Abstract
It was observed that the ascorbic acid residue in the cooked sweet potato depended on the degree of destruction of intracellular structure and residual ascorbate oxidase activities in the heating sample.
It was supposed that, in the heating process of sweet potatoes, following the destruction of intracellular structure the ascorbic acid was oxidized by ascorbate oxidase located in the cells. Accordingly, cooking of sweet potatoes by the electronic range and steaming derived no degradation of ascorbic acid, bacause the temperature in the sweet potato rapidly reached 100°C and the enzyme was inactivated by the high temperature before it sufficiently reacted with ascorbic acid in the cells. On the other hand, sweet potatoes were heated slowly and kept at 60° to 70°C for a long time as roasting, ascorbic acid in the sweet potato was oxidized actively by ascorbate oxidase.
