Hydrolysis of isoflavone glycosides in soy milk by β-galactosidase and β-glucosidase

Abstract

The objective of this study was to assess the potential of pure β-galactosidase and β-glucosidase for hydrolyzing isoflavone glycosides to aglycones in soy milk. Both pure β-galactosidase and β-glucosidase were added at various concentrations (0.5, 1.0, 2.0 and 4.0 U/mL) to soy milk made from 4% soy protein isolate and incubated at 37C for up to 240 min. Isoflavones were quantified using high-performance liquid chromatography. The isoflavone contents of soy milk before and after autoclaving were also compared. β-Glucosidase and β-galactosidase were both able to hydrolyze the β-glucosidic linkages in isoflavone glycosides. A range of 43.3 to 77.2% of the total isoflavone glycosides was hydrolyzed at various β-galactosidase concentrations. The β-glucosidase hydrolyzed isoflavone glycosides more efficiently than β-galactosidase. At the most diluted β-glucosidase concentration (0.5 U/mL), 86.6% of isoflavone glycosides were hydrolyzed to aglycones at 240 min. © 2009, Wiley Periodicals, Inc.