Abstract: Commercial soybean power was hydrolyzed under alkaline conditions and then treated at low pressure levels. Our aim was to investigate the effect of alkaline hydrolysis under optimized conditions followed by low pressure processing on the conversion of soybean isoflavones to aglycones. Soybean isoflavones and aglycones were detected by high performance liquid chromatography (HPLC). The two processes were optimized using one-factor-at-a-time method and response surface methodology. In the alkaline hydrolysis process, hydrolysis time, temperature and pH were taken as independent variables, and the percentage increase in glucoside isoflavones as response variable. Subsequently, low pressure processing time, solid-to-solvent ratio and pressure were optimized for higher conversion rate of aglycones. The results showed that pH 11.5, a temperature of 63 ℃ and a hydrolysis time of 49 min were found to be the optimal conditions to obtain a higher increase in glucoside isoflavones of 286.40%. The conversion rate of aglycones was 16.65% when the hydolysate was processed for 10 min at 0.25 MPa with a solid-to-solvent ratio of 1:120 (g/mL).

Key words: isoflavone aglycones, alkaline hydrolysis, low pressure, conversion rate；response surface methodology