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.

The extract components of mussels were compared with oysters, hard clams, and short-necked clams to evaluate their taste characteristics. Succinic acid was the most abundant in mussels. Regarding the taste-active values, glutamic acid (Glu), inosine monophosphate (IMP), adenosine monophosphate, and succinic acid were greater than 1 in mussels; Glu, aspartic acid (Asp), alanine (Ala), proline, and succinic acid in oysters; Glu, Ala, Asp, and succinic acid in hard clams; and Glu, Asp glycine, Ala, IMP, and succinic acid in short-necked clams. The equivalent umami concentration of mussels was not significantly different from that of the other shellfish. These results suggest that succinic acid and the synergistic effects of amino acids and umami nucleotides contribute to mussel taste. Hierarchical cluster analysis showed that each of the four shellfish species belonged to a different cluster. Hard and short-necked clams and mussels and oysters were classified into two clusters.