Abstract: The hydrolisis conditions of papain, subtilisin(As1.398) and pepsin with the criterion of scavenging activity ofhydroxyl radical of hydrolysed casein were studied by the orthogonal experiment design. The optimum conditions of papainhave been found as follows: pH7.5, enzyme concentration 8%, hydrolysis temperature 45℃ and hydrolysis time 90min. Themaximum scavenging rate of hydroxyl radical (71.28%) of the hydrolysate by papain did not differ siginificantly from that of thesame concentration of Vitamin C and Vitamin E(p>0.05). The optimum conditions of subtilisin have been found as follows, pH7.5, enzyme concentration 8%, temperature 45℃, hydrolysis time 90min with the maximum scavenging rate of hydroxyl radicalas 68.60%. The optimum conditions of pepsin have been also found as follows: pH7.5, enzyme concentration 8%, temperature45℃ and hydrolysis time 90 min; with the maximum scavenging rate of hydroxyl radical as 66.53%. Enzymic hydrolysates ofcasein could inhibit lipid oxidation and the maximum inhibition rate could go up to 59.28%.

Key words: casein, enzymic hydrolysates, antioxidation, hydroxyl radical, scavenging activity