Abstract
The effect of cooking on the losses of ascorbic acid in vegetables and of activity of ascorbic acid oxidase was determined.
1. The loss of ascorbic acid in vegetables was greater in samples added in water of low temperature and cooked than those added in boiling water and then cooked. This tendency was observed significantly in ‘shungiku’.
2. The presence of ascorbic acid oxidase was observed in ‘shungiku’ brussel sprouts, and immature greenpeas. It appears that the enzyme which is contained in ‘shungiku’ and catalyses the oxidation of ascorbic acid is a mixture of catecholase and ascorbic acid oxidase. The loss of ascorbic acid while cooking was greater in vegetables havin the higher a activity of ascorbic acid oxidase.
3. The inactivated enzyme solution of ‘shungiku’ showed further some activity to destroy ascorbic acid. It seems that this is due to quinones formed from phenolic compounds by the action of catecholase during enzyme preparation.
4. When ‘shungiku’ was cooked in salted water the retention of ascorbic acid was observed to be greater than that obtained without salt, and this protecting effect of NaCl against ascorbic acid was only observed with NaCl solution of 1M or more over concentration.
