| With degree of hydrolysis (DH) and scavenging rate on DPPH· radical as indexes, the optimal enzymolysis conditions of cottonseed protein by alkali protease for preparation of cottonseed peptide were studied by single factor experiment and orthogonal experiment. With ascorbic acid (VC) as control, the total reducing power and the scavenging effects of cottonseed peptide on hydroxyl radical and superoxide anion radical and its partial properties were also explored. The results showed that the optimal preparation conditions of cottonseed peptide were obtained as follows: reaction time 180 min,pH 9.5, temperature 55℃, mass concentration of substrate 3.00 mg/mL and dosage of alkali protease 50 U/mL. Under these conditions, the scavenging rate of cottonseed peptide on DPPH· radical and DH were 63.42% and 85.90%, respectively. The scavenging rates of cottonseed peptide on hydroxyl radical and superoxide anion radical both increased with its mass concentration increasing, and half inhibitory concentrations (IC50) of cottonseed peptide were 0.044 mg/mL and 0.046 mg/mL, respectively, both stronger than that of VC. Total reducing power of cottonseed peptide was dosage-independent and weaker than that of VC. Isoelectric point of cottonseed peptide was about 2. The scavenging rates of cottonseed peptide on hydroxyl radical all reached maximum in 60 min under different pH, while they were basically stable at different temperatures with time passing and reached the highest at 60℃. |
