Abstract
Contents of vitamin C in sweet potatoes cooked by steaming, electronic range and roasting were compared with that of the raw sweet patato according to 2, 4-dinitrophenylhydrazine method. It was observed that residual content of vitamin C in the roasted sweet potato depended on the temperature and heating time during the process of cooking. The cooking of sweet potato by roasting gave more degradation of vitamin C, when the potato was heated slowly and kept at 60 to 70°C for 10 to 15 min. While, the cooking of sweet potatoes by the electronic range and steaming gave no degradation, as a result that the heating time of sweet potato was short and that the temperature in the sweet potato reached rapidly at 100°C
Accordingly, it seemed that the tissue of sweet potato may be damaged by slow heating, following the oxidation with the vitamin C oxidase.
