Abstract:In order to improve antioxidant activity of mulberry leaf protein (MLP), Alcalase, Protamex, Papain, Flavourzyme, Neutrase, and Trypsin were used to hydrolyze MLP. Effects of different enzymes on the chemical composition, molecular weight distribution, peptide yield, amino acid composition, radical scavenging activity and reducing power were investigated. Results showed that mulberry leaf protein was mainly composed of the fractions above 6.5 ku, while MLP hydrolysates were rich in the fractions of 0.3~0.6 ku and 0.6~6.5 ku. Limited hydrolysis of MLP could lead to higher antioxidant activity than extensive enzymatic hydrolysis. The radical scavenging activities of MLP hydrolysates were significantly correlated with the peptide yield (r=0.916~0.985). Hydrolysates prepared with neutrase, alcalase, and protamex showed significantly higher antioxidant activity than that of MLP and the other three hydrolysates. Meanwhile, the antioxidant activity of Neutrase hydrolysates was significantly better than the complex hydrolysates. Furthermore, the condition of an enzyme to substrate level of 1% (W/W), substrate concentration of 20 mg/mL and a hydrolysis time of 2 h was found to be the optimum conditions to obtain Neutrase hydrolysates (NH) with the highest antioxidant activity. In the further research, the antioxidant peptides of MLP will be prepared by Neutrase, and NH may be a promising antioxidant in food.
