Effects of boiling and steaming by steam convection oven on isoflavone derivatives in soybeans
2006
Shibata, K.(Kagawa Nutrition Univ., Sakado, Saitama (Japan)) | ; Miyoshi, K. | ; Watanabe, Y. | ; Yasuhara, Y.
We investigated the effects of boiling and steaming by steam convection oven (SC) on the taste and isoflavone derivative content of soybeans. In this study, boiling in an ordinary stainless steel pan (pan-boil), boiling by SC (SC-boil), and steaming by SC (SC-steam) were used. During presoaking for 16 h at 4 deg C, the isoflavones were mostly retained in the soybeans. Although the pan-boil and SC-boil methods gave similar results (70% retention of the original isoflavone content in soybeans with 30% leaching into the cooking water) , SC-steam resulted in nearly 100% retention of isoflavones in the soybeans, preferred method based on overall palatability of the cooked soybeans by sensory evaluation. More than 80% of total isoflavones in soybeans were categorized into 4 kinds of isoflavone derivatives: 6''-o-malonyldaidzin, 6''-o-malonylgenistin, daidzin, and genistin. Aglycone was slightly increased while malonyl glucoside changed to beta-glucoside during cooking by both the SC-boil and SC-steam methods.
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