed flow is maintained but the permeate is stopped) can efficiently remove particles deposited on membrane surface (typically microorganisms in the MF). When internal pore blocking is the main issue, backwashing and backflushing are useful (Fig. 9.16). The first consists in using pure solvent (water) to wash membrane from the permeate side to the retentate one. The second consists in reusing permeate applied in counter flux. These two methods need to be optimized for their frequency and the duration of each sequence (Kim et al., 2007). Besides the use of supplementary tubing and pumping

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Figure 9.16 Permeate flux improvement with regular backwashing.

devices, they decrease the effective production time. Backpulsing with very high frequencies (1 s21) and very short pulse duration (,1 s) is an interesting alternative. It is efficient for skimmed milk filtration for bacterial removal but is difficult to scale up because pressure pulses become less effective in long membrane modules (Brans, Schroe¨n, van der Sman, & Boom, 2004). Dynamic shear-enhanced membrane filtration. Increase shear rate is one of the most efficient factors for increasing permeate flux, by reducing both concentration polarization and fouling layer. Increasing tangential velocity leads to large pressure drop inside the module, with drawbacks already evoked. In dynamic shearenhanced membrane filtration, high shear rate is created either by rotating the membrane, or by vibrating it longitudinally or torsionally around a perpendicular axis, or by rotating a disk near the membrane, which is fixed and circular (Al-Akoum, Ding, Chotard-Ghodsnia, Jaffrin, & Ge´san-Guiziou, 2002; Chai, Ye, & Chen, 2017; Xie et al., 2018). Dynamic shear-enhanced membrane filtration was proved efficient for concentration and separation of milk proteins (Al-Akoum et al., 2002; Chai et al., 2017; Xie et al., 2018) and in many other cases such as protein recovery from dairy effluents, clarification of chicory juice (inuline). These systems are present in paper industry for the treatment of the effluents but there are, up to now, no industrial installations in food industry. Ultrasound. In dead-end laboratory scale filtration a probe placed above the membrane induces several phenomena such as cavitation, radiation pressure, or acoustic streaming (Kyllo¨nen, Pirkonen, & Nystro¨m, 2005), which help to remove polarization layer, cake layer, and internal fouling molecules. Electric-field assisting filtration. With flat sheet and tubular membranes the application of a constant or a pulsed electric field across the membrane can enhance

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Figure 9.17 Multistage membrane separation process for retentate concentration.

the process performances. The electric field is applied with a polarity such that the charged molecules are repulsed from the membrane surface (Huotari, Tr¨aga˚rdh, & Huisman, 1999). This method contributes to limit the concentration polarization and to maintain high permeate fluxes (Sarkar, DasGupta, & De, 2009). Air sparging. Sequential air sparging into the feed side of the membrane leads to a two-phase flow pattern in hollow fibers or tubular modules, which generally stabilizes annular flow (Cui, Chang, & Fane, 2003). Gas bubbles disintegrate the concentration polarization layer leading to an improvement of permeate flux, and a positive correlation is found between the bubble ratio to total flowrates and the critical flux (Wang, Fane, & Chew, 2017). This method is widely used in submerged MBR systems used in effluent treatment (Dewettinck & Trung Le, 2011) to enhance the permeate flux, prevent fouling, and in membrane cleaning. In MD, air sparging is also used in wetting prevention of membrane surface (Rezaei, David, John, Lienhard, & Samhaber, 2017). Multistage operations. In several cases, solutes must be fractionated progressively, with successive separation steps, for example, when the initial mixture contains solutes and/or particles of very different molecular weights, and when the interesting molecules are of intermediate or very small size. For mixtures with very high and very low molecular weights a single separation through a tight membrane leads to a quick flux decrease and fouling. Multistage processes are a good solution to overcome this problem. A fractionation after fermentation should therefore associate successively (1) the MF to remove cells, (2) the UF to retain proteins, and (3) the UF or NF with diafiltration to purify an intermediate molecular weight solute. Multistage systems can also be useful to concentrate progressively an interesting solute while minimizing fouling as shown in Fig. 9.17.

9.3.6 Membrane cleaning Cleaning is unavoidable when too high decrease of the flux is observed. The classical cleaning procedure consists in washing the membrane sequentially with base and acid. Its efficiency is measured by water flux recovery after cleaning, compared with its value before membrane use: Recovery ð%Þ 5

Jwater-after 3 100 Jwater-before

(9.21)

Flux recovery is generally lower than 100%. A higher value means that the membrane structure is degraded because of the cleaning procedure, for example, when excessive NaOH or KOH concentrations are used (Baker, 2012). Less

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sensitive to strong chemical treatments, inorganic membranes are more appropriate than organic ones for cleaning in place procedures. To avoid deeper pore blocking by the fouling molecules during the cleaning procedures, low TMP should be applied, with high cross-flow velocity. In addition to acid or base solutions used for chemical cleaning, detergents are used to improve cleaning efficiency (wettability) and enzymes to hydrolyze the high-molecular-weight fouling agents (mainly proteins and polyphenols) (Baker, 2012; Dewettinck & Trung Le, 2011). A special care must be taken to avoid membrane fouling by the used enzymes. The previously cited use of ultrasounds in membrane separation performance enhancement is also used to enhance cleaning efficiency (Luja´n-Facundo, ´ lvarez-Blanco, 2016). Mendoza-Roca, Cuartas-Uribe, & A

9.4

Membrane applications in food processing

9.4.1 Contribution and interest of membranes in the processes of food industry Whether in pressure-driven or electrically driven separation processes, membranes fundamentally split the feed into two fluxes (retentate and permeate, diluate and concentrate), according to the size (or the electrical charge) of the solutes with a possible modulation by physical
chemical interactions. Membranes can therefore ensure the main following functions: G

G

G

Purification (where permeate is the main target) Concentration/extraction (where retentate is the main target) Separation/fractionation (where both permeate and retentate are considered)

Based on these main functions, a very large panel of applications has been developed in the food industry, which is presented by typology in the following paragraph. In addition, it may be noted that membranes can also accomplish many other functions classically devoted to specific reactors, such as emulsification, phase contacting, crystallization (proteins), and support for catalysts in catalytic reactors. As an example, emulsification of one phase into another through a porous membrane can reach more homogeneous emulsions with lower dispersion of particle sizes that conventionally prepared ones with high stirring or high-pressure homogenizers (Alliod et al., 2018; Charcosset, 2009; Donsı` & Ferrari, 2016; Hancocks, Spyropoulos, & Norton, 2016; Ili´c et al., 2017; Silva, Starov, & Holdich, 2017; Spyropoulosa, Hancocks, & Norton, 2011). Since decades, dairy industry has been pioneer among the food industries for the use of membrane technologies in transformation processes as well as in effluent recycling and by-product valorization and is an incomparable source of examples (Fig. 9.18). Membranes can replace existing unit operations with many benefits: they are continuous operations; they do not involve the use of chemicals or process aids

Membrane separation in food processing

Water removal (evaporation)

269

Control over bacteria (heating)

Centrifugal separation (skimming)

Demineralization (electrodialysis)

Alternatives to unit operations

Removing spores from skimmilk and whey

UF-cheeses

Defatting whey

Resolving separation issues

Removing casein micelles from milk

Creating new products

Extended shelf life milk (ESL) Beverages (UF-permeate)

Extracting whey Proteins (WPCs)

Fermented milks

Separating proteins/peptides Recycling brine and cleaning solutions

Textured milk products

Figure 9.18 Membrane processes in the dairy industry: a look at the applications. Source: From Pouliot, Y. (2008). Membrane processes in dairy technology—From a simple idea to worldwide panacea. International Dairy Journal, 18, 735
740.

such as regenerants and coagulants; they operate at low temperature (even if increasing temperature has favorable influence on performances) and do not involve phase changes; they lead to simplifications in the process schemes (reduction of the number of operations). As a consequence, membrane technologies often prove competitive at different levels: product quality, environmental impact, energy consumption, and productivity. Their modularity and flexibility allows them to integrate more or less intimately with other operations, to obtain more selective processes, for example, ED with the UF membranes (EDUF) for the separation of bioactive peptides or ED with resinfilled compartment (electrodeionization) to produce ultrapure water. Most often, substituting a traditional operation by a membrane, one may lead to more or less substantial product modification. In food processing indeed, small changes can induce great effects, as illustrated by the emblematic example of the Maubois, Mocquot, Vassal (MMV) process, where the introduction of the UF in cheese manufacturing led to completely reverse the traditional sequence from (coagulation 1 draining) to (UF draining 1 coagulation). Moreover, the retention of whey proteins in the cheese deeply changed its characteristics and led to the

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development of several dozens of novel cheeses, different from traditional products. Microfiltered milk may also be considered a novel product, although it is drinking milk, with organoleptic and nutritional properties very different from thermally debacterized milk. If, in the early stages of the development of membranes, the modifications of the products were observed a posteriori, a better understanding of the role of membranes and their interactions with food composition, thanks to decades of experience, could now lead to tailor-cut products through a reverse engineering approach. At last a fast-growing field of application is the treatment of wastewaters. The food industry is especially concerned: water withdrawal for heat, mass, and momentum transfer and for cleaning operations reaches about 400 million m3/year, namely, 23% of manufacturing industry. Even if the implementation of cleaner processes tends to decrease water consumption and the production of waste, effluents are still a major issue in the actual context (global warming, scarcity of water resource, demography, etc.). Beyond conformance with existing regulations the objective of wastewater treatment is the recovery of water or solutions (brines, cleaning solutions, etc.) for recycling or reuse in the process and possibly recovery of raw material. However, industrial applications in this field are still limited by fluxes, and the capital and running cost of the membrane technology.

9.4.2 Purification Purification covers different types of applications depending on the technology, the type of membrane, and the solution processed. The objective is to remove compounds or solutes that affect or alter the aspect of the solution (bio/chemical stabilization), its organoleptic, nutritional or functional properties, or that could lead to an alteration of the product over time and adversely affect its conservation (microbial stabilization). It can also concern the correction of composition to comply with regulations or to remove species detrimental for downstream operations (demineralization, softening). The applications cited here concern with aqueous media. The interest for nonaqueous media is recent: membrane technologies (NF and UF) have been applied to vegetal oil processing (Nath, Dave, & Patel, 2018) (degumming, deacidification, and pigment removal): despite the relatively high cost of appropriate devices, they seem to be good alternatives, in terms of human health and environment preservation, to conventional treatments that use toxic organic solvents or involve energy consuming distillation steps.

9.4.2.1 Biochemical/chemical stabilization A classic example is the clarification of apple juice. The MF with mineral membranes eliminate particles and macro-solutes responsible for the turbidity and replace a succession of traditional unit operations, including enzymatic depectinization, fining, decantation, prefiltration on diatomaceous earth, final filtration on cellulose sheet, before bottling and pasteurization. The MF simplifies definitely the

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whole process and avoids the use of consumable and the production of wastes. Processing time is reduced, which is also beneficial in terms of hygiene. Other beverages such as cider are now industrially processed in the same way. For fruit juices with higher content in pulp particles a satisfactory clarification is obtained by the MF. Lemon juice stabilization is obtained through 0.2 μm membranes (Vaillant et al., 2005). In addition, enzymatic treatment can be applied before filtration to remove high-molecular-weight cellulose and hemicelluloses that are responsible for the viscosity modification of fruit juices (Baker, 2012). These polysaccharides are hydrolyzed using cellulases. The resulting juices have lower viscosities and are consequently easier to treat with a membrane technology (Vaillant et al., 2005). In brewery, fermentation tank bottoms represent around 2% of the total tank volume and contain a high amount of rough beer that can be recovered after clarification by the MF (Lipnizki, 2017), allowing the total productivity to be increased with only modest investment. During the production of glucose syrups from wheat or corn starch hydrolysis, macromolecules remain in solution. They are eliminated by mineral membranes with an MWCO at the limit of the UF and the MF (300 kg/mol) at 70 C in multistage plants. After diafiltration a VRR of about 25 is achieved. In beet sugar industry, sugar juice clarification is achieved through a complex and expensive clarification process associating several steps of liming, carbonation, and filtration or decantation. The attempts to replace this system by membranes gave interesting results but never resulted in industrial application. In cane sugar industry, where traditional clarification is rudimentary (liming and decantation), the juice still contains high-molecular-weight impurities such as dextran, starch, wax, gums, and coloring matters. New Applexion Process, in operation from 1994 to 1998 in Maui (Hawaii), consisted in completing clarification with the UF and possibly a decalcification stage, allowing the crystallization yield to be increased, brown sugar quality to be improved, and the possibility of latter producing white sugar at the sugar factory, a small revolution in this sector. Studies were also undertaken to simplify the cane sugar refinery process, which is rather complicated although impurities to remove represent only a few percentages. The MF was proved sufficient to eliminate turbidity. The UF at 300 kg/mol combined with flocculation allowed to reduce coloring matters up to 50% and turbidity up to 90% with permeate fluxes of about 65 L/h/m2 (Cartier, The´oleyre, & Decloux, 1996). A remarkable example of chemical stabilization concerns tartaric stabilization of red wines by ED. Grapes naturally contain potassium hydrogen tartrate which solubility decreases with alcohol increase during fermentation, leading to salt precipitation during storage. ED can be used to remove up to 14.5% ions and 11% of tartaric acid, leading to a stable product at 0 C (Gonc¸alves, Fernandes, dos Santos, & de Pinho, 2003). It represents an efficient and cost-effective alternative to the traditional treatment (several days cooling at 24 C before filtration). The energy consumption is 0.5
1 kW h/hL of wine, and the cost of the treatment is 25%
45% lower than the traditional one. The process was patented in 1993 by INRA (France) but it needed several years of development before obtaining agreements from EU in

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2001 and further by the FDA and spread in all wine-making countries. In 2008 more than a hundred of installations were in operation in Europe, the United States, South America, Australia, etc.

9.4.2.2 Microbial stabilization Milk cold (20 C
50 C) stabilization with the MF, also called “Bactocatch” process, allows to reach less than 30 UFC/mL for mesophilic microorganisms, without significant change in milk composition (Ge´san-Guiziou, 2010; Pouliot, 2008). This is more efficient than thermal pasteurization processes and preserves the nutritional factors. Mineral membranes are used, with 1.4 μm pore diameter so as to let casein micelles go through. High tangential velocity (8 m/s) and low UTP (0.4 bar) are obtained, thanks to the recirculation of the permeate. Retentate represents less than 5% of the volume processed (VRR . 20). It can be reused for cheese making after thermal treatment or recycled in the centrifuge at the early skimming stage of the process. Microbial stabilization of beer can be ensured by the MF after fermentation (Daufin et al., 2001). This technology is also used for wine stabilization after fermentation (Lipnizki, 2017). Stabilization and clarification by the MF often lead simultaneously to remove microorganisms, reducing the process effect on nutritional and organoleptic product properties (Hongvaleerat, Lourdes, Dornier, Reynes, & Ningsanond, 2008; Polidori, Dhuique-Mayer, & Dornier, 2018; Vaillant et al., 2005) and representing a good alternative to heat pasteurization and sterilization.

9.4.2.3 Composition correction 9.4.2.3.1 Demineralization Less polluting, ED currently replaces IE for demineralization. In whey powder industry, salts representing around 20% of whey dry matter (DM) can impede lactose crystallization and hinder the drying process. ED is implemented on threefold concentrated whey (DM up to 18%
23%) to get sufficient conductivity. Demineralization up to 70% is possible. To reach higher level ( . 90%) and eliminate calcium phosphate and citrate, ED should be completed by IE. Comparing effluents from ED and EI, the volume and the concentration of ashes are 3 times and 4.5 times lower in ED, respectively. The ED avoids the consumption of 36 kg of pure acid and base per m3 of whey processed. Energy consumption is higher by 30% with ED; however, taking into account the energy needed for producing acid and base, the ED solution was shown to be four times less energy consuming than IE (Greiter et al., 2002). On nonconcentrated whey (6% DM), partial demineralization (calcium is not removed) and simultaneous concentration (Daufin et al., 2001) can be achieved by NF combined to diafiltration at lower investment and running costs than ED. A demineralization rate of 72% can be reached with tight NF membranes (300 g/mol), and no significant lactose loss is observed (Pan, Song, Wang, & Cao, 2011). This treatment facilitates further protein and lactose fractionation and purification.

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Partial demineralization by ED is also used in many other sectors, such as the stabilization of grape juices before thermal concentration, to avoid crystallization issues in the evaporator.

9.4.2.3.2 pH adjustment pH adjustment (acidification, deacidification) without the addition of salts is traditionally achieved by IE. For the deacidification of acid fruit juices, anionic resins allow citrate to be exchanged with OH2. After saturation, resin is regenerated with NaOH, liberating sodium citrate. BM ED allows the same operation to be achieved without any of the drawbacks associated with regeneration (use of chemicals, rinsing steps, and release of sodium) (Vera et al., 2003). Conventional or bipolar ED is also used to deacidify whey fractions that may contain too high amounts of lactic acid making it difficult to use them as food additives, in addition to process alteration due to salts (Dufton, Mikhaylin, Gaaloul, & Bazinet, 2018). Demineralization and deacidification are achieved simultaneously.

9.4.2.3.3 Dealcoholization The reduction of alcohol content in red wines was first tested with heat-based processes. However, many aroma compounds are lost by evaporation. To overcome this drawback, alcohol reduction can be experienced with NF technology using very tight NF membranes (150
300 g/mol MWCO). In Catarino and Mendes (2011), authors present an ethanol removal from 12% (v/v) wine to obtain final product with less than 7%
8% of alcohol content, using an NF process in semicontinuous mode with retentate recycling. Nonetheless, del Olmo, Blanco, Palacio, Pra´danos, and Herna´ndez (2014) and Catarino and Mendes (2011) suggest to use first a pervaporation step to recover aroma compounds before dealcoholizing, and to add the latter back at the end of process for wine and beer dealcoholizing. In the brewing sector, around 2% of the total beer production consists in lowalcohol products or alcohol-free ones. These products can be obtained by RO treatment of beer (Lipnizki, 2017). The obtained products have alcohol contents as low as 0.5% (v/v) but their flavor needs to be corrected by the addition of hops or syrups.

9.4.2.3.4 Other composition correction In wine production the modification of sugar and tannins content of must by RO is allowed as far as the modification is lower than 20% of the initial must (Lipnizki, 2017).

9.4.3 Concentration/extraction The use of membranes for concentration is particularly interesting when the solution or the compounds to recover are sensible to heat or to chemical precipitation (by pH or ionic strength change). Membranes have therefore undergone a spectacular development for the concentration of proteins, whether milk, whey, or even egg proteins, where the preservation of the nutritional and functional properties is crucial. Milk and whey protein concentration are the main and oldest applications (Madoumier, Azzaro-Pantel, Tanguy, & Ge´san-Guiziou, 2015; Masotti, Cattaneo,

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Stuknyt˙e, & De Noni, 2017; Nath et al., 2018; Pouliot, 2008; Wang, Wang, Li, & Tang, 2017). Depending on the membrane process, a variety of applications and new products have been developed and are currently produced at industrial scale. The MF (0.1 μm) is used for the concentration of native phosphocaseinates to be incorporated in cheese manufacturing. The debacterized and defatted whey resulting from the MF is considered the source of the best whey powders. Milk preconcentration by the UF covers a large range of applications, from standardization (1.8 , VRR , 4) of milk in proteins (either drinking milk or milk for cheese manufacturing) to the obtention of a real liquid precheese: the MMV process that was developed in 1969 (Maubois, Mocquot, & Vassal, 1969) made it possible to concentrate milk proteins (caseins and whey proteins) until VRR 5 7 with an MWCO of 10
15 kg/mol, improving spectacularly cheese manufacture performances: mass yield was increased by 20%, rennet by 80%, and the net gain represented 8% of the value of the milk processed. In 2016 600,000 t of cheese in the world were manufactured by this process. Concentration by the UF (MWCO 150 kg/mol) of coagulated milk at VRR between 3 and 7 was found to produce fresh cheese with a smoother texture than the traditional process by centrifugation and to improve the yield of between 3% and 25%; 80% of the fresh cheese produced in the world are based on this technology (Aimar & Daufin, 2004). Thanks to membrane technology, whey turned from a waste in the 1960s to the raw material of a new industrial and beneficial sector. Whey proteins can be concentrated by the UF and incorporated in cheese manufacturing. Through a cascade of membranes from the MF to NF, they can also produce whey protein concentrates with high purity (up to 80%
90%) for various diets and lactose (Fig. 9.19) (Daufin et al., 2001). At last the permeate of NF can be reused as process water after an RO final stage.

Figure 9.19 A schematic representation of the role of membranes in the production of WPC. WPC, Whey protein concentrates.

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Many other protein-containing products, whether they are of animal or vegetal origin, are concentrated by membrane, such as egg products (the whole egg and the egg white are concentrated industrially by the UF), or in the vegetal sector, the proteins of soya or alfalfa. The concentration of liquid foods (Sant’Anna, Marczak, & Tessaro, 2012) can be performed using membrane technologies as alternatives to evaporation and distillation. With energy consumption (in kWh/t of water or permeate removed) of 3.5, 5
7, and 9 for the UF, NF, and RO, respectively, membranes are competitive with evapoconcentration (around 100 for a 5-effect plant or 10
20 if equipped of mechanical vapor compression) and avoid the effects of thermal degradation such as browning, for example, when concentrating sucrose, fructose, or glucose syrups. The limit for concentration is the viscosity of the solutions and the osmotic pressure. Therefore membranes are preferably considered for preconcentration before evapo-concentration or drying. Not limited by osmotic pressure, OE, at room temperature, allows DM content up to 60% to be achieved. It is studied for concentrating sucrose solutions (Courel, Dornier, Herry, Rios, & Reynes, 2000) or fruit juices. In this latter case, it was proved to better preserve the sensory quality of the product than evapo-concentration. However, evaporation fluxes remain low and show a marked decay at DM content exceeding 45%. Therefore combined processes associating the RO (or NF) with OE have recently been proposed (Bhattacharjee, Saxena, & Dutta, 2017; Cisse´ et al., 2011). MD crystallization (Motuzas et al., 2018) is applied for concentrated solutions such as brine, where solvent can be evaporated in contact with a solid and generally hydrophobic membrane. This leads to a retentate composed of a supersaturated solution where crystallization can occur and a permeate consisting in pure solvent. As in MD, a solvent vapor pressure gradient is applied across the membrane to ensure the transfer. This technique presents many advantages: it allows separating solvents and solutes with low TMPs; the different solutes present in the same initial solution generally have different solubility and can thus be crystallized and purified sequentially. Depending on flowrates and temperatures of feed and permeate, size and morphology of crystals can be controlled (Chen, Lu, Krantz, Wang, & Fane, 2014).

9.4.4 Separation and integrated processes Fundamentally, pressure-driven membrane technologies split a flow into two fluxes. Separation or fractionation in several constituents with adequate purity, recovery, and concentration involves therefore a cascade of membranes with different MWCO, often associated with diafiltration steps, as already illustrated in Fig. 9.19 in the case of whey fractionation. Together with whey, milk industry is also pioneer in ingredient fractionation by membrane technologies. Fig. 9.20 presents the different fractions that can be obtained by pressure-driven membrane technologies from whole milk. Apart from the different applications already evoked, recent fractionation of milk fat by the MF allowed to separate fractions of fat globules of different sizes in the retentate and in the permeate. Incorporating these fractions in dairy products allows interesting textural characteristics to be achieved.

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Figure 9.20 Milk component fractionation with pressure-driven membrane technologies.

Diverse functional fractions are also purified from fruits and vegetables. They are further used as food ingredients or nutraceuticals. For example, phenolic compounds, such as tannins, anthocyanins, or flavonoids, can be isolated from fruits such as berries. Classically, these compounds are obtained by solid
liquid or solid
liquid extraction, depending on raw material (must, clarified juice). Membrane technologies present the advantage of avoiding the use of polluting and toxic solvents. In Conidi, Drioli, and Cassano (2017), authors present the different applications of membrane technologies for the recovery of polyphenolic compounds from raw vegetal materials or food industry by-products. For example, polymeric phenolic compounds are concentrated from grapes in the retentate of UF membranes of MWCO of 100 kg/mol, while low-molecular-weight fractions are recovered in permeate. Winery effluents and sludges can also be valorized as they contain important residual amounts of antioxidants and polyphenols. Pomegranate juice can also be ultrafiltered or nanofiltered, eventually with a diafiltration step, to separate phenolic compounds from sugars and obtained antioxidant fractions (Conidi, Cassano, Caiazzo, & Drioli, 2017). As an example of by-product valorization, phenolic compounds can be recovered by pressure-driven membrane technologies from olive mill wastewaters (OMWs). In these processes, pH control (at acidic values) is overriding to avoid the oxidation of antioxidant phenolic compounds. The MWCO of the used membranes is often in the UF range (10
25 kg/mol) to recover polymeric fractions from OMWs. Dense membranes are used for the fractionation/concentration/purification of already prepared extracts, generally hydroalcoholic ones. They are also used to recover and reuse the extraction solvents (Conidi et al., 2017). To improve selectivity, separation or fractionation can also be obtained by the association of membranes with either other membrane technologies such as ED or more highly selective technologies such as chromatography. The so-called EDUF process (Bazinet, 2005) based on the integration of UF membranes and EI membranes within a stack in an electric field allows to improve the separation of peptides obtained from the hydrolysis of proteins and to produce fractions enriched in target peptides with controlled biological properties. By associating the two types of membranes the selectivity of the separation is improved.

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In fermentation industries, new processes integrating membranes are proposed to separate the organic acids from the broth and purify them. Organic acids have already many applications in the food industry as acidulants, taste enhancers, or preservatives, and in pharmaceutical industry, and they are promising alternatives as chemical platforms or building blocks to molecules obtained from fossil resources. After a first clarification operation that can be achieved by the MF or UF (instead of centrifugation) a two-step ED associating conventional ED and BM ED allows the organic salt to be separated from the clarified broth and converted to the corresponding acid (Bailly et al., 2001; Lameloise & Lewandowski, 2012; Roux-de Balmann et al., 2002). Further processing by IE chromatography allows the residual salts to be removed to achieve the required purity. Compared with the main traditional process based on the precipitation of the organic salts with Ca(OH)2, followed by their acidification with sulfuric acid, which consumes reactants and overall releases large amounts of CaSO4 in the environment, these novel strategies minimize the waste. Moreover, NaOH or KOH produced during the ED with BM (BMED) step are recycled in the fermentation medium for pH control. According to Lutin and Roux-de-Balmann (2010), this covers completely the running cost of the BMED step. Several industrial units have been installed in the past two decades, and growing development is expected.

9.4.5 Effluent treatment 9.4.5.1 Effluent treatment before discharging Membrane technologies are particularly suitable to remove contaminants such as heavy metals and nonbiodegradable pollutants removal (Le & Nunes, 2016). A special issue concerns the removal of emerging contaminants such as trace organic contaminants (Rodriguez-Narvaez, Peralta-Hernandez, Goonetilleke, & Bandala, 2017), pharmaceuticals, mycotoxins, and pesticides (Li, Luo, Fan, Chen, & Wan, 2018), in particular because most of them are not biologically degradable. The food industry effluents are not concerned by pharmaceuticals but mainly by mycotoxins and pesticides. They remain not degraded after biological treatments: either in the liquid phase or accumulated without metabolization into biomass. For the remaining soluble contaminants, NF and RO are demonstrated to be efficient as posttreatments (Rodriguez-Narvaez et al., 2017). Similar issue concerns phosphorus residues after biological treatments. Phosphorus removal is challenging because its excess in aqueous ecosystems could result in eutrophication thus decrease in dissolved oxygen. RO proved successful for phosphorus removal (Nir, Sengpiel, & Wessling, 2018). OMWs are currently considered relatively recalcitrant effluents. Actually, they contain high amounts of phenolic compounds, bioactive but generally phytotoxic. Many studies investigate the possibility of their treatment in MBRs (see next) and with fine membrane technologies (UF, NF) but they face real difficulties due to membrane fouling, pretreatment issues, and process economics (Gebreyohannes, Mazzei, & Giorno, 2016; La Scalia, Micale, Cannizzaro, & Marra, 2017; Silvan, Pinto-Bustillos, Va´squez-Ponce, Prodanov, & Martinez-Rodriguez, 2018).

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In the refining process of vegetable oils the neutralization process releases very acid wastewaters (soap stocks) with pH around 1. Physical pretreatment by decantation or dissolved air flotation may be not efficient enough to remove all the fats, and this severely impedes the subsequent biological treatment (poor degradability, foaming). Interposing the MF between the physical and the biological steps was shown to enhance the recovery of fats in the retentate and reduce the fat load sent to the biological station without using chemicals (Decloux et al., 2007). Ceramic membranes with pore size from 0.2 to 1.4 μm were tested at very low TMP pressure maintained through a UTP system. With a 0.5 μm membrane, at 60 C and VRR values between 10 and 30, it was possible to maintain a permeate flux of 100 L/h/m2 and achieve a reduction of 91% of suspended solids, 96% of fats, and more than 60% of chemical oxygen demand (COD). In this application, it was hypothesized that fat retention by the MF was a matter of chemical affinity more than a pure steric retention. When effluents contain a significant ratio of biodegradable and not valuable organic compounds, MBR treatment could appear as the most suitable process. MBR is used in industrial effluent treatment since few decades. It consists in coupling conventional biological degradation of the organic pollution with a membrane separation to separate microorganisms and recover clarified water. This process presents many advantages: withholding all biomass and suspended solids ensures a high-quality treated water and a relative stability of the process. In addition, the biodegradation is more efficient since microorganism concentration in MBR systems is four to five times higher than in conventional aerated tank. It also allows to make very compact devices when compared with conventional clarifiers (Chen, Jiang, & Li, 2018; Tang et al., 2017; Zhu, Li, Zheng, Liu, & Chen, 2017). Treating wastewaters before discharging into municipal treatment stations allows the eco-compatibility of industrial processes to be improved. Beyond this, wastewaters could be considered resources and not merely as effluents: resource of water to be reused into the production processes after an adapted treatment and resource of valuable solutes.

9.4.5.2 Effluent treatment to allow water (or solutions) recycling into processes Membrane technologies are suitable to apply a rapid and simple treatment for cleaning and washing waters that can be recycled internally. The treated waters can have two outcomes: recycling into production process (food contact) or reuse for equipment washing, depending on their quality and on regulation rules. In dairy industry, heat treatment and cleaning in place are responsible for between 50% and 95% of the effluents produced (Daufin et al., 2001). Consequently, in the last two decades, dairy industries developed an efficient strategy of water treatment and recycling within small loops (effluent treatment before external treatment plant, after each concerned operation), for example, RO treatment of evaporation condensates, NF regeneration of alkaline, and acid cleaning solutions (Daufin et al., 2001).

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In malt industry, barley steeping is the main effluent generating operation. MBR treatment completed with an NF step was proved to produce water reusable into the malting process (Guiga, Fick, Ouarnier, & Boivin, 2007). In starch industry, steep waters can be evaporated, and the condensates treated by RO are used as boiler water.

9.4.5.2.1 Condensates Thermal concentration is often used to treat fluxes with high COD, such as stillage in distillery or whey in cheese making industry. It allows to decrease the volume in order to find better valorization to DM and to produce water as condensates. The quality of condensates depends on the characteristics of the concentration unit and of the feed. Generally, they cannot be reused as process water unless further purification treatments such as membranes treatment are applied. In beet distilleries, condensates arising from the concentration of stillage represent the most important amount of generated effluents. Their recycling as dilution water would drastically reduce the need for ground water and represent a smart alternative to the extensive and costly management of the condensates by lagooning and manuring (1.5
2 h/m3). Condensates contain various organic compounds which were proved to inhibit fermentation: carboxylic acids (especially acetic acid), furan derivatives, and phenolic compounds. RO possibly coupled with EI was demonstrated to remove them efficiently (Couallier, Payot, Bertin, & Lameloise, 2006; Lameloise, Gavach, Bouix, & Fargues, 2015; Sagne, Fargues, Lewandowski, Lameloise, & Decloux, 2008). Phosphorus removal from biologically treated effluents results in reusable water either in production process or in the cooling
heating loops. In addition, when phosphorus amount in effluents is high, this allows the regeneration of phosphorus as a nonrenewable resource (fertilizer) (Nir et al., 2018).

9.4.5.2.2 Brines In cane sugar refinery, anion-exchange resins are often preferred to traditional black carbon or even granulated active carbon to ensure the ultimate syrup decoloring step before crystallization. However, resin regeneration with NaCl 10% produces colored brines very difficult to handle. The NF brought a smart solution to this issue by allowing to remove the coloring matters from the brine. A first unit with lowcost spiral-wound membrane was installed in 1997 in Marseille refinery (St. Louis Sucre) with the purpose of recovering brine and recycle it directly. The most concentrated fraction of the brine was processed, containing 93% of the total NaCl and 50% of the total COD. Associating NF and diafiltration, it was possible to recover 98% of the NaCl of the treated fraction (i.e., 91% of total NaCl) and to concentrate 95% of the coloring matter in 3%
4% (discarded) of the volume of the treated fraction (Cartier, Theoleyre, & Decloux, 1997). In other plants the whole brine was nanofiltered, and a concentration step allowed the concentration of the brine to be adjusted for recycling. In these units where the retentate was mixed to the refinery molasses the decoloring process did not produce any waste. Glucose syrups produced in wheat or corn starch industry undergo demineralization through IE. Regeneration with HCl and NaOH generates effluents containing

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Figure 9.21 Production of acid and base from a saline effluent (regeneration of resins) by a combined process using bipolar membrane electrodialysis (BMED).

mostly NaCl, among other salts. Based on BMED, a solution was brought to the difficult problem of their management, by converting NaCl into HCl and NaOH (Fig. 9.21). To get rid of divalent cations and bring the brine at a convenient concentration, BMED was preceded by a first conventional electrodialysis and a chelating resin. Acid and base generated could ensure 96% of the needs of chemicals for regeneration, and global pollution was decreased by 73%. The extra cost due to energy consumption was proved to be counterbalanced by the economy on chemicals (Gonin, Lutin, Lameloise, Sandeaux, & Gavach, 1999). The process is currently being implemented at industrial scale.

9.4.5.3 Effluent treatment for by-product valorization In addition to water recovery from effluents after membrane treatment, valuable organic compounds contained in the retentate can be recovered and valorized: organic acids, phenolic compounds, sugars, peptides, and aroma compounds. Many food industries are concerned, in addition to the pioneer dairy and whey industry (proteins, lactic acid, lactose, and salts) (Atra et al., 2005; Daufin et al., 2001; Dufton et al., 2018; Pan et al., 2011; Wang et al., 2017). In dairy industry, starting and interrupting procedures can result in the loss of 1%
3% of raw material. This produces diluted effluents containing milk proteins and lactose. Balannec, Ge´sanGuiziou, Chaufer, Rabiller-Baudry, and Daufin (2002) demonstrated the efficiency of RO/NF for recovering these components in the retentate while the permeate consisted in a partially purified water, reusable for vessel washing steps.

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Figure 9.22 Water as a multiple resource: example of a multistage process to recover polyphenols and polysaccharides from winery effluents and water reuse. Source: Adapted from Giacobbo, A., Meneguzzi, A., Bernardes, A. M., & de Pinho, M. N. (2017). Pressure-driven membrane processes for the recovery of antioxidant compounds from winery effluents. Journal of Cleaner Production, 155, 172
178.

Seafood processing plants reject large amounts of polluting cooking juices that could be a source of natural flavoring compounds sought after by flavor industry. Recovering these compounds concentrated enough to be incorporated at 2%
3% in food preparations and with sensorial characteristics matching the expectancies is not straightforward, and the presence of a high salt load is a real difficulty. The concentration of shrimp cooking juice by RO after a first desalination step by ED (to decrease the osmotic pressure) was proved to give a concentrate with satisfying sensory quality while decreasing significantly the COD load of the juice (Cros, Lignot, Jaouen, & Bourseau, 2006). More recently, it was proposed to associate a preconcentration step by NF until a VRR of 10 and a final concentration by OE (Jarrault, Dornier, Labatut, Giampaoli, & Lameloise, 2017). Thanks to NF, the juice was partially concentrated and desalinated, allowing the further OE step to be run in optimal conditions: reduction of the quantity of water to be evaporated and of the production of brine, limitation of the loss of volatile compounds, and improvement of sensory acceptability. During OE step run at pilot scale a 52% DM concentrate was obtained with aroma loss lower than 35%. Winery effluents contain significant concentrations of colloidal matter, polysaccharides, and phenolic compounds exhibiting antioxidant activities and are thus interesting to be recovered with successive MF, UF, and NF separations as shown in Fig. 9.22 (Giacobbo, Meneguzzi, Bernardes, & de Pinho, 2017).

9.5

Conclusion

Integrating membrane technologies into the food industry, for food processing or effluent treatment and valorization globally, fits with green process conception criteria (van der Goot et al., 2016): adding value to by-products and effluents; recycling effluents; process intensification; and transition from pure ingredients to functional fractions. Dairy industry was a pioneer sector in integrating membrane technologies as green process operations. It was also pioneer in effluent treatment

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and recycling. Current and future developments of membrane technologies in food processes concern mainly: (1) their development in different production sectors and (2) their integration in process water reuse and recycling to minimize water consumption.

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Ili´c, J. D., Branislava, G. N., Petrovi´c, L. B., Koji´c, P. S., Lonˇcarevi´c, I. S., & Petrovi´c, J. S. (2017). The garlic (A. sativum L.) extracts food grade W1/O/W2 emulsions prepared by homogenization and stirred cell membrane emulsification. Journal of Food Engineering, 205, 1
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335. La Scalia, G., Micale, R., Cannizzaro, L., & Marra, F. P. (2017). A sustainable phenolic compound extraction system from olive oil mill wastewater. Journal of Cleaner Production, 142, 3782
3788. Lameloise, M.-L., Gavach, M., Bouix, M., & Fargues, C. (2015). Combining reverse osmosis and ion-exchange allows beet distillery condensates to be recycled as fermentable dilution water. Desalination, 363, 75
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Extrusion

10

Virginie Vandenbossche, Laure Candy, Philippe Evon, Antoine Rouilly and Pierre-Yves Pontalier Laboratory of Agro-Industrial Chemistry, Toulouse University, INRA, INPT, Toulouse, France

10.1

Introduction

Extrusion is a widely used process in the industry to produce foods with specific technological properties (color, texture, aroma, etc.). Its use dates back to the 1950s, mainly in extrusion cooking. Extrusion cooking is considered as a thermoplastic process, whose treatment is done at high temperature and with a short residence time. The mechanical action combined with the high temperature allows the modification of the internal structure of the matrix introduced and therefore its properties. Two types of extruders can be used, with different performance and capabilities, single-screw extruders, and twin-screw extruders. The mechanical treatment of the extruders can be carried out directly in the dry process, or by addition of solvents, and in this context, it is the twin-screw extrusion that is preferred. The twin-screw extruder is a tool that allows to work continuously in many different conditions, which has favored its use in very different fields such as the paper or the chemical industry. It is an instrument increasingly studied in the context of the biorefinery, since it allows the treatment of both green plants, such as alfalfa, and dry residues such as cakes or straw.

10.1.1 Extrusion The term “extrusion” hides a handful of different meanings according to the industrial sectors it refers. It originated however, from a forming process where a material is forced through a hole, the die, of a specific shape to produce all kinds of profiles, a pierced piston operating with a screw in a barrel. In the plastic industry, this technology has been widely used during the last decade and has greatly improved. For the processing of thermoplastics, the extrusion has become a lot more than a forming step and now includes many unitary operations: melting, devolatilizing, mixing, and dispersing (Rauwendaal, GonzalezNunez, & Rodrigue, 2017). For compounding operations, extruders can be considered now more as powerful continuous melt mixers used to add fillers (fibers, minerals, etc.) and additives (lubricants, antioxidants, etc.) to a polymer or eventually mix different kind of polymers. The final extrusion of strands to be pelletized Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00010-0 © 2019 Elsevier Inc. All rights reserved.

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Figure 10.1 Schematic representation of a twin-screw extruder, and unit operations conducted on the biomass during its processing.

through the die is only a final step and is conditioned by all the previous operations. When chemical reactions are involved, the extrusion is reactive and consists of a continuous chemical reactor used to graft or modify melted polymers (Beyer & Hopmann, 2018). A line has however been drawn between the extruders used to only melt and form a plastic through a die; these are usually mono-screw for a better transport and their barrel is full, and the extruders designed for formulation and chemical reaction purpose bearing two interpenetrating screws for a better mixing and shearing capacity, in which only certain zones are pressurized. For the processing of biomass, the range of applications is so wide that twinscrew extruders can be considered as thermal
mechanical
chemical continuous extractor/reactor, and the term extrusion refers to the processing with such twinscrew extruder. Regarding the complex structure and composition of the treated agricultural products and by-products, a destructuring dimension has to be added. The extruder operates as a high shear mixer able to disrupt the organization of cell walls, to “cook” storage polymers and consequently to extract some of the compounds or to shape a final product (Fig. 10.1).

10.1.2 Twin-screw extruder 10.1.2.1 Description A twin-screw extruder is composed of two rotative parallel shafts in a bilobed barrel. On these shafts, specific intermeshing identical screws are set according to the chosen configuration (Fig. 10.1). The barrel is heated and can be divided in different kinds of modules: open modules to introduce other liquid or solid material, closed and thermo-regulated or filtration modules equipped with a filtering mesh. Depending on the machine type, the shafts rotation is either in the same direction (corotating) or in the opposite (contrarotative). At the end of the barrel, die is often fitted to shape the extrudate; in the feed industry, the classical shape is a circular

Extrusion

291

strand to produce pellets, the number of holes depending on the output rate. The shapes can be more complex to produce the desired products.

10.1.2.2 The screw elements The different screw elements fitted on the shaft can have various shape, conformation, and actions (Table 10.1). The arrangement of successive screw elements depends on the unitary operation and mechanical treatment to be imposed to the treated biomass all along the screw profile. There are basically three kinds of screw elements: the direct pitch elements are used not only for transport but also for their self-cleaning and better dissociation capacity (multiple shafts), the mixing elements, mainly kneading disks (Martin, 2016), are used for distributive and dispersive mixing action, and the reverse screws are used to build pressure and apply a high shear on the treated material. The reverse screws are used mainly in extrusion cooking and to create a dynamic plug in liquid/solid extraction processes. The use of restrictive elements allows to increase the residence time in the extruder that range between 10 s to around 5 min, most process operating in the 30 s
2 min range.

10.1.2.3 Process control parameters The operating parameters controlled are mainly the screw speed (rpm), the various feed rates, the temperatures along the barrel, and eventually a vacuum level. The various readouts recorded during an extrusion experiment are the pressures (counter-pressure on the shaft and eventual pressure sensors in reverse screw zone or on the die), the temperatures (from the control of the heating devices or from specific flush temperature sensors) and the motor amperage. For all twin-screw extractor (TSE) experiments, the consumed energy is the sum of the specific mechanical energy (SME) and the specific thermal energy (STE) when the extruder barrel is cooled with water. The SME for all trials, in W h/kg, is calculated as follows: SME 5

I 3 U 3 N 3 0:95 S 3 Nmax

where I is the motor amperage (A), U the motor voltage, N is the screw speed (rpm), S the dry solid input rate (kg/h) and 0.95 is the gearbox efficiency. The STE, in W h/kg, is obtained from this equation: STE 5

d 3 Ceau 3 ΔT S 3 3600

where d is the cooling water flow rate (kg/h), Ceau is the specific heat capacity for water, S the dry solid input rate (kg/h) and ΔT the absolute value of the temperature difference of the cooling water between its input and its output.

Table 10.1 Characteristics of the most common screw elements used in twin-screw extractor.

Direct pitch screw elements

Mixing elements

Reverse screw elements

Denomination

Mixing

Shear

Transport

Remarks

T2S

1

1

11 1

C2S C3S C1S MD

1 1 11 11

1 11 1 11 1

11 11 11 1 Depend on angle

BD

11 1

11

Depend on angle

TD

1111

11

C2RS

1111

1111

Depend on angle


T1RS

1111

1111




C1RS

1111

1111 1




Nonself-cleaning Improve the input in the feeding zone Self-cleaning Self-cleaning Self-cleaning Higher shear than with bilobal Radial compression Residence time increase High mixing capacity Transport capacity depends on the angle between elements Residence time increase Higher mixing intensity Limited use on corotating intermeshing extruders High counter-pressure Residence time increase Dynamic plug formation for liquid/solid extraction High counter-pressure High shear Very high counter-pressure Residence time increase Dynamic plug formation for liquid/solid extraction

BD, Bilobal kneading disk; C1RS, single shaft conjugated reverse screw; C1S, conjugated single shaft; C2RS, double shaft conjugated reverse screw; C2S, conjugated double shaft; C3S, conjugated triple shaft; MD, monolobal kneading disk; T1RS, single shaft trapezoidal reverse screw; T2S, trapezoidal double shaft; TD, trilobal kneading disk.

Extrusion

10.2

293

Extrusion cooking

10.2.1 Process The dry or preconditioned material (between 15% and 30% moisture content) is introduced into the extruder through a screw feeder, in the feeding zone. In this zone, the screws, with a greater depth and pitch, has the main function of transportation and homogenizing of the raw material. This material is conducted from the feeding zone to the compression zones, where there is a consequent increase in shear rate, temperature (110 C
180 C) and pressure (20
30 bar) because of the reduction in screw depth and pitch. In this zone, the solid material starts to be converted to a fluid melt (Steel, Vernaza Leoro, Schmiele, Ferreira, & Chang, 2012). Thus, the extruded mass reaches maximum temperature and pressure and a reduction in viscosity immediately before exiting the extruder. The material is expelled through the die and expands to its final format when in contact with ambient pressure and is rapidly cooled through water flash-off. Before submitting to the drying process, moisture content should be close to 3% (Fellows, 2000). Lipids influence the extrusion cooking processes by acting as lubricants, because they reduce the friction between particles and the screw. In the extruder, fats and oils become liquid at temperatures above 40 C, being mixed with the other materials, and are rapidly dispersed as fine oil droplets (Guy, 2001; Steel et al., 2012).

10.2.2 Flours 10.2.2.1 Mechanisms Starch gelatinization occurs at much lower moisture contents (10%
25%) during extrusion processing than during conventional food processing. Thermoplastic extrusion causes swelling and rupture of the starch granule in conditions depending on the raw material composition. Amylose and amylopectin are partially hydrolyzed to maltodextrins, during thermoplastic extrusion, due to the high temperatures and shear inside the extruder (Steel et al., 2012). Water acts as a plasticizer for the starchy material that displaces itself within the extruder, reducing viscosity and mechanical energy, producing higher density products and inhibiting bubble growth (starch gelatinization is reduced with higher moisture, and therefore bubble growth is retarded, resulting in denser and less crunchy final products). The thermomechanical treatment on the starch granule and water content destroy the organized molecular structure, also resulting in molecular hydrolysis of the material. The starch polymers are then dispersed and degraded to form a continuous fluid melt. The water is retained as bubbles in the melt and stretches during extrudate expansion until the rupture of cell structure (Steel et al., 2012). The starch stiffens as it cools to stabilize the extrudate structure and finally becomes glassy as moisture is removed, forming a hard-brittle texture. The final extruded product is affected by the physical nature of the cereal flour. Soft flour will create less mechanical energy between its particles and require less

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mechanical energy to process through the same screw configuration. A longer time is necessary before melt formation which leaves less time for the transformation of the melt in the shearing section (high-pressure zone). In certain cereals, such as hard wheat, there is a strong bonding between the starch granules and the protein layers forming a hard particle of flour that requires more energy to break down and will generate more heat in the extruder (Steel et al., 2012). Instant precooked flours are cereal-based foods reduced to flours and are precooked. They are intended for instant dissolution with milk or water, to prepare a soup, a porridge, a porridge, or a cream. Recipes can incorporate other ingredients such as milk powder, sugar, minerals and vitamins, or salt or flavors. Extrusion gives all the characteristics required for these precooked flours: solubility of proteins, sensitivity of starches to amylases, or bioavailability of minerals.

10.2.2.2 Applications Extrusion makes it possible to make a very wide range of ready-to-eat cereals for breakfast or snack: directly extruded cereals, directly expanded, or stuffed.

10.2.2.2.1 Expanded cereals Expanded cereals are breakfast cereals with an airy, crisp, or crunchy texture. They can have very varied shapes (rings, balls, stars) with specific coatings and the integration of different tastes and many ingredients (inclusion visible or not) and can be transformed into cereal bars. The texturing and shaping of the expanded products is determined by the design of the final insert.

10.2.2.2.2 Snacks Twin-screw extrusion systems can process a wide range of raw materials to make expanded snacks. These can be shaped into different shapes and textured with many sweet or salty coatings. Inclusions of all kinds can also be added to enhance the taste and enrich the snack from a nutritional point of view. Filled snacks can be made on the same equipment with the addition of complementary modules.

10.2.3 Proteins 10.2.3.1 Mechanisms Protein texturization is one of the main applications of extrusion in high-protein content foods. Texturization processes by extrusion can be used to obtain products that imitate the texture, taste, and appearance of meat or seafood with high nutritional value. Disulfide bonds are cleaved during the extrusion and proteins undergo reorganization and polymerization (Areas, 1992). Texturization occurs between the molecules as they flow in the streamlines to form laminar cross-linked products. Evaporation of water in the mass creates gas bubbles that form alveolar structures held in place by cross-linking in the protein layers (Steel et al., 2012). In general, dry extrusion is applied when the aim is to produce meat extenders and wet extrusion is used for meat analogues. When the conditioned material passes

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through the die at a high temperature, the water in the material is changed into superheated steam, which expands the extrudate immediately. Low moisture (up to 35%) extrusion of vegetable protein can be used to elaborate products to partially or totally substitute meat. Usually, these products are expanded and need to be rehydrated before consumption (Guy, 2001; Steel et al., 2012). On the other hand, high moisture (.50%) extrusion results in products that do not need to be rehydrated and can be consumed directly. Extruded fiber proteins are extracted directly from plants such as soybeans or legumes. The raw materials undergo thermomechanical treatment at temperatures above 140 C and at high humidity levels (60%
80%). This process is also known today as wet extrusion cooking. The fibration (or texturing) is finalized in a long cooling system. Water also makes the extrudate very soft, by reducing its viscosity drastically, so the material just after the die is not self-supporting. Fiber materials produced using twinscrew extrusion technology are processed into cubes, slices, shredded pieces, or meat-like products. They are incorporated into prepared dishes such as vegetarian or vegan hams, sausages (Steel et al., 2012).

10.2.3.2 Applications Ingredients such as fishmeal, cereals, vegetable proteins are selected and crushed according to the specific requirements of the animals in terms of nutritional intake and pellet size. Particle size composition is a key factor in the manufacture of granules. Therefore, the grinding stage is an important operation of the unit. The powder is mixed with secondary ingredients, such as vitamins or mineral mixtures, before preconditioning. These parameters allow the production of granules with functional and nutritional properties such as apparent density or protein
lipid ratios adapted to the various aquatic species. The pellets can then be coated with oil and other additives and cooled to complete the process.

10.2.4 Other applications 10.2.4.1 Encapsulation The encapsulation or microencapsulation of flavors consists in coating an aromatic product or a mixture of molecules with a protective coating. The coat can also provide functional properties, such as a controlled release of the molecules in a specific medium such as water. Extrusion makes it possible to treat a wide variety of raw materials to produce aromatic compounds with high added value. The pulverulent matrix is first melted so as to obtain a homogeneous paste, and the aromatic products, generally in liquid form, are then introduced into a module of the sheath. The screw profile is adjusted so as to disperse these microdroplet liquids in the molten matrix and distribute them evenly throughout the mass. The molten aromatic paste is then pressed through a die to obtain a large number of threads which are cut directly using a granulator mounted at the end of the extruder. Extrusion encapsulated flavorings are used as ingredients in the food industry for

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applications such as quick desserts, pastries, and biscuits, but they are also used to encapsulate active ingredients for direct compression tablets and in cosmetics.

10.2.4.2 Food ingredients Food ingredients are intermediates used to modify foods and provide food-specific properties such as texture, fluidity, hydration, and taste. EPTTM (Extrusion Porosification Technology) is a process of texturing powders and increasing drying efficiency by accelerating mass and heat transfer. It can treat concentrates with a high solids content to produce porous and homogeneous powders with improved rehydration properties.

10.2.5 Mechanical fractionation Different treatments of lignocellulosic fibers have been developed during the last decades with different objectives: G

G

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Increase the digestibility of materials for use as fodder, Delignification of lignocellulosic fibers for the manufacture of pulp, Extraction and hydrolysis of hemicelluloses for the production of pentoses and their derivatives (xylitol, furfural, etc.), Increased accessibility of cellulose and its enzymatic digestibility for glucose production and ethanol fermentation.

The first treatments of lignocellulosic fibers in twin-screw extruders date from the late 1970s with the studies of De Choudens et al. (1987) who studied the treatment of wood chips for manufacturing of paper pulp. Since then, the twin-screw process has become a reference process for the production of refined pasta, for specialized uses such as fiduciary paper from annual plants. In parallel with this industrial transfer, the implementation of the twin-screw extruder for the fractionation of plant material has been studied for many applications with extruder configurations adapted to the type of treatment targeted (Rigal, 2000). In the case of woods, few studies in twin-screw extrusion processes have been conducted. The treatments mainly concerned the manufacture of cellulose pulp for the paper industry developed by Clextral for more than 30 years (De Choudens et al., 1987), the extraction of parietal polysaccharides from poplar (N’Diaye, Rigal, Larocque, & Vidal, 1996), the extraction of polyphenolic compounds and preenzymatic presaccharification pretreatments (Lee, Inoue, Teramoto, & Endo, 2010). Studies were also conducted on wood grinding for the manufacture of wood/ plastic composite (Hietala, Niinim¨aki, & Oksman, 2011) It is possible to obtain by this process fibers which allow a better reinforcement of the composites than with the wood flours more conventionally used (Hietala, 2011). Three parameters were studied during the study: the state of the incoming material, the screw speed, and the profile. The best results were obtained

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by adding a softening step of the fiber before introduction into the extruder (softening by soaking in boiling water 4 min or by sulfonation treatment of the fibers), by using high screw speeds, and by choosing the optimal screw profile inducing a mechanical treatment neither too low nor too hard. The addition of a second zone of reverse screw can lead to a reduction in the length of the fibers and thus lower the length/width ratio.

10.3

Expression

The twin-screw extrusion technology can also be used as a continuous press (Uitterhaegen & Evon, 2017), in particular for food applications. Different researches were recently conducted for extracting continuously edible vegetable oils using mechanical pressing, that is, without adding any solvent (Evon, Vandenbossche, Candy, Pontalier, & Rouilly, 2018). This was made from various oleaginous seeds, especially sunflower (Helianthus annuus L.) (Dufaure, Leyris, Rigal, & Mouloungui, 1999; Amalia Kartika, Pontalier, & Rigal, 2005, 2006; Evon, Vandenbossche, Pontalier, & Rigal, 2007, 2009) and coriander (Coriandrum sativum) (Uitterhaegen et al., 2015; Uitterhaegen, 2018). Industrial oil extraction from oilseeds is usually carried out by mechanical pressing with a hydraulic or single expeller press, followed by solvent extraction with n-hexane. The hydraulic press is highly effective for industrial extraction of oil from oilseeds by mechanical pressing, but it is a discontinuous process. Continuous oil extraction using a single-screw press is also widely used (Crowe, Johnson, & Wang, 2001; Isobe, Zuber, Uemura, & Noguchi, 1992; Singh, Wiesenborn, Tostenson, & Kangas, 2002; Wang & Johnson, 2001; Zheng, Wiesenborn, Tostenson, & Kangas, 2003). However, transport of material in this type of press depends mainly on friction between the material and the barrel’s inner surface and screw surface during screw rotation. Thus, a solid core component is often necessary to produce this friction, causing overheating, high energy consumption, and oil deterioration. Furthermore, single-screw presses provide insufficient crushing and mixing if they are not equipped with breaker bars, or other special equipment. A twin-screw oil press can be expected to solve these problems because of the higher transportation force, similar to a gear pump, and better mixing and crushing at the twin-screw interface, improving mechanical lysis of the cells. In addition, energy consumption of the twin-screw press is more efficient (Bouvier & Guyomard, 1997; Isobe et al., 1992). The advantages of twin-screw extruders stem from their capacity to carry out various functions and processes. According to Dziezak (1989), these include (1) an ability to provide better process control and versatility, especially in pumping efficiency, control of residence time distribution, and uniformity of processing; (2) an ability to process specialty formulations, which the single-screw extruder cannot handle; and (3) machine-setup flexibility, allowing self-cleaning mechanisms and rapid changeover of screw configurations without disassembling the extruder.

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The vegetable oil expression requires the use of an adapted screw profile along the barrel. The latter defines the arrangement of screw elements with different characteristics (pitch, stagger angle, and length) in different positions and with different spacing. It is the main factor influencing performance (product transformation, residence time distribution, and mechanical energy input) during extrusion processing (Choudhury, Gogoi, & Oswalt, 1998; Gogoi, Choudhury, & Oswalt, 1996; Gautam & Choudhury, 1999a, b). For the mechanical pressing of vegetable oils, the screw profile defines the following four successive functional areas: A feeding zone: The first elements are usually trapezoidal double-thread conveying screw and then conjugated double-thread conveying screw with wide pitch, which allows to quickly grab and transport the seeds. A crushing zone: the oilseed crushing is performed by an assembly of monolobe paddle-screw (DM) and/or bilobe paddle-screw, which both provide strong shearing and mixing effects on the material. Between two successive series of mixing discs, direct pitch screws, most often decreasing, ensure the conveying of the material. The raw material heating is also carried out in this functional area. A filtration zone: The filter is most often placed at the level of the penultimate module, that is to say immediately upstream from the pressing zone. The elements in that zone are conveying screws having a decreasing pitch, to ensure an axial pressure of the solid material from the pressing zone to the filtration one. The oil is thus expressed and flows freely by gravity at the filter. In addition, the filtering sieves are permanently unclogged thanks to the rotation of the screws that scrape their surface. A pressing zone: The pressing takes place in the last module. This fourth functional area is the place where the liquid/solid separation occurs. For that, doublethread reversed screw or simple-thread reversed screw are used, producing intensive shearing and considerable mixing of the matter, and exerting a strong axial compression in combination with the forward pitch screws. This opposes the movement of the material toward the barrel exit, and this ensures the formation of a dynamic plug against which the conveyed material comes to compress. The oily liquid can then express itself freely, and the residual solid material is extruded through the reversed screws and then conveyed toward the outlet of the barrel. Looking at the experiments conducted in this subject at LCA laboratory, the conditions of mechanical pressing were optimized for both sunflower (Amalia Kartika et al., 2005, 2006; Dufaure, Leyris et al., 1999; Evon et al., 2007, 2009) and then coriander (Uitterhaegen et al., 2015; Uitterhaegen, 2018) seeds to obtain oil expression efficiency as high as possible, simultaneously with oils of good quality. To do this, various parameters have been studied: (1) the screw profile, comprising two separate working areas, that is, the grinding (or crushing) area of oilseeds and then the pressing one, (2) the filling of the twin-screw reactor, (3) the pressing temperature, and (4) the oilseed moisture at the inlet. When oleic sunflower oil was expressed using a Clextral (France) BC 21 corotating twin-screw extruder, a longer reverse pitch screw improved oil yield, which attained 80% under optimized operating conditions (Dufaure, Leyris et al., 1999). The expression of oil from oleic sunflower seeds was then conducted using a

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twin-screw extruder of bigger capacity (i.e., BC 45 model). And, when two reverse pitch screws were used, the oil yield increased as the distance between them increased, and also with a decrease in the screw pitch (Amalia Kartika et al., 2005). In addition, an increase in the oil extraction yield was obtained as the pressing temperature, the screw rotation speed and the seed input flow rate were decreased. For that study, the higher oil extraction yield (close to 70%) was obtained from the optimal screw profile (Fig. 10.2), and under next operating conditions: 80 C, 60 rpm, and 24 kg/h. In parallel, the effect of the operating parameters on the oil quality was unimportant. In all experiments tested, the oil quality was very good (acid value below 2 mg KOH/g of oil, and total phosphorus content below 40 mg/kg). From the same BC 45 machine, the introduction of a second filtration zone improved the oil yield to 85% (Amalia Kartika et al., 2006). The corresponding press cake contained less than 13% residual oil. This highest oil extraction yield was obtained from the optimal screw profile (Fig. 10.3), and under next operating conditions: 120 C, 75 rpm, and 19 kg/h. In addition, the quality of the produced oil (acid value below 2 mg of KOH/g of oil, and total phosphorus content below 100 mg/kg) was similar to that obtained using traditional industrial extraction. A more recent work conducted at LCA laboratory consisted in extracting vegetable oil from coriander fruits by mechanical pressing (Uitterhaegen et al., 2015). The main fatty acid in coriander vegetable oil is petroselinic (6Z-octadecenoic) acid (up to 75%). Petroselinic acid is an uncommon isomer of oleic acid

C1F 33

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Figure 10.2 Optimal screw configuration for the extraction of vegetable oil from oleic sunflower seeds using a Clextral BC 45 twin-screw reactor and one filtration zone (Amalia Kartika et al., 2005). The numbers following the type of screw indicate the pitch of T2F, C2F, C1F and CF1C screws and the length of the DM and BB screws. BB, Bilobe paddle-screw; C1F, conveying simple-thread screw; C2F, conveying double-thread screw; CF1C, reverse simple-thread screw; CF2C, reverse double-thread screw; DM, monolobe paddle-screw; T2F, trapezoidal double-thread screw.

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Figure 10.3 Optimal screw configuration for the extraction of vegetable oil from oleic sunflower seeds using a Clextral BC 45 twin-screw reactor and two filtration zones (Amalia Kartika et al., 2006).

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found in high levels in oilseeds from the Apiaceae family (Gunstone, Harwood, & Dijkstra, 2007). Vegetable oil from coriander fruits has recently been labeled as a novel food ingredient by the European Food Safety Authority (2013). It is now considered as safe to be used as a food supplement for healthy adults, at a maximum level of 600 mg/day. Therefore, the mechanical pressing of vegetable oil from coriander fruits using a Clextral BC 21 twin-screw reactor was optimized. The screw configuration, the device’s filling coefficient (i.e., the ratio of the inlet flow rate of coriander fruits to the screw rotation speed), and the pressing temperature were varied. The application of twin-screw extrusion was effective. It resulted in significant oil yields while maintaining low foot content (i.e., solid particles forced through the filter) inside the filtrates. The screw profile exhibited a key influence on the extraction efficiency, and oil yields of at least 40% were reached when the pressing zone was positioned immediately after the filter and consisted of 50 mm long, reverse screws with a 233 mm pitch (Fig. 10.4). The highest oil recovery was 47%, and it was obtained from next operating conditions: a device’s filling coefficient of 39.4 g/h rpm (i.e., 3.94 kg/h for the inlet flow rate of coriander fruits and 100 rpm for the screw rotation speed), and a pressing temperature of 120 C. This highest yield was associated with a filtrate’s foot content of only 11%, and a residual oil content of 16.8% inside the press cake instead of 27.7% for the starting fruits. Lastly, all produced oils were of acceptable quality (,1.5% acidity), showed high petroselinic acid content (73%), and were pleasantly scented because part of the essential oil was coextracted with the vegetable oil. A complementary optimization study dealing with the mechanical pressing of coriander vegetable oil from fruits in the Clextral BC 21 twin-screw machine was then made using the optimal screw configuration from Uitterhaegen et al. (2015). This confidential study was conducted in the form of an experimental design using three variables: (1) the extrusion temperature, especially in the pressing zone, (2) the screw rotation speed with fixed inlet flow rate of fruits (i.e., the device’s filling coefficient), and (3) the fruit moisture content (Uitterhaegen, 2018). The twin-screw extrusion process was then characterized through the response surface methodology, and the multiobjective optimization was based on (1) the oil extraction efficiency, (2) the oil and press cake quality, and (3) the energy consumption. The fruit moisture content at the inlet was the most determinant parameter. In comparison with the preliminary study (Uitterhaegen et al., 2015), an important increase in the oil recovery was obtained. Indeed, the potential to recover up to 74% of the

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Figure 10.4 Optimal screw configuration for the extraction of vegetable oil from coriander fruits using a Clextral BC 21 twin-screw reactor (Uitterhaegen et al., 2015).

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vegetable oil from fruits in a single mechanical pressing step was evidenced. However, when also taking into account the oil quality and the energy consumption of the production process, the optimal conditions resulted in an oil recovery of 59%, with good oil quality and an energy consumption below 1 kW h/kg pressed oil. With 23 g of essential oil compounds/kg of pressed oil, the latter was also agreeably scented. In addition, the mechanical pressing process revealed a flexibility to answer to continuously changing market situations. Indeed, thanks to the variation of the operating parameters, it was possible to obtain the desired product, that is, a vegetable oil more or less flavored. Lastly, the scale-up of the pressing process was conducted successfully from a twin-screw reactor of much higher capacity (i.e., Evolum HT 53 model) (Uitterhaegen, 2018). This contributed to a significant increase in the inlet flow rate of coriander fruits, that is, from 3.4 kg dry matter per hour up to 33.2 kg/h for the optimal conditions, while maintaining good oil extraction efficiency.

10.4

Extraction

Thermomechanical treatment during twin-screw extrusion can be exploited to destructure plants to access to molecules located in the cytoplasm or in the walls. During twin-screw extrusion, the screw profile can be organized to greatly slow the screw speed with respect to the upstream zone. This action, led by the reverse screws, allows to compress the material and to destroy its structure. But it is also possible to use this action to compress the material and express a liquid. But twinscrew extrusion also allows for solvent introduction to promote the release of the molecules and their extraction through a screen (Fig. 10.5).

Figure 10.5 Schematic representation of the Clextral BC 45 twin-screw extruder used as a liquid/solid extractor and separator (Evon et al., 2016).

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10.4.1 Lignocellulosic residues 10.4.1.1 Introduction Lignocellulosic plant residues, such as straw or bran, contain molecules that are of industrial interest, either for valorization in the production of biofuels or as food additives. The extraction of these molecules requires a strong thermomechanicalchemical treatment, to dissociate them from cellulose, close to what is achieved in the paper processing. Twin-screw extrusion is an interesting alternative because it allows all these actions to be carried out continuously with a low liquid/solid ratio. The low water content of this biomass requires the introduction of a solvent, which is generally aqueous, either water, acid, or a base. The acid treatment of biomass is the most industrially advanced. It allows the complete hydrolysis of biomass, the precipitation of lignins and thus leads to the production of an extract containing a glucose/xylose mixture that is separated by chromatography. However, the profitability of this process remains low, which indicates that the biorefinery of lignocellulosic biomass requires the valorization of phenolic compounds derived from lignin. When the treatment is done with water, the chemical action is lower, and it is necessary to work with more drastic thermomechanical conditions, temperature above 120 C and strong mechanical destruction of the biomass to promote the transfer of the solvent. The hydrolysis of certain ester bonds leads to the production of acetic acid; the extract obtained is therefore slightly acidic. Extraction under basic conditions is most studied in the context of the biorefinery, because it allows the best solubilization of lignin and hemicelluloses. If the separation is effective, this treatment can lead to the production of a solid residue (raffinate) mainly cellulosic and a basic extract containing hemicelluloses and lignins, more or less degraded depending on the conditions used.

10.4.1.2 Straw Straw is a reference lignocellulosic biomass because, like bagasse, it contains practically only cellulose, lignins, and hemicelluloses. Tests carried out on a Clextral BC-45 extruder on 45 mm premilled straw yielded a hemicellulose extraction yield of 75% and lignins of 60% with a straw/soda ratio of 2.5 and liquid/solid ratio of 7. In this case, the solid content of the solid residue is 25%, with a degree of crystallinity of the cellulose of 90%, that is to say that it has been slightly degraded. The efficiency of extraction is very dependent on the liquid/solid ratio because the higher the water content, the faster the transfer, but there is an optimum, because beyond a certain ratio, it is no longer possible to generate a dynamic plug and the transmission of mechanical energy is less effective. When the water content is high enough, the straw/soda ratio becomes very important. Indeed, during extrusion, the contact time is very short, and the kinetics of hydrolysis becomes the limiting step. The higher the ratio, the higher the efficiency of hydrolysis, but this leads to degradation of the cellulose. In addition, an optimum is defined because when the soda content is too high, the viscosity of the matrix decreases, and the pressing in the

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reverse screws becomes lower, decreasing the recovery efficiency of the liquid fraction. Not all targeted molecules are free in the lignocellulosic matrix. They can be entrapped by covalent bonds. Their extraction then depends not only on their dissolution in the solvent but also on the preliminary breaking of the chemical bonds. Introducing a solvent in the TSE process is then insufficient to reach appreciable yields. The efficiency is increased by introducing well-chosen catalysts and/or reagents to react on the chemical structure of the biomass and to free the biomolecules of interest. For example, using TSE process demonstrated advantages for the recovery of hydroxycinnamic acids (HCAs) from hemp by-products. Hemp hurds and hemp dust were studied as potential sources for the production of two high-value-added HCA: ferulic (FA) and p-coumaric acids (p-CA). Prior to TSE, FA and p-CA analytical contents were evaluated to 0.3 and 3.5 g/kg dry matter for hemp hurds and 0.1 and 0.8 g/kg dry matter for hemp dust as potentials of reference. The continuous TSE pilot scale extraction was then studied. Mild conditions were developed: 50 C, alkaline aqueous or hydroalcoholic solvent (less than 0.5 M NaOH) and low liquid to solid ratios. The mechanical effect helps the diffusion of the solvent, promotes the hydrolysis of the ester and ether bonds, and favors the extraction of HCA in a short time. Yields in p-CA and FA reached 50% and 33%, respectively, of the free and bound contents for hemp hurds. For hemp dust, all of p-CA was extracted, whereas 60% of FA was recovered.

10.4.1.3 Bran The first tests carried out with bran showed that the low content of cellulosic fiber does not allow the transmission of mechanical energy to the material, and it is not possible to generate a dynamic plug at the end of the extruder. The extrusion of a bran/straw blend was therefore studied. Bran impregnation with sodium hydroxide in the twin-screw extruder was efficient, but the separation between the hemicellulosic gel and the lignocellulosic matrix had to be realized in another apparatus and remained difficult without a dilution to an L/S ratio of 50. Bran and straw coextrusion was therefore investigated in order to reduce the L/S ratio. Straw fibers formed a dynamic plug in the restrictive elements. Wheat bran and sodium hydroxide were mixed at room temperature in a separate reactor one hour before each experiment with an L/S ratio of 10, and the mixture was pumped in the twin-screw extruder, while straw was introduced in the extruder’s first section with a screw feeder. Straw was mixed with the alkaline dough in the first zone of the barrel through the neutral pitch element and the reverse pitch screw element successively. Washing water was injected downstream from this zone, and the mixture was conveyed through the second reverse pitch located just downstream from the filtration module. Several trials have shown that the best results for the coextraction of xylans from wheat bran and straw were obtained when working with a low screw speed and a high washing water flow rate.

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Figure 10.6 percentage of solubilized organic matter recovered in the filtrate to the total of introduced organic matter.

The yield in organic matter swept along in the filtrate versus the total quantity of organic matter introduced in the system (Fig. 10.6) depends on two factors: first, the quantity of NaOH available and second, the quality of the dynamic filtration tap in the twin-screw extruder. A low rate of NaOH (bran/soda 5 7) with low straw concentration seems to be sufficient to extract most of the alkaline soluble compounds. Filtration with such soda rate remains possible for every straw/bran ratio. High straw feed rates give the best filtration tap efficiency, but also a lower organic matter recovery because of the decrease in the global soda/vegetable matter rate. Experimental conditions combining a high soda content (bran/soda 5 2) with a high straw introduction rate also give good yields in extracted organic matter as long as the vegetable matter/soda rate is kept around 15
20 to allow the formation of the fibrous tap. If this ratio is too low (when smaller quantity of straw is being used), the quantity of cellulosic fibers is not sufficient, and the high lubricating effect of soda prevents the formation of the dynamic tap in the extruder. As the pressure in the sheath does not increase, the filtrate flow rate drops, followed by a decrease in the yield of the extracted hemicelluloses. The best results were obtained with a straw/bran ratio of 2 and a bran/soda ratio of 7 at a temperature of 50 C. Extraction was carried out with an L/S ratio of 10. Extract was recovered after centrifugation with a concentration of 2.3% (dry matter), 65% of this dry mater being organic matter.

10.4.1.4 Wood The composition of the wood is quite similar to that of straw and contains mainly cellulose, hemicelluloses, and lignins. The chemical structures are nevertheless very different from those of plants, and according to the species of wood, there are specific molecules such as tannins. These compounds have an aromatic chemical structure but are much more soluble in water than lignins. The treatment of wood by extrusion with

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water requires working at high temperature and with a screw profile which has a large mechanical grinding action. But even under these conditions, it is mainly tannins that are extracted, while hemicelluloses and lignins are little impacted. This problem is related to the residence time too short in the extruder, which does not allow the hydrolysis of the ester bonds. This is especially for species such as beech, whose physical structure makes the transfer of matter difficult. Thus, wood extrusion allows selective extraction of tannins without modifying the lignocellulosic matrix. If soda ash is used with a NaOH/dry matter ratio of 0.1, the hemicellulose content in the residue after extraction increases from 25% dry matter to 15% dry matter, that is, a yield of nearly 40%. However, this influence is much weaker than the solubilization of lignins, whose content increases from 26% to 9%, that is, an yield of 65%. However, as the concentration of soda increases, the proportion of xylan increases and especially the Xylose/Arabinose (X/A) ratio increases very significantly from 9.6 for the NaOH/dry matter ratio of 0.05
21 for the 0.1 ratio. This evolution could be explained by the degradation of sugars because their recovery yield in the extract is only 10% under the evaluated conditions. Another example of wood treatment concerns the water extraction of polyphenols from the by-products of the wood sector (paper industry, building, or furniture manufacturing): maritime pine knots and stumps, aspen knots and barks. Indeed, the presence of polyphenols and antiradical compounds of flavonoid type characterizes these raw materials. At analytical scale, they are extracted with medium polarity solvents (ethanol, methanol), but water is not efficient. In the TSE, the temperature and pressure conditions to which the liquid/solid mixture is subjected in the zones of mechanical stress are favorable for the passage of water in the subcritical state. Under these conditions, its viscosity, surface tension, and polarity decrease and reach the physicochemical properties of methanol or ethanol. The flavonoids are then solubilized and extracted. At a flow rate of 15 kg/h in wood by-product, the influence of temperature (50 C
150 C) and liquid/ratio (3
6) was studied. After a conveying zone of two modules, the first part of the solvent was introduced at module 3 ahead from a mixing zone of bilobe paddle screws. It ensured intimate mixing of the solid with the first liquid fraction and favored the diffusion of the solvent. The other liquid fraction was injected at the module 5 level. It has a washing effect under mechanical and thermal effects. Modules 2
5 corresponded to the liquid/solid extraction zone, whereas modules 6
7 were responsible for the solid/liquid separation. It was concluded that the liquid/solid ratio had a major influence. An increase in liquid/solid ratio led to a higher breakdown of the material and a better solid/liquid separation for all plant materials. For example, for maritime pine stumps, the respective yields in total extracted molecules and polyphenols (g/kg dry raw material) increased from 19 and 0.9 at a ratio of 3 to 31 and 1.6 at a ratio of 6. The optimal extraction yield in polyphenols of 1.6 g/kg dry material represented 25% of the analytical polyphenolic content. The twin-screw extracts, thanks to their polyphenolic content and their high antiradical activity, can be used as mass products (preservatives for woody materials, antioxidant for paints) or as fine value-added substances (for food and health applications).

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10.4.2 Green plants 10.4.2.1 Introduction Green plants have been used for many years as animal feed due to their high protein and fiber content. The high-protein content is linked to the presence of rubisco, an enzyme involved in CO2 binding in the Calvin cycle. Rubisco is interesting because its amino acid content is very balanced, which has prompted Food and Agriculture Organization of the United Nations to take an interest in it to meet protein needs in developing countries. Among forage plants, alfalfa (Medicago sativa) is the most widely grown plant in Europe with a production of 100 million tons. Alfalfa is a widely cultivated forage crop, mainly in Europe and North America, since it has a high feeding value: about 2600 kg of proteins per hectare. Alfalfa is currently used by the green crop drying industry as raw material for production of pellets for cattle. Indeed, it contains about 20% of crude proteins and is a good source of vitamins and minerals. Usually, the green crop is chopped and pressed prior to drying, which results in the production of large amounts of alfalfa juice, often considered as fertilizer, or sometime as a waste, even if it was an effective source of highly valuable proteins. A new approach for alfalfa fractionation is required to improve the whole plant valorization.

10.4.2.2 Alfalfa extrusion Used as fodder for animal feed, alfalfa is industrially dried in rotary kilns, up to a final dry matter content of 87%. According to ADEME, the energy consumption of these dryers is close to 800 kW h/t of evaporated water. Predehydration of alfalfa can be considered by a thermally assisted mechanical dewatering (TAMD) process (Arlabosse, Blanc, Kerfai, & Fernandez, 2011). One of the limitations of the process is the ability to extract the water contained in the cells, which mainly comes out through the stomata during compression. The twin-screw extruder can also be an interesting predehydration tool because it initially crushes alfalfa and thus releases the intracellular content, water and proteins, which is then extracted from the cells when the material is compressed. The process can only be considered because the fiber content of the plant is high enough to allow the creation of a dynamic cap at the end of extrusion. This plug is created by positioning counter threads at the end of the profile, and the compression then allows the material to be wrung out and the liquid extracted then flows from the filter placed upstream of this zone. The screw profile that can be considered includes a shear zone, a filtration zone, and a compression zone. Different screw profiles can be declined with a higher or lower shear/compression ratio, two were particularly studied (Fig. 10.7). Tests were conducted on different alfalfa cuts to understand the influence of the composition of matter on the effectiveness of dehydration. The results showed that the cellulosic fiber content was very important for compression efficiency (Colas et al., 2013). The second and third cuts contain much more fiber and less protein.

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Profile A 3 C2F

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66 mm 50 mm 33 mm 33 mm 25 mm

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6

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25 25 mm 15 mm 33 33 33 mm 33 mm 33 mm 33 mm mm –25 mm mm mm

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6 C1F

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3 MPS

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C2F

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–15 25

33 mm 33 mm 33 mm 25 mm 15 mm mm mm

Figure 10.7 Most efficient studied screw profiles (Colas, Doumeng, Pontalier, & Rigal, 2013). Screw type and screw pitch or length are shown. BB, Bilobe paddle-screw; C1F, conveying simple screw; C2F, conveying double-thread screw; CF1C, reverse screw; CF1Ct, reverse screw; MPS, monolobe paddle-screw; T2F, trapezoidal double-thread screw.

In this case, the compression is much stronger and leads to an increase in dry matter, which can go, in the best condition from 38% to 53% in the residue, which is quite high considering about 50% of the dry matter was extracted. The protein content is also important for the efficiency of extrusion. When the proteins are released, by the shearing action of the screws, they remain trapped in the cellulosic matrix, and modify the viscosity of the cap, which becomes complicated to compress. In this case, water recovery and protein extraction are difficult. One solution is the introduction of water, which will allow the proteins to move away from the cellulosic fibers. The cap is then dried, and compression is much more effective, leading to better dehydration of alfalfa. Thus, two optimal conditions can be defined: G

G

With a shearing profile, greater cell deconstruction, and the introduction of water to lead to a high L/S ratio. In this case, it is possible to predehydrate the alfalfa while having a protein extraction yield of nearly 50%. In this case, the optimal temperature is low in order to increase the viscosity of the dynamic cap as much as possible. The optimum for protein recovery and plant dehydration was obtained at 23 C, with a liquid/solid ratio of 8, and led to a protein recovery of 59% and a residue with 54% DW. With a compression profile, the cells are simply crushed, which allows the extraction of intercellular water. Predehydration is possible but leads to low protein extraction. In this case, the temperature must be high in order to promote the convective transport of water out of the lignocellulosic matrix.

The structure of the plant is crucial for the treatment efficiency. Hence, the harvesting period has a significant effect, particularly for alfalfa not only because of a water content change but also because the fiber content is drastically modified. The treatment is then less efficient with the first cut, when the plant contains a small quantity of cellulose, than with the second one, but the TSE screw profile can be adapted to this change, and can produce an almost constant residue. This result

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indicates that TSE is an efficient tool for green-plant fractionation, allowing the recovery of molecules from the plant cytoplasm while producing a cellulosic residue that can be used for cellulose, hemicelluloses, and lignin recovery.

10.4.3 Oil extraction 10.4.3.1 Water extraction In addition to mechanical pressing and thanks to its remarkable versatility, the twin-screw extrusion technology also allowed the aqueous coextraction of sunflower vegetable oil and tensioactive proteins, from (1) seeds (Evon et al., 2007), (2) press cake (Evon et al., 2009), and (3) whole plant (Evon et al., 2016). It was then used simultaneously as a liquid/solid extractor and separator. Looking specifically at the sunflower whole-plant case and because the developed process considered its complete valorization, the thermomechano-chemical twin-screw reactor (BC 45 model) could be considered as a new perspective for the sunflower biorefinery. Indeed, it allowed the production of biodegradable fiberboards from cake (Evon, Vandenbossche, & Rigal, 2012; Evon, Vandenbossche, Pontalier, & Rigal, 2010, 2014; Evon, Vinet, Labonne, & Rigal, 2015) in addition to the aqueous coextraction of oil and other biopolymers. Three basic operations were conducted during the whole-plant treatment, that is, grinding, liquid/solid extraction, and liquid/solid separation, following one another in the same device. And, this is the high content of whole plant in lignocellulosic fibers (33% of dry matter) which enabled an effective liquid/solid separation at the end of the screw profile, that is, at the level of the reversed elements. The sunflower biorefinery then resulted in the continuous production of both an extract and a raffinate. The treatment of the extract (Fig. 10.8) made possible its reorganization into four distinct phases (from the least dense to the densest): (1) an upper hydrophobic phase, (2) a hydrophilic phase, (3) a lower hydrophobic phase, and (4) a foot, which may be added to the cake. From the optimal operating conditions (optimized screw profile, 80 C temperature, 60 rpm screw speed, 5.0 kg/h inlet flow rate of whole plant, and 20.3 kg/h inlet flow rate of water), oil and protein extraction yields were 64.9% and 54.9%, respectively. Residual oil and protein contents in the cake were 13.1% and 6.7% of dry matter, respectively, instead of 26.8% and 17.0% in whole plant. The hydrophilic phase (75.4% of the filtrate’s weight) revealed a high-protein content (i.e., 23.3% of its dry matter). Conversely, its lipid content was low (i.e., 5.3%), indicating a good separation between the hydrophilic phase and both hydrophobic phases. In parallel, the two hydrophobic phases had the form of oil-in-water emulsions. The upper and lower hydrophobic phases represented 11.3% and 6.6%, respectively, of the filtrate’s weight. Their chemical compositions (% of dry matter) were as follows; 77.3% lipids and 15.0% proteins for the upper hydrophobic phase. For the lower hydrophobic phase, 60.2% lipids, 15.0% proteins, 9.7% pectic substances, and 8.7% nonpectic sugars.

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Figure 10.8 Valorization scheme proposed for each fraction from the biorefinery of sunflower whole plant using the thermomechano-chemical twin-screw reactor (Evon et al., 2016).

Edible vegetable oil was in fact extracted in the form of stable emulsions over time, the latter being stabilized at their interfaces by phospholipids and proteins or even pectic substances and nonpectic sugars in the case of the lower hydrophobic phase, which were natural surface-active agents coextracted during the process. Among the 44.5% extracted lipids, 43.2% were inside the two hydrophobic phases (i.e., 32.8% for the upper one and 10.5% for the lower one). The hydrophilic phase represented the main filtrate’s fraction. It was a very dilute phase representing 57.2% of the injected water. A market study revealed the low interest of sunflower pectins contained in the hydrophilic phase for use as gelling agents. Its most reasonable use was thus its recycling to the twin-screw process, reducing the water intake. When observed using an optical microscope, both hydrophobic phases revealed the presence of oil droplets dispersed in the water phase. A laser particle size analysis showed that they were a little smaller inside the upper hydrophobic phase than in the lower one (1.10 and 1.20 μm, respectively, for the mean droplet diameters). A market study revealed the possible interest of both oil-in-water emulsions for their use in the cosmetics industry. And, this was practically confirmed for the lower hydrophobic phase (i.e., the more viscous emulsion). Indeed, the latter could be used for the formulation of various cosmetic products, for example, highly penetrating night creams with high emollient capacity, gels with strong film forming, shower gels, shower oils, which could favor a good economic valuation (from 10 to 50 h/kg). The market study also evidenced that both hydrophobic phases could be used in the food industry. In particular, regarding the upper hydrophobic phase (i.e., the more fluid emulsion), it could be used in its original emulsion form for the

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Green Food Processing Techniques

manufacture of ready meals. As a second food industrial application, the demixing of this upper hydrophobic phase was also investigated. It was obtained by treating it using ethanol/ether mixture (3/1) or absolute ethanol, thus leading to the rupture of the interfacial film between oil and water. Then, a centrifugation step led to the separation between a supernatant and a solid pellet. On the one hand, an edible vegetable oil of high purity was obtained through evaporation of ethanol/ether mixture or ethanol into the supernatant. On the other hand, the centrifugation pellet was a light-colored powder containing a high proportion (i.e., two thirds of its dry weight) of proteins, mainly albumins. As revealed by their differential thermal analysis which evidenced an endothermic peak at a 155 C transition temperature (Evon, 2008), these proteins were not so much denatured during the thermomechanochemical fractionation of whole plant in the twin-screw reactor. Thus, while proteins from industrial cakes are still penalized by their dark color, obtaining “white” proteins with a surfactant character from the sunflower biorefinery could offer new opportunities, especially for food applications (Canella, Castriotta, Bernardi, & Boni, 1985).

10.4.3.2 Solvent extraction The TSE technology was also used for the solvent extraction of sunflower vegetable oil from seeds using an alcohol (Dufaure, Mouloungui, & Rigal, 1999) or fatty acid methyl esters (Amalia Kartika, Pontalier, & Rigal, 2010). In a first study, Dufaure, Mouloungui et al. (1999) used a Clextral BC 21 twin-screw extruder, and the extraction of sunflower seed oil of oleic variety (high purity in oleic acid, i.e., .85%) was then assisted by the injection of 2-ethylhexanol and acidified 2-ethylhexanol inside the barrel. An increase in the oil recovery from 80% without solvent injection to 88% was evidenced when 2-ethylhexanol mixed with phosphoric acid was injected and when the extraction temperature was low (80 C). The membranes surrounding lipid bodies, which contain most of the oil in the kernel, became more labile thanks to the alcohol/phosphoric acid mixture. This resulted in a facilitated oil release. Phosphoric acid also exhibited extracting and degumming roles. The extracted oil was recovered after alcoholic distillation, and its quality was considered as satisfactory with a total acid value (i.e., mineral acidity plus organic acidity) of 4 mg KOH/g oil and organic phosphorus content below 30 ppm. Using an alcohol as extracting solvent resulted in a medium that could be used directly for oleochemistry. Indeed, triglycerides could be transformed into 2ethylhexyl esters through transesterification, the residual phosphoric acid acting as a good catalyst for the reaction (Lacaze-Dufaure, 1998; Mouloungui, LacazeDufaure, Gaset, & Rigal, 1998). The second study was conducted in a Clectral BC 45 machine, and it consisted in processing continuously vegetable oil from seeds through mechanical pressing and then solvent extraction using fatty acid methyl esters as extracting solvent in a single step, that is, in the same time and machine (Amalia Kartika et al., 2010). Two different filtrates were thus produced in two successive zones (Fig. 10.9). The operating parameters, that is, the screw rotation speed, the seed feed rate, and the

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Feed

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3

4

5

6

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3 BB 5x5

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2 C2F 25

1

Axis and screw profile

BB 5x5 C2F 33

Barrel

CF1C-25 C1F 25

First filter

Figure 10.9 Schematic modular barrel and screw profile of the Clextral BC 45 twin-screw extruder used for the thermomechanical pressing and the solvent extraction of vegetable oil from sunflower seeds in a single step (Amalia Kartika et al., 2010).

solvent-to-solid ratio, directly affected the oil recovery. Oil yield increased as the screw rotation speed and the feed rate were decreased, and as the solvent-to-solid ratio was increased at the same time. Highest yield was 98%, and it was obtained under next operating conditions: 185 rpm screw rotation speed, 30 kg/h seed feed rate, and 0.55 solvent-to-solid ratio. The oil quality was equivalent to that obtained with industrial single-screw presses. In addition, the cake meal obtained from such conditions was of particularly good quality (residual oil content lower than 3%). Lastly, it can be noted that the injection of fatty acid methyl esters contributed to an increase in the oil extraction yield by approximately 12%, this solvent solubilizing part of the residual oil contained in the pressed material generated in the first filter section. The oil/fatty acid methyl esters mixture collected at the level of the second filter could be directly used as a biofuel to generate heat, power, and/or chemicals. As a substitute for fossil fuel, this mixture could be considered as a source of renewable energy with a considerable environmental potential (Demirbas & Balat, 2006).

References Amalia Kartika, I., Pontalier, P. Y., & Rigal, L. (2005). Oil extraction of oleic sunflower seeds by twin screw extruder: Influence of screw configuration and operating conditions. Industrial Crops and Products, 2005(22), 207
222. Amalia Kartika, I., Pontalier, P. Y., & Rigal, L. (2006). Extraction of sunflower oil by twin screw extruder: Screw configuration and operating conditions effects. Bioresource Technology, 97, 2302
2310.

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Amalia Kartika, I., Pontalier, P. Y., & Rigal, L. (2010). Twin-screw extruder for oil processing of sunflower seeds: Thermo-mechanical pressing and solvent extraction in a single step. Industrial Crops and Products, 32, 297
304. Areas, J. A. (1992). Extrusion of food proteins. Critical Reviews in Food Science and Nutrition, 32(4), 365
392. Arlabosse, P., Blanc, M., Kerfai, S., & Fernandez, A. (2011). Production of green juice with an intensive thermo-mechanical fractionation process. Part I: Effects of processing conditions on the dewatering kinetics. Chemical Engineering, 168(2), 586
592. Beyer, G., & Hopmann, C. (2018). Reactive Extrusion: Principles and Applications. Weinheim: Wiley-VCH (New-York). Bouvier J.M., Guyomard P. (1997). Method and installation for continuous extraction of a liquid contained in a raw material. In: PCT/FR97/00696. Canella, M., Castriotta, G., Bernardi, A., & Boni, R. (1985). Functional properties of individual sunflower albumin and globulin. Lebensmittel-Wissenschaft und Technologie, 18, 288
292. Choudhury, G. S., Gogoi, B. K., & Oswalt, A. J. (1998). Twin screw extrusion of pink salmon muscle and rice flour blends: Effects of kneading elements. Journal of Aquatic Food Product Technology, 7, 69
91. Colas, D., Doumeng, C., Pontalier, P.-Y., & Rigal, L. (2013). Twin-screw extrusion technology, an original solution for the extraction of proteins from alfalfa (Medicago sativa). Food and Bioproducts Processing, 91, 175
182. Crowe, T. W., Johnson, L. A., & Wang, T. (2001). Characterization of extruded-expelled soybean flours. Journal of the American Oil Chemists’ Society, 78, 775
779. De Choudens, C., Angelier, R., & Lombardo, G. (1987). Pˆates chimico-me´caniques blanchies obtenues par le proce´de´ «bi-vis»: cCaracte´ristiques et utilisations. Revue-ATIP, 41(2), 63
68. Demirbas, M. F., & Balat, M. (2006). Recent advances on the production and utilization trends of bio-fuels: A global perspective. Energy Conversion and Management, 47, 2371
2381. Dufaure, C., Leyris, J., Rigal, L., & Mouloungui, Z. (1999). A twin-screw extruder for oil extraction: I. Direct expression of oleic sunflower seeds. Journal of the American Oil Chemists’ Society, 76, 1073
1079. Dufaure, C., Mouloungui, Z., & Rigal, L. (1999). A twin-screw extruder for oil extraction: II. Alcohol extraction of oleic sunflower seeds. Journal of the American Oil Chemists’ Society, 76, 1081
1086. Dziezak, J. D. (1989). Single and twin-screw extruders in food processing. Food Technology, 164
174. European Food Safety Authority. (2013). Scientific opinion on the safety of coriander seed oil as a novel food ingredient. EFSA Journal, 11(10), 3422. Evon P. (2008). New process for the biorefinery of sunflower whole plant by thermomechano-chemical fractionation in twin-screw extruder: Study of the aqueous extraction of lipids and manufacturing of the raffinate into agromaterials by compression moulding (Ph.D. thesis). Institut National Polytechnique de Toulouse, France. Evon, P., Vandenbossche, V., Candy, L., Pontalier, P. Y., & Rouilly, A. (2018). Twin-screw extrusion: A key technology for the biorefinery, . Biomass extrusion and reaction technologies: Principles to practices and future potential (Vol. 2, pp. 25
44). American Chemical Society, ACS Symposium Series, eBooks. Evon, P., Vandenbossche, V., Labonne, L., Vinet, J., Pontalier, P. Y., & Rigal, L. (2016). The thermo-mechano-chemical twin-screw reactor, a new perspective for the biorefinery

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of sunflower whole plant: Aqueous extraction of oil and other biopolymers, and production of biodegradable fiberboards from solid raffinate. Oilseeds & fats, Crops and Lipids, 23(5), D505. (2016). Evon, P., Vandenbossche, V., Pontalier, P. Y., & Rigal, L. (2007). Direct extraction of oil from sunflower seeds by twin-screw extruder according to an aqueous extraction process: Feasibility study and influence of operating conditions. Industrial Crops and Products, 26, 351
359. Evon, P., Vandenbossche, V., Pontalier, P. Y., & Rigal, L. (2009). Aqueous extraction of residual oil from sunflower press cake using a twin-screw extruder: Feasibility study. Industrial Crops and Products, 29, 455
465. Evon, P., Vandenbossche, V., Pontalier, P. Y., & Rigal, L. (2010). Thermomechanical behaviour of the raffinate resulting from the aqueous extraction of sunflower whole plant in twin-screw extruder: Manufacturing of biodegradable agromaterials by thermopressing. Advanced Materials Research, 112, 63
72. Evon, P., Vandenbossche, V., Pontalier, P. Y., & Rigal, L. (2014). New thermal insulation fiberboards from cake generated during biorefinery of sunflower whole plant in a twinscrew extruder. Industrial Crops and Products, 52, 354
362. Evon, P., Vandenbossche, V., & Rigal, L. (2012). Manufacturing of renewable and biodegradable fiberboards from cake generated during biorefinery of sunflower whole plant in twin-screw extruder: Influence of thermo-pressing conditions. Polymer Degradation and Stability, 97, 1940
1947. Evon, P., Vinet, J., Labonne, L., & Rigal, L. (2015). Influence of thermopressing conditions on mechanical properties of biodegradable fiberboards made from a deoiled sunflower cake. Industrial Crops and Products, 65, 117
126. Fellows, P. (2000). Food processing technology: Principles and practice (2nd ed.). Boca Raton, FL: CRC Press978-084-9308-87-1. Gautam, A., & Choudhury, G. S. (1999a). Screw configuration effect on residence time distribution and mixing in twin-screw extruder during extrusion of rice flour. Journal of Food Process Engineering, 22, 263
285. Gautam, A., & Choudhury, G. S. (1999b). Screw configuration effect on starch breakdown during twin screw extrusion of rice flour. Journal of Food Processing and Preservation, 23, 355
375. Gogoi, B. K., Choudhury, G. S., & Oswalt, A. J. (1996). Effects of location and spacing of reversed screw and kneading element combination during twin-screw extrusion of starchy and proteinaceous blends. Food Research International, 29, 505
512. Gunstone, F. D., Harwood, J. L., & Dijkstra, A. J. (Eds.), (2007). The lipid handbook (3rd ed). Boca Raton, FL: CRC Press. Guy, R. (2001). Extrusion cooking: Technologies and applications. Cambridge, United Kingdom: Woodhead Publishing, 978-185-5735-59-0. Hietala, M. (2011). Extrusion processing of wood raw materials for use in wood-polymer composites (Ph.D. thesis). Oulu University (Finland). Hietala, M., Niinim¨aki, J., & Oksman, K. (2011). The use of twin-screw extrusion in processing of wood: The effect of processing parameters and pretreatment. Bioresources, 6(4), 4615
4625. Isobe, S., Zuber, F., Uemura, K., & Noguchi, A. (1992). A new twin-screw press design for oil extraction of dehulled sunflower seeds. Journal of the American Oil Chemists’ Society, 69, 884
889. Lacaze-Dufaure C. (1998) Fractionation of high oleic sunflower seeds: Pressing and chemical transformations of the triglycerides into esters used as lubricants and additives, in a

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batch reactor and a twin-screw reactor (Ph.D. thesis). Institut National Polytechnique de Toulouse, France. Lee, S.-H., Inoue, S., Teramoto, Y., & Endo, T. (2010). Enzymatic saccharification of woody biomass micro/nanofibrillated by continuous extrusion process II: Effect of hotcompressed water treatment. Bioresource Technology, 101, 9645
9649. Martin, C. (2016). Twin screw extruders as continuous mixers for thermal processing: A technical and historical perspective. AAPS PharmSciTech, 17(1), 3
19. Mouloungui Z., Lacaze-Dufaure C., Gaset A., & Rigal L. (1998). Process of production of alkyls esters by transesterification or alcoholysis. French Patent, FR 98/08062. N’Diaye, S., Rigal, L., Larocque, P., & Vidal, P. F. (1996). Extraction of hemicelluloses from poplar, Populus tremuloides, using an extruder-type twin-screw reactor: A feasibility study. Bioresource Technology, 57(1), 61
67. Rauwendaal, C., Gonzalez-Nunez, R., & Rodrigue, D. (2017). Polymer processing: Extrusion. In Encyclopedia of polymer science and technology (pp. 1
67). John Wiley & Sons. Rigal L. (2000). Twin-screw technology, a new tool for fractionation, and thermo-mechanochemical conversion of the agroresources. In: Proceedings of the first world conference on biomass for energy and industry. Singh, K. K., Wiesenborn, D. P., Tostenson, K., & Kangas, N. (2002). Influence of moisture content and cooking on screw pressing of crambe seed. Journal of the American Oil Chemists’ Society, 79, 165
170. Steel, C. J., Vernaza Leoro, M. G., Schmiele, M., Ferreira, R. E., & Chang, Y. K. (2012). Thermoplastic extrusion in food processing. In Adel El-Sonbati (Ed.), Thermoplastic elastomers. Rijeka, Croatia: Intech. Uitterhaegen, E. (2018). Study of the integrated biorefinery of vegetable and essential oil in Apiaceae seeds (Ph.D. thesis). Universite´ de Toulouse, France. Uitterhaegen, E., & Evon, P. (2017). Twin-screw extrusion technology for vegetable oil extraction: A review. Journal of Food Engineering, 212, 190
200. Uitterhaegen, E., Nguyen, Q. H., Sampaio, K. A., Stevens, C. V., Merah, O., Talou, T., . . . Evon, P. (2015). Extraction of coriander oil using twin-screw extrusion: Feasibility study and potential press cake applications. Journal of the American Oil Chemists’ Society 2015, 92(8), 1219
1233. Wang, T., & Johnson, L. A. (2001). Refining normal and genetically enhanced soybean oils obtained by various extraction methods. Journal of the American Oil Chemists’ Society, 78, 809
815. Zheng, Y., Wiesenborn, D. P., Tostenson, K., & Kangas, N. (2003). Screw pressing of whole and dehulled flaxseed for organic oil. Journal of the American Oil Chemists’ Society, 80, 1039
1045.

Further reading Guyomard, P. (1994). Study of the use of a twin-screw extruder in pressing-extrusion of oleaginous seeds (Ph.D. thesis). Universite´ Technologique de Compie`gne, France.

Gas-assisted oil expression from oilseeds

11

Houcine Mhemdi and Eugene Vorobiev TIMR Laboratory (UTC/ESCOM, EA 4297, TIMR), Research Center of Royallieu, Compiegne, France

11.1

Introduction

From ancient times, nuts and seeds have represented an essential part of human diet in many countries. These foods have been associated with protective effects on degenerative and chronic diseases including cardiovascular diseases and cancers through their content of dietary fibers, macronutrients, micronutrients, and bioactive compounds (Durmaz & Gokmen, 2010). Seeds and nuts could be pressed to produce edible oils with several beneficial properties. These oils have been used for human consumption (e.g., foods and cooking) with important nutritional purposes (Akpan, 2012; Mounts, Warner, List, & Neff, 1994) as well as in the pharmaceutical industry (Sakai, Kino, Takeuchi, & Ochi, 2010; Sionek, 1997). Some edible oils (e.g., olive oil, canola oil) are well known by their health-related benefits due to their richness in oleic acid, polyunsaturated fatty acids (linoleic and linolenic acids), vitamin E (especially α-tocopherol), and also to their high oxidative stability (mainly attributed to the presence of polyunsaturated fatty acids and γ-tocopherol), compared to other oils (Ezebor, Igwe, Owolabi, & Okoh, 2006; Okladnikov, Vorkel’, Trubachev, & Vlasova, 1977). For instance, in the last two decades the consumption of oil from oilseeds and nuts has grown considerably. In 2017 the world’s consumption of vegetable oils reached 187 million tons, which represents an increase of 6 million tons (3%) compared to that recorded in 2016 (USDA, 2017). In this increasing market, improvement of the production process is always pursued, which can be obtained in three areas: oil yield, oil quality, and production costs (Willems, 2007). Soybean, rapeseed, cottonseed, peanut, sunflower seed, palm kernel, and copra are the major oilseed crops produced worldwide, respectively, in the order of importance (Daun, Eskin, & Hickling, 2011). The extraction process is one of the key stages in the production of oil from oily seeds and nuts. The common conventional oil extraction processes are mechanical expression (ME) and/or solvent extraction (SE) (e.g., using n-hexane). Each technique has its benefits and drawbacks as far as operating cost, capital cost, yield, and quality of the extracts are concerned. ME (pressing) is by far the oldest and the cheapest way of the extraction. Cold pressing produces an oil of high quality but the low extraction yield negatively affects the economical profitability of the Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00011-2 © 2019 Elsevier Inc. All rights reserved.

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transformation process limiting its industrial development (Balvardi, Mendiola, Castro-Go´mez, & Fontecha, 2015; Bogaert, Hebert, Mhemdi, & Vorobiev, 2018). Organic SE is intermediate in capital and operating cost and is very efficient for the extraction of oilseeds with high yield. However, concerns about the solvent residues in the oleoresin products, the new regulations of volatile organic solvent emissions in the air, and the extent of further refining that is required after the extraction step restrain the use of this technology (Anderson, 1996; Walkelyn & Wan, 2006). The need for obtaining greener, sustainable, and viable processes has led both food industries and food scientists to develop alternative processes in full correspondence with green extraction concept (Anastas & Warner, 2000; Chemat, Vian, & Cravotto, 2012; Chemat et al., 2017). This concept assumes to make use of renewable plant resources and alternative green solvents, reduction of energy consumption, production of extracts with high quality and purity (nondenatured and biodegradable), and generation of coproducts instead of wastes (Anastas & Warner, 2000; Chemat et al., 2012, 2017). In this line, supercritical fluid (mainly CO2) extraction was proposed as an interesting alternative technique for the production of vegetable oil and a range of other substances from natural products (Brunner, 1994; Boutin & Badens, 2009). Compared to ME and hexane extraction, this technique has higher capital investment and moderate operating costs. However, neither solvent residues remain in the product after extraction nor there are any chemical changes due to the processing technique, which gives the extract of outstanding quality in full correspondence with green concept (Perrut & Clavier, 2003; Temelli, 2009). The investment costs, the CO2 consumption (100 kg CO2 per kg of oil), and the long extraction time (many hours) are the blocking points of the industrial development of this technology for the extraction of vegetable oils with low commercial value (Martin, Skinner, & Marriott, 2018; Mhemdi, Rodier, Kechaou, & Fages, 2011; Perrut & Clavier, 2003). In this context, different improvements, such as seed pretreatments (grinding, cooking, and flacking) before extraction, CO2 recycling, and the use of cosolvents were proposed and tested in order to reduce the extraction times and the CO2 consumption (Aguilera & del Valle, 1999; Koubaa, Mhemdi, & Vorobiev, 2016; Pradhan, Meda, Rout, & Naik, 2010; Rempel & Scanlon, 2012). More recently, applying supercritical fluid extraction along with ME was proposed as an interesting alternative to improve the recovery of seed oils. This process, called gas-assisted ME (GAME), is based on the combination of supercritical extraction and cold expression. In the GAME process, CO2 is dissolved in the oil contained in the seeds before pressing. The presence of supercritical CO2 (Sc-CO2) reduces the viscosity of oil which enhances the pressing kinetic. After pressing the CO2 is easily removed from the cake and oil by depressurization. During depressurization of the cake, some additional oil is removed by entrainment in the gas flow (Koubaa, Barba, Mhemdi, & Grimi, 2015; Koubaa, Lepreux, Barba, Mhemdi, & Vorobiev, 2017; Mhemdi, Koubaa, Majid, & Vorobiev, 2016; Mu¨ller & Eggers, 2014; Mu¨ller, Pietsch, & Eggers, 2014; Pietsch & Eggers, 2011; Venter, 2006; Venter, Hink, Kuipers, & de Haan, 2007; Venter, Willems, Kuipers, & de Haan, 2006; Willems & de Haan, 2011; Willems, Kuipers, & de Haan, 2008).

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Over the last years, some research groups have evaluated the potential of using supercritical fluids and GAME to improve the recovery yields as well as the quality of oils and meals obtained from oily seeds and nuts. This chapter will be focused on the presentation of GAME technology and the recent advances in oil extraction using it. A brief description of conventional methods for vegetable oil recovery will be first provided. The major part of this review will be focused on the use of GAME technology, from laboratory studies to industrial applications. The advantages and the limitations of the application of GAME will be discussed and evaluated. Some prospects will be finally proposed.

11.2

Conventional extraction methods of seed and nut oils

There are commonly two main processes to recover the maximum oil content from seeds and nuts: ME and SE. In fact, seeds with high oil content (e.g., rapeseed) could not be extracted efficiently in one step, and usually a substantial percentage of oil is left in the press cake or meal (Bogaert et al., 2018). The first step of the process, consisting generally on ME, is called prepressing. The process allows reducing the oil content in the seeds to around 20%. The achievement of oil extraction process is then performed either by a second pressing (for low-capacity plants) or using hexane (for industrial-scale plants).

11.2.1 Mechanical expression (pressing) Solid
liquid expression (pressing) is a unit operation in which a liquid is separated from a solid
liquid mixture by mechanical compression. It is widely used in food and food-related industries to express juice and vegetable oils from cellular materials (Bogaert et al., 2018). ME is generally considered the most efficient technique to recover virgin oil of high quality, but it only allows a partial defatting of the seeds. Therefore the resulting press cake is usually defatted by the means of percolation with hexane. Two types of presses are mainly used for oil extraction: hydraulic presses and screw presses. Hydraulic presses ensuring discontinuous and unidirectional compression are often used on laboratory and pilot scale (Bredeson, 1983; Chapuis, Blin, Carre´, & Lecomte, 2014; Daun, Buhr, Mills, Diosady, & Mag, 1993). Hydraulic presses are still used for pressing cocoa in order to extract the cocoa butter, in olive oil production, or in specialty oil production. The pressures encountered are very high: above 50 MPa and up to 100 MPa for cocoa and up to 40 MPa for olive oil (De Ginestel, 1998; Kartika, Pontalier, & Rigal, 2005). Screw presses are implemented at the industrial scale for continuous pressing of oilseeds (Koo, 1942; Laisney, 1984; Savoire, Lanoisele´, & Vorobiev, 2008). A screw press consists of a horizontal or vertical screw fitting closely inside a perforated cage (frame) where liquid (oil) is expelled. Both screw and cage are tapered toward the

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discharge to increase the pressure on the material (Bogaert et al., 2018; Savoire et al., 2008). There is a wide variety of screw presses depending on the supplier concerned. The most used are the expellers, the expanders, and the twin-screw systems (Bogaert et al., 2018; Kartika, Pontalier, & Rigal, 2005; Savoire et al., 2008). ME was intensively studied, and many reviews are available in the literature.

11.2.2 Solvent extraction In a continuous SE process the seeds are contacted with a solvent, generally hexane. The oil contained in the seeds is dissolved in the solvent after which solvent and solids are separated. The solvent is then removed by evaporation. The residual cake is sent to a desolventizer/toaster to eliminate the residual solvent in the meal (Daun et al., 1993; Laisney, 1984). Both oil and solid therefore undergo a heat treatment, which is detrimental for the oil and cake quality. The coextraction of undesired components further reduces the quality of the oil. However, this method is very efficient to recover almost all of the oil from the seeds (Daun et al., 1993; Laisney, 1984). The residual oil content in the meal does not exceed 1%. To further improve the efficiency of the process the extraction can be preceded by a prepressing step. Here part of the oil is recovered by a screw press, which reduces the size of the extractor and improves the permeability of the solids for the solvent (Daun et al., 1993; Laisney, 1984). Recently, many researchers investigated the replacement of hexane for the extraction of vegetable oil by bio-based, nontoxic, and biodegradable solvents, such as water, limonene, ethanol, methanol, and methylic esters (Cater, Rhee, Hargenrnaier, & Mattil, 1974; Cravotto et al., 2011; Lamsal & Johnson, 2007; Li et al., 2017; Sineiro, Dominiguez, Nunez, & Lema, 1998). Some results were promising but all these studies were carried out at the laboratory scale, and no pilot or industrial application has emerged.

11.2.3 Supercritical fluid extraction Supercritical fluid extraction is a recent technology that is of increasing importance in the production of vegetable oils and a range of other substances from natural products (da Silva, Rocha-Santos, & Duarte, 2016; De Melo, Silvestre, & Silva, 2014; Herrero, Castro-Puyana, Mendiola, & Iban˜ez, 2013; Herrero, Mendiola, Cifuentes, & Iba´n˜ez, 2010; Knez et al., 2013; Pereira & Meireles, 2010). The supercritical state is obtained when the pressure and temperature of a compound are increased beyond the so-called critical values. In this state the interface between the liquid and vapor phase disappears, and the fluid properties (density, viscosity, driving force) intermediate between those of the liquid and the vapor state. The properties can be modified by adjusting temperature and pressure allowing for a large change in solubility of solutes. This makes supercritical fluids interesting as extraction solvents. CO2 has been the most used solvent up to now, because of its relatively low critical pressure and temperature (7.38 MPa and 31 C, respectively), its availability, low toxicity, and low cost. This technique has high capital cost. However, neither solvent residues remain in the product after extraction nor there are any chemical

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changes due to the processing technique, which gives extract of outstanding quality (da Silva et al., 2016; De Melo et al., 2014; Herrero et al., 2010, 2013; Knez et al., 2013; Pereira & Meireles, 2010). The principle of extraction itself is similar to normal SE; however, the use of high pressure has a number of complications. Up to now, no continuous feeding system for solids at high pressure is available necessitating the extraction vessels to be depressurized for feeding and pressurized (sometimes up to 70 MPa). The extraction of vegetable oil by Sc-CO2 is well reviewed in the literature (da Silva et al., 2016; De Melo et al., 2014; Herrero et al., 2010, 2013; Knez et al., 2013; Pereira & Meireles, 2010).

11.3

Gas-assisted mechanical expression

As it was described above, all of the cited technologies have some advantages and some limitations (Table 11.1). It is desirable to find a technique that combines the high yields of supercritical extraction and the high oil quality of ME but does not require the large quantities of solvent used in supercritical extraction (100 kg of CO2 per kg of oil). This compromise may be possible by combining ME and supercritical extraction. This combination led to the development of a hybrid technology called GAME.

11.3.1 Fundamentals of gas-assisted mechanical expression technology GAME is a combination of ME and the use of Sc-CO2 (hence gas assisted). The principle of GAME is illustrated in Fig. 11.1 (Willems & de Haan, 2011). In the GAME process, CO2 is dissolved in the oil contained in the seeds before pressing. After equilibration the oil/CO2 mixture is expressed from the seeds. The dissolved CO2 displaces part of the oil during pressing. The oil present in the GAME press cake is saturated with CO2 reducing the oil content compared to the conventional cake by the same amount. Furthermore, the viscosity of CO2-saturated oils is considerably lower than that of the pure oils which increases the rate of pressing (Venter, 2006; Venter et al., 2006, 2007; Willems & de Haan, 2011; Willems et al., 2008). Therefore less energy will be needed to express

Table 11.1 Advantages and limitations of actual oil extraction techniques. Extraction technique

Oil yield

Oil quality

Solvent requirement per kg oil

Mechanical expression Solvent extraction (hexane) Supercritical extraction (CO2)

2 11 1

11 2 11

0 2 100

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Figure 11.1 Gas-assisted mechanical expression technology principle. Source: From Willems, P., & de Haan, A.B. (2011). Gas-assisted mechanical expression of oilseeds. In Enhancing extraction processes in the food industry (pp. 341
360). London, New York: CRC Press.

CO2-saturated oils from oilseeds compared to the expression of pure oils from the oilseeds. In addition, Sc-CO2 dissolving in the oil (up to 50%) may lead to higher volume occupied by CO2-saturated vegetable oils, which provokes cell swelling. These swelling phenomena may induce cell damage, thereby freeing the oil and enhancing the expression kinetics in GAME. It is expected that a higher Sc-CO2 solubility in the oil will result in a higher oil yield. Solids often melt substantially below their atmospheric melting points in the presence of Sc-CO2 (Koubaa et al., 2015; Venter, 2006; Venter et al., 2006, 2007; Willems & de Haan, 2011; Willems et al., 2008). GAME therefore offers the additional advantage that oilseeds can be processed at lower temperatures than those currently used in conventional expression. After pressing the CO2 is easily removed from the cake and oil by depressurization. During depressurization of the cake, some additional oil is removed by entrainment in the gas flow. In these conditions the efficiency of GAME is better than that of conventional ME (Koubaa et al., 2015; Venter, 2006; Venter et al., 2006, 2007; Willems et al., 2008). On the other hand the solubility of Sc-CO2 in vegetable oils is considerably higher than the solubility of the oils in Sc-CO2. In consequence a much smaller volume of Sc-CO2 is needed than in supercritical extraction without ME (Willems et al., 2008).

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11.3.2 Applications of gas-assisted mechanical expression technology GAME technology was successfully tested to extract oil from oilseeds at laboratory, pilot, and industrial scales. The first works about GAME technology were performed by Venter et al. (2006). They investigated the feasibility of using GAME technology to extract cocoa butter from cocoa nibs and edible oils from various oilseeds (sesame, linseed, rapeseed, palm kernel, and jatropha) in the laboratory scale (Venter, 2006; Venter et al., 2006). GAME experiments with cocoa nibs were performed at the temperatures of 40 C
100 C, Sc-CO2 pressures of 0
20 MPa, and effective mechanical pressures (applied mechanical pressure minus Sc-CO2 pressure) of 20
50 MPa. The maximum yield with ME alone (71.8%) was obtained at the pressure of 50 MPa and the temperature of 100 C. It is shown that GAME has a substantially higher yield than conventional ME for the recovery of cocoa butter from cocoa nibs, with the highest yield (87.1%) obtained at 100 C, an Sc-CO2 pressure of 10 MPa, and an effective mechanical pressure of 50 MPa. The cocoa butter yield increases with increasing Sc-CO2 pressure until 10 MPa but remains almost constant for higher Sc-CO2 pressures. In contrast to conventional expression, GAME also allows the recovery of cocoa butter from cocoa nibs at the temperatures below the melting point of pure cocoa butter. The cocoa butter produced with GAME was found to be unfractionated and is therefore of the same quality as mechanically expressed cocoa butter (Venter, 2006; Venter et al., 2006). For oilseeds extraction the effects of temperature (40 C) and the effective pressure (10
70 MPa) were evaluated (Venter et al., 2006, 2007). Furthermore, the authors studied the impact of moisture content, temperature, and Sc-CO2 pressure on the oil yield and seedbed compaction’s rate. Results through this work revealed obtaining up to 30% higher yield than that of conventional expression under the same conditions. Higher extraction yield was found for hulled seeds using GAME technology, as compared to the conventional expression. The authors concluded that oil displacement by dissolved Sc-CO2 was the major factor of increased oil yields (Venter et al., 2006, 2007). Fig. 11.2 shows an example of experimental design used for the oil extraction from oilseeds and nuts with GAME in batch mode. More recently the application of GAME technology to extract oil from tiger nuts was evaluated (Koubaa et al., 2015). GAME process was first studied by varying both pressures of Sc-CO2 and ME (10
30 MPa), then it was compared to these two processes applied separately. It was demonstrated that the better conditions for oil extraction from tiger nuts using GAME process were found using 20 and 30 MPa pressures for Sc-CO2 and ME, respectively. In addition, GAME process allowed faster oil extraction from nuts, reaching 50% yield after 10 min extraction, compared to only 10% and 20% when using Sc-CO2 and ME separately at 20 and 30 MPa pressures, respectively. Furthermore, the quantification of polyphenols in extracted oils using the three processes showed that GAME allowed the recovery of

Figure 11.2 Schematic setup in batch mode used for gas-assisted mechanical expression of oilseeds and nuts. ME, Mechanical expression.

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the highest amount of phenolics compared to Sc-CO2 and ME processes applied alone. It has been reported that polyphenol profiles, obtained by liquid chromatography—high resolution mass spectrometry, showed the presence of 57 compounds in oils extracted by GAME, followed by Sc-CO2 (48 compounds), and ME (27 compounds), concurring with the trends observed for total phenolic compounds (TPCs). Scanning electron microscopy images revealed an advanced cell damage using GAME compared to the applied separate processes. It was concluded that GAME represents a great opportunity to replace conventional methods for oil extraction from plant matrices (Koubaa et al., 2015). Mhemdi et al. (2016) have evaluated the efficiency of GAME and SAME (solute-assisted ME) technologies to recover oil from canola hulls and comparing these technologies with conventional SE (Mhemdi et al., 2016). The experimental setup is presented in Fig. 11.3. First, SE and SAME have been applied using hexane and green solvents (water, ethanol, and water/ethanol mixture) to extract efficiently oil and other bioactive compounds (polyphenols and proteins). In order to avoid the

Figure 11.3 Experimental setup of the extraction processes. GAME, Gas-assisted mechanical expression; ME, mechanical expression; SAME, solute-assisted mechanical expression; Sc-CO2, supercritical CO2; SE, solvent extraction. Source: From Mhemdi, H., Koubaa, M., Majid, A. E., & Vorobiev, E. (2016). Solute and gas assisted mechanical expression for green oil recovery from rapeseed hulls. Industrial Crops and Products, 92, 300
307.

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use of organic solvents, oil extraction yield was compared to that of GAME technology, after optimizing the extraction parameters [effective pressure, CO2 flow rate, and the impact of pretreatments (grinding and/or cooking)] (Mhemdi et al., 2016). Results show that the highest extraction yield (65%) was obtained with GAME using 35 MPa effective pressure, 8.5 kg/h CO2 flow, and without pretreatment (Fig. 11.4). The extraction yields obtained using ME and Sc-CO2 do not exceed 10% and 30%, respectively. It was concluded that the use of GAME technology allowed the recovery of oil without subsequent purification steps (removing the extraction solvent, meal desolvation), and without pretreatment. The efficiency of GAME for oil recovery was recently proved by Koubaa et al. (2017) for the valorization of olive kernel, a by-product produced during olive oil extraction process. In this study, aqueous liquid/solid extraction (LSE), ME, ScCO2, and GAME processes were compared when applied separately or consequently (ME 1 GAME), in terms of TPC and oil recovery yields. Results showed that although the high extraction yields TPC using LSE (61.4 6 1.3%), the extraction process is economically not viable. However, it was demonstrated that applying ME (1 h at 30 MPa), followed by GAME (1 h at 30 MPa ME and 10 MPa Sc-CO2 pressures), allowed recovering extracts enriched with TPC (  50% yield) and oil

Figure 11.4 Oil extraction kinetics from rapeseed hulls using GAME [30 MPa effective pressure (40 MPa ME 1 10 MPa Sc-CO2)], and Sc-CO2 (10 and 40 MPa). GAME, Gasassisted mechanical expression; ME, mechanical expression; Sc-CO2, supercritical CO2. Source: From Mhemdi, H., Koubaa, M., Majid, A. E., & Vorobiev, E. (2016). Solute and gas assisted mechanical expression for green oil recovery from rapeseed hulls. Industrial Crops and Products, 92, 300
307.

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(  80% yield), respectively (Fig. 11.5). Recovered phenolic compounds and oil were then identified using liquid and gas chromatography—mass spectrometry, showing no degradation and high oil quality compared to commercial virgin oil (Koubaa et al., 2017). Pilot-scale experiments performed by Mu¨ller et al. (2014) investigated the influence of process parameters for upcoming industrial applications of GAME technology (Mu¨ller et al., 2014). Piston press equipment was used to evaluate the effect of seed moisture content (ranging from 2% to 6.5%), CO2 pressure (ranging from 10 to 18 MPa), and temperature (ranging from 40 C to 120 C) on oil extraction yield, with and without gas assistance. The authors performed multistage pressing experiments to mimic the industrial-scale process conditions and analyzed oil quality and yields under different conditions. They clarified the phenomena involved in GAME process and presented a calculation model for oil yield increase explanation (Mu¨ller et al., 2014). All of these promising works used batch-processing modes for oil extraction from seeds and nuts. They showed the potential of GAME technology compared to conventional ones and to Sc-CO2 applied solely. Thus continuous processing plants have been proposed and patented. Fig. 11.6 shows some examples of equipment

Figure 11.5 (A) Total volume extraction fraction obtained by ME (2 h), GAME (2 h), and sequential process of 1 h ME and 1 h GAME of olive kernel. Mechanical pressure was fixed to 30 MPa, whereas Sc-CO2 pressure was fixed to 10 MPa. (B) Total phenolic compound and oil yields using ME sole, GAME sole, and a sequential process of 1 h ME and 1 h GAME. GAME, Gas-assisted mechanical expression; ME, mechanical expression; Sc-CO2, supercritical CO2; ME, mechanical expression. Source: From Koubaa, M., Lepreux, L., Barba, F. J., Mhemdi, H., & Vorobiev, E. (2017). Gas assisted mechanical expression (GAME) for the selective recovery of lipophilic and hydrophilic compounds from olive kernel. Journal of Cleaner Production, 166, 387
394.

Figure 11.6 Continuous plants proposed for oil extraction from seeds and nuts at industrial scale. (A and B) Adapted from Savoire, R., Lanoisele´, J. L., & Vorobiev, E. (2008). Mechanical continuous oil expression from oilseeds: A review. Food and Bioprocess Technology, 6(1), 1
16. (C) Adapted from Kartika, I. A., Pontalier, P. Y., & Rigal, L. (2005). Oil extraction of oleic sunflower seeds by twin screw extruder: Influence of screw configuration and operating conditions. Industrial Crops and Product, 22(3), 207
222.

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able to extract oil from seeds and nuts at industrial scale and in continuous mode (Crown Iron Works, 2006; Foidl, 1999; Hobbie, 2006; Koshevoy, Kosachev, & Mezetykov, 2012; Voges, Eggers, & Pietsch, 2008). According to the inventions reported in Fig. 11.6, it is possible to adapt a traditional screw press to be used for GAME. The screw press comprises a jacket, which proof-seals the pressing body and avoid the leak of CO2. Seeds/nuts are first prepressed then subjected to extraction by GAME. Press screw is hollow and comprises outlets wherethrough Sc-CO2 is introduced under pressure. Using this equipment, it has been shown that oil could be simultaneously extracted while feeding, and at least 96% recovery yield (based on total content) is reached (Foidl, 1999). Due to the high pressure applied to the material in the screw press the injected CO2 enters the system in supercritical state, increasing oil solubility. To avoid gas leaking from the system, press screw should contain three frustoconical taperings, which allow increasing the pressure by compressed materials over the gas one and thus constitute a seal. After overcoming a tapering the pressure naturally will drop somewhat again, allowing thus the diffusion of CO2 in the prepressed materials and the extraction of more oil (Fig. 11.6). Homann, Schulz, and Zmudzinski (2006) proposed and patented an alternative design, where the screw press contains of a prepressing zone, an extruder zone with closed barrel, where the CO2 is injected, and an open pressing zone, where both liquid and partially dissolved CO2 leave the press. Following this design, no pressuretight casing is necessary as part of the press itself is pressure tight, and restrictor elements between zones lead to the formation of nearly gas-tight material plugs. The feasibility of using GAME technology at industrial scale was investigated (Mu¨ller & Eggers, 2014). GAME screw-press equipment was used to extract rapeseed oils, and its performance for industrial-scale processing was evaluated. The test run was performed in a full production-scale run for 24 h. The test was operated as a full-press plant, extracting oil in two sequential steps as depicted in Fig. 11.7. The rapeseed educts were first prepressed in a cage screw at cold temperature. The resulting press cake was then fed into two screw presses configured in parallel in order to evaluate the effect of CO2 adding. One press was equipped with a local extruder zone where Sc-CO2 was injected. The average CO2 pressure was 12.55 MPa, and Sc-CO2 feed temperature was 345 K with an average mass flow rate of 111 kg/h. The second control press worked without CO2 injection. Both presses received the same feed of material and were each fed at the rate of about 3.1 ton/h. Results showed that the residual oil levels were reduced to 7.7% (w/w) when using Sc-CO2 at 12.5 MPa to assist oil extraction, compared to 9.9% (w/w) without gas assistance, under the same conditions. The obtained results indicated the achievement of a steady-state operation with improved oil and meal quality (especially when temperature decreased below 361 K). A predictive model of the increase in oil yield achievable with gas assistance was presented, and the results indicate that a temperature decrease below 361 K results in an even better oil yield. Economic analysis was performed based on energy consumption, CO2 supply, and investment costs. It was shown that the aforementioned costs can be offset by the

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Figure 11.7 Simplified flow scheme for a gas-assisted screw-press pressing rapeseeds at the industrial scale. Source: From Mu¨ller, M., & Eggers, R. (2014). Gas-assisted oilseed pressing on an industrial scale. Journal of the American Oil Chemists’ Society, 91, 1633
1641.

oil yield increase without taking into account the impact of increased oil and press cake quality. The analysis showed that GAME process leads to an increased profit margin of about 135.2 kh/year compared to conventional pressing process. The investment cost for the modification of an existing press was estimated to 350 kh. A payback period of 2.7 years was calculated for 14 years depreciation and 3.4% interest payments. On this basis the breakeven point is 64.7 kton of feed for one press. It was concluded that an investment in GAME would be profitable industrially (Mu¨ller & Eggers, 2014).

11.3.3 Advantages and limitations of gas-assisted mechanical expression technology As described above, GAME technology was developed to combine the high extraction yield of supercritical extraction and the high oil quality of ME but does not require the large quantities of solvent used in supercritical extraction. Nowadays, the feasibility and the effectiveness of this novel technique were sufficiently proven in the laboratory scale by using hydraulic presses with the injection of Sc-CO2. As compared to convention crushing process, the application of GAME allows gains at four levels: environment, quality, process, and energy (Fig. 11.8). First of all, the

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Figure 11.8 Advantages of GAME technology. GAME, Gas-assisted mechanical expression.

GAME application allows overcoming all the issues associated with the use of hexane, mainly its emission in the atmosphere (2 L of hexane per ton of treated seeds). The second advantage concerns the high oil (rich in phenolic compounds and less concentrated in phospholipids) and meal (preservation of protein quality) quality obtained using GAME technology. More importantly, the crushing process would be simplified: meal desolvation and solvent evaporation steps will be suppressed, and the refining can be simplified allowing an important energy save. As GAME is an interesting option for continuous pressing processes in screw presses, industrial development is currently going in that direction but further investigations are still needed. These investigations should include additional experiments using an industrial-scale screw press in order to validate the transferability of tendencies observed in hydraulic pressing experiments to continuous pressing. Technically, the design of the gas injection and its recycling are crucial and should be well controlled beacause it is important to realize a sufficient contact time between gas and solid materials, especially against the background of today’s short residence times in screw presses. Furthermore, it is important to ovoid a possible uncontrolled blowout of the solid material by internal gas pressure. More importantly, an efficient design should be found to ensure the tightness at the entrance and the exit of the press. From an economic point of view and besides the sought efficiency increase the energy and CO2 demand of the total process should be taken into account. In this context, CO2 recycling is one of the major challenges for the economic profitability of the process. The oil composition under industrial conditions and the state of the press cake after processing are issues that have to be taken into account. Moreover, a possible change in pressing temperature caused by carbon dioxide expansion has not been discussed much so far. Depending on the kind of process realization, these effects may not be negligible.

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Green Food Processing Techniques

Conclusion

GAME seems to be a promising technique for oilseed extraction. Its implementation may be cost effective in small crushing units where hexane extraction is very costly due to low throughput or a lack of infrastructure. In future works the increase in oil quality should be considered as well as improved press cake quality. The latter is more than just a by-product; it is a fundamental issue for smaller oil mills. In fact the price of vegetable protein has risen in recent years, and this trend will continue in the coming years. GAME process preserves the quality of proteins in the meal. In this actual economic context the cost-effective analysis has to be evaluated for improved oil and press cake quality. In large-scale industrial applications, GAME is a promising option to relieve chronically overcharged extraction bottlenecks and increase plant workload. Despite the promising technical advances in GAME equipment design and the good results (yield and oil quality) obtained by pilot and industrial testing this technology, further investigations are required using the major oilseed and nut crops. Deep economic viability study of the whole process (extraction 1 refining 1 desolvation) is still needed. Finally, the applicability of GAME technology for other biomaterials rich in oil (yeasts, algae, insects, and fruits) should be investigated.

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24. Akpan, U. G. (2012). Oilseeds. Rijeka, Croatia: In Tech. Anastas, P. T., & Warner, J. C. (2000). Green chemistry: Theory and practice. ,bases. bireme.br.. Anderson, D. (1996). A primer on oils processing technology. In Y. H. Hui (Ed.), Bailey’s industrial oil and fat products (pp. 10
17). John Wiley & Sons. Balvardi, M., Mendiola, J. A., Castro-Go´mez, P., Fontecha, J., et al. (2015). Development of pressurized extraction processes for oil recovery from wild almond (Amygdalus scoparia). Journal of the American Oil Chemists’ Society, 92, 1503
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Encapsulation technologies for polyphenol-loaded microparticles in food industry

12

ˇ Dusanka A. Popovic´ 1, Danijel D. Milinciˇ c´ 1, Mirjana B. Pesiˇ c´ 1, Ana ˇ ˇ c´ 1,2, Zivoslav M. Kalusevi Lj. Tesiˇ c´ 3 and Viktor A. Nedovic´ 1 1 Department of Food Technology and Biochemistry, Faculty of Agriculture, University of Belgrade, Belgrade, Serbia, 2Institute of Meat Hygiene and Technology, Belgrade, Serbia, 3 Faculty of Chemistry, University of Belgrade, Belgrade, Serbia

12.1

Introduction

Encapsulation can be defined as a process in which substances (active compounds) are entrapped in carrier material in order to form micrometer- or nanometer-sized particles and which represents useful tool to improve delivery of bioactive compounds (Nedovic, Kalusevic, Manojlovic, Levic, & Bugarski, 2011; Shishir, Xie, Sun, Zheng, & Chen, 2018). Carrier material as protective barriers between active compounds and surrounding food components plays an important role and influences active compounds’ protection, stability, and in the later stage delivery. Encapsulation is widely used in the production of functional food as it enhances supply of bioactive compounds, micronutrients, probiotics, etc. (Donsı`, Sessa, & Ferrari, 2016; Krasaekoopt & Bhandari, 2012; Nedovi´c, Kaluˇsevi´c, Manojlovi´c, Petrovi´c, & Bugarski, 2013). Therefore encapsulation as a complex process requires fundamental knowledge of colloid and interface chemistry, material science, and indepth understanding of active compounds’ stabilization (Nedovi´c et al., 2013; Vincekovi´c et al., 2017). Encapsulation technology is successfully applied in food as well as in pharmaceutical industries. Depending on the particle sizes there are two most common approaches in encapsulating technology: micro- and nanoencapsulation, both aiming to improve functionality and/or effective recovery of bioactive compounds. In encapsulation process, microparticles (1
1000 μm), submicron particles (B1 μm), and nanoparticles (one to several hundred nanometers) can be formed using various micro- and nanoencapsulation techniques (Shishir et al., 2018). Microencapsulation is a technique where solid, liquid, or gaseous phases (known as core, fill, active, internal or payload phase) are entrapped by a coating material (known as wall, capsule, shell, carrier material, or matrix) (Aguiar, Estevinho, & Santos, 2016). There are many reasons for microencapsulation, such as protection of unstable compounds from unfavorable environmental conditions, controlled release of compounds, preservation of antioxidant activity until consumption, Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00012-4 © 2019 Elsevier Inc. All rights reserved.

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masking of undesirable taste (e.g., astringency). Some of the major requests in encapsulation of bioactive components that should be fulfilled are the formation of the shell around the material to be encapsulated (1); ensuring that undesired leakage does not occur (2); and ensuring that undesired materials are kept out (3) (Botelho, Canas, & Lameiras, 2017; Mozafari et al., 2008). The potential encapsulation material for a food application must be generally recognized as safe (GRAS) (Nedovic et al., 2011; Shishir et al., 2018). The most extensively used materials for encapsulation in food sector are carbohydrate polymers (alginate, chitosan, gums, starch, and starch products), proteins (egg proteins, hydrolyzed protein, milk and whey proteins, soy proteins, wheat proteins, and zein), and lipids (glycolipids, phospholipids, waxes, mono- and diglycerides) (Wandrey, Bartkowiak, & Harding, 2010). Plants are rich source of high-value bioactive compounds, among which polyphenols have a noticeable role. Many studies indicate the importance of polyphenols, which have significant health benefits and antidisease properties (Alrgei et al., 2016; Beres et al., 2017; Cicero & Colletti, 2017; Croft et al., 2018; Cvetanovi´c et al., 2017; Fotiri´c Akˇsi´c et al., 2015; Miˇsi´c et al., 2015; Nati´c et al., 2015; Panteli´c et al., 2016; Pavlovi´c et al., 2016; Ristivojevi´c et al., 2015; Stanisavljevi´c et al., 2015, 2016). However, they are very unstable, susceptible to degradation when exposed to unfavorable conditions during processing and storage, they are sensitive to oxygen, light, moisture, and heat (Rodrı´guez, Martı´n, Ruiz, & Clares, 2016). Also, in many cases their application is limited due to their low solubility and bioavailability, fast release, or bitter taste and astringency (Nedovic et al., 2011, 2013; Shishir et al., 2018). So, the development of new functional food requires protection and incorporation of polyphenols and other health-promoting compounds without reducing their important functional characteristics. Encapsulation contributes to enhanced bioavailability, improved biological activity, controlled release, targeted delivery, and prolonged shelf life of bioactive compounds (Ariyarathna & Karunaratne, 2016; de Souza Simo˜es et al., 2017; Mozafari et al., 2008; Yang et al., 2017). Encapsulation of biologically active compounds is a nowadays well-studied area both in micro- and nanoscales and is already adopted by some industries. Application of encapsulating technology has enhanced numerous final food products characteristics and functions. The polyphenol-loaded particles are already used in industry, where a wide range of products can be found. Some of the examples from the market are products with microencapsulated polyphenols (such as hydroxytyrosol and tyrosol) extracted from olive fruits, curcumin, green tea extracts (GTEs), epigallocatechin gallate (EGCG), and others. The fact that those products found its way to the consumers confirms the use of polyphenol-loaded microparticles in the food industry as justified.

12.2

Matrices for polyphenol-loaded microparticles production and their application in food

As encapsulation leads to improvement of stability, bioactivity, and bioavailability of polyphenol compounds in vivo and in vitro, the materials used for encapsulation

Encapsulation technologies for polyphenol-loaded microparticles in food industry

337

must satisfy certain number of criteria (Nedovic et al., 2011). They should be stable, food-grade, bio-grade, biocompatible; they should preserve polyphenols at different conditions of processing and storage, without chemical interaction of food matrix with bioactive compounds; also, they have to possess unique properties such as emulsifying and gelling ability, flexibility, low cost (Botelho et al., 2017; Jain, Thakur, Ghoshal, Katare, & Shivhare, 2016; Nedovic et al., 2011, 2013; Shishir et al., 2018). For adequate encapsulation of bioactive components it is very important to understand the physicochemical and rheological properties of the material used for encapsulation.

12.2.1 Polysaccharide-based carrier for phenolic compounds Polysaccharide-based carriers such as starch, amylose, cellulose, carboxymethyl cellulose (CMC), dextrins, maltodextrins (MDs), cyclodextrins (CDs), β-form CDs (β-CDs), pectins, alginate, gums, or their modified forms have been used for encapsulation of polyphenols or extracts rich in phenolic compounds (Table 12.1). The selection of carrier depends on the type of encapsulation or the molecular and physicochemical characteristics of the active compounds. For example, starch is used for encapsulation of hydrophobic polyphenols because of its hydrophilic properties; however, modified starches (cross-linked, acetylated, hydroxypropylated, dialdehyde starch, etc.) can be specifically produced with improved functional characteristics such as enhanced hydrophobicity, higher heat stability, adhesivity, better protect against oxidation, reduced swelling ability, or emulsification capability (Fathi, Martı´n, & McClements, 2014; Shishir et al., 2018; Wandrey et al., 2010). Corn starch has good characteristics for delivery of bioactive compounds. In the study of Teixeira, Navarro, Martino, and Deladino (2015), corn starch treated by high hydrostatic pressure had an improved ability to carry minerals and yerba mate polyphenols [dominant polyphenols are chlorogenic acid (CGA) esters and isomers] and thus formulated carriers can be suitable additives or ingredients for a wide range of functional foods. Starch is mainly made of two fractions—linear amylose and branched amylopectin. According to Lorentz et al. (2012), amylose complexation can be used to encapsulate CGA and 4-O-palmitoyl-CGA. CGA possesses significant antioxidant (effective scavenger) (Shi et al., 2006) and antimicrobial properties (Zhu, Zhang, & Lo, 2004). However, due to high hydrophilicity, low bioavailability, tendency to degrade, or autoxidate this bioactive compound during processing and storage, it should be protected to be effectively used for the enrichment of food products (Lorentz et al., 2012). By modifying the starch (hydrolysis or enzymatic modification), different forms of dextrins are formed, such as MDs, α-, β-, γ-CDs, which can successfully be used as carriers for polyphenols. MDs very effectively protect polyphenolic compounds from oxidation and degradation during drying and processing (Nunes et al., 2014; Paini et al., 2015; Shishir et al., 2018). The application of MD as a carrier in optimized systems can contribute to improve the retention of polyphenols with longer shelf life (Shishir et al., 2018). Combination of MD with other carriers, such as gums, pectins, and chitosan, contributes to the improvement of emulsification properties, stability, prevention of the loss of polyphenols or controlled release

Table 12.1 Microencapsulation of phenolics—different types of carriers. Type of encapsulation

Carrier material

Polyphenols/extracts rich in polyphenols

Observations and application

Reference

Native starch and treated starch by HHP can be successfully used as bioactive carrier for minerals and YMP and can be used as additive or as functional food ingredient System obtained by incorporation of a starch-Zn carrier into the calcium alginate beads with YMP showed a strong inhibitory activity toward free radicals. The system thus obtained can be used in the formulation of new antioxidant-rich food This system allows effective encapsulation of chlorogenic acid. The microstructure, textural characteristics, viscoelastic properties, chlorogenic acid release rates, and antioxidant stability were optimized depending on the added amount of starch Phosphorylated starch can be successfully used as a carrier for encapsulation of anthocyanins; it showed a low viscosity and high solubility. Prepared anthocyanin microparticles can be used in various food systems Spray-drying can be effectively used for microencapsulation of OP polyphenols. Microparticles obtained by this process showed good stability at storage conditions, significant antioxidant properties and can be used in food production

Teixeira et al. (2015)

Polysaccharide-based carriers for polyphenol microencapsulation Minerals and YMP (dominant polyphenols are chlorogenic acid esters and isomers) Zn and YMP

Not specified

Corn starch treated with high hydrostatic pressure

Not specified

Corn starch-calcium alginate

Not specified

Modified tapioca starch-filled calcium alginate hydrogel beads

CGA

Spray-drying

Phosphorylated starch

Purple maze anthocyanins

Spray-drying

MDs with 16.5
19.5 DE

Olive pomace polyphenols

Lopez-Cordoba et al. (2014)

Lozano-Vazquez et al. (2015)

Garcı´a-Tejeda et al. (2016)

Paini et al. (2015)

Freeze-drying

MD with 8 and 18.5 DE

Phenolic-rich cloudberry extract (mainly ellagitannins)

Spray-drying and freeze-drying

MD (,20 DE)

Polyphenol extract from Averrhoa carambola pomace

Spray-drying

MD

Bordo grape pomace extracts (anthocyanins)

Spray-drying

MD (DE10)

Jabuticaba extracts (anthocyanins)

Freeze-drying

9% (w/w) MD (DE10) and gum arabic

Red wine C. Sauvignon (rich in polyphenols, especially anthocyanins)

Microencapsulation improved the storage stability of cloudberry phenolics and their recovery as high-value compounds. The better results were obtained when MD with 8 DE was used Highest encapsulating efficiency was obtained by freeze-drying methods. This microparticles can be added to different food systems to enhance their antioxidant properties The results indicate that anthocyanins in the spray-dried samples showed good stability during storage and have a high potential to be used as a natural pigments with functional properties. Anthocyanins can also showed good antimicrobial properties MJE was added in fresh sausages as natural dye with antioxidative and antimicrobial properties. The different dosages of MJE were added and it prolonged shelf life and stability during storage. Also, the addition of 2% MJE might be considered as a replacement for cochineal carmine in fresh sausages Conditions during storage for wine powder, such as temperature 38 C and aw 5 0.11, have the best impact on stability of most polyphenols. This way formed wine powder may be used for the enrichment of healthy powder drinks

Laine, Kylli, Heinonen, and Jouppila (2008)

Saikia, Mahnot, and Mahanta (2015)

De Souza et al. (2014)

Baldin et al. (2016)

Rocha-Parra et al. (2018)

(Continued)

Table 12.1 (Continued) Type of encapsulation

Carrier material

Polyphenols/extracts rich in polyphenols

Observations and application

Reference

Spray-drying

MD/gum system

Propolis extracts (dominant polyphenols are galangin and pinocembrin)

Busch et al. (2017)

Inclusion complexation

β-CDs

CGA

Inclusion complexation

β-CD and 2HP-β-CD

CGA

Inclusion complexation

HP-β-CDs, maltosylβ-CDs, β-CDs

Quercetin and myricetin

Inclusion complexation

Maltosyl-β-CDs, β-CDs

Resveratrol

MD mixed with gums had a better characteristic from MD alone. Addition of gums improved particle integrity, antioxidant activity, and encapsulation efficiency of some polyphenols, especially quercetin. The use of propolis as an encapsulated powdered additive widens its alcohol-free dosage applications The stability of chlorogenic acid was improved by covering with β-CD inclusion complex, which was confirmed by measurement of absorbance change during 20 weeks. The aim of the research was to develop β-CD complexes with CGA for adequate industrial applications Inclusion complexes showed high antioxidative activity. This suggested possibility of their practical application in the food industry as enhanced antioxidants and copigments The complexation of polyphenols improved their solubility and bioavailability, prevented enzymatic oxidation, and enabled application of quercetin and myricetin in functional food The complexation of resveratrol with CDs increased total resveratrol concentration in aqueous solution and protected resveratrol from oxidation. This CDs’ complexing approach allows effective use of resveratrol

Zhao et al. (2010)

Shao, Zhang, Fang, and Sun (2014)

Lucas-Abella´n, Fortea, Gabaldo´n, and Nu´n˜ez-Delicado (2008) Lucas-Abellan et al. (2007)

Inclusion complexation

HP-β-CD

Kaempferol, quercetin, and myricetin

Inclusion complexation

β-CDs, HP-β-CD

Resveratrol and other polyphenols (Polygonum cuspidatum)

Inclusion complexation followed by freeze-drying

β-CDs

Trans-cinnamaldehyde, eugenol

Ionic gelation

CH-CNC

Blueberry anthocyanin extract

Antioxidant activity of examined phenols increased when they were entrapped in the hydrophobic cavity of CDs. Kaempferol had the highest, while myricetin had the lowest antioxidant activity Encapsulation within CDs may be used for improvement of solubility, stability, and bioavailability of resveratrol and other polyphenols. This inclusion system can be successfully used as food supplement The results indicate that encapsulation of examined antimicrobial compounds may be effective at inhibiting pathogens and can be applied in food systems where Gram-positive and negative bacteria could present a risk CNC may be successfully used as the macroion crosslinking agent in chitosan-based microencapsulates for the improvement of encapsulation efficiency and stability of blueberry anthocyanin extracts

Mercader-Ros, LucasAbellan, Fortea, Gabaldon, and Nunez-Delicado (2010) Mantegna et al. (2012)

Microencapsulated anthocyanin-rich black carrot concentrate was used as a natural colorant in yoghurt. Formed microparticles protected the color by increasing its stability GTE-loaded microparticles were added to biscuits dough. Both protein matrices had high encapsulation efficiencies and effectively protected catechins during a thermal treatment, while the microencapsulation of GTE had no impact on the acceptability of biscuits

Bilek et al. (2017)

Hill, Gomes, and Taylor (2013)

Wang et al. (2017)

Protein-based carriers for polyphenol microencapsulation Emulsion/heat gelation method

Whey-protein hydrogels

Anthocyanin-rich black carrot concentrate

Electrospraying

Zein and gelatin

GTE (rich in EGCG and catechin)

Go´mez-Mascaraque, Hernandez-Rojas, et al. (2017)

(Continued)

Table 12.1 (Continued) Type of encapsulation

Carrier material

Polyphenols/extracts rich in polyphenols

Observations and application

Reference

Electrospraying

Protein-coated liposomes

Curcumin

Go´mez-Mascaraque, Sipoli, de La Torre, and Lo´pez-Rubio (2017)

Spray-drying

MDs and soybean proteins

Polyphenols and anthocyanins from pomegranate

Spray-drying

MD (12 DE) and MD combined with skimmed milk powder Mixtures of alginate and pectin with whey proteins or HMPC

Pomegranate peel extracts (rich in phenolic compounds)

CPI
CSG complex coacervates

Chia seed oil (main chia seed polyphenols are rutin and hesperidin)

Microencapsulation of curcumin within formed systems improved their bioaccessibility, successfully protected curcumin from degradation in PBS (pH 5 7.4), and gave the opportunity and idea for production of functional ingredients The anthocyanin encapsulation was significantly better when MD matrix was used as a carrier, compared with soybean protein isolates. This microparticles provided better protection and could be used for functional food production Crude and encapsulated pomegranate peel extract can be applied in food industry. Encapsulated extract improved the shelf life of hazelnut paste Combination of whey proteins and alginate was the best carrier for maximization of encapsulation efficiency of polyphenols and hydroxycinnamic acids. This systems can be successfully used for encapsulation of both hydrophilic and lipophilic active compounds The encapsulation enabled high oxidative stability. Spray-dried microparticles showed higher oxidative stability than the freeze-dried

Emulsion (W/O)/ internal ionic gelation

Complex coacervation followed by freeze and spray-drying

Polyphenols (Taraxacum officinale L.) and hydroxycinnamic acid

Robert et al. (2010)

Kaderides et al. (2015)

Belˇscˇ ak-Cvitanovi´c, Buˇsi´c, et al. (2016)

Timilsena, Adhikari, Barrow, and Adhikari (2016)

Not specified

Kafirin microparticles

Catechin and sorghum condensed tannins

Bioactive polyphenols, catechin, and sorghum condensed tannins were entrapped within porous kafirin microparticles. This encapsulation provided protection under simulated gastric conditions and controlled release of antioxidative phenolic compounds

Taylor, Taylor, Belton, and Minnaar (2009)

Codelivery of hydrophobic curcumin and hydrophilic catechin was enabled using W/O/ W emulsions. This way encapsulated polyphenols were four times more accessible compared to free curcumin and catechin Bioavailability of quercetin was improved, as well as its shelf life. Degradation of quercetin was slowed, which indicates that it could be used as interesting food additive Curcumin-loaded proliposomes were coated with micronized sucrose and characterized. Good preservation during storage and hygroscopicity showed that this is a promising technique for further curcumin uses

Aditya et al. (2015)

An in vivo study on rats examined anxiety and cognitive effects of quercetin liposomes. The authors concluded that carrier system provided efficient delivery to the central nervous system

Priprem et al. (2008)

Lipid-based carriers for polyphenol microencapsulation Double emulsion (W/O/W)

Different mixtures of compounds

Curcumin and catechin

Encapsulation in liposomes

Phospholipids

Quercetin

Encapsulation in liposomes

Phospholipids

Curcumin

Encapsulation in liposomes

Egg phosphatidylcholine and cholesterol

Quercetin

Toniazzo et al. (2017)

Silva et al. (2016)

CD, Cyclodextrins; CGA, chlorogenic acid; CH-CNC, chitosan-cellulose nanocrystals; CPI, chia seed protein isolate; CSG, chia seed gum; DE, dextrose equivalent; EGCG, epigallocatechin gallate; GTE, green tea extract; HHP, high hydrostatic pressure; HPMC, hydroxypropyl methylcellulose; HP-β-CD, 2-hydroxypropyl-β-CD; MD, maltodextrin; MJE, microencapsulated jabuticaba extract; OP, olive pomace; PBS, phosphate buffered saline; W/O, water-in-oil; W/O/W, water-in-oil-in-water; YMP, yerba mate polyphenols; β-CD, β-form CD.

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(Busch et al., 2017; Dag, Kilercioglu, & Oztop, 2017; Rocha-Parra, Chirife, Zamora, & Pascual-Teresa, 2018; Zhang, Mou, & Du, 2007). MDs with different dextrose equivalents (DEs) were tested as the carrier matrices for anthocyanin-rich extracts (Delgado-Vargas, Jimenez, & Pardes-Lopez, ˇ 2000; Ersus & Yurdagel, 2007; Kaluˇsevi´c, Levi´c, Calija, Mili´c, et al., 2017; ˇ Kaluˇsevi´c, Levi´c, Calija, Panti´c, et al., 2017; Robert et al., 2010; Yamashita et al., 2017) or as matrices for polyphenols of red wine (Sanchez, Baeza, Galmarini, Zamora, & Chirife, 2013). Yamashita et al. (2017) examined applications of MDs with 10 and 20 DEs as a carrier and obtained the results indicating that the powder produced with MD 10 DEs had a larger particle diameter and higher anthocyanin content and generally showed that it is possible to produce microcapsule from anthocyanin-rich extracts with high anthocyanin retention by freeze-drying. The obtained product can find its application in food industry as a food colorant or healthy ingredient. De Souza et al. (2014) showed that encapsulation of pigments from Bordo grape pomace extracts into MD can inhibit the growth of Staphylococcus aureus, Listeria monocytogenes, and enzyme arginase from ˇ Leishmania. Similar results are obtained by Kaluˇsevi´c, Levi´c, Calija, Panti´c, et al. (2017), where anthocyanin-rich black soybean coat extract was successfully encapsulated in MD, as well as in other matrices, showing antimicrobial properties. CDs can be used for encapsulation of low water-soluble compounds (such as individual polyphenols), as the external surface of CDs is hydrophilic, while the internal cavity is mostly hydrophobic. However, it contains water molecules whose amount varies depending on relative humidity (Duchˆene & Bochot, 2016; Shishir et al., 2018). CDs that are most commonly used for the molecular inclusion of compounds are the β-CDs. Due to their poor water solubility, CD derivatives with improved characteristics can be prepared and used (methyl-β-CDs, hydroxypropylβ-CDs, sulfobutyl ether-β-CDs, etc.) (Duchˆene & Bochot, 2016). CDs have found a wide application in food processing and as food additives (Astray, GonzalezBarreiro, Mejuto, Rial-Otero, & Simal-Ga´ndara, 2009). In the literature there are many examples where CDs and their derivatives can be effectively used for the encapsulation of phenolic compounds (Anselmi et al., 2008; Budryn et al., 2016; Chao, Wang, Zhao, Zhang, & Zhang, 2012; Ding, Chao, Zhang, Shuang, & Pan, 2003; Kfoury et al., 2016; Liu et al., 2015; Lucas-Abellan, Fortea, Lopez-Nicolas, & Nunez-Delicado, 2007; Tommasini et al., 2005; Tomren, Masson, Loftsson, & Tonnesen, 2007; Zhao, Wang, Yang, & Tao, 2010). For example, inclusion complexes formed between CGA with β-CD and (2hydroxypropyl)-β-CD showed higher antioxidant activity compared with the free CGA (Zhao et al., 2010). Also, when CGA/CD complexes were added to grape juice, the reduction of anthocyanin degradation was observed, which indicates that these complexes have significant potential for practical application in the food industry (Zhao et al., 2010). Cellulose can also be used for encapsulation purposes. The natural form of cellulose has several disadvantages, such as solubility in water and other common solvents. This can be overcome by using the modified cellulose that has significantly improved characteristics (Ðorðevi´c et al., 2016; Shishir et al., 2018). Some of the

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modified forms of cellulose are CMC, methylcellulose, hydroxypropyl cellulose, cellulose acetate, or newly produced cellulose nanocrystals and nanofibrillar cellulose (Shishir et al., 2018). According to Zheng, Ding, Zhang, and Sun (2011), polyphenolic extracts of bayberry encapsulated using ethyl cellulose were more stable than unencapsulated. Thus microparticles obtained this way can be used as stabilized natural antioxidants in the food. Also, certain modified forms of cellulose can be combined with other carriers such as chitosan in order to improve the effectiveness of polyphenol encapsulation (Wang, Jung, & Zhao, 2017). Alginates are often used for encapsulation (Balanˇc, Kaluˇsevi´c, et al., 2016; Isteniˇc et al., 2015; Lopez-Cordoba, Deladino, & Martino, 2014; Nedovi´c et al., 2013). According to Lopez-Cordoba et al. (2014), alginate in combination with corn starch as filler agent was used for encapsulation of yerba mate extract and thus formed capsules enabled protection of antioxidants and their application into food products. Also, in the study of Balanˇc, Kaluˇsevi´c, et al. (2016), alginate and alginate-inulin were successfully used for microencapsulation of polyphenols from carqueja extract. Chitosan is a linear polysaccharide composed of glucosamine and N-acetyl glucosamine units with unique characteristics such as nontoxicity, biocompatibility, and biodegradability and can be used for encapsulation of bioactive compounds and nutrients (Luo & Wang, 2014). Although chitosan has been approved (GRAS) for its use as a food additive by the FDA, the status of its use in food products depends on the regulations of different countries. Chitosan has been approved for dietary use in Italy, Japan, and Finland. European Food Safety Authority (2011) published a scientific opinion on food
health relationships related to chitosan without consideration of safety aspects. Sabaghi, Maghsoudlou, and Khomeiri (2015) reported that GTEs incorporated in chitosan had effective inhibitory effect on lipid oxidation and fungal growth during storage of walnut kernels, showing that coating has commercial potential for extension of shelf life and quality of walnut kernels. Trifkovi´c et al. (2015) examined water sorption and release properties of microparticles where glutaraldehydechitosan was used as carriers for Thymus serpyllum L. polyphenols. Regardless, those microparticles produced by emulsion crosslinking method showed excellent properties, due to the use of glutaraldehyde could not be used in food, but as drug delivery system for polyphenols. In another study, thyme extract polyphenols were incorporated into different films. Chitosan compared with starch showed the lower delivery rate because of the strong polyphenol
chitosan bonding, but it also showed notable antioxidant activity (Talo´n, Trifkovic, Vargas, Chiralt, & Gonza´lezMartı´nez, 2017). Chitosan is often combined with other natural polysaccharides (alginate, pectin, carrageenan, different types of gums, CMC, etc.) by forming complexes that can be used as carriers (Belˇscˇ ak-Cvitanovi´c et al., 2011, 2015; Luo & Wang, 2014). According to Belˇscˇ ak-Cvitanovi´c et al. (2011), polyphenolic compounds from traditional medicinal plants encapsulated in alginate
chitosan system (enhanced using ascorbic acid for the solubilization of chitosan) had significant antioxidative potential and could be applied in food products. Deladino, Anbinder, Navarro, and

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Martino (2007) showed that alginate and alginate/chitosan can be successfully used for the encapsulation of polyphenols from yerba mate extracts and applied for food supplementation. Combination of alginate with proteins and pectin/chitosan coating provided the maximum loading efficiency of green tea polyphenols and improved its physical and morphological properties (Belˇscˇ ak-Cvitanovi´c et al., 2015). Also, according to Karaˇca et al. (2019), immortelle (Helichrysum italicum) water extract was encapsulated by various alginate-protein matrices, which also served as edible films. Other polysaccharide-based carriers such as pectin and gums showed potential for encapsulation of polyphenols, too. Pectin is nontoxic and not digestible by intestinal enzymes, but pectinolytic enzymes totally degrade it (de Souza et al., 2013). Furthermore, pectin has excellent gelling properties, good biocompatibility, and biodegradability and by derivation its functional properties can be upgraded (such as solubility and hydrophobicity) (by Chen et al., 2015). De Souza et al. (2013) showed that pectin formulations gave the highest retention of magniferin in microparticles with Polysorbate 80 (Tween 80) as emulsifier. Gums and MD-gums combination were successfully applied for the encapsulation of antioxidant phenolic compounds extracted from spent coffee grounds (Ballesteros, Ramirez, Orrego, Teixeira, & Mussatto, 2017).

12.2.2 Protein-based carrier for phenolic compounds Proteins have various functional properties, such as emulsification, foaming, water binding capacity, and gelation, which gives them numerous opportunities for application in the food industry (Bara´c et al., 2011, 2012; Bara´c, Pesic, Stanojevic, Kostic, & Bivolarevic, 2015; Chen, Remondetto, & Subirade, 2006). Proteins functional characteristics indicate the possibility of their use as matrices for the delivery of bioactive components. They are effective carriers for both hydrophobic and hydrophilic compounds and functional particles that can be used for various types of food (Chen et al., 2006). The most commonly used proteins for encapsulation of polyphenols are casein, whey proteins, gelatin, collagen, as well as cereal (maize, wheat, barley, etc.), soy and pulse proteins (Jia, Dumont, & Orsat, 2016; Shishir et al., 2018) (Table 12.1). Polysaccharide
protein complex coacervates also may be used for encapsulation of numerous active compounds and ingredients (Devi, Sarmah, Khatun, & Maji, 2017). Several authors suggested the possible application of whey protein hydrogels ¨ zkan, 2017), (Betz & Kulozik, 2011; Oidtmann et al., 2012; Bilek, Yılmaz, & O whey-protein isolates (Flores, Singh, Kerr, Pegg, & Kong, 2014; Flores, Singh, & ˇ ´ Kong, 2014; Saponjac, Cetkovi´ c, et al., 2016), and skimmed milk powder ˇ ˇ (Kaluˇsevi´c, Levi´c, Calija, Mili´c, et al., 2017; Kaluˇsevi´c, Levi´c, Calija, Panti´c, et al., 2017) for microencapsulation of anthocyanins. Serrano-Cruz, Villanueva-Carvajal, Rosales, Da´vila, and Dominguez-Lopez (2013) used whey protein, CMC, and pectin mixtures for entrapment of Roselle’s (Hibiscus sabdariffa L.) polyphenols

Encapsulation technologies for polyphenol-loaded microparticles in food industry

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concluding that their release can be predicted by changing the ratio of different components in matrix. In several studies soy proteins and their isolates have been successfully applied ˇ ´ as carriers for polyphenols (Hidalgo, Brandolini, Canadanovi´ c-Brunet, Cetkovi´ c, & ˇ ˇ ˇ Saponjac, 2018; Robert et al., 2010; Saponjac, Canadanovi´ c-Brunet, et al., 2016; ˇ ´ Saponjac, Cetkovi´ c, et al., 2016). Soy protein isolate (SPI) was compared with MD as a matrices for anthocyanins and the encapsulating efficiency of SPI was superior to MD, but MD had the lower degradation rate constants and showed better characteristics during storage (Robert et al., 2010). The study of Trifkovi´c et al. (2018) demonstrated the potential of alginate/SPI matrixes to be used for encapsulation of saffron extract. The obtained microparticles showed good characteristics regarding stability, morphology, and overall possibility to be applied in development of functional foods. Catechins are group of polyphenols frequently entrapped within milk proteins. Green tea catechins containing epicatechin (EC) and EGCG were successfully encapsulated in oil-in-water emulsions, which were more stable with addition of ovalbumin. In addition, EGCG showed better synergy with ovalbumin compared to EC (Almajano, Delgado, & Gordon, 2007). The interactions between polyphenols and proteins may also serve for formation of protein
polyphenolic coating. Lau et al. (2017) formed protein
tannic acid multilayer films, where tannic acid serves as a cementing agent between layers of proteins, controlling the thickness of film and also contributing to the antioxidative properties of the system. The coating created on this way can serve as a carrier for various types of functional food ingredients, providing them targeted delivery to small intestine. Water insoluble proteins (such as zein) are promising matrices for the production of colloidal particles for encapsulation of water-soluble bioactive compounds. Donsı`, Voudouris, Veen, and Velikov (2017) demonstrated that zein particles combined with sodium caseinate improved functionality, antioxidative activity, and encapsulation efficiency of water-soluble polyphenols such as EGCG. Go´mezMascaraque, Hernandez-Rojas, et al. (2017) showed that EGCG-rich green tee extracts encapsulated within zein and gelatin can be applied in real food systems by adding in biscuits dough. The encapsulation of curcumin in a chickpea protein matrix protected curcumin from heat and light improving its stability (Ariyarathna & Karunaratne, 2016). This study showed that the release of curcumin from the protein matrix is pH dependent (at pH 2 is nearly 100%). Pa¸scal˘au et al. (2015) encapsulated curcumin in order to examine its antitumor activity. For this purpose, curcumin was entrapped within bovine serum albumin/polysaccharide multilayer coating, and these particles affected the tumor cells even at lower concentrations, which indicated potential usage of this polyphenol as strong antitumor agent. One of the powerful possibilities of polyphenol usage in functional food formulation is the inhibition of enzyme activity, due to binding of polyphenol with enzymes which have protein structure. In the study reported by Links, Taylor, Kruger, and Taylor (2015), kafirin was used as a protective carrier for sorghum

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Green Food Processing Techniques

condensed tannins. This coating protected polyphenols during digestion, thus retaining inhibitor activity against carbohydrate digesting enzymes in small intestine and consequently attenuated hyperglycemia.

12.2.3 Lipid-based carrier for phenolic compounds Apart from already known lipid carriers, such as phospholipids, fatty acids, or waxes, some of delivery systems developed for encapsulation of hydrophilic compounds are double emulsions (duplex or multiple emulsions), liposomes, liquid crystalline nanostructures, niosomes, bilosomes, cubosomes, etc. (Aditya, Espinosa, & Norton, 2017). Some of these lipid carriers are only used for nanosized particles. Due to special challenge to develop food products enriched with hydrophilic components which are sensitive and unstable within the complex matrix of food, an adequate colloidal system for the delivery of hydrophilic molecules is necessary (Aditya et al., 2017). Certain polyphenols are among the hydrophilic compounds that require lipid based carriers defined such above mentioned (Table 12.1). Lipidbased carriers are being formed to deliver hydrophobic polyphenols with low bioavailability, because it is closely related to poor aqueous solubility (Aditya et al., 2017). For example, polyphenols such as curcumin and catechin are highly sensitive to oxidation and they have low bioavailability, but by forming water-in-oil-in-water (W/O/W) double emulsion they can be effectively encapsulated (Aditya et al., 2015). Encapsulation of hydrophilic catechin and hydrophobic curcumin within emulsion improved their stability and bioavailability (Aditya et al., 2015). Oil-inwater emulsions can protect important characteristics of different polyphenolic compounds, such as caffeic acid (Almajano, Carbo´, Delgado, & Gordon, 2007) or tea infusions, containing mainly catechins (Almajano, Carbo´, Jime´nez, & Gordon, 2008). Components such as gallic acid, catechin, and quercetin can be added into O/W emulsions to improve their stability and delay lipid autoxidation in emulsions (Mattia, Sacchetti, Mastrocola, & Pittia, 2009). The significant retention of antioxidant activity of polyphenols from grape seed extract, apple polyphenol extract, and olive leaf extract was enabled using a combination of soy lecithin and sodium caseinate as carrier materials, showing that protein
lipid emulsions are suitable for polyphenols such as catechin, EC, gallic acid, or oleuropein (Kosaraju, Labbett, Emin, Konczak, & Lundin, 2008). Quercetin liposomes, made out of egg phosphatidylcholine, cholesterol, and quercetin showed anxiolytic and cognitive activities in vivo in a lower dose and a faster rate providing efficient delivery (Priprem, Watanatorn, Sutthiparinyanont, Phachonpai, & Muchimapura, 2008). In another study, encapsulation of quercetin in liposomes enhanced its bioavailability and emphasized its potential use in dried food. The experiment showed that the encapsulated quercetin had not degraded after 100 days of storage (Toniazzo, Peres, Ramos, & Pinho, 2017). Curcumin-loaded proliposomes, produced by coating of micronized sucrose and hydration of phospholipids powders, were able to preserve around 80% of the initial amount of curcumin (Silva, Jange, Rocha, Chaves, & Pinho, 2016).

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Examples of lipid-based carriers for polyphenolic components are not as numerous as polysaccharide or protein-based ones. Lipids as carriers are suitable for spray-chilling and spray-cooling techniques. Those low-cost techniques are relatively easy to apply and scale up without requiring the use of organic solvents and the application of high temperatures in the process. Therefore those encapsulation techniques may facilitate the development and production of novel, functional food products solving some technological challenges associated with the utilization of compounds that are highly reactive and unstable (Okuro, de Matos Junior, & Favaro-Trindade, 2013).

12.3

Techniques for polyphenol-loaded microparticles production and applications

Numerous techniques for microparticles production can be roughly divided to mechanical (or physical) techniques, based on distribution of solution, emulsion or dispersion using mechanical processes, and chemical techniques, where formation of a coating material around a core substance takes place in liquid phase (de Souza Simo˜es et al., 2017; Krasaekoopt & Bhandari, 2012). There are a lot of techniques that are available, and they are constantly optimized in order to secure bioactive properties of different core compounds (Fig. 12.1). Although there is no standard method of encapsulation, there are some basic important factors that need to be considered before choosing of proper technique, such as core and matrix molecular weight, polarity, solubility, particle size distribution, encapsulation efficiency, and shape (de Souza Simo˜es et al., 2017; Krasaekoopt & Bhandari, 2012).

12.3.1 Spray-drying Spray-drying microencapsulation process must rather be considered as an art than a science because of the many factors to optimize and the complexity of the heat and mass transfer phenomena that take place during the microcapsule formation. Gharsallaoui, Roudaut, Chambin, Voilley, and Saurel (2007)

Spray-drying, one of the oldest techniques, is commonly used for encapsulation of flavors, lipids, carotenoids (Gharsallaoui et al., 2007). Generally, it can be divided into few phases—dissolving, emulsifying, or dispersing the core compounds, atomization, and spraying (Ðorðevi´c et al., 2015; Gharsallaoui et al., 2007). During this drying process, the liquid (solution/emulsion/dispersion) is atomized to tiny droplets that can be quickly mechanically dehydrated by contact with hot air in the spray-drier chamber, where microcapsules are formed and core compounds are entrapped. Fast evaporation that occurs in few seconds or milliseconds is very important. Thermolabile carriers can keep their structure, which is essential to its bioactive function, although temperature of air used in this process is high (up to

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Green Food Processing Techniques

Spray drying

Freeze drying

Fluid bed coating

Matrix type

Matrix type

Coated matrix type

Emulsification

Extrusion

Liposomes

Oil

Matrix and reservoir type

Water

Complex coacervation

Molecular inclusion

Cross-linked protein shell

Matrix

Water-soluble polyphenols

Liposoluble polyphenols

Cyclodextrins Polyphenols

Coating

Hydrophilic head with hydrophobic tails

Figure 12.1 Schematic view of different types of microparticles regarding applied encapsulation techniques.

220 C). Development of powders with improved physical properties and the possibility of reaching higher yields are enabled, thanks to the addition of numerous carrier materials (Castro-Rosas et al., 2017; Ðorðevi´c et al., 2015; Kaluˇsevi´c, Levi´c, ˇ ˇ Calija, Mili´c, et al., 2017; Kaluˇsevi´c, Levi´c, Calija, Panti´c, et al., 2017). It is a low-cost and well-known technique, so it is clear why this method is used for 90% of all industrially produced microencapsulates. Its disadvantages are different shape and size of particles and their tendency toward aggregation (Ðorðevi´c et al., 2015). Numerous applications of spray-drying technique used for polyphenol entrapment can be found in literature (Baldin et al., 2016; Ballesteros et al., 2017; Belˇscˇ ak-Cvitanovi´c et al., 2015; de Souza et al., 2014; Garcı´a-Tejeda, SalinasMoreno, Herna´ndez-Martı´nez, & Martı´nez-Bustos, 2016; Garofuli´c, Zori´c, Pedisi´c, & Dragovi´c-Uzelac, 2017; Isailovi´c et al., 2013; Kaderides, Goula, & Adamopoulos, 2015; Machado et al., 2018; Paini et al., 2015). Beside advantages provided by encapsulation, polyphenols are often extracted from food industry byproducts, where thanks to usage of waste an eco-friendly dimension was also present. For example, olive pomace polyphenols (Aliakbarian et al., 2018) and olive leaves extract, which is rich in polyphenols (Urzu´a et al., 2017), can serve as valuable source of polyphenols, and their encapsulation proved to be effective, enabling potential functional role in food. Fruit processing by-products have been widely studied and used for encapsulation. Fruit peel, such as pomegranate peel

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(Kaderides et al., 2015) or jabuticaba fruit peel (Cabral et al., 2018), as well as citrus processing by-products (Lauro et al., 2015) and grape pomace (Kaluˇsevi´c, Levi´c, ˇ ˇ Calija, Mili´c, et al., 2017; Kaluˇsevi´c, Levi´c, Calija, Panti´c, et al., 2017; Tolun, Altintas, & Artik, 2016) were successfully used as a source of polyphenols, encapsulated using spray-drying. The grapefruit juice bioflavonoid naringin can be more soluble when it is spray-dried with resistant MD used as a carrier (Pai, Vangala, Ng, Ng, & Tan, 2015). Also, the encapsulation of propolis by this technique enabled protection of polyphenols such as galangin, pinocembrin, and quercetin (Busch et al., 2017). Garofuli´c et al. (2017) suggested that spray-drying is useful for sour cherry juice encapsulation, which leads to its polyphenolic content preservation.

12.3.2 Freeze-drying Freeze-drying, a low temperature dehydration process, is carried out at lower temperatures compared to spray-drying and because of this unstable compounds can be encapsulated with diminished risk (Morais et al., 2016). However, freeze-drying is slow, costly process, requiring a lot of energy (Nedovic et al., 2011). Freeze-drying was proved to be a better technique of green tea polyphenols encapsulation compared to the spray-drying method, because of higher encapsulation efficiency and better antioxidant activity (Pasrija, Ezhilarasi, Indrani, & Anandharamakrishnan, 2015). On the other hand, the work of Ramı´rez, Giraldo, and Orrego (2015) that modeled and compared spray and freeze-dried encapsulates showed that spray-dried particles were superior to freeze-dried in terms of storage stability. Among a number of different core materials encapsulated by freeze-drying, red wine is very interesting, since this way entrapped polyphenols can be consumed even by people who do not drink alcoholic beverages. Argentinean red wine dry extract, as well as red wine powder were successfully encapsulated by freezedrying with MD containing five times the concentration of anthocyanins than that in liquid wine and more than 30 polyphenols (Rocha-Parra et al., 2018; Sanchez et al., 2013). Food industry by-products were also used as a source of various polyphenols encapsulated by this technique. In that term, the number of interesting sources can be found in the literature, such as red onion peel (Elsebaie & Essa, 2018), beetroot ˇ ˇ pomace (Saponjac, Canadanovi´ c-Brunet, et al., 2016), or lime waste, which encapsulated together with hesperidin can also reduce the bitter taste of flavonoid glucosides (Afkhami, Goli, & Keramat, 2017). Oancea et al. (2017) showed that sour cherry anthocyanins encapsulated by this technique into β-lactoglobulin were protected from the gastric digestion, simulated in vitro.

12.3.3 Fluid bead coating This is a technique where core compound is suspended in air stream and then sprayed with matrix material in order to form microparticles. Size and shape of the

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Green Food Processing Techniques

particles are more uniform (de Souza Simo˜es et al., 2017) and wider range of materials can be used compared to the spray-drying (Ðorðevi´c et al., 2015). Potential problems are direct exposure to high temperature, which can cause bioactive material degradation, and possible agglomeration of particles (de Souza Simo˜es et al., 2017; Ðorðevi´c et al., 2015). As an example Oehme, Valotis, Krammer, Zimmermann, and Schreier (2011) successfully prepared shellac and shellac/hydroxypropyl methylcellulose
coated anthocyanin amidated pectin beads as dietary colonic delivery systems. Those were produced by ionotropic gelation and fluid bed Wurster coating with aqueous shellac solution. Similar to the abovementioned, spray-dried blueberry extract was coated with shellac using laboratory scale fluidized-bed coater with Wurster insert. Different pectins, as well as caffeine as copigment, were applied in order to influence the release of anthocyanins from the shellac coated granulates in simulated gastric fluid (Berg, Bretz, Hubbermann, & Schwarz, 2012).

12.3.4 Extrusion methods Extrusion process leads to the formation of droplets by extrusion of liquid mixture of core and matrix material. Simply, it is based on injection of one solution into another where gelation is initiated (de Souza Simo˜es et al., 2017). This technique is classified by used mechanisms to simple dripping, electrostatic extrusion, coaxial airflow, vibrating jet/nozzle, jet cutting, and spinning disk atomization (Ðorðevi´c et al., 2015; Pru¨ße, Jahnz, Wittlich, Breford, & Vorlop, 2002). Particles produced in this way have a hard, dense, and glassy structure which provides protection from unfavorable conditions and controlled release. Electrostatic extrusion is a good method for producing small particles, down to 50 μm (Nedovic et al., 2011). In many studies, the extrusion method is used to obtain polyphenol-loaded microparticles (Belˇscˇ ak-Cvitanovi´c et al., 2011; Belˇscˇ ak-Cvitanovi´c et al., 2015; Balanˇc, ´ c et al., 2016). Kaluˇsevi´c, et al., 2016; Belˇscˇ ak-Cvitanovi´c, Juri´c, et al., 2016; Cuji´ Chokeberry extract, a rich source of polyphenols, can be successfully incorporated in microparticles using electrostatic extrusion and encapsulates obtained on ´ c et al., 2016). Different mixtures this way can be a promising food additive (Cuji´ were investigated to find the best delivery systems for green tea polyphenols, also using electrostatic extrusion (Belˇscˇ ak-Cvitanovi´c, Juri´c, et al., 2016). Vibrationnozzle encapsulation provided longer stability of polyphenols extracted from wine production wastes (Aizpurua-Olaizola et al., 2016). Electrospinning, another variation of electrostatic extrusion technique, proved to be an effective method for encapsulation of sour cherry polyphenols (Isik, Altay, & Capanoglu, 2018). Coextrusion implies extrusion of two or more substances for microparticle formation, but the basic principle is the same. The study of Chew and Nyam (2016) demonstrated that kenaf seed oil can be successfully microencapsulated using coextrusion technology. They examined and suggested best processing conditions (such as different flow rates for shell and core feed, vibrational frequencies, drying methods, and shell formulations) and showed that microencapsulation is efficient, stable, and reproducible process.

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The interesting study of Wang, Waterhouse, and Sun-Waterhouse (2013) investigated encapsulation of canola oil fortified with quercetin (core solution) into alginate-pectin (shell solution) beads using coextrusion method. The obtained microparticles remained intact after treatment in low pH conditions. Also, the oxidation, hydrolytic rancidity, and total phenolic content were recorded under storage conditions. The quercetin-enriched canola oil was more effective than canola oil fortified with vitamin E or butylated hydroxytoluene in suppressing oil oxidation. The authors suggested this type of encapsulation as an excellent way of delivery of unsaturated oil and phenolic antioxidants, apart from nutritional value of pectin enriched matrix, which enable to consider it as a potential food additive. Coextrusion, as well as other microencapsulation techniques, is useful for probiotic culture (PC) protection. Shinde, Sun-Waterhouse, and Brooks (2013) examined coextrusion encapsulation of PC with or without apple skin polyphenol extract (ASPE). The addition of polyphenols resulted in significantly greater viability of PC cells in a model milk drink and protection of PC in low pH conditions. ASPE, which is an extract of fruit processing by-product, proved to be a useful and functional value-added ingredient.

12.3.5 Emulsification process This technique is also widely employed for food applications. It is very efficient, provides stable particles, and allows their controlled release (Lu, Kelly, & Miao, 2016). During emulsion formation, two basic systems may be applied—water/oil emulsions or oil/water emulsions, or more complex systems such as W/O/W double emulsions (Ðorðevi´c et al., 2015; Nedovic et al., 2011). Methods for emulsification processes are numerous, and some of them are phase separation and gelation of single biopolymer solutions; injection and gelation of single biopolymer solution; gelation of single biopolymer solutions within double emulsion; aggregative separation and gelation of mixed biopolymer solution; and segregative separation and gelation of mixed biopolymer solution (Ðorðevi´c et al., 2015). After emulsion formation, a gelling agent can be added in order to obtain microbeads (e.g., via electrostatic extrusion) (Kaluˇsevi´c et al., 2012). The sources of polyphenols encapsulated in this way are very diverse, ranging from bilberries, rich in anthocyanins (Mueller et al., 2018), cocoa (Lupo, Maestro, Porras, Gutie´rrez, & Gonza´lez, 2014), herbs like thyme (Trifkovi´c et al., 2014) or even dandelion (Belˇscˇ ak-Cvitanovi´c, Buˇsi´c, et al., 2016). Este´vez, Gu¨ell, LamoCastellvı´, and Ferrando (2018) produced stable W/O/W double emulsion for encapsulation of grape seed extract, a source of polyphenols widely encapsulated by a lot of techniques. This double emulsion method is also used for entrapment of hydrophilic catechin and hydrophobic curcumin simultaneously (Aditya et al., 2015). Furthermore, resveratrol efficiently improved the stability of α-tocopherol, as showed in two different studies (Feng, Yue, Ni, & Liang, 2018; Wang et al., 2016). Despite the number of examples of simultaneous encapsulations is emerging, coencapsulation is not always insofar effectual. For example, Gaudreau, Champagne, Remondetto, Gomaa, and Subirade (2016) concluded that GTE did not

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affect the encapsulation yield of Lactobacillus helveticus cells or helped its survival during simulated digestion.

12.3.6 Complex coacervation Mechanism that stands behind coacervation is a liquid
liquid phase separation. The coacervation can be divided to simple coacervation (1), which employs one kind of polymer, or complex coacervation (2), which is more frequently used and requires two or more polymers of opposite ionic charges (Zhang, Law, & Lian, 2010). Complex coacervation process has three main stages: forming of three immiscible phases, deposition of the coating and its solidification, which may be followed by addition of a cross-linker (Zhang et al., 2010). Palupi and Praptiningsih (2016) encapsulated coffee residue in oxidized tapioca starch that can serve as an alginate substitute. This promising coating had better properties compared to the alginate capsule. Souza et al. (2018) encapsulated proanthocyanidin-rich cinnamon extract, preserving its compounds responsible for valuable effect on health and hiding their unacceptable sensorial characteristics, all at once. Curcumin’s low solubility can be improved by coacervation, and then it can be properly used as a functional food ingredient (Shahgholian & Rajabzadeh, 2016).

12.3.7 Encapsulation in liposomes Liposomes are spherical vesicles consisting of one or more lipid bilayers. Beside their pharmaceutical use, entrapment of diverse core materials, regardless of their solubility has also found its applications in food sector (Ðorðevi´c et al., 2015). Lipid bilayers are formed between hydrophilic heads and lipophilic tails of phospholipids, which interact with water (Ðorðevi´c et al., 2015). The result is spherical organization—liposomes. Encapsulation methods based on liposomes are numerous (Balanˇc, Trifkovi´c, et al., 2016; Gibis, Ruedt, & Weiss, 2016; Isailovi´c et al., 2013; Silva et al., 2016; Silva-Weiss et al., 2018; Priprem et al., 2008; Toniazzo et al., 2017). The main conventional methods are thin-film hydration method, reversed-phase evaporation, solvent injection method, and heating-based method, while some of novel methods are membrane contactor-based method (a modified solvent injection method), freeze-drying of double emulsion method and proliposome method (Ðorðevi´c et al., 2015). Silva-Weiss et al. (2018) emphasized the relevance of liposomes in encapsulation of quercetin and rutin, while Isailovi´c et al. (2013) explored the use of resveratrol-loaded liposomes for existing food products quality improvement. Gibis et al. (2016) coated grape seed polyphenols with chitosan, which slowed down its release. This is important in food industry because it stops bioactive compounds to diffuse too fast into the medium.

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12.3.8 Molecular inclusion CDs are natural molecules with uncommon structure—simplified, they are hollow cyclic oligosaccharide capsules inside of which a “guest” molecule can be entrapped. CDs inclusion complexes are made thanks to coprecipitation principle, under particular conditions for every guest substance, and these complexes can be dried using spray- or freeze-drying (Ðorðevi´c et al., 2015). The main reason of unexploitation of this method is its price, as well as its small size that limits loading capacity of CDs (Nedovic et al., 2011). Davidov-Pardo and McClements (2014) gave plenty of examples for resveratrol encapsulation in CDs. Improvement of resveratrol properties can be obtained by supercritical antisolvent technology (Zhou, Wang, Guo, & Zhao, 2011) or development of eco-friendly process for extraction and encapsulation of resveratrol (Mantegna et al., 2012) and many others. Beside resveratrol, polyphenols from different sources can be entrapped within CDs, such as anthocyanins from blackberry (Fernandes et al., 2018) or saffron (Ahmad, Ashraf, Gani, & Gani, 2018). This technique can help overcoming of undesirable characteristics of some polyphenols, such as catechins sensitivity to pH and high relative humidity (Ho, Thoo, Young, & Siow, 2017) or protect antioxidative properties of tea non-EC polyphenols (Aree & Jongrungruangchok, 2018). Many other polyphenols are suitable for CDs, such as curcumin (Lo´pez-Tobar, Blanch, Castillo, & Sanchez-Cortes, 2012) or ferulic and gallic acid, coencapsulated together (Girtzi, Christophoridou, & Poussis, 2015).

12.4

Conclusion

Many studies indicate various benefits of polyphenols. However, they are not suitable for use in food processing in free form. They are unstable, easily degradable, sensitive to oxygen, light, moisture, heat, etc. This chapter gives an overview of the recent achievements in the area of polyphenol encapsulation. The first part is addressing the beneficial features of polyphenols, as well as the role of encapsulation and carrier materials in stabilization, protection, and targeting delivery. The second part summarizes techniques for polyphenol encapsulation and its important characteristics, advantages, limitations, and applications in food products. Encapsulation proved that it is possible to incorporate polyphenols without reducing their functional characteristics. At the same time, encapsulation of polyphenols improves their bioavailability, controlled release, biological activity, target delivery, and shelf life or helps to mask undesirable taste. Encapsulation technology offers a wide range of solutions in this respect—improvement of sensory characteristics, health aspects, and/or nutritional value of food. Topics such as coencapsulation, the synergistic effect of bioactive compounds, and enhancement of their delivery are likely to be the future trends in this area and both consumers and industry may profit from this emerging field of science.

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There are number of possibilities how to encapsulate polyphenols and where to incorporate them. However, the particular application of encapsulated polyphenols depends on many factors such as particle size and its distribution, the food matrix in which these are going to be incorporated, compatibility with foods, as well as the impact on rheological and textural properties of final products.

Acknowledgment This work was supported by the Ministry of Education, Science and Technological Development, Republic of Serbia (projects nos. III46010, 31069, and 173019).

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686. Zhu, X., Zhang, H., & Lo, R. (2004). Phenolic compounds from the leaf extract of artichoke (Cynara scolymus L.) and their antimicrobial activities. Journal of Agricultural and Food Chemistry, 52(24), 7272
7278.

Further reading Bora, A. F., Ma, S., Li, X., & Liu, L. (2018). Application of microencapsulation for the safe delivery of green tea polyphenols in food systems: Review and recent advances. Food Research International, 105, 241
249. Fang, Z., & Bhandari, B. (2010). Encapsulation of polyphenols—A review. Trends in Food Science & Technology, 21(10), 510
523. Kosaraju, S. L., D’Ath, L., & Lawrence, A. (2006). Preparation and characterisation of chitosan microspheres for antioxidant delivery. Carbohydrate Polymers, 64, 163
167. Tang, D. W., Yu, S. H., Ho, Y. C., Huang, B. Q., Tsai, G. J., Hsieh, H. Y., et al. (2013). Characterization of tea catechins-loaded nanoparticles prepared from chitosan and an edible polypeptide. Food Hydrocolloids, 30, 33
41.

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Chahrazed Boutekedjiret1, Amina Hellal1, Anne-Sylvie Fabiano-Tixier2, Maryline Abert-Vian2 and Farid Chemat2 1 Laboratory of Science and Technology of Environment, Ecole Nationale Polytechnique, Alger, Alge´rie, 2Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France

13.1

Extraction processes of essential oils: from tradition to innovation

13.1.1 Essential oils: definition, localization, and composition Essential oils (EOs), which must be isolated by physical means only, are defined as products obtained from raw plant materials. The physical methods used are distillation (steam, steam/water, and water), squeezing (also known as cold pressing for citrus peel oils), or dry distillation (also known as pyrolysis) of natural materials. The EO is physically separated from the water phase by distillation. The volatile compounds have the property to solubilize in fatty oils and fats so that they have been called “essential oils.” The term “oil” is used to denote the hydrophobic and viscous characteristic (not water soluble) while the term “essential” is used to denote the native essence and typical fragrance of the plant. EO’s volatility opposes them to fixed or vegetal oils, which are mainly lipids (Fernandez & Chemat, 2012). According to their uses, EOs can be treated later in order to partially or completely eliminate a component or a group of components. We obtain deterpenated, desesquiterpenated, rectified EOs or purified EOs of a particular compound. EOs are largely set out again in the vegetable kingdom. Some families’ are particularly rich; with car of example: Lamiales, Asterales, Rutales, Laurales, Magnoliales, etc. They can be stored in all the vegetable bodies: flowers, sheets, barks, wood, roots, rhizomes, fruits, and seeds. According to its location in the plant, the EO composition can vary. At the cellular level, EOs can be localized in insulated secreting cells, but they are generally in the secreting bodies, such as pockets, glands, channels, or hairs (Fig. 13.1). Observation of EO in the cuts of bodies of the plant is carried out using the lipophilic dyes as Sudan III, which colors the droplet oils in red. Chemical composition of EOs is complex and variable; it is a mixture of compounds, which can be classified into two groups: terpenes (monoterpenes, sesquiterpenes, and diterpenes) that constitute the hydrocarbon fraction and the oxygenated compounds (esters, aldehydes, ketones, alcohols, phenols, oxides, acids, and lactones). Nitrated or sulfur compounds can sometimes be present (Fig. 13.2). Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00013-6 © 2019 Elsevier Inc. All rights reserved.

Figure 13.1 Secreting cells of some plants. (A) transverse section of rosemary sheet observed under the photonic microscope (6.3 3 3.2), (B) secreting hair of rosemary sheet observed on longitudinal section under the electron microscope, (C) secreting gland of rosemary observed under the photonic microscope (100 3 3.2), (D) secreting gland and secreting hair of rosemary observed under the electron microscope, (E) lavender flower observed under the electron microscope, (F) secreting gland and secreting hair of lavender flower observed under the electron microscope, (G) secreting hair of thyme stem observed under photonic microscope ( 3 600), and (H) secreting gland of orange peel observed under the electron microscope.

Essential oils for preserving foods H

CH

3C

371

Monoterpenes

2

Lactone O

Limonene

O

δ-undecalactone

H3 C

H

CH

CH

3C

3

Phenols

2

Ketones

OH

Carvone

Eugenol

H2 C

O

O

CH3

CH

3

O

Furanone

Aldehydes

CH3

p-Anisaldehyde

CH3

O

OH

Mesifurane

O H3 C

O

CH3 O

O

CH3

Volatiles compounds

H3 C

HO

H3 C

SH H3 C

4-methoxy-2methyl-2-butanethiol

O

Alcohol C15 Esters

CH3

H3 C

CH3

Ethers

O

Methyl jasmonate

CH3

O O

O

CH3

Sesquiterpenes H3 C

Chamazulene

CH3 CH3

Lavandulol

CH2

Soufres

Coumarins O

CH3

H3 C

3-Butyl-phtalide

Coumarine

O

Alcohol

Phtalides

Oxide

H3 C

HO

CH3

H3 C

CH3

Viridiflorol

H3 C CH3

O O

Menthofuran

Oxyde de rose

CH3

Figure 13.2 Chemical composition of essential oils.

It is important to note that the chemical composition of an EO can be influenced by several factors: the existence of chemo-types, vegetative cycle, the incidence of the environmental factors, and the cultivation methods and the extraction processes. EOs are generally liquid at ambient temperature, volatile, with an aromatic odor, and can be colored. Their density is generally lower than that of the water from 0.850 to 0.950 except for EOs of cinnamon, clove, sassafras, and wintergreen. They have a high refraction index and, generally, are endowed to provide rotatory. EOs are soluble in alcohol (generally more used), in the majority of organic solvents (at the laboratory one prefers hexane), and in fixed oils or their derivatives (grease). They are far from water soluble, but they communicate their odor to him. EOs have an undeniable percutaneous penetration capacity (Bruneton, 1993). Considering chemical proprieties, they are neutral with the sunflower but acquire little by little an acid reaction. They oxidize easily by the light and are resinified by absorbing oxygen at the same time as their odor changes, their boiling point increases, and their solubility decreases. EOs absorb chlorine, bromine, and iodine with the release of heat and can combine with water to form hydrates.

13.1.2 Essential oils: recovery methods EOs can be obtained by distillation processes [steam distillation, and water or hydro-distillation (HD)] or by a mechanical process (cold pressing) (Fig. 13.3). Distillation processes are based on a codistillation of water and volatile organic compounds. In a heterogeneous system, such as this one, boiling occurs when the

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Condenser

Reactor + matrix

Essential oil Aqueous phase

Florentine flask Steam generator

Figure 13.3 Extraction of essential oils by distillation and cold pressing.

sum of the vapor tensions of the compounds present reaches the atmospheric pressure. The vapor tension of the considered organic molecules being low, codistillation is done at a temperature close to 100 C (Naves, 1974). Steam distillation consists of subjecting the vegetable material to the action of a current of vapor without preliminary maceration. The organic volatile principles, which are not very water soluble, are carried by the steam and after condensation separated from the distillate by decantation. Two methods can be used: the water/ steam method, where the plant material must be carefully distributed on the grill above the hot water placed inside the distillation tank. The steam is produced by this water. In the second case, steam is produced by an outside source and directed into the distillation tank. This is a “direct” steam distillation that is the most common method for EO’s extraction. These processes are generally used to treat the sensitive vegetable matters that could not support a prolonged boiling. For HD, the vegetable material is immersed in water carried to boiling. The resulting steam from boiling water carries the volatile compounds with it. EO is collected after condensation and decantation of a distillate as for the steam distillation. HD is generally led to atmospheric pressure. However, to improve the ratio of the drive (mass of the involved compound/evaporated water mass), in other words the energy effectiveness, the operation can be made under pressure. Some raw materials, such as the rhizomes of vetiver, are treated thus because their components cannot be pulled by the vapor under atmospheric pressure because of their molecular mass. However, this technique cannot be used for fragile products which would be denatured at a temperature higher than 100 C. For this reason, founded overpressure is limited to a maximum value of 1.5 bar to the top of the atmospheric pressure. Cold pressing is the only process of treatment of the aromatic plants not implementing a fluid in the phase of extraction. It consists of either separately expressing the pericarps under a water current or to crush the whole fruits between metal cylinders. The essence, from low density, also called EO, is then separated from the aqueous phase (water of drive or fruit juice) by centrifugation. This process answers the double characteristic of EOs of hesperides. On the one hand, those are mainly

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made up of peroxydables and polymerizable terpenic hydrocarbons, therefore sensitive to the temperatures of HD. In addition, they are localized in an easily destroyed porous pericarp. So they are recovered by simple mechanical action. In a more general way, the choice of a technique of the aromatic plants exploitation must be adapted to a compound specifically required. In theory, it does not depend on the type of body used: leaf, flower, wood, seed or fruit, root, or rhizome, at the dry state or the fresh state. Those can be treated by steam distillation or HD. The option depends on the type of desired product or the chemical nature of the target odorous molecules.

13.1.3 Devices of essential oils extraction At a laboratory or an industrial scale (Fig. 13.4), the device used for the extraction of EOs consists of four elements: a heat source to heat water or to produce vapor, a reactor to contain the vegetable matter, a condenser to condense the (EO
steam water) mixture, and a Florentine flask to recover the distillate. Laboratory scale devices used for the extraction of EOs by steam distillation or HD are generally out of glass and are simple to use. The capacity of the reactor can vary from 500 mL to 3 L (Fernandez, Andre´, & Casale, 2014). The extraction of EOs at industrial scale is done in an alembic made up of several parts: a steam or hot water generator, the body of the alembic where the plant and water are charged in the HD case, or the plant alone in the case of the steam distillation, the capital and the swan neck which surmount the body of the alembic, the condenser in the form of serpentine or pipe cooler, the essencier or Florentine flask to separate EO from water distillation. According to cases, the alembic can be fixed or mobile. Its loading can be done by total opening of the capital, or inspection pit at the top, whereas the unloading

Figure 13.4 Laboratory and industrial conventional recovery of EOs. EO, Essential oil. Source: With permission from www.tournaire.com.

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by total opening and hoist, by swing of the body of the alembic, by side inspection pit, or by drainage sluice to the bottom of the alembic. The heating is assured by a naked fire under the alembic or by immersed electric resistance, or by a steam generator. Steam can be introduced directly into the alembic or in a double content. In the cases of the crushed plants, a system of agitation is necessary to avoid their filling. Generally, after separation of the EO from distillation water, this one is recycled in the body of the alembic; it is a cohobating.

13.1.4 Innovative techniques Effectiveness and selectivity became the principal characteristics of an ideal extraction, new technologies, such as microwave-assisted extraction, extraction by supercritical fluid, controlled instantaneous detente, and pulsed electric fields, developed in the field of the extraction of EOs (Fig. 13.5). Compared to the traditional processes, these new techniques make it possible to reduce the durations of treatment as well as the rejections, to consume less energy, and to obtain extracts of a better quality. However, these techniques are not recognized from a lawful point of view because they do not meet the standard defining an EO. Also, the products obtained by these techniques are called aromatic extracts (Fernandez & Chemat, 2012).

Figure 13.5 Turbo-distillation and Microwave extraction. Source: With permission from (left) www.etsreus.com and (right) www.milestonesrl.com.

Essential oils for preserving foods

13.2

375

Essential oils as antimicrobials

In the last few decades, a lot of works have been aimed at the detection, production, and characterization of EOs, as well as to their use in various fields. In the word, interest in the use of more naturally occurring compounds has been generated by the negative public opinion of industrially synthesized food antimicrobials. Hence, publications dealing with the application of EOs as natural antimicrobials to the protection of foods begun to be available in the literature (Bevilacqua, Corbo, & Sinigaglia, 2010; Bukvicki et al., 2004; Gyawali & Ibrahim, 2014; Hyldgaard, Mygind, & Meyer, 2012; Mahian & Sani, 2016; Pandey, Kumar, Singh, Tripathi, & Bajpai, 2017; Prakash, Media, Mishra, & Dubey, 2015; Preedy, 2016; Tiwari et al., 2009; Vergis, Gokulakrishnan, Agarwal, & Kumar, 2015). These biopreservatives can be used in several foodstuffs as alternatives to traditional chemical food additives to improve their microbial stability. Traditionally, the antimicrobial effects of different species of herbs and spices are known and used to increase the shelf-life of foods. Thus the EOs and their components, currently used as food flavorings, could serve as food preservatives due to their antimicrobial activity, particularly since they are mostly classified as Generally Recognized As Safe by the U.S. Code of Federal Regulations (U.S. Code of Federal Regulations, 2016). Also, their use in very small quantities is possible due to their high efficiency. EOs are the aromatic and volatile products of plant’s secondary metabolism well known for their antimicrobial effects against a wide variety of microorganisms. The antimicrobial activities of EOs are directly correlated to the presence of their bioactive volatile components (Bukvicki et al., 2004). Worldwide, as food industry presents a growing demand for natural food preservatives and innovation in food packaging, EOs and their components have been applied in many foods (meat, bread, vegetables, lactic products, etc.) against the foodborne pathogen microorganisms. Until now, numerous recent review articles focused on the efficiency of EOs in the fight against bacterial pathogens encountered in food products (Calo, Crandall, O’Bryan, & Ricke, 2015; Mendonca, Jackson-Davis, Moutiq, & Thomas-Popo, 2018; Pandey et al, 2017; Preedy, 2016; Magdalena, Pop, GEOrgescu, Turcu¸s, & Mathe, 2018). Nevertheless, very few preservation applications based on EO utilization are implemented until now by the food industry.

13.2.1 Applications in meat-based foodstuffs and seafood products Meat products are an excellent culture medium for food spoilage and pathogenic bacteria proliferation because of their neutral pH, water activity, and rich nutrientspecific composition. Nowadays, the meat product industry uses chemical additives in several meat processes to prevent the growth of foodborne pathogens and to extend the shelf-life

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of refrigerated storage. Particular interest has been shown on the potential use of plant-based EOs as safer additives for meat preservation. Hence, some spices and herbs (such as thyme, oregano, rosemary, and marjoram) have been used in meats as aromatic agents (Speranza & Corbo, 2010). For EOs in meat and meat product applications, eugenol and coriander, clove, oregano, and thyme oils were found to be very effective in inhibiting autochthonous spoilage flora and pathogens in meat products (Speranza & Corbo, 2010). Previously, Lemay et al. (2002) have studied the antimicrobial effect of natural preservatives in chicken meat and reported that with the use of mustard’s EO, aerobic mesophilic bacteria and lactic acid bacteria were significantly lower than the control after 2 days of storage. Chouliara, Karatapanis, Savvaidis, and Kontominas (2007) considered the combined effect of oregano EO (known for its richness in thymol and carvacrol) and modified atmosphere packaging for the prolongation of the shelf-life of fresh chicken meat, stored at 4 C. A reduction of pseudomonads, lactic acid bacteria, Enterobacteriaceae and Brochothrix thermosphacta, and yeasts population growth was improved. A very low degree of lipid oxidation was observed. But, sensory analyses pointed out that 1% oregano oil imparted a very strong taste to the product, whereas samples containing 0.1% oregano oil gave a characteristic desirable odor and taste to chicken meat, very compatible to cooked chicken flavor. Interesting studies of Oussalah, Caillet, and Lacroix (2006) showed that the incorporation of oregano EO in the minced beef has helped to maintain the microbiological quality and reducing the oxidation of fat beyond its duration normal storage. To enhance the effectiveness of EO, Oussalah, Caillet, Salmie´ri, Saucier, and Lacroix (2004) have stabilized the EOs in edible polymers (biofilm, coating, capsule, emulsion), which allows their distribution to the food during storage. The application of biofilms containing EOs on slices of meat reduced significantly the growth of pathogenic bacteria beyond a week of storage. Otherwise, the effects of Satureja horvatii EOs in a ground pork product investigated by Bukvicki et al. (2014) showed significant inhibition of Listeria monocytogenes inoculated into the meat. Da Silveira et al. (2014) evaluated the antimicrobial activity of bay leaf EO in fresh Tuscan sausage stored at 7 C for 14 days. The EO was able to reduce the population of total coliforms by nearly 3 log CFU/g and to extend the product shelf-life for 2 days. But, although the presence of the EO affected the sensory characteristics of the sausage, it was considered acceptable by consumers and was proposed in fresh Tuscan sausage to improve its safety and shelf-life. The efficacy of EOs against the foodborne pathogens bacteria would be directly related to interactions with food components. Indeed, Singh, Singh, Bhunia, and Singh (2004) reported that thyme oil reduced significantly bacterial population of L. monocytogenes in low-fat hotdogs but not in full-fat hotdogs. More recently, as reported by Speranza and Corbo (2010), the effect of oregano oil toward Photobacterium phosphoreum was stronger on cod filets than on salmon (a fatty fish). A high-fat content appears to markedly reduce the action of EOs in meat and fish products.

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13.2.2 Applications in dairy products Until now, several recent review articles focused on the application of EOs in lactic acid products. Bayoumi (1992) had studied the bacteriostatic effect of some spices and their utilization on the activity of the yogurt bacteria starter. However, a reaction between carvacrol and proteins is a limiting factor in the antibacterial activity against Bacillus cereus in milk (Pol, Mastwijk, Slump, Popa, & Smid, 2001), as well as in diluted low-fat cheese, when clove oil is used as an antimicrobial against Salmonella enteritidis (Smith-Palmer, Stewart, & Fyfe, 2001). The recent review of Khorshidian, Yousefi, Khanniri, and Mortazavian (2018) represents an overview of the impact of EOs and their constituents as natural antimicrobials versus common pathogenic and spoilage microorganisms in cheese. This review introduces the potential application of EOs as natural antimicrobial agents for reduction of common spoilage and pathogenic bacteria as well as molds and yeasts in cheese-making industry. Applications of various EOs in different types of cheese have been well described in this review. For example, in a study by Govaris, Botsoglou, Sergelidis, and Chatzopoulou (2011), antibacterial effects of oregano and thyme EOs against L. monocytogenes and Escherichia coli O157:H7 in feta cheese stored under modified atmosphere packaging (50% CO2 and 50% N2) at 4 C were determined. The results revealed that the growth of bacteria was restricted by the EOs with a greater inhibitory effect toward L. monocytogenes. Olmedo, Nepote, and Grosso (2013) evaluated the effect of oregano and rosemary EOs on the oxidative and fermentative stabilities of flavored cheese prepared with cream cheese base and demonstrated a protective effect against lipid oxidation and fermentation in flavored cheese prepared with cream cheese base. Another approach on yogurt added with oat flakes, sesame seeds, linseeds, honey, and EO of basil (Ocimum basilicum L.) showed that the combination of these additives did not affect adversely on the speed of the fermentation process of the lactic acid bacteria and the obtained product got appreciated organoleptic properties (Kostova et al., 2016).

13.2.3 Applications in vegetables and fruits Contrary to meats, vegetables generally have a low-fat content, which may contribute to the successful applications obtained with EOs (Bukvicki et al., 2004). Furthermore, a decrease in storage temperature and pH enhances the antimicrobial activity of EOs (Smith-Palmer et al., 2001). All EOs and their components that have been tested on vegetables appear effective against the natural spoilage flora and foodborne pathogens. Roller and Seedhar (2002) showed that the treatment with 1 mM of carvacrol or cinnamic acid delays spoilage of fresh-cut kiwifruit and melon at freezing temperatures without adverse sensory consequences. Lemongrass and geraniol have been found effective against E. coli, Salmonella sp., and Listeria spp. in apple, pear, and melon juices (Raybaudi-Massilia, Mosqueda-Melgar, & Martin-Belloso, 2006).

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Previously, 17 plant EOs and 9 oil compounds evaluated for antibacterial activity against the foodborne pathogens E. coli O157:H7 and Salmonella enterica in apple juices. The most active compounds were carvacrol, oregano oil, geraniol, lemon oil, citral, lemongrass oil, and cinnamon. The activity was greater for S. enterica than for E. coli, increased with incubation temperature and storage time, and was not affected by the acidity of the juices. Others evaluated the antifungal activity of EOs of thyme, summer savory, and clove in tomato paste throughout 2 months against Aspergillus flavus. The antifungal activity of the EOs could inhibit the growth of the mold with a stronger inhibition of the thyme oil and summer savory, taste panel evaluation carried out in a tomato ketchup base, was accepted by panelists.

13.2.4 Applications to cereal products EOs have the potential to be used as a food preservative for cereals. Cereals can be infected by a number of fungal pathogens. Hence, EOs from five species of medicinal and food plants were tested, against five important pathogenic fungal species that cause stem, leaf, and ear diseases of cereals. The EOs were extracted from Pimpinella anisum, Thymus vulgaris, Pelargonium odoratissimum, Rosmarinus officinalis, and Foeniculum vulgare and applied on the fungi Oculimacula yallundae, Microdochium nivale, Zymoseptoria tritici, Pyrenophora teres, and Fusarium culmorum. All EOs used affected the growth of these fungi, the best antifungal activity was revealed by T. vulgaris. As the widespread use of pesticides has resulted in the development of pest resistance, toxicity, and hazardous effects on the human health and the environment, the use of botanical pesticides appears to be an acceptable alternative. So, EOs from plants could provide natural alternatives to chemical fungicides to preserve cereals.

13.3

Essential oils as antioxidant agents in food products

Nowadays, with the growing internationalization of the food industry, everyone can consume all kinds of food everywhere in the world. It is resulting in an increasing concern about health and safety risks in the global food supply chain. One of the problems derived from food degradation is lipid oxidation. Foods which contain fat and oils will spoil once exposed to oxygen from the air due to oxidation reactions. This chemical change results in a bad odor, taste, and texture. A common strategy to inhibit lipid autoxidation is to supplement food products with efficient exogenous antioxidants. For instance, butylated hydroxyanisole (BHA) and butyl hydroxytoluene (BHT) are among the most powerful synthetic antioxidants and were used in foods to limit oxidation processes and prevent offflavors. However, these synthetic antioxidants are suspected to have mutagenic, carcinogenic, and teratogenic effects during a long-term use (Chave´ron, 1999). The

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substitution of synthetic antioxidants for natural additives has encouraged several studies toward the utilization of natural products such as EOs (Ribeiro-Santos, Andrade, Sanches-Silva, & Ramos de Melo, 2018).

13.3.1 Chemical lipid oxidation Degradation is generally undesirable since it can change the organoleptic, nutritional, or functional characteristics of foods and cosmetics. There are numerous factors influencing or initiating lipid oxidation, which are classified with intrinsic [e.g., unsaturation of lipid fatty acids (number and position), the presence of prooxidants (metal ions, enzymes, etc.), and natural antioxidants] and external factors (e.g., temperature, light, partial pressure of oxygen, water activity, and conditions of storage and processing). Autooxidation is a free radical chain reaction with three main stages (initiation, propagation, and termination) (Frankel, 1980). In the initiation step, hydrogen is removed from an unsaturated fatty acid in a lipid molecule, resulting in the formation of a lipid alkyl radical (R ) in the presence of an initiator. This slow reaction is promoted with an increasing temperature, metallic traces, oxygen, humidity, or irradiation. In the propagation step, lipid alkyl radicals react with oxygen to form peroxyl radicals (ROO ), which are more reactive than the initially formed alkyl radicals. This peroxyl radical (ROO ) has sufficient energy to promote the abstraction of hydrogen from another unsaturated fatty acid, thus forming another alkyl radical and a lipid hydroperoxide (ROOH). All free radicals produced in this propagation stage combine each other to form stable nonradical species (ROOR, RR, O2) in the termination stage. G

G

G

13.3.2 Antioxidant activity Antioxidants are substances that can efficiently protect a given target against oxidation while being used at a very low antioxidant/target molar ratio, say lower than 1%. In foods, the most important targets are polyunsaturated lipids (RH). Traditionally, antioxidants are classified into two main groups (Fig. 13.6) depending on how they act to remove reactive oxygen species, ROS, a collective name for peroxyl radicals, hydroxyl radicals, singlet oxygen, superoxide, and hydroperoxides. Preventive antioxidants interfere with the initiation stage by retarding the initial formation of ROS. They act by reducing hydroperoxides to molecular species without the formation of free radicals. Examples of such are metal complexing agents (iron, copper), such as phytic acid, which prevents them from participating in reactive radical production. In biological systems, enzymatic antioxidants, such as superoxide dismutases, catalases, and glutathione peroxidases, have an important role as preventive antioxidants (Valgimigli & Pratt, 2012). However, if the autooxidation process has started, preventive antioxidants are ineffective, thus chainbreaking antioxidants are more suitable. Chain-breaking antioxidants inhibit autooxidation by reacting with peroxyl radicals more rapidly than the oxidizable substrate in order to block the propagation

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Temperature UV metals

Preventive antioxydant

Initiation

H

OO•

Propagation •

R

R

R O2

Unsaturated fatty acid

Lipid radical (R•)

Chain-breaking Lipid peroxyl radical (ROO•) antioxydant H+

OOH

H

+

R

R

Terminaison Lipid peroxide (ROOH)

Figure 13.6 Simplified mechanism of lipid autoxidation and antioxidant protection.

stage. A common example is α-tocopherol (vitamin E). It transfers its phenolic H-atom to ROO (Huang, Hopia, Schwartz, Frankel, & German, 1996) and is simultaneously converted into a resonance-stabilized radical, which unlike ROO is unable to react with a second RH molecule to propagate the chain. Antioxidant activity is governed by several parameters, such as the reducing activity of the antioxidant (ability to quickly deliver H-atoms and/or electrons), its location in biphasic water
lipid systems (roughly predicted from the hydrophilic
lipophilic balance), and its metal-binding capacity. Consequently, antioxidant tests may give highly contrasted results depending on whether they involve monophasic or biphasic systems and make use of metal ions or organic species (e.g., diazo compounds) for a radical generation (Frankel, Huang, Kanner, & German, 1994). Hence, the results of a single assay can give only a reductive view of the antioxidant properties of EOs and must be interpreted with caution. Moreover, EOs are complex mixtures of compounds with different reducing capacity, which makes data interpretation even more complicated and offers more opportunities for scattered results depending on the antioxidant tests selected. Two main approaches can be applied to determine in vitro antioxidant activities: G

G

G

The inhibition of lipid autoxidation in different systems (oil, solutions of lipids in organic solvents, oil-in-water emulsions, micelles, liposomes, lipoproteins, etc.). These methods are aimed at modeling oxidation processes in foods or living systems. Thus they are close to real situations and, being generally based on biphasic systems, offer the opportunity to test both hydrophilic and lipophilic antioxidants. Their main drawbacks are timeconsuming experimental procedures and complexity in data interpretation. Indeed, lipid autoxidation is typically slow and yields a complex distribution of products beyond the primarily formed lipid hydroperoxides, that is, lipid alcohols and carbonyl compounds, cleavage products, volatile compounds, etc. Measurable and reproducible autooxidation rates are more readily achieved when large concentrations of initiator (diazo compounds, metal ions) are used. Overall, the data may depend on the type of initiator used, the lipid autoxidation products monitored, and the analytical technique selected.

Essential oils for preserving foods

G

381

The ability of antioxidants to scavenge-free radicals species that can be easily generated or are eventually stable enough to be commercially available and handled as common chemicals. Although these methods do not bear clear biological significance and must be interpreted with caution, they are typically much simpler and much easier to implement than methods based on lipid autooxidation. They can offer first efficient approaches for screening a large number of samples and are widely popular in the agro-food industry.

A summary of the methods that can be used to evaluate the antioxidant activity of EOs is presented in Table 13.1.

13.3.3 Inhibition of lipid autooxidation The protective action of EO has been evaluated in two model systems by measuring the formation of primary [conjugated dienes (CDs)] and secondary [thiobarbituric acid reactive species (TBARS)] lipid autooxidation products (Ruberto & Baratta, 2000).

13.3.3.1 Conjugated diene method The method deals with the first step of lipid autooxidation, that is, the dioxygenation of polyunsaturated lipids membrane (LH) that is accompanied by a conjugation of two carbon
carbon double bonds (CDs). The main CDs are the lipid hydroperoxides (ROOH) formed as a mixture of regioisomers, diastereoisomers, and enantiomers. CDs can be spectrophotometrically quantified by detection in the range of 230
240 nm (Lingnert, Vallentin, & Eriksson, 1979). Using this assay, Mau et al. (2003) showed a moderate antioxidant activity of Curcuma zedoaria R. EO (56.7%
70.3%), at 10
20 mg/mL in linoleic acid emulsions, using BHA (98.5%), ascorbic acid (84.7%), and α-tocopherol (92.7%) as reference antioxidants.

13.3.3.2 Thiobarbituric acid reactive species method The method consists of monitoring aldehydes produced by lipid hydroperoxide (LOOH) cleavage. Among these advanced lipid autoxidation products responsible for undesirable off-flavors, malondialdehyde (MDA) is especially toxic due to its strong electrophilic character. MDA reacts with thiobarbituric acid (TBA) to give a pink adduct detected by UV
vis spectroscopy at 532 nm (Ohkawa, Ohishi, & Yagi, 1979). A TBARS method involving egg yolk homogenates or rat liver homogenate as Polyunsaturated fatty acids (PUFA)-rich media has been used to test the antioxidant capacity of EOs (solubilized in methanol) with or without lipid autooxidation inducer (diazo compounds, such as 2,2’-Azobis(2-amidinopropane) dihydrochloride (AAPH), Fe31/ascorbate, Cu21). Thus it was shown that Salvia multicaulis and Salvia crypthanta EOs had greater antioxidant activity than BHT (Tepe et al., 2004). Miguel et al. (2004) compared the antioxidant properties of different concentrations of Thymus caespititius, Thymus camphoratus, and Thymus mastichina EOs, with and without AAPH. In the absence of AAPH, EOs, mainly from T. caespititius

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Table 13.1 Antioxidant activities of essential oils in comparison with common references. Essential oils (compared to references)

In vitro tests of antioxidant activity

References

Achillea millefolium (curcumin, BHT) Anthemis nobilis Cananga odorata (Trolox, Thymus vulgaris, BHA)

DPPH, IC50 (1.56; 7.92; 19.3) HRS (2.70; 14.3; 32) ABTS (0.81) DPPH, in % (66; 28; 75; n.t.) CL (31.7; n.t.; 342; n.t.) BCB (75; n.t.; 92; 87) ABTS (1.66) ABTS (,0.1) ABTS (,0.1) ABTS (2.12 3 103)

Candan et al. (2003)

ABTS (0.16) ABTS (,0.1) ABTS (,0.1) ABTS (3.16 3 102) DPPH, in % (20; 28; 75; n.t.) CL (0.79; n.t.; 342; n.t.) BCB (58; n.t.; 92; 87) DPPH, in % (63; 28; 75; n.t.) CL (28.1; n.t.; 342; n.t.) BCB (72; n.t.; 92; 87) DPPH, in % (96.8; 97; 96.4; 91) RA (0.97; 1.2; 1.2; 1.2) CD (70; 98.6; 92.7; 84.7) TBARS 2 i (73; 95; 95; 73) DPPH, in % (60; 28; 75; n.t.) CL (23.3; n.t.; 342; n.t.) BCB (49; n.t.; 92; 87) ABTS (0.26) DPPH, in % (13; 28; 75; n.t.) CL (0.5; n.t.; 342; n.t.) BCB (57; n.t.; 92; 87) ABTS (0.86) ABTS (,0.1) ABTS (1.14) ABTS (,0.1) DPPH, IC50 (5.62; 18; 3.8) BCB (70.5; 96.6; 94.5) ABTS (,0.1) DPPH, IC50 (8.49; 18; 3.8) BCB (59.5; 96.6; 94.5) DPPH, in % (18; 28; 75; n.t.) CL (0.85; n.t.; 342; n.t.) BCB (21; n.t.; 92; 87)

Mantle et al. (1998) Mantle et al. (1998) Mantle et al. (1998) Mantle et al. (1998) Sacchetti et al. (2005)

C. odorata Cedrus atlantica Cinnamomum camphora Cinnamomum verum J.S. PRESL. Citrus aurantium (L.) Osbeck Citrus limonum Citrus medica (L.) Burm. Commiphora molmol Cupressus sempervirens (Trolox, T. vulgaris, BHA) Curcuma longa L. (Trolox, T. vulgaris, BHA) Curcuma zedoaria (Christm.) Rosc. (BHA, α-tocopherol, ascorbic acid)

Cymbopogon citratus (DC) Stapf. (Trolox, T. vulgaris, BHA) Cymbopogon nardus Eucalyptus globulus (Trolox, T. vulgaris, BHA) Hyssopus officinalis L. Lavandula vera Melissa officinalis L. Pelargonium roseum Pimpinella anisum (BHT, ascorbic acid) Pimpinella anisum L. Pimpinella flabellifolia (BHT, ascorbic acid) Pinus radiata (Trolox, T. vulgaris, BHA)

Mantle et al. (1998) Sacchetti et al. (2005)

Mantle et al. (1998) Mantle et al. (1998) Mantle et al. (1998) Mantle et al. (1998)

Sacchetti et al. (2005)

Mau et al. (2003)

Sacchetti et al. (2005)

Mantle et al. (1998) Sacchetti et al. (2005)

Mantle et al. (1998) Mantle et al. (1998) Mantle et al. (1998) Mantle et al. (1998) Tepe et al. (2006) Mantle et al. (1998) Tepe et al. (2006) Sacchetti et al. (2005)

(Continued)

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Table 13.1 (Continued) Essential oils (compared to references)

In vitro tests of antioxidant activity

References

Piper crassinervium (Trolox, T. vulgaris, BHA)

DPPH, in % (43; 28; 75; n.t.) CL (10.2; n.t.; 342; n.t.) BCB (53; n.t.; 92; 87) DPPH, in % (23; 28; 75; n.t.) CL (0.84; n.t.; 342; n.t.) BCB (13; n.t.; 92;87) DPPH, in % (64; 28; 75; n.t.) CL (66; n.t.; 342; n.t.) BCB (82; n.t.; 92; 87) ABTS (0.16) DPPH, IC50 (3.9; 19.8) HRS (1.9; 32) DPPH, IC50 (2.4; 19.8) HRS (1.6; 32) DPPH, IC50 (13.13; 110.7; 86.6; 11.6) SRS (0.161; 0.08; 2.35; 0.006) TBARS 2 i (76.6; 74.2; 65.6; 87.7) TBARS 1 i (42; 82.1; 82.8; 69.4) TBARS 2 i (51.6; 74.2; 65.6; 87.7) TBARS 1 i (37.4; 82.1; 82.8; 69.4) DPPH, in % (22; 28; 75; n.t.) CL (1.54; n.t.; 342; n.t.) BCB (49; n.t.; 92; 87) TBARS 2 i (38.9; 74.2; 65.6; 87.7) TBARS 1 i (16; 82.1; 82.8; 69.4) ABTS (33.5) ABTS (0.78) DPPH, in % (55; 28; 75; n.t.) CL (0.94; n.t.; 342; n.t.) BCB (66; n.t.; 92; 87)

Sacchetti et al. (2005)

Psidium guajava (Trolox, T. vulgaris, BHA) Rosmarinus officinalis L. (Trolox, T. vulgaris, BHA) R. officinalis L. Salvia cryptantha (BHT) Salvia multicaulis (BHT) Teucrium marum (ascorbic acid, BHT, Thymol)

Thymus caespititius (α-tocopherol, BHA, BHT)

Thymus camphoratus (α-tocopherol, BHA, BHT)

Thymus citriodora (Trolox, T. vulgaris, BHA) Thymus mastichina (α-tocopherol, BHA, BHT)

T. vulgaris L. Verbena officinalis Zingiber officinale L. (Trolox, T. vulgaris, BHA)

Sacchetti et al. (2005)

Sacchetti et al. (2005)

Mantle et al. (1998) Tepe et al. (2004) Tepe et al. (2004) Ricci et al. (2005)

Miguel et al. (2004)

Miguel et al. (2004)

Sacchetti et al. (2005)

Miguel et al. (2004)

Mantle et al. (1998) Mantle et al. (1998) Sacchetti et al. (2005)

2,2-diphenyl-1-picrylhydrazyl (DPPH) is DPPH test; scavenging activity expressed either as a percentage of DPPH reduced or as IC50 value (EO concentration for 50% inhibition, in μg/mL). ABTS is ABTS test; scavenging activity reported as trolox equivalent (mmol/L). SRS is superoxide radical scavenging; expressed as IC50 value (in μg/mL). HRS is hydroxyl radical scavenging; expressed as IC50 value for deoxyribose degradation. RA is reducing activity. Cl is chemiluminescence (luminol), in trolox equivalent (mmol/L). CD is conjugated diene method; antioxidant activity expressed as a percentage of inhibition of lipid peroxidation (control without added antioxidant 5 0%). TBARS is TBARS method carried out without inducer (TBARS 2 i) or with inducer (TBARS 1 i); lipids 5 egg yolk or rat liver homogenates. Values are the percentage of antioxidant index (AI%). BCB is β-carotene bleaching test; antioxidant activity expressed as inhibition percentage after a 60 min incubation. BHA, Butylated hydroxyanisole; BHT, butyl hydroxytoluene; n.a., not active; n.t., not tested; TBARS, thiobarbituric acid reactive species.

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at 250 and 500 mg/L, demonstrated antioxidant capacities close to α-tocopherol and BHA. However, in the presence of AAPH, EOs (except T. camphoratus EO) were less efficient.

13.3.3.3 β-Carotene bleaching test In the inhibition of lipid peroxidation, antioxidants compete with polyunsaturated lipids for the lipid peroxyl radicals (ROO ) and/or the oxidizing species involved in the initiation step. In this test, the pigment β-carotene is added as a reference antioxidant, whose oxidative degradation can be selectively monitored by UV
vis spectroscopy at 470 nm. This provides a second opportunity (in addition to monitoring the lipid oxidation products) to assess the activity of a given antioxidant, which is expected to compete with both the lipid and β-carotene, thereby inhibiting both lipid peroxidation and β-carotene bleaching (Taga, Miller, & Pratt, 1984). The antioxidant activity is expressed as the percentage of β-carotene spared for a given antioxidant concentration (inhibition percentage or IP). Sacchetti et al. (2005) reported the antioxidant activity of 11 EOs in comparison with T. vulgaris L. EO (a reference antioxidant). The results of the β-carotene blenching assay showed that Cananga odorata (75.5% inhibition), R. officinalis L. (81.1% inhibition), and Curcuma longa L. (72.4% inhibition) were almost as efficient as T. vulgaris L. (90.9%) and BHA (86.7%). Piper crassinervium, along with Eucalyptus globulus, Cymbopogon citratus (DC) Stapf., and Cupressus sempervirens, displayed more moderate activities with IP values ranging from 65% to 48%. G

13.3.4 Radical-scavenging tests These methods are based on the ability of EOs to scavenge-free radicals, such as the superoxide radical anion (O2 2 ), the hydroxyl radical (HO ), and the stable colored radicals ABTS 1, DDPH . G

G

G

13.3.4.1 ABTS test In this method, the decay of the stable radical-cation ABTS 1 (strong visible absorption in the range of 600
750 nm) is monitored after addition of a given antioxidant. ABTS 1 rapidly reacts with electron donors, such as phenols and carotenoids, and is simultaneously converted into the colorless reduced form ABTS. The concentration of ABTS 1 reduced is expressed in terms of mM Trolox equivalent, the water-soluble analog of α-tocopherol (in other words, the ABTS 1 concentration reduced by Trolox is arbitrarily set at 1 mM). The radical-cation ABTS 1 was produced via oxidation of ABTS by metmyoglobin (heme-FeIII)
H2O2. According to Mantle et al. (1998), only three EOs showed high ABTS 1-scavenging activities, that is, cinnamon (2.1 M), pimento (316 mM), and bay (252 mM) EOs, whereas thymus and rosemary EOs, which typically rank among the most antioxidant EOs, were much less active. These surprising results raise the possibility of underlying G

G

G

G

G

G

Essential oils for preserving foods

385

practical problems due to the low solubility of EOs in the ABTS 1 aqueous solutions used in this test. G

13.3.4.2 DPPH test This assay is considered as a simple and accurate method for the first assessment of antioxidant properties of EOs. The DPPH test is based on the ability of the stablefree radical 2,2-diphenyl-1-picrylhydrazyl to abstract H-atoms from antioxidants. As DPPH shows a very intense absorption in the visible region (λmax 5 515 nm in MeOH), its simultaneous conversion into the colorless hydrazine (DPPH-H) can be easily monitored by UV
vis spectroscopy. Typically, an aliquot of EO is solubilized in a neutral buffered solution containing the detergent Tween 20 and the DPPH solution in ethanol is added. In their investigation of the DPPH-scavenging activity of 11 EOs, Sacchetti et al. (2005) showed that C. odorata, C. citratus, R. officinalis L., C. longa L. EOs notably reduced the DPPH concentration with efficiencies in the range of 60%
64%, that is, only slightly lower than that of the reference EO T. vulgaris L. (75.6%) and ca. twice as high as that of Trolox (28.2%). Similarly, Choi, Song, Ukeda, and Sawamura (2000) reported a DPPH-scavenging study for 34 kinds of citrus EOs. All EOs revealed scavenging effects in the range of 17.7%
64% compared to Trolox (23.2%). In the series, the DPPH-scavenging activities of EOs from ozu, daidai, and Valencia orange were low (17.7%
19.1%), whereas those of the other citrus EOs (21.6%
64%) were comparable with or stronger than that of Trolox (23.2%). The oils of Ichang lemon (64%), Tahiti lime (63.2%), and Eureka lemon (61.8%) were stronger radical scavengers than other citrus oils. The high efficiency may have been caused by the composition of EOs having a higher content of γ-terpinene and terpinolene. Antioxidative properties of EOs from the aerial parts of Pimpinella anisetum and Pimpinella flabellifolia (Tepe et al., 2006) were studied by a DPPH test in methanol. P. anisetum and P. flabellifolia EOs showed an IC50 value of 5.62 and 8.49 μg/mL, respectively, while BHT was less efficient (IC50 5 19.8 μg/mL). The DPPH-scavenging activity of both EOs could be attributed to their high content of methyl chavicol and anethole. G

13.3.4.3 Hydroxyl radical-scavenging activity The hydroxyl radical (HO ) is formed by the reduction of hydrogen peroxide by FeII/Ethylenediaminetetraacetic acid (EDTA) (Fenton reaction) produced in situ from FeIII/EDTA 1 ascorbate. Although essentially indiscriminate due to its extremely high reactivity, HO is assumed to mainly react with deoxyribose added in a large concentration in the test, thus forming aldehydes that react with TBA to form colored adducts. The ability of EOs to scavenge hydroxyl HO was thus measured by IC50 values for the formation of the colored adducts. According to Candan et al. (2003), the EO from Achillea millefolium (IC50 5 2.7 μg/mL) is a much better HO scavenger than curcumin and BHT (IC50 5 14.3 and 32.0 μg/mL, respectively). This could be assigned to the presence of some phenolic compounds, such as borneol and α-terpineol. G

G

G

G

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Green Food Processing Techniques

13.3.4.4 Scavenging of the superoxide radical anion In some studies (Ricci et al., 2005), O2 2 is generated by the xanthine/xanthine oxidase system as a by-product of the conversion of xanthine into uric acid.O2 2 thus formed quickly reduces the nitroblue tetrazolium dye into formazan whose formation can be monitored by UV
vis spectroscopy at 560 nm. In this test, data interpretation is complicated because antioxidants can either reduce O2 or inhibit 2 xanthine oxidase or both. Hence, it may be preferable to use other superoxide generators if true scavenging activities are to be measured. A common method makes use of luminol, which upon irradiation transfers one electron to dioxygen with the 2 concomitant O2 2 formation. Then, O2 quickly reacts with luminol to form a peroxo adduct, which ultimately decomposes into a chemioluminescent product (Mantle et al., 1998). The corresponding light emission at 430 nm can thus be quenched by O2 scavengers, commonly with a pronounced induction period 2 (tIND). The more efficient the antioxidant, the longer the induction period for a given antioxidant concentration. Once more, the results are typically expressed as Trolox equivalents. Using this photo-chemiluminescence method, Sacchetti et al. (2005) were able to show that the T. vulgaris EO (342 mM) was a much more potent superoxide scavenger than the C. odorata, C. longa, C. citratus, and R. officinalis EOs (23.3
66 mM) in agreement with data from the β-carotene bleaching assay.

13.3.4.5 FeIII reduction The efficiency of antioxidants at reducing FeIII to FeII can be considered as a measure of their electron-donating capacity (Oyaizu, 1986). Experimentally, the reduction of ferricyanide by EOs is monitored by UV
vis spectroscopy in water
MeOH mixtures. The reducing power of EO from C. zedoaria (Christm.) Rosc. (Mau et al., 2003) was much lower than those of ascorbic acid, BHA, and α-tocopherol.

13.4

Future trends

EOs have various intrinsic and extrinsic critical challenges, which hindered their application as food preservatives (Prakash et al., 2018). The scarcity of raw materials, chemotypic variation, inconsistent efficacy, lack of molecular mechanism of action, adverse impact on food matrix, low water solubility, high cost, and threat of biodiversity losses are some of the major challenges to EO-based preservatives (Prakash & Kiran, 2016). Regarding the application of EOs in food systems, the major problem is related to the in situ antimicrobial and antioxidant efficacy which can be negatively influenced by various factors, such as binding of the food components (fat or protein molecules). Thus the various properties of EOs offer the possibility of using natural, safe, eco-friendly, cost-effective, renewable, and easily biodegradable antimicrobials and antioxidants for food commodity preservation in the near future (Pandey et al., 2017). Therefore it is possible that additional safety and toxicological data would

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be required before regulatory approval for their use as novel food preservatives. In order to provide stability to foods, new packaging systems are produced by direct mixing of EOs in the packaging films during manufacturing to reduce or inhibit the growth of microorganisms that may be present in the packed food (Avila-Sosa, Palou, & Lo´pez-Malo, 2016). The challenge of using plant extracts, such as EOs in food production, is the lack of reproducibility of their activity due to the diversity of compounds that are present in plants. On the other hand, these compounds present variations due to different cultivars, growing conditions, harvesting times, environmental factors, and extraction processes. The search for alternative processes to heat for the preservation of food is permanent. The use of EOs must respect the organoleptic and nutritional qualities of the food. Extensive toxicological studies are needed to determine their potential toxicity.

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391. Preedy, V. R. (2016). EOs in food preservation, flavor and safety. Elsevier. Raybaudi-Massilia, R. M., Mosqueda-Melgar, J., & Martin-Belloso, O. (2006). Antimicrobial activity of EOs on Salmonella enteritidis, Escherichia coli, and Listeria innocua in fruit juices. Journal of Food Protection, 69, 1579
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Sacchetti, G., Maietti, S., Muzzoli, M., Scaglianti, M., Manfredini, S., Radice, M., & Bruni, R. (2005). Comparative evaluation of 11 essential oils of different origin as functional antioxidants, antiradicals and antimicrobials in foods. Food Chemistry, 91, 621
632. Singh, A., Singh, R. K., Bhunia, A. K., & Singh, N. (2004). Efficacy of plant EOs as antimicrobial agents against Listeria monocytogenes in hot-dogs. LWT—Food Science and Technology, 36, 787
794. Smith-Palmer, A., Stewart, J., & Fyfe, L. (2001). The potential application of plant EOs as natural food preservatives in soft cheese. Food Microbiology, 18, 463
470. Speranza, B., & Corbo, M. R. (2010). EOs for preserving perishable foods: Possibilities and limitations. In A. Bevilacqua, M. R. Corbo, & M. Sinigaglia (Eds.), Application of alternative food-preservation technologies to enhance food safety and stability (pp. 35
57). Bentham Science Publishers. Taga, M. S., Miller, E. E., & Pratt, D. E. (1984). Chia seeds as a source of natural lipid antioxidants. Journal of the American Oil Chemists’ Society, 61, 928
931. Tepe, B., Akpulat, H. A., Sokmen, M., Daferera, D., Yumrutas, O., Aydin, E., . . . Sokmen, A. (2006). Screening of the antioxidative and antimicrobial properties of the essential oils of Pimpinella anisetum and Pimpinella flabellifolia from Turkey. Food Chemistry, 97, 719
724. Tepe, B., Donmez, E., Unlu, M., Candan, F., Daferera, D., Vardar-Unlu, G., . . . Sokmen, A. (2004). Antimicrobial and antioxidative activities of the essential oils and methanol extracts of Salvia cryptantha (Montbret et Aucher ex Benth.) and Salvia multicaulis (Vahl). Food Chemistry, 84, 519
525. Tiwari, B. K., Valdramidis, V. P., O’Donnell, C. P., Muthukumarappan, K., Bourke, P., & Cullen, P. J. (2009). Application of natural antimicrobials for food preservation. Journal of Agricultural and Food Chemistry, 57, 5987
6000. U.S. Code of Federal Regulations. (2016). Title 21—Food and drugs part 182, substances generally recognized as safe. Valgimigli, L., & Pratt, D. A. (2012). Antioxidants in chemistry and biology. In C. Chatgilialoglu, & A. Studer (Eds.), Encyclopedia of radicals in chemistry, biology and materials (Vol. 3, pp. 1623
1677). Chirchester: Wiley. Vergis, J., Gokulakrishnan, P., Agarwal, R. K., & Kumar, A. (2015). EOs as natural food antimicrobial agents: A review. Critical Reviews in Food Science and Nutrition, 55(10), 1320
1323.

Pulsed light as a new treatment to maintain physical and nutritional quality of food

14

Tatiana Koutchma Agriculture and Agri-Food Canada (AAFC), Guelph Research and Development Center, Guelph, ON, Canada

14.1

Introduction

With the current growth of interest in commercial minimal food preservation and sanitation methods, light technologies are emerging in food production both as mild thermal and nonthermal techniques due to their unique effects on microorganisms and minimal impact on foods attributes. Food scientists, engineers, technology providers, and food manufacturers explore a few techniques based on the unique properties of light to interact with foods and their components and food-related microflora. This includes continuous mercury and amalgam low- and medium-pressure ultraviolet (UV) lamps [low-pressure mercury (LPM) and medium-pressure mercury (MPM)], pulsed UV (PUV) light, pulsed light (PL), and light-emitting diodes. In addition to a range of wavelengths generated, each technology utilizes a different type of light generation and demonstrates different power efficiencies, efficacy in terms of microbial inactivation, treatment times, and applications (Table 14.1). In addition to improvement of microbiological safety and products shelf life, enhancement of food functional properties, further development and commercialization of light technologies have much to offer for the sustainable development of food industry. This chapter presents the basics of generation and absorption of PL by microorganisms and food components, PL sources and available equipment, emission spectrum of PUVs and comparison with mercury lamps, effectiveness and mechanisms of microbial inactivation, effects on quality, vitamins, and enzymes and also presents the pros and cons of the potential applications for food and beverages.

14.2

Mode of action of pulsed and pulsed ultraviolet light

PL is characterized by a range of the wavelengths between 170 and 1000 nm and often combines visible and UV photons at energies of 0.01
50 J/cm2. PL is produced using pulsed power energization technique that multiplies the power manyfold, in the order of Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00014-8 © 2019 Elsevier Inc. All rights reserved.

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Table 14.1 Performance comparison of light-based technologies. Continuous

Pulsed

Sources

UV lamps Mercury Amalgam

LEDs Solid state

PUV Microwaved Xenon

PL Xenon

Wavelength range (nm)

253.7

250
400 Tuneable

200
400

170
1000

Spectrum

Monochromatic

Polychromatic

Efficiency (%)

30
33

.5

Up to 30

10

Intensity

mW/area

mW/area

W/area

kW/area

Treatment time

min

h

s-ms

ms

LEDs, Light-emitting diodes; PL, pulsed light; PUV, pulsed ultraviolet; UV, ultraviolet.

megawatts. Power is magnified by storing electricity in a capacitor over relatively long time (less than a second) and releasing it in a short time (millionths or thousandths of a second) using a high speed switch. Electricity is discharged in a xenon lamp that emits a high peak power with a high repetition rate ( . 1 Hz). The intensity of PL is about 20,000 times the intensity of UV light. The xenon lamps are commercial sources of PL that require air or water cooling for the operation. PUV covers the section of the spectrum between 200 and 400 nm and offers some advantages over continuous UV-C light and PL because it is rich in UV-C germicidal light (200
280 nm) and also includes UV-B and UV-A range (280
400 nm band), the higher intensity and shorter treatment times. Microwavepowered electrodeless mercury UV lamps can be used as a source of PUV when operated in pulsing regime. The intensity of the PUV light can be increased depending on the applied microwave power. The xenon lamps, solid-state pulsed lasers, and exciplex lasers also can generate PUV light. Fig. 14.1A shows the emission spectrum of high-intensity pulse (HIP) UV lamp from Phoenix Science and Technology, Inc. (Chelmsford, Massachusetts, United States) that were measured for a single pulse and operated at different frequencies: 10 Hz (HIP-1), 0.75 Hz (HIP-2), and 0.5 Hz (HIP-3). As the pulse frequency decreased, the higher energy was carried by the pulse: 644 J/pulse at 0.5 Hz, 344 J/pulse at 0.75 Hz, and 31 J/pulse at 8 Hz, and consequently the light output shifted upward. The total spectrum of the polychromatic sources covered the range between 200 and 350 nm. For comparison, Fig. 14.1B shows the emission spectra of continuous LPM and MPM lamps. The differences in emission spectra of light sources can result in distinct effects on the quality and composition of treated foods and beverages when they are applied at the similar fluence at 5 mJ/cm2. From the comparison of MPM and HIP lamp spectra, it follows that the HIP lamp was characterized by higher number of peaks in the germicidal UV-C range, while the MPM lamp had more peaks in UV-B range.

Pulsed light as a new treatment to maintain physical and nutritional quality of food

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Irradiance (mW/cm2/nm)

(A) 0.04 HIP-1 at 8 Hz HIP-2 at 0.75 Hz HIP-3 at 0.5 Hz

0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 200

250

300

350

Wavelength (nm) (B)

Irradiance (mW/cm2/nm)

0.5

0.4

LPM MPM

0.3

0.2

0.1

0 200

250 300 Wavelength (nm)

350

Figure 14.1 (A) UV irradiance in the collimated beam setup for the pulsed UV lamp and (B) medium- and low-pressure mercury continuous lamps (B). UV, Ultraviolet.

14.3

Advantages and disadvantages of high-intensity light pulses

The short pulse width and high doses of the PL source may provide some practical advantages over continuous UV sources in those situations where rapid disinfection at high doses is required. Other advantages of PL and PUV treatments are the lack of residual compounds and the absence of applying chemicals that can cause ecological problems and/or are potentially harmful to humans. Sample heating is perhaps the most important limiting factor of PL for practical applications. Heat can originate from the absorption of infrared (IR) part of PL by

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the food or by lamp heating. Another disadvantage of PL treatments is the possibility of shadowing occurring when microorganisms readily absorb the rays.

14.4

Factors affecting interaction between high-intensity pulses and materials

The factors determining the interaction of PL exposure with foods are in some extent similar to UV light treatments. The critical factor affecting PL treatments is fluence incident on the sample. The energy emitted by the flash lamp is different from the energy incident on the sample. Factors, such as distance from light source to target and propagation vehicle (air, water or other fluids, and dust particles), affect the level of energy then ultimately reach the target. The inactivation efficacy of PL is higher when treated products are closer to the lamp. Food composition also affects the efficacy of the decontamination by PL (Go´mez-Lo´pez, Ragaert, Debevere, & Devlieghere, 2007). High-protein and fat containing food products have little potential to be efficiently treated by PL. Vegetables, on the other hand, could therefore be suitable for PL treatment.

14.5

Microbial inactivation mechanism

The microbial inactivation mechanism of continuous light and PL has been extensively studied and reported in the literature (Go´mez-Lo´pez, Koutchma, & Linden, 2011). The UV-C part of the PL spectrum is the most important for microbial inactivation. In both the cases, DNA damage has been identified as the primary lethal event, but inactivation by PL has additional features that may explain its higher efficiency on a per fluence basis including photothermal and physical effects.

14.5.1 Photochemical effect The main lethal event caused by UV-C light on microorganisms is the formation of cyclobutane thymine dimmers in DNA, mainly thymine dimmers. The structural damage caused by the formation of these dimmers inhibits the formation of new DNA, resulting in the inactivation of the affected microorganism. As for PL, this reaction has been called the “photochemical effect.” In order for a photochemical reaction to proceed, the molecules must absorb photons, and they must have enough energy to promote a reaction. LPM lamps have an almost monochromatic output at 253.7 nm, a wavelength that is close to the maximum absorbance of DNA, 260 nm, which explains the sensitivity of this macromolecule to exposure to the emission of LPM lamp. The polychromatic emission spectra of MPM and xenon lamps include also other wavelengths that are absorbed by DNA.

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14.5.2 Photothermal effect The term photothermal effect has been used with two meanings, both having in common microbial inactivation by heat. One is when a large dosage of flash discharge absorbed by microorganisms heats them instantaneously providing a sort of heat inactivation. The other is heating a superficial layer of food product through absorption of light to a temperature effective to inactivate microorganisms. Heat may be localized at a very superficial layer and quickly dissipated without raising interior temperature of the food (Go´mez-Lo´pez et al., 2011). In the first case, PL may still be considered a nonthermal method because heating is localized in the microorganism; while in the second case, PL will be a kind of thermal treatment but without significantly overall heating of the product.

14.5.3 Photophysical effect A third inactivation mechanism has been recently identified by Krishnamurthy, Tewari, Irudayaraj, and Demirci (2009), which refers to the structural damage in microbial cells attributed to the constant disturbance caused by the high-energy pulses. These effects have been observed in Staphylococcus aureus cells that damage due to PL consisted of cell leakage, lack of cell wall, cytoplasmic membrane shrinkage, and collapse of internal structures (Krishnamurthy et al., 2009). The following trend of susceptibility of microorganisms to PL in decreasing order was reported: Gram-negative bacteria, Gram-positive bacteria, and fungal spores. The color of the spores can play a significant role in fungal spore susceptibility. Aspergillus niger spores are more resistant than Fusarium culmorum spores, which could be because the pigment of the A. niger spores absorbs more in the UV-C region than that of the F. culmorum spores, protecting the spore against UV (Go´mez-Lo´pez et al., 2007).

14.6

High-intensity light pulses for food preservation

PL and PUV light has been shown to be an effective process for decontamination of microbes or allergens of many liquid products such as milk, juices, powders, and spices and semisolid foods such as liquid peanut butter, shrimps, shelled eggs, cheese, and meat. The PL is an effective tool for surface decontamination of packaging materials and food contact surfaces. At present, PL is used for decontamination of bottle caps in industrial scale. The PL was tested for its utility to improve the microbial quality and safety of ready-to-Eat (RTE) vacuum
packaged ham and bologna slices inoculated with Listeria monocytogenes. PL treatment at 8.4 J/cm2 reduced L. monocytogenes by 1.78 CFU/cm2 in cooked ham and by 1.11 CFU/cm2 in bologna. The PL at 8.4 J/cm2 did not affect the sensory quality of cooked ham, while treatments above 2.1 J/cm2 negatively influenced the sensory properties of bologna. The combination of PL and vacuum packaging provided ham with an additional shelf

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life extension of 30 days compared with only vacuum packaging. In addition, the effectiveness of PL was demonstrated for the treatments of RTE chicken frankfurters (Sommers, Geveke, Pulsfus, & Lemmenes, 2009). In another study, effectiveness of high intensity near UV/visible (NUV
vis) 395 6 5 nm light against Campylobacter was assessed at three distances from the light source for up to 10 min, corresponding to doses of 0.06
18 J/cm2 for the decontamination of raw chicken and contact surfaces. The exposure of skinless chicken fillet to NUV
vis light for 1 or 5 min at 3 cm distance reduced Campylobacter jejuni by 2.21 and 2.62 log10 CFU/g, respectively. For Enterobacteriaceae and total viable counts, significant reductions were achieved only on chicken fillet samples. Light treatments were significantly effective for decontaminating contact surfaces as there was no C. jejuni recovered from stainless steel or cutting board surfaces after NUV
vis light treatments from an initial inoculum of 2
4 log10 CFU/cm2(P , .05). The study demonstrated potential for the use of NUV
vis light for the inactivation of Campylobacter spp. in liquids, on raw chicken and contact surfaces. The PL can also be used for in-package pasteurization of foods provided that the packaging has high PL transmissivity. The combination of PL and vacuum packaging provided ham with an additional shelf life extension of 30 days compared with single vacuum packaging. Also, as a nonthermal postharvest intervention method, PUV treatment is reported to be effective at reducing microbial loads on fruits and vegetables. The antimicrobial efficacy of PUV light treatment on nascent biofilms formed by Escherichia coli O157:H7 and L. monocytogenes on the surfaces of food packaging materials, such as low-density polyethylene, and fresh produce, such as lettuce leaves, also has been reported (Montgomery & Banerjee, 2015). The effectiveness of microbial inactivation is defined by the optical properties of food, the growth stage of microorganisms, the resistance of the microorganisms, and the amount of energy supplied to the microbial culture. For a simple food matrix, significant inactivation of target microorganisms can be achieved within a few seconds. The spores may exhibit more resistance to PL due to a thick protein coat. Unlike vegetative cells, spores produce minimal or no thymine dimers and predominantly produce spore photoproducts (5-thyminyl-5,6-dihydrothymine adducts). In general, PL is effective in inactivating various spores. Limited studies indicate that PL can be successfully used for the inactivation of yeasts from buffer, agar surfaces, food, or food contact surfaces. A 3- to 7-log reduction of various yeasts (Saccharomyces cerevisiae, Candida lambica, and Rhodotorula mucilaginosa) was observed in buffer or on agar surfaces.

14.7

Pulsed light effects on quality, enzymes, and functionality

Orlowska et al. (2013) evaluated performance of three HIP PUV sources characterized by different emission spectra, energy per pulse, and frequency (HIP-1: 31 J/pulse, 8 Hz; HIP-2: 344 J/pulse, 0.75 Hz; and HIP-3: 644 J/pulse, 0.5 Hz) at similar fluence of

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5 mJ/cm2 by measuring the effects on quality parameters of fructose, apple juice, and milk. The results were compared with the continuous monochromatic LPM and polychromatic MPM lamps at the UV fluence of 10 mJ/cm2 that was determined based on 5-log microbial reduction requirement. The effects of HIP-1 and HIP-3 pulsed lamps on color, pH, and vitamin C were comparable with the LPM lamp. For example, pH of fructose decreased by 1.94% for the LPM lamp and by 0.78% and 4.31% for HIP-1 and HIP-3, respectively. Treatment with the LPM lamp reduced the vitamin C content by 1.3% in apple juice and 35% in milk. In the case of PL the reduction of vitamin C was 0.85% for HIP-1 and 1.78% for HIP-3 in apple juice, 12% (HIP-1) and 21.7% (HIP-3) in milk. HIP-2 and MPM lamps caused the most significant deterioration of the quality parameters in all tested liquids. The HIP-2 lamp decreased vitamin C by 8.5% in apple juice and 35.8% in milk and also reduced fructose pH by 5.3%. These results indicated that treatment with pulsed HIP-1 and HIP-3 sources could represent a promising alternative for the treatment of low UV transparent and opaque liquid foods. The stability of juice quality and nutritional properties is often dependent on the activity of the enzymes present in plants. Limited and often controversial information is reported in the literature in regard to the effect of PL on the activity of certain enzymes associated with juices and milk, including polyphenol oxidase (PPO), peroxidase, lipoxygenase, and pectin methylesterase and alkaline phosphatase (AP), the indigenous enzyme present in milk. Destruction of AP is used in dairy industry as an indicator of proper thermal pasteurization of milk. Fig. 14.2A shows that AP has the maximum of absorbance at 280 nm that is overlapped by PL peaks at 267.5, 273, and 286 nm. Raw milk treatment with the PUV and LPM lamps only slightly affected the AP activity. In the case of LPM lamp exposure of milk at 10 mJ/cm2 similar PUV treatment at 5 mJ/cm2, the AP enzyme residual activity was B92%. PPO is the enzyme that can cause browning in apple juices with absorbance maximum at 280 nm. Under similar exposure conditions of fresh apple cider to PUV and LPM (Fig. 14.2B), residual activities of PPO were 85% and 82%, respectively. Total phenolic content and antioxidant activity in apple cider were insignificantly affected by PL with the relative changes less than 5%. Fig. 14.2 shows the emission spectra of LPM and PL sources (marked HIP-3) and compares them with absorption spectra of raw milk, riboflavin, and vitamin C. The content of vitamin C can be used as an indicator of oxidative processes in light processed milk. Also, the loss of ascorbic acid in milk can be associated with the destruction of riboflavin, known as vitamin B2. Riboflavin is a photosensitive compound, and its photolysis leads to the formation of lumiflavin and lumichrome that catalyze oxidation of vitamin C, proteins, lipids, and methionine. As can be seen in Fig. 14.2, riboflavin is characterized by absorbance peaks in the UV-C range with the maximum at 222 and 266 nm. The effect of PUV emission spectrum on vitamin C destruction has been shown in milk treated with the LPM and PUV HIP-3 lamps with partially blocked wavelengths using quartz filter in both cases. The treatment of milk with LPM lamp was used as a base line for comparison of vitamin C destruction at 254 nm and equivalent dose of 5 mJ/cm2.

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(A) 1.4

8.0E–05 Raw milk

7.0E–05

Alkaline phosphatase

1.2

HIP-3 lamp

5.0E–05 0.8 4.0E–05 0.6

Irradiance

Absorbance

6.0E–05

LPM lamp

1.0

3.0E–05 0.4

2.0E–05

0.2

0.0 200

1.0E–05

220

240

260

280

300

320

340

0.0E+00 360

Wavelength (nm) (B) 1.0

8.0E–05 Apple cider

0.9

Polyphenol oxidase

7.0E–05

0.8

LPM lamp

6.0E–05

Absorbance

0.7

5.0E–05

0.6 4.0E–05 0.5 3.0E–05 0.4 2.0E–05 0.3 1.0E–05

0.2

0.0E+00

0.1 0.0 200

Irradiance (J/pulse/nm/cm2)

HIP-3 lamp

–1.0E–05 220

240

260 280 300 Wavelength (nm)

320

340

Figure 14.2 (A) Absorption spectra of raw milk in 0.2 mm quartz cuvette and alkaline phosphatase 0.097 mg/mL; 10 mm quartz cuvette compared with the emission spectra of PL and LPM lamps. (B) Absorption spectra of apple cider in 0.2 mm quartz cuvette and aqueous solution of polyphenol oxidase 0.12 mg/mL; 10 mm quartz cuvette compared with the emission spectra of PL and LPM lamps. LPM, Low-pressure mercury; PL, pulsed light.

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399

8.0E–05

1.2 Vitamin C Riboflavin

1.0

6.0E–05

HIP-3 lamp

0.8

5.0E–05 0.6

4.0E–05 3.0E–05

0.4

Irradiance (J/cm2/pulse)

Filter

Absorbance

7.0E–05

Milk

2.0E–05 0.2 1.0E–05 0.0 200

220

240

260

280

300

320

340

0.0E+00 360

Wavelength (nm)

Figure 14.3 Emission spectra of PUV source with quartz filter and absorbance of milk in 0.2 mm quartz cuvette, vitamin C at 1 mg/mL in 2 mm quartz cuvette, and riboflavin at 0.08 mg/mL in 0.5 mm quartz cuvette. PUV, Pulsed UV; UV, ultraviolet.

Fig. 14.3 presents absorption characteristic of milk, vitamin C, and riboflavin along with the emission spectra of PL HIP-3 lamp and its emission spectrum using quartz filter. The application of quartz filter on LPM lamp did not cause the change of vitamin C destruction in milk that remained at approximately of 30% loss level. At the identical dose of 5 mJ/cm2, similar decrease in vitamin C content was also found in milk treated with PUV lamp without filter. However, the application of filter on PUV lamp caused double destruction of vitamin C at the level of 60%. As seen in Fig. 14.3, the quartz lamp filter blocked PUV peaks in the range from 200 to 228 nm and from 230 to 254 nm. However, peaks at 229 and 259 nm were overlapping with the maximum of riboflavin absorbance at 223 and 268 nm and caused higher reduction of vitamin C. Considering the differences in the components absorption and emission spectra, the photolysis of riboflavin and related vitamin C loss can be attributed to the UV wavelength effects in a range of 250
270 nm. In general, according to Koutchma, Forney, and Moraru (2009), the use of PL treatment is not considered to pose any new nutritional safety concerns when used at the doses not exceeding 12 J/cm2 recommended by US Food and Drug Administration (FDA). PL and PUV light can have beneficial effects on health-related compounds such as increase of vitamin D content in mushrooms. The mushrooms contain the precursor ergosterol that is converted to ergocalciferol (vitamin D2) when

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mushrooms are exposed to light. Studies have shown that the concentration of vitamin D2 in mushrooms might be increased by as much as 467% by postharvest PL or UV light illumination. Depending on the type of mushroom and the treatment that the mushrooms have received, the vitamin D levels can vary. Overall, PL-treated mushrooms can be a good source of vitamin D2, and PL can be used to prepare mushrooms with high vitamin D2 content as a nutrient supplement.

14.8

Pulsed light sources and equipment

Xenon flash lamps have an emission spectrum ranging from UV to IR light. The UV-C part of the spectrum is the most important for microbial inactivation. The pioneer company producing PL equipment for disinfection was PurePulse Technologies Inc. (San Diego, California), a subsidiary of Xenon Corporation. Applications included water purification systems and virus inactivation systems for biopharmaceutical manufacturers. Nowadays, there are three commercial companies producing pilot scale and commercial systems based on PL: Claranor from France, SteriBeam Systems from Germany, and Xenon Corporation from the United States. The detailed information regarding the devices for industrial applications can be found at the websites of these companies.

14.9

Conclusion

Code 21CFR179.41, issued by the US FDA in 1996, approved the use of PUV light in the production, processing, and handling of food. The PL may be safely used for the treatment of foods under the following conditions: (1) the radiation sources consist of xenon flash lamps designed to emit broadband radiation consisting of wavelengths covering the range of 200
1000 nm and operated so that the pulse duration is no longer than 2 ms; (2) the treatment is used for surface microorganism control; (3) foods treated with PL shall receive the minimum treatment reasonably required to accomplish the intended technical effect; and (4) the total cumulative treatment shall not exceed 12.0 J/cm2. In assessing the safety of foods treated with all forms of radiation, the international government agencies consider changes in chemical composition of the food that may be induced by the proposed treatment, including any potential changes in nutrient levels. The legal status of light treatments in the European Union is determined by different approach, since the legislation is not technology oriented but food and food ingredient oriented. The light technologies would fall in the scope of regulation 258/97 on novel foods and novel food ingredients, Article 1, Item f. The approval process is based on the risk assessment approach that includes microbiological, chemical, and toxicological safety; possible changes in composition and nutrition content; allergenicity; and dietary exposure.

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The US FDA’s approval of PL gave rise to numerous scientific research of PL treatment of food, food contact surfaces, and processing environments. Despite the effort made, the potential of PL on foods is still under investigation, and the gap between the basic research and commercialization seems to be remaining. In industrial scale the PL technique is applied for packaging decontamination, although systems for other applications are already patented or launched in the market. Product heating that can originate from the absorption of infrared part of PL spectrum by the food or by lamp heating is perhaps the most important limiting factor of PL. The main hurdle for commercialization of PL technology for food and beverage applications is the limited number of commercial units and the lack of control of operational dose and standardized validation procedures. In order to explore the full potential of novel PL and PUV sources for applications in the food industry and to optimize treatment conditions, more studies have to be performed using commercial PL equipment tuned for specific foods with the focus on safety and quality parameters of tested products. Although there are a number of benefits for light-based technologies in food industry, cost-saving opportunities of energy, processing water, and enhanced safety need to be carefully considered in each specific case for successful technology implementation and to assure positive outcomes.

References Go´mez-Lo´pez, V. M., Koutchma, T., & Linden, K. G. (2011). Ultraviolet & pulsed white light. In P. J. Cullen, B. Tiwari, & V. Valdramidis (Eds.), Novel and non-thermal technologies for fluid foods. Elsevier, Chapter. Go´mez-Lo´pez, V. M., Ragaert, P., Debevere, J., & Devlieghere, F. (2007). Pulsed light for food decontamination: A review. Trends in Food Science and Technology, 18, 464
473. Koutchma, T., Forney, L., & Moraru, C. (2009). Ultraviolet light in food technology: Principles and applications. Boca Raton, FL: CRS Press. Krishnamurthy, K., Tewari, J. C., Irudayaraj, J., & Demirci, A. (2009). Microscopic and spectroscopic evaluation of inactivation of Staphylococcus aureus by pulsed UV light and infrared heating. Food and Bioprocess Technology, 3, 93
104. Montgomery, N., & Banerjee, P. (2015). Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes in biofilms by pulsed ultraviolet light. BMC Research Notes, 8, 235. Available from https://doi.org/10.1186/s13104-015-1206-9. Orlowska, M., Koutchma, T., Grapperhaus, M., Gallagher, J., Schaefer, R., & Defelice, C. (2013). Continuous and pulsed ultraviolet light for nonthermal treatment of liquid foods. Part 1: Effects on quality of fructose solution, apple juice, and milk. Food and Bioprocess Technology, 6(6), 1580
1592. Sommers, C. H., Geveke, D., Pulsfus, S., & Lemmenes, B. (2009). Inactivation of Listeria innocua on Frankfurters by ultraviolet light and flash pasteurization. Journal of Food Science, 74(3), M138
M141.

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Pulsed electric field in green processing and preservation of food products

15

Eugene Vorobiev1 and Nikolai Lebovka1,2 1 Sorbonne Universities, University of Technology of Compiegne, Laboratory TIMR, Research Center of Royallieu, Compiegne, France, 2Institute of Biocolloidal Chemistry Named After F.D. Ovcharenko, NAS of Ukraine, Kyiv, Ukraine

15.1

Introduction

Food processing aims to preserve the quality of final products during numerous unit operations and/or to recover the maximal quantity of valuable substances from food stuff and biomass feedstocks. Green processing methods (e.g., cold mechanical pressing, green solvents extraction, nonpolluting purification, and nonthermal preservation of foods) provide mild transformation of food and biomass materials and create a minimal quantity of wastes (Clark & Macquarrie, 2008; Proctor, 2018). Unfortunately, green methods are often insufficient for obtaining high processing output and good recovery of valuable compounds. Preliminary rupture of cell matrix of food plants is needed to recover target molecules and products. A high temperature is often used to dehydrate food materials. In conventional food processing, cell tissues are often denaturated mechanically (using fine cutting, grinding, milling, and crushing), thermally (by scalding, blanching, heating, and freeze-thawing), chemically (e.g., by lime), or biologically (by enzymes). In some cases the upstream operations, such as cutting and scalding, are sequenced (e.g., in sugar processing) to maximize the processing yield. Conventional treatments disrupt material structure (both cell membranes and cell walls) effectively and enhance the following mass and heat transfer operations (pressing, solvent extraction, frying, etc.). Unfortunately, different undesirable reactions (oxidation, Maillard, etc.) can be provoked by these preliminary treatments that worsen product quality and complicate purification operations. Moreover, important structural elements of mechanically or thermally disrupted cells are destroyed or released during conventional treatments. Then cell tissue can lose its retaining capacity and become easily permeable not just for target compounds but also for undesirable substances (impurities) contaminating extract and complicating downstream processing. The downstream extraction operations often use heating (e.g., by hot water in sugar, stevia, or inulin processing), chemicals (e.g., hexane in oilseed extraction), and enzymes (e.g., pectinase in apple juice processing) to recover the maximal Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00015-X © 2019 Elsevier Inc. All rights reserved.

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Green Food Processing Techniques

quantity of juice or target substances. Complex and multistage separation, which is needed to purify obtained extracts and solid residues, again uses chemicals (e.g., lime in sugar processing) and creates additional wastes. In the case of food plant dehydration, a high drying temperature is not just highly energy consuming but also leads to the loss of food quality. Milder methods of cell tissue damage are needed to preserve the food quality better and provide more selective recovery of target cell compounds (BarbosaCa´novas, Pothakamury, Palou, & Swanson, 1998). Pulsed electric field (PEF) is considered a nonthermal treatment of very short duration (from several microseconds to several milliseconds) with pulse amplitude from 100
300 V/cm to 20
80 kV/cm. Under the effect of PEF the biological membrane is electrically pierced and loses its semipermeability temporarily or permanently (Miklavcic, 2017; Weaver & Chizmadzhev, 1996). The electrical permeabilization of biological membranes (called electroporation) may be reversible or irreversible. For a spherical cell in the external field the induced transmembrane potential um is a function of cell radius R, field strength E, and position of the observation point on the surface of membrane (Miklavcic, 2017):

t  um 5 1:5REf cosθ 1 2 exp 2 τ

(15.1)

where θ is the angle between the external field E and radius vector on the surface of a membrane, f is the electroporation factor that is dependent on geometry and electrophysical properties of cells, and τ (  1
10 μs) is the time constant reflecting charging of capacities in the membranes. For the anisotropic cells the value of um is a function not only of electric field intensity E and cell size R but also of the cell shape and orientation. Typically, the critical value of transmembrane potential needed for the electroporation is of the order of umc  0.7
1.2 V (Zimmermann, 1986). Supposing tctc , f 5 1, and umc 5 1 V, we find at the cell poles (i.e., at cos θ 5 1) for the critical electric field intensity Ec 5 (1.5 R)21. It gives the value of Ec 5 0.67 kV/cm for electroporation of plant tissue with cell radius R 5 10 μm, and Ec 5 13.4 kV/cm for electroporation of microorganism with cell radius R 5 0.5 μm. In biological systems the electroporation can induce different effects: the small and/or large molecules can be introduced into cells or extracted from them, proteins can be inserted into the membrane, and cells can be fused (Miklavcic, 2017). Nowadays electroporation has found applications in biochemistry, molecular biology, and medicine. For instance, this phenomenon has been applied to amplify the insertion of nucleic acid molecules in genetic modifications (Jordan, Neumann, & Sowers, 1989), to enhance drug transport in cancer treatment—named electrochemotherapy (Mir & Orlowski, 1999) and other applications (Kim & Lee, 2017; Pakhomov, Miklavcic, & Markov, 2010; Saito, 2015; Sundararajan, 2014). Potential of food and environmental applications of electroporation is very important: cold extraction of sugar from sugar beets; selective extraction of valuable

Pulsed electric field in green processing and preservation of food products

Intact EEc

E

θ Cell

Cell

Cell walls

Figure 15.1 Intact and electroporated cell membrane. Large molecules can be retained by electroporated cell membranes or by tissue matrix.

compounds from various food plants, coproducts, and microalgae; nonthermal preservation of liquid foods; enhancement of mass and heat transfer, etc. (Vorobiev & Lebovka, 2008). Probably, one of the most important functional features of electroporation is creating the good conditions for selective sieving of smaller or larger compounds through cellular membrane and cell wall structure (Fig. 15.1). Cell walls represent additional barrier for the transport of macromolecules outside of damaged cells. Cell walls, composed of cellulose microfibrils linked via hemicellulosic tethers, form a cellulose
hemicellulose network, which is embedded in the pectin matrix. Conventional mechanical and thermal treatments lead to the breakage of both cell membranes and cell walls and also to the uncontrolled release of intracellular and extracellular substances. PEF differs from other treatments by better controlled damage of cellular membranes and preservation of cell walls from important destruction. Plant tissue with damaged cell membranes but with conserved cell wall network is selectively permeable, and it is capable of better retaining of cell compounds. The capacity of the cell network to act as a barrier for the passage of some undesired compounds is a big advantage and allows improvement in extraction selectivity (Vorobiev & Lebovka, 2017b).

15.2

Impact of pulsed electric field on cell tissue and biosuspensions

PEF parameters (intensity of electric field E, duration of pulse tp, number of pulses n, distance between pulses Δtp, pulses frequency, form of pulses, and their monoor bipolarity) influence importantly on the electroporation phenomena (Barba et al., 2015). Product characteristics (size and firmness of cells, intra- and extracellular electrical conductivities, difference in cell structure) are determinant to choose the

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appropriate PEF treatment parameters (Ben Ammar, Lanoiselle´, Lebovka, Van Hecke, & Vorobiev, 2011). Successfulness of PEF treatment can be detected by different methods: visually (food surface humidification by released intracellular juice, modification of extract color), microscopically (solid structure, distribution of fluorescent molecules in cells with damaged membranes), using magnetic resonance imaging, electrical impedance tomography, characterizing mechanical, acoustical, physicochemical, electrophysical, and other food properties modified by PEF (Barbosa-Ca´novas et al., 1998; Vorobiev & Lebovka, 2015). Fig. 15.2 shows examples of cell structure of food plants treated by PEF. It is easy to see that the cell wall structure of the grape skin and cell walls of red beet remain practically intact after electroporation. Similar results demonstrative of a good preservation of cell matrix by PEF were obtained in many other studies (see, for example, Cholet et al., 2014; Fincan & Dejmek, 2002). Fig. 15.3 shows the curves of stress relaxation tests P(ε) for carrot, potato, and apple samples (disks of 12 mm in diameter and 9 mm of thickness) treated by PEF (E 5 1100 V/cm) or heated (T 5 65 C) and cooled (Lebovka, Praporscic, & Vorobiev, 2004). After the PEF treatment the tissues lost a part of their initial strength. However, the PEF-treated tissues are clearly stronger than heated/cooled tissues. Especially, PEF-damaged potato and carrot show close stress
deformation behavior to their intact tissues. This is an established fact that PEF treatment preserves significantly better cell wall matrix than scalding or blanching (Vorobiev & Lebovka, 2011). It can be explored for the development of purer and greener food processing. One of the most accessible and reliable methods to detect the membrane electroporation is based on the determination of electrical conductivity disintegration index Zc (Vorobiev & Lebovka, 2011): Zc 5

σ 2 σi σd 2 σi

(15.2)

where σ is the electrical conductivity value measured at low frequency (  1 kHz) and indices “i” and “d” refer to the conductivities of intact and totally damaged tissue, respectively. Eq. (15.2) gives Zc 5 0 for the intact tissue and Zc 5 1 for the totally electroporated membranes. Fig. 15.4 presents examples of the electrical conductivity disintegration index Zc versus the time t for PEF, ohmic heating, freeze-thawing, and heating treatments (Parniakov, Lebovka, Bals, & Vorobiev, 2015).

15.3

Food processing with pulsed electric field

PEF treatment can immensely modify the food processing chain influencing numerous downstream processing (Fig. 15.5).

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407

Figure 15.2 Microscopic pictures of cells from the skin tissue of Lemberger wine grapes before (A) and after (B) electroporation. The pigments are stored inside a vacuole and released after electroporation. Microscopic pictures of cells after extraction from untreated (C) and electroporated (D) red beet tissue. The pigments are better extracted from electroporated tissue. Source: (A) and (B) Adapted from Sack, M., Sigler, J., Eing, C., Stukenbrock, L., Stangle, R., Wolf, A., & Muller, G. (2010). Operation of an electroporation device for grape mash. IEEE Transactions on Plasma Science, 38(8), 1928
1934. (C) and (D) Adapted from Loginova, K. V., Lebovka, N. I., & Vorobiev, E. (2011). Pulsed electric field assisted aqueous extraction of colorants from red beet. Journal of Food Engineering, 106(2), 127
133 (Loginova, Lebovka, & Vorobiev, 2011).

PEF can be applied directly to whole food materials (tubers, roots, and fruits) submerged in water or it can be applied to mechanically fragmentized materials (after upstream slicing, grinding, and/or mild heating) submerged in water or previously compacted. Biomass feedstocks (microalgae and green biomass) can also be effectively treated by PEF.

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(B)

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1.5

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2 0.1

4

3

4

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5 0 0

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ε

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ε

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Figure 15.3 The curves of stress P versus relative deformation ε 5 Δh/h for apple, carrot, and potato tissues (Δh and h are the changes and initial samples height, respectively): (A) the untreated samples and (B, C, D) PEF-treated samples at electric field intensity E 5 1100 V/cm, and time of PEF treatment tPEF 5 0(1), 2  1024 s(2), 1021 s(3). Curves 4 (B, C, D) and 5 (B, C, D) correspond to the thermally treated (during the 2 h at temperature T 5 65 C K) and freeze-thawed tissues, respectively. PEF, Pulsed electric field. Source: Adapted from Lebovka, N. I., Praporscic, I., & Vorobiev, E. (2004). Effect of moderate thermal and pulsed electric field treatments on textural properties of carrots, potatoes and apples. Innovative Food Science & Emerging Technologies, 5(1), 9
16.

Mechanical compaction of sliced food materials permits to exclude or minimize water addition during PEF treatment to decrease electric energy consumption. Mild preheating leads to some softening of cell structure and easier electroporation. Cell membrane electroporation can modify mechanical, physicochemical, electro- and thermophysical properties of treated materials. Successful PEF treatment can revolutionarily modify downstream food processing replacing highly energy-consuming and environment-polluting operations on colder operations, which are “solvent free” or use green solvents. PEF extracts are purer than the ones obtained after conventional extraction, and purification of PEF extracts creates fewer wastes. Different mass and heat transfer operations (extraction, drying, osmotic dehydration, freezing, fermentation, etc.) may become shorter and milder after the PEF treatment and preserve better product quality.

Electrical conductivity disintegration index, Zc

Pulsed electric field in green processing and preservation of food products

409

1

PEF

OH

H

FT

0.8

Apple 0.6

0.4

0.2

0 10 –4

10 –2

10 0

10 2

10 4

10 6

Time of treament, t (s) Figure 15.4 Electrical conductivity disintegration index Zc versus the time of treatment t for PEF (800 V/cm, T 5 20 C), OH (40 V/cm, Tmax 5 55 C), FT (T 5 240 C), and H (60 C) treatments of apples. FT, Freeze-thawing; H, heating; PEF, pulsed electric field; OH, ohmic heating. Source: Adapted from Parniakov, O., Lebovka, N., Bals, O., & Vorobiev, E. (2015). Effect of electric field and osmotic pre-treatments on quality of apples after freezing-thawing. Innovative Food Science & Emerging Technologies, 29, 23
30.

Upstream Slicing, mild heating

PEF

Downstream Cold pressing, Cold or mild solvent Extraction,

Simplified liquid purification, Solids dehydration, Secondary extraction ,

Mild drying, Osmotic dehydration, Freezing

Figure 15.5 Food processing with PEF. PEF, Pulsed electric field.

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Green Food Processing Techniques

15.3.1 Upstream processing Upstream processing refers to the preliminary treatment of material (e.g., mechanical fragmentation of food plants and preheating) that can modify cell structure and influence the efficiency of both PEF treatment and downstream processing. The finesse of mechanical fragmentation (slicing or grinding) of roots and tubers results in higher or lower quantity of cells disrupted prior to PEF treatment. Just the cell membranes remained intact after mechanical fragmentation can be electroporated. Fig. 15.6 shows the influence of sugar beet slicing on the following pressing with and without PEF treatment (Grimi, 2009). Sugar beets were previously sliced to obtain the cuts of four different sizes: S1 (0.15 3 0.15 3 2 mm3), S2 (1.5 3 1 3 20 mm3), S3 (4 3 1.5 3 25 mm3), and S4 (7 3 3 3 30 mm3). Then cuts were treated by PEF (E 5 400 V/cm, tPEF 5 100 ms) and pressed at 11 bars during 10 min. Results were compared with pressing of untreated samples at the same pressure and duration (Grimi, 2009). Mechanical disintegration index (Zm) was defined as Zm 5

Nd Nd 1 Ni

(15.3)

where Nd and Ni are the numbers of mechanically damaged by slicing and intact cells, respectively, which were estimated for each size of particles based on the characteristic size of cell 50 μs and taking supposition that just the layer of cells settled on the surface of the particle is damaged by slicing. Accordingly, the values of Zm (in %) for each particle size were as follows: for S1 2 Zm 5 76%, for S2 2 Zm 5 20%, for S3 2 Zm 5 9%, and for S4 2 Zm 5 7%. With increase of mechanical disintegration index Zm the pressing yield logically increases for both untreated and PEF pretreated slices. However, after the PEF treatment, juice yield increases importantly even for the largest slice S4 having just 7% of mechanically disintegrated cells, while for PEF-untreated slices fine slicing is needed (particles S1 with 76% of mechanically disintegrated cells) to enhance the juice yield immensely (Fig. 15.6). Fig. 15.6B shows clearly the main disadvantage of fine slicing: with higher quantity of mechanically disintegrated cells the juice purity (defined as the quantity of expressed sugar to the total quantity of soluble solids in juice) decreases. It can be explained by worse retainment of juice impurities by mechanically disrupted cells comparatively to the electroporated ones. Similar tendency was confirmed for carrot, potato, chicory, and apple cuts both on the laboratory and pilot scale, using the belt press (Grimi, 2009). Therefore with PEF treatment, the parameters of upstream fragmentation of roots and tubers should be completely revised. For more selective release of valuable compounds the percentage of mechanically disrupted cells should be decreased, and more coarse particles should be produced by slicing or grinding. It can be even interesting to treat the whole roots or tubers (previously to slicing) by PEF. Fig. 15.7 shows the cutting force, which is needed to cut the whole apple and carrot untreated and treated by PEF (E 5 400 V/cm, tPEF 5 100 ms) (Grimi, 2009). After

Pulsed electric field in green processing and preservation of food products

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(A) 80

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76

Mechanical disintegration index, Zm (%) Figure 15.6 Juice yield, Y (A), and purity, P (B), after pressing of sliced sugar beet particles with different degrees of cell disintegration. Symbols S1
S4 correspond to the cuts of different sizes.

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Green Food Processing Techniques

(A)

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With PEF

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Force, F (N)

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Time, t (s) Figure 15.7 Force needed for cutting of whole carrot (A, B) and apple (C, D) untreated or treated by PEF (E 5 400 V/cm, tPEF 5 100 ms). PEF, Pulsed electric field. Source: Adapted from Grimi, N. (2009). Vers l’intensification du pressage industriel des agroressources par champs e´lectriques pulse´s : e´tude multi-e´chelles. PhD thesis, UTC, Compie`gne, France.

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the PEF treatment the cutting force decreases on about 20% and 50% to cut, respectively, the whole apple and carrot. This can be advantageous to decrease energy content but also produces the products of better quality. For instance, french fried potatoes are prepared from whole white potatoes by cutting. The cuts are blanched and then fried. However, blanching influences negatively on the texture and taste of potato chips due to cell wall degradation by heat and starch gelatinization. To prevent the dark color of the blanched potato, some chemicals (e.g., sulfites) are usually added, which is undesirable for consumers (Ignat, Manzocco, Brunton, Nicoli, & Lyng, 2015). The whole potatoes can be submitted to the PEF treatment prior to frying (Liu et al., 2017; Toepfl, Siemer, & Heinz, 2015). It was shown (Ignat et al., 2015) that after PEF application, only reducing sugars and small molecules were released from the potato raw material, whereas larger substances such as starch and proteins remained inside the cells. Pretreated potatoes presented lower peak force in comparison to the raw control samples (Fauster et al., 2018; Grimi et al., 2009; Toepfl, 2006). About 35% less energy was required to cut PEF-treated samples compared to untreated samples (Ignat et al., 2015). Surface of obtained cuts is smooth and highly humidified due to the release of cellular juice. The thin layer of cellular juice on the surface of cuts creates some barriers reducing oil uptake during frying. Besides health advantages, this process economizes better oil use and reduces the quantity of wastes. Industrial PEF process of french fried potatoes is actually commercialized (Fauster et al., 2018; Toepfl et al., 2015). Recently, it was shown on the industrial scale (35 tons/h) that PEF treatment of whole tomatoes improves their peeling (Arnal et al., 2018; Pataro et al., 2018). The PEF treatment (E 5 0.2
0.5 kV/cm, pulse duration 20 μs, energy input 0.2
0.5 kJ/ kg) was applied during the upstream washing of tomatoes. When the PEF technology is incorporated in the process, it reduces the amount of steam and natural gas used in the thermophysical peeling. The energy consumption was lower, but also it was easier to peel the tomatoes (Arnal et al., 2018).

15.3.2 Downstream processing PEF treatment can immensely modify the downstream processing. It can enhance mass and heat transfer in extraction and dehydration operations, assure selective recovery of target intracellular compounds, and make downstream processing greener, nonthermal, or mild thermal, to obtain finally the products of better quality (Fig. 15.8).

15.3.2.1 Cold or mild thermal extraction in sugar beet processing Conventional sugar beet technology includes hot water extraction and complex multistage purification of the extract (diffusion juice). Sugar beets are initially sliced to obtain fine cossettes, and then cossettes are subjected to cell denaturation by scalding (using hot juice at 95 C), followed by aqueous countercurrent diffusion at 70 C
75 C for 60
90 min (Der Poel, Schiweck, & Schwartz, 1998). Diffusion

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Green Food Processing Techniques

Downstream processing

PEF

Extraction/dehydration Solute extraction

Pressing

Osmotic dehydration

Drying

Freezing

Frying

Selective Nonthermal or mild heating

Stress/ inactivation Nonthermal or mild heating

Higher yield, mass, heat transfer Better food quality

Figure 15.8 Downstream processing with PEF. PEF, Pulsed electric field.

juice contains many impurities, such as proteins, pectins, reducing sugars, amino acids, and pigments, which are eliminated during multistage purification including preliming, main liming, first and second saturation, several filtrations, and sulfitation. The obtained thin juice is then concentrated by water evaporation. Then syrup is crystallized to obtain sugars and molasses. Electroporation of sugar beet cells opens new ways for the improvement of sugar beet processing. G

G

G

G

cellular juice extraction by cold pressing without heating; aqueous diffusion of sucrose at lower temperatures, during shorter time, or using lower quantity of water; new combinations of pressure and aqueous extraction; and improvement of downstream juice purification.

Recent publications (Almohammed, Mhemdi, Grimi, & Vorobiev, 2015; Almohammed, Mhemdi, & Vorobiev, 2016, 2017; Loginova, Vorobiev, Bals, & Lebovka, 2011; Mhemdi, Bals, Grimi, & Vorobiev, 2014; Mhemdi, Bals, & Vorobiev, 2016; Miklavcic, 2017; Vorobiev & Lebovka, 2017a) explored different schemes of sugar beet processing using PEF. Fig. 15.9 presents the yield of soluble solids expressed from the electroporated sugar beet cossettes by four cold pressings at ambient temperature, when diffusion operation was completely excluded. The first pressing of electroporated (E 5 600 V/cm, tPEF 5 10 ms) cossettes was realized under the pressure of 15 bars. The press cake (pulp) was then impregnated by the lime milk at the temperature of 10 C. The quantity of the added lime milk was fixed at 0.6 kg CaO/100 kg of sugar beets. The lime addition increases the yield of soluble solids significantly after the second pressing (from 87% to 94%) (Fig. 15.9). The third and fourth pressings, each with the addition of w 5 5% water to the mass of beets, reveal more effective results than just the sole third pressing with the addition of w 5 10% water to the mass of beets. The yield of soluble solids was 99.53% when third and fourth

Pulsed electric field in green processing and preservation of food products

Yield of soluble solids, Y (%)

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Sugar beet With lime

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Pressing W = 5%

75

W = 5%

W = 10% 70 0

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Pressing time, t (min) Figure 15.9 Yield of soluble solids expressed from the electroporated (E 5 600 V/cm, tPEF 5 10 ms) cossettes (first pressing) and from the first, second, and third pulp (second, third, and fourth pressing). Source: Adapted from Almohammed, F., Mhemdi, H., & Vorobiev, E. (2016). Several-staged alkaline pressing-soaking of electroporated sugar beet slices for minimization of sucrose loss. Innovative Food Science & Emerging Technologies, 36, 18
25.

pressings were used, each with the addition of w 5 5% of water, whereas it was 98.25% when just the third pressing was used with the addition of w 5 10% of water. With liming, sucrose content in the pulp that remained after four pressing stages was just 0.23% to the mass of the beets. The dry matter of the last pulp was 39%. Expressed juice obtained from electroporated cossettes had higher content of soluble solids (18% instead of 14.5%  Brix), was more pure (93.16% instead of 91.62%), less colorated (2619 instead of 9842 ICUMSA units), contained lower quantity of colloids (9.94 instead of 17.66 mg/g of soluble matter), and lower quantity of proteins (0.92 instead of 2.08 mg/g of soluble matter) in comparison to the diffusion juice obtained conventionally (Almohammed et al., 2015). Filtration properties of the juice of the first saturation were significantly improved when expression from electroporated cossettes was done with lime addition (Almohammed et al., 2017). The purity of the obtained juice was higher, and its coloration was lower than for the juice obtained by conventional sugar beet technology. Due to the very high quality of raw juice obtained from electroporated cossettes by cold pressing, alternative membrane purification of the juice was also

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Green Food Processing Techniques

97

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Coloration (IU)

Purity, P (%)

proposed (Mhemdi et al., 2014). Clarified juice was subjected to the dead-end membrane filtration at the ambient temperature. The polyethersulfone membranes with pore sizes of 10, 30, 50, and 100 kDa were used. Fig. 15.10 shows that the ultrafiltrated juice obtained by cold pressing from electroporated cossettes had a very good quality (purity  96% and lower coloration). Therefore the new cold PEF 1 pressing sugar beet technology avoids thermal degradation of sugar beet tissue and decreases consequent release of pectin, proteins, and colorants into the juice. Sugar beet juice, which is less contaminated by impurities, can be better purified using lower quantity of lime and producing lower quantity of environment-polluting wastes (filter cakes). Moreover, sugar beet tissue preserved from thermal degradation conserves bigger quantity of valuable compounds (e.g., pectins, proteins), which can be later valorized in biorefinery applications. Important advantage of a new cold pressing technology is avoiding of water addition during extraction and excluding consequent juice dilution. In conventional sugar beet technology, hot water is used as a solvent in a quantity of about 30% to the mass of sugar beets (Der Poel et al., 1998). This water should be then

Coloration 500

93

92

0 20°C (PEF)

80°C

Temperature, T (°C) Figure 15.10 Purity and color of ultrafiltrated juices obtained by pressing of electroporated (E 5 600 V/cm, tPEF 5 7 ms) and thermally treated (80 C) cossettes. In these experiments the PES membranes with pore sizes of 10, 30, 50, and 100 kDa were used. PES, Polyethersulfone. Source: Adapted from Mhemdi, H., Bals, O., Grimi, N., & Vorobiev, E. (2014). Alternative pressing/ultrafiltration process for sugar beet valorization: Impact of pulsed electric field and cossettes preheating on the qualitative characteristics of juices. Food and Bioprocess Technology, 7(3), 795
805.

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evaporated consuming very important quantity of energy. In pressing technology, cellular juice remains more concentrated than diffusion juice in conventional technology, which decreases energy consumption on evaporation station (Almohammed et al., 2017).

15.3.2.2 Selective extraction of valuable compounds in juice and wine processing Both solutes flux and extraction selectivity depend on the number and size of pores created electrically in cell membranes, as well as the size and physical properties of target molecules which should be extracted, and also on the retention capacity of the cell wall network. Fig. 15.11 presents the characteristics of juices during expression from carrot and apple slices (Vorobiev & Lebovka, 2008). Immediately after the PEF application, juice yield is importantly increased due to the membrane electroporation of carrot and apple tissue. However, the electroporation is accompanied by the decrease of juice absorbance indicating higher clarity of expressed juices. Such effect was also detected for many different food materials, for example, sugar beets, red beets, grapes, apples, mushrooms, potatoes, chicories, etc. (Fincan, 2017; ´ lvarez, & Raso, 2013; Miklavcic, 2017; Pue´rtolas, Saldan˜a, & Raso, Luengo, A 2017), demonstrating also higher purity, lower turbidity, and selective recovery of ´ lvarez, & Raso, 2016; different cell compounds using PEF (Luengo, Martı´nez, A Pataro et al., 2017). Smaller cell molecules (e.g., sugars and polyphenols) penetrate

Figure 15.11 Yield, absorbance, and  Brix of juices during extraction from carrot (A) and apple (B) slices under the pressure of 5 bars. Arrows show the moment of PEF application (E 5 350 V/cm, tPEF 5 40 ms). PEF, Pulsed electric field. Source: Adapted from Vorobiev, E., & Lebovka, N. (2008). Pulsed Electric Field Induced Effects in Plant Tissues: Fundamental Aspects and Perspectives of Application. In: E. Vorobiev & N. Lebovka (Eds.), Electrotechnologies for Extraction from Food Plants and Biomaterials (pp. 39
82). Springer.

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easily through the cell matrix, which is less damaged by electroporation than by thermal or mechanical treatments. Juice and wine processing may have important benefits using PEF treatments. In cider production, apples after washing and grinding are subjected to pressing. The juice yield obtained with single-staged pressing is often insufficient, and the apple pulp should be additionally pressed to increase the process efficiency. Some research studies showed enhanced juice yield after the treatment of apple mash by PEF both on pilot (280 kg/h) and industrial (4.4 tons/h) scale (Turk, Billaud, Vorobiev, & Baron, 2012; Turk, Vorobiev, & Baron, 2012). Fig. 15.12 presents the juice extraction line with belt filter press (A) and the juice yield (B) obtained from the Bedan’s apple cider variety in the pilot trials (280 kg/h) with and without PEF treatment (Turk, Billaud, Vorobiev, & Baron, 2012). Experimental scheme of the juice extraction line included apple washing, grinding, mash pumping, mash treatment by PEF, and juice extraction on a single belt press with four rollers (Fig. 15.12A). The total juice yield was increased on about 4% by PEF, which may permit excluding secondary pressing stage (Fig. 15.12B). Moreover, a significant difference of color was detected between control and treated juices. The color of the treated juice was the most appreciated among the sensorial panel comparing to the control. The overall chemical composition of treated juices was not different comparing to their respective controls. The pilot trials of apple and carrot juices production (50
250 kg/h) from mashes treated by PEF (colinear chamber, average electric field strength 3 kV/cm) following dejuicing have been realized (Jaeger, Schulz, Lu, & Knorr, 2012). In these experiments for juice production the belt press, rack-and-cloth press, hydraulic filter press, and decanter were used. An increase of juice yield after PEF treatment was found for apple mash in the range of 0%
11% and for carrot mash in the range of 8%
31%, depending on mash structure and dejuicing system. Grape mash can be effectively treated by PEF for the production of white and red wines. For example, for white wine production, pressing is gently applied with pressure maximum of 1.25
2 bar and pressing duration about 1.5
2 h (Jackson, 2008). Rapid pressure increase can produce turbid juice with high quantity of suspended solids, which can induce undesirable enzyme-catalyzed oxidation and hydrogen sulfide production. To avoid it the pressure should be progressively increased at the initial stage of pressing. However, juice expression yield is rather small when low pressure is applied at the initial pressing stage. The PEF application (E 5 400 V/cm, tPEF 5 0.1 s) allowed the decreasing of the applied pressure and time needed for the pressing of Chardonnay grape (Grimi, Lebovka, Vorobiev, & Vaxelaire, 2009). At a constant pressure, noticeable increase of press cake deformation defined as ε 5 1 2 h/hi (h and hi are the current and the initial height of the sample, respectively) was observed (Fig. 15.13). Consequently, the juice yield was increased, especially at the lower pressure of 0.5 bar (Grimi, Lebovka, Vorobiev, & Vaxelaire J. 2009). Statistical analysis showed no significant effect of PEF treatment on turbidity and content of polyphenols for the constant pressure regime. However, PEF treatment application resulted in the elevation of the content of polyphenols (more than

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Apple 73.6 69.5

70 62.1

64.5

Untreated

PEF

Juice yield, Y (%)

60 50 40 30 20 10 0

7.3

Juice 1

9.0

Juice 2

Juice 3

Figure 15.12 (A) Experimental scheme of the juice extraction line. The line includes apple washing (1), grinding (2), mash pumping (3), mash treatment by PEF (4), and juice extraction on a single belt press with four rollers (5). (B): Extraction yield of juices collected under the first roller (juice 1) and the three next rollers (juice 2). Total juice yield was the sum of both juices 1 and 2. Control sample (E 5 0 V/cm; black bars) and treated sample (E 5 1000 V/cm; white bars) were compared for each category of juice. PEF, Pulsed electric field. Source: Adapted from Turk, M. F., Billaud, C., Vorobiev, E., & Baron, A. (2012). Continuous pulsed electric field treatment of French cider apple and juice expression on the pilot scale belt press. Innovative Food Science & Emerging Technologies, 14, 61
69.

420

Green Food Processing Techniques

0.7

Chardonnay grape

Press-cake deformation, ε

0.6 0.5 0.4 0.3 Pressure, bar

0.2

0.5 1

0.1 0 0 10

10

1

2 10 Time, t(s)

10

3

Untreated PEF

10

4

Figure 15.13 Press cake deformation ε versus time for pressing at constant pressures P 5 0.5 bar and P 5 1.0 bar with (solid lines) and without (dashed lines) PEF treatment. PEF, Pulsed electric field. Source: Adapted from Grimi, N., Lebovka, N., Vorobiev, E., & Vaxelaire, J. (2009). Effect of a Pulsed Electric Field Treatment on Expression Behavior and Juice Quality of Chardonnay Grape. Food Biophysics, n 4(3), 191
198.

15%) for the progressive pressure increase regime. Red wines rich by polyphenols are highly appreciated. Compared to other techniques employed to enhance phenolic diffusion (thermovinification), PEF process is of great interest (El Darra, Grimi, Maroun, Louka, & Vorobiev, 2013). PEF treatment influences aroma composition and could have a major impact on the final aroma and style of wine. Fig. 15.14 shows anthocyanin (A) and tannins (B) content in the wines obtained after the PEF treatment of Cabernet sauvignon grapes (Delsart et al., 2014). The color intensity of the musts freshly treated by PEF at 4 (1 ms) and 0.7 kV/cm (200 ms) was 86% and 168%, respectively, higher than that of the control must. The hyperchromic effect was explained by the enhanced extraction of anthocyanins at the beginning of the fermentation process (Delsart et al., 2014). After bottling (day 205) the color intensity of the wines obtained with the application of PEF at E 5 0.7 kV/cm (tPEF 5 200 ms) and E 5 4 kV/cm (tPEF 5 1 ms) was higher (26% and 13%, respectively) than in the control wine. The anthocyanins and tannins are extracted more intensely and more rapidly with PEF treatment than is the case with traditional maceration (Fig. 15.14). Numerous studies on the laboratory, pilot-scale, and industrial levels confirm improvements of winemaking with PEF (see, for example, Pue´rtolas, Herna´ndez´ lvarez, & Raso, 2010; Sack et al., 2010; Sack et al., 2010). Orte, Sladan˜a, A

(A)

600

Anthocyanin

Content, C (mg/L)

550

500

450

400

(B) 4.0

Control

E = 0.7 kV/cm tPEF = 200 ms

Cabernet sauvignon grape

4 kV/cm 1 ms

Tannins

3.5

Content, C (mg/L) c

3.0 2.5 2.0 1.5 1.0 0.5 0.5

Control

E = 0.7 kV/cm tPEF = 200 ms

4 kV/cm 1 ms

Figure 15.14 Content of anthocyanin (A) and tannins (B) in the wines (at 3 months after bottling) obtained from untreated (0 kV/cm) and PEF-treated Cabernet sauvignon grapes (E 5 0.7 kV/cm for tPEF 5 200 ms and E 5 4 kV/cm for tPEF 5 1 ms). Insert shows the photos of musts immediately after treatments. PEF, Pulsed electric field. Source: Adapted from Delsart, C., Cholet, C., Ghidossi, R., Grimi, N., Gontier, E., Ge´ny, L., et al. (2014). Effects of pulsed electric fields on Cabernet Sauvignon grape berries and on the characteristics of wines. Food and Bioprocess Technology, 7(2), 424
436.

422

Green Food Processing Techniques

15.3.2.3 Preserving of food quality by dehydration, freezing, and stress/inactivation PEF can be useful in food preservation processes such as drying, freezing, and inactivation of microorganisms. Drying is commonly used to remove moisture, inhibit microbial development in foods, and preserve products stability. However, drying is highly energy consumable process. Moreover, excessive heating during drying leads to the losses of vitamins and aromas and degradation of food structure and quality. Positive impacts of PEF on convective air drying, vacuum and freeze-drying of different foods have been reported (Ben Ammar, Lanoiselle, Lebovka, Van Hecke, & Vorobiev, 2010; Jalte, Lanoiselle´, Lebovka, & Vorobiev, 2009; Lebovka, Shynkaryk, & Vorobiev, 2007; Phoon, Galindo, Vicente, & Dejmek, 2008; Vorobiev & Lebovka, 2011; Wiktor, Schulz, Voigt, Witrowa-Rajchert, & Knorr, 2015; Wu & Zhang, 2014). Electroporation of cell membranes leads to the water release from interior of cells. Then humidity can be easily removed during drying. Fig. 15.15 presents Arrhenius plot of the vacuum drying time (td) required to attain the same actual (W) to initial (Wi) moisture ratio W/Wi 5 0.2 for untreated

Drying temperature, Td (oC) 70

60

50

40

5000 4500

8.4

Potato

8.2 3500

3000

8

2500

7.8

2000 0.0029

lntd

Drying time, td (s)

4000

7.6 0.003

0.0031

0.0032 –1

Inverse drying temperature, 1/Td (K ) Figure 15.15 Temperature dependencies of the time td required to attain the moisture ratio of W/Wi 5 0.2, for untreated (filled squares) and PEF-treated (open squares) potato tissues. The dashed line corresponds to the activation energy of 28 kJ/mol. PEF, Pulsed electric field. Source: Adapted from Liu, C., Grimi, N., Lebovka, N., & Vorobiev, E. (2018). Effects of pulsed electric fields treatment on vacuum drying of potato tissue. Lebensmittel-Wissenschaft & Technologie, 95, 289
294.

Pulsed electric field in green processing and preservation of food products

423

and PEF-treated (E 5 600 V/cm, tPEF 5 0.1 s) potato samples (Liu, Grimi, Lebovka, & Vorobiev, 2018). The vacuum drying was done at pressure p 5 30 kPa that corresponds to the boiling point of water of about 70 C. The drying time td decreased with the increase of drying temperature Td, and the PEF treatment allowed noticeable decreasing of td (by 22%
27% at Td 5 40 C
70 C). The dashed line corresponds to the activation energy of 28 kJ/mole. It follows from Fig. 15.15 that for the same drying time td  2800 s, the drying temperature can be decreased from 70 C for the untreated potato sample to about 47 C for the PEF-treated potato sample. It gives important benefits not just for energy saving due to the drying at lower temperature but also for the better quality preservation of potato tissue. For traditional thermal convective air drying the decreasing of drying time or drying temperature was also demonstrated for red beet (Shynkaryk, Lebovka, & Vorobiev, 2008) and other food plants (Ostermeier, Giersemehl, Siemer, To¨pfl, & J¨ager, 2018; Wiktor et al., 2016). Freeze-drying is also widely used in the processing of different food products. It allows processing with low energy consumption and in high-quality food products. Application of PEF accelerates the product cooling and leads to a higher drying rate (Parniakov, Bals, Lebovka, & Vorobiev, 2016). Fig. 15.16 shows drying curves for the intact (cell disintegration index Zc 5 0) and PEF-treated (E 5 800 V/cm, Zc 5 0.46 and 0.96) apple samples in the 1

(A)

Apples

(B)

Moisture contents (wet basis), W

0.8

Zc = 0 0.49 0.96

0.6 0.4 0.2

W = 0.1 0

50

100

150

200

250

Drying time, t (min) 1 0.8 0.6 0.4 0.2

W = 0.1 0

0

0.002

0.004

0.006

–dW*/dt Figure 15.16 Moisture content (wet basis), W, versus the time, t (A), and W versus 2 dW/dt (B) for untreated (Z 5 0) and PEF pretreated (E 5 800 V/cm, Zc 5 0.46 and 0.96) apple samples. PEF, Pulsed electric field. Source: Adapted from Parniakov, O., Bals, O., Lebovka, N., & Vorobiev, E. (2016). Pulsed electric field assisted vacuum freeze-drying of apple tissue. Innovative Food Science & Emerging Technologies, 35, 52
57.

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Green Food Processing Techniques

Figure 15.17 Macroscopic (A) and microscopic (B) pictures of untreated (Z 5 0) and PEF pretreated (E 5 800 V/cm, Z 5 0.96) apple samples after vacuum freeze-drying. The initial samples before drying had diameter of di 5 2.9 mm and thickness of hi 5 5 mm. PEF, Pulsed electric field. Source: Adapted from Parniakov, O., Bals, O., Lebovka, N., & Vorobiev, E. (2016). Pulsed electric field assisted vacuum freeze-drying of apple tissue. Innovative Food Science & Emerging Technologies, 35, 52
57.

coordinates of moisture content (wet basis), W, versus the time, t (A), and W versus 2 dW/dt (B) for the same sets of data. For the PEF-treated apple samples the moisture content falls more rapidly than that for the untreated ones (Fig. 15.16). The PEF treatment also accelerated the drying rate. Consequently, the freeze-drying duration is considerably shorter with PEF treatment. Fig. 15.17 presents the macroscopic (A) and microscopic (B) pictures of untreated (Zc 5 0) and PEF pretreated (E 5 800 V/cm, Zc 5 0.96) freeze-dried apple samples. The PEF treatment (E 5 800 V/cm, Zc 5 0.96) applied before vacuum freeze-drying results in better preservation of the sample shape and shrinking inhibition (Parniakov et al., 2016). Other studies confirm better product quality and lower samples shrinking for PEF accompanied freeze-drying. For instance, PEF pretreatment decreased the drying time and resulted in more uniform shape, clear colors, smaller shrinkage, smaller browning level, and visually better quality of the dried potato samples (Jalte et al., 2009).

Pulsed electric field in green processing and preservation of food products

425

(B)

Concentration of viable cells, Nv (CFU/mL)

(A)

10 5 E, V/cm 20 100 1000 2000

10 4 10 2

10 4

10 6

PEF treatment time, tPEF (µs) 10 5 “Saturated”

10 4

“Logarithmic”

Inactivation Electro-stimulation

10 –6

10 –4

10 –2

10 0

10 2

Specific energy consumption, W (J/mL) Figure 15.18 Concentration of viable cells Nv (CFU per mL) versus the time of PEF treatment tPEF (A) and specific energy consumption W (B) for Saccharomyces cerevisiae cells in a synthetic fermentation medium. Electric field strengths were varied (E 5 0
2000 V/cm) and preliminary fermentation stage was fixed at tf 5 24 h. PEF, Pulsed electric field. Source: Adapted from Mattar, J. R., Turk, M. F., Nonus, M., Lebovka, N. I., El Zakhem, H., & Vorobiev, E. (2014). Stimulation of Saccharomyces cerevisiae cultures by pulsed electric fields. Food and Bioprocess Technology, 7(11), 3328
3335.

Effects of PEF in liquid foods and biosuspensions include electroporation of cell membranes, electrostimulation of cellular metabolisms, different bioreactions, electro-fusion of cells, enhanced extraction of intracellular components, and stress or inactivation of microorganisms. Fig. 15.18 shows the curves of the concentration of viable cells Nv [in colonyforming unit (CFU) per ML] versus PEF treatment time tPEF (A) and specific energy consumption W (B) for Saccharomyces cerevisiae cells in a synthetic fermentation medium (Mattar et al., 2014). Different electric field strengths (E 5 0
2000 V/cm) were used, and preliminary fermentation stage was fixed at tf 5 24 h. The data evidenced strong impact of PEF treatment on the grown ability of yeast. It is important to note that electrostimulation was only energy dependent, so all Nv versus W dependencies were falling into the same master curve at different values of E within 20 and 2000 V/cm (Fig. 15.18B). The colony growth was saturated within the range of 1021 J/mL , W , 101 J/mL, and the value of Nv decreased at stronger PEF treatment with tPEF 5 106 μs and E 5 2000 V/cm, which reflects the inactivation or killing of yeast due to the electroporation phenomenon. Fig. 15.18 also demonstrates the interest of low PEF treatment for the enhancement of fermentation processes. However, this promising topic was almost unexplored yet in the

426

Green Food Processing Techniques

literature. On the contrary the topic concerning inactivation of microorganisms in liquid foods (juices, milk, wines, etc.) at high PEF was widely studied and referenced. We will not discuss this subject, to learn it the reader can see the well-known book (Barbosa-Ca´novas et al., 1998) and numerous reviews (e.g., Espachs-Barroso, Barbosa-Ca´novas, & Martı´n-Belloso, 2003; Miklavcic, 2017; Mosqueda-Melgar, Elez-Martinez, Raybaudi-Massilia, & Martin-Belloso, ´ lvarez, Condo´n, & Raso, 2014). 2008; Saldan˜a, A

15.4

Conclusion

This chapter shortly reviews different examples of food processing with PEF. The significance of PEF-assisted green processing and preservation of food products has become increasingly recognized over the past decades. The PEF treatment of biological objects offers new ways to regulate the efficiency extraction, drying, freezing, osmotic, and fermentation processes as well as inactivation of pathogenic bacteria. At the present time the understanding of underlying mechanisms of PEF action on foods and effective integration of PEF techniques into the different existing food processing (upstream and downstream) has a high priority in the field.

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1296. Wiktor, A., Schulz, M., Voigt, E., Witrowa-Rajchert, D., & Knorr, D. (2015). The effect of pulsed electric field treatment on immersion freezing, thawing and selected properties of apple tissue. Journal of Food Engineering, 146, 8
16. Wu, Y., & Zhang, D. (2014). Effect of pulsed electric field on freeze-drying of potato tissue. International Journal of Food Engineering, 10(4), 857
862. Zimmermann, U. (1986). Electrical breakdown, electropermeabilization and electrofusion, . Reviews of physiology, biochemistry and pharmacology (Vol. 105, pp. 175
256). Berlin, Heidelberg: Springer Berlin Heidelberg. Available from https://doi.org/10.1007/ BFb0034499.

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N.N. Misra1 and M.S. Roopesh2 1 Department of Food Science & Human Nutrition, Iowa State University, Ames, IA, United States, 2Department of Agricultural, Food & Nutritional Science, University of Alberta, Edmonton, AB, Canada

16.1

Introduction

The world should produce and process enough food to feed approximately 10 billion people by 2050. The agri-food manufacturing sector should be ready for this task in the time of climate change and diminishing arable land. Sustainable food production and processing has become increasingly important recently than any other time. Reducing the foodborne illnesses, food recalls, and food safety
related incidents will improve the sustainability of the whole food systems. According to the World Health Organization (2015), 600 million foodborne illnesses by hazards, including foodborne pathogens, caused 420,000 deaths globally in 2010. According to United States Department of Agriculture (2014), foodborne illnesses cost more than $15.6 billion annually to the United States alone. Traditional technologies such as thermal treatments are effective in improving food safety; however, they can be highly energy intensive and can cause significant quality changes in foods. The agri-food industry looks to improve sustainability by reducing the water and energy use, food waste, during food production and processing, and foodborne illnesses postproduction. Further, the agri-food industry is more willing to accept new technologies than ever as many of these are nonthermal, resulting in minimal quality changes in food products. Effective but energy-efficient and advanced green technologies offer more sustainable solutions to food industry. Among the green, sustainable, and nonthermal food processing technologies to improve food safety and reduce food recalls due to the occurrence of pathogenic microorganisms, cold plasma is becoming highly popular. Cold plasma is the highly energized state of a gas at relatively low temperature (close to room temperature) and atmospheric pressure. The use of cold plasma at atmospheric pressure and low temperature helps to develop its sustainable applications in food production and processing. Providing electrical energy at room temperature and atmospheric pressure to a gas can create plasma with a large number of reactive components. They interact with microorganisms and food biomolecules, leading to their inactivation or changes in their structural and functional properties.

Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00016-1 © 2019 Elsevier Inc. All rights reserved.

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These reactive components are short lived, hence no residue exists after the cold plasma treatment, and hence, it can be considered as a green and sustainable technology. Other advantages include its flexibility to use for a variety of products, reduced treatment times which leads to energy efficiency, and limited quality changes while ensuring food safety (Bourke, Ziuzina, Boehm, Cullen, & Keener, 2018). Cold plasma is finding niche applications in agriculture and food sector, including seed germination enhancement (Dobrin, Magureanu, Mandache, & Ionita, 2015; Randeniya & de Groot, 2015), plant growth enhancement (Randeniya & de Groot, 2015; Sivachandiran & Khacef, 2017), water treatment (Sarangapani, Danaher et al., 2017; Sarangapani et al., 2016), soil decontamination (Stryczewska, Ebihara, Takayama, Gyoutoku, & Tachibana, 2005; Zhang, Ma, Qiu, Tang, & Du, 2017), decontamination of food and biomaterials (Misra, Pankaj, Frias, Keener, & Cullen, 2015), decontamination of processing equipment (Leipold, Kusano, Hansen, & Jacobsen, 2010), inactivation of enzymes (Misra, Pankaj, Segat, & Ishikawa, 2016; Pankaj, Misra, & Cullen, 2013; Segat, Misra, Cullen, & Innocente, 2016), food property modification (Misra, Kaur, et al., 2015; Misra, Yong, Phalak, & Jo, 2018; Pal et al., 2016; Segat, Misra, Cullen, & Innocente, 2015; Segat et al., 2014), and food packaging property modification (Pankaj et al., 2014a, 2015a, 2015b, 2017; Pankaj, Bueno-Ferrer, Misra, O’Neill, Tiwari, et al., 2014). Published research articles on cold plasma technology for agricultural applications increased significantly but linearly from 2010 to 2016 from approximately 1600 to around 2700 (Ito et al., 2018). Previous and current research demonstrates potential of cold plasma technology in the abovementioned applications in different areas of agricultural and food production and processing. Agricultural and food raw materials and products are often processed in bulk. One of the main challenges of the industrial development of cold plasma technology is the appropriate selection of plasma source for large volume processing of agricultural and food materials. Several plasma sources such as corona, dielectric barrier discharge (DBD), microwave, and radio frequency (RF) have been used to generate plasma. Further, important parameters determining the efficacy of cold plasma technology in these applications should be well understood, in order to optimize the conditions to achieve maximum energy and cost-effectiveness. It would be necessary to use it at atmospheric pressure using air as the plasma-generating gas without any expensive electrical power source for cost-effective application of cold plasma technology (Ito et al., 2017). Investigations to address the chemical and biological changes in food macromolecules leading to any potential toxicity after cold plasma treatment should be addressed before its commercial applications. Prospective scale-up and future adoption of cold plasma technology require regulatory approval from respective authorities in different countries. Further, consumer acceptance of any technology is a challenge. Cold plasma treatments could be considered “clean label,” owing to no production of residues, which may be an advantage compared to other conventional processes, which may help in its industrial adoption and consumer acceptance in the future (Bourke et al., 2018). Addressing some of the abovementioned opportunities and challenges, this chapter presents the fundamentals of cold plasma

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including plasma chemistry, antimicrobial mechanisms of plasma, and a few important applications including in-package treatment, water treatment, food production, and some details on its energy efficacy and process cost.

16.2

Cold plasma fundamentals

To understand the plasma state, let us consider a simple case of matter present inside a closed volume. Let us also assume this matter to exist in a solid state (say, as ice). Up on adding energy to this closed volume, say, in the form of heat, we will eventually melt this solid into liquid (water), and up on further addition of thermal energy, we will enter the gas phase (steam). Until this point, everything should sound familiar to average readers. The obvious question is, what happens when the gas is further energized? When a gas is energized to an extent that the atoms and molecules breakdown resulting in the formation of a sufficient number of free electrons and ions, such that the gas becomes electrically conductive; at this point, the resulting state of the matter is known as “plasma.” Thus plasma is an ionized state of a gas. To define formally, plasma refers to a partially or fully ionized state of a gas or gas mixture that comprises of free electrons, positive and negative ions, radicals, metastables, neutrals, atoms, molecules, and photons (Misra et al., 2017). While the example we chose above involved the addition of thermal energy to the gaseous state of matter, the ionization of the gas can also be achieved using strong electric fields. The example of the former approach for plasma generation is the flame torches used for welding, while the example for the latter case is the arc welding process. Note that in both these cases, the temperature of the gas will be very high (103
104K). Plasmas with such high temperatures are referred to as “thermal plasmas.” However, one could also reach a plasma state under room temperature conditions, where such a plasma would be referred to as “nonthermal plasma” or “cold plasma” or “nonequilibrium plasma.” Obviously, a cold plasma state can be achieved using electrical discharges only. In the context of cold plasma technology the term “cold” is often debated as it could be interpreted as near-zero or subzero temperatures. In fact, there is no established definition of the temperature range. That being said, it is informally agreed that plasmas with temperatures from close to ambient to under 60 C can be termed cold plasmas (Misra, Yepez, Xu, & Keener, 2019). From the perspective of physicists the term cold implies a lower temperature of the heavy species (ions, radicals, and neutrals) as compared to electrons in the ionized gas. This thermodynamic nonequilibrium between electrons and heavy species is a direct consequence of the asymmetric momentum transfer during collisions under the influence of an electrical potential difference (Misra, Martynenko, et al., 2018). During early years, cold plasmas were obtained via electrical discharges in gases held under low-pressure conditions. This is because low pressures allow to sufficiently ionize the rarefied gas molecules at relatively lower electrical potential differences. However, with advancement in the plasma science and technology,

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efficient ionization was achieved even under atmospheric pressure conditions using high-voltage, pulsed, or high-frequency power systems. Such plasmas are referred to as “atmospheric pressure plasmas.” Interestingly, the food research community has explored both low-pressure and atmospheric pressure cold plasmas for various applications. Technically, however, atmospheric pressure cold plasmas are of greater interest to the industry considering that the process would be easy to implement for continuous application, without the need for mechanical systems to maintain low pressures (Misra, Tiwari, Raghavarao, & Cullen, 2011).

16.2.1 Plasma sources Having introduced the terminology pertinent to atmospheric pressure and cold plasma electrical discharges in gases, we will now shift to discuss the various approaches to establish such discharges. The setup for an electrical discharge in gases for obtaining the plasma is referred to as a “plasma source.” Various types of plasma sources have been developed by engineers for applications in food, medical, environmental, and chemical sectors. We have provided a summary of the design, a simple schematic, and the operational principle of three common plasma sources of interest to food applications in Fig. 16.1. In addition to the plasma sources described in Fig. 16.1, another commonly employed plasma source is a plasma jet, where two concentric electrodes are

Figure 16.1 Plasma sources, their design, and operational principle, with a schematic.

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arranged such that a gas (or gas mixture) can be flown through the interannular region (Schutze et al., 1998). The inner metallic electrode is subjected to a high voltage (B102 V) using a high-frequency power source (B13.56 MHz, RF), resulting in gas ionization. The ionized gas (plasma) exits through the nozzle and is directed on to the food to be treated. Note that the plasma jet is essentially a geometric modification of the barrier discharge. Yet another plasma source reported in literature is the photoionization plasma which involves subjecting the gas to highenergy deep ultraviolet light with an effective radiation spectrum between 180 and 270 nm. This approach has been commercialized by BioZone Scientific (BioZone Scientific International, Florida). A detailed discussion of the design of plasma sources, a complex topic, is beyond the scope of this chapter. In general the plasma source design and type is largely dictated by the type of application. The design of plasma sources for biological applications is invariably aimed at achieving specific plasma chemistries—the type of species, their number density, and kinetics. Therefore we will present a discussion of the plasma chemistry in the next section.

16.2.2 Plasma chemistry The reaction mechanisms resulting in the formation of active plasma chemical species include electronic impact processes (vibration, excitation, dissociation, attachment, and ionization), ion
ion neutralization, ion
molecule reactions, Penning ionization, quenching, three-body neutral recombination, and neutral chemistry, besides photoemission, photoabsorption, and photoionization. In gas mixtures containing oxygen and nitrogen, these result in the formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The ROS and RNS generated in humid air plasma are well-known antimicrobial agents. Examples of ROS species in plasma include hydrogen peroxide (H2O2), ozone (O3), superoxide anion (O2 2 ), hydroperoxyl (HO2 ), alkoxyl (RO ), peroxyl (ROO ), singlet oxygen (1O2), hydroxyl radical ( OH), and carbonate anion radical (CO2 3 ). Examples of RNS in plasma include nitric oxide (NO ), nitrogen dioxide radical ( NO2), peroxynitrite (ONOO2), peroxynitrous acid (OONOH), and alkyl peroxynitrite (ROONO) (Arjunan, Sharma, & Ptasinska, 2015). A list of known reactions that result in the formation of such species of antimicrobial significance is summarized in Table 16.1. The experimental methods commonly employed for identification and quantification of the plasma chemical species include the use of chemical methods (e.g., shortterm gaseous species detection tubes), optical emission spectroscopy (Arago´n & Aguilera, 2008), optical absorption spectroscopy (in the ultraviolet, visible, and infrared regions) (Moiseev et al., 2014), and laser-induced fluorescence (Niemi, Gathen, & Do¨bele, 2005). The reactions resulting in the formation of the reactive species occur over a broad range of timescales (nanoseconds, microseconds, milliseconds, seconds, hours) and length scales (from molecular scales to characteristic length scales of the plasma reactor). Thus the study of plasma chemistry via experimental methods is a very complex task and often requires the use of computer simulations for kinetic studies (Gaens & Bogaerts, 2013; Park, Choe, & Jo, 2018). K

K

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Table 16.1 List of major ground state species and some atomic oxygen species of antimicrobial relevance formed in nonequilibrium low-temperature humid air plasma (Herron & Green, 2001). O reactions

N reactions

O 1 O3!O2 1 O2 O 1 NO2!O2 1 NO O 1 NO3!O2 1 NO2 O 1 N2O5!Products O 1 HN!H 1 NO O 1 HO!O2 1 H O 1 HO2!O2 1 HO O 1 H2O2!HO2 1 HO O 1 HNO!NO 1 HO O 1 HONO!NO2 1 HO O 1 HONO2!Products O 1 HO2NO2!Products

N 1 O2!NO 1 O N 1 O3!NO 1 O2 N 1 NO!N2 1 O N 1 NO2!N2O 1 O N 1 NO3!NO 1 NO2 N 1 HN!H 1 N2 N 1 HO!NO 1 H N 1 HO2!NO 1 HO

H reactions

NOx reactions

H 1 HN!N 1 H2 H 1 O3!HO 1 O2 H 1 HO2!HO 1 HO H 1 HNO!H2 1 NO H 1 HONO!H2 1 NO2 H 1 NO2!HO 1 NO

NO 1 O3!NO2 1 O2 NO 1 NO3!2NO2 NO 1 HO2!HO 1 NO2 NO 1 HNO!HO 1 N2O NO2 1 O3!NO3 1 O2

HOx reactions

HNx reactions

HO 1 H2!H2O 1 H HO 1 O3!HO2 1 O2 HO 1 HO!H2O 1 O HO 1 HO2!H2O 1 O2 HO 1 H2O2!HO2 1 H2O HO 1 HNO!NO 1 H2O HO 1 HONO!NO2 1 H2O HO 1 HONO2!NO3 1 H2O HO 1 NO3!HO2 1 NO2 HO 1 N2O5!Products HO 1 HO2NO2!Products HO2 1 HO2!H2O2 1 H2O HO2 1 O3!HO 1 2O2 HO2 1 NO3!O2 1 NO2 1 HO HNO 1 NO2!HONO 1 NO NO2 1 NO3!NO 1 NO2 1 O2 NO3 1 NO3!2NO2 1 O2 NO3 1 O2!Products N2O5 1 H2O!2HONO2

HN 1 NO!H 1 N2O HN 1 NO2!products HN 1 O2!HO 1 NO HN 1 HO!NO 1 H2 HN 1 HO2!products Major atomic oxygen reactions H2 1 O!H 1 OH CH4 1 O!CH3 1 OH H2O 1 O!2OH O2 1 O!O3 CO 1 O!CO2

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The power input to the discharge, working gas, and mode of operation of the plasma source has a major impact on the species that are formed and their extent of formation.

16.3

Antimicrobial action of plasma species

In Fig. 16.2 a graphical summary of the mechanisms responsible for cold plasma
led inactivation of bacterial cells is provided. The plasma source shown represents a DBD-based plasma jet. A plasma source has two distinct modes of

Figure 16.2 A pictorial summary of the mechanism of cold plasma
induced bacterial cell damage. Source: Adapted from Misra, N. N., & Jo, C. (2017). Applications of cold plasma technology for microbiological safety in meat industry. Trends in Food Science & Technology, 64, 74
86.

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application: (1) the direct treatment of the food using the active region of the glow and (2) the indirect treatment using the remote region of the plasma glow. When the food is subjected to the direct plasma treatments, the food as well as any bacterial cells harbored are exposed to very strong electric fields, very short lifetime (quasistable) species, as well as the radicals, positive and negative ions of the plasma. However, on the indirect treatment of the food the strength of the electric field is much lower, and the quasistable species recombine. The ROS generated in plasma are detrimental to the functionality of cellular biomolecules in a bacterium, including DNA, proteins, and enzymes. The ROS are capable of hampering the functionality of bacterial membranes by acting on the lipids to result in the formation of unsaturated fatty acid peroxides and oxidized amino acids in proteins (Misra et al., 2016). Experiments have revealed that exposure of bacterial cells to intense electric fields causes cell membrane rupturing due to the electrostatic tension experienced from the high electrical charge developed (Laroussi, Mendis, & Rosenberg, 2003). Cold plasma could also destroy the outer membrane of bacterium, and this aspect has been confirmed through experiments (Sun, Qiu, Nie, & Wang, 2007) as well as computer simulations (Yusupov et al., 2012, 2013). The computer simulations have suggested that the ROS break the C
O, C
N, and C
C bonds of the peptidoglycan molecule of the Gram-positive bacterial cell wall. In the case of Gram-negative bacteria, it has been reported that the lipopolysaccharides are chemically modified on exposure to argon plasma (Bartis, Graves, Seog, & Oehrlein, 2013). The change in morphology of bacterial cells or their lysis under the influence of cold plasma has also been imaged via electron microscopy (Ziuzina, Patil, Cullen, Keener, & Bourke, 2013). The end result of such a broad scale of action on the bacterial cell organelles is the cell leakage and loss of functionality. It is worthwhile mentioning that the type and extent of effects on the bacterial cell are governed by the type of plasma source, the process parameters, the gas used, the food product/substrate, and finally the type of bacteria (or microorganism, in general). While we elaborated upon the action of cold plasma on bacterial cells, it has been widely confirmed in literature to be active against yeasts, molds (Hashizume et al., 2013, 2014; Iseki et al., 2011; Ishikawa & Hori, 2014), viruses (Ahlfeld et al., 2015; Lacombe et al., 2017; Min et al., 2016), bacterial spores (Patil et al., 2014; van Bokhorst-van de Veen et al., 2015), and biofilms (Gabriel et al., 2016; Puligundla & Mok, 2017).

16.4

In-package cold plasma: a dry, green, and resource-efficient process

An interesting development in the cold plasma applications to foods is the inpackage cold plasma technology (Misra, Keener, Bourke, & Cullen, 2015; Misra, Ziuzina, Cullen, & Keener, 2013). The sequence of events involved in an inpackage cold plasma treatment process is summarized in Fig. 16.3. The in-package

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Figure 16.3 Schematic of the processes occurring during in-package cold plasma treatment. Source: Adapted from Misra, N. N., Yepez, X., Xu, L., & Keener, K. (2019). In-package cold plasma technologies. Journal of Food Engineering, 244, 21
31.

cold plasma treatment involves sealing of food product contained in a rigid or flexible package, whose headspace is filled with ambient air or flushed with a modified atmosphere gas mixture (Misra, Moiseev, et al., 2014) (Fig. 16.3A). This rigid package is subsequently subjected to a strong electric field, which results in an electrical breakdown of the gas, creating the ionized gas environment (plasma) (Fig. 16.3B). The breakdown products, namely ROS and RNS, having high diffusion coefficients, spread out in the package and act upon the spoilage microorganisms for timescales ranging from few seconds to few hours (Fig. 16.3C). However, the ROS and RNS being unstable, the residual (unreacted) species recombine and/ or extinguish to form the original gas (Fig. 16.3D). Thus toward the end of the process, one ends with the same gas composition as the one starts with, while successfully reducing the microbial population on the contained food. There are several advantages of the in-package cold plasma process. Cold plasma does not necessitate the use of large quantities of water as is conventionally used in the fresh produce or meat industry. However, it has been recommended that cold plasma be used for fresh produce and meat after a washing step to increase its efficacy (Misra & Jo, 2017; Misra et al., 2016). It is to be recalled that the food processing industry is one of the most water-intensive industries coming after the chemical and the refinery industries. Furthermore, the food and beverage industry has the highest contribution to the emissions of organic water pollutants. Between 10% and 30% of the total industrial emissions of organic water pollutants comes from the food and beverage industry in high-income countries. Cold plasma has so far been not reported to leave any toxic residues (as has been suggested for chlorine or other chemical wash). This is because the reactive species are in the gaseous phase, and being unstable, recombine to form the original gas. The fresh-cut industry is heavily dependent on chlorine as an effective sanitizer to assure the safety of its produce. However, in light of concerns about its efficacy, as well as about the environmental and health risks associated with the formation of carcinogenic halogenated disinfection by-products, there is increasing pressure on the industry to eliminate chlorine from the disinfection process. Moreover, the use of chlorine for the disinfection of fresh produce is banned in some countries including Germany and Switzerland. Recontamination of the washed produce by pathogens such as Listeria monocytogenes poses a risk even after washing with chlorine,

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as they multiply faster on cleaned produce. Cold plasma technology offers a potential increase in producing shelf life, thereby allows to reduce the amount of waste generated and facilitates market expansion. Cold plasma is not only effective against microorganisms but also mitigates the menace of pesticide residues in foods, for example, the efficacy of cold plasma in degrading pesticide residues on strawberries (Misra, Pankaj, et al., 2014), blueberries (Sarangapani, O’Toole, Cullen, & Bourke, 2017), cucumber (Dorraki, Mahdavi, Ghomi, & Ghasempour, 2016), and goji berry (Zhou et al., 2018) has been reported in literature. Not only pesticides but the degradation efficacy of cold plasma against mycotoxins in food grains has also been reported by several researchers (Misra, Yadav, Syamaladevi, & Jo, 2019; Shi, Cooper, Stroshine, Ileleji, & Keener, 2017; Shi, Ileleji, Stroshine, Keener, & Jensen, 2017). Within the grain industry, though less explored, the potential for elimination of toxic fumigants (e.g., phosphene) for insecticidal or insect control measures also exists. Gas phase plasma application using a jet has been shown to effectively kill Indian meal moth (Plodia interpunctella) (Abd El-Aziz, Mahmoud, & Elaragi, 2014). The effectiveness of cold plasma against Tribolium castaneum (Herbst) in wheat flour was recently studied, and a 100% mortality was reported (Ratish Ramanan, Sarumathi, & Mahendran, 2018). Water activated using cold plasma has been shown to be effective against mealybugs (Ten Bosch, Kohler, Ortmann, Wieneke, & Viol, 2017). Finally, it is interesting to note that cold plasma has been employed as an alternative to hydrogen peroxide and ethylene oxide for the decontamination of packaging materials (Lee, Puligundla, & Mok, 2017; Pankaj, Bueno-Ferrer, Misra, Milosavljevi´c, et al., 2014; Yong et al., 2017) as well as their surface property modification (Pankaj et al., 2014b, 2015a, 2015b). Thus in-package cold plasma could allow to decontaminate the food as well as the packaging material in a singleprocess step, thereby saving time and cost for the industry.

16.5

Cold plasma for water treatment

Washing in the fresh foods industry (fresh fruits, vegetables, meat, fish, and poultry) serves several purposes, including detachment of dirt, removal of pesticide residues and adhering microbes, as well as precooling of cut produce and removal of cell exudates that could foster microbial growth. The food industry, especially the fresh-cut industry, has relied on the use of chlorine as an effective sanitizer for assuring product safety. As mentioned earlier, the industry is striving to eliminate chlorine as a disinfectant due to the concerns associated with its efficacy and the environmental and health risks associated with the possible formation of carcino¨ lmez & Kretzschmar, 2009). On the genic halogenated disinfection by-products (O one hand, it is well recognized that washing products without sanitizers will necessitate the use of large volumes of water for achieving similar degrees of microbial reduction. On the other, oftentimes wash water is a source of cross-contamination

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as reusing processing water could result in the buildup of microbial loads, including undesirable pathogens from the crop. An important challenge before the industry is the minimization of water consumption and discharge. A technology enabling efficient disinfection of the product as well as the wash water will therefore be highly welcomed. Such a technology will also promote higher recycling and reduce wastewater discharge rates. Electrical discharge plasmas have been employed for ex situ ozone production for over a century and used alone or in combination with other advanced oxidation processes (AOPs) for degrading recalcitrant pollutants in water. Several kinds of electrical discharge configurations and reactor designs have been explored for optimizing the efficiency of pollutant removal from water and wastewater (Malik, 2009; Stratton et al., 2017). The pollutant degradation efficacy of plasma is due to several reactive species and not primarily ozone, as is the case with gas phase treatments. This can be justified because the working gas in water treatment reactors is saturated with water vapors, which significantly reduces the ozone yield. Being prone to quick reaction with reactive species with negligible competition from their intermediates, redox-colored dyes are commonly employed for demonstrating water decontamination ability of newly developed or modified plasma reactors. For example, methylene blue dye has been employed as a simulant for wastewater rich in phenolics (e.g., from olive mills) for testing the efficacy of a high-voltage DBD plasma reactor (Misra, Keener, et al., 2015). The results indicated a rapid discoloration of the dye within 120 s at an applied voltage of 50 kV. Recently, Tampieri et al. (2018) developed a mini prototype reactor based on streamer discharges in air to screen the performance in oxidizing organic pollutants in water. They reported that the reactor performed well in degrading phenol and rhodamine B, which are common standards for the comparative evaluation of AOPs. The reactor was also found to be effective in the treatment of metolachlor, a recalcitrant organic contaminant, which was mineralized with a yield of 20% in 30 min. The ability of cold plasma in air to effectively degrade pesticides, namely dichlorvos, malathion, and endosulfan, in water has been demonstrated (Sarangapani et al., 2016). Some other studies have also reported the successful degradation of endosulfan and organophosphorus pesticides using oxygen containing inducer gases (Bai, Chen, Yang, Guo, & Zhang, 2010; Manoj Kumar Reddy, Mahammadunnisa, & Subrahmanyam, 2014). In a recent study the effectiveness of high-voltage DBD plasma at atmospheric pressure was evaluated for its effect on dairy and meat fats, and considerable degradation was observed (Sarangapani, Ryan Keogh, Dunne, Bourke, & Cullen, 2017). Similar results have been reported in many other studies (Gavahian, Chu, Mousavi Khaneghah, Barba, & Misra, 2018). Thus the breakdown of dairy and meat industry wastewater rich in fatty components can also be achieved with good efficiency using cold plasma technology. Overall, the limited number of studies carried out so far indicates that cold plasma technology can be used for effective degradation of pesticides and organic matter in wash water and wastewater released by food processing industries.

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16.6

Green Food Processing Techniques

Cold plasma for sustainable food production

With the global population projected to rise beyond what could be balanced by existing agricultural practices and the available natural resources (land, water, and energy), the demand for innovative sustainable agricultural technologies is bound to rise. In addition, there is already an increasing trend of movement toward urban agriculture, vertical farming, aeroponics, aquaponics, and precision farming (Wolfert, Ge, Verdouw, & Bogaardt, 2017). Within this scenario, cold plasma technology could also become a contributor to the agricultural sustainability due to several emerging agricultural applications that are being demonstrated. Examples of such applications include the enhanced seed germination, fungal control in agricultural seed material, plant growth enhancement, and production of nitrates for fertigation. Plasma treatment has been found to decrease the apparent contact angle of seeds, thereby resulting in an increased water imbibition in seeds. In fact the introduction of oxygen and nitrogen containing groups on the seed surface has also been confirmed through mass spectrometry studies (Bormashenko, Grynyov, Bormashenko, & Drori, 2012). In addition, an increase in root and shoot length (distribution) and mass has also been confirmed in many studies (Fig. 16.4). These enhanced effects have been attributed to an increased antioxidative activity in the seeds and changes in the hormonal patterns (Stola´rik et al., 2015). A summary of selected studies exploring the plasma treatment of seeds and its effect on enhanced germination and/or plant growth is included in Table 16.2.

Figure 16.4 Distribution of seed population as a function of the length of sprout for untreated and 15 min plasma-treated wheat seeds (all seeds were cultivated for 4 days). Source: Reproduced from Dobrin, D., Magureanu, M., Mandache, N. B., & Ionita, M. -D. (2015). The effect of non-thermal plasma treatment on wheat germination and early growth. Innovative Food Science & Emerging Technologies, 29, 255
260.

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Table 16.2 Summary of studies exploring the effect of cold plasma on seed germination and/or plant growth enhancement. Seeds

Sources

Salient results

References

Lentils, beans, wheat

RF plasma in air

Bormashenko et al. (2012)

Oat, wheat

Low-pressure cold plasma

Lamb’s quarters

Low-pressure microwave discharge

Decrease in the apparent contact angle of seeds and increased water imbibition Late stage increases in wheat plant growth, and increase in root generation in oats, originating from treated seeds About three times increase in seed germination rate was observed

Blue lupine, catgut, honey clover, and soy

Capacitively coupled plasma

Tomato

Ozone generator

Radish sprout

Atmospheric discharge plasma

Wheat

Atmospheric pressure surface discharge

Presowing plasma treatment led to enhanced field germination and survival Exposure to low O3 concentration for a moderate time was beneficial in alleviating seed dormancy Enhanced germination rate, shoot length, and root length observed in plants grown from treated seeds. Increased growth was attributed to increased antioxidative capacity Plasma treatment resulted in increased root and shoot length and weight distribution

Sera, Spatenka, Sery, Vrchotova, and Hruskova (2010)

Sera´, Strana´k, Sery´, Tichy´, and Spatenka (2008); ˇ ´ , Sery ˇ ´, Sera ˇ ˜ a´k, Spatenka, ˇ Stran and Tichy´ (2009) Filatova et al. (2010, 2011)

Sudhakar et al. (2011)

Hayashi, Ono, Shiratani, and Yonesu (2015)

Dobrin et al. (2015)

(Continued)

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Table 16.2 (Continued) Seeds

Sources

Salient results

References

Oat

Low-pressure cold plasma

Dubinov, Lazarenko, and Selemir (2000)

Herbaceous plant (Andrographis paniculata)

DBD plasma in air

Corn

Ozone generator

Soybean

Low-pressure RF plasma

Pea

Diffuse coplanar surface DBD plasma

Continuous plasma treatment was effective compared to pulsed discharge for growth enhancement 10 s treatment resulted in permeability enhancement of seeds resulting in seed germination acceleration and seedling emergence Faster initiation of germination was observed for treated seeds, thereby resulting in a larger number of germinated seeds with longer roots in 4
5 days Germination, vigor indices, and water uptake of treated seeds significantly increased. The apparent contact angle decreased In addition to the enhancement of percentage of germination and growth enhancement, plasma treatment provoked changes in endogenous hormones (auxins, cytokinins, and their catabolites and conjugates)

DBD, Dielectric barrier discharge.

Tong et al. (2014)

Violleau, Hadjeba, Albet, Cazalis, and Surel (2008)

Ling et al. (2014)

Stola´rik et al. (2015)

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16.7

445

Energy efficiency and process cost

Minimization of energy consumption and efficient use of thermal energy remains at focus in the food industry since many decades. The development of novel nonthermal technologies continue to provide a potential approach to reduce energy consumption and costs of operation, as well as to improve sustainability of production (Pereira & Vicente, 2010). The high-voltage atmospheric pressure cold plasma is an energy-efficient technology that can sufficiently ionize air in a 4 L reactor in seconds to minutes using high voltages (typically greater than 50 kV), with low current (1
2 mA), resulting in a low-power (100
200 W) consumption. In Fig. 16.5, we present the power measurements as a function of applied voltage in an in-package DBD, to sustain a stable discharge in air at 4.2 cm gap for dielectric thicknesses of 1 and 2 mm. It can be observed that the maximum power consumed at an applied voltage of 80 kV (RMS, 50 Hz frequency) does not exceed 130 W. To make an appropriate comparison the power consumed is in the order of that required by a light bulb. Hence, it is easy to see that the in-package cold plasma technology is energy efficient. When considering the application of cold plasma technology for large-scale operations, the cost of the equipment and the process gas are both important variables. Ideally, the machine should be inexpensive, and the process relies on common atmospheric gases, preferably ambient air. While during the early years of plasma research for food and biological applications, noble gases (e.g., He and Ar) were popular; there is a notable shift toward the use of atmospheric gases (including commonly modified atmosphere packaging gases) and air (Milosavljevi´c & Cullen, 2017; Misra, Moiseev, et al., 2014). That being said, noble gas plasmas could still prove useful for the treatment of high-value foods or

Figure 16.5 Power consumed by a DBD with 42 mm discharge gap for two different dielectric thicknesses operating in air as a function of the applied voltage (Misra, 2014). DBD, Dielectric barrier discharge.

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Green Food Processing Techniques

functionalized ingredients that are sensitive to oxidizing species (from oxygen in the plasma). An example of this includes the use of argon cold plasma for enhancing the extraction from oleogeneous plant materials (Kodama, Thawatchaipracha, & Sekiguchi, 2014). It is important to note that most of the studies concerning cold plasma technology for food applications have been performed in lab scale. Therefore, the results obtained are difficult to extrapolate to scale-up usage and cannot be generalized. However, the progress in plasma science and technology indicates that the cost of plasma treatments is likely to considerably plummet in the future.

16.8

Conclusion

Disinfection is one of the most critical processing steps in food production, affecting the quality, safety, and shelf life of the product. The competitive advantages that could be derived by using cold plasma technology include: (1) The increased safety profiles providing the food industry with a powerful marketing message for increasing consumer confidence. (2) The replacement of chlorine will safeguard the health and well-being of consumers and will enable producers to tap into a growing demand for products free from artificial chemicals that are safer for human health and the environment. (3) Environmental and economic benefits will be derived from reduced water usage, given that cold plasma is a dry preservation technology, this will alleviate the considerable burden of freshwater consumption by the food and agriculture sector. (4) In addition, shelf life extension will facilitate expansion of markets, longer display of life and a reduction in waste generation due to expiration. Cold plasma technology can be applied to a wide range of foods, including shelf life extension of fresh produce, meats, decontamination of grains and pulses, and eggs within cartons. The current limitations of cold plasma technology for industrial application are associated with the high investment costs, the lack of full control over process variables, and regulatory barriers. It is likely that some of these technologies, according to their specificities, will find niche applications in the food industry (some of them already did), replacing or complementing conventional preservation technologies, through synergistic interactions (e.g., hurdle concept) (Keener & Misra, 2016). Irrespective of the current state of the technology, it is evident from research outcomes that cold plasma technologies have clear environmental benefits and facilitate achieving sustainability goals for the industry.

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Microwave technology for food applications

17

Alice Angoy1, Syle`ne Brianceau2, Franc¸ois Chabrier2, Pascal Ginisty1, Wahbi Jomaa3, Jean-Franc¸ois Rochas4, Alain Sommier5 and Marc Valat3 1 IFTS, Agen, France, 2Agrotec, Agen, France, 3Bordeaux University, Bordeaux, France, 4 Waves Concept, Lyon, France, 5I2M, Bordeaux, France

17.1

Introduction: approach adopted in this chapter

What are microwaves (MWs)? What are the principles of dielectric heating? Do MW techniques respond to the requirements of novel technologies in the food industry have to comply with? What food processes are suitable for the MW processing? Does the MW processing of foods comply with the principles of a green process? These are the main questions raised in this chapter. In a second time, common beliefs are very often associated with MW techniques. This chapter tries to draw up a list of misconceptions attributed to MWs and through the works in the literature to provide a scientific point of view. It is particularly the case for applications in the food industry due to the complexity of raw materials and the numerous effects of heating on food products. Combined with this aspect, the potential impact of food on health generates a research activity which aims at demonstrating the beneficial effects of “novel” technologies such as MWs. However, the amazing amount of published works in this domain refers to a wide range of products and it is difficult to draw general conclusions on every aspect related to the use of MWs in the food industry. As an illustration, 257 documents relevant to keywords “food” and “MW” are referenced by Scopus in 2018 (at the end of May). Parallel to that, when a comparison is made between a so-called conventional process and the corresponding MW process, few, if any studies present, results obtained in comparable operating conditions and provide data for environmental impact assessment. This is probably due to the technical constraints for measuring basic parameters, such as temperature or relative humidity, in the presence of an electromagnetic field. Moreover, most of the works published regard lab equipment rather than industrial applications. In this chapter, the attempt is, from a nonexhaustive list of the common beliefs on MWs processes, to present a review of recent scientific works and to initiate, as clearly as possible, a discussion establishing the scientific reality of the more widespread dogmatic statements concerning MWs. Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00017-3 © 2019 Elsevier Inc. All rights reserved.

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The discussion is based on works relative to different food processing techniques: G

G

G

G

cooking, baking, and frying, drying, thawing and tempering, and extraction, etc.

Prior to this discussion, a brief presentation of the concepts of dielectric heating is provided. Constraints of measurement are also covered. The chapter closes with future trends of the use of the MW process in the food industry.

17.2

Principle, influencing factors, induced mechanisms

17.2.1 Introduction Dielectric heating corresponds to energy conversion from an electromagnetic wave (EMW) to a dielectric media. It differs from conduction or convection heating by several aspects. MWs are EMWs in a frequency range adapted to the size of most of the usual industrial products. The following main properties of MW heating can be quoted: G

G

G

G

G

volumetric heating, specific heating, theoretically unlimited absorbed power, fast heat transfer allowing lower drying temperatures and shorter drying times than in convection or conduction, and no direct contact with the heat source.

For food products, water is generally at the origin of dielectric heating (Datta & Davidson, n.d.). Moreover, food products are generally nonmagnetic materials (Ayappa, Davis, Crapiste, Davis, & Gordon, 1991) which discard specific phenomena associated with magnetic materials.

17.2.2 Some theoretical aspects of microwaves MWs are EMWs, that is, electric and magnetic fields (perpendicular to each other and perpendicular to the propagation direction), propagating in free space or in dielectric media (Fig. 17.1). An EMW is characterized by its wavelength λ and its frequency f which are related by the wave velocity c through λ5

c f

(17.1)

MWs cover the frequency band ranging from 300 MHz to 300 GHz. The most commonly used frequencies are 915 and 2450 MHz (both in the industry and 2450 MHz

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y x

E~ z

B~

λ

Figure 17.1 Plane EMW propagating in the z direction and polarized in the y direction. EMW, Electromagnetic wave. 2.45 GHz

915 MHz 1

2

10

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3

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Frequency (Hz)

23

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Radio frequency spectrum Microwaves HF

Visible light λ

8

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–1

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–7

–8

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–9

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–10

10

10

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–1

10

–1

10

–1

Wavelength (m)

Figure 17.2 Electromagnetic spectrum.

for home ovens) (Datta & Davidson, n.d.). In Europe, regulations impose a limit on the use of 915 MHz frequency. This radio frequency (RF) limitation is 240 dB μV/m at 30 m from the installation, with an obligation to declare the equipment to the competent authorities. This level of radiation is well below the limit imposed for the protection of people (typically 5 mW/cm2 at 2 in. from equipment in the industry and 1 mW/cm2 at 2 in. for household appliances for 2.45 GHz). This constraint on 915 MHz frequency explains why almost all the industrial equipment is of the batch type. Only England benefits from a derogation for a frequency of 896 MHz without limitation of radiation other than for the protection of the people. Fig. 17.2 shows the electromagnetic spectrum and more specifically the RF and MWs spectra. In vacuum, EMWs propagate at the light speed co . When an EMW propagates in a dielectric material (i.e., nonconductive), it interacts with the atoms or molecules of the materials and the wave velocity v is lower in vacuum (corresponding value: co ). The interaction depends on the polarization and on ionic conduction (free ions or ionic species are oriented by themselves by ionic motion generated in the electrical field) in the material. Polarization results from different mechanisms: G

G

G

G

electronic polarization, atomic polarization, dipolar polarization (alignment of polar molecules caused by MW irradiation), and interfacial polarization.

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The most significant effect for dielectric heating, at MWs frequencies, is dipolar polarization. Polarization is described by the permittivity E of the material. In most textbooks, complex relative permittivity is used and is defined as Er 5

E Eo

(17.2)

where Eo 5 8:85 3 10212 F/m is the permittivity of free space (Schubert & Regier, 0 2005). Relative permittivity is a complex quantity whose real part Er is named the 00 permittivity of the material and the imaginary part Er , the loss factor. The loss tangent (named also dissipation factor) tanδ is also defined as 00

tanδ 5

Er E0r

(17.3) 0

The permittivity Er gives the ability of a particular media to “store the electrical potential energy” from an electrical field, whereas the loss factor is responsible for the wave attenuation and the conversion of electrical energy into heat. For distilled 0 00 water, at 20 C, values of permittivity are Er 5 78:2 and Er 5 10:3. In a dielectric media, as the wave velocity decreases, the wavelength λm also decreases in regard to the wavelength in vacuum λo . MWs as EMWs obey Maxwell’s equations. However, it is not a question here of describing the theory underlying electromagnetism but to give a comprehensive presentation of the phenomena involved in dielectric heating. On the basis of the interaction of a plane wave (EMW) with a dielectric material, a qualitative description of the physical principles responsible for dielectric heating is given in the following part.

17.2.3 An insight into the principles of dielectric heating 17.2.3.1 Interaction wave/matter When a plane EMW travels in a dielectric 1 (say air) and strikes the surface of another dielectric 2, depending on the properties of the two dielectrics, the following phenomena take place (Roussy, Rochas, & Oberlin, 2003) (Fig. 17.3): Case 1—If the permittivity of dielectric 2 is greater than the permittivity of air, a transmitted wave propagates in dielectric 2 (lower wavelength). If the second dielectric is nonlossy, the transmitted wave is not attenuated in dielectric 2. It is the case of the microwave (MW) transparent materials (e.g., quartz) where the MWs pass through the material without any loss. A reflected wave traveling in the opposite direction to the incident wave is formed. The amplitude of the reflected wave depends on the contrast of permittivity 0 (Er ) between dielectrics 1 and 2. Case 2—In the case where dielectric 2 is lossy, the transmitted wave is exponentially attenuated and electromagnetic power is converted into heat in the material. It is the case of MW-absorbing (lossy) materials (e.g., polar molecules such as water).

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Figure 17.3 Plane wave propagating in the air and striking a plane surface: (Case 1) nonlossy dielectric material, (Case 2) lossy dielectric material, and (Case 3) conducting material.

G

Case 3—If the second medium is a perfect conducting material (e.g., metals), it can be treated as a dielectric with an infinite permittivity. In this case, the wave is reflected. Induced currents in the vicinity of the surface (skin effect) diminish the amplitude of the electric field (for nonmagnetic materials) for the reflected wave.

The only relevant configuration for dielectric heating is case 2. The electric field of the transmitted wave interacts with polar structures (polar molecules or clusters) in the dielectric and if the frequency of the incident wave is properly adjusted, conversion of electromagnetic energy into heat occurs in the volume of the dielectric. Metaxas and Meredith (1983) provide an explanation of dielectric heating in the following manner: “the origin of the heating lies in the ability of the electric field to polarize the charges in the material and the in inability of this polarization to follow extremely rapid reversals of the electric field.” At a certain frequency, in a band of frequency centered around on a frequency named relaxation frequency, the polar molecules experience difficulties in aligning themselves with the alternating electric field. This results in heat dissipation due to

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ε⬘, ε⬙ ε⬘

ε⬙ fr

f

Figure 17.4 Evolution of dielectric permittivity and factor loss as a function of frequency.

interacting forces between molecules. If these interactions between molecules are weak, as for gases, no heat is produced. The extent of heating is given by the loss tangent (high if tanδ . 0:5, medium if 0:1 , tanδ , 0:5 and low if tanδ , 0:1). Both ε0 and ε00 depend on wave frequency and temperature. ε0 is a decreasing function of frequency and ε00 goes through a maximum at the “relaxation frequency” fr (Fig. 17.4). At this frequency, permittivity ε0 experiences a rapid decrease because the clusters or molecules in the dielectric fail to align in the direction of the electric field due to its rapid change. For water, the maximum value of ε00 is obtained at approximately 20 GHz (Schubert & Regier, 2005). Temperature dependence of both permittivity and loss factor varies from one product to the other. In the case where permittivity decreases and loss factor increases with temperature, the power dissipated in the material raises with the temperature of the product and may lead to a thermal runaway. Moreover, relaxation frequency increases with temperature and is significantly lower than 20 GHz for bond water. Thus an efficient dielectric heating might become much less efficient when water activity decreases during the drying operation, for example. As mentioned earlier, the amplitude of the wave, in a lossy dielectric, decreases exponentially according to the following equation: P 5 Po e2z=Dp

(17.4)

where P is the power transported by the wave at a distance z from the plane surface and Po is the incident power. The penetration depth Dp is defined as the distance from the surface at which the incident power is reduced to 37% of its value and may be expressed as (Fu, 2008) Dp 5

co sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi  pffiffiffiffiffiffiffi 2 0 2πf 2εr 1 1 ðtanδÞ 2 1

(17.5)

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When tanδ is small (e.g., ,0.1), the previous equation can be simplified as follows: Dp 5

pffiffiffiffi c0 ε 0 2πf ε0 0

The expression shows that the penetration depth is inversely proportional to the wave frequency. It is a decreasing function of the loss factor. For water at 20 C and at 2.45 GHz wave frequency, the penetration depth is about 1.7 and 5.7 cm at 95 C. The choice of 915 MHz or 2.45 GHz for MW operational frequencies is the result of a compromise: at 915 MHz, the loss factor is not at its maximum for water but in return, it has a higher penetration depth. The rate of heat generation per unit volume, Q_ mw in a dielectric material at a given position is provided by 00 Q_ mw 5 2πf εo εr E2

(17.6)

where E is the root mean square value of the electric field and f the wave frequency. The distribution of electric field in the material is far from being uniform and is difficult to predict due to the complex phenomena involved, which depend on numerous factors (shape and size of the product, type and shape of the applicator, product dielectric properties, etc.).

17.2.4 Heat and mass transfer in food processing To highlight the interest in MW heating, Schubert and Regier (2005) propose to compare the rate of heat generation by MW to the rate of heat conduction in a plane slab of thickness 2l (with 2l , 2Dp ) irradiated from both sides: Q_ mw ωεo εr 00 E2 l2 5 kΔT Q_ cond

(17.7)

To achieve high rates of conduction, it is thus necessary to impose a high temperature gradient (high ΔT). When the temperature difference ΔT is limited, MW processes will lead to a much faster operation. More uniform heating may also be obtained, if heat generation is evenly distributed in the dielectric material. However, dielectric heating depends on the magnitude of the electric field which, in most cases (thick products), strongly varies inside the product. As a result, hot spots are frequently observed and require a control of the process and/or the introduction of a mode stirrer or a rotating turntable to avoid a loss of quality of the product (Chandrasekaran, Ramanathan, & Basak, 2013).

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17.2.5 Associated metrology MW setup is constituted of a source (magnetron or klystron), a line (waveguide) to transport EMW to the applicator in which the product is positioned. Several textbooks describe in details MW devices (Fu, 2008; Metaxas & Meredith, 1983; Schubert & Regier, 2005; Reader, 2006).

17.2.5.1 Incident and reflected power During the MW heating operation, the material absorbs part of the incident power and a portion is reflected by the cavity and returns to the MW generator. The amount of reflected power depends on the impedance match between the applicator and the transmission line. The input impedance of the applicator is related to the applicator and the product volumes and on the dielectric properties of the product. If a perfect match is obtained, only part of the incident power is transmitted to the material, the rest being dissipated in the applicator walls. If the reflected part is too important, the magnetron may be degraded. Generally, large magnetrons are protected from reflected power by a circulator that diverts reflected power from magnetron to a water load. The monitoring of the reflected power is generally a good indicator of the amount of water loss in the product and therefore a useful tool to manage MW heating operation. A manual or an automatic impedance matching allows a reduction of the reflected power and adaptation of the incident power to the product and to the cavity. This matching consists of inserting an iris or stub system into the waveguide.

17.2.5.2 Temperature measurement The electromagnetic field inside the cavity being very intense most of the sensors are disturbed in this environment and most electronic devices could be damaged. For measuring the temperature inside the product, normal thermocouples will cause a disturbance of the electromagnetic field and cannot be used. Fiber-optic sensors are a good alternative as they avoid this disturbance problem. All other types must be deported outside the cavity and protected with wave traps. Metal tubes with sufficient length, fixed on the cavity, could serve as wave traps and thus prevent the electromagnetic field from damaging the sensor. For this, the tube diameter has to be lower than the cutoff wavelength at the working frequency. Moreover, the tube length has to be greater than the propagation length of the evanescent wave. It is important to specify that tube diameter has to be further reduced if the tube is filled with such a dielectric material as quartz. With such wave traps, infrared sensors can provide reliable information on the surface temperature of the product and can be used to drive the operation. Different technologies have been tested in MW systems as shown in Table 17.1.

Table 17.1 Comparison of different temperature analysis systems. Technology

Monochromatic radiation pyrometer

Two-color radiation pyrometer

IR thermography

Optical fiber thermometer

Thermocouple

Measurement range ( C)

0
2800

0
50 (depending on the model)

0
1900

0
1600

Adapted to microwave Advantages

Yes Contactless Moderate cost Moderate accuracy Easy to move on the surface Usable in continuous

400
4000 Not adapted for food industry Yes Contactless Moderate cost High accuracy Easy to move on the surface Usable in continuous mode Surface measurement

Yes Contactless Good accuracy Give map of surface temperature

Yes Contact Excellent accuracy

No Contact Low cost Good accuracy in conventional heating system

G

G

G

G

Disadvantage

G

Surface measurement

G

G

G

G

G

G

G

G

G

G

G

Surface measurement

G

G

G

High cost Usable only in batch Very fragile

G

Usable only in batch

Source: From Cuccurullo, G., Berardi, P. G., Carfagna, R., Pierro, V. (2002). IR temperature measurements in microwave heating. Infrared Physics & Technology, 43, 145
150. doi:10.1016/ S1350-4495(02)00133-0 (Cuccurullo, Berardi, Carfagna, and Pierro, 2002); Pert, E., Carmel, Y., Birnboim, A., Olorunyolemi, T., Gershon, D., Calame, J. et al. (2001). Temperature measurements during microwave processing: The significance of thermocouple effects. Journal of the American Ceramic Society, 84, 1981
1986. doi:10.1111/j.1151-2916.2001.tb00946.x (Pert et al., 2001).

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Table 17.2 The pros and cons of microwave processes in the food industry. Pros

Cons

Ability to achieve high heating rates

Narrow dependence of dielectric properties on food product characteristics (quantity and state of water, salt and sugar concentration, particle size, structure, density, etc.) Nonuniform temperature distribution (hot and cold spots) Difficult process control (temperature measurement dependent on temperature distribution, etc.)

Volumetric heating Selective heating Color and texture preservation according to the process Reduced processing time

17.2.6 Pros and cons of dielectric heating in food processing The frequently reported properties of MW processes in the food industry are listed in Table 17.2.

17.3

Techniques at laboratory and industrial scale

Manufacturers have developed MW systems at the lab scale. Poux, Estel, and Len (2016) have listed all the setup available for organic synthesis and extraction. The maximum delivered power varies from 0.2 to 6 kW and the volume of the reactors from ,1 mL up to 5 L. Most apparatus operate in batch mode. Continuous and discontinuous processes are available. However, this type of apparatus (lab scale) for food processing is not developed. Thus for a given couple (product/process), a very thorough study is required to establish the feasibility of the process at the pilot scale.

17.4

Pre- and postprocessing and coupling

The MW technique is the only operational unit in a global process system and can be used as a pretreatment of the materials before further processing, and posttreatment as an intermediate or final stage of a process. It can be coupled with other technologies to enhance its productivity and efficiency.

17.4.1 Pretreatment 17.4.1.1 Pretreatment by means of microwaves MW could be used as a pretreatment step to improve the efficiency of other stages in the process.

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MW pretreatments of oilseeds before mechanical/chemical extraction are likely to improve oil yield and oil quality during storage, even under extreme environmental conditions. The treatment simply consists of a short application of MWs (a few minutes) before conventional oil extraction. A review by Koubaa et al. (2016) analyzes different studies using MWs in pretreatment for oilseed extraction. For instance, preheat of sunflower seeds by MWs resulted in a decrease in lipase activity accompanied by an increased content of phosphorus and free fatty acids (Veldsink et al., 1999). Rapeseed oils have a better flavor when preheated by MWs and for sesame seeds. ´ Concerning rapeseed oil, two studies carried out by Re˛kas, Scibisz, Siger, and Wroniak (2017) and Wroniak, Re˛kas, Siger, and Janowicz (2016) use MWs prior to cold pressing. They show that the storage stability of phenolic compounds was higher in oils produced from MW pretreated rapeseeds than in reference oils, whereas the fatty acid composition of oils was not altered (relevant from the nutritional point of view). MW treatment significantly improves the fuel characteristics of the wheat and barley straw and improves the grindability and hydrophobicity of the biomass before torrefaction (Satpathy, Tabil, Meda, Naik, & Prasad, 2014). MW applied as pretreatment induces lignocellulosic breakdown through the molecular collision caused by the dielectric polarization (Aguilar-Reynosa et al., 2017). It allows the treatment time to be reduced from 17 h to 3 min compared to classical hydrothermal treatment and fractionates lignocellulosic compounds into a celluloserich residue, a liquor rich in lignin and recoverable hemicellulose (Singh, Bhuyan, Banerjee, Muir, & Arora, 2017). After this pretreatment, alkali hydrolysis liberates 75%
80% of reducing sugars (to be compared with the value of two percent obtained with untreated biomass). This pretreatment has been shown to work effectively with a wide range of lignocellulosic feedstocks as rape straw, sugarcane bagasse, sago, and wheat straw (Kostas, Beneroso, & Robinson, 2017). MW pretreatment may also be before anaerobic digestion to help the hydrolysis step.

17.4.1.2 Pretreatment before microwaves Several pretreatments have been reported to have a beneficial effect on MW efficiency. The plant material can be sieved or ground. Smaller particle size facilitates better solute
solvent interactions (Kala, Mehta, Sen, Tandey, & Mandal, 2016). Huang, Kuan, and Chang (2018) have shown that both maximum temperature (from 475 C to 557 C) and heating rate (from 75 to 95 C/min) increased with decreasing particle size (from around 1 mm to 150 μm) of corn stover during MW pyrolysis. Nevertheless, too many finer particles may cause problems in subsequent cleanup systems. The preleaching time (time of contact between the plant matrix and solvent before irradiation) improves the hydration status of the plant, thus making the cell more susceptible to thermal stress for polyphenols extraction (Kala et al., 2016). Immersion in a hypertonic solution increases mass transfer of water between membranes and extracellular media.

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The increase in the water content (with vapor for example) in matrix promotes hydrolyzation and reduces the risk of oxidation of active compounds

17.4.2 Posttreatment 17.4.2.1 Posttreatment after microwaves Enzymatic saccharification and fermentation are also classically used after this MW treatment has been used to enhance delignification. Once the extraction is completed, the extract has to be clarified, especially if the matrix has been previously ground, to remove solid particles by filtration and/or centrifugation techniques and then purified by chromatographic processes, for example.

17.4.2.2 Microwaves as posttreatment MW could be applied at the end of air-drying (moisture ,20%) in order to finish the operation of moisture squeezing. Drying times could be reduced down to 64% for bananas for instance (Karam, Petit, Zimmer, Baudelaire Djantou, & Scher, 2016).

17.4.3 Coupling An important aspect of dielectric heating is that heat is provided essentially to the product. However, irrespective of the process, thermal transfers by conduction, convection, or thermal radiation exist between the product and the device. It follows that part of the MW energy (obtained at a high investment per kW) is spent to compensate for the thermal loss of the product. In many cases, it is more advantageous to combine with MWs a conventional heating to reduce the installed MW power. The investment is reduced and also the risk of arcing due to the decrease in electric field because of the reduction of power required. As an example, MW-assisted drying can be cited. Water vapor is not absorbent (nonlossy) but has to be evacuated to eliminate condensation on the dryer walls and to limit the humidity of ambient air. Thus for an efficient drying, beyond the mechanisms of heat generation in the product, aeraulic conditions have to be carefully defined (temperature and air flow rate). In the case of an overventilation, the required MW power will raise. On the contrary, an underestimate of air flow rate will lead to condensation in the dryer with the risk of rewetting the product and an increasing risk of arcing. A recent trend is the concept of hybrid/combination mode or otherwise called MW-assisted food processing technologies, which infers utilizing MW s to enhance conventional and nonconventional food processes and consequently obtaining high end products, that is not readily achievable by traditional techniques. The technology integrates the advantage of MW energy to overcome the shortcomings of other food process technologies. A typical example is the combination of MW energy with convection heating with the latter being known to require greater energy consumption and longer processing times.

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MW-assisted drying techniques can be divided into three categories: MWassisted air drying (MWAD), MW-assisted vacuum drying (MWVD), and MW-assisted freeze-drying (MWFD). MWAD is principally used in several industrial food processing applications in order to shorten drying times and enhances product quality as compared with hot air drying alone. For kiwi fruits and banana slices, increase in drying rates of 64% and decrease in tissue shrinkage of 40% are reported (Karam et al., 2016). The coupling of MW s with other drying methods permits also to overcome some limitations of single MW drying: occurrence of hot spots in the foodstuffs during heating, subsequent to nonuniform electrical field, textural damages (arcing at power .500 W in small-scale drying cavities and puffing) as well as subsequent scorching and development of off-flavors. MWVD is one of the recently emerging food processes and is especially suitable for heat-sensitive products (such as fruits of high sugar content and highvalue vegetables). It has been successively used for drying grapes, cranberries, bananas, tomatoes, carrots, garlic, potatoes, kiwi fruits, apples, pears, etc. MWFD shortens drying times to 70%
90% and remains faster than freezedrying (FD) or HAD with products of better qualities (higher porosity, lower density, lower shrinkage) as well as higher rehydration potential and minimal extent of color change. The energy savings can achieve 54% and are particularly convenient for products of intermediate value but it is difficult to use in large industrial applications due to gas ionization. Section 17.6 gives a lot of examples of coupling MW s with other principles to integrate the benefits of MW technology. We can quote also some examples where MW technology is assisted. For instance, vacuum reduces the boiling temperature of the solvent (interesting for thermally sensitive products) and provides an oxygenfree environment (interesting when oxidation of target is feared). Ultrasounds help to increase the yield of polyphenols by promoting the destruction of the cellular integrity. High pressure helps in squeezing out the analytes from the punctured cell walls and glands (Kala et al., 2016).

17.5

Applications in transformation, food processing, and preservation

Theoretical time saving in heating systems using MWs attired companies and in particular food industries. During the last 40 years, tests have been performed in order to integrate MW technologies in classical food industry processes like pasteurization, sterilization, blanching, or frying.

17.5.1 Pasteurization
sterilization Pasteurization and sterilization are two thermal processes. They are used to increase shelf life of food products. Pasteurization is a food treatment aiming to eliminate

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pathogenic microorganism and to reduce overall microbial load (Bornhorst, Liu, Tang, Sablani, & Barbosa-Ca´novas, 2017). Sterilization is also a food treatment of the product and in most cases of its packaging in order to eliminate all microorganisms of the product (Al-Baali & Farid, 2006). Historically, pasteurization as sterilization treatments is thermal processes based on convection or conduction systems. In the past 50 years, other nonthermal treatments are used as pulsed electric fields, high-pressure system, etc. MW techniques are used for pasteurizing as well as for sterilizing operations. Different cases come from the industry as well as from the laboratory. It can be used in continuous mode or in batch. Single mode cavities are used most of the time in the food industry. Power of installations is of course depending on the size of the installation ranging from 10 to 200 kW (Brody, 2011). In pasteurization and sterilization applications, MW technology (alone or in combination) presents specificities in comparison with other ways to heat products.

17.5.1.1 Time savings For pasteurization treatment, MW can be used as a single way of heating food or in combination with another system (usually hot water). Peng et al. (2017) have shown comparisons between packed carrot pasteurization in hot water and MW. They show that after 20 min at 60 C preheating time, heating time to reach a 3 min F90 C value is more than 5.7 times shorter by using MW than hot water. To reach the F90 C 5 3 min in an MW system, a holding time is needed. If these two durations are considered, the saved time is still around 60%. Same approach is done with an F90 C 5 10 min target and MW system has a heating time 9.5 times quicker than hot water system. Including the holding time, saved time is around 64%. The same conclusion is also given for other food products like mashed potatoes or green peas puree (Bornhorst, Tang, Sablani, & Barbosa-Ca´novas, 2017).

17.5.1.2 Food quality preservation Measured impact on process time is also completed by a positive impact of MW treatment on food quality. For instance, Peng et al. (2017) have shown that packed carrots treated by MW present a higher Betacarotene and carotenoids rate than those treated by hot water. The same conclusion is drawn by Bornhorst et al. (2017) for the color of mashed potatoes. She demonstrates that time reduction is responsible for a diminution of Maillard reaction. Food quality is also evaluated by Bornhorst, Liu, et al. (2017) with model foods applied on mashed potatoes and peas. A demonstrated model has been developed to show the impact of pasteurization (assisted by MWs or with hot water) on food products and confirms previous conclusions: color changes are reduced in MW-assisted processes. Effect of MW on texture is not different from hot water treatment effect. Quality of MW s heated products is also demonstrated for surimi products (Cao et al., 2018). Two processes are compared.

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The first one is the most common. It uses steam and hot water in different baths to process surimi. The first step is to drop raw material to a 93 C water bath for a 90 s duration, then it falls to a second pool at 95 C for 90 s to permit coagulation. These two pools are heated by steam (158 C/0.6 MPa) and pumps ensure water circulation. The second one, more innovative, uses a combination of steam and MW. Instead of soaking food product in different pools, the product is conveyed at 5.27 m/min throw boxes that send MW s (at 25, 35, and 45 kW) and steam is sprayed to avoid the drying of the product and to add an auxiliary heating system. Comparison of different parameters drives to different conclusions. The moisture content of the product is really more controllable on the combined process with MW; texture is therefore easier to control. Sensory analysis has also given better results on product transformed by MW and steam. Improvement of the texture of fishes is also related by Ji, Xue, Zhang, Li, and Xue (2017) on Alaska Pollock surimi. MW process (300 W for 1, 2, 5, or 10 min) gives better gel texture than water bath treatment (30 min immersion in a 90 C water).

17.5.1.3 Energy consumption Energy consumption measurement method has to be defined before running any comparison. It is quite hard to find subsequent energy consumption comparisons in the scientific literature. Such a comparison has been done on a surimi process (Cao et al., 2018). Process consists of heating surimi in a water bath (gas heated) or in a water bath with MW s. In this case (as in most of the studies), time to heat product is really reduced (Liu & Lanier, 2016) and consequently energy consumption. For this surimi application, energy saving represents 13.69% by reducing time of 61%. Comparison of parameters of different approaches can be based on the examples from the literature of the last years. It shows also that pasteurization or sterilization are topics mainly studied in China or the United States over the last 5 years (Table 17.3).

17.5.2 Drying Drying, one of the oldest preservation techniques, consists of removing water from the product by application of heat. The moist product is heated to a specific temperature where the evaporation or vaporization can occur. Drying process techniques can be classified into different categories depending on the mode of heat transfer and the mode of moisture evacuation. Two modes of heat transfer can be distinguished, which are as follows: G

G

Surface supply with conduction, convection, or radiation where heat is supplied on the surface of the product. The surface of the product dries out faster than the core and depending on the drying conditions of an overdrying at the surface can occur leading to a case-hardened layer formation. Volumetric supply where heat is supplied to the core of the product thanks to the interaction of the wet material and especially water with the electromagnetic field.

Table 17.3 Comparison of different pasteurization and sterilization process microwave assisted. Action

Product

Microwave alone or combination

Main parameters

Laboratory (LS) or industrial scale (IS)

Source

Pasteurization

Mashed potatoes and green peas Surimi

C

Preheating at 60 C in hot water than exposition to a single mode 915 MHz microwaves and recirculating hot water (1.7 min at 90 C or 95 C) Steam and microwave combination, belt conveyor at 5.27 m/min, power of magnetron at 25, 35, and 45 kW Single mode 915 MHz microwave system and four sections [preheating with water, microwave heating in water (2 cavities with a 14 kW power), holding in hot water and cooling ice cold water] Samples are heated in microwave set to 300 W for 1, 2, 5, and 10 min; comparison with a water bath at 90 C for 30 min Batch system using a 486 kW magnetron at 2.45 GHz

LS

Bornhorst, Tang, et al. (2017)

IS

Cao et al. (2018)

LS

Peng et al. (2017)

LS

Ji et al. (2017)

LS

Sarah, Madinah, and Salamah (2018) Tang et al. (2008)

Pasteurization

C

Pasteurization

Prepacked carrots

C

Pasteurization

Alaska pollock surimi

A

Pasteurization

Palm fruit

A

Sterilization

Precooked beef slices Vegetable puree

C

Sterilization

C

Continuous system, 2 3 5 kW single magnetron at 915 MHz Under pressure system, using a 2.45 GHz microwave system at 1 kW

LS LS

Reverte-Ors et al. (2017)

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Unlike conventional drying methods, where the heat transfer from the surface of the product to the interior relies mainly on conduction, during MW drying, the energy is generated in the liquid, which is distributed throughout the wet material. Due to this phenomenon, there is a number of attractive advantages associated with the use of MW-enhanced drying, which include volumetric heating, moisture leveling, reduced drying times, and high drying rates. The reduction in drying time compared to conventional drying is very much dependent on the amount of MW incident power used in the drying process, and of course highly dependent on the type of product being dried. Other important differences are summarized in the following list: G

G

G

Volumetric heating: As the energy from the EMWs is transferred directly to the liquid, which is distributed throughout the wet material, a bulk heating phenomenon prevails. This volumetric heating can eliminate the case hardening of products, which is usually associated with convective hot air drying. Higher fluxes of liquid to the drying surface from the interior: During the period when the MW power absorption is maximal in the material, liquid fluxes migrate from the core of the material to its surface. This phenomenon underlines the importance of using adequate air flow rates over the drying surface in order to avoid excess liquid accumulation around the surface when these liquid fluxes are most prominent. High temperature and internal pressure buildup: Due to volumetric heating, a pumping effect appears to push the water from the interior of the material to the drying surface. This effect, which is caused by internal pressure buildup (Fig. 17.5), can be used to great advantage in enhancing moisture migration through the material during drying. It should be noted that due to the higher temperatures and pressures, there is a greater risk of causing mechanical or physical damages to the material.

1.4 A 1.3 Pressure (bar)

B 1.2

C

1.1 1 0.9 0.8 0

10

20

30

40

50

Time (h)

Figure 17.5 Internal gaseous pressures for different drying cases of pinewood (A) convective drying, (B) and (C) microwave drying with 5 and 10 kW/m2 incident power, respectively (Turner, Puiggali, & Jomaa, 1998).

472

G

Green Food Processing Techniques

Preferential heating of wetter areas: Due to the dielectric properties that are decreasing when the moisture content decreases, the wet regions of the material receive more energy than the dried ones. For instance, for thick materials, this phenomenon will help to get a moisture leveling. The power density exhibits a phase change during the drying process, and the MWs appear to “track” the moisture distribution in the pores of the material being dried.

During a drying process, three periods can be distinguished, which are as follows: 1. A warming phase or initial phase where temperature evolves quickly and water content drops slightly. 2. A so-called constant rate period where water content decreases rapidly. Temperature is mostly constant and depends on the drying process used (MW-assisted hot air drying, MW vacuum drying, MWFD, etc.). When water driven to the surface is not quickly transported away from the product, the temperature can reach the boiling temperature during this period (100 C at atmospheric pressure), 3. A falling rate period where the loss of water slows down and the temperature of the material increases. During this period the quantity of water transported from the inside of the product is not sufficient to maintain a wet surface.

During MW-assisted drying the falling rate period could be critical to be managed especially for foods where biopolymers can absorb the energy of the MWs. Indeed, an increase of εv with temperature will lead to an overheating and a risk of burning of the product (Franco, Tadini, & Wilhelms Gut, 2017; Siguemoto & Gut, 2016; Song, Wang, Wang, & Cui, 2016). In such sensitive products, MW energy should be intermittent or driven by a temperature measurement. The duration of each phase depends on the heat and mass transport properties of the product and on the energy delivered. A limitation of using MWs in a drying process is the nonuniformity of the electromagnetic field in the dryer, which can give a nonuniform temperature distribution in the product. In order to avoid this disadvantage the product can be moved making all parts receiving almost the same amount of energy or using mode stirrers to distribute the waves in the dryer. Mode steers are mobile metallic elements that modify the electromagnetic field, resulting in a nonstationary distributed energy over the product.

17.5.3 Microwave with convective drying In traditional air-drying processes, hot humid air is used to heat the material and to remove the moisture from the product. When associated with MWs, volumetric heating involves a liquid flux migration from the core of the material to its surface, and air flow is then mainly used to remove moisture from the surface of the product. Such combination significantly decreases drying time as it allows to lengthen the constant rate period and reduces the risk of case hardening at the surface of the material (Azam, Zhang, Law, & Mujumdar, 2018; Maurya, Gothandam, Ranjan, Shakya, & Pareek, 2018; Salim, Garie´py, & Raghavan, 2017).

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17.5.4 Microwave vacuum drying Vacuum drying is generally used for thermal sensitive products that cannot be processed by using hot air drying. Reducing pressure leads to reduce the water boiling point, for instance at a pressure of 0.1 bar, the vaporization temperature is almost equal to 45 C. Otherwise, reducing pressure and air density in the dryer weakens the ability of air to transfer heat to the material. The association between the vacuum drying and the MW heating seems to be a good alternative as MWs are efficient to transfer energy to the product (Lv et al., 2018; Monteiro, Link, Tribuzi, Carciofi, & Laurindo, 2018). In this situation the pressure level in the dryer mainly controls the product temperature during the constant rate period. During the falling rate period where moisture moving from the core is not sufficient to maintain a wet surface, the temperature might increase rapidly. During this period the energy of the MWs should be managed by being applied intermittently or driven by a temperature measurement.

17.5.5 Thawing and tempering Thawing and tempering differ from each other by the final temperature attained at the end of the process. Thawing is completed when the product temperature has reached 0 C and no ice is present (Schubert & Regier, 2005). For tempering, the final temperature is maintained just below the freezing temperature to soften the product in order to facilitate chopping and handling. James, James, and Purnell (2016) underline the importance of food contamination during thawing. The microbiological load is mainly located on the food surface, and during thawing, surface temperature is more elevated than the other parts of the food and such that the growth of bacteria is possible. Different conventional techniques exist for thawing (James et al., 2016) are as follows: G

G

G

air-assisted thawing (still and forced air), water-assisted thawing, and vacuum-condensing steam-assisted thawing.

Emerging techniques are also developed, such as acoustic pressure-assisted thawing and RF-assisted thawing. Tempering is usually performed processed with air. Both MW and RF techniques can be found in industrial processes. Because of lower frequencies, RF presents advantages as compared with MW thawing, such as greater penetration depth and more uniform heating. However, RF equipment is more expensive (Pham, 2014). An uneven distribution of heat with MWs may cause thermal runaway due to the greater absorption of MW in liquid water than ice. Consequently, the thawed parts of the food absorb a greater amount of energy and heat up rapidly, which can induce the beginning of cooking. To avoid this phenomenon, intermittent heating is usually applied to allow relaxation of the temperature field in the material. The main advantage of the MW thawing is a marked reduction

474

Green Food Processing Techniques

of thawing time. Taher and Farid (2001) use intermittent dielectric heating to thaw frozen minced beef. They obtain a better temperature homogeneity with cyclic heating than with continuous operation. They also compare thawing time for conventional (air thawing, 21 C) and temperature-controlled MW thawing. They observe a marked reduction of thawing time with the MW process (divided by 5). Chen, Warning, Datta, and Chen (2016) compare cycled power heating and inverter heating (constant power applied but with the same average power as for cycled heating) for the thawing of Tylose, in an experimental and numerical study. Inverter heating was presented as a method improving heating rate and temperature uniformity and limiting overcooking at corners and edges. Experimental results obtained show similar heating rates and no appreciable difference in color of samples treated by both methods. Pupan, Dhamvithee, Jangchud, and Boonbumrung (2018) studied the effect of different freezing and thawing methods on the flavor and sensory properties of durian puree. In particular, they used two different thawing methods, such as refrigerator and MW. The sensory analysis shows odor and flavor changes in the samples thawed by MW. Moreover, off-flavor and off-odor are remarked in the MW samples and are attributed to the formation of a new volatile compound during thawing. In this study the two thawing methods did not lead to significantly different drip losses. Moreover, the thawing time for the two methods was extremely different: 3 h for the refrigerator method (sample stored at 4 C and core temperature reached 0 C) and 70 s for MW thawing (100 W, core temperature reached 0 C).

17.5.6 Microwave frying Frying is a very specific food operation used in order to give some specific organoleptic properties of products (taste, texture, color, etc.) (Pankaj & Keener, 2017). Such a process is used in food industry as well as for domestic applications. MW application can also reduce process time in frying system. For instance, frying time for chicken breast meat has been reduced by a factor of three (Barutc¸U Mazi & Mazi, 2017) by using MW heating (365 W in a domestic oven) instead of classical frying system. The organoleptic results are correct even if the product color is little light and its texture not hard enough. It is also possible to fry french fries by using MW system (Parikh & Takhar, 2016). Results are much better than in chicken application. The two magnetrons of 750 W at 2.45 GHz used in a 36 L fryer help in increasing the quality of products. For a frying time over 90 s, fat content of french fries is lower than in the conventional system. Moreover, texture is also improved, and during the process, the internal pressure evolution of the product during MW frying is significantly higher than in the conventional frying. Using an MW can help in decreasing process time as well as improving quality product. Besides, effect can also be positive on oil quality. When oil is heated with a moderate power MW system (360 W), oil is more degraded than with high power

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475

(900 W) (Aydinkaptan, Mazi, & Mazi, 2017). It can be explained by the shorter heating time needed to reach the set point temperature. MW heating led to better final product properties (in free fatty acid level, peroxide value, viscosity, etc.) than with conventional systems. MW frying system can also be coupled with other systems, such as ultrasonic and vacuum system (Devi, Zhang, & Law, 2018; Su, Zhang, Zhang, Liu, & Adhikari, 2018) to improve the quality of mushroom or potato chips.

17.6

Applications in extraction of food ingredients

17.6.1 Extraction principle Due to its efficiency and ease of implementation, solid
liquid extraction is the most widely used technique for the recovery of bioactive molecules from plant sources. It is widely applied in the food and pharmaceutical industries to extract compounds of interest from plants for the production of beverages and medicines, for example. Solid
liquid extraction is a physical transfer of matter between a solid phase that contains the substances to be extracted and a liquid phase, the extraction solvent (Pham, 2014; Taher & Farid, 2001). Following the contact between solvent and heterogeneous solid, the substances having an affinity for the solvent are solubilized and transferred from the solid phase to the liquid phase. During extraction, substance content in the solid phase decreases, and their concentration in liquid phase increases. The transfer of matter is carried out by molecular diffusion and by convection. Extraction is a nonstationary process that stops when a balance of concentration in both phases (solid and liquid) is established. However, if the solvent is continuously renewed, the diffusion continues until the solid phase is exhausted (Dibert, Cros, & Andrieu, 1989). Generally, the extraction mechanisms are not very selective. In addition to the molecules of interest, other substances are also coextracted from the solid phase to the solvent. The solution obtained is called extract. The solid source exhausted after extraction contains very little or no solute. It is called residue. In some cases the plant material is pretreated before extraction to improve the contact between the phases. Drying and grinding are often used as pretreatment operations. Sometimes, enzymatic pretreatments are also used to facilitate the dissolution of interest molecules in the solvent. The rupture of cell walls by pectinases and cellulases promotes the extraction of phenolic compounds (Bonilla, Mayen, Merida, & Medina, 1999). During the extraction, the following successive stages of mass transfer can be distinguished: G

G

G

G

penetration of the solvent into the solid matrix, dissolution of the solute in the solvent, diffusion of the solute toward the peripheral part of the solid matrix, and transfer of the solute to the heart of the liquid phase (by diffusion or convection).

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Green Food Processing Techniques

The duration of solid
liquid extraction is determined by the slowest stage that controls the operation speed. Most often, it is the stage of internal diffusion in the plant matrix. The extraction consists of solubilizing and detaching the desired compound from the matrix in a reasonable time and in a satisfactory proportion (Perino-Issartier, Maingonnat, & Chemat, 2010). However, the process can sometimes be difficult and highly dependent on the complexity and geometry of the molecule and on the technique used. The nature of the solvent, extraction pH, surface exchange of solid phase, temperature, stirring, solvent-to-solid ratio, extraction time are some parameters influencing liquid
solid extraction. There are several techniques for extracting high value-added products from plants. These techniques can be called conventional (based on the classical mechanisms of extraction) or innovative (developed more recently and involving different mechanisms). Conventional techniques include Soxhlet extraction, maceration, and steam distillation (hydrodistillation). In the innovative technical category, MWassisted extraction (MAE), ultrasound-assisted extraction, accelerated solvent extraction, and supercritical fluid extraction can be cited.

17.6.2 Microwave-assisted extraction principles MAE was first used in chemical laboratories in 1986 by Gedye et al. (1986) and Giguere, Bray, Duncan, and Majetich (1986) in organic synthesis and by Ganzler, Salgo´, and Valko´ (1986) in the extraction of biological matrices. This nonconventional thermal energy source has an enormous potential for synthetic, analytical, and processing applications. In a conventional solvent extraction (CSE), mass transfers and temperature gradients are in opposite directions. Mass transfer takes place from inside outward, while the temperature gradients occur from the outside to the inside (conduction heating). For solvent extraction assisted by MW, heat and mass transfer operate in the same direction due to volumetric heating (Chemat, Abert-Vian, & Huma, 2009). Process intensification using MW heating may be due to a synergistic combination of heat and mass transfers. The energy of the EMW is dissipated in heat within the lossy material according to the distribution of the electromagnetic field (Luque de Castro & CastilloPeinado, 2016). The amount of MW energy absorbed by a specific sample depends on its loss factor that is finite for absorptive materials. When the loss factor of vegetal material is higher than the solvent’s, the plant material can reach higher temperature than the solvent, and consequently, the inside cell pressure increases resulting in the rupture of cell’s membrane and release of the components into the solvent. The reverse situation is also possible in which the solvent is polar and absorbs the energy of the waves. In this case the plant material is heated by conduction, and the release of the matrix components follows the same mechanisms. The effect of MWs on chemical or biochemical reactions is considered generally strictly

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thermal (Chemat et al., 2009), but this point is a contentious issue. Some studies relate indeed to the nonthermal effects of MWs. This point is addressed in Section 17.7. MWs have the particularity of instantaneously heating polar substances such as water. Under the effect of EMWs the intracellular liquid heats up. This sudden increase in temperature implies an increase of internal pressure and generates the bursting of the cell walls. It follows the release of the metabolites of interest. In food products, it is mainly water molecules that are concerned by this phenomenon, but many other polar molecules also absorb MWs (alcohol, sugars, amino acids, etc.). Thus MW extraction without addition of solvent is possible induced by the deterioration of cellular membranes under the effect of rapid temperature elevation. As a consequence, MAE can be divided into two main categories that are MWassisted solvent extraction (MASE) and solvent-free MW extraction. Falling into these categories, one finds several derived techniques that are listed in Table 17.4 using two different methods: G

G

distillation that is used for separating the constituents of a mixture by boiling and hydrodiffusion that consists of heating a product without addition of solvent and in recovering the condensed vapor containing the extract by gravity.

17.6.2.1 Influencing factors A lot of variables influence MAE, such as MW power output, exposure time, sample size, product moisture, solvent viscosity, and the type of solvent as well as a solvent-to-solid ratio (Luque de Castro & Castillo-Peinado, 2016; Vinatoru, Mason, & Calinescu, 2017). The rate of temperature increases depending on the MW power and the dielectric loss factor of the material being irradiated (Zill-E-Huma, 2010). A rapid temperature increase represents a huge advantage because high temperatures (.90 C) might inhibit enzymes activity and consequently molecules oxidation. Processing time has to be controlled to avoid the degradation of thermolabile compounds. For optimal extraction a balanced combination of moderate ε0 to promote the penetration of wave in the product and high loss (maximum εv) is required. The temperature dependence of the factor loss causes an increase of the penetration with temperature (water, f 5 2.45 GHz: T 5 25 C, Dp 5 3.4 cm; T 5 95 C, Dp 5 14 cm) (Datta, 2001).

17.6.3 Microwave-assisted extraction techniques This first use of MWs in the field of extraction by Ganzler et al. (1986) marked the beginning of an expansion. The following different processes have been developed in order to counteract the limitations of conventional extraction techniques. These innovative techniques can use solvents (MASE) (Pare´, 1992), water (MAD: hydrodistillation by MWs) (Stashenko, Jaramillo, & Martı´nez, 2004), or directly

Table 17.4 Classification of extraction techniques and some examples of application. Type of extraction

Acronym of the technique

Principle

Vegetable matrix

Targeted compounds

Industrial or laboratory scale

References

Solvent extraction

MASE

Diffusion between a solvent and a matrix Vacuum MASE

Tomato, olive pomace oil

Phenolic acids and flavonoı¨ds, carotenoı¨ds Lipids

Lab; batch

Tomato: Pinela et al. (2016)Olive pomace oil: Yank (2017)

Lab; batch

Oil

Lab; batch

Meullemiestre, Breil, Abert-Vian, and Chemat (2016) Virot, Tomao, Colnagui, Visinoni, and Chemat (2007)

Lippia sidoides Cham leaves

Essential oils

Lab; batch

Cinnamomum

Essential oils

Lab; batch

Cassia bark Lavandin

Essential oils Essential oils

Lab; batch Lab; batch

ARCHIMEX Pe´rino-Issartier, Ginies, Cravotto, and Chemat (2013)

Orange peels

Essential oils

Lab; batch

Farhat et al. (2011)

VMASE

MISE

Distillation

CAMD

MWHD

VMHD MASD

Hydrodiffusion

MSDf

Soxhlet extraction combined with MW Addition of compressed air Hydrodistillation combined with MW Vacuum MWHD Steam distillation combined with MW MASD but steam injection by the top of the reactor

Oleaginous Yarrowia lipolytica Olive seeds

Craveiro, Matos, Alencar, and Plumel (1989) Jeyaratnam et al. (2016)

Solvent free

Distillation

SFME

VSFME

ISFME

Hydrodiffusion

MHG

VMHG

Similar to MWHD without an addition of the solvent Solvent-free VMHD (sequential vacuum between 100 and 200 mbar) SFME with the addition of material absorbing MW (graphic powders or ionic liquids) Recover extract by gravity (mixture of HE and internal water of matrix) Vacuum MHG

Sea bucktthorn

Polyphenols, HE

Lab; batch

Perino-Issartier, AbertVian, and Chemat (2011)

Lavandin

Essential oils

Lab; batch

Pe´rino-Issartier et al. (2013)

Zingiber officinale Rosc.

Essential oils

Lab; batch

Wang et al. (2006)

Broccoli; lettuce

Essential oils

Lab; batch industrial

Onion

Flavonoids

Ferreira, Passos, Cardoso, Wessel, and Coimbra (2018); Pe´rino, Pierson, Ruiz, Cravotto, and Chemat (2016) Abert-Vian, Elmaataoui, and Chemat (2011)

CAMD, Compressed air microwave distillation; ISFME, improved solvent-free microwave extraction; MASD, microwave-assisted steam distillation; MASE, microwave-assisted solvent extraction; MHG, microwave hydrodiffusion and gravity; MISE, microwave-integrated Soxhlet extraction; MSDf, microwave steam diffusion; MWHD, microwave hydrodistillation; SFME, solvent-free microwave extraction; VMASE, vacuum microwave-assisted solvent extraction; VMHD, vacuum microwave hydrodistillation; VMHG, vacuum microwave hydrodiffusion and gravity; VSFME, vacuum solvent-free microwave extraction.

480

Green Food Processing Techniques

intracellular water of the plant (SFME) (Lucchesi, Chemat, & Smadja, 2004). They can also use gravity [MW hydrodiffusion and gravity (MHG)] (Vian, Fernandez, Visinoni, & Chemat, 2008), use in combination water vapor (MSD) (Farhat, Ginies, Romdhane, & Chemat, 2009), and combine Soxhlet (Virot, Tomao, Ginies, Visinoni, & Chemat, 2008) or Dean
Stark method (Veillet, Tomao, Ruiz, & Chemat, 2010). Other techniques are emerging consisting of superimposing another physical mechanism to these various extraction methods (vacuum, addition of water vapor, addition of extraction cycles, ultrasounds, centrifuge force, etc.). The extraction methods depend highly on the properties of the extracted compound. Extraction proceeds, generally, as follows. The sample is loaded into a support and in the case where an extraction solvent is present, it is added until immersion of the sample. It is heated until the explosion of its cells using MWs. The vapors are then condensed, and the extract is recovered in a suitable container (florentine vase, balloon, Erlenmeyer flask, etc.). The major MW extraction techniques are listed in Table 17.4.

17.6.3.1 Advantages of microwave-assisted extraction over conventional techniques Specificity of dielectric heating provides MW extraction with many interesting features compared to conventional methods. In many comparative studies the advantages of MW extraction were underlined, such as a gain of extraction time, a high quality of product obtained combined with a gain of energy. Some examples are exposed in the following. MAE with solvent (ethanol/water/TFA) method was used and compared with a CSE technique to yield anthocyanins from Morus nigra L. (MN) (Koyu, Kazan, Demir, Haznedaroglu, & Yesil-Celiktas, 2018). The MW procedure showed a higher yield of anthocyanins from MN with an MW power between 300 and 500 W and extraction times up to 10 min. However, a remarkable decline was observed in anthocyanins content after 15 min of extraction indicated that the prolonged temperature exposition might cause reduction in targeted bioactive metabolites. Furthermore, total phenol, anthocyanin (12.63 mg/g cya-3-glu equiv. anthocyanins), and tyrosinase inhibitory activity (IC50 value of 1.60 mg/mL) were better compared to the values obtained with solvent extraction (10.93 mg/g content and IC50 of 2.81 mg/mL, respectively), whereas similar results were attained for flavonoid content. Koyu et al. (2018) concluded that the superiority of MAE over conventional systems was majorly explained with the shortening of process time that limits the degradation of active components. A reduction of extraction time from 300 to 10 min and a solid-to-solvent ratio from 1:60 to 1:10 were observed. Moreover, these parameters allowed to halve the tyrosinase inhibitory activity. Pandey and Shrivastava (2018) exploited a two-step MAE (TSMAE) to enhance oil yield from rice bran. This technique consists of treating a vegetable matrix in an MW oven at a selected power time followed by solvent washing outside the MW oven (first step). Then the rice bran was again placed in MW oven and the first step was repeated. In this study the total oil content of rice bran as obtained from

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Soxhlet extraction was found to be 162.8 6 0.76 mg/g (extraction time: 4 h). With TSMAE, more oil was recovered (B97%) in shorter extraction time (8
10 min). Furthermore, the phospholipid content of oil and peroxide value in TSMAE were found to be significantly lower than the CSE method (0.64 6 0.11% vs 1.02 6 0.15%). This result is explained by the longer extraction time in CSE compared to TSMAE during which more phospholipids were extracted from the cell membranes. It can be observed that in CSE more than 95% of oil was recovered after 20 min, whereas the same quantity could be recovered in ,10 min in TSMAE. Moreover, oil quality obtained from TSMAE process was superior as oil obtained by CSE, and there was no significant difference in the overall change in color between the oil extracted by MW and solvent extraction. As a final example, MHG dehydration extraction technique was used to recover phenolic compounds and polysaccharides from broccoli (Ferreira et al., 2018) and to dehydrate broccoli. This technique was compared with hot water extraction. For dehydration purposes (drying), MHG allowed to drop the moisture of broccoli byproducts down to 12% without affecting polysaccharides and protein content. The washed-out solutes obtained by MHG represented only 4.4% per dry weight of broccoli by-products indicating that the most bioactive compounds of broccoli matrix are still present in dried by-product. Furthermore, a total of 76% of pectic polysaccharides were extracted by MHG dehydration technique as compared to 60% with hot water extraction. The authors point out another advantages, such as filtration and concentration steps, are not required unlike with aqueous/solvent extractions. According to Ferreira et al. (2018), MHG technology has also potential for the valorization of industrial by-products. In this study the combined MHG extracts were used to cook up a bechamel sauce where the added water is replaced by the aqueous extract of broccoli. The purpose was to enrich the sauce with bioactive compounds extracted from broccoli. The authors did not notice any taste modification, and the characteristics of bechamel sauce were maintained. To say a few words about energy consumption, Zill-E-Huma (2010) compared two extractions techniques, such as Soxhlet (conventional extraction) and MWintegrated Soxhlet (MIS) extraction for the extraction of compounds from different varieties of onions. Combined with a marked reduction of extraction time, the author measured an energy consumption of 8 kW h for Soxhlet extraction and of 0.5 kW h for MIS.

17.7

Environmental impact

17.7.1 Introduction More than 130 million MW systems are affected the EU legislation that focuses on their life cycle. Nevertheless, there is little information on the environmental impacts (eutrophication and acidification of natural systems, primary energy demand, global warming, ozone layer depletion, etc.) of the entire life cycle of MW

482

Green Food Processing Techniques

systems. A recent paper (Gallego-Schmid, Mendoza, & Azapagic, 2018) gives the results of a comprehensive environmental evaluation of MW systems across the whole life cycle and claims that the electricity consumption is the main contributor to the environmental impacts. The manufacturing of MWs and the end-of-life disposal have also a relevant contribution and promote eco design. Some user practices are encouraged, for example, the adjustment of heating time to each type of material. The evaluation of environmental impacts requires a rigorous and standardized methodology. A recognized methodology is life cycle assessment (LCA) defined by ISO 14040/44 as the “compilation and evaluation of the inputs, outputs and potential environmental impacts of a product system throughout its life cycle” (ISO, 2006a, 2006b; Bisinella de Faria, Spe´randio, Ahmadi, & Tiruta-Barna, 2015). LCA enables calculating the environmental impacts of a product, process, or service over its entire life cycle (from cradle to grave) or for limited boundaries of the life cycle system, for example, cradle to gate (from natural resources to the output of the plant). The environmental impacts are classified in different impact categories (e.g., climate change, resource depletion, and human health.) and are assessed quantitatively starting from the life cycle inventory (LCI) of the system (natural resources consumption and hazardous substance emissions toward environment) and using specific impact assessment methods. The studied products and processes have to be comparable in order to derive consistent (unbiased) results, that is, they have to fulfill the same function or to respond to the same need on the market. Some classical approaches assess this comparison according to mean values. In the case of food processes the resulting outputs from alternative processes may have different composition, nature, and quality, and consequently, innovative approaches have to be considered. New LCA approach offers the capability to analyze the environmental performances of an industrial process at different levels, that is, for the unit processes, background life cycle processes, distinct periods, or the whole life of a plant, etc. It shall demonstrate the impact of a new unit in the overall process, in comparison with the classical process at a scale, close to the industrial unit. The proof of concept of this new LCA approach has already been validated in the field of water treatment processes (Bisinella de Faria et al., 2015; Mery, Tiruta-Barna, Benetto, & Baudin, 2013). The environmental impact determination of MW technology in food processing is generally few documented, and there is a lack of data to have a global view on the environmental impact of MW technology comparing to other technologies used classically in food industry. In this chapter, we propose to describe the methodology to compare the environmental impact of implementation of targeted processes comparing to classical ones, illustrated by some examples found in literature comparing MW applications in food industry. The methodology is applied in four steps, they are as follows: (1) the definition of goal and scope, (2) the building of LCI, (3) the life cycle impact assessment, and (4) the interpretation of results.

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17.7.2 Goal and scope The goal of the study must be specified including the following aspects. Table 17.5 gives some examples of “expression of the need” for comparison of MW operations to conventional techniques.

17.7.2.1 Life cycle inventory By definition, LCI is the compilation and quantification of all natural resources consumed and all substances emitted into environment by the life cycle system (emissions and resources). LCIs are traditionally based on the average data of material and energy inputs and outputs collected on industrial site or estimated from literature or from modeling studies performed prior to the LCA study. In order to build an LCI, all inputs and outputs of each process must be quantified, and all processes of the life cycle system must be considered. The process should be placed at an industrial scale such that the modeled system is as close as possible to a real industrial process. In the case of ongoing development and low technology readiness level (TRL) of a new process, a scale-up modeling should be performed in order to calculate material and energy flows for the desired real scale. The LCI step is the most important in terms of invested work and time, and also the most influencing on the final results. Table 17.6 gives one example for case number D (Table 17.5) comparing MW process (D1) to reference process (D2) to illustrate the methodology highlighting that a homemade meal made from conventional ingredients and cooked in an MW could be a better option than a frozen ready-made meal made from frozen ingredients heated in an electrical oven, considering the life cycle and environmental impacts. Other examples could be found in MW drying, defrosting (tempering), bleaching, pasteurization/ sterilization, and extraction in comparison to conventional techniques; but it is difficult to find fully documented comparison in literature, especially at industrial scale. However, these findings could be useful to inform both producers and consumers on how their choices influence costs and environmental impacts of food. The study could be further investigated by “pushing the boundaries,” considering a complete environmental evaluation of the MWs across the whole life cycle in Europe, considering the production of materials, packaging, manufacturing of MWs, distribution, use of electricity, end-of-life waste treatment for an MW oven (Gallego-Schmid et al., 2018).

17.7.2.2 Life cycle impact assessment In this step the LCI is converted in environmental impacts by impact category. There are many impact categories following the environmental problems and damages of concern, for example, climate change, human toxicity, respiratory effects, ozone layer depletion, acidification, eutrophication, natural resources depletion, etc. Each substance in LCI is responsible to at least one impact category, for example, NOx emitted in air are responsible for respiratory effects, acidification, and eutrophication.

Table 17.5 The fundamental aspects of life cycle assessment evaluation of microwave (MW) processes in comparison to classical ones. Case number

Process investigated (1)

Reference process (2)

Process function

Reference unit

Boundaries of life cycle system

Process location

Reference

A

MW drying

Oven drying and vacuum drying

Drying rate for 1 kg of water evaporated

Olive leaves

Turkey

Elhussein and Sahin ¸ (2018)

B

MW Defrosting and tempering

Hot air defrosting

Beef meat (1 kg or 1 ton)

Ireland

Farag, Lyng, Morgan, and Cronin (2008)

C

MW bleaching

Immersion in boiling water

Temperature increase until 0 C in the whole unit, without ice traces Highest scores in color intensity

Modelization (14 empirical equations for drying behavior) Defrosting tunnels pilots

D

Homemade meal made from conventional ingredients and heated in an MW MW stabilization and conservation

Frozen ready-made meal made from frozen ingredients heated in the electric oven Freeze-drying

MW extraction (MISE)

Solvent extraction (soxlet)

E

F

Preparation and consumption of a meal of 360 g (roast dinner) for one person Preservation of the nutritional quality and color during 4 months of storage Yield of antioxidant (targeted value)

Brassica vegetables (broccoli, brussels sprout, etc.) Chicken meat and three vegetables (potatoes, carrots, and peas), and tomato sauce 15
45 kg of fresh mealworms

Lab tests

Worldwide

Guo, Sun, Cheng, and Han (2017)

Oven

Domestic (Home) in the United Kingdom

Rivera and Azapagic (2016)

Pilot and industrial dryers

Belgium

Lenaerts, Van Der Borght, Callens, and Van Campenhout (2018)

Plants (onions)

Lab/Batch

France

Zill-E-Huma (2010)

Table 17.6 Life cycle inventory for case number D (see Table 17.5). Case number

D1

D2

Resources (input)

Emissions (outputs)

Power

Water (process)

Raw materials (e.g., chemicals)

Others (e.g., transportation)

Gas (e.g., CO2, NOx, SOx, VOC)

Wastewater

Solid wastes

Others (e.g., packaging)

0.39 kW h/ meal

Water for preprocessing: 1.36 L Steam: 54 kJ

Transportation: 79.3 km kg (regional distribution center for products)

Natural gas— distribution: (20 kJ) Preprocessing (54 kJ)

Wastewater: 4.05 L

Food waste: 120 g Waste transportation: 3.51 km kg Meat losses: 43 g Vegetable losses: 47 g

Plastic bag: 10 g Tin: 8 g Cardboard: 1.81 g LDPE: 10 g

2.03 kW h/ meal

Water for preprocessing: 1.46 L Steam: 58 kJ Water for manufacturing: 4.4 L

151 g chicken 110 g potatoes, 44 g carrots, 44 g peas, 36 g onions, 44 g tomato paste, 1 g salt, and 9 g vegetable oil 162 g chicken, 125 g potatoes, 50 g carrots, 50 g peas, 40 g onions, 53 g tomato paste, 1 g salt, 9 g vegetable oil

Transportation: 87.6 km kg (regional distribution center for products) 40 mL fuel oil for manufacturing

Natural gas— preprocessing (59 kJ)

Wastewater: 0.9 L for consumption Wastewater for manufacturing: 3.96 L

Food waste: 86 g Waste transportation: 3.66 km kg Meat losses: 43 g Vegetable losses: 43 g

Plastic packaging: 45 g Cardboard: 22 g LDPE: 11 g PE: 36 g Steel: 6 g

LDPE, Low-density polyethylene; VOC, volatil organic compound.

486

Green Food Processing Techniques

Environmental models were used to determine specific parameters named characterization factors (CFs) that quantify the effect of a substance in a given impact category. The impact result is proportionally linked to the mass of the emitted substance by using CFs as proportionality constants. For a given substance s the obtained impact value (I) of a given impact category k is Is;i;k 5 gs;i CFs;I;k where index i represents the emission compartment (e.g., air, water), g represents the quantity of substance s in the LCI, and CF is the characterization factor for that substance emitted in compartment I, for the impact category k. Fortunately, it is not necessary to calculate these CFs since they are available with LCA software and on Ecoinvent database website. Moreover, many impact calculation methods currently exist, which delivers CF based on various environmental modeling approaches and hypotheses, for example, ReCiPe (Bisinella de Faria et al., 2015) and Impact2002 1 (Mery et al., 2013) for cite the most currently used ones. The complete analyses of LCA and LCI, fully completed by data provided by tests at pilot and industrial scales, are necessary to have a good overview of environmental gains brought by the replacement of classical technology by a new one.

17.7.2.3 Results interpretation In this last step the impact calculation results are analyzed, and the information is structured in order to obtain a fully understanding of the studied system. LCA results are of multicriteria as many environmental impact categories are calculated. Mainly two kinds of information can be derived from a usual LCA application, which are as follows: Comparison of several alternatives, that is, comparison of a new process with a reference one Identification of hot spots of a process life cycle system, that is identification of the part of a system where the impacts are generated and the substances in question. These interpretations can be done at the level of each impact category (this is the best way of interpretation) and at the level of aggregated impact results when the method permits to calculate a single indicator by regrouping all impact categories. This last option is less relevant since the aggregation of all impact categories is source of information loss and distortion.

17.8

Regulation and security

As presented earlier, MWs are used in many food applications. This utilization implies specific risks that need to be defined and controlled. To ensure a safe production in food industry, various methods exist to identify the occurrence of

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possible risks (Mortimore & Wallace, 2013). The concepts of HACCP (hazard analysis and critical control points) and HAZOP (hazard and operability analysis) are used to ensure food safety and to optimize the efficiency and risks management related to manufacturing, staff, and environment.

17.8.1 Hazard analysis and critical control points approach 17.8.1.1 Principles The HACCP system is depending on the process control of food processing, it is established on the basis of food safety programs. With such a system, known hazards according to a process can be prevented and reduced to an acceptable level. This method ensures food safety and hygiene at all levels of production by applying a hazard assessment methodology (Datta and Davidson, n.d.; Mortimore & Wallace, 2013) HACCP system is based on seven principles. It has been defined by directive 43/93/EEC of 14/06/1993 now converted as part of food in EC Regulation 852/2004 (Ayappa et al., 1991; Chemat & Cravotto, 2013).

17.8.1.2 Application of hazard analysis and critical control points system to microwave technology—evaluation of risks The chemical hazards involved during an MW process are the appearance of dangerous chemical compounds, such as acrolein, acrylamide, or heterocycles amines. Furthermore, other chemicals, such as the carcinogen DEHA [bis(2-ethylhexyl) adipate] found in polyvinyl chloride films can migrate from packaging into food during MW treatment. However, the amount of this substance is not significant, except for certain conditions (Hill, 1998; Schubert & Regier, 2005). Microbial hazards are one of the main concerns for food industry. Indeed, raw materials may contain microorganisms and pathogens. According to storage conditions, the risk of pathogen exposition for consumers can increase. To avoid a crosscontamination problem, MW machines used for food processes have to be cleaned properly, disinfected, and rinsed. Finally, packaging line, storage conditions, and hygiene staff must be controlled properly to prevent recontamination.

17.8.1.3 Hazard and operability analysis approach The HAZOP method allows to control the identifiable hazards that may be harmful to personnel, environment, and processing operations or equipment. The investigation consists of examining potential deviations of operations from defined conditions that could create process-operating problems and hazards (Rossing, Lind, Jensen, & Jørgensen, 2010). It is designed in order to optimize the food process and to obtain a better performance. The HAZOP system is based on eight principles. HAZOP system can be used to complete HACCP program.

488

Green Food Processing Techniques

17.8.1.4 Using of hazard analysis and critical control points and hazard and operability analysis systems in food industry To ensure food and staff safety, HACCP and HAZOP methods have to be applied correctly during MW processes. HACCP allows to determine physical, chemical, and biological hazards on food safety, and HAZOP is employed to identify necessary actions to ensure staff and material safety. Frequency, power, and treatment time of MWs are linked to HACCP method. The process and electromagnetic field exposition issues are linked to HAZOP system (Perino & Chemat, 2015).

17.8.1.5 Quality assurance in microwave food processing In MW food processing, few reviews exist on quality assurance. Many aspects are examined by Atuonwu and Tassou (2018), concerning the effects of MWs on food products. Thermal effects can be evaluated in term of the inactivation of microorganisms/enzymes and degradation of relevant nutritional and sensory quality variables. Nonthermal effects are still a subject of intense debate (Chandrasekaran et al., 2013). The major question is to determine if MWs can have an effect on molecules or not. Most scientists agree that the energy of the MW photon is far too low to directly cleave molecular bonds (Kappe, Pieber, & Dallinger, 2013). In many cases, experimental artifacts were mainly a consequence of erroneous temperature measurements of the product. Other studies (de la Hoz, Dı´az-Ortiz, & Moreno, 2005) show that the effect of electromagnetic field has not been elucidated conclusively. It is a very complex irradiation involving thermal (hot spots, superheating) and nonthermal (molecular mobility, field stabilization) effects. The absence of heating uniformity is partially responsible of the limited application of MW heating in food industry (Atuonwu & Tassou, 2018).

17.8.1.6 Microwave oven safety Nowadays, MWs oven is an indispensable tool present in every kitchen. It is rapid for reheating food. However, some questions may be raised linked to food safety such as microbiological hazards. A study was carried out by (New et al., 2017), to gauge the knowledge and practice of MW oven of Malaysian consumers. The result revealed that consumers have not a deep knowledge of how to use MW oven. For the betterment of the public health the knowledge on MW oven safety has to be improved and integrated in the food safety educational programs. Consumers of MW oven have to use MW-safe cookware because certain plastic containers are not advisable to be used with MW. Indeed, some plastic additives could be migrated into the food at high temperatures. In some cases, damage of MW oven can occur if consumers use metal cookware of aluminum foil and arcing (sparks) can be observed.

Microwave technology for food applications

17.9

489

Upscaling and its applications in industry

Several industrial applications use MWs around the world for food applications, such as drying, thawing, cooking, blanching, pasteurization, or sterilization as described earlier. The following examples in food processing have been provided by SAIREM SAS (Neyron, France) that has 40 years of experience in MW and RF engineering, bespoke electronic design, application development, process design, and production of a standardized range of MW generators. Table 17.7 shows that MW-assisted processes have a very short processing time, allow continuous mode operation, and present economic advantages, in most of the cases, as compared to conventional processes. Nowadays, the world’s largest market for MWs and high frequency is tempering of frozen blocks (meat, poultry, fish, seafood, butter, fruits, and vegetables). But other domains using MW food processes are in development, such as in pasteurization, debacterization, disinsectization, and liquid treatment. MW can be used for liquid treatment and pumpable products such as marmelade before potting (2 tons/h). The process can be used in continuous way. Another application is the disinsectization of dry products (dried fruits, flour, semolina, etc.). MWs have a major advantage compared to other conventional techniques (steam, CO2, freezing): the process is adapted to product packaged in bags of 1
25 kg and can be applied in very short times in continuous operation. Concerning MAE, the field is under development, a lot of devices at laboratory scale exist and some at industrial scale. Archimex, SAIREM, and Milestone are some companies, which develop new MW extraction systems.

17.10

Future trends

In the early 1980s, future trends for MW use were to develop this technology very shortly in most of food industries. It was maintained in the 1990s. From years 2000 the evolution of MW technology is more considered a part of a process. Most of publications include MW systems as a part of complex processes. It is considered a mean of improving existing process by reducing time, increasing or maintaining the quality product, or sometimes reducing energy costs. Nowadays, despite the fact that the first industrial applications date back many years, most of textbooks treating of MWs industrial techniques underline the needs of research effort. MWs sources will benefit in the developments of semiconductors manufacturing, which have led to solid-state MW generators showing many advantages compared to magnetrons (Schubert & Regier, 2005). The complex phenomena involved in the conversion of electromagnetic energy into heat, in a heterogeneous media, explain the need of improvement of numerical tools to simulate both electric and temperature fields in the product. Accurate simulations will help the design of MW devices and will contribute to operate MWs in optimized conditions improving the quality of the product (mitigating the nonheating uniformity, for example). For energy intensive processes as drying the advantages of dielectric heating should lead to the emergence, in industry, of combined techniques involving MWs.

Table 17.7 Examples of industrial microwave applications. Applications

Product

Microwave device

Capacity—energy consumption

Time

Electric coast

Microwave tempering

Frozen blocks (meal, poultry, fish, seafood, butter, fruits, and vegetables)

TM150 Power: 75 kW

2
3 tons/h from 220 C to 24 C/ 2 2 C Energy: 100 kVA/h

5
10 min from 220 C to 24 C/ 2 2 C

3
4 euros/tons

9
12 euros/ton

Preheating (from 110 C to 170 C)

Spring rolls

Power: 40 kW

5000 spring rolls/h Energy: 60 kVA/h

Continuous cooking

Ham, sausage

High frequency: 50 kW Continuous cooking

500
600 kg/h

Between 48 and 72 h for 20 cm thick blocks Between 8 and 12 h for 8 cm thick blocks 1 min before prefrying in oil Advantage (only 2 min in oil instead of 6 min: less oil in final product and oil economy) 1
2 min

Classical tempering (thawing room)

Classical cooking (cooking room)

1
2 h

6 euros/h

1.50 euro for 100 kg/h

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Acknowledgments The authors are grateful to FEDER as well as Nouvelle Aquitaine Region for supporting this work. Special thanks to Ligia Barna for the discussions about the environmental impact assessment methodology.

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64. Available from https://doi.org/10.1016/j.jfoodeng.2017.01.003. Perino, S., & Chemat, F. (2015). Chauffage micro-ondes comme e´co-proce´de´ en industrie agroalimentaire. Pe´rino, S., Pierson, J. T., Ruiz, K., Cravotto, G., & Chemat, F. (2016). Laboratory to pilot scale: Microwave extraction for polyphenols lettuce. Food Chemistry, 204, 108
114. Available from https://doi.org/10.1016/j.foodchem.2016.02.088. Perino-Issartier, S., Abert-Vian, M., & Chemat, F. (2011). Solvent free microwave-assisted extraction of antioxidants from sea buckthorn (Hippophae rhamnoides) food byproducts,. Food and Bioprocess Technology, 4, 1020
1028. Pe´rino-Issartier, S., Ginies, C., Cravotto, G., & Chemat, F. (2013). A comparison of essential oils obtained from lavandin via different extraction processes: Ultrasound, microwave, turbohydrodistillation, steam and hydrodistillation. Journal of Chromatography A, 1305, 41
47. Perino-Issartier, S., Maingonnat, J.-F., & Chemat, F. (2010). Chapter 11: Microwave food processing. In Alternatives to conventional food processing (pp. 415
458). doi:10.1039/ 9781849730976-00415. Pert, E., Carmel, Y., Birnboim, A., Olorunyolemi, T., Gershon, D., Calame, J., . . . Wilson, O. C. (2001). Temperature measurements during microwave processing: The significance of thermocouple effects. Journal of the American Ceramic Society, 84, 1981
1986. Available from https://doi.org/10.1111/j.1151-2916.2001.tb00946.x. Pham, Q. T. (2014). Modelling coupled phenomena. In Q. T. Pham (Ed.), Food freezing and thawing calculations (pp. 95
131). New York: Springer New York. Available from http://doi.org/10.1007/978-1-4939-0557-7_6.

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Pinela, J., Prieto, M. A., Carvalho, A. M., Barreiro, M. F., Oliveira, M. B. P., Barros, L., & Ferreira, I. C. (2016). Microwave-assisted extraction of phenolic acids and flavonoids and production of antioxidant ingredients from tomato: A nutraceutical-oriented optimization study. Separation and Purification Technology, 164, 114
124. Poux, M., Estel, L., Len, C. (2016). Micro-ondes en synthe`se organique (p. 17). Pupan, N., Dhamvithee, P., Jangchud, A., & Boonbumrung, S. (2018). Influences of different freezing and thawing methods on the physico-chemical, flavor, and sensory properties of durian puree (cv. Monthong). Journal of Food Processing and Preservation, 42, e13669. Available from https://doi.org/10.1111/jfpp.13669. Reader, H. C. (2006). Understanding microwave heating systems: A perspective on state-ofthe-art. Advances in microwave and radio frequency processing (pp. 3
14). Berlin, Heidelberg: Springer. Available from http://doi.org/10.1007/978-3-540-32944-2_1. ´ Re˛kas, A., Scibisz, I., Siger, A., & Wroniak, M. (2017). The effect of microwave pretreatment of seeds on the stability and degradation kinetics of phenolic compounds in rapeseed oil during long-term storage. Food Chemistry, 222, 43
52. Available from https:// doi.org/10.1016/j.foodchem.2016.12.003. Reverte-Ors, J. D., Pedren˜o-Molina, J. L., Ferna´ndez, P. S., Lozano-Guerrero, A. J., Periago, P. M., & Dı´az-Morcillo, A. (2017). A novel technique for sterilization using a power self-regulated single-mode microwave cavity. Sensors, 17, 1309. Available from https:// doi.org/10.3390/s17061309. Rivera, X. C. S., & Azapagic, A. (2016). Life cycle costs and environmental impacts of production and consumption of ready and home-made meals. Journal of Cleaner Production, 112, 214
228. Available from https://doi.org/10.1016/j.jclepro.2015.07.111. Rossing, N. L., Lind, M., Jensen, N., & Jørgensen, S. B. (2010). A functional HAZOP methodology. Computers & Chemical Engineering, 34, 244
253. Roussy, G., Rochas, J. -F., & Oberlin, C. (2003). Chauffage die´lectrique
Principes et spe´cificite´s, Ref : TIP302WEB
“Re´seaux e´lectriques et applications.” ,/base-documentaire/energies-th4/electrothermie-industrielle-42270210/chauffage-dielectrique-d5940/. Accessed 23.07.18. Salim, N. S. M., Garie´py, Y., & Raghavan, V. (2017). Hot air drying and microwave-assisted hot air drying of broccoli stalk slices (Brassica oleracea L. Var. Italica). Journal of Food Processing and Preservation, 41, e12905. Available from https://doi.org/10.1111/ jfpp.12905. Sarah, M., Madinah, I., & Salamah, S. (2018). Optimization of palm fruit sterilization by microwave irradiation using response surface methodology. IOP Conference Series: Materials Science and Engineering, 309, 012074. Available from https://doi.org/ 10.1088/1757-899X/309/1/012074. Satpathy, S. K., Tabil, L. G., Meda, V., Naik, S. N., & Prasad, R. (2014). Torrefaction of wheat and barley straw after microwave heating. Fuel, 124, 269
278. Available from https://doi.org/10.1016/j.fuel.2014.01.102. Schubert, H., & Regier, M. (2005). The microwave processing of foods. Elsevier Ltd. Available from http://doi.org/10.1533/9781845690212. Siguemoto, E´. S., & Gut, J. A. W. (2016). Dielectric properties of cloudy apple juices relevant to microwave pasteurization. Food and Bioprocess Technology, 9, 1345
1357. Available from https://doi.org/10.1007/s11947-016-1723-0. Singh, R. D., Bhuyan, K., Banerjee, J., Muir, J., & Arora, A. (2017). Hydrothermal and microwave assisted alkali pretreatment for fractionation of arecanut husk. Industrial Crops and Products, 102, 65
74. Available from https://doi.org/10.1016/j. indcrop.2017.03.017.

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497

Song, C., Wang, Y., Wang, S., & Cui, Z. (2016). Temperature and moisture dependent dielectric properties of Chinese steamed bread using mixture equations related to microwave heating. International Journal of Food Properties, 19, 2522
2535. Available from https://doi.org/10.1080/10942912.2015.1104508. Stashenko, E. E., Jaramillo, B. E., & Martı´nez, J. R. (2004). Comparison of different extraction methods for the analysis of volatile secondary metabolites of Lippia alba (Mill.) NE Brown, grown in Colombia, and evaluation of its in vitro antioxidant activity. Journal of Chromatography A, 1025, 93
103. Su, Y., Zhang, M., Zhang, W., Liu, C., & Adhikari, B. (2018). Ultrasonic microwaveassisted vacuum frying technique as a novel frying method for potato chips at low frying temperature. Food and Bioproducts Processing, 108, 95
104. Available from https:// doi.org/10.1016/j.fbp.2018.02.001. Taher, B. J., & Farid, M. M. (2001). Cyclic microwave thawing of frozen meat: experimental and theoretical investigation. Chemical Engineering and Processing: Process Intensification, 40, 379
389. Available from https://doi.org/10.1016/S0255-2701(01)00118-0. Tang, Z., Mikhaylenko, G., Liu, F., Mah, J.-H., Pandit, R., Younce, F., & Tang, J. (2008). Microwave sterilization of sliced beef in gravy in 7-oz trays. Journal of Food Engineering, 89, 375
383. Available from https://doi.org/10.1016/j. jfoodeng.2008.04.025. Turner, I. W., Puiggali, J. R., & Jomaa, W. (1998). A numerical investigation of combined microwave and convective drying of a hygroscopic porous material: a study based on pine wood. Chemical Engineering Research and Design, 76, 193
209. Available from https://doi.org/10.1205/026387698524622. Veillet, S., Tomao, V., Ruiz, K., & Chemat, F. (2010). Green procedure using limonene in the Dean
Stark apparatus for moisture determination in food products. Analytica Chimica Acta, 674, 49
52. Veldsink, J. W., Muuse, B. G., Meijer, M. M., Cuperus, F. P., van de Sande, R. L., & van Putte, K. P. (1999). Heat pretreatment of oilseeds: Effect on oil quality. Lipid/Fett, 101, 244
248. Vian, M. A., Fernandez, X., Visinoni, F., & Chemat, F. (2008). Microwave hydrodiffusion and gravity, a new technique for extraction of essential oils. Journal of Chromatography A, 1190, 14
17. Vinatoru, M., Mason, T. J., & Calinescu, I. (2017). Ultrasonically assisted extraction (UAE) and microwave assisted extraction (MAE) of functional compounds from plant materials. TrAC Trends in Analytical Chemistry, 97, 159
178. Available from https://doi.org/ 10.1016/j.trac.2017.09.002. Virot, M., Tomao, V., Colnagui, G., Visinoni, F., & Chemat, F. (2007). New microwaveintegrated Soxhlet extraction: An advantageous tool for the extraction of lipids from food products. Journal of Chromatography A, 1174, 138
144. Virot, M., Tomao, V., Ginies, C., Visinoni, F., & Chemat, F. (2008). Microwave-integrated extraction of total fats and oils. Journal of Chromatography A, 1196, 57
64. Wang, Z., Wang, L., Li, T., Zhou, X., Ding, L., Yu, Y., . . . Zhang, H. (2006). Rapid analysis of the essential oils from dried Illicium verum Hook. f. and Zingiber officinale Rosc. by improved solvent-free microwave extraction with three types of microwave-absorption medium. Analytical and Bioanalytical Chemistry, 386, 1863
1868. Wroniak, M., Re˛kas, A., Siger, A., & Janowicz, M. (2016). Microwave pretreatment effects on the changes in seeds microstructure, chemical composition and oxidative stability of rapeseed oil. LWT—Food Science and Technology., 68, 634
641. Available from https://doi.org/10.1016/j.lwt.2016.01.013.

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Yank, D. K. (2017). Alternative to traditional olive pomace oil extraction systems: Microwave-assisted solvent extraction of oil from wet olive pomace. LWT—Food Science and Technology, 77, 45
51. Zill-E-Huma, H. (2010). Microwave hydro-diffusion and gravity: A novel technique for antioxidants extraction (Ph.D. thesis). Universite´ d’Avignon.

Further reading Leybros, J., & Fremeaux, P. (1990). Extraction solide-liquide. I. Aspects the´oriques, Techniques de l’inge´nieur. Ge´nie Des Proce´de´s, 2, J2780
J2781. Penchev, P.I. (2010). E´tude des proce´de´s d’extraction et de purification de produits bioactifs a` partir de plantes par couplage de techniques se´paratives a` basses et hautes pressions.

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Laila Mandi1, Soukaina Hilali2, Farid Chemat3 and Ali Idlimam4 1 National Center for Studies and Research on Water and Energy, University Cadi Ayyad, Marrakech, Morocco, 2Faculty of Sciences Semlalia, University Cadi Ayyad, Marrakech, Morocco, 3Avignon University, INRA, UMR408, GREEN Extraction Team, Avignon, France, 4 Laboratory of Solar Energy and Medecinal Plants, Teacher’s Training College, Marrakech, Morocco

18.1

Instrumentation

18.1.1 Thermal solar energy The thermal energy in this case is gained through conversion of solar radiation. It has the ability to replace fossil fuels in many industrial processes such as food processing or extraction. Even though this is considered as a green and inexhaustible source, the radiation factor is not able to deliver energy at all time, making it hard to rely on such systems without supplementary source of energy. The operation of energy conversion systems requires solar thermal collectors as well as concentrators with specific characteristics and design according to the followed process with the ability to both accumulate and deliver solar radiation (Nkhonjera, Bello-Ochende, John, & King’ondu, 2017).

18.1.2 Photovoltaic energy Photovoltaic is defined as the direct conversion of solar rays into electricity with no heat engine help. Photovoltaic devices have stand-alone simple designs that can provide output from micro- to megawatts. Therefore they can be used as power plants or for multiple applications such as power source for a building, water pumping, communications, and even satellites (Parida, Iniyan, & Goic, 2011). They can also be used as a power source for food-processing devices such as the example of power rice husking (Uddin, Tasneem, Annie, & Salim, 2017).

Green Food Processing Techniques. DOI: https://doi.org/10.1016/B978-0-12-815353-6.00018-5 © 2019 Elsevier Inc. All rights reserved.

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18.2

Green Food Processing Techniques

Solar energy in food process engineering

In prehistoric ages, the competition of food urged the processing of food to preserve it for longer times. Nowadays, the processed foods that are flourishing in supermarkets are modern processed foods and traditional foods, but their manufacturing, processing, and packaging technologies have been advanced and rationalized to an incomparable extent. The principle aims of these technologies are to reduce the processing time, save energy, and improve the shelf life and quality of food products. Thermal technologies (radio frequency and microwave heating), vacuum cooling technology, high-pressure processing, pulsed electric field, and solar energy are those novel technologies who have potential for producing high-quality and safe food products, but current limitations related with high investment costs, full control of variables associated with the process operation, lack of regulatory approval, and importantly consumer acceptance have been delaying a wider implementation of these technologies at the industrial scale. In recent years, solar food processing represents an environmentally developed technique that provides a high food quality at an almost negligible or minimum cost; it has a very wide scope in food disinfection, shelf life allowance, drying, cooking, and substance quality improvement (Aravindh & Sreekumar, 2015). Solar food processing is not a new technique; in fact, this practice goes back to early ages with known process such as solar cooking and solar drying, in times when preservation was done by adding salt (Claflin & Schollers, 2012). There are a large number of potential applications of solar energy in food processing of which a number are discussed in Table 18.1.

18.3

Solar extraction

Extraction has been used probably since the discovery of fire. Egyptians and Phoenicians, Jews and Arabs, Indians and Chinese, Greeks and Romans, and even Mayas and Aztecs, all possessed innovative extraction and distillation processes used even for perfumes or food (Fig. 18.1). Nowadays extraction process is used in many industries such as food, cosmetics, pharmaceutics, neutraceutics, and bioenergy. Existing extraction technologies (such as maceration, solvent extraction, steam or hydrodistillation, cold pressing, or squeezing) have considerable technological and scientific bottlenecks to overcome: often requiring petroleum solvents and more than 70% of total process energy. These shortcomings have led to the consideration of the use of enhanced extraction techniques, which typically require less solvent and energy, such as solar extraction and/or distillation (Chemat & Strube, 2015). Many solar systems were developed to assure an efficient solar extraction process. Yen & Lin (2017) propose a solar extraction system composed of a solar-energy tube, solar cell as well as a sunlight shade coupled with a temperature controller to regulate the intensity of solar rays for an approximate extraction temperature of 100 C, and an essential oil collection unit with the following component: a collecting

Table 18.1 Examples of solar-energy applications in food processing. Application

Solar principle

Advantages

Products

References

Cooking

Uniform heat transfer

Less time Efficient

Sharaf (2002) Buddhi & Sahoo (1997)

Husking

Scheffler dish direct Scheffler dish indirect direct (via solar steam generation) Photovoltaic electricity

Short-time convenience of cooking in kitchen under shade, automatic sun tracking fast rate Decrease energy consumption attenuate health hazards and environmental impact Less time Improving quality Improving heat transfer Characteristic drying curve Cheapest method

Meat and legumes Rice, vegetables, meat, bake cakes Meat and vegetables Meals

Rice

Uddin et al. (2017)

Dehydrated products (fruits, vegetables, etc.) Medicinal plants Turmeric

Yaldy´z & Erteky´n (2001) Akpinar & Bicer (2008) Idlimam, Mohammed, Abdelkader, & Nabil (2016) Lakshmi, Muthukumar, Layek, & Nayak (2018) Atia, Mostafa, Abdel-Salam, & El-Nono (2011) & Caso, Fernandez, Franco, & Saravia (2008)

Drying

Uniform heat transfer Open sun

Pasteurization

Thermal energy

Efficient

Milk, water, and juices

Nahar (1990) Indora & Kandpal (2018)

502

Green Food Processing Techniques

Figure 18.1 Solar distillation and extraction of aromatic and medicinal plants (French, 1651).

bottle and a cooling tank with a thermoelectrical cooler. The energy for both regulating the temperature via the shading and cooling is delivered by a battery. Munir et al. (2014) proposed a different solar system for the processing of aromatic and medicinal plants composed of a parabolic reflector with an area of 8 m2 composed of mirrors with an electronic and mechanical system for the daily and seasonal monitoring of the sun which reflect the sun’s rays toward an aluminum secondary reflector, This frame is curved in such a way that it reflects the total radiation from the main reflector on the bottom of the distillation still; therefore, the secondary reflector is used as a conventional oven under the still. Kulurel & Tarhan (2016) proposed a similar solar apparatus also used for the essential oil distillation, which was composed of multiple compound parabolic solar collectors as well as a distillation unit. The solar collectors were used to transfer the heat from the heat transfer oil that was circulated by a pump from the solar collectors to the distillation water (Table 18.2).

18.4

Solar cooking

Cooking is a primary need and a major activity of every household and commercial places. Solar cookers represent smoke-free solutions for cooking used in order to reduce the consumption of firewood or conventional fuel and are well recognized by various national and international organizations (Table 18.3). Despite of numerous efforts, the widespread use of solar cookers has yet to become possible due to diverse reasons that include the impossibility of using the system during period that lacks sufficient radiation for cooking, high prices, the necessity of specific cooking tools (Nkhonjera et al., 2017). The characterization of solar cooker as well as their performance is a really complex and difficult task due to the variety of range of available cookers and their

Table 18.2 Solar extraction of aromatic and medicinal plants. Application

Matrix

Treatment conditions

Benefits (B) and disadvantages (D)

References

Essential oil extraction

Cymbopogon citrus

2 6 0.2 cm M 5 500 g Extraction T: 100 6 5 C Cooling T: 4 6 0.5 C

Yen & Lin (2017)

Essential oil extraction

Melissa Peppermint Rosemary Cumin (seed) Cloves (buds)

Essential oil extraction

Eucalyptus Peppermint leaves or Pinus Mentha piperita Mentha spicata

Melissa 5 11.6 kg Peppermint 5 9.1 kg Rosemary 5 3 kg Cumin 5 1.2 kg Cloves 5 0.8 kg Temperature range (300
450 C) S 5 8 m2 M 5 10 kg each S 5 10 m2

B: Similar extraction yields with hydrodistillation Citral extracted by solar energy is higher D: Needs additional energy B: The payback period is 2336 sunny hours Reducing fossil fuel consumption D: Needs solar tracking Direct solar radiation

B: Reducing fossil fuel consumption D: Needs solar tracking and additional source of energy B: No solar tracking D: Electricity is needed to operate the heat transfer oil pump Essential oil yield is lower than the one extracted by Neo Clevenger device

Afzal, Munir, Ghafoor, & Alvarado (2017)

Essential oil extraction

T: 22.21 C
29.53 C 1019
1148 W/m2 M 5 5 kg M (water) 5 7 kg

Munir et al. (2014)

Kulurel & Tarhan (2016)

Table 18.3 Comparison between modern and traditional cooking techniques. Traditional

Source of energy Efficiency Environmental impact References

Modern

Three-stones

Mud

Fired clay

Electric

Gas fuel

Liquid fuel

Solar cooker

Wood

Wood

Electricity

Low

Very high

Liquefied petroleum gas Very high

Kerosene/ ethanol . . . Very high

Solar rays

Very low

Wood and/or charcoal Low

Very high

Very high

Very high

Low

High

High

MacCarty, Still, & Ogle (2010)

Anozie, Bakare, Sonibare, & Oyebisi (2007)

Manibog (1984)

Anozie et al. (2007)

MacCarty et al. (2010)

MacCarty et al. (2010)

Time-variations of the efficiency Very low ¨ ztu¨rk (2004) O

Solar as sustainable energy for processing, preservation, and extraction

505

operation. They can be classified based on the used solar collector (Farjana, Huda, Mahmud, & Saidur, 2018) as shown in Table 18.4. They could also be classified based on both the types of cooking methodologies (Klemens & Da Silva, 2008) as presented in Table 18.5. Table 18.4 Classification of solar collectors. Solar collector

Description

Indicative temperature

References

Nonconvecting solar pond Cylindrical reflector

Stationary

300 , T , 360

Farjana et al. (2018)

Motion single-axis/solar tracking Stationary/motion single-axis/solar tracking Motion single-axis/solar tracking Motion single-axis/solar tracking Stationary Motion single-axis/solar tracking Motion single-axis/solar tracking

340 , T , 540

Farjana et al. (2018)

340 , T , 510, 340 , T , 560

Oommen & Jayaraman (2002)

340 , T , 540 340 , T , 560

Sonune & Philip (2003) Farjana et al. (2018)

300 , T , 350 340 , T , 1000

Farjana et al. (2018) Farjana et al. (2018)

340 , T , 1000

Farjana et al. (2018)

Compound parabolic collector Fresnel reflector Parabolic reflector Flat-plate absorber Spherical bowl reflector Parabolic dish reflector

Table 18.5 Classification of solar cookers. Solar cookers

Collector type

Methods

Concentrating (disk type)

Transmitting concentrator Reflecting concentrator: Parabolic Cylindric Spherical Frensel With reflector Without reflector: Single Double Multiple Steam based Chemical based CPC Organic fluid

The concentrated solar rays are reflected to the pot

G

G

G

G

Nonconcentrating (box type)

The pot is placed in the collector

G

G

G

Indirect use

CPC; Compound Parabolic Concentrator.

The energy is transferred by a heat transfer medium

506

18.5

Green Food Processing Techniques

Solar drying systems

Drying is one of the oldest methods of preserving food and can be specified as a simultaneous heat and mass transfer operation in which water activity of a foodstuff is lowered by the removal of water by evaporation into an unsaturated gas stream. The conventional method of air drying is represented by a typical drying curve of a food product. This drying phenomenon is subdivided into three stages. During the first stage, the drying rate is constant because the surface of the product contains moisture-free. In the second stage, moisture is transported from the inner part of the product to the surface, and the critical moisture content is reached, this is called the first falling rate period. In the second falling rate period, there is a slow diffusion of water to the inner surface leading to desorption and diffusion through pores to the surface. Drying is used for the preservation of food; it involves heating a product to evaporate the water it contains (or another solvent). There is a distinction between boiling and entrainment drying. Boiling is when the product reaches the boiling point of water. During the drying by entrainment the product to be dried is brought into contact with a current of air more or less hot. The warm air transmits some of its heat to the product that develops a partial water pressure at its surface greater than the partial pressure of the water in the air used for drying. This pressure difference causes a transfer of material from the surface of the solid to the “drying agent.” In order to dry a product, liquid or solid, it is necessary to provide heat, energy. Overall, it is considered that drying operations consume about 12% of the industrial energy used in the manufacturing process (Brunetti et al., 2015). This part is important and it is vital to find ways to optimize those processes in both economical and ecological approach. The traditional solar drying is an established food preservation technique, yet it doesn’t preserve the quality of the food since it is an unprotected environment and can be infected by insect, dust, dirt, and animals, which may lead to negative effect on the economic value of the product Fig. 18.2. Therefore, it is best to use solar-energy systems (Lahsasni, Kouhila, Mahrouz, & Idlimam, 2004; Visavale, 2014).

Figure 18.2 Advantages and disadvantages of using solar drying.

Solar as sustainable energy for processing, preservation, and extraction

507

Figure 18.3 Solar drying techniques.

Solar-energy drying systems are normally classified by both the heating and heat utilization modes. In general, there are two major groups (Ekechukwu & Norton, 1999): G

G

Active solar-energy dryer (hybrid); Passive-energy dryer (natural-circulation).

Each of them is subcategorized in three classes Fig. 18.3: G

G

G

Integral-type solar dryers; Distributed-type solar dryers; Mixed-mode solar dryers.

18.6

Solar pasteurization

Pasteurization is defined as heating food process with as purpose to kill and eliminate harmful organisms while reducing the banal flora (Caso et al., 2008). Researchers were interested in developing and designing pasteurization systems that obtain their thermal energy from a green source, that is why they turned to solar energy. First studies focused on water pasteurization, knowing that diseases caused by water are the reason behind five million deaths per year (Burch & Thomas, 1998). Further studies focused on milk pasteurization since it is a fundamental product for human nutrition.

508

18.7

Green Food Processing Techniques

Environmental impacts using solar energy

Two main environmental impacts can be easily identified; the first one is the mitigation of deforestation giving; indeed the annual consumption of forests is at a rate of 1.3% of the total forest area which stand for 10
15 million hectares per year, and fuel wood gathering represents a major compounds in this equation (Manibog, 1984). Another example is the sub-Saharan countries with 70% of their energy derived from wood fuel, and it is mostly used for cooking purposes (Mwampamba, 2007). The second one is reducing global pollution as well as its effects on human health. In fact, the exposure to cooking fuels was found to be a major cause of respiratory symptoms, which also includes chronic bronchitis (Behera, Chakrabarti, & Khanduja, 2001). Solar technologies are known as green, clean, and renewable energy sources that provide significant environmental benefits compared to the conventional energy sources; however, these systems are not perfect, and they often exhibit some negative yet minor environment impacts during their operational process: G

G

G

G

Land use and thermal pollution: The large covered land ecosystem and productivity as well as the thermal balance can be affected (Tsoutsos, Frantzeskaki, & Gekas, 2005). There is also the possibility of accidentally burning or polluting the surrounding area. Visual impacts: Visual impacts are related to the reflectivity of the used solar-energy system coupled with visual pollution. Impacts on natural resources: Solar-energy systems have negative environmental impacts during their production since they still use conventional energies for manufacturing. Air pollution: Emissions are produced during both manufacturing and transportation.

18.8

Hazard analysis and critical control points and hazard and operability considerations using solar energy

HACCP [hazard analysis and critical control points (CCPs)] concept is a systematic approach to food safety management based on seven recognized principles designed to identify and prevent the hazards likely to occur at any stage in the food supply chain (Sicaire, Vian, & Chemat, 2017). A CCP is a step in the flow diagram of the food process at which control measures can be applied. These CCPs are essential to prevent or eliminate a food safety hazard or reduce it to an acceptable level. Solar energy is nowadays used in many unit operations during food processing, not only considering their physical effects for extraction and drying, but also considering their biological effects for pasteurization for example. However, the use of solar energy in food engineering requires the setting up of an HACCP program in which the CCPs are identified, so that potential hazards in producing a safe quality product can be controlled. In the solar-energy treatment the critical processing factors are assumed to be the time of exposure/contact, the volume of food to be processed, the composition of the food, and the temperature of the treatment.

Solar as sustainable energy for processing, preservation, and extraction

509

Hazard and operability study is a formal, systematic, logical, structured investigative study for examining potential deviations of operations from design conditions that could create process
operating problems and hazards (Sicaire et al., 2017). The main hazard the users may face is from accidental-contact exposure to the solar irradiation and high temperature. Direct-contact exposure can cause tissue injury for the operator. High temperature induced by solar energy can cause burns and be a potential fire hazard. Irradiation with UV could imply damages to the eyes.

References Afzal, A., Munir, A., Ghafoor, A., & Alvarado, J. L. (2017). Development of hybrid solar distillation system for essential oil extraction. Renewable Energy, 113, 22
29. Available from https://doi.org/10.1016/j.renene.2017.05.027. Akpinar, E. K., & Bicer, Y. (2008). Mathematical modelling of thin layer drying process of long green pepper in solar dryer and under open sun. Energy Conversion and Management, 49 (6), 1367
1375. Available from https://doi.org/10.1016/j.enconman.2008.01.004. Anozie, A. N., Bakare, A. R., Sonibare, J. A., & Oyebisi, T. O. (2007). Evaluation of cooking energy cost, efficiency, impact on air pollution and policy in Nigeria. Energy, 32(7), 1283
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744. Behera, D., Chakrabarti, T., & Khanduja, K. L. (2001). Effect of exposure to domestic cooking fuels on bronchial asthma. The Indian Journal of Chest Diseases & Allied Sciences, 43(1), 27
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619. Available from https://doi.org/10.1016/S0960-1481 (01)00136-7. Sicaire, A.-G., Vian, M., & Chemat, F. (2017). Handbook of ultrasonics and sonochemistry. https://doi.org/10.1007/978-981-287-470-2. Sonune, A. V., & Philip, S. K. (2003). Development of a domestic concentrating cooker. Renewable Energy, 28, 1225
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Further reading Kabir, E., Kumar, P., Kumar, S., Adelodun, A. A., & Kim, K. H. (2018). Solar energy: Potential and future prospects. Renewable and Sustainable Energy Reviews, 82 (September 2016), 894
900. Available from https://doi.org/10.1016/j.rser.2017.09.094. Saxena, A., Goel, V., & Karakilcik, M. (2018). Solar food processing and cooking methodologies.

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Author Index

Note: Page numbers followed by “f” and “t” refer to figures and tables, respectively. A Aamir, M., 175
177, 180t Abbas, M., 199 Abd El-Aziz, M. F., 440 Abd Hamid, I. A., 3 Abd Rahman, N., 3 Abdelkader, L., 501t Abdelrahim, K., 159
160 Abdel-Salam, M. F., 501t Abert-Vian, M., 48
49, 476, 478t Abrahamsson, V., 205 Abu Dagga, Y., 173
174 Achir, N., 166 Adachi, S., 209
211 Adami, R., 60, 74
77 Adamopoulos, K. G., 350
351 Adekunte, A. O., 41t Adhikari, B., 338t, 475 Adhikari, R., 338t Aditya, N. P., 338t, 348, 353 Afkhami, R., 351 Afzal, A., 7, 503t Aganovic, K., 123
124, 150 Agarwal, R. K., 375 Aguiar, A. C., 75 Aguiar, J., 335
336 Aguilar, J. G. D., 151 Aguilar-Reynosa, A., 465 Aguilera, J. A., 435
437 Aguilera, J. M., 316 Ahlfeld, B., 438 Ahmad, M., 355 Ahmadi, A., 482 Ahmed, J., 8
9 Ahmedov, A., 115t, 122 Ahn, J., 88, 93t Aimar, P., 248
249, 255
256, 259t, 261, 274

Ait Amar, H., 49 Aizpurua-Olaizola, O., 352 Akdemir Evrendilek, G., 112 Akpan, U. G., 315 Akpinar, E. K., 501t Al-Akoum, O., 266 Alarcon-Rojo, A., 29 Al-Baali, G., 467
468 Albarelli, J. Q., 64
65, 71
72 Albet, J., 443t Albrecht, T., 208 Albu, S., 26
27 Alencar, J. W., 478t Alexandrakis, Z., 92, 97
98 Al-Hilphy, A. R. S., 177 Aliakbarian, B., 350
351 Alignan, M., 206 Allaf, K., 221
223, 226
229 Allaf, T., 221
223, 226 Allali, H., 168t, 172
173 Alli, I., 104t Alliod, O., 268 Almajano, M., 348 Almajano, M. P., 347
348 Almeida, A., 95t Almohammed, F., 177
178, 414
417, 415f Alpas, H., 110 Alrgei, H. O. S., 336 Altamirano, C., 210
211 Altay, F., 352 Altintas, Z., 350
351 Altuner, E., 110 Aluko, R. E., 104t Alvarado, J. L., 7, 503t Alvarenga, V. O., 64 ´ lvarez, I., 43t, 417
418, 420, 425
426 A ´ lvarez-Blanco, S., 268 A Alzamora, S. M., 41t

514

Amador-Espejo, G. G., 150 Amalia Kartika, I., 297
299, 299f, 310
311, 311f Amaral, G. V., 70
71 Amato, F., 123 Ambrosi, V., 102 Ameer, K., 58
59, 175 Amigo-Benavent, M., 210 Anandharamakrishnan, C., 351 Anastas, P. T., 193, 194f, 316 Anbinder, P. S., 345
346 Anderson, D., 315
316 Anderson, N., 94t Andersson, J. M., 207 Andrade, M., 378
379 Andre´, C., 373 Andreou, V., 97, 111
112 Andrieu, J., 475 Anema, S. G., 113 Anese, M., 7 Angers, P., 256 Annie, S. I., 499 Annunziata, M., 142 Anozie, A. N., 504t Anselmi, C., 344 Antonio, A. V., 174 Arago´n, C., 435
437 Aravindh, M. A., 500 Areas, J. A., 294 Aree, T., 355 Ariyarathna, I. R., 336, 347 Arjunan, K., 435
437 Arlabosse, P., 306 Armenta, S., 175 ´ . J., 413 Arnal, A Arnau, J., 112
113 Arnold, G., 39t Arora, A., 465 Arque´s, J. L., 112 Arroyo, C., 166 Arroyo, G., 111 Arshadi, M., 60f Artik, N., 350
351 Asbahani, A. E., 65 Asghari, F. S., 210
211 Ashokkumar, M., 23
24, 26
29, 31, 45
46 Ashraf, B., 355 Asker, D., 26
27 Assadpoor, E., 147
148

Author Index

Assamia, K., 48
49 Astray, G., 344 Atia, M. F., 501t Atra, R., 264
265, 280 Attard, T. M., 57
59, 60f, 64 Atungulu, G. G., 43t, 222
223 Atuonwu, J. C., 488 Avila-Sosa, R., 386
387 Awad, S. B., 37
39 Awad, T. S., 26
27, 46 Awuah, G. B., 7 Ax, K., 139
140 Ayappa, K. G., 456, 487 Aydinkaptan, E., 474
475 Azam, S. M. R., 472 Azapagic, A., 481
482, 484t Azzaro-Pantel, C., 273
274 B Baars, A., 116, 118 Bacchin, P., 255
256, 265 Badens, E., 65, 316 Baeza, R., 344 Bah, C. S., 103 Bai, Y., 441 Bailly, M., 248
249, 277 Bajpai, V. K., 375 Bakare, A. R., 504t Baker, R. W., 258f, 267
268, 271 Balaban, M. O., 3
4 Balanˇc, B., 345, 352, 354 Balannec, B., 280 Balasubramaniam, V., 113
114 Balasubramaniam, V. M., 2
3, 11
12, 88, 91, 93t, 112 Balat, M., 310
311 Baldin, J. C., 338t, 350
351 Baldo, P., 48
49 Baldwin, D. F., 64 Balentı´c, 61, 69 Balint, A., 264
265 Ballesteros, L. F., 346, 350
351 Balogh, T., 98 Bals, O., 406, 409f, 414, 416f, 423, 423f, 424f Balvardi, M., 315
316 Banakar, A., 177 Bandala, E. R., 277 Banerjee, J., 465

Author Index

Banerjee, P., 396 Bara´c, M., 346 Bara´c, M. B., 346 Baratta, M. T., 381 Barba, F. J., 1
2 Barba, F. J., 2
3, 5, 7, 12, 106
108, 316, 325f, 405
406, 441 Barbero, G. F., 68, 77
78 Barbosa-Ca´novas, G., 23
26, 122 Barbosa-Canovas, G. V., 11
12, 87
88, 120 Barbosa-Ca´novas, G. V., 110, 404, 406, 425
426, 467
468 Bargas, M. A., 64 Barnes, M., 40 Baron, A., 418, 419f Baroutian, S., 199
204 Barrow, C. J., 338t Bartels, P. V., 49, 88 Bartis, E. A. J., 438 Bartkowiak, A., 336 Bartolomeu, W. S. S., 174 Barutc¸U Mazi, I., 474 Barzegar, M., 177 Basak, T., 461 Bassi, A., 66 Bastos, C. P., 64 Basu, S., 63 Bates, D., 8, 40, 45
46 Batista, M. T., 68 Baudelaire Djantou, E., 466 Baudin, I., 482 Bauer, B. A., 120, 121t Bawa, A. S., 165 Bayoumi, S., 377 Baysal, A. H., 168t, 177 Baysal, T., 165, 173 Bazinet, L., 256
257, 273, 276 Beckman, E. J., 63 Behera, D., 508 Beheshti, B., 166 Behravesh, A. H., 61 Behrend, O., 139
140 Bekassy-Molnar, E., 264
265 Bekhit, A. E.-D. A., 103 Belkova, B., 165
166 Bellettre, J., 142 Bello-Ochende, T., 499 Bellumori, M., 8

515

Belˇscˇ ak-Cvitanovı´c, A., 345
346, 352
353 Belˇscˇ ak-Cvitanovic, A., 338t, 345
346, 350
352 Belton, P. S., 338t Ben Ammar, J., 405
406, 422 Ben Amor, B., 223, 226 Benelli, P., 71
72 Beneroso, D., 465 Benetto, E., 482 Benzaria, A., 149 Berardi, P. G., 463t Beres, C., 336 Beresford, T. P., 95t Berg, S., 352 Bergsten, U., 60f Berka, B., 226 Bermu´dez-Aguirre, D., 23
26, 110, 122 Bernardes, A. M., 281 Bernardi, A., 309
310 Berni, M. D., 71
72 Bertin, A. P., 279 Besombes, C., 221
222 Betz, M., 346
347 Bevilacqua, A., 375 Beyer, G., 289
290 Bhandari, B., 147
148, 335, 349 Bhunia, A. K., 376 Bhuyan, K., 465 Bi, J., 77 Bicer, Y., 501t Bilek, S. E., 338t, 346
347 Bilgin, M., 8 Billaud, C., 418, 419f Bily, A., 26
27, 222
223, 231 Bindu, J., 95t Birnboim, A., 463t Bisinella de Faria, A. B., 482, 486 Bitencourt, R. G., 70 Bivolarevic, V., 346 Blanc, M., 306 Blanch, G., 355 Blanco, C. A., 273 Blasco-Moreno, A., 147 Bleoanca, I., 2
3 Blin, J., 317
318 Bochot, A., 344 Boehm, D., 431
432 Boelsmand, J., 264 Bogaardt, M.-J., 442

516

Bogaert, L., 315
318 Bogaerts, A., 435
437 Boivin, P., 279 Boldo, P., 23 Boni, R., 309
310 Bonilla, F., 475 Bonomi, F., 102 Boom, R. M., 265
266 Boonbumrung, S., 474 Borda, D., 2
3 Borderias, A. J., 112
113 Borderı´as, A. J., 112
113 Borghei, A. M., 166 Borisova, D. R., 197 Bormashenko, E., 442, 443t Bormashenko, Y., 442 Bornhorst, E. R., 467
468, 470t Botelho, G., 335
337 Both, S., 48
49 Botsoglou, E., 377 Bouallegue, K., 221
222 Bouix, M., 279 Boulekou, S., 97
100 Bouras, M., 7 Bourke, P., 431
433, 438
441 Bourseau, P., 254
255, 281 Boussetta, N., 5
6, 144
145 Boutin, O., 316 Bouvier, J.-M., 228
229 Bouvier J. M., 297 Bozkurt, H., 165 Braga, M. E. M., 68 Brandolini, A., 347 Brans, G., 265
266 Bravi, E., 67 Bravo, D., 112 Bray, T. L., 476 Bredeson, D., 317
318 Breford, J., 352 Breil, C., 48
49, 478t Bretz, M., 352 Brijesh, K., 37
39 Brin˜ez, W. J., 151 Briones-Labarca, V., 106 Brochier, B., 168t, 173 Brody, A. L., 468 Brookman, J. S. G., 145 Brooks, J., 353 Bruneton, J., 371

Author Index

Brunetti, L., 506 Brunner, G., 58
59, 73
74, 208, 316 Brunton, N. P., 413 Buckow, R., 2
3, 97, 106
108 Buddhi, D., 501t Budryn, G., 344 Bueno-Ferrer, C., 432, 440 Buffa, M., 147 Bugarski, B., 335 Buhr, N., 317
318 Bukhanko, N., 60f Bukvicki, D., 375
377 Burch, J. A. Y. D., 507 Bursa´c Kovaˇcevi´c, D., 1
2, 5
8, 11
12 Busch, V., 337
344, 338t, 350
351 Buˇs´ıc, A., 353 Busk, L., 210 Bussemaker, M. J., 27
28 Butz, P., 110 Buzrul, S., 94
97 C Cabeza, M. C., 41t Cabral, B. R., 350
351 Cabral, F. A., 70 Cai, S., 26
27 Caiazzo, F., 276 Caillet, S., 376 Calame, J., 463t ˇ Calija, B., 344, 346
347, 349
351 ˇ Calija, B. R., 344, 346
347, 349
351 Calinescu, I., 477 Callanan, M., 150 Callens, A., 484t Callewaert, L., 148
149 Calo, J. R., 375 ˇ ´c-Brunet, J., 347 Canadanovı ˇ Canadanovi´ c-Brunet, J., 347, 351 Canas, S., 335
336 Candan, F., 382t, 385 Cando, D., 112
113 Cando˘gan, K., 110 Candy, L., 297 Canella, M., 309
310 Cannizzaro, L., 277 Cano, M. P., 98 Cao, B., 272 Cao, H., 468
469, 470t Capanoglu, E., 352

Author Index

Capello, C., 213
214 Capelo-Martı´nez, J.-L., 29
30 Cappato, L. P., 165 Capuano, E., 210 Caputo, G., 76
77 Carbo´, R., 348 Carciofi, B. A. M., 473 Cardea, S., 60 Cardona, C. A., 73 Cardonic, A., 37
39 Cardoso, S. M., 478t Carfagna, R., 463t Carle, R., 210
211 Carlez, A., 95t Carmel, Y., 463t Carne, A., 103 Carre´, P., 317
318 Carretero, C., 112
113 Carrillo-Lopez, L., 29 Cartier, S., 271, 279 Carvalho, P. I. N., 63
64, 67, 77
78, 206
207 Casale, A., 373 Casas, L., 76
77 Caso, R., 501t, 507 Cassano, A., 250, 276 Ca´ssia, C. R. B., 68 Castillo, M. R., 355 Castillo-Peinado, L. S., 476
477 Castriotta, G., 309
310 Castro, I., 167
173, 168t Castro, S. M., 98 Castro-Go´mez, P., 315
316 Castro-Puyana, M., 59, 195
199, 196f, 205, 213
214, 318
319 Castro-Rosas, J., 349
350 Catarino, M., 273 Cater, C. M., 318
319 Cattaneo, S., 273
274 Cazalis, R., 443t Ceni, G., 64 Cerqueira, M. A., 174 C ¸ eter, T., 110 ´ Cetkovi´ c, G., 346
347 Chai, M., 266 Chakrabarti, T., 508 Chalier, P., 39t Chamberland, J., 104t Chambin, O., 349

517

Champagne, C. P., 353
354 Chandrasekaran, S., 461, 488 Chang, C.-Y., 465 Chang, S., 267 Chang, S. K. C., 147 Chang, Y. K., 293 Changzhen, W., 110 Changzheng, W., 110 Chao, J., 344 Chapuis, A., 317
318 Charalampopoulos, D., 77 Charcosset, C., 268 Charoux, C. M. G., 37
39 Charrier, S., 39t Chatzifragkou, A., 77 Chatzopoulou, P. S., 377 Chaufer, B., 280 Chauvet, M., 61, 64, 69 Chave´ron, H., 378
379 Chaves, M. A., 348 Cheftel, J. C., 106, 139
140 Cheftel, J.-C., 95t, 98
100 Chellaram, C., 2 Chemat, F., 7
9, 23
32, 34, 37
40, 42
49, 57
59, 62, 73
74, 140, 175, 222
223, 231, 316, 374, 476
480, 478t, 487
488, 508 Chemat, S., 48
49 Chen, F., 43t, 474 Chen, G., 275 Chen, J., 346, 441 Chen, J.-C., 43t Chen, J. L., 4 Chen, L., 278, 346 Chen, R., 278 Chen, V., 266 Chen, W., 335 Chen, X., 474 Cheng, J.-H., 484t Cheng, L., 77 Cheng, S.-C., 2 Cheng, X., 260 Cheong, J. S. H., 195
196 Cherubini, F., 71 Cheryan, M., 248
249 Chevalier-Lucia, D., 142 Chew, J. W., 267 Chew, S., 352 Chiaradia, A. C. N., 111

518

Chicho´n, R., 104t Chiralt, A., 345 Chirife, J., 337
344 Chisti, Y., 145 Chizmadzhev, Y. A., 404 Cho, H. Y., 167, 168t Cho, W. I., 166 Cho, Y.-J., 206
207 Choe, W., 435
437 Choi, H. S., 385 Choi, W., 167 Cholet, C., 406, 421f Chordia, L., 74
75 Chotard-Ghodsnia, R., 266 Chottanom, P., 176
177 Choudhury, G. S., 298 Chouliara, E., 376 Christakopoulos, P., 118 Christophoridou, S., 355 Chu, Y.-H., 441 Chua, S. C., 43t Chun, B.-S., 206
207 Chung, I.-M., 9 Chung, M.-S., 205
206 Chung, T.-S., 261, 277 Chung, Y. K., 167 Cicero, A. F. G., 336 Cifuentes, A., 57, 71
72, 207, 318
319 Cilla, A., 106 Cintas, P., 23
24, 42
46 Cirano, N., 65 Cisse´, M., 275 Claeys, W. L., 121t Claflin, K., 500 Clares, B., 336 Clark, J. H., 403 Clavier, J. Y., 75, 316 Coccaro, N., 151 Cocero, M. J., 60, 64
65, 208
209 Coelho, C. C. S., 174 Coelho, J. A. P., 67 Coimbra, M. A., 77, 478t Colas, D., 306
307, 307f Cole, R., 26
27 Colletti, A., 336 Colnagui, G., 478t Common, A., 61 Condon, S., 41t Condo´n, S., 43t, 425
426

Author Index

Condo´n-Abanto, S., 43t Conidi, C., 276 Considine, K. M., 91 Coons, J. E., 145 Cooper, B., 440 Corbo, M. R., 375
376 Corradini, M. G., 110 Corrales, M., 110
111 Corte´s-Mun˜oz, M., 142, 147
149 Couallier, E. M., 279 Courel, M., 275 Crampon, C., 65 Crandall, P. G., 375 Crapiste, G., 456 Crapiste, G. H., 221 Craveiro, A. A., 478t Cravotto, G., 9, 23
24, 32, 42
46, 175, 316, 318, 478t, 487 Crelier, S., 88
89 Critianini, M., 151 Croft, K. D., 336 Cronin, D. A., 41t, 166, 484t Cros, E., 475 Cros, S., 281 Crowe, T. W., 297 Cruz, N. S., 147
148, 151 Cruz, R. M. S., 41t Cuartas-Uribe, B., 268 Cuccurullo, G., 463t Cui, Y., 261, 277 Cui, Z., 472 Cui, Z. F., 267 Cukelj, N., 1
2 Cullen, P. J., 41t, 431
434, 438
441, 445
446 Cullor, J., 2 Cunha, A., 95t Cvetanovı´c, A., 200t, 205, 336 D Da Cruz, A. G., 62 Da Porto, C., 43t Da Silva, F. A., 77 Da Silva, M. E. V., 505 da Silva, R. P. F. F., 59, 318
319 Da Silveira, S. M., 376 Daferera, D. J., 43t Dag, D., 337
344 Daghero, J., 70

Author Index

Dale, T., 145 Dallinger, D., 488 Damar, S., 3
4 Damyeh, M., 177
178 Danaher, M., 432 Danielson, R., 209 Danquah, M. K., 145 D’Archivio, M., 199 Daryaei, H., 91
92 Das, S., 95t DasGupta, S., 266
267 Datta, A. K., 456
457, 474, 477, 487 Datta, N., 142 Daufin, G., 259t, 261, 272, 274, 278, 280 Daun, J. K., 315, 317
318 Dave, H. K., 270 David, M. W., 267 Davidov-Pardo, G., 355 Davidson, P. M., 456
457, 487 Da´vila, J. F., 346
347 Davis, E. A., 456 Davis, H. T., 456 Davis, J., 123 De, S., 266
267 De Aguiar, A. C., 77
78 De Alba, M., 112 De Almeida Meireles, M. A., 62 De Ancos, B., 98 De Andrade Lima, M., 77 De Choudens, C., 296 de Elvira, C., 117 De Freitas, M. Q., 62 De Ginestel, G., 317
318 de Groot, G. J. J. B., 432 de Haan, A. B., 316, 319
320, 320f De Heij, W. B. C., 119 de Jong, P., 39t de la Guardia, M., 175 de la Hoz, A., 488 de La Torre, L. G., 338t De Marco, I., 61
62, 70, 72 de Matos Junior, F. E., 349 de Melo, M. M. R., 62
63, 75, 318
319 De Noni, I., 273
274 de Oliveira Soares Vicente, A. A. M., 160
161 de Pinho, M. N., 271
272, 281 De Sousa, H. C., 68 de Souza, J. R. R., 346

519

De Souza, V. B., 338t, 344, 350
351 de Souza Simo˜es, L., 336, 349, 351
352 De Vries, H., 162 Debevere, J., 394 De´bora, P. J., 176
177 Decloux, M., 271, 278
279 Decorti, D., 43t Deeth, H. C., 142 Degrois, M., 48
49 Dehghani, F., 74
75 Deji, S., 110 Dejmek, P., 406, 422 del Castillo, M. D., 210 ´ ., 273 del Olmo, A Del Valle, J. M., 67, 73
74, 77, 316 Deladino, L., 337, 345
346 Delgado, A., 116
118 Delgado, M., 348 Delgado, M. E., 347 Delgado-Vargas, F., 344 Della Porta, G., 70 Delsart, C., 420, 421f Demir, S., 480 Demirbas, M. F., 310
311 Demirci, A., 395 Denys, S., 116
117 De´on, S., 254
255 Der Poel, P., 413
414, 416
417 Dermesonlouoglou, E., 112 Dermesonlouoglou, E. K., 112 Desrumaux, A., 142, 147 Devi, N., 346 Devi, S., 475 Devlieghere, F., 394 Dewettinck, K., 264
265, 267
268 Dey, T., 163
164 Dhamvithee, P., 474 Dhuique-Mayer, C., 272 ´ ., 488 Dı´az-Ortiz, A Dibert, K., 475 Diels, A. M. J., 148
150 Dijkstra, A. J., 299
300 Dikeman, M. E., 39t Dimitrov, D. D., 7 Dimopoulos, G., 97, 111
112 D’Incecco, P., 147 Ding, H., 344 Ding, L., 144
145, 266 Ding, Z., 344
345

520

Diosady, L., 317
318 Djas, M., 73
74 Djekic, I., 2 Do Cardoso, M. F. C., 164 Do¨bele, H. F., 435
437 Dobre, T., 75 Dobrin, D., 432, 442f, 443t Dogan, C., 95t Domeneghini, G., 178 Domeneghini, G., 168t, 173 Domingues, L., 167
172 Domı´nguez, R., 1
2 Dominguez-Lopez, A., 346
347 Dominiguez, H., 318 Donsı´, F., 142, 147, 149
152, 268 Donsı`, F., 335, 347 Ðorðevı´c, V., 344
345, 349
355 Dorileo, I. L., 71
72 Do¨rnenburg, H., 111 Dornier, M., 272, 275, 281 Dorraki, N., 440 dos Santos, C. A., 160
161 dos Santos, P. C., 271
272 Dotta, R., 68 Doumeng, C., 307f Doyen, A., 103, 104t, 256
257 Dragovı´c-Uzelac, V., 350
351 Dramur, M. U., 8 Drioli, E., 250 Drioli, E., 276 Drogui, P., 43t Drori, E., 442 Du, C., 432 Du, Y., 337
344 Duan, L., 209
210 Duarte, A. C., 59 Dubery, I. A., 200t Dubey, N. K., 375 Dubinov, A. E., 443t Duchˆene, D., 344 Dufaure, C., 297
299, 310 Dufton, G., 273, 280 Dumay, E., 104t, 106, 139
140, 142, 147, 149, 151 Dumont, M. J., 346 Dumsday, G. J., 145
146 Duncan, S. M., 476 Dunne, J., 441 Dunnill, P., 140

Author Index

Dupont, W. D., 12 Durling, L. J. K., 210 Durmaz, G., 315 D’urso, E., 70 Dussault, C., 7 Dutournie´, P., 254
255 Duygu, B., 166 Dziezak, J. D., 297 E Ebihara, K., 432 Eggers, R., 316, 325
327 Eing, C., 407f Ekechukwu, O. V., 507 Ekman, A., 214 El Darra, N., 180t, 181, 418
420 El Zakhem, H., 425f Elamin, W. E., 115t, 122 Elaragi, G. M., 440 Eleftheriou, E. G., 113 Elez-Martinez, P., 425
426 Elhussein, E. A. A., 484t Elmaataoui, M., 478t El-Nono, M. A., 501t Elsebaie, E. M., 351 Elvira, C., 117 Emin, M., 348 Endan, J. B., 115t, 122 Endo, T., 296 Engchuan, W., 166 Engler, C. R., 145 Eriksson, C. E., 381 Eriksson, D., 60f Erkmen, O., 95t Ersan, S., 200t, 210
211, 344 Ertbjerg, P., 104t Erteky´n, C., 501t Escobedo-Avellaneda, Z., 97 Escriu, R., 147 Eshtiaghi, M., 41t Eskin, N. A. M., 315 Espachs-Barroso, A., 425
426 Espinosa, Y. G., 348 Esquena, J., 146
147 Essa, R. Y., 351 Estel, L., 464 Esteve, M. J., 2 Este´vez, M., 353 Estevinho, B. N., 335
336

Author Index

Evon, P., 297
298, 301f, 308
310, 309f Ezebor, F., 315 Ezhilarasi, P., 351 F Fabiano-Tixier, A., 23
24 Fabiano-Tixier, A. S., 23 Fagan, C. C., 144
145 Fages, J., 61, 316 Falconer, J. R., 59 Falconi, C., 67 Fane, A. G., 267, 275 Fang, Z., 338t Fantozzi, P., 67 Farag, K. W., 484t Farahnaky, A., 177
178 Fargues, C., 248
249, 279 Farhat, A., 477
480, 478t Farhoosh, R., 177 Farı´as-Campomanes, A. M., 71
72 Farid, M., 166 Farid, M. M., 117, 467
468, 473
474 Farjana, S. H., 502
505, 505t Farkas, B. E., 112
113 Farkas, D., 113
114 Fathi, M., 337 Fauster, T., 413 Favaro-Trindade, C. S., 349 Feijoo, S. C., 150 Fellows, P., 293 Feng, H., 29
30, 37
40, 41t, 45
46 Feng, W., 353 Fernandes, A. A. R., 111, 355 Fernandes, C., 271
272 Fernandes, F. A. N., 43t Fernandes, P. M. B., 111 Fernandez, A., 306 Fernandez, C., 501t Fernandez, D. P., 111 Ferna´ndez, F. G. A., 66 Ferna´ndez, M. B., 221, 226 Fernandez, X., 373
374, 477
480 ´ vila, C., 147
148 Ferna´ndez-A Ferna´ndez-Ponce, M. T., 76
77 Fernandez-Sevilla, J. M., 66 Ferragut, V., 95t, 151 Ferrando, M., 353 Ferrari, G., 102, 104t, 142, 147, 149
152, 268, 335

521

Ferrario, M., 41t Ferreira, R. E., 293 Ferreira, S. R. S., 71
72, 75 Ferreira, S. S., 478t, 481 Ferrentino, G., 4 Fick, M., 279 Fidelis, M., 1
2 Filatova, I., 443t Filatova, I. I., 443t Fincan, M., 406, 417
418 Fisher, U., 213
214 Fitzgerald, G. F., 91 Fliss, I., 151 Flores, F. P., 346
347 Floury, J., 142, 147
149 Flugstad, B., 7 Fogliano, V., 210 Foglio, M. A., 70 Foidl, N., 325
327 Fontecha, J., 315
316 Forget, M., 228
229 Fornari, T., 61, 65, 76
77 Forney, L., 399 Forster-Carneiro, T., 71
72 Fort, N., 112
113 Fortea, I., 338t Fortea, M. I., 338t, 344 Foster, N. R., 74
75 Fotirı´c Akˇsi´c, M. M., 336 Fowler, M. R., 168t, 173
174 Fox, P. F., 106, 142, 147 Franck, M., 102 Franco, A. P., 472 Franco, J., 501t Frankel, E. N., 379
380 Frantzeskaki, N., 508 French, J., 10, 10f, 502f Frias, J., 102 Frias, J. M., 432 Frideres, L., 123 Frı´gola, A., 2 Fryer, P., 117 Fryer, P. J., 117, 145 Fu, W., 261 Fu, Y.-C., 460
462 Fukuoka, M., 181
182 Fulladosa, E., 112
113 Fyfe, L., 377

522

G Gaaloul, S., 273 Gabaldon, J. A., 338t Gabaldo´n, J. A., 338t Gabassi, G., 147 Gabrı´c, D., 5 Gabriel, A. A., 438 Gaens, W. V., 435
437 Gagic, T., 210
211 Galanou, E., 97 Galindo, F. G., 422 Gallant, D., 48
49 Gallego-Jua´rez, J. A., 39t Gallego-Schmid, A., 481
483 Gally, T., 166 Galmarini, M. V., 344 Ga´lvez Moraleda, J. C., 39t Gani, A., 41t, 355 Ganzler, K., 476
480 Gao, J., 206
207 Garcı´a, A. F., 110 Garcı´a, M. C. C., 66 Garcia, S., 2 Garcı´a-Gimeno, R. M., 95t Garcia-Gonzalez, L., 70
71 Garcia-Mendoza, M. D. P., 68 Garcia-Mora, P., 102 Garcia-Palazon, A., 97 Garcı´a-Risco, M. R., 61 Garcı´a-Tejeda, Y. V., 338t Garie´py, Y., 472 Garmus, T. T., 70 Garnjanagoonchorn, W., 166 Garofulı´c, I. E., 350
351 Garrigues, S., 175 Gaset, A., 310 Gathen, V. S.-V. D., 435
437 Gaudreau, H., 353
354 Gaulin, A., 139 Gautam, A., 298 Gavach, C., 279
280 Gavach, M., 279 Gavahian, M., 177
178, 180t, 441 Gavlighi, H. A., 177 Gaya, P., 112 Ge, L., 442 Gebreyohannes, A. Y., 277 Gedye, R., 476 Gekas, V., 508

Author Index

Geladi, P., 60f Ge´ny, L., 421f George, S., 165
166 GEOrgescu, C., 375 Georget, E., 91
92, 150 German, J. B., 379
380 Gershon, D., 463t Gervais, P., 111 Ge´san-Guiziou, G., 266, 272
274, 280 Getachew, A. T., 206
207 Geveke, D., 395
396 Ghafoor, A., 7, 503t Ghani, A. G. A., 117 Gharibzahedi, S. M. T., 2
3 Gharsallaoui, A., 349 Ghasempour, A., 440 Ghidossi, R., 421f Ghomi, H., 440 Ghosh, P. C., 163
164 Ghoshal, G., 336
337 Giacobbo, A., 281 Giacometti, J., 5, 7
8, 11 Giampaoli, P., 281 Giannoglou, M., 97 Giasson, J., 151 Gibis, M., 354 Giersemehl, P., 422
423 Giguere, R. J., 476 Gilbert-Lo´pez, B., 195
197 Gil-Ramı´rez, A., 206 Ginies, C., 477
480, 478t Giorno, L., 277 Giraldo, G. I., 351 Girtzi, O., 355 Gkarane, V., 104t Gladman, S., 117 Glatzel, V., 67 Goetz, L. A., 260 Gogate, P. R., 46
48 Gogoi, B. K., 298 Gogou, E., 97, 110, 118, 120, 121t Goh, D., 195
196 Goic, R., 499 Gokmen, V., 315 Gokulakrishnan, P., 375 Gola, S., 119 Goli, M., 351 Gomaa, A., 353
354 Gomes, C., 338t

Author Index

Gomes, C. F., 165 Gomes, M. T. M., 60 Gomez, R., 102 Go´mez, R., 104t Go´mez-Lo´pez, V. M., 394
395 Go´mez-Mascaraque, L. G., 338t, 347 Gonc¸alves, F., 271
272 Gondrexon, N., 23 Gong, M., 66 Gonin, A., 279
280 Gontier, E., 421f Gonzalez, A., 210
211 Gonzalez, C., 102 Gonza´lez, C., 353 Gonzalez-Barreiro, C., 344 Gonza´lez-Garcia´, J., 23
24 Gonza´lez-Martı´nez, C., 345 Gonzalez-Nunez, R., 289
290 Goodwin, A. R. H., 111 Goonetilleke, A., 277 Gordon, J., 456 Gordon, M., 348 Gordon, M. H., 347
348 Gothandam, K. M., 472 Gou, P., 112
113 Goula, A. M., 350
351 Govaris, A., 377 Granato, D., 5, 9, 12 Grant, S., 88 Grauwet, T., 117, 119, 121t Graves, D. B., 438 Grbin, P., 40 Green, D. S., 436t Griffin, S., 146 Grima, E. M., 66 Grimi, N., 145
146, 181, 316, 410
414, 412f, 416f, 418
420, 420f, 421f, 422
423, 422f Gro¨nroos, A., 39t Grossi, A., 104t Grosso, N. R., 377 Grynyov, R., 442 Guamis, B., 95t, 147, 149, 151
152 Guamis, Lo´pez, B., 151 ¨ ., 210
211 Guclu, Ustundag, O Gu¨ell, C., 353 Guerrero, S., 41t Guiavarc’h, Y., 97
98 Guida, V., 165

523

Guiga, W., 279 Guilbot, A., 48
49 Guimara˜es, J. D. T., 62 Guiraud, J. P., 139
140 Gunning, A. P., 9 Gunstone, F. D., 299
300 Guo, B., 93t, 119 Guo, L., 441 Guo, N., 24
26 Guo, Q., 484t Guo, X., 110
111 Guo, Z., 355 Gut, J. A. W., 472 Gutie´rrez, J. M., 353 Guven, E., 159
160, 165 Guy, R., 293
295 Guyomard, P., 297 Gyawali, R., 375 Gyoutoku, Y., 432 H Hadjeba, K., 443t Hajslova, J., 165
166 Halim, R., 145 Hamany Djande, C. Y., 200t Hamidi-Esfahani, Z., 177 Han, B. N., 178
179 Han, X., 77 Han, Z., 48
49, 484t Hancocks, R. D., 268 Hansen, F., 432 Harding, S. A., 336 Hargenrnaier, R. O., 318
319 Harris, K., 206
207 Hartel, R. W., 39t Hartmann, C., 117 Harun, M. R., 199
204 Harun, R., 145 Harwood, J. L., 299
300 Hashemi, S. M. B., 3, 7, 177
178, 180t Hashizume, H., 438 Hassani, A., 226 Hata, S., 210
211 Hay, J. X. W., 24
26 Hayashi, N., 443t Hayes, M., 103 Hayes, M. G., 142, 147
148 Hayes, W. W., 150 Haznedaroglu, M. Z., 480

524

He, C., 200t, 204
205 He, R., 104t He, Y., 147
148 Hebert, M., 315
316 Hebishy, E., 147
149 Heinonen, J., 68 Heinonen, M., 338t Heinz, V., 111, 150, 413 Hellemons, J. C., 91 Hellman, B. E., 210 Henczka, M., 73
74 Hendrickx, M., 97
98, 119, 121t Hendrickx, M. E., 98, 116
117, 121t Hendrickx, M. E. G., 88
89, 97 Heng, M. Y., 200t Henle, T., 113 Hensarling, T. P., 221 Herceg, K., 1
2, 7
8 Herceg, Z., 5 Herna´ndez, A., 98 Herna´ndez, A., 273 Hernandez-Herrero, M., 151 Herna´ndez Herrero, M. M., 151 Herna´ndez-Herrero, M. M., 150 Herna´ndez-Orte, P., 420 Hernandez-Rojas, M., 338t, 347 Hernando-Sa´inz, A., 122 Herranz, B., 112
113 Herrero, M., 57, 71
72, 77, 195
196, 196f, 198
204, 207, 210
211, 318
319 Herron, J. T., 436t Herry, J.-M., 275 Hew, C. S., 195
196, 206 Hickling, D., 315 Hidalgo, A., 347 Hietala, M., 296
297 Hill, C., 91 Hill, L. E., 338t Hink, R., 316 Hiremath, N. D., 95t Hite, B., 88 Ho, I., 166 Ho, S., 355 Hobbie, M., 325
327 Hoffmann, M., 163
164 Hogenboom, J. A., 147 Hohnova´, B., 207 Holdich, R. G., 268 Holley, R. A., 88

Author Index

Homann, T., 327 Hong Yong, J. W., 195
196 Hongvaleerat, C., 272 Hooshyar, N., 145 Hopia, A., 379
380 Hopmann, C., 289
290 Hori, M., 438 Hosseini, S. E., 166 Howard, L. R., 209
210 Hradecky, J., 165
166 Hrnˇciˇc, M. K., 60 Hruskova, I., 443t Hsu, C.-P., 122 Hu, W., 71 Huang, H.-W., 2, 102, 106, 114, 122 Huang, S. W., 379
380 Huang, Y.-F., 465 Hubbermann, E. M., 352 Huda, N., 502
505 Huisman, I. H., 266
267 Hulle, N. R. S., 65 Huma, Z., 476 Hungerbu¨hler, K., 213
214 Hunt, A. J., 60f Huo, C.-Y., 104t Huotari, H. M., 266
267 Huppertz, T., 102, 106 Hussein, M. H. M., 167 Hyldgaard, M., 375 I Iannone, R., 72 Iban˜ez, E., 59, 71
72, 77, 318
319 Iba´n˜ez, E., 57, 193
204, 196f, 207, 210, 213, 318
319 Ibrahim, S. A., 375 Icier, F., 165
166, 168t, 173, 177 Idlimam, A., 501t, 506 Ignat, A., 413 Igwe, C. C., 315 Ileleji, K., 440 Ileleji, K. E., 440 Ili´c, J. D., 268 Indora, S., 501t Indrani, D., 351 Indrawati, O., 119 Infante, J. A., 117 Iniyan, S., 499 Innocente, N., 432

Author Index

Inoue, S., 296 Ionita, M.-D., 432, 442f Irudayaraj, J., 395 Irwe, S., 98
100 Isailovı´c, B. D, 350
351, 354 Iseki, S., 438 Ishikawa, K., 432, 438 Isik, B. S., 352 Islek, C., 110 Ismail, A., 110 Ismail, N., 3 Isobe, S., 297 Isteniˇc, K., 345 Ivorra, B., 117 Izquierdo, P., 146
147 J Jacks, T. J., 221 Jackson, R. S., 418 Jackson-Davis, A., 375 Jacobsen, T., 432 Jacotet-Navaro, M., 43t Jae, W. P., 173
174 Jaeger, H., 160
161, 165, 418 Jaeschke, D., 178, 180t Jafari, S. M., 146
148 Jaffrin, M. Y., 266 J¨ager, H., 422
423 Jahnz, U., 352 Jain, A., 336
337 Jako´b, A., 168t, 173 Jalte, M., 422, 424 Jalvo, B., 260 James, C., 473 James, G. L., 166 James, S. J., 473 Jang, J.-H., 41t Jangchud, A., 474 Jange, C. G., 348 Janowicz, M., 465 Jaouen, P., 281 Japip, S., 261, 277 Jaramillo, B. E., 477
480 Jarrault, C., 281 Javidnia, K., 177 Jayaraman, S., 505t Jayas, D. S., 88 Je˛drzejczak, R., 3 Jenness, R., 149

525

Jensen, J. L., 440 Jensen, N., 487 Jentzer, J. B., 206 Jeyaratnam, N., 478t Jhamandas, J. H., 206
207 Ji, L., 469, 470t Jia, Z., 346 Jiang, H., 278 Jiang, S., 163
164 Jiang, Y. M., 110 Jiao, B., 250 Jimenez, A. R., 344 Jime´nez, J. A., 348 Jime´nez, L., 199 Jiranek, V., 40 Jittanit, W., 166, 175
177, 180t, 181
182 Jo, C., 432, 435
437, 437f, 439
440 John, G., 499 John, H., 267 Johnson, L. A., 297, 318 Jokı´c, S., 76, 210
213 Jomaa, W., 471f Jongrungruangchok, S., 355 Jordan, C. A., 404
405 Jorgensen, S. B., 487 Joseph, G., 95t Jouppila, K., 338t Juan, B., 147, 150 Juliano, P., 87
88, 117, 120 Jun, S., 163 Jun, X., 110 Jung, J., 344
345 Jung, S., 104t Junjie, Z., 110 Jurı´c, S., 352 Jury, V., 166 K Kaderides, K., 338t, 350
351 Kadi, H., 221 Kajda, P., 97 Kala, H. K., 465, 467 Kalb, D. M., 145 Kalusevic, A., 335 Kaluˇsevi´c, A., 344, 346
347, 349
351 Kaluˇsevı´c, A., 345, 353 Kaluˇsevı´c, A. M., 344, 346
347, 349
351 Kamal, S. M. M., 199 Kamalakanth, C. K., 95t

526

Kanakis, C. D., 43t Kandpal, T. C., 501t Kang, D. H., 167, 168t Kangas, N., 297 Kanjanapongkul, K., 163
164, 166, 180t, 181 ¨ ., 210
213 Kanmaz, E. O Kanner, J., 380 Kappe, C. O., 488 Kar, S., 206
207 Karaˇca, S., 345
346 Karadag, A., 199
204 Karam, M. C., 466
467 Karami, A., 177 Karatapanis, A., 376 Karata¸s, S., ¸ 95t Kartika, I. A., 317
318, 326f Karunaratne, D. N., 336, 347 Karwe, M. V., 90
91, 103 Katapodis, P., 97
98, 118, 120 Katare, O., 336
337 Katayama, S., 200t Katsaros, G., 92
94, 97
98, 112 Katsaros, G. I., 92
94, 95t, 97
98, 100 Kaur, S., 432 Kazan, A., 200t, 480 Kechaou, N., 316 Keener, K., 431
433, 440 Keener, K. M., 432, 438
441, 446, 474 Kelly, A., 102 Kelly, A. L., 91, 95t, 106, 112
113, 142, 147
148, 353 Kendirci, P., 166 Kentish, S., 23
24, 26
31, 37
40, 45
46 Keramat, J., 351 Kerfai, S., 306 Kerr, W. L., 346
347 Kerry, J. P., 40, 112
113 Keshavarz, E., 140 Kessler, R., 9 Keum, Y. S., 66 Kfoury, M., 344 Khacef, A., 432 Khadhraoui, B., 49 Khan, M. K., 7
8, 26
27, 37
40, 42
46 Khan, S., 207 Khanam, S., 65 Khanduja, K. L., 508 Khanniri, E., 377

Author Index

Khatun, B., 346 Khaw, K. Y., 59 Kheadr, E. E., 151 Kheirkhah, H., 199
204 Khoddami, A., 9 Khomeiri, M., 345 Khorshidian, N., 377 Khoza, B. S., 200t, 204
205 Khuenpet, K., 180t, 181
182 Khuwijitjaru, P., 209
210 Kilercioglu, M., 337
344 Kim, H.-G., 265
266 Kim, K., 404
405 Kim, K. M., 167 Kim, S. S., 167, 168t Kimura, Y., 210
211 King, J. W., 209
210 King’ondu, C. K., 499 Kino, S., 315 Kiran, S., 386 Kirchhoff, M. M., 193, 194f Kirtchev, N. A., 7 Kleinig, A. R., 149 Klemens, S., 505 Klostermeyer, H., 113 Kludska, E., 165
166 ˇ 60, 62, 77, 318
319 Knez, Z., Knez, Z., 210
211 Knirsch, M. C., 160
161, 165 Knoerzer, K., 97, 117 Knorr, D., 2
3, 5, 41t, 88
89, 92, 93t, 97, 106
108, 110
111, 120, 121t, 418, 422 Ko, M.-J., 205
206 Kodama, S., 445
446 Ko¨hler, K., 141 Kohler, R., 440 Korhonen, H., 103 Kolbe, E., 7, 173
174 Konczak, I., 348 Kong, F. B., 346
347 Kontominas, M. G., 376 Koo, E. C., 317
318 Kor, G., 166 Kosachev, V. S., 325
327 Kosaraju, S. L., 348 Koshevoy, E. P., 325
327 Kostas, E. T., 465 Kostic, A., 346 Kostova, I., 377

Author Index

Kotnik, P., 77 Kotnik, T., 167 Koubaa, M., 2, 5, 7, 316, 319
325, 323f, 324f, 325f, 465 Kouhila, M., 506 Koutchma, T., 7, 93t, 119
120, 121t, 122, 394, 399 Kovacevic, D. B., 206 Kowalczyk, W., 116 Koyu, H., 200t, 480 Krammer, G., 352 Krantz, W. B., 275 Krasaekoopt, W., 335, 349 Krebbers, B., 88, 93t Kretzschmar, U., 440
441 Krijgsman, A. J., 145 Krishnamurthy, K., 395 Kruger, M. C., 347
348 Kruszewski, B., 4 Krzy˙zanowska, J., 4 Kuan, W.-H., 465 Kuipers, N. J. M., 316 Kuldiloke, J., 41t Kulozik, U., 346
347 Kulurel, Y., 502, 503t Kumar, A., 375 Kumar, P., 375 Kupchik, M. P., 172
173 Kurniawansyah, F., 74 Kurtulus Ozturk, T., 200t Kurz, T., 30 Kusano, Y., 432 Kwon, J. H., 175 Kwon, J.-H., 58
59 Kylli, P., 338t Kyllo¨nen, H., 39t Kyllo¨nen, H. M., 266 Kyriakopoulou, K., 97 L la Fuente, M. A., 106 La Scalia, G., 277 Labatut, M.-L., 281 Labbett, D., 348 Labonne, L., 308 Labuza, T. P., 90
91, 120 Lacaze-Dufaure C., 310 Lachos-Pe´rez, D., 199, 200t, 209 Lacombe, A., 438

527

Lacroix, M., 376 Lacroix, N., 151 Lafarga, T., 103 Lagha, A., 49 Lagunas-Solar, M., 2 Lahsasni, S., 506 Laine, P., 338t Laisney, J., 317
318 Lakkakula, N., 177, 179
181, 180t Lakshmi, D. V. N., 501t Lalitha, K. V., 95t Lameiras, J., 335
336 Lameloise, M.-L., 248
249, 277, 279
281 Lamo-Castellvı´, S. D., 353 Lamrous, O., 221 Lamsal, B. P., 318 Lanciotti, R., 149 Lanier, T. C., 112
113, 469 Lanoisele´, J. L., 317
318 Lanoiselle´, J.-L., 405
406, 422 Lanoiselle, J.-L., 422 Lardie`res, J., 147 Larkeche, O., 65 Larocque, P., 296 Laroussi, M., 438 Lascorz, D., 166 Lau, H. H., 347 Lauber, S., 113 Laugier, F., 23
24, 26
27, 29
32, 34 Laurindo, J. B., 473 Lauro, M. R., 350
351 Lauterborn, W., 30 Lavinas, F. C., 95t Law, C. L., 472, 475 Law, D., 354 Layek, A., 501t Lazarenko, E. M., 443t Lazennec, F., 104t Le, N. L., 277 Leadley, C., 88 Leal, P. F., 67 Le-Bail, A., 166 Lebovka, N., 404
406, 409f, 414, 422
423, 422f, 423f, 424f Lebovka, N. I., 168t, 172
173, 175
176, 405
406, 407f, 408f, 414, 417
418, 417f, 422
423, 425f Lecomte, D., 317
318 Ledward, D., 88

528

Lee, C. H., 167 Lee, C. Y. J., 167 Lee, H., 41t Lee, H. S., 110 Lee, H.-Y., 93t Lee, J., 27
28 Lee, J.-H., 205
206 Lee, S. H., 147 Lee, S. K., 113 Lee, S. Y., 167, 168t Lee, S.-H., 296 Lee, T., 440 Lee, W. G., 404
405 Lefe`vre, T., 147 Legrand, J., 142 Lei, L., 174 Leipold, F., 432 Leiteritz, L., 39t Leizerson, S., 166 Lema, J. M., 318 Lemay, M. J., 376 Lemmenes, B., 395
396 Lemmon, E. W., 111 Len, C., 464 Lenaerts, S., 484t Lenza, E., 149
150 Leong, T., 27
28, 45
46 Lepreux, L., 7, 316, 325f Levaj, B., 1
2, 7
8 Levelt Sengers, J. M. H., 111 Levic, S., 335 Levi´c, S., 344, 346
347, 349
351 Levı´c, S. M., 344, 346
347, 349
351 Lewandowski, R., 248
249, 277, 279 Leyris, J., 297
299 Li, B., 261, 277 Li, B.-S., 112
113 Li, M., 278 Li, W., 273
274 Li, Y., 318 Li, Y.-Y., 278 Li, Z., 469 Lian, G., 354 Liang, L., 353 Liang, W., 41t Liao, X., 71 Lienhard, V., 267 Lienqueo, M. E., 145
146 Liew, S. Q., 206
207

Author Index

Lignot, B., 281 Limnaios, A., 111
112 Lin, L., 206
207 Lin, Y. C., 500
502, 503t Lin Teng Shee, F., 256 Lind, M., 487 Lindahl, S., 207 Linden, K. G., 394 Lindquist, E., 209
210 Ling, L., 443t Lingnert, H., 381 Link, J. V., 473 Links, M. R., 347
348 Lipnizki, F., 264, 271
273 Lipshtat, O., 165 List, G. R., 315 Liu, B., 344 Liu, C., 422
423, 422f, 475 Liu, D., 48
49, 144
146 Liu, D.-H., 43t Liu, F., 467
468 Liu, G., 112 Liu, J., 204
205, 207, 209, 211 Liu, K., 208, 221 Liu, L., 166 Liu, R., 278 Liu, S., 160
162, 205 Liu, T., 413 Liu, W., 469 Lo, R., 337 Lodeiro, C., 29
30 Loftsson, T., 344 Loghavi, L., 167, 168t Loginova, K. V., 407f, 414 Lopes, M. L. M., 95t, 111 Lopes-da-Silva, J., 98 Lopez-Cordoba, A., 338t, 345 Lopez-Fandino, R., 106 Lo´pez-Fandin˜o, R., 102, 104t Lo´pez-Malo, A., 386
387 Lopez-Nicolas, J. M., 344 Lo´pez-Padilla, A., 75
77 Lo´pez-Pedemonte, T., 142 Lo´pez-Rubio, A., 338t Lo´pez-Tobar, E., 355 Lorentz, C., 337 Lorenzo, J., 1
2, 7
8 Lorenzo, J. M., 1, 5 Lorimer, J. P., 32, 45
46

Author Index

Louisnard, O., 23
24 Louka, N., 181, 228
229, 418
420 Lourdes, M. C. C., 272 Lovrı´c, V., 9 Loypimai, P., 176
177, 179
181, 180t Lozano-Ojalvo, D., 102, 104t Lozano-Vazquez, G., 338t Lu, J., 104t Lu, J.-K., 2, 102 Lu, P., 418 Lu, W., 353 Lu, Y., 275 Lucas-Abellan, C., 338t, 344 Lucas-Abella´n, C., 338t Lucchesi, M. E., 477
480 Lucini, L., 1 Ludikhuyze, L. R., 98, 117, 121t Luengo, E., 43t, 417
418 Luja´n-Facundo, M. J., 268 Luna-Rodriguez, L., 29 Lundin, L., 348 Luo, Y., 345
346 Lupacchini, M., 8 Lupo, B., 353 Luque De Castro, M. D., 43t Luque de Castro, M. D., 476
477 Lutin, F., 248
249, 277, 279
280 Lv, H., 473 Ly Nguyen, B., 97
98 Lyng, J. G., 41t, 166, 413, 484t M Ma, D., 432 Ma, H., 43t, 222
223 Ma, Y.-Q., 43t Mac Tavish, D., 206
207 MacCarty, N., 504t Macedo, B., 173 Machado, A. P., 350
351 Machado, A. P. D. F., 63
64, 69
72 Machado, B. A. S., 59 Machado, L. F., 167, 168t Macı´as-Sa´nchez, M. D., 66 Macquarrie, D. J., 403 Madala, N. E., 200t Madinah, I., 470t Madoumier, M., 273
274 Madsen, R. F., 264 Maeda, A., 210
211

529

Maesmans, G., 119 Maestro, A., 353 Mag, T., 317
318 Magdalena, A., 375 Maggi, A., 119 Maghsoudlou, Y., 345 Magureanu, M., 432, 442f Mahadevan, S., 90
91, 103 Mahammadunnisa, S., 441 Mahanta, C. L., 338t Mahdavi, V., 440 Mahendran, R., 440 Mahian, R. A., 375 Mahmoud, E. A., 440 Mahmud, M. A. P., 502
505 Mahniˇc-Kalamiza, S., 167 Mahnot, N. K., 338t Mahrouz, M., 506 Maingonnat, J.-F., 8
9, 476 Majetich, G., 476 Maji, T. K., 346 Majid, A. E., 316, 323f, 324f Majid, I., 37
39 Majzoobi, M., 177 Makhlouf, J., 151 Makroo, H. A., 173 Maldonado, J., 90
91 Malik, M. A., 441 Maltezou, I., 92
94 Mammucari, R., 74 Manach, C., 199 Manas, P., 41t Mandache, N. B., 432, 442f Mandal, V., 465 Manibog, F. R., 504t, 508 Manoj Kumar Reddy, P., 441 Manojlovic, V., 335 Manouchehri, R., 177
178, 180t Mansoori, G. A., 73
74 Mantegna, S., 338t, 355 Mantle, D., 382t, 384
386 Manzocco, L., 7, 413 Maras, M., 2 Marchal, L., 172
173 Marciniak, A., 103 Marconi, O., 67 Marcotte, M., 159
160 Marczak, L. D. F., 165, 176
177, 275 Mare´chal, F., 71
72

530

Mare´chal, P. A., 111 Maresca, P., 102, 104t, 149
150, 152 Margosch, D., 93t Marı´c, M., 7 Marina, M. L., 195
196 Mariotti-Celis, M. S., 200t, 205, 210
211 Markov, M. S., 404
405 Maroun, R., 181 Maroun, R. G., 418
420 Marra, F. P., 277 Marriott, R. J., 316 Marrone, B. L., 145 Marrone, C., 70 Marszałek, K., 3
4 ´ ., 60, 337 Martı´n, A Martin, C., 291 Martin, G. J. O., 145
146 Martin, J. H., 150 Martin, L., 316 Martı´n, M. J., 336 Martin, S. E., 41t Martin-Belloso, O., 146
147, 377, 425
426 Martı´n-Belloso, O., 97 Martı´nez, J., 68
72, 75, 77
78 Martı´nez, J. L., 67 Martı´nez, J. M., 417
418 Martinez, J. R., 477
480 Martinez-Rodriguez, A. J., 277 Martinez-Villaluenga, C., 102 Martini, S., 39t Martino, M., 337, 345 Martino, M. N., 345
346 Martins, R. C., 165, 167 Martynenko, A., 6
7, 433 Mason, T. J., 23
30, 32, 40, 42
46, 222
223, 230, 477 Masotti, F., 273
274 Masschalck, B., 95t, 148
149 Masson, M., 344 Mastrocola, D., 348 Mastwijk, H. C., 377 Mathe, E., 375 Mathew, A. P., 260 Mathys, A., 111, 150, 152 Matinier, H., 248
249 Matos, F. J. A., 478t Matser, A. M., 88 Matsumura, Y., 208
209 Mattar, J. R., 425
426, 425f

Author Index

Mattea, F., 60 Mattea, M., 70 Mattia, C. D., 348 Mattil, K. F., 318
319 Mau, J. L., 381, 382t, 386 Maubois, J. L., 274 Maureira, H., 106 Maurel, A., 255
256 Maurya, V. K., 472 Mawson, R., 8 Mawson, R., 45
46 Mayanga-Torres, P. C., 71
72 Mayen, M., 475 Mazi, B., 474 Mazi, B. G., 474
475 Mazi, I. B., 474
475 Mazzei, R., 277 Mazzutti, S., 199
205, 200t McClements, D. J., 146
147, 337, 355 McConnell, M. A., 103 McDonnell, K., 144
145 McHugh, T. H., 43t, 222
223 Meda, V., 316, 465 Media, A., 375 Medina, M., 112, 475 Mehta, R., 465 Meireles, A. M. A., 65 Meireles, M. A. A., 59
67, 71
72, 75
78, 206
207, 318
319 Mejuto, J. C., 344 Meklatia, B. Y., 48
49 Mendes, A., 273 Mendiola, J. A., 59, 195
196, 196f, 198, 213, 315
316, 318
319 Mendis, D. A., 438 Mendonca, A., 375 Mendoza, J. M. F., 481
482 Mendoza-Roca, J. A., 268 Menegol, T., 178 Meneguzzi, A., 281 Meniai, A.-H., 65 Mercader-Ros, M. T., 338t Meredith, R. J., 459, 462 Merida, J., 475 Mery, Y., 482, 486 Mesı´as, M., 165
166 Metaxas, A. C., 459, 462 Meullemiestre, A., 8
9, 48
49, 478t Meyer, P., 88

Author Index

Meyer, R. L., 375 Mezetykov, Z. A., 325
327 Meziane, S., 221 Mezzomo, N., 75 Mhemdi, H., 7, 315
316, 323
324, 323f, 324f, 325f, 414
416, 415f, 416f Miao, S., 353 Micale, R., 277 Michelino, F., 4
5 Michiels, C. W., 95t, 148
150 Middelberg, A. P. J., 144
145, 149 Mierzwa, D., 48
49 Miglioli, L., 119 Miguel, G., 381
384, 382t Miguel, M. A. L., 95t Mikhaylin, S., 273 Miklavcic, D., 167, 404
405, 414, 417
418, 425
426 Milı´c, J. R., 344, 346
347, 349
351 Millao, S., 65 Miller, B., 150 Miller, E. E., 384 Mills, J., 317
318 Milosavljevi´c, V., 440, 445
446 Min, S. C., 438 Minerich, P. L., 90
91, 120 Minnaar, A., 338t Mir, L. M., 404
405 Mishra, P. K., 375 Miˇs´ıc, D., 336 Misra, N. N., 2, 6
7, 432
434, 437f, 438
441, 445
446, 445f Mitani, T., 200t Mitchell, S. L., 117 Miyashita, F., 64 Moates, G. K., 123 Mocquot, G., 274 Mohamed, R. S., 73
74 Mohammed, K., 501t Moharram, H. A., 26
27 Moiseev, T., 435
439, 445
446 Mok, C., 438, 440 Molina, A. D., 117 Molina, E., 102 Molina-Garcia, A. D., 116 Moncada, J., 73 Mongenot, N., 39t Monrad, J. K., 209
210 Monsalve, M. T., 145
146

531

Montanari Junior, I´., 70 Monteiro, R. L., 473 Montesano, D., 1 Montgomery, N., 396 Moon, K.-D., 41t Moongngarm, A., 176
177 Moontree, T., 176
177 Moore, M., 140 Moo-Young, M., 145 Moraes, M. N., 75
78 Morais, A. R., 351 Morales, F. J., 165
166 Morales-de la Pen˜a, M., 97 Morand, C., 199 Moraru, C., 399 Moreira, M. M., 200t, 205 Moreno, A., 488 Moreno, H. M., 112
113 Moreno, J., 172
173 Moreno, J., 168t, 172
173 Morgan, D. J., 41t, 166, 484t Morris, V. J., 9 Morrissey, M. T., 173
174 Morrow, R., 163
164 Mortazavian, A. M., 377 Mortimore, S., 486
487 Mosqueda-Melgar, J., 377, 425
426 Mostafa, M. M., 501t Motoki, M., 112
113 Motuzas, J., 275 Mou, D., 337
344 Mouloungui Z., 297, 310 Mounir, S., 226
227 Mounts, T. L., 315 Mousavi Khaneghah, A., 441 Moutiq, R., 375 Mozafari, M. R., 335
336 Mueller, D., 353 Muir, J., 465 Mujumdar, A. S., 472 Mukherjee, D., 147 Mukherjee, S., 147 Mukhopadhyay, M., 67 Muller, G., 407f Mu¨ller, M., 316, 325, 327 Mulvaney, S., 69 Munir, A., 7, 502, 503t Munir, M. T., 199
204, 200t Munoz, B., 41t

532

Munoz, C., 106 Murphy, A., 163
164 Murphy, F., 144
145 Murphy, P. M., 95t Murthy, K., 110 Musina, O., 1
2 Mussa, D. M., 95t Mussatto, S. I., 346 Mustapa Kamal, S. M., 199
204 Muthukumar, P., 501t Muthukumaran, P., 74
75 Mwampamba, T. H., 508 Mygind, T., 375 N Nabil, K., 501t Naderi, N., 103 Nahar, N. M., 501t Naik, S., 316 Naik, S. N., 465 Nair, G. R., 179
181, 180t Nakamura, S., 200t Nam, H.-H., 205
206 Nanda, V., 37 Nastic, N., 200t Nath, K., 270, 273
274 Na´thia-Neves, G., 65 Natı´c, M. M., 336 Navarro, A. S., 337, 345
346 Naves, Y., 371
372 Nayak, P. K., 501t Nayik, G. A., 37 N’Diaye, S., 296 Nedovic, V., 335
337, 345, 351
353, 355 Neff, W. E., 315 Nepote, V., 377 Neumann, E., 404
405 New, C. Y., 488 Ng, J. W., 350
351 Ng, W. K., 350
351 Ngoh, G. C., 206
207 Nguyen, L. T., 178
179 Ni, Y., 353 Niakousari, M., 177
178 Nicoli, M. C., 7, 413 Nie, A., 438 Niemi, K., 435
437 Niinim¨aki, J., 296
297 Nikitine, C., 61

Author Index

Nilsson, A., 200t Nilsson, M., 264
265 Nimalaratne, C., 104t Ningsanond, S., 272 Nir, O., 277, 279 Niranjan, K., 2
3 Nkhonjera, L., 499 Noci, F., 41t Noguchi, A., 297 Nogueira, G. C., 65 Nolasco, S. M., 221 Nonus, M., 425f Nordberg Karlsson, E., 207 Norton, B., 507 Norton, I. T., 268, 348 Nunes, D. S. V., 5 Nunes, G. L., 337
344 Nunes, S. B., 59 Nunes, S. P., 277 Nunez, M., 112 Nunez, M. J., 318 Nunez-Delicado, E., 338t, 344 Nu´n˜ez-Delicado, E., 338t Nunez-Mancilla, Y., 112 Nuortila-Jokinen, J., 39t Nyam, K., 352 Nystro¨m, M., 39t, 266 O Oancea, A., 351 Oberlin, C., 458
459 O’Bryan, C. A., 375 Ochi, T., 315 O’Connor, P. M., 95t O’Donnell, C. P., 37
40, 41t Oehme, A., 352 Oehrlein, G. S., 438 Ogle, D., 504t Oidtmann, J., 346
347 Ojha, K. S., 37
40, 46 Okladnikov, I. N., 315 Okoh, S. O., 315 Oksman, K., 296
297 Okuro, P. K., 349 Olano, A., 106 Oliveira, C., 167
172 Oliveira, D., 200t Oliveira., 178, 180t Olmedo, R. H., 377

Author Index

¨ lmez, H., 440
441 O Olorunyolemi, T., 463t Olsen, K., 104t Olsson, I., 98
100 Omar, R., 199
204 O’Neill, L., 432 Ong, E. S., 195
196, 200t, 206 Ono, R., 443t ¨ nu¨r, ˙I., 2
3 O Oommen, R., 505t Oreopoulou, V., 110 Orfanoudaki, A., 97 Orlien, V., 2
3, 104t, 106
108 Orlowska, M., 396
397 Orlowski, S., 404
405 Orrego, C. E., 346, 351 Orsat, V., 346 Ortiz-Medina, J., 260 Ortmann, R., 440 Osorio-Tobo´n, J. F., 63
64, 67, 77
78 ¨ stergren, K., 264
265 O Ostermeier, R., 422
423 Oswalt, A. J., 298 Otero, L., 116
117 Otte, J., 104t Otte, J. A., 104t O’Toole, G., 440 Ouarnier, N., 279 Oussalah, M., 376 Owolabi, F. A. T., 315 Oyaizu, M., 386 Oyebisi, T. O., 504t Ozcan, S. E., 97 Ozcelik, B., 199
204 ¨ zkan, G., 346
347 O ¨ zkan, N., 166 O Oztop, M. H., 337
344 ¨ ztu¨rk, H. H., 504t O P Pablos-Tanarro, A., 102 Padilha, F. F., 59 Paes, J., 68 Pai, D. A., 350
351 Paidosh, A., 71
72 Paini, M., 337
344, 338t, 350
351 Paiva, M., 226
227 Pakhomov, A. G., 404
405 Pal, P., 432

533

Palacio, L., 273 Palavra, A. M. F., 67 Palou, E., 386
387, 404 Palupi, N. W., 354 Pan, J., 344 Pan, K., 272, 280 Pan, Z., 2, 43t, 222
223 Panagiotou, T., 92
94 Panchev, I. N., 7 Pandey, A. K., 375, 386
387 Pandey, M. C., 165 Pandey, R., 480
481 Paniwnyk, L., 7
8, 23, 26
27, 45
46 Pankaj, S. K., 432, 440, 474 Pantelı´c, M. M., 336 Panti´c, M., 344, 346
347, 349
351 Panza, J. L., 63 Paquin, P., 147, 151 Parat, M. O., 59 Pardes-Lopez, O., 344 Pare´ J. R. J., 477
480 Pareek, S., 472 Parent F., 228
229 Parida, B., 499 Parikh, A., 474 Parisi, B., 93t, 119 Park, C. B., 61, 64 Park, I. K., 167, 168t Park, J. W., 7, 168t, 173
174 Park, S., 435
437 Park, Y.-B., 206
207 Parniakov, O., 43t, 406, 409f, 423
424, 423f, 424f Pˆarvulescu, O. C., 75 Pa¸scal˘au, V., 347 Pascual-Teresa, S. D., 337
344 Pasrija, D., 351 Passos, C. P., 77, 478t Pataro, G., 176, 413, 417
418 Patazca, E., 93t, 119 Pateiro, M., 7 Patel, T. M., 270 Patil, S., 438 Patrignani, F., 149 Patterson, M., 88, 91 Paula, J. T., 70, 76 Paviani, L. C., 70 Pavkov, I., 1 Pavlic, B., 199
204, 200t

534

Pavlovı´c, A. V., 336 Payot, T., 279 Pedersen, B., 123 Pedisı´c, S., 350
351 Pegg, R. B., 346
347 Pellegrino, L., 147 Pen˜as, E., 102 Peng, J., 468, 470t Penna, T. C. V., 160
161 Pennington, D. W., 213
214 Peralta-Hernandez, J. M., 277 Pereda, J., 151 Pereira, C. G., 59, 62
63, 318
319 Pereira, R., 168t, 445 Pereira, R. N., 123, 161
162, 165, 167, 168t, 174
177, 179, 180t Peres, M. S., 348 Perez, E. E., 221 Pe´rez-Correa, J. R., 210
211 Pe´rez-Rodrı´guez, F., 95t Pe´rez-Rodrı´guez, L., 102 Perino, S., 488 Pe´rino, S., 478t Perino-Issartier, S., 8
9, 476, 478t Pe´rino-Issartier, S., 48
49, 478t Perretti, G., 67 Perrut, M., 70
71, 73
75, 316 Persico, M., 256
257 Pert, E., 463t Peshkovsky, A. S., 7
8 Pesic, M. B., 346 Petenate, A. J., 63
64, 67, 75
76 Petersson, E. V., 209, 211 Petigny, L., 48
49 Petit, J., 466 Pe´trier, C., 23 Pflug I. J., 119 Phalak, R., 432 Pham, Q. T., 473
475 Philip, S. K., 505t Phoon, P. Y., 422 Piater, L. A., 200t Picart, L., 139
140, 142, 147
150 Pieber, B., 488 Pierro, V., 463t Pierson, J. T., 478t Pietsch, A., 316, 325
327 Pinela, J., 478t Pingret, D., 23
26, 48
49

Author Index

Pinho, S. C., 348 Pinto, G. A. S., 43t Pinto, J., 164 Pinto-Bustillos, M. A., 277 Pirkonen, P., 39t, 266 Pittia, P., 348 Piyasena, P., 7 Pla, R., 112
113 Plaza, L., 97
98 Plaza, M., 68
69, 193
196, 195t, 199, 200t, 204
205, 207
208, 210
211 Plumel, M. M., 478t Pohlman, F. W., 39t Pol, I. E., 377 Polenta, G., 102 Poletto, M., 70 Polidori, J., 272 Poliseli-Scopel, F., 151 Poliseli-Scopel, F. H., 151 Polissiou, M. G., 43t Polydera, A. C., 97
100, 103 Pontalier, P. Y., 297
298, 307f, 308, 310, 317
318, 326f Poojary, M. M., 2, 144
145 Pootao, S., 180t, 181 Pop, P. A., 375 Popa, M. E., 377 Popa, V. I., 62
63 Porras, M., 353 Porta, G. D., 60 Pothakamury, U. R., 404 Pouliot, Y., 103, 104t, 269f, 272
274 Pourali, O., 210
211 Poussis, I. G., 355 Poux, M., 464 Powell, K., 163
164 Pra´danos, P., 273 Pradhan, R. C., 316 Prado, G. H. C., 75
76 Prado, J. M., 66, 71
72, 75
76 Prakash, B., 375, 386 Praporscic, I., 168t, 172
173, 175
176, 406, 408f, 417
418, 417f Praptiningsih, Y., 354 Prasad, N., 110 Prasad, R., 465 Prasad, R. V., 65 Pratt, D. A., 379 Pratt, D. E., 384

Author Index

Preece, K. E., 145 Preedy, V. R., 375 Prestamo, G., 111 Priprem, A., 348, 354 Priyanka,., 65 Probst, L., 123 Probst, L., 123
124 Proctor, A., 403 Prodanov, M., 277 Pru¨ße, U., 352 Ptasinska, S., 435
437 Pucihar, G., 167 Pue´rtolas, E., 5, 417
418, 420 Puiggali, J. R., 471f Puligundla, P., 438, 440 Pulsfus, S., 395
396 Pupan, N., 474 Purnell, G., 473 Purroy-Balda, F., 122 Putnik, P., 1
2, 5
8, 11
12 Q Qian, C., 146
147 Qian, Y., 104t Qiu, R., 432 Qiu, Y., 438 Qu, W., 43t, 222
223 Queiroga, C. L., 70 Quevedo, J. M., 151 R Rabiller-Baudry, M., 280 Radhakrishna, K., 165 Ragaert, P., 394 Raghavan, V., 472 Raghavarao, K. S. M. S., 2
3, 433
434 Rajabzadeh, G., 354 Rajakumar, G., 9 Rajewska, K., 48
49 Ramanathan, S., 461 Ramaswamy, H., 8
9 Ramaswamy, H. S., 7, 95t, 98, 104t, 159
160, 162, 165
166 Ramı´rez, M. J., 346, 351 Ramos, A. M., 117 Ramos, A. P., 348 Ramos, M., 106 ´ . L., 174 Ramos, O Ramos de Melo, N., 378
379

535

Randeniya, L. K., 432 Ranjan, V., 472 Rao, M. L., 177 Raso, J., 43t, 417
418, 420, 425
426 Rastogi, N. K., 2
3, 106 Ratish Ramanan, K., 440 Rauh, C., 92, 116, 118 Rauwendaal, C., 289
290 Raybaudi-Massilia, R. M., 377, 425
426 Reader, H. C., 462 Rech, R., 178 Recio, I., 104t Regier, M., 458, 460
461, 487, 489 Reglero, G., 61, 76
77 Regnault, S., 106 Reineke, K., 92, 93t Re˛kas, A., 465 Re´me´sy, C., 199 Remondetto, G. E., 346, 353
354 Rempel, C. B., 316 Ren, D.-F., 104t Rene´, F., 259t, 261 Repaji´c, M., 1
2 Reverchon, E., 60
62, 70, 76
77 Reverte-Ors, J. D., 470t Rey, J. M., 117 Reyes-Villagrana, R., 29 Reynes, M., 267, 272, 275 Reˇzek Jambrak, A., 1, 6
7 Rhee, K. C., 318
319 Rhodehamel, E. J., 93t Riahi, E., 98 Rial-Otero, R., 344 Ribeiro-Santos, R., 378
379 Ricci, D., 382t, 386 Richard, N., 95t Richter Reis, F., 164
165 Ricke, S. C., 375 Riehl, C. A. S., 71
72 Riemma, S., 72 Rigal L., 206, 296
298, 307f, 308, 310, 317
318, 326f Rios, G. M., 275 Ristivojevı´c, P., 336 Rivera, X. C. S., 484t Rizvi, S. S. H., 69, 73
74 Robert, M. C., 88
89 Robert, P., 338t, 344, 347 Roberts, T., 9

536

Robinson, C. W., 145 Robinson, J. P., 465 Rocchetti, G., 1 Rocha, C. M. R., 175, 178 Rocha, J. S., 348 Rocha, S. M., 95t Rocha-Parra, D., 337
344, 338t, 351 Rochas, J. -F., 458
459 Rocha-Santos, T. A. P., 59 Rodarte, D., 147 Rodier, E., 61, 316 Rodrigo, D., 98 Rodrigue, D., 289
290 Rodrigues, R. M., 174 Rodrigues, S., 43t Rodrı´guez, E., 112 Rodrı´guez, J., 336 Rodriguez-Corral, G., 39t Rodrı´guez-Meizoso, I., 68
69, 72, 207, 214 Rodriguez-Narvaez, O. M., 277 Rogalinski, T., 208 Rohm, H., 39t Roig-Saugue´s, A. X., 151 Rojas-Grau, M. A., 146
147 Roller, S., 377 Rombaut, N., 8
9, 26
27, 222
223, 231 Romdhane, M., 477
480 Roohinejad, S., 1
2 Rosa, P. T., 75 Rosal, R., 260 Rosales, E. J., 346
347 Rosec, J.-P., 95t Rosello´-Soto, E., 7 Rosenberg, M., 438 Rosi, V., 147 Rossing, N. L., 487 Rostagno, M. A., 63
64, 67, 71
72 Rouaud, O., 166 Roudaut, G., 349 Rouilly, A., 297 Roussy, G., 458
459 Rout, P. K., 316 Roux, S., 165
166 Roux-de Balmann, H., 248
249, 277 Rovere, P., 93t, 119 Ruberto, G., 381 Rubilar, M., 145
146 Ruedt, C., 354 Rui, Z., 110

Author Index

Ruiz, K., 477
480, 478t Ruiz, M. A., 336 Ruizhan, C., 110 Ruiz-Jime´nez, J., 43t Ruiz-Rodriguez, A., 76
77 Ryan Keogh, D., 441 Ryu, S., 167, 168t S Sabaghi, M., 345 Saberian, H., 177, 180t Sablani, S. S., 467
468 Sacchetti, G., 348, 382t, 384
386 Sack, M., 407f, 420 Safi, C., 144
146 Sagne, C., 279 Sagong, H. G., 168t Saguer, E., 112
113 Saharkhiz, M. J., 177 Sahin, S., 7
8, 484t Sahoo, L. K., 501t Saidur, R., 502
505 Saikia, S., 338t Saini, R. K., 66 Saito, T., 404
405 Sakai, K., 315 Sakr, M., 160
162 Salamah, S., 470t Salazar, F., 2 Saldan˜a, G., 417
418, 425
426 Salea, R., 67, 75
76 Salgo´, A., 476 Salim, K. M., 499 Salim, N. S. M., 472 Salinas-Roca, B., 97 Salmie´ri, S., 376 Salplachta, J., 207 Salvador Ferreira, S. R., 199
204 Salvia-Trujillo, L., 146
147 Samaranayake, C. P., 168t, 173 Samhaber, W. M., 267 Sampedro, F., 98 Sanches-Silva, A., 378
379 Sanchez, V., 344, 351 Sa´nchez-Camargo, A. D. P., 57
59 Sanchez-Cortes, S., 355 Sandahl, M., 204
205 Sandeaux, J., 279
280 Saner, S., 199
204

Author Index

Sani, A. M., 375 Sant’ana, A. S., 64 Sant’Anna, V., 275 Santos, D. T., 60, 64
65, 71
72, 206
207 Santos, H. M., 29
30, 32 Santos, L., 335
336 Santos, L. M. N. B. F., 161
162, 164 Sanz, D., 41t Sanz, P. D., 116
117 ˇ Saponjac, V. T., 346
347, 351 Sarah, M., 470t Saraiva, J. A., 95t, 98 Sarangapani, C., 432, 440
441 Saravana, P. S., 193
194, 206
207 Saravia, L., 501t Sarkar, B., 266
267 Sarkis, J. R., 165, 176
177 Sarmah, M., 346 Sarumathi, R., 440 Sastry, S., 159
160, 163, 167 Sastry, S. K., 164
167, 168t, 173, 176
181, 180t Sato, H. H., 151 Satpathy, S. K., 465 Sauceau, M., 61, 69, 74 Saucier, L., 376 Saurel, R., 349 Savoire, R., 317
318 Savvaidis, I. N., 376 Sawamura, M., 385 Saxena, J., 168t, 173 Scalbert, A., 199 Scales, P. J., 145
146 Scanlon, M. G., 316 Scannell, A. G. M., 41t Scaramuzza, N., 119 Scher, J., 466 Scheweiggert, R. M., 210
211 Schiweck, H., 413
414 Schler, J., 165 Schmiele, M., 293 Schollers, P., 500 Schreier, P., 352 Schroe¨n, C. G. P. H., 265
266 Schubert, H., 139
140, 147
148, 458, 460
461, 487, 489 Schuchmann, H. P., 141 Schuck, P., 227 Schulz, J., 327

537

Schulz, M., 418, 422 Schutze, A., 434
435 Schwartz, K., 379
380 Schwartz, T., 413
414 Schwarz, K., 352 ´ Scibisz, I., 465 Seabra, I. J., 68, 70
72 Seedhar, P., 377 Segat, A., 432 Segovia, O., 97 Seguro, K., 112
113 Sekiguchi, H., 445
446 Selemir, V. D., 443t Sen, K. K., 465 Sendra, E., 95t Sengpiel, R., 277 Sengun, I. Y., 166 Sensoy, I., 164
165, 168t, 176
179, 180t Seog, J., 438 Sera´, B., 443t Sereda, K., 172
173 Sereewatthanawut, I., 208, 210 Sergelidis, D., 377 Serra, X., 112
113 Serrano-Cruz, M. R., 346
347 Serrato, A. G., 221 ˇ ´ , M., 443t Sery Sessa, M., 147 Sessa, M., 335 Sevenich, R., 92, 150, 152 Sevgili, L. M., 8 Shahbaz, H. M., 58
59, 175 Shahgholian, N., 354 Shahidi, F., 177 Shakya, A., 472 Shaltout, O. E., 26
27 Shamsudin, R., 115t, 122 Shao, P., 338t Shao, Y., 95t Sharaf, E., 501t Sharma, A., 43t Sharma, V., 435
437 Shaw, P. N., 59 Shene, C., 145
146 Shi, G., 337 Shi, H., 440 Shi, J., 110 Shi, S., 43t Shilpi, A., 63

538

Shimoni, E., 166 Shin, S. H., 104t Shinde, T., 353 Shiratani, M., 443t Shirsath, S. R., 46
48 Shishir, M. R., 335
346 Shivhare, U., 336
337 Shivhare, U. S., 63 Shouqin, Z., 110
111 Shrigod, N. M., 65 Shrivastava, S. L., 480
481 Shuang, S., 344 Shynkaryk, M. V., 417
418, 417f, 422
423 Shynkaryk, N. V., 422 Shyu, Y.-T., 2, 102 Siajam, S. I., 199
204 Sicaire, A.-G., 8, 508
509 Siemer, C., 413, 422
423 Siger, A., 465 Sigler, J., 407f Siguemoto, E´. S., 472 Sila, D. N., 98 Silva, A. M. G., 164 Silva, A. M. S., 161
162, 164 Silva, C. M., 77, 318
319 Silva, E. K., 60
62, 64
65 Silva, G. S., 348 Silva, L. P. S., 77
78 Silva, P. S., 268 Silva, V. L. M., 161
162, 164 Silvan, J. M., 277 Silva-Weiss, A., 354 Silvestre, A. J. D., 318
319 Simal-Ga´ndara, J., 344 Sima´ndi, B., 70 Simons, L., 8, 45
46 Simpson, R., 168t, 172
173 Sineiro, J., 318 Singdeo, D., 163
164 Singh, A., 376 Singh, K. K., 297 Singh, N., 376 Singh, P., 375 Singh, R. D., 465 Singh, R. K., 346
347, 376 Singh, T., 2 Sinigaglia, M., 375 Sionek, B., 315 Siow, L. F., 355

Author Index

Sipoli, C. C., 338t Sirisansaneeyakul, S., 181
182 Sivachandiran, L., 432 Sjoberg, P. J. R., 204
205, 209 Ska˛pska, S., 3
4 ˇ Skerget, M., 60, 77, 210
211 Skibsted, L., 104t Skinner, C., 316 Sladan˜a, G., 420 Sleator, R. D., 91 Slump, R. A., 377 Smadja, J., 477
480 Smania, A., 71
72 Smania, E. F. A., 71
72 Smelt, J. P., 91 Smid, E. J., 377 Smith, J. P., 95t Smith, N. A. S., 117 Smith-Palmer, A., 377 Smout, C., 97
98 Sokołowska, B., 4 Solans, C., 146
147 Soliva-Fortuny, R., 146
147 Solomon, H. M., 93t Somavat, R., 167, 168t Sommers, C. H., 395
396 Sonawane, S. H., 46
48 Song, C., 472 Song, H. S., 385 Song, Q., 272 Sonibare, J. A., 504t Sonune, A. V., 505t Soquetta, M. B., 64 Soria, A., 26, 48
49 Soria, A. C., 7
8 Sousa, I. M. O., 70 Souza, B. W. S., 168t, 174 Souza, V. B., 354 Sowers, A. E., 404
405 ˇ Spani´ c, I., 1
2 Spatenka, P., 443t Spe´randio, M., 482 Speranza, B., 375
376 Spiden, E. M., 145
146 Spilimbergo, S., 4 Spyropoulos, F., 268 Spyropoulosa, F., 268 Sreekumar, A., 500 Srinivas, K., 209
210

Author Index

Srivastava, B., 173 Stangle, R., 407f Stanisavljevı´c, N. S., 336 Stanojevic, S. P., 346 Starov, V. M., 268 Stashenko, E. E., 477
480 Statkus, M. A., 197 Stavros, P., 98 Steel, C. J., 293
295 Steenkamp, P. A., 200t Stewart, J., 377 Still, D., 504t Stoforos, N. G., 88
89, 97, 119 Stoica, A., 75 Stola´rik, T., 442, 443t ˇ ˜ a´k, V., 443t Stran Strathmann, H., 255 Strati, I. F., 110 Stratton, G. R., 441 Stroescu, M., 75 Stroshine, R. L., 440 Strube, J., 48
49, 500 Stryczewska, H. D., 432 Stukenbrock, L., 407f Stuknyt˙e, M., 273
274 Sturzoiu, A., 75 Su, Y., 475 Suarez-Jacobo, A., 151
152 Suaylam, B., 209
210 Subaric, D., 210
211 Subirade, M., 147, 346, 353
354 Subrahmanyam, C., 441 Sudhakar, N., 443t Suh, J.-W., 104t Suh, N. P., 64 Sun, B., 206
207 Sun, C., 335 Sun, D.-W., 48
49, 484t Sun, H., 165, 167 Sun, J., 144
145, 344
345 Sun, P., 338t Sun, Y., 438 Sundararajan, R., 404
405 Sun-Waterhouse, D., 353 Sunwoo, H., 104t Surampalli, R. Y., 43t Surel, O., 443t Suthanthangjai, W., 97 Suwal, S., 103, 104t, 256
257

539

Suzuki, A. H., 39t Swanson, B. G., 404 Syamaladevi, R. M., 440 T Tabil, L. G., 465 Tachibana, M., 432 Taddeo, R., 70 Tadini, C. C., 472 Tadpitchayangkoon, P., 173
174 Tadros, T. F., 146
147 Taga, M. S., 384 Taher, B. J., 473
474 Takasuke, I., 174 Takayama, M., 432 Takeuchi, M., 315 Takhar, P. S., 474 Talmaciu, A. I., 62
63 Talo´n, E., 345 Tamayo, J. A., 73 Tampieri, F., 441 Tamura, K., 64 Tan, C. K., 206
207 Tan, R. B., 350
351 Tan, S. N., 195
196, 206 Tandey, R., 465 Tandya, A., 74 Tang, C. Y., 273
274 Tang, J., 278, 467
468, 470t Tang, Y., 432 Tang, Z., 470t Tanguy, G., 273
274 Tao, H., 344 Taoukis, P., 92
94, 96t, 97, 111
112 Taoukis, P. S., 88
89, 92
94, 97
98, 113, 118
120 Tarantilis, P. A., 43t Tarhan, S., 502, 503t Ta´rrago-Mingo, S., 122 Tasneem, Z., 499 Tassou, S. A., 488 Tauscher, B., 110 Tavantzis, G., 97 Taylor, J., 338t, 347
348 Taylor, J. R., 338t, 347
348 Taylor, T. M., 338t Teh, C. Y., 24
26 Teixeira, A. S., 337, 338t Teixeira, J. A., 167
174, 346

540

Temelli, F., 60
61, 63
64, 68
69, 74, 77, 316 Ten Bosch, L., 440 Teo, C. C., 195
196, 199, 206 Teoh, W. W., 206
207 Tepe, B., 381
385, 382t Teramoto, Y., 296 Terefe, N. F., 106
108 Terefe, N. S., 2
3, 97 Terra, L. D. M., 64 Tesch, S., 147
148 Tessaro, I. C., 176
177, 275 Tetzloff, R. C., 93t Tewari, G., 88 Tewari, J. C., 395 Thakur, D., 336
337 Thawatchaipracha, B., 445
446 The´oleyre, M. A., 271, 279 Thiebaud, M., 139
140, 142, 147, 149
150 Thiering, R., 74
75 Thiruvengadam, M., 9 Thomas, K. E., 507 Thomas-Popo, E., 375 Thong, Z., 261, 277 Thoo, Y. Y., 355 Tia, S., 163
164 Tichy´, M., 443t Tikvah, P., 165 Timilsena, Y. P., 338t Ting, Y.-P., 24
26, 29
31, 42
45 Tiruta-Barna, L., 482 Tiwari, B. K., 8, 40, 41t, 375, 432
434 Tixier, A.-S., 26
27, 222
223, 231 Tjandrawinata, R. R., 67 Toepfl, S., 110
111, 123, 413 Tolun, A., 350
351 Toma, M., 26
27 Tomao, V., 7
8, 24
27, 42
45, 477
480, 478t Tommasini, S., 344 Tomren, M. A., 344 Tonello, C., 101f, 114 Tong, J., 443t Toniazzo, T., 338t, 348, 354 Tonnesen, H. H., 344 To¨pfl, S., 422
423 Torella, E., 166 Torkian Boldaji, M., 166 Tostenson, K., 297

Author Index

Tovar, C. A., 112
113 Tr¨aga˚rdh, G., 264
267 Trespalacios, P., 112
113 Tribuzi, G., 473 Trifkovı´c, K., 345, 347, 354 Trifkovic, K. T., 345 Trifkovı´c, K. T., 353 Tripathi, N. N., 375 Trubachev, I. N., 315 Trujillo, A. J., 147, 150
151 Trung Le, T., 264
265, 267
268 Tsantes, M., 111
112 Tsevdou, M., 92
94, 96t, 113 Tsevdou, M. S., 113 Tsimogiannis, D., 97 Tsironi, T., 92
94, 95t, 112 Tsizin, G. I., 197 Tsoutsos, T., 508 Turcu¸s, V., 375 Turek, E. J., 113
114 Turk, M. F., 418, 419f, 425f Turner, C., 193
197, 195t, 199, 200t, 204
205, 207
210, 213
214 Turner, I. W., 471f Turp, G. Y., 166 Turtoi, M., 2
3 Tyagi, R. D., 43t U Uddin, M. R., 499, 501t Uemura, K., 297 Uitterhaegen, E., 297
301, 300f Ukeda, H., 385 ¨ mit, G., 166 U Umsza-Guez, M. A., 59 Uniacke, T., 106 Unruh, J. A., 39t Uquiche, E., 65 Urzu´a, C., 350
351 Utsumi, N., 64 Uzel, R. A., 207 V Vaca-Garcı´a, C., 206 Vachon, J. F., 151 Vaillant, F., 271
272 Valente Mesquita, V. L., 95t, 111 Valero, A., 95t Valgimigli, L., 379

Author Index

Valko´, K., 476 Vallentin, K., 381 Valotis, A., 352 Valsasina, L., 152 van Bokhorst-van de Veen, H., 438 Van Campenhout, L., 484t Van Den Berg, R. W., 88 Van den Broeck, I., 98, 121t Van Der Borght, M., 484t van der Goot, A. J., 281
282 Van der Plancken, I., 119, 121t van der Sman, R. G. M., 265
266 Van Hecke, E., 405
406, 422 Van Loey, A., 97
98, 119, 121t Van Loey, A. M., 97, 116
117 Van Loey, F., 98 Van Loey, I. A. M., 121t Van Opstal, I., 95t Vandenbossche, V., 297, 308 Vangala, V. R., 350
351 Vanmuysen, S. C. M., 95t Vardanega, R., 71
72, 77
78, 206
207 Vargas, M., 345 Varghese, K. S., 165 Varona, S., 60 Va´squez-Ponce, P., 277 Vassal, L., 274 Vatai, G., 264
265 Vaxelaire, J., 410, 412f, 418, 420f Va´zquez, E., 61 Veen, S. J., 347 Veggi, P. C., 64
66 Veillet, S., 7
8, 26
27, 46, 477
480 Velazquez-Estrada, R. M., 151
152 Velazquez-Lucio, J., 145 Veldsink, J. W., 465 Velikov, K. P., 347 Venter, M. J., 316, 319
321 Venter, R. D., 61 Vera, E., 273 Vera, L. M. S., 164 Verbeyst, L., 98 Verdouw, C., 442 Verdurmen, R., 39t Vergara, D., 145
146 Vergara, M., 210
211 Vergara-Salinas, J. R., 210
211 Vergis, J., 375 Veriansyah, B., 67

541

Verlent, I., 97
98 Vernaza Leoro, M. G., 293 Versteeg, C., 97, 117 Vervoort, L., 120, 121t Vian, M., 508 Vian, M. A., 175, 316, 477
480 Vicente, A., 422, 445 Vicente, A. A., 123, 161
162, 165, 167
175 Vicente, G., 61 Vidal, P. F., 296 Vidcoq, O., 104t Vigano´, J., 69
72 Vilarem, G., 206 Vilkhu, K., 8, 45
46 Villamiel, M., 7
8, 26, 39t, 48
49 Villanueva-Carvajal, A., 346
347 Vinatoru, M., 26
28, 46, 477 Vincekovı´c, M., 1, 6
7, 335 Vinet, J., 308 Viol, W., 440 Violleau, F., 443t Virot, M., 24
26, 42
45, 477
480, 478t Visavale, G., 506 Visentainer, J. V., 75 Visinoni, F., 477
480, 478t Vlasova, N. V., 315 Vogel, R. F., 93t Voges, S., 325
327 Voigt, E., 422 Voilley, A., 349 Volf, I., 62
63 Vorkel’, I. B., 315 Vorlop, K. D., 352 Vorobiev, E., 5
7, 144
145, 167, 172
173, 181, 315
318, 323f, 324f, 404
406, 407f, 408f, 409f, 410, 412f, 414, 415f, 416f, 417
420, 417f, 419f, 420f, 422
423, 422f, 423f, 424f, 425f Voudouris, P., 347 Vrchotova, N., 443t Vu, N. T., 178
179 Vyas, S., 24
26, 29
31, 42
45 W Wagner, M., 165
166 Wajsman, J., 48
49 Waldron, K. W., 123 Walkelyn, P. J., 315
316

542

Walker, T., 177 Walkling-Ribeiro, M., 41t Wallace, C., 486
487 Walstra, P., 139 Wan, A. P., 315
316 Wan, J., 94t Wan, X., 43t Wandrey, C., 336
337 Wang, C.-Y., 2, 102, 122
123 Wang, F., 355 Wang, H., 64, 344 Wang, J., 267, 280 Wang, L., 26
27, 272, 353 Wang, Q., 345
346 Wang, R., 273
275 Wang, S., 472 Wang, T., 73, 297 Wang, W., 338t, 344
345, 353 Wang, W. C., 179
181, 180t Wang, X., 438 Wang, Y., 200t, 205, 472 Wang, Y.-N., 273
274, 280 Wang, Z., 478t Warner, J. C., 316 Warner, K., 315 Warning, A. D., 474 Waterhouse, G. I., 353 Watson, C. E., 150 Weaver, J. C., 404 Webley, P. A., 145 Weemaes, C. A., 121t Weidner, E., 60, 63
64, 69, 74 Weiss, J., 354 Weiss, U., 97 Weller, C. L., 26
27 Wells, J. H., 7 Welti-Chanes, J., 97 Wessel, D. F., 478t Wessling, M., 277 Wiboonsirikul, J., 210
211 Wie, M. B., 206
207 Wieneke, S., 440 Wiesenborn, D. P., 297 Wiktor, A., 422
423 Wilhelms Gut, J. A., 472 Wilkes, M., 9 Willems, P., 315
316, 319
320, 320f Williams, R. C., 111 Witrowa-Rajchert, D., 422

Author Index

Wittlich, P., 352 Wolf, A., 407f Wolfert, S., 442 Wongsa-Ngasri, P., 163
164, 166 Woo, H.-C., 206
207 Wood, R. J., 27
30, 42
45 Woodward, N. C., 9 Wo´zniak, Ł., 3
4 Wroniak, M., 465 Wu, S.-J., 2, 102 Wu, T. Y., 24
27, 42
45 Wu, Y., 422 Wuytack, E. Y., 95t, 148
150 X Xi, J., 110
111 Xia, T., 43t Xie, L., 335 Xie, X., 266 Xiujin, Z., 174 Xu, D. P., 59 Xu, L., 433 Xu, Z., 71 Xue, C., 469 Xue, Y., 469 Y Yadav, B., 440 Yaldy´z, O., 501t Yamashita, C., 344 Yan, S., 43t Yang, B., 260, 344 Yang, B. B., 122 Yang, H., 336 Yang, T. S., 39t Yang, Y., 209
210, 441 Yang, Y. H., 97 Yanık, D. K., 478t Yap, A., 40 Yap, B. H. J., 145
146 Yaylayan, V., 104t Ye, L., 110 Ye, X.-Q., 43t Ye, Y., 266 Yen, H. Y., 500
502, 503t Yepez, X., 433 Yesil-Celiktas, O., 200t, 480 Yildiz, H., 159
160, 165, 173 Yılmaz, F. M., 346
347

Author Index

Yin, Z., 163
164 Yonesu, A., 443t Yong, H. I., 432, 440 Yong, J. W. H., 206 Yong, T. L.-K., 208
209 Yongsawatdigul, J., 168t, 173
174 Yoon, S. W., 167, 168t Yoovidhya, T., 163
164 Yoshida, H., 210
211 Yosuf, Y. A., 115t, 122 Younes, R. B., 221
222 Young, B. R., 199
204 Young, D. J., 355 Young Quek, S., 199
204 Yousef, A. E., 88, 91, 167 Yousefi, M., 377 Youssef, M. M., 26
27 Yue, C. W., 353 Yurdagel, U., 344 Yusoff, R., 206
207 Yusupov, M., 438 Z Zabetakis, I., 97 Zabot, G. L., 65, 75
78 Zaghdoudi, K, 66 Zahn, S., 39t Zaigui, L., 174 Zakaria, S. M., 199
204, 200t Zaman, S. U., 95t Zamora, A., 147, 149, 151
152 Zamora, C., 337
344 Zamora, M. C., 344 Zayas, J. F., 39t Zeece, M., 102, 104t Zeghman L. G., 119 Zeki Haznedaroglu, M., 200t Zell, M., 166 Zeng, X.-A., 48
49 Zenker, M., 41t Zermane, A., 65 Zhang, C., 441

543

Zhang, D., 422 Zhang, G., 344 Zhang, H., 205, 337, 432 Zhang, H. Q., 11
12 Zhang, J., 338t Zhang, L., 337
344 Zhang, M., 344
345, 472, 475 Zhang, R., 77 Zhang, T., 469 Zhang, W., 475 Zhang, Y., 71, 147 Zhang, Z., 43t, 354 Zhang, Z.-S., 227 Zhao, M., 206
207, 338t, 344 Zhao, W., 344 Zhao, Y., 7, 344
345, 355 Zheng, L., 344
345 Zheng, S., 4
5 Zheng, W., 278 Zheng, X., 335 Zheng, Y., 297 Zhi, H., 174 Zhou, B., 41t Zhou, L., 71 Zhou, R., 355, 440 Zhu, S., 95t Zhu, X., 278, 337 Zhu, Z., 7
8, 112
113 Zill-e, H., 7
8 Zill-E-Huma, H., 477, 481, 484t Zimmer, D., 466 Zimmermann, I., 352 Zimmermann, U., 404 Ziuzina, D., 431
432, 438
439 Zmudzinski, R., 327 Zobrist, M. R., 106 Zolotov, Y. A., 197 Zorı´c, Z., 350
351 Zuber, F., 297 Zuidam, N. J., 145 Zulkafli, Z. D., 64

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Subject Index

Note: Page numbers followed by “f” and “t” refer to figures and tables, respectively. A Absorption spectra of raw milk, 397, 398f ABTS test, 384
385 Acoustic cavitation, 26, 33t, 45f pressure, 24
26 wave intrinsic parameters, 27
30 Additives, 289
290 Advanced oxidation processes (AOPs), 441 Agile gas phase chromatography, 232 Agri-food industry, 1
2 manufacturing sector, 431 residue valorization, 71
72 Air sparging, 267 Alfalfa (Medicago sativa), 306 extrusion, 306
308 Alginates, 345 Alkaline phosphatase (AP), 397 Alkoxyl (ROd), 435
437 Allergenicity, 106 Allergens, 106, 107t Alternative cell disruption techniques, 144
145 Aminopeptidases, 97 Amontons’ law, 11
12 Amplitude, 28t of acoustic pressure, 27
28 Amylopectin, 293 Amylose, 293 Analytes, 209 Anisotropic translational random microagitation, 229 Anthocyanins degradation, 176
177 extraction, 68 Antimicrobials, 112 action of plasma species, 437
438

EO as, 375
378 applications in dairy products, 377 applications in meat-based foodstuffs and seafood products, 375
376 applications in vegetables and fruits, 377
378 applications to cereal products, 378 Antioxidant activity of essential oils, 379
381, 382t Antioxidant agents, EOs as, 378
386 antioxidant activity, 379
381 chemical lipid oxidation, 379 inhibition of lipid autooxidation, 381
384 radical-scavenging tests, 384
386 Antioxidant capacity of foods, 102
103 Antisolvent, 60 AOPs. See Advanced oxidation processes (AOPs) AP. See Alkaline phosphatase (AP) Apple skin polyphenol extract (ASPE), 353 Area under curves (AUCs), 12 Arkopharma, French company, 42, 44f ASPE. See Apple skin polyphenol extract (ASPE) Aspergillus niger spores, 395 Atmospheric pressure, 59, 431
434 plasmas, 433
434 Atomized rapid injection solvent extraction process, 74 AUCs. See Area under curves (AUCs) Autooxidation, 379 Autovaporization, 223 Avure, 113
114 B Backflushing, 265
266 Backwashing, 265
266 BACs. See Bioactive compounds (BACs)

546

Bacterial vegetative cells, 92 “Bactocatch” process, 272 Baroresistant enzyme fraction, 98 Basil (Ocimum basilicum L.), 377 β-carotene bleaching test, 384 β-form CDs (β-CDs), 337, 344 BHA. See Butylated hydroxyanisole (BHA) BHT. See Butyl hydroxytoluene (BHT) Bioactive compound extraction degradation, 209 PHWE of, 210
211 from Plantago major and Plantago lanceolata, 199
204 from plants and natural sources, 199 Bioactive compounds (BACs), 1
2, 102
103, 323
324 Bioactive peptides (BPs), 102
103 Bioactive substances, 144
145 Biochemical/chemical stabilization, 270
272 Biocompounds, 175
182 Biological engineering, 163
164 Biomass feedstocks, 407 Biopolymers, 208 Biorefinery process, 71
72 Biosuspensions, PEF impact on, 405
406 BioZone Scientific (BioZone Scientific International, Florida), 434
435 Bipolar membranes (BMs), 248
249 Bis(2-ethylhexyl) adipate (DEHA), 487 Blake threshold, 31 BMED. See ED with BM (BMED) BMs. See Bipolar membranes (BMs) Bovine serum albumin (BSA), 260 BPs. See Bioactive peptides (BPs) Bran, 303
304 Branched amylopectin, 337 Brown macroalgae (Saccharina japonica), 206
207 BSA. See Bovine serum albumin (BSA) Bubbles, 27
28 implosion, 26 Butyl hydroxytoluene (BHT), 378
379 Butylated hydroxyanisole (BHA), 378
379 C Caffeic acid, 209
210 Caffeine production, 72 Campylobacter jejuni, 396

Subject Index

Carbohydrate polymers, 336 Carbon dioxide (CO2), 3, 57 Carbonate anion radical (CO
3), 435
437 Carboxymethyl cellulose (CMC), 337 Carotenoids extraction, 66 Catechins, 347 Cavitation bubble characteristics, 30
31 phenomenon, 23
24, 28t threshold, 31 CCPs. See Critical control points (CCPs) CDs. See Cyclodextrins (CDs) CDs method. See Conjugated dienes method (CDs method) Celerity, 28t Cell disruption, 46
48 membrane disruption, 144
145 modification, 70
71 structure, 175
176 shrinkage, 49 tissues, 403 PEF impact on, 405
406 walls, 405 disruption, 46
48, 48f Cellular matrices, 166
173 Cellular tissues, 5
6 Cellulose, 344
345 Cellulose acetate, 257 Cellulose
hemicellulose network, 405 Cereal products, applications to, 378 CFs. See Characterization factors (CFs) CFU. See Colony-forming unit (CFU) CGA. See Chlorogenic acid (CGA) Chain-breaking antioxidants, 379
380 Characterization factors (CFs), 486 Chemical engineering, 163
164 Chemical hazards, 487 Chemical lipid oxidation, 379 Chilton and Colburn correlation for turbulent flow, 255
256 Chitosan, 345
346 Chlorogenic acid (CGA), 337 Chokeberry extracts, 352 Christmas tree configuration, 262
263 Citronella (Cymbopogon winteriana), 73 Clean and green processing, 140 Clean label, 432
433 G

Subject Index

Clextral BC 45 twin-screw extruder, 310
311, 311f Climate change, 71 Clove buds (Eugenia caryophyllus), 75 CMC. See Carboxymethyl cellulose (CMC) Coacervation, 354 Coextrusion process, 352
353 Cold or mild thermal extraction in sugar beet processing, 413
417 Cold plasma, 431
432 inactivation of bacterial cells, 437
438, 437f for sustainable food production and processing antimicrobial action of plasma species, 437
438 energy efficiency and process cost, 445
446 in-package cold plasma, 438
440 plasma chemistry, 435
437 plasma sources, 434
435 for sustainable food production, 442
444 for water treatment, 440
441 technology, 432
433 Cold pressing. See Squeezing method Colony-forming unit (CFU), 425
426 Complex coacervation, 354 Compression phase, 23
26, 25f Concentration polarization, 254
256 Conjugated dienes method (CDs method), 381 Constant rate period, 472 Contaminants, 211 Continuous membrane separation device, 262
263, 263f Continuous-flow apparatuses, 36 Convective drying, MW with, 472 Conventional extraction, 221 methods of seed and nut oils, 317
319 mechanical expression, 317
318 solvent extraction, 318 supercritical fluid extraction, 318
319 Conventional homogenization processing, 139 Conventional oil extraction processes, 315
316 Conventional solvent extraction (CSE), 476

547

time to obtaining equivalent oil yields as, 228, 233
236 Conventional sugar beet technology, 413
414 Conventional thermal pasteurization, 87 Conventional thermal treatments, 90 Coriander (Coriandrum sativum), 297 Corn starch, 337 Cosolvent, 60 Coupled washing/diffusion phenomenological model (CWD phenomenological model), 221
222, 225
227 kinetic parameters defining from, 237
238 coupling DIC impacts with ultrasound technique, 238 flash depressurization effects, 237 intensification effect induced by ultrasound technique, 237
238 Coupling, 464
467 CPX3800H series US model, 231 Crank solutions, 226
227 Critical control points (CCPs), 508 Cross-flow filtration, 245, 246f Cross-flushing, 265
266 CSE. See Conventional solvent extraction (CSE) Cup-horn system, 36 Curcumin, 347 Curcumin-loaded proliposomes, 348 Cutting, 403 CWD phenomenological model. See Coupled washing/diffusion phenomenological model (CWD phenomenological model) Cyclodextrins (CDs), 337, 344, 355 Cysteine proteases, 97 D Daidzin, 205 Dairy products, EO applications in, 377 Darcy law, 252 DBD. See Dielectric barrier discharge (DBD) DBD-based plasma jet, 437
438 Dead-end filtration, 245, 246f Dealcoholization, 273

548

Decimal reduction time, 91
92 Decontamination of processing equipment, 432 Degradation of analytes, 209 DEHA. See Bis(2-ethylhexyl) adipate (DEHA) Dehydration, preserving of food quality by, 422
426 Demineralization, 272
273 Denaturation, 174 Dense membranes, 252 Depressurization, 116 Desolventation process, 242
243 Deterioration rate, 88 Dextrins, 337 Diafiltration, 263
264 Diagnostic US assessment, 229 Diavolume (DV), 263
264 DIC technology. See Instant controlled pressure drop technology (DIC technology) Dichlorvos, 441 Dielectric barrier discharge (DBD), 432
433 Dielectric heating, 456 principles, 458
461 pros and cons, 464, 464t Diffusion, 160
161 coefficients, 3
4 Dimensionless numbers, 255
256, 255t Direct enzymatic hydrolysis, 103 Disruption system, 143
144, 143f Distillation, 369, 371
372, 477 Donnan exclusion phenomenon, 247 Downstream extraction operations, 403
404 Downstream processing, 413
426 cold or mild thermal extraction in sugar beet processing, 413
417 with PEF, 414f preserving of food quality by dehydration, freezing, and stress/inactivation, 422
426 selective extraction of valuable compounds in juice and wine processing, 417
421 DPPH test, 385 Droplet aggregation, 147
148 Dry distillation, 369 Drying, 469
472

Subject Index

DV. See Diavolume (DV) Dynamic extractions, 204
205 Dynamic high-pressure, 140 principle and equipment, 141
144 processing as greener preservation processing, 149
152 as greener submicron emulsion processing, 146
149 Dynamic maceration, 221
222, 224
225, 231 Dynamic shear-enhanced membrane filtration, 266 E EC. See Epicatechin (EC) Eco-friendly applications, 140 Economical aspects, 122
124 of HP, 122 ED. See Electrodialysis (ED) ED with BM (BMED), 277 ED with UF membranes (EDUF), 269 Edible oils, 315 Edible polymers, 376 Edible vegetable oil, 309 EDUF. See ED with UF membranes (EDUF) EF. See Electric field (EF) Effective diffusivity (Deff), 224, 226
227, 237 Effluent treatment, 277
281 to allowing water recycling into processes, 278
280 brines, 279
280 condensation, 279 for by-product valorization, 280
281 before discharging, 277
278 EGCG. See Epigallocatechin gallate (EGCG) EHS. See Environmental, Health, and Safety performance factor (EHS) Elderberry (Sambucus nigra L.), 207 Electric field (EF), 159. See also Pulsed electric field (PEF) Electric frequency, 159 Electric pulse generators, 5 Electric-field assisting filtration, 266
267 Electrical conductivity, 167, 175
176 disintegration index, 406, 409f Electrical discharge plasmas, 441 Electrically driven membrane technology, 248
249

Subject Index

Electrodialysis (ED), 248
249 Electromagnetic heating technologies, 161 Electromagnetic spectrum, 457, 457f Electromagnetic wave (EMW), 456
458 Electronic impact processes, 435
437 Electropermeabilization, 167 Electropermeation effects, 175
176 Electroporation, 179, 404, 417
418 Electrospinning technique, 352 Electrotechnologies, 5
7 Emission spectrum of HIP UV lamp, 392 of PUVs, 391, 397
399 xenon flash lamps, 400 Emulsification process, 353
354 Emulsions, 45
46 formulation, 148
149 processing, 146
147 viscosity, 148
149 EMW. See Electromagnetic wave (EMW) Encapsulation, 335 in liposomes, 354 polyphenol-loaded microparticles production and application matrices for, 336
349 techniques for, 349
355 Endosulfan, 441 Energy consumption, 469 efficiency and process cost, 445
446 energy-consuming processes, 152 transference phenomena, 159 Environment-friendly character, 123 Environment-friendly technique, 2, 111 Environmental, Health, and Safety performance factor (EHS), 213
214 Environmental aspects, 122
124 of HP, 123
124 Environmental impact, 71
73 Enzymatic saccharification and fermentation, 466 Enzymes, 40, 118
120, 166
173 HP effect, 97
102, 99t high pressure
assisted enzymatic protein hydrolysis, 102 PL effects, 396
400 pretreatment, 112
113 EOs. See Essential oils (EOs) Epicatechin (EC), 347

549

Epigallocatechin gallate (EGCG), 336 EPTTM. See Extrusion Porosification Technology (EPTTM) Erosion, 49 Escherichia coli, 87
88 Essential oils (EOs), 369
371 as antimicrobials, 375
378 as antioxidant agents in food products, 378
386 chemical composition of, 371f distillation, 502 extraction, 65 devices, 373
374 by distillation and cold pressing, 372f future trends, 386
387 innovative techniques, 374 recovery methods, 371
373 Eukaryotic cells, 91 Evolum HT 53 model, 300
301 Expanded cereals, 294 Extraction, 59, 221, 301
311, 315
316. See also Solvent extraction (SE) applications of food ingredients, 475
481 of biocompounds, 175
182 electroheating, 176
178 nonthermal effects, 178
179 OH with extraction techniques, 179
182 of essential oils and fibers, 7
8 of food ingredients, application in, 64
68 green plants, 306
308 lignocellulosic residues, 302
305 oil extraction, 308
311 pressure, 196
197 principle, 475
476 stage, 64
65 sustainable processes, 175 ultrasound techniques for, 231 US applications in, 42, 43t Extruders, 289 Extrusion, 61, 69, 289
290 cooking process, 293 encapsulation, 295
296 expression, 297
301 extraction, 301
311 flours, 293
294 food ingredients, 296 mechanical fractionation, 296
297

550

Extrusion (Continued) methods, 352
353 proteins, 294
295 twin-screw extruder, 290
292 Extrusion Porosification Technology (EPTTM), 296 F FA. See Ferulic acid (FA) Faraday reactions, 159
160 FC method. See Folin
Ciocalteu method (FC method) FDA. See US Food and Drug Administration (FDA) Fed-batch membrane separation configuration, 262, 262f FeIII reduction, 386 Ferulic acid (FA), 303 Fiber-optic sensors, 462 Fick law, 226 Fillers, 289
290 First falling rate period, 506 First-order inactivation, 98 First-order kinetics, 118
119 models, 91
92, 98 Fixed-geometry interaction chamber, 143
144 Flash depressurization effects by expander and DIC pretreatments, 237 Flavonoids, 199 Flours, 293
294 Fluid, 58
59 bead coating technique, 351
352 Flux recovery, 267
268 Folin
Ciocalteu method (FC method), 199
204 Food applications in transformation and processing, 68
70 of US in preservation, 40
41, 41t biotechnology, 159 components, 335 degradation, 123
124 HP effect on nutritional characteristics, 102
108 PL effects on food functionality, 396
400 US in transformation and processing of, 37
40, 39t

Subject Index

Food industry, 3 by-products, 1 HACCP and HAZOP in, 488 high pressure application in, 122
124 Food ingredients extraction, 64
68 of anthocyanins, 68 of carotenoids, 66 of essential oil, 65 of spices, 67 PHWE applications in extraction, 199
207, 200t Food preservation applications in, 70
71 high-intensity light pulses for, 395
396 Food processing, 1, 57, 403 heat and mass transfer in, 461 with PEF, 406
426, 409f and preservation nonthermal effects, 166
173 thermal processing of foods, 164
166 transformation of macromolecules, 173
174 solar energy in food process engineering, 500, 501t Food production, 124 and processing, 431 Food products, 114
116 HP effect on shelf life of, 108
110 Food quality preservation, 468
469 and safety attributes, 91
110 using PHWE, 209
213 Foodborne pathogens, 92 Fouling, 256 Fractionation, 69
70 Fragmentation, 49 Free radicals, 46 Freeze-drying, 351, 423 Freezing, preserving of food quality by, 422
426 Frequency, 23, 24f, 28t, 167 Friable solids, 26
27 Fructooligosaccharides, 206
207 Fruits, 1 EO applications in, 377
378 and vegetable tissue enzymes, 4 Frying, 474

Subject Index

Fucoidan, 206
207 Functional food, 335
336 G GAME. See Gas-assisted mechanical expression (GAME) Gas chromatography conditions, 232 Gas composition, 32 Gas-assisted mechanical expression (GAME), 316, 319
329 actual oil extraction techniques, 319t advantages and limitations, 328
329, 329f applications, 321
328 fundamentals of technology, 319
320, 320f Gas-expanded liquid and solid phases, 63
64 Germination, 442 Glassware, 34 Global warming, 71 Gram-negative bacteria, 40 Gram-positive bacteria, 40 Graphene oxide laminar membranes, 261 Green alternatives, 12 “Green and innovative” techniques, 2 Green chemistry, 8 Green concepts, 1 Green extraction chemistry, 193, 194f Green food processing electrotechnologies, 5
7 experiential methodology, theory, and statistical calculations, 11
12 HHP, 2
3 laser ablation and radiofrequency, 7 microwaves, 8
9 nanotechnology, 9
10 SCCD, 3
5 solar energy, 10
11 strategy, challenges, and perspectives, 12
13 techniques, 57 ultrasound, 7
8 Green plants, 306 alfalfa extrusion, 306
308 Green processing methods, 403 Green solvents, 7 Green tea catechins, 347 Green tea extracts (GTEs), 336

551

Greener extraction processes, 175 Greener extraction processing, 144
146 Greener preservation processing, 149
152 Greener submicron emulsion processing, 146
149 Greener technologies, 13 Greenness, 213 GREENVOLTEX project, 13 Growth phase of cells, 91 GTEs. See Green tea extracts (GTEs) H Hard solids, 26
27 Hazard analysis and critical control points (HACCP), 486
488, 508
509 application, 487 in food industry, 488 principles, 487 Hazard and operability analysis (HAZOP), 486
487 considerations, 508
509 in food industry, 488 HCAs. See Hydroxycinnamic acids (HCAs) HD method. See Hydro-distillation method (HD method) Heat and mass transferring processes, 7 Heat deposition, 161 Heat transfer in food processing, 461 model, 117 modes, 469
471 phenomena, 117 Heating or cooling stage, 64
65 Herbs and spices, 67 Heterochlorella luteoviridis, 178 Heterogeneous cavitation, 26, 27f Heterogeneous liquid
liquid reactions, 26 systems, 45
46 Heterogeneous solid
liquid cavitation, 26
27 Hexane, 177, 221 High hydrostatic pressure processing (HHP processing), 2
3, 71, 149. See also Supercritical fluid processing and extraction economical and environmental aspects, 122
124 fundamental principles of HP process, 88
91

552

High hydrostatic pressure processing (HHP processing) (Continued) effect of HP on food quality and safety attributes, 91
110 HP process design and evaluation, 114
122 HP technology in combination with processes and hurdles, 110
113 industrial applications of HP, 113
114 High partial pressure, 32 High-frequency power source, 434
435 High-intensity light pulses for food preservation, 395
396 High-intensity pulse (HIP), 392 factors affecting interaction between HIP and materials, 394 UV lamp, 392 advantages and disadvantages, 393
394 High-performance liquid chromatography coupled to mass spectrometry detection (HPLC
MS), 199
204 High-pressure (HP), 87, 104t application in food industry, 122
124 carbon dioxide. See Supercritical carbon dioxide (SCCD) effect on food quality and safety attributes, 91
110 effect on enzymes, 97
102 effect on nutritional characteristics of foods, 102
108 effect on shelf life of food products, 108
110 on microorganisms, 91
97 fundamental principles of HP process, 88
91 high pressure
assisted enzymatic protein hydrolysis, 102 high pressure
assisted extraction, 110
112 intensifiers, 139
140 process design and evaluation, 114
122 HP processing impact evaluation, 118
119 pressure
temperature
time indicators, 119
122 technology in combination with processes and hurdles, 110
113 application in combination with enzyme pretreatment, 112
113

Subject Index

application in combination with osmotic dehydration, 112 in combination with antimicrobials and plant extracts, 112 high pressure
assisted extraction, 110
112 High-pressure homogenization (HPH), 139
140 dynamic high-pressure principle and equipment, 141
144 greener preservation processing, 149
152 greener submicron emulsion processing, 146
149 processing as greener extraction processing, 144
146 High-pressure processing. See High hydrostatic pressure processing (HHP processing) High-pressure
high-temperature (HPHT), 87 High-temperature/short-time treatment (HTST treatment), 223 High-temperature
high-pressure (HTHP), 92, 93t, 94t High-temperature
low-pressure region, 98
100 High-voltage atmospheric pressure cold plasma, 445 High-voltage electrical discharges (HVED), 2, 5, 6f HIP. See High-intensity pulse (HIP) Hiperbaric, 113
114 HMF. See 5-Hydroxymethylfurfural (HMF) Homogenization, 142 homogeneous cavitation, 26 processing, 139, 140f Homogenizer, 139 Homopolar electrodialysis, 248
249, 249f Hormonal patterns, 442 Horn-based system, 36 Hot humid air, 472 Hot spot theory, 46 HP. See High-pressure (HP) HPH. See High-pressure homogenization (HPH) HPHT. See High-pressure
high-temperature (HPHT) HPLC
MS. See High-performance liquid chromatography coupled to mass spectrometry detection (HPLC
MS)

Subject Index

553

HTHP. See High-temperature
high-pressure (HTHP) HTST treatment. See High-temperature/ short-time treatment (HTST treatment) HVED. See High-voltage electrical discharges (HVED) Hydro-distillation method (HD method), 371 Hydrodiffusion, 477 Hydrodistillation, 177 Hydrogen peroxide (H2O2), 435
437 Hydrolysis reactions during PHWE, 208
209 Hydronium ions (H3O1), 208 Hydroperoxyl (HO 2), 435
437 Hydroxycinnamic acids (HCAs), 303 Hydroxyl radical (HO  ), 385, 435
437 Hydroxyl radical-scavenging activity, 385 5-Hydroxymethylfurfural (HMF), 208, 210 G

I In-package cold plasma, 438
440, 439f Incident and reflected power, 462 Indian meal moth (Plodia interpunctella), 440 Industrial applications of HP, 113
114, 115t Industrial process, 11 Industrial scale, ultrasound techniques at, 36
37, 37f Ingredients, 64 Innovative techniques, 374 Instant controlled pressure drop technology (DIC technology), 222, 228
229, 229f flash depressurization effects by, 237 Intensification effect induced by ultrasound technique, 237
238 ways of solvent extraction process, 221
224 Interaction wave/matter, 458
461 Ionized gas, 434
435 Isotropic membranes, 257 J Jerusalem artichoke tuber (JAT), 181
182 Joule heating, 159 Joule’s law, 159

Juice extraction line, 418, 419f processing, 166 selective extraction of valuable compounds in, 417
421 K Kafirin, 347
348 Kinetic equation, 98 L Laboratory scale, ultrasound techniques at, 34
36 Lactic acid bacteria (LAB), 100 Lactobacillus acidophilus, 167 Laminaria japonica, 206
207 Laser ablation, 2, 7 LC analysis. See Liquid chromatography analysis (LC analysis) LCA. See Life cycle assessment (LCA) LCI. See Life cycle inventory (LCI) Lemongrass (Cymbopogon citrus), 73 Leptocarpha rivularis, 65 Levoglucosan, 208 Life cycle assessment (LCA), 72, 152, 213
214, 482 fundamental aspects, 484t impact assessment, 483
486 Life cycle inventory (LCI), 482
483, 485t Light technologies, 391 Lignin, 208
209 Lignocellulosic residues, 302 bran, 303
304 straw, 302
303 wood, 304
305 Linear amylose, 337 Lipid autoxidation, 380 inhibition, 381
384 β-carotene bleaching test, 384 CDs method, 381 TBARS method, 381
384 Lipid-based carrier for phenolic compounds, 348
349 Lipids, 336, 349 Lipophilic compounds, 70 Lipopolysaccharides, 438 Liposomes, 354 Liquid chromatography analysis (LC analysis), 232

554

Liquid/solid extraction process (LSE process), 324
325 Liquids, 23 fractionation, 62 liquid
liquid extraction, 61 Listeria monocytogenes, 87
88, 376, 439
440 Low-pressure mercury (LPM), 391 Low-sodium products, 106
108 LPM. See Low-pressure mercury (LPM) LSE process. See Liquid/solid extraction process (LSE process) M Macromolecule transformation, 173
174 Macromolecules, transformation of, 173
174 MAE principles. See Microwave-assisted extraction principles (MAE principles) Magnetic wave (MW), 458 Malathion, 441 Malondialdehyde (MDA), 381
384 Maltodextrins (MDs), 337, 344 Mango leaves (Mangifera indica), 76 Manosonication, 40 Manothermosoncation, 40 Marigold (Calendula officinalis), 76
77 MASE. See MW-assisted solvent extraction (MASE) Mass transfer in food processing, 461 Matrices for polyphenol-loaded microparticles production and application, 336
349 Maubois, Mocquot, Vassal process (MMV process), 269
270 Maxwell
Stefan diffusive transport equation, 254 MBR. See Membrane bioreactor (MBR) MD. See Membrane distillation (MD) MDA. See Malondialdehyde (MDA) MDs. See Maltodextrins (MDs) ME. See Mechanical expression (ME) Meat processing, 166 Meat-based foodstuffs and seafood products, EO applications in, 375
376 Mechanical compaction of sliced food materials, 408 Mechanical disintegration index, 410

Subject Index

Mechanical expression (ME), 315
316 Mechanical forces, 46 Mechanical fractionation, 296
297 Medicinal and aromatic plants, 1 Medium physical parameters, 31
32 Medium Pressure DIC unit (MP-DIC unit), 228
229 Medium-pressure mercury (MPM), 391 MEF. See Moderate electric fields (MEF) Membrane cleaning, 267
268 electroporation, 406 fouling, 256
257, 256f membrane-manufacturing processes, 257 selectivity, 251 Membrane bioreactor (MBR), 265 Membrane distillation (MD), 250 crystallization, 275 Membrane separation, 245 classification by driving force and membrane type, 246t configurations, 261
264 batch configuration, 261
262 continuous mode, 262
263, 263f diafiltration, 263
264 electrically driven membrane technology, 248
249 in food processing, 245
250 concentration/extraction, 273
275 contribution and interest of membranes, 268
270 effluent treatment, 277
281 purification, 270
273 separation and integrated processes, 275
277 innovations in material manufacturing, 260
261 materials, 257 membrane cleaning, 267
268 module geometries, 258
259, 259t pressure-driven membrane technologies, 245
248 separation process performances enhancement techniques, 264
267 theoretical aspects in, 250
257 parameters, 250
251 transport theory, 252
254 vapor pressure gradient membranes, 250 3ʹ-Methoxypuerarin, 205

Subject Index

MF. See Microfiltration (MF) MFA. See Multiflash autovaporization (MFA) MHG. See MW hydrodiffusion and gravity (MHG) Micro-encapsulation, 10, 335
336 Microbial cells, 145 Microbial hazards, 487 Microbial inactivation mechanism, 394
396 photochemical effect, 394 photophysical effect, 395 photothermal effect, 395 Microbial stabilization, 272 Microfiltration (MF), 245 Micronization, 68
69 Microorganisms, 40, 119
120, 166
173, 431
432 HP effect, 91
97 decimal reduction times, 95t parameters of multiparameter equation, 96t Microparticles, 335 Microwave-assisted extraction principles (MAE principles), 476
477 advantages, 480
481 influencing factors, 477 Microwaves (MWs), 8
9, 161, 455 applications in extraction of food ingredients, 475
481 in transformation, food processing, and preservation, 467
475 associated metrology, 462
463 with convective drying, 472 coupling, 464
467 environmental impact, 481
486 goal and scope, 483
486 results interpretation, 486 extraction, 9, 374f frying, 474
475 future trends, 489
490 heat and mass transfer in food processing, 461 industrial microwave applications, 490t microwave-assisted extraction techniques, 477
481 advantages, 480
481 MW-assisted food processing technologies, 466

555

oven safety, 488 as posttreatment, 466 pre-and postprocessing, 464
467 principle of dielectric heating, 458
461 influencing factors, induced mechanisms, 456
464 regulation and security, 486
488 techniques at laboratory and industrial scale, 464 theoretical aspects, 456
458 treatment, 222
223 upscaling and applications in industry, 489 vacuum drying, 473 Mineral content, 103
106 membranes, 257 MIS extraction. See MW-integrated Soxhlet extraction (MIS extraction) MMV process. See Maubois, Mocquot, Vassal process (MMV process) Moderate electric fields (MEF), 159
160 Modifier, 59 Moisture content measurement, 231 Molecular inclusion, 355 Molecular weight cutoff (MWCO), 245
246 Momordica foetida, 204
205 Morus nigra L. (MN), 480 MP-DIC unit. See Medium Pressure DIC unit (MP-DIC unit) mpHP. See Multipulses HP (mpHP) MPM. See Medium-pressure mercury (MPM) Multiflash autovaporization (MFA), 242 Multipulses HP (mpHP), 94
97 Multistage membrane separation process, 267, 267f MW. See Magnetic wave (MW) MW hydrodiffusion and gravity (MHG), 477
480 dehydration extraction technique, 481 MW-assisted air drying (MWAD), 467 MW-assisted freeze-drying (MWFD), 467 MW-assisted solvent extraction (MASE), 477 MW-assisted vacuum drying (MWVD), 467 MW-integrated Soxhlet extraction (MIS extraction), 481

556

MWAD. See MW-assisted air drying (MWAD) MWCO. See Molecular weight cutoff (MWCO) MWFD. See MW-assisted freeze-drying (MWFD) MWs. See Microwaves (MWs) MWVD. See MW-assisted vacuum drying (MWVD) N n-hexane extraction technique, 233 n-hexane Randall method, 224 Nannochloropsis gaditana, 145 Nanoencapsulation, 10 Nanofiltration (NF), 247 Nanoparticles, 335 Nanosized droplets, 149 Nanotechnology, 2, 9
10 Natural food products, 57 Natural products, 42 PHWE applications in, 199
207, 200t Near UV/visible (NUV
vis), 396 Negligible external resistance condition (NER condition), 221
222, 225
226 NF. See Nanofiltration (NF) Niche applications, 432 Nonconventional energy sources, 2 Nonequilibrium plasma, 433 Nonglandular trichomes, 49 Nonthermal effects, 166
173, 488 in extraction processes, 178
179 food processing, 12 mechanical technology, 141 processing, 87 technology, 140 Nucleation-growth kinetics, 63
64 Nutrients, 1
2 Nutritional characteristics of foods, HP effect on, 102
108 allergenicity, 106 bioactive peptides, 103 low-sodium products, 106
108 minerals content, 103
106 polyphenols and antioxidant capacity of foods, 102
103 NUV
vis. See Near UV/visible (NUV
vis)

Subject Index

O OE. See Osmotic evaporation (OE) Ohmic heating (OH), 159, 160f, 180t commercial and novel applications, 162
164 extraction of biocompounds, 175
182 food processing and preservation, 164
174 fundamentals, 159
162 nonthermal effects, 168t Ohmic-assisted hydrodistillation, 177 Oil extraction solvent extraction, 310
311 water extraction, 308
310 Oil palm fruits, 181 Oil recovery, GAME for, 324
325 Oil yields issues from SE operations, 232
233 time to obtaining equivalent oil yields as CSE, 233
236 Oil-in-water (O/W) emulsions, 147, 348 phases, 39
40 Oilseeds, gas-assisted oil expression from conventional extraction methods of seed and nut oils, 317
319 GAME, 319
329 Oleaginous materials, 227
228 Oleic sunflower oil, 298
299 Olive mill wastewaters (OMWs), 276
277 Organic acids, 212
213, 277 polymeric membranes, 257 solvents, 66, 73 synthesis, 164 Organoleptic deterioration, 164
165 Osmotic dehydration, 112, 172
173 Osmotic distillation. See Osmotic evaporation (OE) Osmotic evaporation (OE), 250 Osmotic pressure, 253 Ozone (O3), 435
437 P p-coumaric acid (p-CA), 303 Para-coumaric acid, 74 Particle formation, 60
61 plants, 74 Pasteurization, 100
101, 163, 467
469

Subject Index

PATS. See Pressure-assisted thermal sterilization (PATS) Pectin, 346 Pectin methylesterases (PMEs), 97
98, 101f, 151 PEF. See Pulsed electric field (PEF) Penetration depth, 460
461 Period, 28t Permeability, 251 Permeate flux, 250
251, 253 Peroxidases, 97 Peroxyl (ROOd), 435
437 Peroxyl radicals (ROO  ), 379 Pervaporation, 250 Petroselinic acid, 299
300 pH, 71 Phenolic compounds, 176
177, 199
204 lipid-based carrier for, 348
349 polysaccharide-based carrier for, 337
346 protein-based carrier for, 346
348 Phenomenological analysis of solvent extraction process, 221
224 Phosphoric acid, 310 Photobacterium phosphoreum, 376 Photovoltaic energy, 499 PHWE. See Pressurized hot water extraction (PHWE) Physiochemical process, 5
6 Piezoelectric transducers, 34 PL. See Pulsed light (PL) Plant extracts, 112 growth enhancement, 432 plant-based beverages, 151 plant-based food proteins, 102 plant-based ingredients, 221 plant-derived compounds, 68 solid
liquid extraction, 46
48 Plasma chemistry, 435
437 ground state species and atomic oxygen species, 436t jet, 434
435 sources, 434
435, 434f species, 437
438 PMEs. See Pectin methylesterases (PMEs) POH. See Pulsed ohmic heating (POH) Polar cosolvent, 59 Polarization, 457
458

557

Poly(ethylene glycol) methacrylate, 260 Polyphenol oxidase (PPO), 97, 397 Polyphenol-loaded microparticles production and application matrices for, 336
349 lipid-based carrier for phenolic compounds, 348
349 polysaccharide-based carrier for phenolic compounds, 337
346 protein-based carrier for phenolic compounds, 346
348 techniques for, 349
355 complex coacervation, 354 emulsification process, 353
354 encapsulation in liposomes, 354 extrusion methods, 352
353 fluid bead coating technique, 351
352 freeze-drying process, 351 molecular inclusion, 355 spray-drying microencapsulation process, 349
351 Polyphenols, 102
103, 347
348, 355 Polysaccharide films, 174 Polysaccharide-based carrier for phenolic compounds, 337
346 microencapsulation of phenolics, 338t Polysaccharides, 206
207 Pomegranate juice, 276 Pore-flow model, 252
253 Porous membranes, 252 Porous solids, 26
27 Posttreatment, 466 after microwaves, 466 Power US, 39
40, 230 PPO. See Polyphenol oxidase (PPO) Preleaching time, 465 Prepressing, 317 Preservation, 62 Pressing, 317
318 Pressure, 4, 71, 90
91 resistance constant, 91
92 Pressure-assisted thermal sterilization (PATS), 87
88 Pressure-driven membrane technologies, 245
248 Pressure-enhanced sterilization, 87 Pressure
temperature
time indicators (PTTIs), 114
116, 119
122, 121t Pressurization, 64
65, 116, 142

558

Pressurized fluid-based processes, 68 Pressurized gas-expanded liquid, 74 Pressurized hot water extraction (PHWE), 193
197, 198f. See also Solvent extraction (SE) applications in food ingredients extraction, 199
207, 200t environmental impact, 213
214 food quality and safety using, 209
213 hydrolysis reactions during, 208
209 instrumentation, 197
198 principles of green chemistry, 194f Pretreatment, 464
466 by means of microwaves, 464
465 before microwaves, 465
466 Probiotic bacterium Bifidobacterium lactis BB12, 92
94 Process intensification, 222 Process validation, 90
91 Prokaryotic cells, 91 Proteins, 294
295, 336 aggregation, 174 protein-based carrier for phenolic compounds, 346
348 protein
lipid films, 174 texturization, 294 PTTIs. See Pressure
temperature
time indicators (PTTIs) Pueraria lobata, 205 Puerarin, 205 Pulsed electric field (PEF), 5, 179, 404 food processing with, 406
426, 409f downstream processing, 413
426 upstream processing, 410
413 impact on cell tissue and biosuspensions, 405
406 Pulsed light (PL), 391 effects on quality, enzymes, and functionality, 396
400 factors affecting interaction between HIP and materials, 394 high-intensity light pulses for food preservation, 395
396 microbial inactivation mechanism, 394
395 mode of action, 391
392 performance comparison of light-based technologies, 392t sources and equipment, 400

Subject Index

Pulsed ohmic heating (POH), 181 Pulsed UV light (PUV light), 391 mode of action, 391
392 Purification, 270
273 biochemical/chemical stabilization, 270
272 composition correction, 273 dealcoholization, 273 demineralization, 272
273 pH adjustment, 273 microbial stabilization, 272 PUV light. See Pulsed UV light (PUV light) Pyrex, 32 Pyrolysis, 369 Pyruvaldehyde, 208 Q Quality assurance in microwave food processing, 488 PL effects on quality of food, 396
400 Quartz, 32 Quercetin liposomes, 348 R Radical-scavenging tests, 384
386 ABTS test, 384
385 DPPH test, 385 FeIII reduction, 386 hydroxyl radical-scavenging activity, 385 scavenging of superoxide radical anion, 386 Radio frequency (RF), 2, 7, 432
433, 456
457 drying process, 7 heating, 161 Randall extraction, 231 Rapeseed oil, 241 Rapeseed pressing cake, 225 Rarefaction phase, 23
26, 25f Reactive nitrogen species (RNS), 435
437 Reactive oxygen species (ROS), 435
437 Recycling emulsion, 148 Redox-colored dyes, 441 Relative permittivity, 458 Renewable energy, 73 Residue, 475 Resin purification (RP), 211 Resource-efficient process, 438
440

Subject Index

Resveratrol, 355 Retinyl-acetate, 149 Reverse osmosis (RO), 245, 247
248, 248f RF. See Radio frequency (RF) Riboflavin, 397
399 RNS. See Reactive nitrogen species (RNS) RO. See Reverse osmosis (RO) ROS. See Reactive oxygen species (ROS) Rosemary leaf, 49 Rosemary-of-field leaves (Baccharis dracunculifolia), 76 RP. See Resin purification (RP) S Saccharomyces cerevisiae, 167
172 Salmonella, 87
88 SAME technologies. See Solute-assisted ME technologies (SAME technologies) Saponins, 206 SAS. See Supercritical antisolvent (SAS) Satureja horvatii EOs, 376 Scalding, 403 Scavenging of superoxide radical anion, 386 SCCD. See Supercritical carbon dioxide (SCCD) scCO2. See Supercritical carbon dioxide (SCCD) Scenedesmus almeriensis, 66 SE. See Solvent extraction (SE) Second falling rate period, 506 Semiconductor manufacturing, 489 Separation between solvent and extraction, 64
65 SFE. See Supercritical fluid extraction (SFE) Shear forces, 46 Shelf life of food products, HP effect on, 108
110, 109t Shock waves, 46 Sieving instrument, 231 Silymarin, 209
210 Single intensifier system, 141 Singlet oxygen (1O2), 435
437 SME. See Specific mechanical energy (SME) Snacks, 294 Soft solids, 26
27 Soil decontamination, 432 Solar cookers, 502, 505t

559

cooking, 502
505 distillation, 10f drying systems, 506
507, 506f, 507f energy, 10
11 drying systems, 507 environmental impacts using, 508 in food process engineering, 500, 501t HACCP, 508
509 hazard and operability considerations, 508
509 instrumentation, 499 extraction, 500
502, 503t pasteurization, 507 technologies, 508 Solar collectors, 502
505, 505t Solid liquid mixtures, 162
163 Solid surface-liquid systems, 26 Solid
liquid boundary, 46 expression, 317
318 extraction, 46, 175, 475 UAE, 46
48 Solubilization, 10 Solute, 60 Solute flux (Js), 253 Solute-assisted ME technologies (SAME technologies), 323
324 Solution-diffusion model, 253
254 Solvent, 60 recycling stage, 64
65 Solvent extraction (SE), 221
222, 310
311, 315
316, 318. See also Pressurized hot water extraction (PHWE) assessments and characterization dynamic maceration, 231 gas chromatography conditions, 232 liquid chromatography analysis, 232 moisture content measurement, 231 Randall extraction, 231 sieving instrument, 231 intensification ways, 221
224 DIC technology, 228
229, 229f ultrasound techniques for extraction, 231 ultrasound-assisted SE, 229
230 kinetics of vegetal oil extraction, 233
238 oil yields issues from differently assisted operations of SE, 232
233

560

Solvent extraction (SE) (Continued) phenomenological analysis, 221
228 CWD phenomenological kinetic model, 225
227 intensification methodology and experimental protocol, 227
228, 228f raw material rapeseed pressing cake, 225 soybean, 224
225 sunflower, 224 Solvent residence time (tRES), 75 Sonocapillary effect, 49 Sonochemical effects, 42
45 Sonoporation, 46, 49 Sonotrode, 35
36 Soy protein isolate (SPI), 347 Soybean, 224
225 Specific mechanical energy (SME), 291 Specific thermal energy (STE), 291 SPI. See Soy protein isolate (SPI) Spices extraction, 67 Spiral-wound membrane, 258, 260f Spoilage microorganisms, 92 Spray-drying microencapsulation process, 349
351 Squeezing method, 369, 372
373 Stable colloidal dispersion, 146
147 Staphylococcus aureus, 395 Starch, 337
344 gelatinization, 293 “Starting accessibility” stage, 221
222, 224, 226
227 STE. See Specific thermal energy (STE) Steam distillation, 372 Sterilization, 163, 165
166, 467
469 Straw, 302
303 Structural pretreatment, 227 Subcritical water extraction. See Pressurized hot water extraction (PHWE) Submicron particles, 335 Sucrose, 206 Sugar beet juice, 416
417 Sugar beet processing, cold or mild thermal extraction in, 413
417 Sunflower (Helianthus annuus L.), 76
77, 224, 297 oil extraction, 241 Supercritical antisolvent (SAS), 69

Subject Index

Supercritical carbon dioxide (SCCD), 2
5, 3f, 57, 58f, 316, 319 role in particle formation techniques, 63f Supercritical drying, 4
5 Supercritical fluid extraction (SFE), 59, 316, 318
319 Supercritical fluid processing and extraction. See also High hydrostatic pressure processing (HHP processing) applications in extraction of food ingredients, 64
68 in food preservation, 70
71 in transformation and processing of food, 68
70 environmental impact, 71
73 extraction, 59 extrusion, 61 factors, 62
64 fractionation, 61
62 particle formation, 60
61 preservation, 62 principle, 58
59 upscaling and application in industry, 73
77 Supercritical fluids, 57 supercritical fluid-based processes, 71 Supercritical organic solvent drying, 4
5 Supercritical technology, 62 Superheated water extraction. See Pressurized hot water extraction (PHWE) Superoxide anion (O 2_), 435
437 Superoxide radical anion, scavenging of, 386 Surimi process, 112
113, 469 Sustainable/sustainability development, 144
145 of extraction process, 213 food production, 442
444, 442f, 443t industrial solvents, 13 processing technologies, 193 G

T TBA. See Thiobarbituric acid (TBA) TBARS method. See Thiobarbituric acid reactive species method (TBARS method) Technology readiness levels (TRL), 87 Temperature, 32, 71, 90
91 measurement, 462
463

Subject Index

Tempering, 473
474 Texturization, 294 TGase. See Transglutaminase (TGase) Thawing, 473
474 Thermal effects, 175
176, 488 of OH, 176 Thermal inactivation, 46 Thermal microagitation, 222 Thermal plasmas, 433 Thermal processes, 70 of foods, 164
166 techniques, 161 Thermal resistance constant, 91
92 Thermal solar energy, 499 Thermal technique, 9 Thermal treatments, 431 Thermodynamic nonequilibrium, 433 Thermoplastics, 289
290 Thermosonication, 40 Thiobarbituric acid (TBA), 381
384 Thiobarbituric acid reactive species method (TBARS method), 381
384 Time, 71 savings, 468 Time
temperature integrators (TTIs), 119 TMP. See Transmembrane pressure (TMP) Tomato pealing, 166 Total phenolic compounds (TPCs), 321
323 Toxic residues, 439
440 TPCs. See Total phenolic compounds (TPCs) Transglutaminase (TGase), 112
113 Transient bubbles, 24
26 Transmembrane pressure (TMP), 245, 250, 265 Transmission rate (Tr), 251 Transport theory, 252
254 concentration polarization, 254
256 membrane fouling, 256
257 pore-flow model, 252
253 solution-diffusion model, 253
254 TRL. See Technology readiness levels (TRL) TSE. See Twin-screw extruder (TSE) TSMAE. See Two-step MAE (TSMAE) TTIs. See Time
temperature integrators (TTIs) Tubular membranes, 258 Turbo-distillation, 374f

561

Twin-screw extruder (TSE), 289
291, 310 process control parameters, 291
292 screw elements, 291, 292t Twin-screw extrusion technology, 297 Two-step MAE (TSMAE), 480
481 U UAE. See Ultrasound-assisted extraction (UAE) UF. See Ultrafiltration (UF) UHPH. See Ultrahigh-pressure homogenization/homogenizers (UHPH) UI. See Ultrasonic intensity (UI) Ultra-HPLC
qTOF
MS analysis of PHWE, 204
205 Ultrafiltration (UF), 245
246 Ultrahigh-pressure homogenization/ homogenizers (UHPH), 139
140, 143
144 Ultrasonic cutting, 37
39 drying, 39
40 frequency, 29 power, 23, 27
28, 28t shape and size of ultrasonic reactors, 32
33 transducer, 29
30 vibrational energy, 37
39 wave, 27
28 propagation velocity, 29
30 Ultrasonic intensity (UI), 23, 28t Ultrasound (US), 7
8, 23, 179, 221
222, 266 applications, 37
42, 38f in transformation and processing of food, 37
40 of US in extraction, 42 of US in preservation of food, 40
41 comprehension of ultrasound-induced mechanisms, 42
50 factors, 27
33 acoustic wave intrinsic parameters, 27
30 cavitation bubble characteristics, 30
31 medium physical parameters, 31
32 shape and size of ultrasonic reactors, 32
33 principle, 23
27, 29t

562

Ultrasound (US) (Continued) techniques, 34
37 coupling DIC impacts with, 238 for extraction, 231 at industrial scale, 36
37 intensification effect induced by, 237
238 at laboratory scale, 34
36 transducers, 34 ultrasound-assisted SE, 229
230 US-assisted degassing, 39
40 US-assisted surface cleaning, 37
39 Ultrasound-assisted extraction (UAE), 8, 42 Ultraviolet (UV), 391 Uniform TMP system (UTP), 265 United States Department of Agriculture, 431 Upscaling and application in industry, 73
77 Upstream processing, 410
413 US. See Ultrasound (US) US Food and Drug Administration (FDA), 399 UTP. See Uniform TMP system (UTP) UV. See Ultraviolet (UV) V Vacuum drying, MW, 473 van’t Hoff equation, 247
248 Vapor pressure gradient membranes, 250 Vegetables, 1 EO applications in, 377
378 oil, 298 Vegetal oil extraction, kinetics of, 233
238 DIC treatment and ultrasound treatment impacst on, 235t impact on oil quality, 238
241 kinetic parameters defining from CWD phenomenological model, 237
238

Subject Index

specific new desolventation ways, 242
243 time to obtaining equivalent oil yields as CSE, 233
236 Vegetative pathogenic bacteria, 87
88 Velocity of extraction, 11 Vetiver roots (Chrysopogon zizanioides), 75 Vitamin A, 88 Vitamin B2. See Riboflavin Vitamin C, 88, 397
399 Vitamin E, 315 Volume reduction ratio (VRR), 263 Volumetric heating, 471 W Wash water, 440
441 Washing accessibility stage, 221
222 Water extraction, 308
310 insoluble proteins, 347 treatment, 432 cold plasma for, 440
441 vapors, 441 water-soluble polysaccharides, 177 Water extraction and particle formation online (WEPO), 207 Water-in-oil-in-water double emulsion (W/O/W double emulsion), 348 Wavelength, 23, 28t Wine processing, selective extraction of valuable compounds in, 417
421 Wood, 304
305 World Health Organization, 431 X X-ray diffraction, 174 Xenon flash lamps, 400 Xylanase, 120