Optimization of enzymatic preparation of antioxidant peptides from purpleback flying squid (sthenoeuthis oualaniensis) protein by response surface methodology

Response surface methods were used to optimize the hydrolysis conditions of purpleback flying squid( Sthenoeuthis oualaniensis) for production of antioxidant peptides.Papain was the optimum enzyme selected by the single-factor tests.Based on the single-factor tests,enzyme amount,liquid-material ratio and hydrolysis time were determined by single-factor tests as independent variables,1,1-diphenyl-2-picrylhydrazyl( DPPH) radical scavenging activity as the response value. The model of quadratic regression design was established. The hydrolysis conditions were adjusted to that enzyme amount was 0.66%( w/w),liquid-material ratio was 10.2( v/w),hydrolysis time was 380 min. Under such conditions,1,1-diphenyl-2-picrylhydrazyl( DPPH) radical scavenging activity was 89.80%. The result was consistent with the model prediction. In addition,amino acid analysis showed that compared with purpleback flying squid protein,the content of essential amino acids of enzymatic hydrolysis product was increased to 2.2 times,antioxidative amino acids such as methionine and tryptophan was increased to7.2,25.6 times,respectively.