Effects of fermentation temperature on the content and composition of isoflavones and β-glucosidase activity in Sufu

Sufu is a popular fermented tofu product in China. The low quality of sufu produced in the hot summer is a big problem in sufu manufacture, so we prepared sufu at two different temperatures, 26degreesC as normal and 32degreesC as high temperature, and the effects of temperature on isoflavones and beta-glucosidase activity were investigated. Fermentation temperature did not cause significant differences in the recovery of isoflavones, but resulted in a different redistribution of isoflavone isomers in sufu. Sufu fermented at 26degreesC was richer in isoflavone aglycones than at 32degreesC; the enrichment of isoflavone aglycones might have the advantage of enhancing the physiological function. No 6-O-malonyl-glucosides were detected in sufu fermented at 26degreesC, whereas some 6-O-malonyl-glucosides were found at 32degreesC. A fermentation temperature of 26degreesC benefited the P-glucosidase production by fungi, which contributed to valid conversion from P-glucosides to aglycones. It was also found that P-glucosidase converted P-glucosides more effectively than 6-O-malonyl-glucosides and 6-O-acetyl-glucosides into aglycones.