Abstract: This study aimed at optimizing the ultrasonic-assisted hot water extraction conditions of water-soluble soybean polysaccharides (SSPS) from soybean residues left after the aqueous enzymatic extraction of soybean oil. On the basis of one-factor- at-a-time experiments, response surface methodology and central composite rotary design (CCRD) was employed to SSPS extraction yield with respect to ultrasonic power, ultrasonic treatment time, material-to-liquid ratio, extraction temperature and hexametaphosphate concentration, and a quadratic polynomial regression model was established. The optimal conditions for SSPS extraction were ultrasonic power of 150 W, extraction temperature of 88 ℃, ultrasonic treatment time of 17 min, material-to-liquid ratio of 1:28, and hexametaphosphate concentration of 2 g/100 mL. Under the optimal extraction conditions, the predicted and experimental extraction rates of SSPS were 12.06% and 11.52%, respectively.

Key words: water soluble polysaccharide, ultrasonic, response surface analysis, aqueous enzymatic method