ASCORBIC-ACID IN EXOTIC FRUITS - A LIQUID-CHROMATOGRAPHIC INVESTIGATION

The levels of ascorbic acid (AA) have been measured by means of an HPLC method in 11 different exotic fruits (avocado pear, babaco, feijoa, grapefruit, kiwi, kumquat, litchi, mango, papaya, passion fruit, pineapple) and, for comparative purposes, in two citrus fruits (lemon and orange). They were measured in the exotic fruits at two different stages of ripening: (i) immediately after purchasing from a local fresh fruit market, and (ii) after a one-week period of artificial ripening. The results show that all tropical fruits contain relatively high levels of AA (varying between 20 and 90 mg/100g), with the exceptions of avocado pear and feijoa (whose AA levels are markedly affected by oxidation processes). Moreover, the results show that there is a remarkable loss of AA content (usually 30-40%) after the one-week period of artificial ripening, in all the different tropical fruits considered. They seem to indicate that the process of artificial ripening, which is usually carried out during the short-term storage of exotic fruits, can affect the nutritional value of this kind of food as far as the concentration of the reduced form of vitamin C is concerned.