Food Carbohydrate Chemistry

Not since Sugar Chemistry by Shallenberger and Birch(1975) has a text clearly presented and applied basic carbohydratechemistry to the quality attributes and functional properties offoods. Now in Food Carbohydrate Chemistry, author Wrolstademphasizes the application of carbohydrate chemistry tounderstanding the chemistry, physical and functional properties offood carbohydrates. Structure and nomenclature of sugars and sugarderivatives are covered, focusing on those derivatives that existnaturally in foods or are used as food additives. Chemicalreactions emphasize those that have an impact on food quality andoccur under processing and storage conditions. Coverage includes:how chemical and physical properties of sugars and polysaccharidesaffect the functional properties of foods; taste properties andnon–enzymic browning reactions; the nutritional roles ofcarbohydrates from a food chemist′s perspective; basic principles,advantages, and limitations of selected carbohydrate analyticalmethods. An appendix includes descriptions of proven laboratoryexercises and demonstrations. Applications are emphasized, andanecdotal examples and case studies are presented. Laboratoryunits, homework exercises, and lecture demonstrations are includedin the appendix. In addition to a complete list of citedreferences, a listing of key references is included with briefannotations describing their important features.

Students and professionals alike will benefit from this latestaddition to the IFT Press book series. In FoodCarbohydrate Chemistry, upper undergraduate and graduatestudents will find a clear explanation of how basic principles ofcarbohydrate chemistry can account for and predict functionalproperties such as sweetness, browning potential, and solubilityproperties. Professionals working in product development andtechnical sales will value Food Carbohydrate Chemistry as aneeded resource to help them understand the functionality ofcarbohydrate ingredients. And persons in research and qualityassurance will rely upon Food Carbohydrate Chemistry forunderstanding the principles of carbohydrate analytical methods andthe physical and chemical properties of sugars andpolysaccharides.

Contributors xv

Acknowledgments xvii

Introduction xix

1 Classifying, Identifying, Naming, and Drawing Sugars andSugar Derivatives 1

Structure and Nomenclature of Monosaccharides 2

Aldoses and Ketoses 2

Configurations of Aldose Sugars 3

D– vs. L–Sugars 3

Different Ways of Depicting Sugar Structures 5

Fischer, Haworth, Mills, and Conformational Structures 5

Classifying Sugars by Compound Class Hemiacetals,Hemiketals, Acetals, and Ketals 7

Structure and Nomenclature of Disacchaarides 8

Structure and Optical Activity 10

A Systematic Procedure for Determining Conformation (C–1 or1–C), Chiral Family (D or L), and Anomeric Form (or ) of SugarPyranoid Ring Structures 13

Structure and Nomenclature of Sugar Derivatives with Relevanceto Food Chemistry 14

Glycols (Alditols) 14

Glyconic, Glycuronic, and Glycaric Acids 15

Deoxy Sugars 17

Amino Sugars and Glycosyl Amines 17

Glycosides 18

Sugar Ethers and Sugar Esters 19

Vocabulary 20

References 21

2 Sugar Composition of Foods 23

Introduction 23

Sugar Content of Foods 24

Composition of Sweeteners 24

Cane and Beet Sugar 24

Honey 26

Starch–Derived Sweeteners 27

Inulin Syrup 28

Sugar Composition of Fruits and Fruit Juices 28

Vocabulary 31

References 31

3 Reactions of Sugars 35

Introduction 35

Mutarotation 35

Oxidation of Sugars 39

Glycoside Formation 40

Acid Catalyzed Sugar Reactions 42

Alkaline–Catalyzed Sugar Reactions 43

Summary 45

Vocabulary 47

References 47

4 Browning Reactions 49

Introduction 50

Key Reactions in Maillard Browning 51

Introductory Comments 51

Sugar–Amino Condensation 51

The Amadori and Heyn s Rearrangements 53

Dehydration, Enolization, and Rearrangement Reactions 54

The Strecker Degradation 55

Final Stages: Condensation and Polymerization 58

An Alternate Free–Radical Mechanism for Nonenzymatic Browning58

Measurement of Maillard Browning 59

Control of Maillard Browning 60

Introductory Comments 60

Water Activity 60

The Importance of pH 61

Nature of Reactants 62

Temperature 65

Oxygen 68

Chemical Inhibitors 68

Other Browning Reactions 68

Caramelization 68

Ascorbic Acid Browning 69

Enzymatic Browning 69

Assessing Contributing Factors to Nonenzymatic Browning 70

Vocabulary 72

References 72

5 Functional Properties of Sugars 77

Introduction 77

Taste Properties of Sugars 78

The Shallenberger Acree Theory for Sweetness Perception80

Sugar Solubility 83

Crystallinity of Sugars 85

Hygroscopicity 86

Humectancy 87

Viscosity 87

Freezing Point Depression and Boiling Point Elevation 87

Osmotic Effects 88

Vocabulary 88

References 88

6 Analytical Methods 91

Introduction 91

Physical Methods 92

Refractometry 92

Density 94

Polarimetry 95

Colorimetric Methods 95

Total Sugars by Phenol–Sulfuric Acid 95

Reducing Sugar Methods 96

Chromatographic Methods 96

Paper and Thin–Layer Chromatography 96

Gas Liquid Chromatography 97

HPLC 100

Enzymic Methods 102

Carbon Stable–Isotopic Ratio Analysis (SIRA) 103

References 104

7 Starch in Foods 107

Introduction 108

Sources of Starch 108

Molecular Structure of Starch 109

Starch Granules 112

Gelatinization and Pasting: The Cooking of Starch 113

Retrogradation and Gelation: The Cooling of Cooked Starch115

Monitoring Starch Transitions 118

Microscopy 118

Viscometric Methods 118

Differential Scanning Calorimetry 119

Starch Hydrolytic Enzymes 120

–Amylase 121

–Amylase 122

Modified Starches 122

Physical Modifications 123

Chemical Modifications 125

Resistant Starch 127

Concluding Remarks 129

Vocabulary 129

References 131

8 Plant CellWall Polysaccharides 135

Introduction: Why Plant Cell Walls are Important 135

Cellulose 137

Hemicelluloses 139

Xyloglucans 139

Heteroxylans 140

(1 3),(1 4)––D–Glucans 140

Mannans 141

Pectic Polysaccharides 141

Interactions Between Polysaccharides and Cellulose 143

The Plant Cell Wall Structure 144

Vocabulary 145

References 145

9 Nutritional Roles of Carbohydrates 147

Introduction 147

The Digestive Process: From the Bucchal Cavity through the SmallIntestine 148

Absorption of Sugars 149

Sugar Metabolism 152

The Large Intestine and the Digestive Process 153

The Colon 153

Intestinal Microflora 153

Fate of Nonabsorbed Monosaccharides, Sugar Derivatives, andOligosaccharides 155

Dietary Fiber 158

Carbohydrate Nutrition and Human Health 159

Vocabulary 162

References 163

Appendices 165

Unit 1. Laboratory/Homework Exercise Building MolecularModels of Sugar Molecules 167

Unit 2. Homework Exercise Recognizing Hemiacetal,Hemiketal, Acetal, and Ketal Functional Groups 171

Unit 3. Laboratory/Homework Exercise Specification ofConformation (C–1 or 1–C), Chiral Family (D or L), and AnomericForm (or ) of Sugar Pyranoid Ring Structures 175

Unit 4. Demonstration of the Existence of Plane–Polarized Lightand the Ability of Sugar Solutions to Rotate Plane–Polarized Light181

Unit 5. Laboratory Exercise Sugar Polarimetry 183

Unit 6. Laboratory Exercise or Lecture Demonstration TheFehling s Test for Reducing Sugars 187

Unit 7. Laboratory Exercise Student–Designed MaillardBrowning Experiments 189

Unit 8. Laboratory Exercise or LectureDemonstration Microscopic Examination of Starch 193

Unit 9. Names and Structures of Oligosaccharides 197

Index 211

RONALD E. WROLSTAD, Ph.D. is Distinguished Professor of Food Science & Technology, Emeritus in the Department of Food Science & Technology, Oregon State University, Corvallis, OR. Dr. Wrolstad has authored over 150 professional publications, including 115 papers in refereed journals and 17 books or book chapters. He has served on the editorial boards of numerous scientific journals including Food Chemistry, Journal of Food Processing and Preservation, and Journal of Food Science Education, and has served as chair of the Food Chemistry Division and Fruit & Vegetable Division of the Institute of Food Technologists.