Food chemistry

Logically organized according to food constituents and commodities and extensively illustrated with more than 450 tables and 340 figures this completely revised and updated edition provides students and researcher in food science or agricultural chemistry with an outstanding textbook. The extensive use of tables for easy reference, the wealth of information given, and the comprehensive subject index will help this volume serve as a reference text for advanced students in food technology and as a valuable on-the-job reference for chemists, engineers, biochemists, nutritionists, and analytical chemists in food industry and in research as well as in food control and other service labs.

0 Water 1
0.1 Foreword 1
0.2 Structure 1
0.2.1 Water Molecule 1
0.2.2 Liquid Water and Ice 2
0.3 Effect on Storage Life 3
0.3.1 Water Activity 3
0.3.2 Water Activity as an Indicator 5
0.3.3 Phase Transition of Foods Containing Water 5
0.3.4 WLF Equation 6
0.3.5 Conclusion 7
0.4 Literature 7
1 Amino Acids, Peptides, Proteins 8
1.1 Foreword 8
1.2 Amino Acids 9
1.2.1 General Remarks 9
1.2.2 Classification, Discovery and Occurrence 9
1.2.2.1 Classification 9
1.2.2.2 Discovery and Occurrence 11
1.2.3 Physical Properties 12
1.2.3.1 Dissociation 12
1.2.3.2 Configuration and Optical Activity 14
1.2.3.3 Solubility 15
1.2.3.4 UV Absorption 15
1.2.4 Chemical Reactions 16
1.2.4.1 Esterification of Carboxyl Groups 16
1.2.4.2 Reactions of Amino Groups 17
1.2.4.2.1 Acylation 17
1.2.4.2.2 Alkylation and Arylation 18
1.2.4.2.3 Carbamoyl and Thiocarbamoyl Derivatives 21
1.2.4.2.4 Reactions with Carbonyl Compounds 21
1.2.4.3 Reactions Involving Other Functional Groups 23
1.2.4.3.1 Lysine 23
1.2.4.3.2 Arginine 23
1.2.4.3.3 Aspartic and Glutamic Acids 24
1.2.4.3.4 Serine and Threonine 24
1.2.4.3.5 Cysteine and Cystine 24
1.2.4.3.6 Methionine 25
1.2.4.3.7 Tyrosine 25
1.2.4.4 Reactions of Amino Acids at Higher Temperatures 25
1.2.5 Synthetic Amino Acids Utilized for to Increasing the Biological
Value of Food (Food Fortification) 29
1.2.5.1 Glutamic Acid 31
1.2.5.2 Aspartic Acid 31
1.2.5.3 Lysine 31
1.2.5.4 Methionine 31
1.2.5.5 Phenylalanine 33
1.2.5.6 Threonine 33
1.2.5.7 Tryptophan 33
1.2.6 Sensory Properties 33
1.3 Peptides 34
1.3.1 General Remarks, Nomenclature 34
1.3.2 Physical Properties 35
1.3.2.1 Dissociation 35
1.3.3 Sensory Properties 35
1.3.4 Individual Peptides 37
1.3.4.1 Glutathione 37
1.3.4.2 Carnosine, Anserine and Balenine 38
1.3.4.3 Nisin 38
1.3.4.4 Lysine Peptides 39
1.3.4.5 Other Peptides 39
1.4 Proteins 39
1.4.1 Amino Acid Sequence 40
1.4.1.1 Amino Acid Composition, Subunits 40
1.4.1.2 Terminal Groups 41
1.4.1.3 Partial Hydrolysis 42
1.4.1.4 Sequence Analysis 43
1.4.1.5 Derivation of Amino Acid Sequence from the Nucleotide
Sequence of the Coding Gene 45
1.4.2 Conformation 48
1.4.2.1 Extended Peptide Chains 48
1.4.2.2 Secondary Structure (Regular Structural Elements) 49
1.4.2.2.1 beta-Sheet 50
1.4.2.2.2 Helical Structures 51
1.4.2.2.3 Reverse Turns 52
1.4.2.2.4 Super-Secondary Structures 53
1.4.2.3 Tertiary and Quaternary Structures 53
1.4.2.3.1 Fibrous Proteins 53
1.4.2.3.2 Globular Proteins 53
1.4.2.3.3 Quaternary Structures 56
1.4.2.4 Denaturation 56
1.4.3 Physical Properties 58
1.4.3.1 Dissociation 58
1.4.3.2 Optical Activity 60
1.4.3.3 Solubility, Hydration and Swelling Power 60
1.4.3.4 Foam Formation and Foam Stabilization 61
1.4.3.5 Gel Formation 62
1.4.3.6 Emulsifying Effect 63
1.4.4 Chemical Reactions 63
1.4.4.1 Lysine Residue 63
1.4.4.1.1 Reactions Which Retain the Positive Charge 64
1.4.4.1.2 Reactions Resulting in a Loss of Positive Charge 64
1.4.4.1.3 Reactions Resulting in a Negative Charge 65
1.4.4.1.4 Reversible Reactions 65
1.4.4.2 Arginine Residue 66
1.4.4.3 Glutamic and Aspartic Acid Residues 66
1.4.4.4 Cystine Residue 67
1.4.4.5 Cysteine Residue 68
1.4.4.6 Methionine Residue 69
1.4.4.7 Histidine Residue 69
1.4.4.8 Tryptophan Residue 69
1.4.4.9 Tyrosine Residue 69
1.4.4.10 Bifunctional Reagents 70
1.4.4.11 Reactions Involved in Food Processing 70
1.4.5 Enzyme-Catalyzed Reactions 74
1.4.5.1 Foreword 74
1.4.5.2 Proteolytic Enzymes 74
1.4.5.2.1 Serine Peptidases 75
1.4.5.2.2 Cysteine Peptidases 76
1.4.5.2.3 Metalo Peptidases 76
1.4.5.2.4 Aspartic Peptidases 78
1.4.6 Chemical and Enzymatic Reactions of Interest to Food Processing 79
1.4.6.1 Foreword 79
1.4.6.2 Chemical Modification 79
1.4.6.2.1 Acylation 80
1.4.6.2.2 Alkylation 82
1.4.6.2.3 Redox Reactions Involving Cysteine and Cystine 82
1.4.6.3 Enzymatic Modification 82
1.4.6.3.1 Dephosphorylation 82
1.4.6.3.2 Plastein Reaction 83
1.4.6.3.3 Associations Involving Cross-Linking 86
1.4.7 Texturized Proteins 87
1.4.7.1 Foreword 87
1.4.7.2 Starting Material 87
1.4.7.3 Texturization 87
1.4.7.3.1 Spin Process 88
1.4.7.3.2 Extrusion Process 88
1.5 Literature 88
2 Enzymes 92
2.1 Foreword 92
2.2 General Remarks, Isolation and Nomenclature 92
2.2.1 Catalysis 92
2.2.2 Specificity 93
2.2.2.1 Substrate Specificity 93
2.2.2.2 Reaction Specificity 94
2.2.3 Structure 94
2.2.4 Isolation and Purification 94
2.2.5 Multiple Forms of Enzymes 96
2.2.6 Nomenclature 96
2.2.7 Activity Units 97
2.3 Enzyme Cofactors 97
2.3.1 Cosubstrates 100
2.3.1.1 Nicotinamide Adenine Dinucleotide 100
2.3.1.2 Adenosine Triphosphate 100
2.3.2 Prosthetic Groups 101
2.3.2.1 Flavins 101
2.3.2.2 Hemin 102
2.3.2.3 Pyridoxal Phosphate 102
2.3.3 Metal Ions 103
2.3.3.1 Magnesium, Calcium and Zinc 103
2.3.3.2 Iron, Copper and Molybdenum 104
2.4 Theory of Enzyme Catalysis 105
2.4.1 Active Site 106
2.4.1.1 Active Site Localization 106
2.4.1.2 Substrate Binding 107
2.4.1.2.1 Stereospecificity 107
2.4.1.2.2 "Lock and Key" Hypothesis 108
2.4.1.2.3 Induced-fit Model 109
2.4.2 Reasons for Catalytic Activity 110
2.4.2.1 Steric Effects ­ Orientation Effects 110
2.4.2.2 Structural Complementarity to Transition State 111
2.4.2.3 Entropy Effect 111
2.4.2.4 General Acid-Base Catalysis 112
2.4.2.5 Covalent Catalysis 114
2.4.3 Closing Remarks 117
2.5 Kinetics of Enzyme-Catalyzed Reactions 117
2.5.1 Effect of Substrate Concentration 117
2.5.1.1 Single-Substrate Reactions 117
2.5.1.1.1 Michaelis-Menten Equation 117
2.5.1.1.2 Determination of K_m and V 120
2.5.1.2 Two-Substrate Reactions 121
2.5.1.2.1 Order of Substrate Binding 121
2.5.1.2.2 Rate Equations for a Two-Substrate Reaction 122
2.5.1.3 Allosteric Enzymes 124
2.5.2 Effect of Inhibitors 125
2.5.2.1 Irreversible Inhibition 126
2.5.2.2 Reversible Inhibition 126
2.5.2.2.1 Competitive Inhibition 126
2.5.2.2.2 Non-Competitive Inhibition 127
2.5.2.2.3 Uncompetitive Inhibition 127
2.5.3 Effect of pH on Enzyme Activity 128
2.5.4 Influence of Temperature 130
2.5.4.1 Time Dependence of Effects 131
2.5.4.2 Temperature Dependence of Effects 131
2.5.4.3 Temperature Optimum 133
2.5.4.4 Thermal Stability 134
2.5.5 Influence of Water 136
2.6 Enzymatic Analysis 136
2.6.1 Substrate Determination 136
2.6.1.1 Principles 136
2.6.1.2 End-Point Method 138
2.6.1.3 Kinetic Method 139
2.6.2 Determination of Enzyme Activity 139
2.6.3 Enzyme Immunoassay 140
2.7 Enzyme Utilization in the Food Industry 141
2.7.1 Technical Enzyme Preparations 141
2.7.1.1 Production 141
2.7.1.2 Immobilized Enzymes 141
2.7.1.2.1 Bound Enzymes 141
2.7.1.2.2 Enzyme Entrapment 143
2.7.1.2.3 Cross-Linked Enzymes 144
2.7.1.2.4 Properties 144
2.7.2 Individual Enzymes 145
2.7.2.1 Oxidoreductases 145
2.7.2.1.1 Glucose Oxidase 145
2.7.2.1.2 Catalase 145
2.7.2.1.3 Lipoxygenase 145
2.7.2.1.4 Aldehyde Dehydrogenase 145
2.7.2.1.5 Butanediol Dehydrogenase 145
2.7.2.2 Hydrolases 146
2.7.2.2.1 Proteinases 146
2.7.2.2.2 alpha- and beta-Amylases 147
2.7.2.2.3 Glucan-1,4-alpha-D-Glucosidase (Glucoamylase) 147
2.7.2.2.4 Pullulanase (Isoamylase) 148
2.7.2.2.5 Endo-1,3(4)-beta-D-Glucanase 148
2.7.2.2.6 alpha-D-Galactosidase 148
2.7.2.2.7 beta-D-Galactosidase (Lactase) 148
2.7.2.2.8 beta-D-Fructofuranosidase (Invertase) 148
2.7.2.2.9 alpha-L-Rhamnosidase 148
2.7.2.2.10 Cellulases and Hemicellulases 148
2.7.2.2.11 Lysozyme 149
2.7.2.2.12 Thioglucosidase 149
2.7.2.2.13 Pectolytic Enzymes 149
2.7.2.2.14 Lipases 149
2.7.2.2.15 Tannases 150
2.7.2.3 Isomerases 150
2.8 Literature 150
3 Lipids 152
3.1 Foreword 152
3.2 Fatty Acids 153
3.2.1 Nomenclature and Classification 153
3.2.1.1 Saturated Fatty Acids 153
3.2.1.2 Unsaturated Fatty Acids 154
3.2.1.3 Substituted Fatty Acids 157
3.2.2 Physical Properties 158
3.2.2.1 Carboxyl Group 158
3.2.2.2 Crystalline Structure, Melting Points 158
3.2.2.3 Urea Adducts 160
3.2.2.4 Solubility 160
3.2.2.5 UV-Absorption 160
3.2.3 Chemical Properties 161
3.2.3.1 Methylation of Carboxyl Groups 161
3.2.3.2 Reactions of Unsaturated Fatty Acids 161
3.2.3.2.1 Halogen Addition Reactions 161
3.2.3.2.2 Transformation of Isolene-Type Fatty Acids to Conjugated Fatty Acids 161
3.2.3.2.3 Formation of a pi-Complex with Ag^+ Ions 162
3.2.3.2.4 Hydrogenation 162
3.2.4 Biosynthesis of Unsaturated Fatty Acids 162
3.3 Acylglycerols 163
3.3.1 Triacylglycerols (TG) 163