A systematic, comparative study on the beneficial health components and antioxidant activities of commercially fermented soy products marketed in China.

The objectives of this study are to systematically assess the bioactive substances and overall antioxidant capacities of commercially fermented soy products and to find the relationships between the presence of beneficial components in different types of soybean fermented products. The results show that phenolic profiles increased significantly after fermentation as compared with raw yellow soybeans. Among all the samples, the douchi and fermented black bean sauce had the highest detected antioxidant profiles. Even though the total isoflavone content was reduced in fermented soybean products (794.84 μg/g on average) as compared with raw yellow soybeans (3477.6 μg/g), there was an obvious trend of conversion of the glucoside form in raw soybeans into the aglycone-form isoflavones in the fermented soybean products. The highest daidzein and genistein values were found in the "Yangfan" black bean douchi, i.e. 860.3 μg/g and 1025.9 μg/g, respectively. The amounts of essential amino acids also were improved in most fermented soybean products. The douchi and black bean fermented products are recommended for consumption due to their abundant bioactive substances.