Optimization of ultrasonic-assisted enzymatic hydrolyzing of black-soybean protein

Different proteases were used to hydrolyze black-soybean protein,according to the protein hydrolysis degree(DH).Alcalase protease was selected as the most appropriate enzyme.Ultrasound pretreatment was applied to the Alcalase protease hydrolysis of black-soybean protein.In the singlefactors analysis,the influences of the ultrasound time,power,substrate concentration,pH,temperature and enzyme concentration on the protein hydrolysis degree and DPPH ? scavenging activity were studied. The response surface analysis were used to optimize the condition of enzyme hydrolysis,the results showed that the optimum condition for preparing black-soybean peptides with high-DPPH ? scavenging activity were:ultrasound 20 min,ultrasound power 1029.27w,substrate concentration 4.04%,pH 8.64, temperature 50℃,enzyme concentration 4.10%.Under this condition,the DPPH? scavenging activity of the peptides obtained is 86.37%.