Effects of Fermentation Temperature on the Content and Composition of Isoflavones and β-Glucosidase Activity in Sufu

Abstract

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, 26 degrees C as normal and 32 degrees C 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 26 degrees C was richer in isoflavone aglycones than at 32 degrees C; 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 26 degrees C, whereas some 6''-O-malonyl-glucosides were found at 32 degrees C. A fermentation temperature of 26 degrees C benefited the beta-glucosidase production by fungi, which contributed to valid conversion from beta-glucosides to aglycones. It was also found that beta-glucosidase converted beta-glucosides more effectively than 6''-O-malonyl-glucosides and 6''-O-acetyl-glucosides into aglycones.