Application of Vacuum-Cooking to Plant-Based Foods: Boiled Soybeans and Cooked Soybeans

Abstract

This study investigated the practicality of preparing soybeans by vacuum-cooking and the usefulness of this method in retaining the isoflavones. Under the low-water-volume conditions of vacuum-cooking, the isoflavone retention ratio in soybeans was approximately 90%, and there was a transfer of approximately 5% into the cooking water, demonstrating that there is less leaching of isoflavone into the boiling water compared with conventional cooking.

The vacuum-cooking that uses less water is a useful method for improving the isoflavone retention rate in soybeans, and soaking is important for increasing the level of aglycone in boiled soybeans. Also, during vacuum-cooking, the vacuum promotes absorption of water at lower temperatures at the start of heating, even without soaking, making it possible to soften the beans comparatively uniformly by extending the heating period.

Although vacuum-cooking requires heating for a long time, it was clearly demonstrated to be a useful method in terms of operational convenience and high isoflavone retention ratio.