مقاومت و پایداری ویتامین ث در برخی میوه‌ها در شرایط مختلف نگهداری

ABSTRACT There is some evidence showing that vitamin C is destroyed by different factors such as heat ,air, light and mechanical pressure Ascorbic acid oxidizing enzyme, once exposed to air,becomes activated and oxidize vitamin C.This enzyme, however becomes inactivated by heat specially in vicinity of iron and copper and once exposed to an alkalin environment .Since vitamin C is water solouble , juicy fruits lose their vitamin C content in the lapse of time. In the present study ,vitamin C content of some types of fruits available in the country was assessed while the samples were preserved for a period of 2 months at zero and 15 degrees centigrade respectively during which vitamin C content of the Samples was assessed at regular intervals . Results of the study showed that generally ,vitamin C content of all the studied fruits had reduced by the lapse of time and this reduction was more conspicuous in 15 C compared to 0 (the correlation coefficient between days of study and vitamin C content of fruits in all samples was less than 0.87 and was significant at 0.01 level). Change of vitamin C in different fruits was varied in a way that, for example in the last day of study the vitamin C content of pomegranate was nil while in orange this amount was only 10% of the original amount of vitamin which had been present in the sample in the first day of study In quince ,vitamin C reduction was the same either in zero or 15^C and less compared with other fruits .The reason may be that this fruit contains less water and ascorbic acid oxidase enzyme (A.A.O.) compared with other fruits Therefore it is more resistant against the destructive factors