Effects of Microwave Pretreatment on Enzymatic Hydrolysis of Pumpkin Seed Protein (Cucurbita maxima L.) Using Trypsin and Investigation of the Protein Antioxidant Activity Using Response Surface Methodology

In this study, effects of microwave pretreatment in optimizing conditions of enzymatic hydrolysis of pumpkin seed protein (Cucurbita maxima L.) was investigated using enzyme trypsin to achieve the maximum antioxidant activity using Design Expert software and response surface methodology.

The solution containing pumpkin seed concentrate was exposed to microwave energy with power of 450–900 W and time of 30–90 s. Enzymatic hydrolysis was carried out using trypsin enzyme with quantities of 0.5 to 2.5% per substrate, time intervals of 20 to 190 min and the optimum temperature and pH of trypsin. Antioxidant activity was assessed using DPPH free radical scavenging method, iron chelation activity and total oxidant activity (absorbance in 695 nm).

The maximum DPPH free radical scavenging of 56.5%, iron chelation activity of 96.9%, total oxidant activity (absorbance in 695 nm) of 1.03 and hydrolysis degree of 22.3% in condition without pretreatment were achieved within 190 min at 1.5% E/S ratio. Using microwave pretreatment, the maximum DPPH free radical scavenging of 55.3%, iron chelation activity of 94.5%, total oxidant activity (absorbance in 695 nm) of 1.07 and hydrolysis degree of 25.8% were achieved within 105 min at 1.5% E/S ratio. These results were largely similar to those presented by the software (respectively without pretreatment in 165.1 min and 1.65% E/S 55.1%, 95.5%, 1.02, 21.35 and with pretreatment in 106 min and 1.37% E/S 51.1%, 93.7%, 1.05, 24.9).

Microwave pretreatment in enzymatic hydrolysis of pumpkin seed proteins using  trypsin enzyme has resulted in production of hydrolysates with appropriate antioxidant activity in addition to significant decreases of the hydrolysis time, which can be replaced by artificial preservatives in nutritional products as natural compounds.