The vitamin C content of different types of fruits ranges between some thousands of milligrams per 100 g in the instance of the West Indian cherry (acerola/Barbados cherry, Malpighia punificolia) to a few milligrams in apples (species of Malus sylves-tris) and pears (varieties of Pyrus communis). The yellow-orange colored fruits (e.g., apricots, Prunus armeniaca, pawpaw, Carica papaya) supply carotene, as also do all green vegetables, while it is absent from white types. Leafy vegetables are rich sources of vitamin K and many fruits and vegetables are significant sources of folate.
Growing conditions including soil, fertilizer (type, amount, and time of application) and the state of maturity influence the vitamin content, particularly of vitamin C. In some foods, such as citrus fruits and tomato, the vitamin C is influenced by exposure to sunshine. One further cause of variation in vitamin content, again applying particularly to vitamin C and to a lesser extent to folate, is the loss after cropping, particularly from leaves that are bruised or wilted. Consequently it is not possible, apart from very broad generalizations, to state the vitamin content of a particular fruit or vegetable. Furthermore, new varieties have been and are being developed that are particularly rich in some vitamins.
Comparisons between food composition tables from various national authorities are unrealistic. Thus among six such tables (Australia, Germany, Great Britain, Spain, Italy, and the USA) the range of carotene in pumpkins is quoted from 0.24 to 19mgper100g; for thiamin between 0.15 and 0.5 mg per 100 g; and for vitamin C between 10 and 50mgper100g. For tomato the carotene ranges between 0.8 and 4mgper 100 g. Even within one set of tables, in which the same sampling and analytical techniques are presumably used, there is a range of carotene in sweet potatoes (Ipomea batatas) from 0.3 to 4.6mgper 100g; and for lettuce (Lactuca sativa) from 0.16 to 1.6 mg per 100 g.
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