2000 Volume 6 Issue 4 Pages 314-319
We evaluated the concentration and distribution of isoflavones in a total of 50 samples of soybean foods consumed daily in Japan by high-performance liquid chromatography (HPLC). A hierarchical cluster analysis using the measured isoflavone distribution classified these foods into 6 clusters. Experiments of heat processing representing standard commercial production processes of the foods clarified that each cluster was characterized by the effects of the heating method and temperature. Tofu, which is produced under mild heating conditions, showed similar isoflavone distribution to raw soybeans, having the highest proportion of 6″-O-malonyl-β-glucosides to total isoflavones, while soymilk, yuba, cooked soybean, and natto which are produced by comparatively stronger heat, showed a lower proportion of 6″-O-malonyl-β-glucosides and higher non-acylated-β-glucosides. In the production of kinako by roasting, the proportion of 6″-O-acetyl-β-glucosides, generated by decarboxylation of 6″-O-malonyl-β-glucosides, increased. Miso and soy sauce had an increased proportion of aglycons due to a lengthy fermentation period. Abura-age which is produced by frying tofu showed lower 6″-O-malonyl-β-glucosides than tofu, and higher 6″-O-acetyl-β-glucosides.
