Optimization of enzymatic hydrolysis parameters for antioxidant capacity of peptide from goat placenta

The goat placenta protein was hydrolyzed by pepsin and the optimal hydrolysis parameters of strongest antioxidant capacity of peptides were obtained using response surface methodology (RSM). The effects of reaction temperature, pH value and enzyme to substrate (E:S) ratio on the reducing power (RP) of the peptides and degree of hydrolysis (DH) of protein were well fitted to a quadric equation with high determination coefficients. The hydrolysate with optimal RP was predicted to be obtained at: temperature of 36.5 °C, pH value of 1.05, and E:S ratio of 2.03% and 3–10 kDa fraction (10 mg/mL), rich in GLY, GLU, ASP and TYR, was proved to exhibit highest RP, which is equivalent to the RP of 0.189 mg/mL ascorbic acid. The fraction of peptide also showed peroxidation inhibition in linoleic acid oxidation system and had a free radical scavenging ability similar to ascorbic acid (10 μg/mL) in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) system after 17 min.