Abstract: Carp protein was hydrolyzed by subtilisin to prepare hydrolysate rich in peptides, and its antioxidant activity was investigated by free radical scavenging assay. The effects of the hydrolysis conditions temperature, pH, enzyme dosage, reaction time and solid-to-water ratio on degree of hydrolysis, polypeptide content, amino acid content and the abilities to scavenge hydroxyl and superoxide anion free radicals were examined in single factor experiments. Further, ternary quadratic regression rotation design was employed to optimize temperature, enzyme dose and solid-to-liquid ratio for maximizing polypeptide content. The results showed that the optimum values of temperature, pH, enzyme dosage, reaction time and solid-to-water ratio were 62 ℃, 7.0, 100 U/g, 4 h and 1:2 (g/mL). The polypeptide content in the resultant hydrolysate under these conditions was 0.704 mg/mL, and its scavenging rates against hydroxyl and superoxide anion free radicals were 73.41% and 59.78%, respectively, suggesting excellent antioxidant activity.

Key words: carp protein, hydrolysis, polypeptides, antioxidant activity