1724_Cover 10/28/04 2:47 PM Page 1 C M Y CM MY CY CMY K Food Science & Technology Introduction to Food Chemistry INTRODUCTION TO INTRODUCTION TO FOOD CHEMISTRY Providing a thorough introduction to a core area specified by the Institute of Food Science, Introduction to Food Chemistry focuses on principles rather than commodities and balances facts and explanations. The text focuses on major themes of Food Chemistry, including the role of chemistry in the food system, expected student based learning outcomes, FOOD CHEMISTRY food analysis, statistical analysis, carbohydrate and polysaccharide ingredients, proteins, lipids and fat mimetics, food material science, rheology, the Maillard reaction and health, nonenzymatic oxidation, food enzymology and biochemical changes in fresh foods. Features • Presents the latest theories in food chemistry in an accessible manner • Provides highlighted keywords for additional reading via the internet • Supplements each chapter with recommended reading This multilevel text presents a wealth of information in a clear and accessible style. It serves as an ideal introduction to a diverse audience, as well as a owusu-apenten supplementary textbook for undergraduate and graduate students in food science courses.
richard owusu-apenten 1724 CRC PRESS www.com CRC PR E S S Composite INTRODUCTION TO FOOD CHEMISTRY INTRODUCTION TO FOOD CHEMISTRY richard owusu-apenten CRC PR E S S Boca Raton London New York Washington, D. CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2004 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U. Government works Version Date: 20160405 International Standard Book Number-13: 978-1-4200-5817-8 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the valid- ity of all materials or the consequences of their use.
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Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.com and the CRC Press Web site at http://www.com To Wenli Preface Food chemistry is the application of chemistry principles to the food system, including agricultural production, storage, transportation, processing, distribution, retail, and con- sumption. The mission statement for food chemists is to ensure a supply of food that is safe, nutritious, and affordable, with due regard for the environment. Food chemistry is a challenging subject for at least three reasons.
First, students of food chemistry need a good grounding in general chemistry. Second, they must possess the will to apply their chemistry knowledge to foods, which are invariably highly complex systems. Third, there is generally only a short time between discovery, integration, education, and application of new food chemistry ideas. There are several advanced food chemistry books on the market, but there are very few introductory texts for food chemists.
This book attempts to fill this niche. There is a balance of facts and explanations. Each chapter contains material for about 5 hours of reading followed by appropriate homework. Typically, food chemistry students have previous experience of college chemistry (organic and physical) and some calculus.
They are computer literate and able to use the Internet for supplementary reading. No previous training in food chemistry is assumed. Familiarity with and/or a willingness to engage some major themes in general chemistry (Chapter 1) is needed. Introduction to Food Chemistry is a multi-level text with material for a diverse audience.
Within each of the twelve chapters, more complex ideas appear near the end. The book will be suitable as a basis for courses in food science with emphasis on food chemistry. Material from some parts of the book could be useful for nutrition majors. Another aim of this book is to help the reader proceed to more specialist monographs and research articles.
Members of the food professions will also benefit from reading this book. Acknowledgments ‘‘It takes a village to raise one child.’’ I am indebted to many people who contributed directly or indirectly to this book. My sincere thanks to Professor D. Povey, and Professor B.
Wedzicha for their inspiration. Yannis Zebatakis, Athens University, for his friendship. Special regards to the many hundreds of students who took the courses FDSC 1020, FDSC 2030, FDSC 3040, and FDSC 5030 at the University of Leeds, UK. Gratitude is due to many present and past food science students at PSU who took FDSC 200, FDSC 201, FDSC 500, FDSC 508, and or FDSC 509.
Without your participation this book would not have been written. I am grateful to my editor, Susan Farmer, and the staff of CRC Press for their help. Thanks are also given to my current boss, John Floros, for putting up with my ‘‘moonlighting.’’ Finally, I thank my Ma and Grandma for their lasting love and patience. Richard Owusu-Apenten State College, PA August 2004 Author Richard Owusu-Apenten BSc, PhD, CChem, MRSC, MIFT graduated with biochemistry (BSc with honors) and chemistry (PhD) degrees from the University of London.
He has taught food chemistry for 15 years in universities in the UK and USA. The author is a chartered chemist and a professional member of the Royal Society of Chemistry, Institute of Food Technology, and the American Chemical Society. Apenten is an associate professor at the College of Agriculture, Pennsylvania State University. Table of Contents Chapter 1.
Chemistry and Food Chemistry: An Overview 1.1 On the need for chemistry 1 1.1 Functional group chemistry 3 1.3 Organic reaction mechanisms 3 1.2 The shapes of molecules 9 1.4 Molecular orbital theory 10 1.1 Definition and scope 11 1.2 Areas of expertise required by the Institute of Food Technology 12 1.3 Chemistry and the food system 12 1.6 Organization of This Book 13 1.1 Structure and rationale 13 1.2 Audience and readership 14 1.3 Specific outcomes 14 Appendix 1.1 Statistical description of entropy 14 Appendix 1.2 Quantity of heat evolved 15 Appendix 1.3 Origins of chemical bonding 16 References 16 Chapter 2.1 Analytical chemistry of foods 17 2.1 Determination of water 18 2.2 Determination of crude protein 20 2.3 Column Chromatographic Analysis 23 2.2 Modes of chromatographic separation 25 2.3 The effciency of chromatographic separations 26 2.2 Properties of electromagnetic radiation 28 2.4 Quantitative absorbance studies 30 References 31 Chapter 3 Statistical Analysis 3.1 Types of data and histograms 33 3.2 The potato chip scenario 34 3.1 The mean or average 35 3.2 Measures of error and scatter 36 3.3 Standard error of the mean 36 3.4 Types of statistical error 37 3.1 Normal distribution curve 37 3.1 Testing a hypothesis about a mean 40 3.2 Testing the hypothesis about two means 40 3.5 Statistical Procedures for Calibration 41 3.2 Calibration using standard samples 41 3.6 Analysis of Variance (ANOVA) 41 3.1 ANOVA test for differences between means 42 3.2 ANOVA for partitioning variances 43 References 44 Chapter 4 Carbohydrates 4.1 Monosaccharides and disaccharides 45 4.2 Glucose ring structure 46 4.3 Reactions of monosaccharides 47 4.4 Polyols or sugar alcohols 49 4.3 Sucrose and Other Disaccharides 50 4.1 Sources and processing 50 4.2 Physical properties of sucrose 50 4.3 Sucrose as a food ingredient 50 4.1 Sources and isolation 51 4.2 Starch and glycogen—storage polysaccharides 52 4.5 Interactions between starch granules and water 53 4.1 Gelation of pectin 54 4.2 Pectin and texture in plant foods 55 4.1 Structure of alginate 56 4.2 Gelation of alginate 57 4.7 Xanthan and Microbial Exo-Polysaccharides 58 4.1 Thickening by xanthan 58 4.2 Applications of xanthan 59 4. Other microbial exo-polysaccharides 59 4.8 Guar, Tara, and Locust Bean Gum 59 4.9 Functionality of Polysaccharides 60 References 60 Chapter 5 Lipids and Fat Replacers 5.1 Definition and classes of lipids 61 5.2 Sources of edible oils 61 5.2 Processing Edible Oils 62 5.1 Nomenclature of fatty acids 65 5.2 Saturated and unsaturated fatty acids 65 5.4 Chemical Reactivity of Fats and Oils 65 5.5 Physical Properties of Triacylglycerides 68 5.6 Functionality of Fats and Oils 72 5.1 Properties versus qualities of fats 72 5.3 Shortening and anti-staling 74 5.4 Fat microstructure and crystal networks 74 5.7 Fat Replacers and Mimetics 75 5.1 Rationale of fat replacers 76 5.3 Fat mimetics 76 References 78 Chapter 6 Proteins 6.1 Protein science and technology 81 6.1 Classification of proteins by source and shape 83 6.2 Protein classification by solubility 83 6.3 Classification and physiological function 84 6.1 The native conformation 84 6.4 Super-secondary structure 90 6.6 Tertiary or globular structure 91 6.4 Stabilization of Protein Structure 92 6.4 Hydrophobic amino acids 93 6.5 Protein hydrophobicity and surface hydrophobicity 93 6.1 Stages of protein hydration and dissolving 95 6.2 Factors affecting protein hydration 95 6.3 Hofmeister model for solute effects 95 6.4 Preferential hydration and exclusion 95 6.1 Definition and significance 97 6.7 Technology of Protein Ingredients 97 6.1 Extraction of proteins from solid sources 97 6.2 Recovery of proteins from liquid sources 97 6.3 Texturization of food industrial proteins 98 6.7 Protein functionality 100 Appendix 6.1 The Osborne extraction 101 Appendix 6.2 Measurement of protein surface hydrophobicity 101 References 101 Chapter 7 Principles of Food Material Science 7.1 Classification of polymers and biopolymers 103 7.2 Kinetics of Free Radical Reactions 104 7.1 Free radical reaction kinetics 104 7.2 Types of initiators 106 7.3 Techniques for free radical polymerization 106 7.1 Introduction and scope 107 7.2 Polymer conformation and tacticity 107 7.3 Polymers as solids 108 7.4 Fringe micelle and lamella models 108 7.4 Order–Disorder Transitions within Materials 109 7.2 Glass transition for amorphous solids 110 7.3 A physical model for the glass transition 111 7.4 Techniques for measuring Tg 112 7.5 Characteristics affecting Tg 112 7.6 Effect of plasticizers on Tg 112 7.5 Biopolymer Conformation and Shape 113 7.6 Solution Tertiary Structure 119 7.1 Random walk model 119 7.2 The equivalent sphere model 120 7.3 The worm-chain-like model (reptation model) 120 7.7 Solid State Tertiary Structure 120 7.8 Techniques in Food Material Science 121 Appendix 7.2 Changes of state 121 References 122 Chapter 8 Principles of Food Rheology 8.1 Significance and scope 123 8.2 Stress–Strain Curves 125 8.3 Solid and Liquid Foods 127 8.4 Measuring the Rheology of Solids 128 8.1 The Instron texture analyzer 128 8.5 Solid and Jelly-Like Foods 131 8.1 Bulk modulus for solids 131 8.2 Modulus of jelly-like foods 132 8.2 Molecular size and intrinsic viscosity 134 8.3 Ionic strength and viscosity 136 8.4 Temperature and viscosity 136 8.5 Effect of concentration on zero-shear viscosity 137 8.6 Effect of shear rate on viscosity 137 8.7 Measuring Viscosity: The Cone Viscometer 138 8.8 Sensory Evaluation of Texture 139 References 139 Chapter 9 Chemistry of Nonenzymic Oxidations 9.2 Significance in foods 141 9.2 Characteristics of Food Oxidation 142 9.2 Thermodynamics of reduction–oxidation reactions 145 9.3 Effect of concentration and pH 146 9.3 Reactive Oxygen Species 146 9.1 Singlet and triplet oxygen 147 9.3 Peroxides and hydroperoxides 148 9.