Effect of different processing methods on isoflavone content in soybeans and soy products

This study investigated the effect of different hydrothermal and biotechnological processes on the changes in isoflavones in soybeans. The cooking of soybeans resulted in increased genistin and decreased glycitin by 60–80%, while aglycones – daidzein and genistein –remained unchanged. The water/soybean ratio had a more pronounced effect on isoflavones than the heating duration. Tempe fermentation caused a decrease in daidzin, glycitin and genistin by 77%, 93% and 43%, respectively. Whereas the level of daidzein and genistein increased 12 and 14 times, respectively. Sprouting soybeans for 11 days caused the highest reduction in the total content of analysed isoflavones. The daidzin and glycitin content in soy chops after frying dropped by 75% and 93%, respectively, while genistin, daidzein and genistein levels did not change, remaining at about 76%. The cooking of soy pasta contributed to a decrease in daidzin, glycitin, genistin, daidzein and genistein by 59%, 54%, 49%, 72% and 62%, respectively. Our study shows the impact of popular treatments on the content of isoflavones, which may be useful in choosing the type of treatment depending on the individual consumer’s health needs.