Optimization of Enzymatic Hydrolysis of Freeze-Dried Sea Cucumber Powder with Response Surface Methodology and Its Antioxidant Evaluation

In this study, freeze-dried sea cucumber powder was used as raw material and the preparation processing conditions were studied for hydrolysis of sea cucumber powder with neutral protease using Response Surface Methodology (RSM) to obtain a high concentration of sea cucumber polypeptide. The effects of hydrolysis temperature, pH, enzyme dosage and hydrolysis time on the degree of hydrolysis (DH) were studied. Based on the single factor experiment, Box-Benhnken center composite experiment was carried out with three factors and three levels, including hydrolysis temperature, pH and enzyme dosage. RSM was used to determine the effect of prime factors on the DH and establish a regression model. The results showed that the optimal hydrolysis conditions were as follows: enzyme dosage of 5753 U g^-1 dry matter, hydrolysis temperature of 52°C, pH of 8.3, substrate concentration of 5% and hydrolysis time of 5 h. Under the optimal conditions, the DH was up to 16.01%, which matched well with the predicted value. With VC as the positive control, the scavenging ability of the hydrolyzate on DPPH radicals, hydroxyl radicals and superoxide radicals were very powerful, which mean that the hydrolyzate of sea cucumber powder has good antioxidant activity.