Optimising the free radical scavenging activity of shrimp protein hydrolysate produced with alcalase using response surface methodology

P>Response surface methodology (RSM) was used to optimise the hydrolysis parameters of Acetes chinensis by Alcalase 2.4L in order to obtain a hydrolysate with potent radical scavenging activity. The parameters were temperature, pH and enzyme concentration/substrate concentration (E/S) ratio with degree of hydrolysis (DH) being the response. The results showed that the optimum condition was: temperature at 57 degrees C, pH at 8.0, E/S ratio at 2.6AU 100 g(-1) shrimp, hydrolysis time 3 h. The DH was 26.32%, the hydroxyl radical scavenging activity was up to 88.12% and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was 35.61%. The gel column filtration chromatography by a Sephadex G-25 column yielded five fractions. The molecular weight of the most potent free radical scavenging activity fraction ranged from 915 to 207 Da, its IC50 for hydroxyl radical was 0.03 mg mL(-1), and IC50 for DPPH radical was 8.86 mg mL(-1).