Protein hydrolysate have many practical applications in a various of industries due to the bioactive peptides related to their amino acid composition, sequence and molecular weight. The amino acid composition, molecular weight distribution and antioxidant stability of alcalase hydrolysate were investigated in this study. The hydrolysate was separated into five fractions by ultra filtration system with different molecular weight cutoff with 10, 5, 3 and 1 kDa, respectively. The protein content, 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and molecular weight of each fraction were determined. In addition, the antioxidant stability of the hydrolysate under several operating conditions was studied. The results showed that the hydrolysate was composed with high amounts of hydrophobic amino acids (40.4%) which might contribute to the high antioxidant activity. The fraction with molecular weight lower than 1 kDa exhibited the highest antioxidative activity among the five fractions. The antioxidant stability experiments showed that the hydrolysate was stable when it was heated up to 100°C and the relative antioxidative activity could be maintained nearly 70% at very low pH of 2.0. Glucose and sucrose had negative effects on the antioxidative activity, in which the relative activity of about 80% was retained. Sodium chloride and sodium benzoate had little or no effects on the antioxidative activity of the hydrolysate. The effects of Zn2+ and Cu2+ on the antioxidative activity were significant and dependent on metal concentration. The shrimp processing byproduct hydrolysate may be a potential natural food antioxidant in the future.
J. Zhao, G.R. Huang, M.N. Zhang, W.W. Chen and J.X. Jiang, 2011. Amino Acid Composition, Molecular Weight Distribution and Antioxidant Stability of Shrimp Processing Byproduct Hydrolysate. American Journal of Food Technology, 6: 904-913.