Abstract
A series of thawing experiments was conducted on frozen young legumes of the kidney beans (Phaseolus vulgaris L., ) by routine methods with 10°C as the final thawing temperature and the residual amount of L-ascorbic acid was measured. It was found that in comparison with the value at blanching the residual rates of L-ascorbic acid were (1) 86.2± 5.2% when thawed in a refrigerator, (2) 80.8± 4.2% when thawed naturally, (3) 80.8± 4.5% when thawed in a microwave oven, and (4) 76.4± 6.6% when thawed under running water. Analysis of variance and t-test demonstrated that thawing in a refrigerator produced significantly better results than thawing by other methods.
The residual amount of L-ascorbic acid following cooking was measured. A loss of about 20% was observed even when the beans were thawed with the most proper method and cooked, after 2 days of-20°C storage, in comparison with the content immediately after blanching of fresh beans. The residual amount showed no difference whether thawed Phaseolus vulgais were used or whether non-thawed beans were used.
