Abstract
Contents of total vitamin C (ascorbic acid and dehydroascorbic acid) of potatoes harvested in the spring and autumn were 19. 3 and 18. 8 mg%, respectively, and decreased during the storage. The decrease in the total vitamin C content was drastic during 1-to 2-month storage, and the content after 2-month storage was less than a half of the content of fresh potatoes. A positive correlation between the decrease in the total vitamin C content and the budding during storage was not observed. It was demonstrated by using three different assay methods that ascorbic acid content of potatoes increased after slicing. The maximum content of vitamin C was observed in potato slices after 2 days. Ascorbic acid content of potatoes decreased gradually during roasting and microwave heating depending on the heating time, however, in the case of steaming and boiling the content decreased within 10-min heating and the content was maintained thereafter. Remaining total vitamin C content after cooking in the optimal heating time was highest in the microwave-heated potatoes (96 %), intermediate in the steamed and roasted potatoes (67 and 62 %), and lowest in the boiled ones (28 %). Residual content of total vitamin C of potatoes cooked as a whole was higher than that of cooked after cutting. Total vitamin C content of frozen fried potatoes commercially available was varied from 4 to 18 mg%.
