P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come Chocolate Science and Technology Emmanuel Ohene Afoakwa University of Ghana Legon – Accra Ghana and formerly Nestle´ Product Technology Centre York UK A John Wiley & Sons, Ltd., Publication P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come Chocolate Science and Technology P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come Dedication This book is dedicated to my dear wife Ellen and our three lovely children, Nana Afra, Maame Agyeiwaa and Kwabena Ohene-Afoakwa (Jnr), whose wisdom, prayers and support have helped me achieve great success in my life. P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come Chocolate Science and Technology Emmanuel Ohene Afoakwa University of Ghana Legon – Accra Ghana and formerly Nestle´ Product Technology Centre York UK A John Wiley & Sons, Ltd., Publication P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come This edition first published 2010 C 2010 Emmanuel Ohene Afoakwa Blackwell Publishing was acquired by John Wiley & Sons in February 2007. Blackwell’s publishing programme has been merged with Wiley’s global Scientific, Technical, and Medical business to form Wiley-Blackwell. Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom Editorial offices 9600 Garsington Road, Oxford, OX4 2DQ, United Kingdom 2121 State Avenue, Ames, Iowa 50014-8300, USA For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell. The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988. 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 the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Afoakwa, Emmanuel Ohene. Chocolate science and technology / Emmanuel Ohene Afoakwa. p. cm. Includes bibliographical references and index. ISBN 978-1-4051-9906-3 (hardback : alk. paper) 1. Cocoa. 2. Chocolate. I. Title. TP640.A36 2010 664.5–dc22 2009046211 A catalogue record for this book is available from the British Library. Set in 10/12 pt Times by Aptara R Inc., New Delhi, India Printed in Singapore 1 2010 P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come Contents Preface xi Acknowledgements xiii About the author xv 1 Chocolate production and consumption patterns 1 1.1 History of cocoa and chocolate 1 1.2 World production and consumption of cocoa and chocolate products 2 1.2.1 World production and consumption of cocoa 2 1.2.2 World cocoa prices 4 1.2.3 World consumption of chocolate products 5 1.2.4 World consumption of premium chocolate products 6 1.3 Fairtrade cocoa and chocolate in modern confectionery industry 7 1.3.1 Future of Fairtrade cocoa and confectionery industry 9 1.4 The concept of this book 10 2 Cocoa cultivation, bean composition and chocolate flavour precursor formation and character 12 2.1 Introduction 12 2.2 Cocoa cultivation and practices 13 2.2.1 Cultivation of cocoa 13 2.2.2 Flowering and pod development 14 2.2.3 Harvesting and pod opening 16 2.2.4 Cocoa diseases and pests and their influence on chocolate quality 18 2.2.4.1 Swollen shoot disease 19 2.2.4.2 Black pod disease 19 2.2.4.3 Witches broom disease 20 2.2.4.4 Pod borers (capsids, cocoa thrips and mealybugs) 20 2.3 Bean composition and flavour precursor formation 20 2.3.1 Chemical composition of the bean 20 2.3.2 Polyphenols and chocolate flavour quality 21 2.3.3 Effects of proteins and sugars on flavour precursor formation 22 2.3.4 Microbial succession and enzymatic activities during flavour precursor generation in cocoa fermentation 23 2.4 Effect of genotype on cocoa bean flavours 26 2.5 Flavour development during post-harvest treatments of cocoa 27 2.5.1 Fermentation processes 27 2.5.2 Drying 30 2.6 Conclusion 33 P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come vi Contents 3 Industrial chocolate manufacture – processes and factors influencing quality 35 3.1 Introduction 35 3.2 Cocoa processing and technology 36 3.2.1 Bean selection and quality criteria 36 3.2.2 Cleaning, breaking and winnowing 38 3.2.3 Sterilisation 38 3.2.4 Alkalisation 39 3.2.5 Roasting 39 3.2.6 Nib grinding and liquor treatment 40 3.2.7 Liquor pressing 40 3.2.8 Cake grinding (kibbling) 40 3.2.9 Cocoa powder production 41 3.3 Chocolate manufacturing processes 41 3.3.1 Mixing 41 3.3.2 Refining 41 3.3.3 Conching 43 3.4 Tempering, lipid crystallisation and continuous phase character during chocolate manufacture 44 3.5 Particle size distribution in chocolate 47 3.6 Compositional effects on rheological and textural qualities in chocolate 50 3.6.1 The role of fats 50 3.6.2 The role of sugar 51 3.6.3 The role of milk and other dairy components 52 3.6.4 The role of surfactants in modern chocolate confectionery 52 3.7 Moisture and chocolate flow 53 3.8 Chocolate quality and defects 54 3.8.1 Chocolate quality 54 3.8.1.1 Rheological measurements of chocolate quality 54 3.8.1.2 Sensory evaluation of chocolate quality 55 3.8.2 Chocolate defects 55 3.8.2.1 Fat bloom 56 3.8.2.2 Sugar bloom 57 3.9 Conclusion and further research 57 4 The chemistry of flavour development during cocoa processing and chocolate manufacture 58 4.1 Introduction 58 4.2 Influence of bean selection on chocolate flavour quality 58 4.3 Effect of roasting 59 4.3.1 Maillard reactions – aldol condensation, polymerisation and cyclisation 63 4.3.2 Effects of alkalisation 64 4.4 Flavour development during chocolate manufacture 65 4.4.1 Conching 65 4.5 Key flavour compounds in milk chocolate 66 P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come Contents vii 4.6 Key flavour compounds in dark chocolate 68 4.7 Conclusion 71 5 Sensory character and flavour perception of chocolates 73 5.1 Summary and industrial relevance 73 5.2 Introduction 73 5.3 Sensory perception of quality in chocolates 74 5.3.1 Appearance 75 5.3.2 Texture 75 5.3.3 Taste 79 5.3.4 Flavour and aroma 80 5.4 Sensory assessment of chocolates 80 5.5 Factor influencing chocolate flavour 81 5.6 Flavour release and perception of sweetness in chocolate 82 5.7 Dynamism of flavour perception in chocolate 84 5.8 Retronasal flavour release and perception during chocolate consumption 85 5.9 Measurement of flavour release and intensity in chocolates 87 5.10 Electronic noses and tongues as online sensors for sensory assessment of chocolates 89 5.11 Conclusion 89 6 Nutritional and health benefits of cocoa and chocolate consumption 91 6.1 Summary and significance 91 6.2 Introduction 91 6.3 Chemistry and composition of cocoa flavonoids 92 6.4 Chocolate types and their major nutritional constituents 94 6.5 Antioxidant properties and their mechanism of action 95 6.6 Effects on endothelial function, blood pressure and cardiovascular system 96 6.7 Effects on insulin sensitivity and carcinogenic properties 98 6.8 Cocoa, chocolate and aphrodisiac properties 99 6.9 Conclusion 100 7 Structure – properties (rheology, texture and melting) relationships in chocolate manufacture 101 7.1 Summary and industrial relevance 101 7.2 Introduction 102 7.3 Materials and methods 104 7.3.1 Materials 104 7.3.2 Preparation of chocolate samples 105 7.3.3 Determination of particle size distribution 105 7.3.4 Rheological measurements 105 7.3.5 Tempering procedure 108 7.3.6 Texture measurements 109 7.3.7 Colour measurements of solid dark chocolate 111 7.3.8 Microstructure analysis 111 P1: KAE/UKS P2: KAE FM BLBK244-Afoakwa January 25, 2010 15:31 Printer Name: Yet to Come viii Contents 7.3.9 Determination of melting properties of dark chocolates 111 7.3.10 Experimental design and statistical analysis 112 7.4 Results and discussion 112 7.4.1 Particle size distribution of molten dark chocolate 112 7.4.2 Rheological properties of molten dark chocolate 115 7.4.2.1 Casson plastic viscosity 115 7.4.2.2 Casson yield value 116 7.4.2.3 Apparent viscosity 118 7.4.2.4 Yield stress 119 7.4.2.5 Thixotropy 119 7.5 Relationships between casson model and ICA recommendations 120 7.6 Textural properties 123 7.6.1 Molten dark chocolate 123 7.6.2 Hardness