Microstructure of dairy products 9781118964194, 1118964195, 9781118964200, 1118964209, 9781118964217, 1118964217, 9781118964224

Table of contents :
Content: List of Contributors xiiiPreface xv1 Microscopy Techniques for Dairy Products - An Introduction 1Mark A.E. Auty1.1 Introduction 11.1.1 Brief History and Background 11.2 Conventional Optical Microscopy Techniques 41.2.1 Conventional Light Microscopy - Optical Contrast 41.2.1.1 Bright Field 41.2.1.2 Polarized Light 41.2.1.3 Phase Contrast 41.2.1.4 Differential Interference Contrast 51.2.1.5 Fluorescence 51.2.2 Chemical Contrast Techniques in Light Microscopy 51.3 Confocal Scanning Laser Microscopy 61.3.1 Confocal Principle 61.3.2 Identifying Dairy Primary Components in CSLM: Labeling Strategies 81.3.2.1 Generic Labeling 81.3.2.2 Specific Labeling 101.3.2.3 Covalent Labeling 111.3.3 Some Applications of Confocal Microscopy to Dairy Products and Ingredients 121.3.3.1 Spreads 121.3.3.2 Emulsions and Foams 121.3.3.3 Fermented Milks 121.3.3.4 Cheese 131.3.3.5 Dairy Powders 131.3.3.6 Milk Protein Gel Systems 141.3.3.7 Dynamic CSLM Techniques 141.4 Electron Microscopy (EM) Techniques 161.4.1 Transmission Electron Microscopy 161.4.2 Scanning Electron Microscopy 181.4.3 Other EM Techniques 181.4.3.1 X?ray Microanalysis 181.4.3.2 Cryo?electron Microscopy 191.4.3.3 Environmental and Variable Pressure SEM 201.5 Emerging Microscopy Techniques 201.5.1 Atomic Force Microscopy 201.5.2 Advanced Fluorescence Microscopy Techniques 221.5.3 Confocal Raman Microscopy 221.5.4 X?ray Nano/Microtomography 221.5.5 Super?Resolution Microscopy 231.6 Image Analysis 231.7 Conclusions 24References 242 Light Microscopy and CSLM Techniques, Principles and Applications 33Johan Hazekamp2.1 Introduction 332.1.1 The History of Microscopy 332.1.2 Evolution of Confocal Microscopy 342.1.3 Food Microscopy 352.1.4 Wide Field Microscopy 362.1.5 Confocal Scanning Laser Microscopy (CSLM) 382.2 Sample Preparation and Specific Staining and Labeling 412.2.1 Specific Labeling 442.2.2 Dynamic Imaging 462.2.3 Future Perspectives 46References 473 Electron Microscopy Techniques 51Semih Otles and Vasfiye Hazal Ozyurt3.1 Introduction 513.2 Types of EM 513.2.1 Scanning Electron Microscopy (SEM) 513.2.2 Transmission Electron Microscopy (TEM) 523.2.3 Cryo?SEM 523.2.4 Cryo?TEM 533.2.5 Environmental Scanning Electron Microscopy (ESEM) 533.3 Sample Preparation for EMs 533.3.1 Scanning Electron Microscopy 533.3.2 Transmission Electron Microscopy 533.3.3 Cryo?Scanning Electron Microscopy 533.4 Dairy Microstructure 543.5 Electron Microscopy for the Dairy Product 543.6 Summary 60References 644 Emerging Techniques for Microstructural Analysis 67I. Hernando, E. Llorca, and A. Quiles4.1 Introduction 674.2 Scanning Probe Microscopy 674.2.1 Scanning Tunneling Microscope (STM) 694.2.2 Atomic Force Microscope (AFM) 704.2.3 Applications of the Main Probe Microscopes 714.3 X?Ray Tomography 724.4 Small?Angle?Scattering (SAS) Methods: SAXS and SANS 744.4.1 Small?Angle X?Ray Scattering (SAXS) 744.4.2 Small?Angle Neutron Scattering (SANS) 754.4.3 Applications of Small?Angle?Scattering Methods 754.5 Vibrational Spectroscopies (Fourier Transform Infrared?FTIR and Raman Microscopy) 754.5.1 Fourier Transform Infrared (FTIR) Spectroscopy 764.5.2 Raman Spectroscopy 784.6 Magnetic Resonance: NMR and MRI 804.7 Conclusions 82References 825 Quantitative Image Analysis in Microscopy 89Gaetano Impoco5.1 Aim and Scope 895.2 Image Analysis Software 905.3 Applications to Microscopy for Dairy Science 975.3.1 Porosity 985.3.2 Fat Globules 995.3.3 Microbial Cells 1005.4 Image Analysis and Quantitative Measurement 1005.4.1 Image Analysis Basics 1015.4.1.1 Feature Detection 1025.4.1.2 Quantitative Analysis 1035.4.2 Common Pitfalls 1055.4.3 Misuse and Wrong Interpretation of Image Analysis Results 1145.4.4 Good Practices 1165.4.5 Image Analysis in your Lab 1195.5 Conclusions 122Acknowledgments 123References 1236 Microstructure of Milk 127Michael H. Tunick6.1 Components of Milk 1276.2 Fat 1276.2.1 Fat Globules 1276.2.2 Milkfat Globule Membrane 1286.2.3 Cream 1296.3 Protein 1336.3.1 Types of Protein 1336.3.2 Casein Micelles in Bovine Milk 1336.3.3 Casein Micelles in Caprine Milk 1336.3.4 Casein Micelles in Milk of Other Species 1366.3.5 Micelle Structure 1366.4 Bacteria and Somatic Cells 1376.5 Concentrated Milk 1386.6 Digested Milk 1406.7 Conclusion 142Acknowledgments 142References 1427 Microstructure of Cheese Products 145Bhavbhuti M. Mehta7.1 Introduction 1457.2 Factors Affecting the Development of Microstructures in Cheeses 1467.2.1 Addition of Calcium Chloride 1487.2.2 Rennet Coagulation 1497.2.3 Acid?Coagulation 1507.2.4 Coagulation Temperature 1507.2.5 Syneresis 1517.2.6 Salting 1517.2.7 Ripening 1527.2.8 Homogenization and High Pressure Treatments 1537.2.9 Evaporation and Ultrafiltration Treatments 1557.2.10 Freezing 1567.2.11 Fat Replacers 1567.3 Microstructures of Various Components in Cheese Matrix 1587.3.1 Protein in Cheese Matrix 1587.3.2 Fat Globule in Cheese Matrix 1597.3.3 Calcium in Cheese Matrix 1627.4 Crystals in Cheese Matrix 1627.5 Starter Bacteria in Cheese Matrix 1637.6 Microstructure of Selected Varieties of Cheeses 1647.6.1 Processed Cheese 1647.6.1.1 Curd Granules and Fat 1667.6.1.2 Occurrence of Crystals 1667.6.2 Cheese Analogs 1667.6.3 Feta Cheese 1677.6.4 Domiati Cheese 1677.6.5 Fresh Cheese 1677.6.6 Cream Cheese 1687.6.7 Mold?Ripened Cheeses 1697.6.8 Cheese Powder 1697.7 Cheese Matrix and Digestion 1707.8 Conclusions 171References 1718 Microstructural Aspects of Yogurt and Fermented Milk 181P.H.P. Prasanna, C.S. Ranadheera, and J.K. Vidanarachchi8.1 Yogurt and Fermented Milk: An Overview 1818.2 Yogurt and Fermented Milk: Production Technologies 1848.3 Microstructure of Yogurt and Fermented Milk 1878.4 Factors Influencing Microstructure of Yogurt and Fermented Milk 1888.4.1 Effects of Type of Milk on Structure 1888.4.2 Rate of Inoculation Level and Starter Culture Composition on Microstructure of Yogurt and Fermented Milk 1898.4.2.1 Rate of Inoculation 1898.4.2.2 Culture Composition 1898.4.3 Effect of Exopolysaccharide Producing Starter Culture on Microstructure 1908.4.4 Incubation Temperature on Structure 1918.4.5 Effect of Different Processing Steps 1918.4.5.1 Homogenization of Milk 1918.4.5.2 Heat Treatment of Milk 1928.4.5.3 Effect of Stirring 1928.4.6 Effect of Addition of Different Hydrocolloids and Fibers on Microstructure 1938.5 Microscopy Methods Used for Analyzing Microstructure of Fermented Milk 1948.5.1 Light Microscopy 1948.5.1.1 Bright Field Light Microscopy 1948.5.1.2 Polarized Light Microscopy 1948.5.1.3 Fluorescence Microscopy 1958.5.1.4 Confocal Laser Scanning Microscopy 1978.5.2 Electron Microscopy 1988.5.2.1 Scanning Electron Microscopy 1988.5.2.2 Transmission Electron Microscopy 2008.6 Conclusions 201References 2029 Microstructure of Milk Fat and its Products 209Pere Randy R. Ramel and Alejandro G. Marangoni9.1 Introduction 2099.2 Milk Fat Crystal Structure 2119.2.1 Mesoscale Structure of Milk Fat 2119.2.1.1 Polymorphism 2119.2.1.2 Phase Behavior and Fractionation 2139.2.1.3 Solid Fat Content and Crystallization/Melting Behavior 2149.2.2 Nanoscale Structure of Fat Crystal Networks 2169.3 Effect of Different Factors on the Crystallization Behavior and Microstructure of Milk Fat 2189.3.1 Processing Conditions 2189.3.1.1 Different Crystallization Mechanisms 2189.3.1.2 Crystallization Temperature and Cooling Rate 2189.3.1.3 Agitation, Shear and Ultrasound 2199.3.2 Composition 2209.3.2.1 Minor Components 2209.3.2.2 Blending with Different Fats and Oils, and Waxes 2209.3.3 In a Dispersed State (Emulsion) 2219.3.3.1 Emulsified State (Cream) vs Bulk State or Anhydrous Milk Fat (AMF) 2229.3.3.2 Emulsion Droplet Size 2229.3.3.3 Addition of Emulsifiers 2239.3.4 In Food Matrices 2239.3.4.1 Water?in?Oil Emulsion 2239.3.4.2 Foamed Emulsions 2249.3.4.3 Chocolate 2259.3.4.4 Cheese 2269.4 Impact of Resulting Microstructure on the Properties of Different Milk Fat Products 2269.4.1 Rheology 2269.4.2 Thermal Stability 2299.4.3 Sensory Qualities 2299.5 Conclusions 229References 23010 Microstructure of Ice Cream and Frozen Dairy Desserts 237Samantha R. VanWees and Richard W. Hartel10.1 Overview of Frozen Desserts 23710.1.1 Ingredients 23810.1.2 Processing 23910.2 Frozen Dessert Structure 24010.2.1 Serum Phase 24010.2.2 Ice Crystals 24210.2.3 Fat Phase 24510.2.4 Air Cells 24710.2.5 Proteins and Hydrocolloids 25010.3 Storage 25110.3.1 Recrystallization 25110.3.2 Sugar Crystallization 25310.3.3 Air Coarsening 25410.3.4 Shrinkage 25510.4 Conclusion 256References 25611 Whey Wastes and Powders 261J. Chandrapala11.1 Whey 26111.2 Current Whey Uses 26311.3 Processing of Liquid Whey 26311.3.1 Recovery of Casein Fines and the Separation of Fat 26411.3.2 Concentration of Total Solids 26511.3.3 Drying 26611.3.4 Fractionation of Total Solids 27011.4 Whey Powders 27411.4.1 Whey Protein Concentrates 27511.4.2 Whey Protein Isolates 27711.4.3 Whey Protein Hydroxylates 27911.4.4 Other Whey Powders 28011.4.4.1 Defatted Whey Protein Concentrates 28011.4.4.2 Demineralized Whey Protein Concentrates 28011.4.4.3 Delactosed Whey Powders 28311.4.4.4 Acid Whey Powders 28311.4.4.5 Salty Whey Powders 28411.5 Utilization and Applications of Whey Powders 28511.6 Conclusion 287References 28712 Microstructure of Selected Traditional Indian Dairy Products 293Bhavbhuti M. Mehta12.1 Introduction 29312.2 Heat Desiccated Dairy Products 29412.2.1 Khoa and Khoa?Based Sweets 29412.2.1.1 Microstructure of Khoa 29412.2.1.2 Microstructure of Gulabjamun 29512.2.1.3 Microstructure of Burfi and Kalakand 29812.3 Heat?Desiccated Milk Cereal Based Desserts 29912.3.1 Microstructure of Kheer 29912.4 Heat?Acid Coagulated Dairy Products 30012.4.1 Microstructure of Paneer 30012.4.1.1 Fried Paneer 30012.4.2 Microstructure of Chhana and Chhana Based Sweets 30212.4.2.1 Microstructure of Rasogolla 30212.4.2.2 Microstructure of Chhana Podo 30512.5 Fermented Dairy Products 30612.5.1 Microstructure of Dahi 30612.5.2 Microstructure of Shrikhand 30612.6 Conclusion 307References 30713 Using Microscopy for Microorganism Localization within Dairy Products 311I.T. Smykov13.1 Introduction 311PART 1 31213.1.1 Microorganisms and Starters 31213.1.2 Techniques Used in the Microstructure Analyses 31313.1.3 Interactions Occurring in the Microstructure 315PART 2 31813.2 Materials and Methods 31813.2.1 Bacterial Strains and Dairy Products 31813.2.2 Electron Microscopy 31813.2.2.1 Surface Topography Heavy Metal Shadowing 31913.2.2.2 Negative Staining Transmission Electron Microscopy 31913.2.3 Freeze?Fracture Replication 31913.3 Results and Discussion 32013.3.1 Casein Micelle 32013.3.2 Bacteria 32413.3.3 Bacteria in a Protein Matrix 32713.3.4 Bacteria in Cheese Eyes 33113.3.5 Bacteria in Yoghurt 33313.3.6 Bacteriophages 33613.4 Conclusions 338Acknowledgment 339References 33914 Microstructure of Dairy Products: Challenges and Future Trends 345Marice Nogueira de Oliveira14.1 Introducing Microstructure of Dairy Products 34514.2 Microstructure of Fermented Milks 34614.3 Microstructure of Yogurt and Milk Drinks 34714.3.1 Yogurt 34714.3.2 Milk Drinks or Lactic Beverages 35414.4 Microstructure of Cheeses 35614.5 Conclusion 359References 359Index 363

Citation preview

Microstructure of Dairy Products

Microstructure of Dairy Products First Edition

Edited by Mamdouh Mahmoud Abdel‐Rahman El‐Bakry Universitat Autònoma of Barcelona Barcelona, Spain

Antoni Sanchez

Universitat Autònoma of Barcelona Barcelona, Spain

Bhavbhuti M. Mehta

Anand Agricultural University Gujarat, India

This edition first published 2018 © 2018 John Wiley & Sons Ltd All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. The right of Mamdouh Mahmoud Abdel-Rahman El-Bakry, Antoni Sanchez, and Bhavbhuti M. Mehta to be identified as the editors of the editorial material in this work has been asserted in accordance with law. Registered Office(s) John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial Office The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com. Wiley also publishes its books in a variety of electronic formats and by print‐on‐demand. Some content that appears in standard print versions of this book may not be available in other formats. Limit of Liability/Disclaimer of Warranty While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Library of Congress Cataloging‐in‐Publication Data has been applied for: 9781118964224

Cover Design: Wiley Cover Image: © Biophoto Associates/Science Source Images Set in 10/12pt WarnockPro by SPi Global, Chennai, India 10 9 8 7 6 5 4 3 2 1

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Contents List of Contributors  xiii Preface  xv 1

Microscopy Techniques for Dairy Products – An Introduction  1 Mark A.E. Auty

1.1 Introduction  1 1.1.1 Brief History and Background  1 1.2 Conventional Optical Microscopy Techniques  4 1.2.1 Conventional Light Microscopy – Optical Contrast  4 1.2.1.1 Bright Field  4 1.2.1.2 Polarized Light  4 1.2.1.3 Phase Contrast  4 1.2.1.4 Differential Interference Contrast  5 1.2.1.5 Fluorescence 5 1.2.2 Chemical Contrast Techniques in Light Microscopy  5 1.3 Confocal Scanning Laser Microscopy  6 1.3.1 Confocal Principle  6 1.3.2 Identifying Dairy Primary Components in CSLM: Labeling Strategies  8 1.3.2.1 Generic Labeling  8 1.3.2.2 Specific Labeling  10 1.3.2.3 Covalent Labeling  11 1.3.3 Some Applications of Confocal Microscopy to Dairy Products and Ingredients  12 1.3.3.1 Spreads 12 1.3.3.2 Emulsions and Foams  12 1.3.3.3 Fermented Milks  12 1.3.3.4 Cheese 13 1.3.3.5 Dairy Powders  13 1.3.3.6 Milk Protein Gel Systems  14 1.3.3.7 Dynamic CSLM Techniques  14 1.4 Electron Microscopy (EM) Techniques  16 1.4.1 Transmission Electron Microscopy  16 1.4.2 Scanning Electron Microscopy  18 1.4.3 Other EM Techniques  18

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1.4.3.1 X‐ray Microanalysis  18 1.4.3.2 Cryo‐electron Microscopy  19 1.4.3.3 Environmental and Variable Pressure SEM  20 1.5 Emerging Microscopy Techniques  20 1.5.1 Atomic Force Microscopy  20 1.5.2 Advanced Fluorescence Microscopy Techniques  22 1.5.3 Confocal Raman Microscopy  22 1.5.4 X‐ray Nano/Microtomography  22 1.5.5 Super‐Resolution Microscopy  23 1.6 Image Analysis  23 1.7 Conclusions  24 References  24 2

Light Microscopy and CSLM Techniques, Principles and Applications  33 Johan Hazekamp

2.1 Introduction  33 2.1.1 The History of Microscopy  33 2.1.2 Evolution of Confocal Microscopy  34 2.1.3 Food Microscopy  35 2.1.4 Wide Field Microscopy  36 2.1.5 Confocal Scanning Laser Microscopy (CSLM)  38 2.2 Sample Preparation and Specific Staining and Labeling  41 2.2.1 Specific Labeling  44 2.2.2 Dynamic Imaging  46 2.2.3 Future Perspectives  46 References  47 3

Electron Microscopy Techniques  51 Semih Otles and Vasfiye Hazal Ozyurt

3.1 Introduction  51 3.2 Types of EM  51 3.2.1 Scanning Electron Microscopy (SEM)  51 3.2.2 Transmission Electron Microscopy (TEM)  52 3.2.3 Cryo‐SEM  52 3.2.4 Cryo‐TEM  53 3.2.5 Environmental Scanning Electron Microscopy (ESEM)  53 3.3 Sample Preparation for EMs  53 3.3.1 Scanning Electron Microscopy  53 3.3.2 Transmission Electron Microscopy  53 3.3.3 Cryo‐Scanning Electron Microscopy  53 3.4 Dairy Microstructure  54 3.5 Electron Microscopy for the Dairy Product  54 3.6 Summary  60 References  64

Contents

4

Emerging Techniques for Microstructural Analysis  67 I. Hernando, E. Llorca, and A. Quiles

4.1 Introduction  67 4.2 Scanning Probe Microscopy  67 4.2.1 Scanning Tunneling Microscope (STM)  69 4.2.2 Atomic Force Microscope (AFM)  70 4.2.3 Applications of the Main Probe Microscopes  71 4.3 X‐Ray Tomography  72 4.4 Small‐Angle‐Scattering (SAS) Methods: SAXS and SANS  74 4.4.1 Small‐Angle X‐Ray Scattering (SAXS)  74 4.4.2 Small‐Angle Neutron Scattering (SANS)  75 4.4.3 Applications of Small‐Angle‐Scattering Methods  75 4.5 Vibrational Spectroscopies (Fourier Transform Infrared‐FTIR and Raman Microscopy)  75 4.5.1 Fourier Transform Infrared (FTIR) Spectroscopy  76 4.5.2 Raman Spectroscopy  78 4.6 Magnetic Resonance: NMR and MRI  80 4.7 Conclusions  82 References  82 5

Quantitative Image Analysis in Microscopy  89 Gaetano Impoco

5.1 Aim and Scope  89 5.2 Image Analysis Software  90 5.3 Applications to Microscopy for Dairy Science  97 5.3.1 Porosity  98 5.3.2 Fat Globules  99 5.3.3 Microbial Cells  100 5.4 Image Analysis and Quantitative Measurement  100 5.4.1 Image Analysis Basics  101 5.4.1.1 Feature Detection  102 5.4.1.2 Quantitative Analysis  103 5.4.2 Common Pitfalls  105 5.4.3 Misuse and Wrong Interpretation of Image Analysis Results  114 5.4.4 Good Practices  116 5.4.5 Image Analysis in your Lab  119 5.5 Conclusions  122 Acknowledgments  123 References  123 6

Microstructure of Milk  127 Michael H. Tunick

6.1 Components of Milk  127 6.2 Fat  127 6.2.1 Fat Globules  127 6.2.2 Milkfat Globule Membrane  128

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6.2.3 Cream  129 6.3 Protein  133 6.3.1 Types of Protein  133 6.3.2 Casein Micelles in Bovine Milk  133 6.3.3 Casein Micelles in Caprine Milk  133 6.3.4 Casein Micelles in Milk of Other Species  136 6.3.5 Micelle Structure  136 6.4 Bacteria and Somatic Cells  137 6.5 Concentrated Milk  138 6.6 Digested Milk  140 6.7 Conclusion  142 Acknowledgments  142 References  142 7

Microstructure of Cheese Products  145 Bhavbhuti M. Mehta

7.1 Introduction  145 7.2 Factors Affecting the Development of Microstructures in Cheeses  146 7.2.1 Addition of Calcium Chloride  148 7.2.2 Rennet Coagulation  149 7.2.3 Acid‐Coagulation  150 7.2.4 Coagulation Temperature  150 7.2.5 Syneresis  151 7.2.6 Salting  151 7.2.7 Ripening  152 7.2.8 Homogenization and High Pressure Treatments  153 7.2.9 Evaporation and Ultrafiltration Treatments  155 7.2.10 Freezing  156 7.2.11 Fat Replacers  156 7.3 Microstructures of Various Components in Cheese Matrix  158 7.3.1 Protein in Cheese Matrix  158 7.3.2 Fat Globule in Cheese Matrix  159 7.3.3 Calcium in Cheese Matrix  162 7.4 Crystals in Cheese Matrix  162 7.5 Starter Bacteria in Cheese Matrix  163 7.6 Microstructure of Selected Varieties of Cheeses  164 7.6.1 Processed Cheese  164 7.6.1.1 Curd Granules and Fat  166 7.6.1.2 Occurrence of Crystals  166 7.6.2 Cheese Analogs  166 7.6.3 Feta Cheese  167 7.6.4 Domiati Cheese  167 7.6.5 Fresh Cheese  167 7.6.6 Cream Cheese  168 7.6.7 Mold‐Ripened Cheeses  169 7.6.8 Cheese Powder  169 7.7 Cheese Matrix and Digestion  170

Contents

7.8 Conclusions  171 References  171 8

Microstructural Aspects of Yogurt and Fermented Milk  181 P.H.P. Prasanna, C.S. Ranadheera, and J.K. Vidanarachchi

8.1 8.2 8.3 8.4 8.4.1 8.4.2

Yogurt and Fermented Milk: An Overview  181 Yogurt and Fermented Milk: Production Technologies  184 Microstructure of Yogurt and Fermented Milk  187 Factors Influencing Microstructure of Yogurt and Fermented Milk  188 Effects of Type of Milk on Structure  188 Rate of Inoculation Level and Starter Culture Composition on Microstructure of Yogurt and Fermented Milk  189 8.4.2.1 Rate of Inoculation  189 8.4.2.2 Culture Composition  189 8.4.3 Effect of Exopolysaccharide Producing Starter Culture on Microstructure  190 8.4.4 Incubation Temperature on Structure  191 8.4.5 Effect of Different Processing Steps  191 8.4.5.1 Homogenization of Milk  191 8.4.5.2 Heat Treatment of Milk  192 8.4.5.3 Effect of Stirring  192 8.4.6 Effect of Addition of Different Hydrocolloids and Fibers on Microstructure  193 8.5 Microscopy Methods Used for Analyzing Microstructure of Fermented Milk  194 8.5.1 Light Microscopy  194 8.5.1.1 Bright Field Light Microscopy  194 8.5.1.2 Polarized Light Microscopy  194 8.5.1.3 Fluorescence Microscopy  195 8.5.1.4 Confocal Laser Scanning Microscopy  197 8.5.2 Electron Microscopy  198 8.5.2.1 Scanning Electron Microscopy  198 8.5.2.2 Transmission Electron Microscopy  200 8.6 Conclusions  201 References  202

9

Microstructure of Milk Fat and its Products  209 Pere Randy R. Ramel and Alejandro G. Marangoni

9.1 Introduction  209 9.2 Milk Fat Crystal Structure  211 9.2.1 Mesoscale Structure of Milk Fat  211 9.2.1.1 Polymorphism 211 9.2.1.2 Phase Behavior and Fractionation  213 9.2.1.3 Solid Fat Content and Crystallization/Melting Behavior  214 9.2.2 Nanoscale Structure of Fat Crystal Networks  216 9.3 Effect of Different Factors on the Crystallization Behavior and Microstructure of Milk Fat  218 9.3.1 Processing Conditions  218

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9.3.1.1 Different Crystallization Mechanisms  218 9.3.1.2 Crystallization Temperature and Cooling Rate  218 9.3.1.3 Agitation, Shear and Ultrasound  219 9.3.2 Composition  220 9.3.2.1 Minor Components  220 9.3.2.2 Blending with Different Fats and Oils, and Waxes  220 9.3.3 In a Dispersed State (Emulsion)  221 9.3.3.1 Emulsified State (Cream) vs Bulk State or Anhydrous Milk Fat (AMF)  222 9.3.3.2 Emulsion Droplet Size  222 9.3.3.3 Addition of Emulsifiers  223 9.3.4 In Food Matrices  223 9.3.4.1 Water‐in‐Oil Emulsion  223 9.3.4.2 Foamed Emulsions  224 9.3.4.3 Chocolate 225 9.3.4.4 Cheese 226 9.4 Impact of Resulting Microstructure on the Properties of Different Milk Fat Products  226 9.4.1 Rheology  226 9.4.2 Thermal Stability  229 9.4.3 Sensory Qualities  229 9.5 Conclusions  229 References  230 10

Microstructure of Ice Cream and Frozen Dairy Desserts  237 Samantha R. VanWees and Richard W. Hartel

10.1 Overview of Frozen Desserts  237 10.1.1 Ingredients  238 10.1.2 Processing  239 10.2 Frozen Dessert Structure  240 10.2.1 Serum Phase  240 10.2.2 Ice Crystals  242 10.2.3 Fat Phase  245 10.2.4 Air Cells  247 10.2.5 Proteins and Hydrocolloids  250 10.3 Storage  251 10.3.1 Recrystallization  251 10.3.2 Sugar Crystallization  253 10.3.3 Air Coarsening  254 10.3.4 Shrinkage  255 10.4 Conclusion  256 References  256 11

Whey Wastes and Powders  261 J. Chandrapala

11.1 Whey  261 11.2 Current Whey Uses  263 11.3 Processing of Liquid Whey  263

Contents

11.3.1 Recovery of Casein Fines and the Separation of Fat  264 11.3.2 Concentration of Total Solids  265 11.3.3 Drying  266 11.3.4 Fractionation of Total Solids  270 11.4 Whey Powders  274 11.4.1 Whey Protein Concentrates  275 11.4.2 Whey Protein Isolates  277 11.4.3 Whey Protein Hydroxylates  279 11.4.4 Other Whey Powders  280 11.4.4.1 Defatted Whey Protein Concentrates  280 11.4.4.2 Demineralized Whey Protein Concentrates  280 11.4.4.3 Delactosed Whey Powders  283 11.4.4.4 Acid Whey Powders  283 11.4.4.5 Salty Whey Powders  284 11.5 Utilization and Applications of Whey Powders  285 11.6 Conclusion  287 References  287 12

Microstructure of Selected Traditional Indian Dairy Products  293 Bhavbhuti M. Mehta

12.1 Introduction  293 12.2 Heat Desiccated Dairy Products  294 12.2.1 Khoa and Khoa‐Based Sweets  294 12.2.1.1 Microstructure of Khoa  294 12.2.1.2 Microstructure of Gulabjamun  295 12.2.1.3 Microstructure of Burfi and Kalakand  298 12.3 Heat‐Desiccated Milk Cereal Based Desserts  299 12.3.1 Microstructure of Kheer  299 12.4 Heat‐Acid Coagulated Dairy Products  300 12.4.1 Microstructure of Paneer  300 12.4.1.1 Fried Paneer  300 12.4.2 Microstructure of Chhana and Chhana Based Sweets  302 12.4.2.1 Microstructure of Rasogolla  302 12.4.2.2 Microstructure of Chhana Podo  305 12.5 Fermented Dairy Products  306 12.5.1 Microstructure of Dahi  306 12.5.2 Microstructure of Shrikhand  306 12.6 Conclusion  307 References  307 13

Using Microscopy for Microorganism Localization within Dairy Products  311 I.T. Smykov

13.1 Introduction  311 PART 1  312 13.1.1 Microorganisms and Starters  312 13.1.2 Techniques Used in the Microstructure Analyses  313 13.1.3 Interactions Occurring in the Microstructure  315

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PART 2  318 13.2 Materials and Methods  318 13.2.1 Bacterial Strains and Dairy Products  318 13.2.2 Electron Microscopy  318 13.2.2.1 Surface Topography Heavy Metal Shadowing  319 13.2.2.2 Negative Staining Transmission Electron Microscopy  319 13.2.3 Freeze‐Fracture Replication  319 13.3 Results and Discussion  320 13.3.1 Casein Micelle  320 13.3.2 Bacteria  324 13.3.3 Bacteria in a Protein Matrix  327 13.3.4 Bacteria in Cheese Eyes  331 13.3.5 Bacteria in Yoghurt  333 13.3.6 Bacteriophages  336 13.4 Conclusions  338 Acknowledgment  339 References  339 14

Microstructure of Dairy Products: Challenges and Future Trends  345 Maricê Nogueira de Oliveira

14.1 Introducing Microstructure of Dairy Products  345 14.2 Microstructure of Fermented Milks  346 14.3 Microstructure of Yogurt and Milk Drinks  347 14.3.1 Yogurt  347 14.3.2 Milk Drinks or Lactic Beverages  354 14.4 Microstructure of Cheeses  356 14.5 Conclusion  359 References  359 Index  363

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List of Contributors M. Auty

E. Llorca

Food Chemistry & Technology Department Teagasc Food Research Centre Teagasc, Moorepark Co. Cork, Ireland

Departamento de Tecnología de Alimentos Universitat Politècnica de València Valencia, Spain

J. Chandrapala

Food Science Building University of Guelph Guelph, Ont. Canada

School of Science RMIT University Bundoora, Victoria Australia

A.G. Marangoni

Bhavbhuti M. Mehta

University of Wisconsin‐Madison Madison, WI, USA

Dairy Chemistry Department SMC College of Dairy Science Anand Agricultural University Anand, Gujarat, India

J. Hazekamp

M.N. Oliveira

Unilever R&D Colworth Science Park Sharnbrook, Bedfordshire United Kingdom

Department of Biochemical and Pharmaceutical Technology University of São Paulo, Brazil

I. Hernando

Department of Food Engineering Faculty of Engineering Ege University Izmir, Turkey

R.W. Hartel

Departamento de Tecnología de Alimentos Universitat Politècnica de València Valencia, Spain G. Impoco

CoRFiLaC Ragusa, Italy

S. Otles

V. Ozyurt

Graduate School of Natural and Applied Sciences Food Engineering Branch

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List of Contributors

Ege University Izmir, Turkey P.H.P. Prasanna

Department of Animal & Food Sciences Faculty of Agriculture Rajarata University of Sri Lanka Anuradhapura, Sri Lanka A. Quiles

Departamento de Tecnología de Alimentos Universitat Politècnica de València Valencia, Spain P.R. Ramel

Food Science Building University of Guelph Guelph, Ont. Canada C.S. Ranadheera

Advanced Food Systems Research Unit College of Health & Biomedicine Victoria University Werribee Campus Werribee, Victoria, Australia

I.T. Smykov

All‐Russian Scientific Research Institute for Butter and Cheese Making Uglich, Russia M.H. Tunick

Center for Food & Hospitality Management Drexel University Philadelphia PA, USA S.R. VanWees

University of Wisconsin‐Madison Madison, WI, USA J.K. Vidanarachchi

Department of Animal Science Faculty of Agriculture University of Peradeniya Peradeniya, Sri Lanka

xv

Preface The idea of the edited book Microstructure of Dairy Products has evolved from the fact that it is difficult to find recent books related to and focusing on the microstructure analyses of dairy products in addition to their detailed microstructural aspects. Microstructure has been studied for several decades; however, the few recent specialized books that discuss the microstructure of food matrices have no focus on the microstructure of dairy products. Microstructure of Dairy Products is considered as a timely multi‐author text, with contributors from the USA, Europe, Canada, Australia, Brazil, India and other parts of the world. Microstructure significantly affects all end‐product processing characteristics. These are functional properties, which include mainly textural and rheological parameters, and flavor or sensory properties. Therefore, it is essential to understand fully the microstructure of these food products. Microstructure of Dairy Products provides a full description and updates of the most recent developments of microscopy techniques used and analyses of the microstructure of dairy products. The book may help in areas related to microstructural analyses, and to studies on the relationship between microstructure, functionality and flavor. Currently, there is a need for systematic microstructure studies of most dairy products, in order to provide an insight into the understanding of the different phenomena that relate to functional and biochemical changes during processing and subsequent storage. The topics in Microstructure of Dairy Products are of great interest to everyone involved in the manufacture of dairy products, through to dairy consultants and scientists who are involved in product development and troubleshooting. The topic has been extensively researched, and the result of this widespread interest is that many articles on the structure of different dairy products have been published in scientific journals, targeted at very specific groups of scientists. This book enables an easy knowledge transfer of a comprehensive and global overview to the reader. For the sake of clarity, there are various chapters dealing separately with different dairy products. For example, a researcher might be working/interested only in dairy fat products rather than fermented milks. The book consists of 14 chapters, spanning about 400 pages. There are two main parts: 1) Overview of microscopy techniques used, where different types of the following techniques are discussed in detail: light microscopy, electron microscopy and emerging microscopy techniques (Chapters 1–4). This is followed by a chapter on the quantitative analyses of micrographs and the software used in microstructural analyses (Chapter 5).

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Preface

2) Microstructure of various dairy foods (Chapters 6–12). This part is divided into sections related to the microstructure of milk, cheeses, yoghurts, fat products, ice cream and frozen dairy desserts, dairy powders and selected traditional Indian dairy products. In addition, Chapter 13 reviews the localization of microorganisms within the microstructure of various dairy products. The last chapter discusses the challenges and future trends of the microstructure of dairy products (Chapter 14). This book is aimed at the following potential audiences. Microstructure of Dairy Products, which serves as an essential stand‐alone source, is primarily recommended in academia as well as the food industry and especially dairy science and technology. In addition, physicists and microscopists can benefit from this book as it provides updated information on the description, uses and applications of microscopy techniques in the microstructural analyses of dairy products. Other audiences include graduate students and researchers in the field of pure sciences such as biology, physics and chemistry. It is always useful to have an updated knowledge about microscopy techniques and their benefits and challenges, and accordingly the future research that is required. It is hoped that this text will become an important component of the book series in the field of dairy microstructure. Mamdouh Mahmoud Abdel‐Rahman El‐Bakry, Antoni Sanchez, and Bhavbhuti M. Mehta Editors

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1 Microscopy Techniques for Dairy Products – An Introduction Mark A.E. Auty Food Chemistry and Technology Department, Teagasc Food Research Centre, Teagasc, Moorepark, Co. Cork, Ireland

1.1 ­Introduction The textural properties of a particular dairy product are strongly influenced by the three‐dimensional arrangement of its structural elements and their interactions (Heertje, 1993). To fully understand the behavior of dairy products, it is therefore not enough to know the chemical composition and bulk physical properties but how they interact and affect the spatial arrangement or organization of the food constituents at the nano‐ and micro‐length scales. Food microstructure studies therefore provide a link between physico‐chemical properties, process behavior and organoleptic qualities of a particular dairy product (Figure 1.1). Linking microscopy with rheological and sensory techniques in particular is necessary for a fuller understanding of food behavior, requiring a multivariate approach to experimental design. This chapter gives a brief overview of the different types of microscopy used to study dairy foods with a focus on confocal microscopy as this is arguably the most useful single technique of benefit to both researchers and food industry technologists. 1.1.1  Brief History and Background In the seventeenth century, Antonie van Leeuwenhoek, using a high magnification hand lens, first viewed fat droplets in milk (Leeuwenhoek, 1674). Despite this early start, microscopy of dairy products, and food in general, remained unexplored, with little published literature until well after the development of electron microscopy techniques in the 1940s. As food manufacturers began using microscopes in the 1950s and 1960s, it became apparent that the structural arrangement of food components strongly influenced food processing and quality. Most of the early food‐related electron microscopy work was performed on dairy products, mainly yoghurt and cheese (for reviews see Brooker, 1979; Kalab, 1979a, b, c, 1981, 1993; Holcomb, 1991; Schmidt and Bucheim, 1992). Despite the enormous influence of light microscopy on medical research at the end of the last century and the improvement in optic materials and design, conventional light microscopy of food products remained largely neglected although Lewis (1978) Microstructure of Dairy Products, First Edition. Edited by Mamdouh Mahmoud Abdel-Rahman El-Bakry, Antoni Sanchez, and Bhavbhuti M. Mehta. © 2018 John Wiley & Sons Ltd. Published 2018 by John Wiley & Sons Ltd.

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1  Microscopy Techniques for Dairy Products – An Introduction

Ingredients • • • • • • • •

• • • • • • • • •

Processing

Proteins Fats Carbohydrates Salts Emulsifiers Stabilisers Water/solvents Vitamins/trace elements

• • • • • • •

Temperature Time Mixing/shear Pressure pH Ionic strength Mass/thermal transport

Microstructure

Physical Properties

Spatial distribution Strand length Particle size/shape Flexibility Porosity Alignment Connectivity Film thickness Interactions

• • • • •

Organoleptic Properties • • • • • •

Creaminess Crispness Softness Spreadability Mouthfeel Flavor release

Viscosity Gel strength Hardness Emulsion stability Water holding capacity • Elasticity

Nutritional Properties (Matrix effect) • • • • •

Bio-activity Bio-accessibility Bio-absorption Satiety Gut health

Figure 1.1  Diagram showing inter‐relationships between microstructure and functionality of dairy products.

and Flint (1994) published selected methods for light microscopic examination of a range of food ingredients and products, including milk powders and dairy spreads. Contrast between the component of interest and surrounding food material may be achieved by optical techniques, chemical staining, or a combination of both (Flint, 1994). Despite this, optical microscopy of dairy products remained largely neglected until the development of commercial confocal microscopes in the 1990s. In the past 20  years, there has been considerable research interest in food microstructure as a key  to understanding structure‐function relationships. A wide range of microscopy techniques is now available for the study of food microstructure, with more being developed (for a review see Morris and Groves, 2013). These techniques are frequently employed to study dairy products such as cheese (El‐Bakry and Sheehan, 2014). The food researcher now has a large toolbox of techniques, the choice of which depends on

1.1 Introduction

the particular application. However, a correlative approach employing various microscopy techniques is required to provide a fuller understanding of complex multiphase nano‐ and microstructures (Aguilera and Stanley, 1990; Lewis, 1993). This approach has led to the development of hybrid microscopes such as the RISE (WITech, Ulm, Germany) system which combines a scanning electron microscope with Raman confocal, focused ion beam and even atomic force microscopes, permitting examination of the same sample area by different microscopy techniques. Many of the common techniques used to study food microstructure have been adapted from specimen preparation procedures for biological tissue. However, there are particular problems associated with the preparation of food products for microscopic examination that the researcher should be aware of. Many foods have high levels of moisture, fat or sugar and preserving the original microstructure of such materials may be difficult, particularly for electron microscopic studies that may require low moisture, conductive specimens. Dried ingredients, such as spray dried powders, crystalline sugars, starches etc. with a moderately small particle size (