Isoflavone content in Korean fermented and unfermented soybean foods

Soybean isoflavones known as an anticarcinogenic factor were evaluated in some Korean soybean foods by high performance liquid chromatography. Unfermented soybean foods contained predominantly isoflavone (genistin and daidzin), but in the fermented soybean foods isoflavones were present mainly as aglycones (genistein and daidzein). Average contents of isoflavones of tofu, soymilk and soy sprout were 1, 151, 676 and 424 mg/kg, respectively. Among the fermented soybean products, soybean paste (Chongkukjang) was highest in the isoflavone content (920 mg/kg) and the degree of hydrolysis of bonds was ranged from 30 to 100%. Doenjang, Chunjang and Kanjang contained lesser amounts of isoflavones and their contents were 627, 291 and 10 mg/kg, respectively. Korean traditional fermented foods, Chongkukjang and Doenjang could be regarded as the excellent sources of soy isoflavone aglycones.