The Effect of Heat and Freeze-thaw Pretreatment on the Alcalase Enzymatic Hydrolysis of Lentil Protein and Production of Antioxidant Peptides

The biological activity of protein hydrolysis products is affected by the enzyme type, protein type and enzymatic hydrolysis conditions including temperature, time and enzyme/substrate ratio and pre-treatment process.The protein pretreatment process can cause improving the enzymatic hydrolysis and production of antioxidant peptides by affecting the spatial structure of the protein and increasing the enzyme access to the peptide bounds. In this study, The protein extracted from lentils was first subjected to heat pretreatment (65,75, 85°C, for 15 min) and freeze-thaw (3 freezing cycles at -20 °C and thawing at room temperature). It was then exposed to hydrolysis for 3 hr by alcalase (with an E/S of 90 AU / kg protein, 55°C). Over time, the progress of enzymatic hydrolysis and antioxidant activity were investigated by O-phthaldialdehyde (OPA) assay and DPPH and ABTS radical scavenging methods and compared with the control sample (without pretreatment). Pre-treatment at 75°C causes the highest value of free amino groups .The maximum DPPH (63.57%) and ABTS (36.24%) radical scavenging activity were observed respectively, for samples pre-treated at 65°C and by freeze-thaw process. Heat pretreatment and freezing-thawing before enzymatic hydrolysis have a positive effect on the development of enzymatic hydrolysis and production of antioxidant peptides. Based on the results of this study, the process of heat treatment of lentil protein at 65°C or freezing-thawing and enzymatic hydrolysis by enzyme alcalase was identified as an effective method in the production of lentil protein hydrolysis for use in the formulation of functional foods.