Production of the isoflavone aglycone and antioxidant activities in black soymilk using fermentation with Streptococcus thermophilus S10

Abstract

The best starter culture for fermented black soymilk was determined. Black soymilk was fermented using Lactobacillus acidophilus ATCC 4356 (LA), Lactobacillus plantarum P8 (LP), and Streptococcus thermophilus S10 (ST). An ST single culture exhibited higher β-glucosidase activities than LAST (LA:ST=1:1, v/v), LPST (LP:ST=1:1, v/v), and LALPST (LA:LP:ST=1:1:1, v/v) mixed cultures. The pH of fermented black soymilk was significantly (p<0.05) decreased during fermentation due to an increase in lactic acid formed by lactic acid bacteria. The β-glucosidase activity of the ST single culture was significantly (p<0.05) higher than for mixed cultures. Black soymilk fermented with ST alone showed significantly (p<0.05) more bioconversion of the isoflavone glycoside to aglycone, compared with controls. Black soymilk fermented with ST resulted in the best antioxidant effect. The ST single culture was best for production of health functional fermented black soymilk.