Promotion of Fungal Growth, Antibacterial and Antioxidative Activities in Tempe Produced with Soybeans Thermally Treated Using Steam Pressure

Tempe is produced by thermally treating soybeans with boiling and subsequent fermentation using Rhizopus oligosporus. In this study, thermal processing by boiling was replaced with steam pressure, and the physicochemical features and biological activities of tempe were examined. Retention of nutrients and the fungal growth rate were higher in soybeans treated by steam pressure than in those treated by boiling. Antibacterial activity against Staphylococcus aureus was found in extracts of soybeans after fermentation, and the activity was higher in tempe processed by steam pressure. Antioxidative activities in extracts of soybeans before and after fermentation were higher using steam pressure than boiling. These results suggested that in tempe processed by steam pressure, the promotion of antibacterial activity was due to the increase in fungal growth, whereas the enhanced antioxidative activities were mainly due to increases in the antioxidative activities in soybeans before fermentation.