Vitamins in foods : analysis, bioavailability, and stability

Part I Properties of Vitamins Chapter 1. Nutritional Aspects of Vitamins 1.1 Definition and Classification of Vitamins .. .. . 3 1.2 Nutritional Vitamin Deficiency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Vitamin Requirements.. .. .. .. .. .. .. .., . .. . . . . . .. .. .. .. .. .. .. . . . . 4 1.4 Vitamin Enhancement of Foods 5 1.5 Stability of Vitamins 6 1.5.1 Water Activity and Lipid Oxidation 6 1.5.2 First-Order Kinetics.. .. .. .. . ... .. .. .. .. .. . .. . .. . .. .. .. .. .. 7 1.5.3 Effects of Food Processing on Vitamin Retention 9 1.5.3.1 Dehydration.. ... .. .. .. .. .. .. .. .. . .. .. . 9 1.5.3.2 Blanching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 1.5.3.3 Canning .. .. .. .. .. .. ... 11 1.5.3.4 Pasteurization and Ultra-High-Temperature Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11 1.5.3.5 Microwave Heating. .. .. .. .. .. .. .. .. .. .. ... .. ... 12 1.5.3.6 Hydrothermal Processes (Flaking, Puffing, and Extrusion) 13 1.5.3.7 Freezing.. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. . .. ... 14 1.5.3.8 Irradiation.. . .. . .. . . . . . .. .. .. .. .. . .. .. .. .. .. .. ... 14 1.5.3.9 High Hydrostatic Pressure Treatment 15 1.5.3.10 Curing and Smoking. . . . . . . . . . . . . . . . . . . . . . . . . . .. 16 1.5.4 Milling... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17 1.5.5 Effects of Food Storage on Vitamin Retention.. ... 17 1.5.6 Effects of Domestic Cooking on Vitamin Retention 17 References 18 Chapter 2. Intestinal Absorption and Bioavailability of Vitamins: Introduction 2.1 General Principles of Solute Translocation. . . . . . . . . . . . . . . . . . . .. 23 2.2 Intestinal Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24 2.2.1 The Villus 24 2.2.2 The Luminal Environment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25 2.2.3 Adaptive Regulation of Intestinal Nutrient Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25 2.2.3.1 Nonspecific Anatomical Adaptations to Changing Metabolic Requirements and Food Deprivation.. .. .. . .. . . .. .. .. " .. .. .. . .. . . ... 25 2.2.3.2 Dietary Regulation of Intestinal Nutrient Carriers.. .. " . .. .. .. .. .. .. .. . . .. .. . . . ... 26 2.2.4 Digestion, Absorption, and Transport of Dietary Fat 27 2.2.5 Transport of Glucose and Fructose: A Model for the Absorption of Some Water-Soluble Vitamins . . . . . . . .. 28 2.2.6 Effects of Dietary Fiber on Absorption of Nutrients " .. .. .. 30 2.3 Bioavailability 32 2.3.1 General Concepts 32 2.3.2 Methods for Estimating Vitamin Bioavailability in Human Subjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33 2.3.2.1 Plasma Response.. .. . .. .. .. .. .. .. .. .. .. . .. .. .. ... 33 2.3.2.2 Urinary Excretion 34 2.3.2.3 Oral-Fecal Balance Studies and the Determination of Prececal Digestibility ... 34 2.3.2.4 Use of Stable Isotopes.. .. .. .. .. .. .. .. .. . .. .. .. ... 35 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Chapter 3. Vitamin A: Retinoids and the Provitamin A Carotenoids 3.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39 3.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40 3.2.1 Structure and Biopotency .. . . .. .. .. .. .. 40 3.2.1.1 Retinol .. .. .. 40 3.2.1.2 Provitamin A Carotenoids 41 3.2.2 Physicochemical Properties .. " .. .. .. 43 3.2.2.1 Appearance and Solubility 43 3.2.2.2 Stability in Nonaqueous Solution 45 3.2.2.2.1 Retinoids .. .. " .. .. 45 3.2.2.2.2 Carotenoids. . . . . . . . . . . . . . . . . . . . . . . . . . .. 45 3.3 Vitamin A in Foods 45 3.3.1 Occurrence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45 3.3.1.1 Vitamin A 46 3.3.1.2 Provitamin A Carotenoids 47 3.3.2 Stability. . . .. " .. .. .. .. .. .. " .. " ... " .. .. " .. .. . '" 48 3.3.2.1 Introduction .. .. ... .. ... 48 3.3.2.2 Vitamin A in Milk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 51 3.3.2.3 Supplemental Vitamin A in Corn Flakes and Rice .. .. .. .. .. .. . .. .. .. .. .. .. .. .. . .. ... 56 3.3.2.4 Provitamin A Carotenoids 57 3.3.3 Vitamin A Equivalency 60 3.3.4 Applicability of Analytical Techniques 61 3.4 Intestinal Absorption, Metabolism, and Transport . . . . . . . . . . . .. 61 3.4.1 Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 62 3.4.2 Metabolic Events Within the Enterocyte . . . . . . . . . . . . . . . . .. 63 3.4.2.1 Esterification of Retinol 63 3.4.2.2 Conversion of Provitamin Carotenoids to Retinoids .. . . . . . . . . . . . . . . . . . . . . . .. 63 3.4.3 Liver Uptake of Chylomicron Remnants and Storage of Vitamin A .. .. .. .. . .. .. .. . .. .. .. .. . .. .. 66 3.4.4 Plasma Transport of Retinol and Carotenoids . . . . . . . . . . .. 66 3.4.5 Tissue Uptake and Metabolism of Retinol . . . . . . . . . . . . . . .. 67 3.5 Bioavailability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67 3.5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67 3.5.2 In vivo Methods of Assessing ~-Carotene Bioavailability ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 68 3.5.2.1 Use of Radioisotopes in Cannulated Patients. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 68 3.5.2.2 Animal Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 69 3.5.2.3 Serum, Plasma, or Chylomicron Responses not Involving Isotopic Tracers 69 3.5.2.4 Methods Involving Stable Isotopes 71 3.5.3 In vitro Methods of Assessing ~-Carotene Bioaccessibility and Bioavailability 74 3.5.3.1 In vitro Digestion Methods to Assess ~-Carotene Bioaccessibility . . . . . . . . . . . . . . . . . . . . . .. 74 3.5.3.2 In vitro Studies of ~-Carotene Absorption Using Caco-2 Cells 76 3.5.4 Host-Related Factors Affecting the Bioavailability of ~-Carotene . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 77 3.5.5 Dietary Factors Affecting the Bioavailability of ~-Carotene 77 3.5.5.1 Location of Carotenoids in the Plant Source . . . .. 77 3.5.5.2 Food Matrix 78 3.5.5.3 Dietary Protein 80 3.5.5.4 Dietary Fat and Energy 81 3.5.5.5 Dietary Fiber 86 3.5.5.6 Plant Sterols 87 3.5.6 Conclusions... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 88 3.6 ~-Carotene Supplementation. . . . . .. . .. .. . . . . . .. .. . . . . . . . . .. ... 88 3.6.1 Effect of Vegetable Consumption on Vitamin A Status in Populations at Risk of Vitamin A Deficiency 88 3.6.2 Effects of f3-Carotene Supplementation on Breastmilk Carotenoids 90 References 92 Chapter 4. Vitamin D 4.1 Background 107 4.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 108 4.2.1 Structure and Biopotency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 108 4.2.2 Physicochemical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 108 4.2.2.1 Appearance and Solubility 108 4.2.2.2 Stability in Nonaqueous Solution 109 4.3 Vitamin D in Foods.. .. .. .. .. ... .. 110 4.3.1 Occurrence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 110 4.3.2 Stability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 112 4.3.3 Expression of Dietary Values 113 4.3.4 Applicability of Analytical Techniques.. .. .. .. .. 113 4.4 Intestinal Absorption, Transport, and Metabolism . . . . . . . . . . .. 114 4.5 Bioavailability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 115 References.. .. .. " .. .. .. " .. .. .. .. .. 116 Chapter 5. Vitamin E 5.1 Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 119 5.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 120 5.2.1 Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 120 5.2.2 Biopotency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 121 5.2.3 Physicochemical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 122 5.2.3.1 Appearance and Solubility 122 5.2.3.2 Stability in Nonaqueous Solution. .. 122 5.2.3.3 In Vitro Antioxidant Activity. . . . . . . . . . . . . . . . . . .. 122 5.3 Vitamin E in Foods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 123 5.3.1 Occurrence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 123 5.3.2 Stability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 126 5.3.3 Expression of Dietary Values 128 5.3.4 Applicability of Analytical Techniques 128 5.4 Intestinal Absorption and Transport. . . . . . . . . . . . . . . . . . . . . . . . .. 128 5.4.1 Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 129 5.4.2 Plasma Transport and Distribution . . . . . . . . . . .. 129 5.4.3 Preferential Secretion of 2R-(X-Tocopherol Stereoisomers by the Liver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 129 5.4.4 Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 130 5.5 Bioavailability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 130 5.5.1 Efficiency of Vitamin E Absorption 130 5.5.2 Effects of Polyunsaturated Fats on Vitamin E Absorption 131 5.5.3 Effects of Dietary Fiber on Vitamin E Absorption 131 5.5.4 Effect of Plant Sterols on Vitamin E Bioavailability .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 132 5.6 Vitamin E Requirements.. .. .. 132 References 132 Chapter 6. Vitamin K 6.1 Background 137 6.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 138 6.2.1 Structure and Biopoter,cy ... . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 138 6.2.2 Physicochemical Properties... .. .. 139 6.2.2.1 Appearance and Solubility 139 6.2.2.2 Stability in Nonaqueous Solution. . . . . . . . . . . . . .. 139 6.3 Vitamin K in Foods .. .. .. ... .. 139 6.3.1 Occurrence.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 139 6.3.2 Stability 141 6.3.2.1 Effects of Hydrogenation... .. ... .. .. .. 142 6.3.3 Applicability of Analytical Techniques. .. .. .. .. .. 142 6.4 Intestinal Absorption and Transport. . . . . . . .. . . . . . . . . . . . . . . . .. 143 6.4.1 Absorption and Transport of Dietary Vitamin K 143 6.4.2 Bacterially Synthesized Menaquinones as a Possible Endogenous Source of Vitamin K... .. .. 143 6.5 Bioavailability. . . .. .. .. .. . . . . . . .. .. . . . . . .. . . . . . . . .. . . . . . . . ... 145 References 146 Chapter 7. Thiamin (Vitamin B1) 7.1 Background 149 7.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 149 7.2.1 Structure and Potency. . . .. . . .. .. .. .. .. .. .. .. .. .. . .. . . 149 7.2.2 Physicochemical Properties... .. .. .. .. ... .. 150 7.2.2.1 Appearance and Solubility 150 7.2.2.2 Stability in Aqueous Solution 150 7.3 Thiamin in Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 151 7.3.1 Occurrence 151 7.3.2 Stability.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 152 7.3.3 Applicability of Analytical Techniques 154 7.4 Intestinal Absorption.. . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. 154 7.5 Bioavailability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 155 7.5.1 Bioavailability of Thiamin in Foods 155 7.5.2 Antithiamin Factors . . . . . . . . . . . . . . . . . . . . . . . . . .. 156 7.5.2.1 Thiaminases. .. . .. .. .. .. .. .. .. .. . .. . ... 156 7.5.2.2 Polyphenols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 157 7.5.3 Effects of Alcohol 159 7.5.4 Effects of Dietary Fiber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 160 References 160 Chapter 8. Flavins: Riboflavin, FMN, and FAD (Vitamin B2) 8.1 Background.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 165 8.2 Chemical Structure, Biopotency, and Physicochemical Properties 165 8.2.1 Structure and Potency.. .. .. .. . .. . .. . .. .. .. .. .. .. . .. . .. ... 165 8.2.2 Physicochemical Properties 167 8.2.2.1 Appearance and Solubility. . . . . . . . . . . . . . . . . . . . .. 167 8.2.2.2 Stability in Aqueous Solution.. .. 167 8.3 Vitamin B2 in Foods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 168 8.3.1 Occurrence 168 8.3.2 Stability .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. 169 8.3.3 Applicability of Analytical Techniques 171 8.4 Intestinal Absorption. . . . . . . .. .. . . . .. .. .. . .. .. " . . . . . .. . . . . .. 171 8.4.1 Absorption of Dietary Vitamin B2 171 8.4.2 Absorption of Bacterially Synthesized Vitamin B2 in the Large Intestine 172 8.5 Bioavailability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 173 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 173 Chapter 9. Niacin 9.1 Background 177 9.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . .. . . . . . . . .. .. . .. . . . . . .. " . . . . . .. .. . . . " . . . .. . .. 178 9.2.1 Structure and Potency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 178 9.2.2 Physicochemical Properties 179 9.2.2.1 Appearance, Solubility, and Other Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 179 9.2.2.2 Stability in Aqueous Solution 179 9.3 Niacin in Foods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 179 9.3.1 Occurrence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 179 9.3.2 Stability. . . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. 181 9.3.3 Applicability of Analytical Techniques 182 9.4 Intestinal Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 183 9.5 Bioavailability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 183 9.5.1 Niacin 183 9.5.2 Tryptophan 187 References . . . .. 187 Chapter 10. Vitamin B6 10.1 Background 189 10.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .. 190 10.2.1 Structure and Potency .. .. .. .. .. .. .. ... .. .. 190 10.2.2 Physicochemical Properties 191 10.2.2.1 Appearance and Solubility 191 10.2.2.2 Stability in Aqueous Solution 192 10.3 Vitamin B6 in Foods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 193 10.3.1 Occurrence. .. .. ... .. .. .. .. .. .. .. .. .. ... .. . . 193 10.3.2 Stability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 194 10.3.3 Applicability of Analytical Techniques. . . . . . . . . . . . . . .. 197 lOA Intestinal Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 198 10.5 Bioavailability 199 10.5.1 Bioavailability of Vitamin B6 in Foods 199 10.5.2 Effects of Alcohol. . . .. . .. .. . . . . .. . . .. . .. . .. . .. .. ... 201 10.5.3 Effects of Dietary Fiber 201 10.504 Glycosylated Forms of Vitamin B6 202 References 205 Chapter 11. Pantothenic Acid 11.1 Background 211 11.2 Chemical Structure, Biopotency, and Physicochemical Properties.. . . . . . . . . . . .. .. . . . .. . . .. . . . . . . .. 211 11.2.1 Structure and Potency .. .. .. .. .. .. .. .. . 211 11.2.2 Physicochemical Properties.. .. . .. .. .. .. .. .. .. .. .. .. ... 212 11.2.2.1 Appearance and Solubility .. .. 212 11.2.2.2 Stability in Aqueous Solution 213 11.3 Pantothenic Acid in Foods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 213 11.3.1 Occurrence 213 11.3.2 Stability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 213 11.3.3 Applicability of Analytical Techniques. . . . . . . . . . . . . . .. 216 11.4 Intestinal Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 216 1104.1 Digestion and Absorption of Dietary Pantothenic Acid. .. .. .. . .. .. .. .. .. .. .. . . .. .. .. .. .. .. ." 216 1104.2 Absorption of Bacterially Synthesized Pantothenic Acid in the Large Intestine 217 11.5 Bioavailability 217 References 218 Chapter 12. Biotin 12.1 Background 221 12.2 Chemical Structure, Biopotency, and Physicochemical Properties. . .. . . . . . . . . . . .. . . . . . . . .. . . . . . . .. 221 12.2.1 Structure and Potency. .. .. .. 221 12.2.2 Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . .. 222 12.2.2.1 Appearance and Solubility 222 12.2.2.2 Stability in Aqueous Solution 223 12.3 Biotin in Foods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 223 12.3.1 Occurrence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 223 12.3.2 Stability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 223 12.3.3 Applicability of Analytical Techniques. . . . . . . . . . . . . . .. 225 12.4 Intestinal Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 226 12.4.1 Digestion and Absorption of Dietary Biotin. . . . . . . . . .. 226 12.4.2 Absorption of Bacterially Synthesized Biotin in the Large Intestine 227 12.5 Bioavailability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 228 References 229 Chapter 13. Folate 13.1 Background 231 13.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 232 13.2.1 Structure and Potency 232 13.2.2 Physicochemical Properties.. .. .. 233 13.2.2.1 Appearance, Solubility, and Ionic Characteristics 233 13.2.2.2 Stability in Aqueous Solution 234 13.3 Folate in Foods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 236 13.3.1 Occurrence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 236 13.3.2 Stability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 238 13.3.3 Applicability of Analytical Techniques. . . . . . . . . . . . . . .. 244 13.4 Absorption, Transport, and Metabolism. . . . . . . . . . . . . . . . . . . .. 245 13.4.1 Deconjugation of Polyglutamyl Folate 245 13.4.2 Absorption of Dietary Folate 246 13.4.3 Influence of Folate-Binding Protein on the Absorption of Folate from Milk 247 13.4.4 Adaptive Regulation of Folate Absorption. . . . . . . . . . .. 249 13.4.5 Salvage of Dietary 5-Methyl-5,6-DHF 249 13.4.6 Absorption of Bacterially Synthesized Folate in the Large Intestine .. .. .. .. . .. . .. .. .. .. .. . .. 250 13.4.7 Plasma Transport and Intracellular Metabolism 251 13.4.8 Folate Homeostasis 251 13.5 Bioavailability . .. . . . .. .. . . . .. .. . . . .. .. . .. ... 252 13.5.1 Introduction.. .. .. .. .. .. ... .. .. .. .. .. .. .. .. '" 252 13.5.2 Methods for Assessing Folate Bioavailability 252 13.5.2.1 Plasma Response 252 13.5.2.2 Stable-Isotopic Methods.. .. .. 253 13.5.2.3 Use of Ileostomy Subjects 255 13.5.3 Inherent Bioavailability of Monoglutamyl and Polyglutamyl Folates 256 13.5.4 Bioavailability of Naturally Occurring Folate in Fruits and Vegetables.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 257 13.5.5 Bioavailability of Folate in Milk . . . . . . . . . . . . . . . . . .. 258 13.5.6 Effects of Soluble Food Components on Folate Bioavailability 260 13.5.7 Effects of Dietary Fiber on Folate Bioavailability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 262 13.5.8 Bioavailability of Folate in Fortified Foods. . . . . . . . . . .. 263 13.5.9 Effects of Alcohol on Folate Status .. 264 References 264 Chapter 14. Vitamin B12 (Cobalamins) 14.1 Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 275 14.2 Chemical Structure, Biopotency, and Physicochemical Properties. '" .. ... 276 14.2.1 Structure and Potency. .. " . . .. .. .. ... . . .. .. .. .. .. .. ... 276 14.2.2 Physicochemical Properties.. .. .. ... .. .. .. . . .. ... 277 14.2.2.1 Appearance and Solubility 277 14.2.2.2 Stability in Aqueous Solution 278 14.3 Vitamin B12in Foods .. .. 278 14.3.1 Occurrence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 278 14.3.2 Stability 279 14.3.3 Applicability of Analytical Techniques 281 14.4 Absorption and Conservation.. .. 281 14.4.1 Digestion and Absorption of Dietary Vitamin B12 282 14.4.2 Conservation of Vitamin B12. .. .. .. ... .. .. .. 283 14.5 Bioavailability . . . . .. .. .. . .. .. . .. . . .. .. . .. . . . . . .. . . . . .. 283 14.5.1 Efficiency of Absorption. .. ., .. .. .. .. ... .. .. ... 283 14.5.2 Bioavailability Studies. .. 284 14.5.2.1 Effects of Dietary Fiber 284 14.5.2.2 Effects of Alcohol 284 14.5.2.3 Effects of Smoking . . . . . . . . . . . . . . . . . . . . . . . . . .. 285 References 285 Chapter 15. Vitamin C 15.1 Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 289 15.2 Chemical Structure, Biopotency, and Physicochemical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 290 15.2.1 Structure and Potency... .. .. .. .. .. .. .. .. . .. .. .. ... 290 15.2.2 Physicochemical Properties .. .. . .. ... 291 15.2.2.1 Solubility and Other Properties 291 15.2.2.2 Stability in Aqueous Solution 292 15.3 Vitamin C in Foods.. ... .. .. .. 292 15.3.1 Occurrence . .. . . .., .. . . .. .. .. .. .. . . . . . .. . . .. .. . .. 292 15.3.2 Stability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 294 15.3.3 Applicability of Analytical Techniques. . . . . . . . . . . . . . .. 299 15.4 Intestinal Absorption. . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. 300 15.4.1 General Principles 300 15.4.2 Transport Mechanisms 301 15.4.2.1 Ascorbic Acid.. .. .. .. .. .. ... 301 15.4.2.2 Dehydroascorbic Acid 302 15.4.3 Efficiency of Ascorbate Absorption in Humans .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 302 15.5 Bioavailability .. . .. .. . .. .. .. .. .. 303 15.5.1 Bioavailability of Vitamin C in Foods 303 15.5.2 Effects of Dietary Fiber 304 15.5.3 Effects of Alcohol .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 305 References 305 Part II Analysis of Vitamins Chapter 16. Analytical Considerations 16.1 Bioassays. . . . . . . . . .. . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 311 16.2 In Vitro Analytical Techniques. . . . . . . . .. . . . .. . . . . . . . ., . . . . .. 312 16.3 Analytical Approach. .. .. .. . . . . . .. . .. . . . . .. . .. . . . .. .. . .. . .. 312 16.4 Preparation of Sample Extracts for Analysis. . . . . . . .. .. . . . . .. 313 16.4.1 Extraction. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... 314 16.4.2 Cleanup 314 16.5 Method Evaluation... .. 314 16.5.1 Measurement Value and Uncertainty 314 16.5.2 Quality Assurance. .. .. .. .. .. .. .. .. ... 316 16.5.3 Food Reference Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 316 16.5.4 Method Validation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 318 References 320 Chapter 17. Extraction Techniques for the Water-Soluble Vitamins 17.1 Vitamin B1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 321 17.2 Vitamin B2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 322 17.3 Niacin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 323 17.4 Vitamin B6' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 326 17.5 Pantothenic Acid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 328 17.6 Biotin 328 17.7 Folate 329 17.8 Vitamin B12 . . . . . . . . . . .. . . . . . ., . . . . . .. . . . . . . . . . . . . . . . . . . . . .. 331 17.9 Vitamin C. . . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 332 References . . . . . . . .. 333 Chapter 18. Microbiological Methods for the Determination of the B-Group Vitamins 18.1 Introduction 339 18.2 General Principles. . . . .. .. . ., .. . . . . . .. . . . . . . . . . . . . . . . . . . . . .. 339 18.2.1 Turbidimetric Methods 339 18.2.2 Methods Based on the Measurement of Metabolic Carbon Dioxide .. .. .. .. .. .. .. .. .. .. ... 341 18.3 Conventional Turbidimetric Method Using Test Tubes. . .. . ., 342 18.3.1 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 342 18.3.2 Laboratory Facilities and Cleaning of Glassware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 343 18.3.3 Media... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 344 18.3.4 General Assay Procedure.. .. .. . .. .. .. .. .. .. .. . . .. .. . .. 344 18.3.4.1 Maintenance of Stock Cultures . . . . . . . . . . . . .. 345 18.3.4.2 Preparation of the Inoculum Culture. . . . . . .. 346 18.3.4.3 Preparation of the Assay (Basal) Medium. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 347 18.3.4.4 Extraction of the Vitamin from the Test Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 348 18.3.4.5 Setting Up the Assay 348 18.3.4.6 Quantification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 349 18.3.5 Partial Automation of the Assay Procedure 350 18.4 Turbidimetric Method Using Microtiter Plates... .. ., ... 350 18.5 Assays of Individual B-Group Vitamins. . . . . . . . . . . . . . . . . . . .. 351 18.5.1 Vitamin B1 351 18.5.2 Vitamin B2 352 18.5.3 Niacin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 354 18.5.3.1 Determination of Total Niacin 354 18.5.3.2 Determination of Bound Nicotinic Acid. . . .. 355 18.5.3.3 Determination of Added Nicotinic Acid 356 18.5.4 Vitamin B6 356 18.5.5 Pantothenic Acid 359 18.5.6 Biotin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 360 18.5.7 Folate 360 18.5.8 Vitamin B12 361 References 363 Chapter 19. Physicochemical Analytical Techniques (Excluding HPLC) 19.1 AOAC Titrimetric Method for Vitamin C. . . . . . .. . . . .. . . . . . .. 369 19.2 Direct Spectrophotometric Determination of Vitamin C 372 19.3 Colorimetric Methods for Niacin and Vitamin C .. 373 19.3.1 Determination of Niacin by the Konig Reaction (AOAC Method) 373 19.3.2 Colorimetric Methods for Vitamin C . . . . . . . . . . . . . . . . .. 374 19.4 Fluorometric Methods for Thiamin, Riboflavin, Vitamin B6' and Vitamin C 375 19.4.1 Thiamin (AOAC Method) 375 19.4.2 Riboflavin (AOAC Method) 375 19.4.3 Vitamin B6 376 19.4.4 Vitamin C (AOAC Method) 377 19.5 Enzymatic Methods for Nicotinic Acid and Ascorbic Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 378 19.5.1 Nicotinic Acid 378 19.5.2 Ascorbic Acid.. " .. . . . .. . . .. ... . .. . 379 19.6 Continuous-Flow Analysis. .. ... .. .. 380 19.6.1 Segmented-Flow Methods .. .. 380 19.6.2 Flow-Injection Analysis. .. " .. .. " . .. .. .. .. 380 19.6.3 Applications to Food Analysis 381 19.6.3.1 Fat-Soluble Vitamins.. . .. .. .. . . .. .. .. 381 19.6.3.2 Thiamin 381 19.6.3.3 Riboflavin . .. .. .. . ... .. 382 19.6.3.4 Thiamin and Riboflavin Simultaneously 382 19.6.3.5 Niacin. .. .. .. '" ... . .. . ... 382 19.6.3.6 Vitamin C 383 19.7 Gas Chromatography '" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 385 19.7.1 Principle... 385 19.7.2 Column Technology. . .. .. .. 385 19.7.3 Detectors. .. .. .. .. .. .. .. .. .. 386 19.7.4 Derivatization Techniques.. .. 386 19.7.5 Quantification 387 19.7.6 Applications to Food Analysis 387 19.7.6.1 Vitamin E 387 19.7.6.2 Thiamin 388 19.7.6.3 Niacin. .. .. '" .. .. .. .. 388 19.7.6.4 Vitamin B6 388 19.7.6.5 Pantothenic Acid 389 19.8 Supercritical Fluid Chromatography. . . .. . . . . . .. . . . . . .. . . . .. 390 19.8.1 Principle 390 19.8.2 Instrumentation . . . ... . . ... .. .. .. .. .. .. . " . '" .. 391 19.8.3 Columns 393 19.8.4 Applications to Food Analysis 394 19.9 Capillary Electrophoresis. . . . . ., . . . . . . . . . . . . .. . . . .. . . . . . . . .. 394 19.9.1 Principle .. .. 394 19.9.2 Capillary Zone Electrophoresis .. .. .. .. 396 19.9.3 Micellar Electrokinetic Capillary Chromatography. .. 396 19.9.4 Operational Aspects.. .. .., . .. .. .. .. .. .. 397 19.9.5 Applications to Food Analysis 399 19.9.5.1 Thiamin 399 19.9.5.2 Riboflavin, FMN, and FAD 399 19.9.5.3 Niacin .. .. .. .. .. .. . . .. 406 19.9.5.4 Vitamin C .. .. 408 References 409 Chapter 20. Determination of the Fat-Soluble Vitamins by HPLC 20.1 Nature of the Sample. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 419 20.2 Extraction Procedures. .. 419 20.2.1 Alkaline Hydrolysis (Saponification) .. .. 419 20.2.1.1 Vitamin A .. 421 20.2.1.2 Carotenoids 422 20.2.1.3 Vitamin D . .. .. .. .. 422 20.2.1.4 Vitamin E 423 Alcoholysis 424 Enzymatic Hydrolysis 424 Direct Solvent Extraction 425 20.2.4.1 Vitamin A and Carotene. . . . . . . . . . . . . . . . . . . .. 426 20.2.4.2 Carotenoids.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 427 20.2.4.3 Vitamin D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 427 20.2.4.4 Vitamin E 428 20.2.4.5 Vitamin K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 428 20.2.5 Matrix Solid-Phase Dispersion .. .. 429 20.2.6 Supercritical Fluid Extraction. . . . . . . . . . . . . . . . . . . . . . . . .. 430 20.2.6.1 Principle.. .. ... .. .. .. .. .. .. .. .. .. 430 20.2.6.2 Instrumentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 430 20.2.6.3 Applications .. .. .. .. .. 431 20.3 Cleanup Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 435 20.3.1 Precipitation of Sterols.. .. .. .. .. .. .. . .. .. .. .. .. .. 436 20.3.2 Open-Column Chromatography 436 20.3.2.1 Magnesia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 436 20.3.2.2 Alumina. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 436 20.3.2.3 Silica Gel .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 437 20.3.3 Solid-Phase Extraction.. .. .. .. .. . . .. .. .. . .. .. .. .. .. 437 20.3.3.1 General Considerations .. 437 20.3.3.2 Application in Vitamin D Determinations .. 438 20.2.2 20.2.3 20.2.4 20.4 HPLC Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 439 20.4.1 Principle .. .. .. 439 20.4.2 Explanations of Chromatographic Terms 440 20.4.2.1 Retention.. .. '" . . " .. .. .. .. .. " .. .. .. 440 20.4.2.2 Separation..