Preparation of Polypeptides from Hemp by Two-step Enzymatic Hydrolysis with Complex Enzymes and Its Antioxidant Properties

Since hemp seeds because of rich in nutrients and do not contain anti-nutritional factors such as trypsin inhibitors have become a research hotspot in the fields of food and medicine in recent years. In this study,hemp protein isolate was enzymolysis step by step with alkaline protease and papain complex enzyme,and the hemp polypeptide was prepared by response surface. The DPPH free radical scavenging rate and iron reducing capacity were measured by spectrophotometer,and the antioxidant capacity of hemp polypeptide was evaluated. The results showed that the contents of hemp polypeptide was highest obtained by enzymatic hydrolysis of alkaline protease followed by papain. The optimal conditions of enzymatic hydrolysis were as follows:The first step was alkaline protease hydrolysis:The substrate concentration was 5%,the time of enzymatic hydrolysis was 2 h,the pH was 8.5,the temperature of enzymatic hydrolysis was 54 ℃,the amount of enzyme added was 10100 U/g.The second step was papain hydrolysis. The pH was 6.5,the temperature was 50 ℃,the amount of enzyme added was 5000 U/g,the enzymolysis time was 1.5 h,the degree of hydrolysis of hemp peptide mixture was 24.48%,and the contents of peptide was 8.48 mg/mL.The DPPH free radical scavenging rate of hemp polypeptide was 82.32%,the hemp polypeptide had stronger iron reducing ability than hemp protein isolate,which indicated that hemp poly peptide had strong antioxidant ability. This study would provide a theoretical basis for the development and utilization of hemp protein poly peptide.