Abstract: In the present study, silkworm pupae protein hydrolysates at different degree of hydrolysis were prepared with alcalase, papain, trypsin, and bromelain, respectively and their scavenging activity against DPPH, superoxide anion and hydroxyl free radicals and antihypertensive activity were comparatively determined, with the result that hydrolyzing silkworm pupae protein by alcalase to a degree of hydrolysis (DH) of 20% yielded a hydrolysate with better antixodiant and antihypertensive activities. Three main process conditions for the hydrolysis of silkworm pupae protein by alcalase, including temperature, pH and enzyme dosage were further optimized using response surface methodology. The results of response surface analysis indicated that temperature and enzyme dosage had a significant interactive effect on the hydrolysis of silkworm pupae protein and that the optimal hydrolysis conditions for achieving 20% DH and minimizing costs were 51.0 ℃, pH 9.05 and 0.38% enzyme/substrate ratio. Under these conditions, the experimental DH was 20.53%, with an error of less than 5% as compared with the predictive value, and the DPPH radical scavenging rate and ACE inhibitory rate of the obtained hydrolysate were 51.2% and 50.3%, respectively.

Key words: silkworm pupae protein, antioxidant peptide, ACE inhibitory peptide, response surface methodology, degree of hydrolysis