Optimization for enzymatic hydrolysis of Gracilaria lemaneiformis protein and antioxidant activity of its hydrolysate

Response surface methodology (RSM) was employed to optimize the process conditions for the enzymatic hydrolysis of Gracilaria lemaneiformis protein. After the single enzyme screening experiments, the ferrous ion-chelating and DPPH free radical scavenging abilities as the main index, the degree of hydrolysis as the auxiliary index, the effects of hydrolysis time, p H, hydrolysis temperature, concentration of substrate and enzyme dose on the degree of hydrolysis and the antioxidant activity of hydrolysates were investigated based on the single factor experiments.The results showed that protamex was the best enzyme for the enzymatic hydrolysis of Gracilaria lemaneiformis protein.The optimal conditions for the ferrous ion-chelating ability and the scavenging activity on DPPH free radical were as follows: hydrolysis time of 8.1 h, p H7.0, temperature of 50.1 ℃, substrate concentrate of 10 g/L, and enzyme dose of 0.1%.Under these conditions, the ferrous ion-chelating ability of hydrolysate was up to 74.61%, significantly higher than that of 0.01% ascorbic acid and 0.01% BHA (p < 0.05) .The scavenging ability of DPPH free radical was 47.66%, and the degree of hydrolysis was 17.58%, lower than that of 0.01% ascorbic acid and 0.01% BHA (p < 0.05) . These results suggested that the protein hydrolysates possess excellent antioxidant activity.