Isoflavone composition, polyphenols content and antioxidative activity of soybean seeds during tempeh fermentation

The content of polyphenols and the antioxidative properties were determined in soybean tempeh fermented by four strains of Rhizopus oligosporus. The highest concentration of polyphenols was observed in soybean fermented for 4 days by R. oligosporus strain NRRL 5905 (5.307 mg/g). The strength of antioxidative activity increased from the first day of fermentation to the fourth day, and on the fourth and fifth fermentation day it was near 12 times higher than in unfermented material. Isoflavone content and composition were analysed. The content of isoflavone aglycones (daidzein and genistein) increased up to the third day of fermentation. Fermentation time and the kind of used R. oligosporus strain are factors that enable creation of prohealthy quality of tempeh