Abstract:The soybean was hydrolyzed by the Aspergillus niger β-glucosidase to convert the bound soy isoflavone glycosides into a free aglycone. Using soybean as the raw material, the influence of three factors (enzyme dose for addition, reaction time, reaction temperature) on the hydrolysis of soybean isoflavone glycosides in soy milk was first investigated in single factor experiments. According to the Box-Behnken center-united experimental design principles, three factors and three levels were adopted based on the combinations of different enzyme doses, reaction times and reaction temperatures to establish polynomial regression prediction models for the isoflavone aglycone content in soy milk and determine the optimal process parameters. The results showed that optimal hydrolysis conditions were as follows: the enzyme dose, 0.028 U/5 mL; reaction time, 1.64 h; reaction temperature, 53.82 ℃. Under these conditions, the content of isoflavone aglycone in soy milk was significantly improved, with the concentrations of daidzein (De), glycitein (Gle) and genistein (Ge) being 39.434±1.410, 4.626±0.462, 45.851±2.098 μg/mL, respectively. The response surface prediction values of De, Gle and Ge were 40.905, 4.263, and 48.441 μg/mL, respectively, indicating that the measured values were close to the predicted values. The optimized process conditions are reasonable and feasible, and can allow a significant increase in the contents of isoflavone aglycones in soy milk.
