POTATOHANDBOOK The chemical composition of two essential vitamins found in the potato tuber. involved in the formation of connective tissue, the absorption of iron and resistance to diseases in human beings. There are also other antioxidants in potato tubers besides vitamin C. These are flavonoids, polyphenols, chlorogenic acid 1 and various carotenoids, such as zeaxanthin, which is found in orange or dark yellow coloured ‘egg yolk varieties’. Flavonoids are water-soluble anthocyanins, pigments that occur in the skin and the flesh of red, purple and blue tubers. 2 3 4 Other essential vitamins besides C are B6 and B1. In addition to calcium and potassium, the potato is an important source of magnesium. Vitamin B6 is involved in the amino acid metabolism of the immune system and in the proper functioning of the nervous system. The fibres in the potato mainly come from the cell walls and raw fibre or dietary fibres cellulose, hemicellulose and pectin. They represent a small percentage of the tuber weight. More than one fifth of the skin consists of fibres and contains more of these than the flesh of the tuber. Potato fibre contains soluble and insoluble substances and most of them are not digested by human intestines. The daily consumption of a normal serving of potatoes contributes substantially to the daily needs of the most important nutritional components. Potatoes do not contain vitamin A or D, which dairy products do have. So, if these vitamins are combined with vitamins from other products, this will result in a complete meal from the nutritional point of view. To combat malnutrition, infants in Peru in the 1980s received such mixtures of potato and milk powder to supplement the baby food. ● The combination of egg and potato (1) significantly increases the biological value of the two components. Potato and milk (2) have complementary vitamins in food for humans. In Peru, this combination was part of the children’s food programmes in the 1980s. The glycaemic index of the starch-rich potato decreases considerably when it is eaten in combination with fibre-rich lettuce (3). Fish & Chips (4) are also a good combination. Potato World 2019 • number 1 11 Pagina 10
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