Optimization of the Production of Protein Hydrolysates from Cotton Seed by Response Surface Methodology

Protein hydrolysates are compounds with low molecular weight that after entering the body are easily absorbed and play important biological roles in cellular levels. The most important functions of bioactive compounds are antioxidant, antimicrobial, anticancer activities and enhance the immune system. The main objective of this study was to produce cotton seed protein hydrolysate using pepsin enzyme that was optimized by response surface methodology. The factors investigated in this study were temperature (30-40◦C), time (2-5h) and enzyme/substrate ratio (0.5-2%) in order to obtain maximum antioxidant activity. The antioxidant activities were investigated using 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging capacity, total antioxidant capacity, reducing power and chelating activity. All of the experiments were designed according to the central composite design. Each of the studied variables had a significant effect on the responses (p<0/05). The optimal conditions to achieve maximum antioxidant activity were temperature of 31.1◦C, time of 5h and enzyme/substrate ratio of 1.75%, respectively. Under these conditions, (DPPH) free radical scavenging capacity, reducing power, chelating activity, total antioxidant capacity and degree of hydrolysis were 83%, 0.158 Å, 70%, 1.99 mmol α- tocopherol/mL and 31.75%, respectively. Cotton seed protein hydrolysates have exhibited good antioxidant activity and might be employed as a natural antioxidant in food products and formulations.