Effects of germination and osmopriming treatment on enhancement of isoflavone contents in various soybean cultivars and cheonggukjang (fermented unsalted soybean paste).

To develop soybean products containing high isoflavone contents, the effects of germination and osmopriming on the isoflavone contents of 3 soybean cultivars (Ilmi, Daehwang, and Taekwang) were investigated. Total isoflavone contents of Ilmi and Daehwang cultivars were not significantly different with soaking time at 20 and 25 degrees C. Ilmi and Taekwang cultivars had higher total isoflavone contents at 0.243 to 0.256 and 0.072 to 0.079 g/100 g, respectively, after 12 h of germination at 20 degrees C than those at 0.232 and 0.064 g/100 g at the initial stage. After 48 h of germination at 20 degrees C, contents of total isoflavone, daidzein, and genistein were 0.246, 0.094, and 0.147 g/100 g, respectively. In contrast, after 48 h of germination and 0.2 M NaCl treatment at 20 degrees C, those contents increased up to 0.346, 0.140, and 0.203 g/100 g, respectively. Total isoflavone and genistein contents of cheonggukjang prepared with germinated soybean or soybeans treated with osmopriming were 0.322 and 0.198 g/100 g, 0.332 and 0.201 g/100 g, respectively, at 48 h of fermentation, and were higher than those of the control group (0.277 and 0.169 g/100 g). We concluded that cheonggukjang would contain higher isoflavone contents after the treatment of germination and osmopriming.