Vitamins are defined as a diverse group of food-based essential organic substances (relatively small molecules but comparable in size to amino acids or sugars) that are not synthesized by the human body, but by plants and microorganisms. Therefore, vitamins are nutritionally essential micronutrient for humans and function in vivo in several ways, including: (1) as coenzymes or their precursors (niacin, thiamin, riboflavin, biotin, pantothenic acid, vitamin B6, vitamin B12, and foliate); (2) in specialized functions such as vitamin A in vision and ascorbate in distinct hydroxylation reactions; and (3) as components of the antioxidative defense systems (vitamins C and E and some carotenoids), and as factors involved in human genetic regulation and genomic stability (folic acid, vitamin B12, vitamin B6, niacin, vitamin C, vitamin E, and vitamin D) (Table 5.2) (5,6,42).
Vitamins present in a food source, once taken up by the body, are dissolved either in water or fat (37,42). As a consequence vitamins are classified on the basis of their solubility as water-soluble or fat-soluble vitamins. Vitamins and the chemical structures of each group are presented in Figures 5.1 and 5.2.
The term carotenoids summarizes a class of structurally related compounds, which are mainly found in plants, algae, and several lower organisms, bacteria, and fungi. At present, more than 600 different carotenoids have been identified (72). Saffron, pepper, leaves, and red palm oil possessing carotenoids as their main color components, have been exploited as food colors for several centuries. The color of carotenoids, together with beneficial properties such as vitamin A precursor and antioxidant activity, has led to their wide application in the food industry. They have been used for pigmentation of margarine, butter, fruit juices and
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