Composition, functional properties and in vitro antioxidant activity of protein hydrolysates prepared from sardinelle (Sardinella aurita) muscle

Composition, functional properties and in vitro antioxidative activities of protein hydrolysates prepared from muscle of sardinelle (Sardinella aurita) were investigated. Sardinelle protein hydrolysates (SPH) were obtained by treatment with crude enzyme preparations from Bacillus pumilus A1 (SPHA1), Bacillus mojavensis A21 (SPHA21) and crude enzyme extract from sardinelle (Sardinella aurita) viscera (SPHEE). The protein hydrolysates SPHA1, SPHA21 and SPHEE contained high protein content 79.1%, 78.25% and 74.37%, respectively. The protein hydrolysates had an excellent solubility and possessed interfacial properties, which were governed by their concentrations. The antioxidant activities of protein hydrolysates at different concentrations were evaluated using various in vitro antioxidant assays, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method, reducing power assay, chelating activity, beta-carotene bleaching and DNA nicking assay. All protein hydrolysates showed varying degrees of antioxidant activity. SPHA21 had the highest DPPH radical scavenging activity (89% at 6 mg/ml) and higher ability to prevent bleaching of beta-carotene than SPHA1 and SPHEE (p < 0.05). However, SPHEE exhibited the highest metal chelating activity (89% at 1 mg/ml) and the strongest protection against hydroxyl radical induced DNA breakage (p < 0.05).