| To reduce the wastage of aquatic resources and improve the additional value of cod swim bladder, we determined the optimum technological conditions for antioxidant peptides from the cod swim bladder and observed the changes in antioxidant activities after being digested in vitro. Six kinds of proteases, namely, acid proteinase, dispase, pepsin, papain, compound proteinase, and trypsin, were used to hydrolyze the cod swim bladder in order to select the optimal protease by determining the degree of hydrolysis and DPPH radical scavenging rate. Combining the single factor method and response surface methodology, the optimum process was ensured at the hydrolysis temperature of 58.56℃, hydrolysis time of 6 h, pH of 7.21, and enzyme addition of 200 U/ml. The results of the confirmatory experiment showed that the scavenging rate of DPPH was 61.1%, which agreed with the predicted value of 62.0%, and the results proved that the optimized extraction process was stable and reliable. The free radical scavenging rates of peptides were detected, and the results showed that swim bladder peptides have good abilities of scavenging free radicals of DPPH, OH, O2-, and chelating Fe2+. Besides, the half maximal inhibitory concentration (IC50) of these was 8.29 mg/ml, 5.03 mg/ml, 5.43 mg/ml, and 1.35 mg/ml, respectively. After being digested in vitro, the degree of hydrolysis increased while the free radicals scavenging abilities and chelating power of Fe2+ decreased. This might have occurred because the changes of reaction conditions in the simulated gastrointestinal digestion process such as the change of pH value lead to the changes of composition and structure of the peptides. Meanwhile, the changes of composition and structure lead to the changes in antioxidant activities. In conclusion, swim bladder peptides had potent antioxidants and could serve as useful ingredients in the food industry. |
