ABSTRACT
Vitamins are organic substances, present in minute amounts fanatural foodstuffs, which are essential for normal metabolism. Their lack in the diet causes deficiency diseases. Vegetables and fruits are the major source of ascorbic acid for human nutrition. The data of Karmas published in 1988, however, indicate that the shares of citrus fruits, potato, and sweet potato have undergone some changes so that these two food groups provided 29.8 and 13.5% of the total vitamin C in the diet of US consumers. Vitamins are differently sensitive to destruction by heat, light, oxygen, and the pH of the medium they are kept in. Carotenoids account for the yellow, orange, or red color of maize, carrot, tomato, mango, sweet potato, apricot, and many other plant products. They frequently occur along with chlorophyll in all green plant tissues, and thus leafy vegetables such as spinach, are good sources of carotenes, although in these plants the color of carotenes is masked by the chlorophyll molecules.
