Effect of enzymatic hydrolysis using endo- and exo-proteases on secondary structure, functional, and antioxidant properties of chickpea protein hydrolysates

Abstract

Chickpea protein isolate was hydrolyzed batchwise using Alcalase as an endopeptidase and Flavourzyme as an exopeptidase, by either individual or sequential treatment. Secondary structure, SDS-PAGE molecular weight profile, functional properties, and antioxidant activity of the hydrolysates were investigated. Alcalase was more effective than Flavourzyme to cleave the peptide bonds, and the degree of hydrolysis (DH) of Alcalase-treated hydrolysate was 25.8% compared to Flavourzyme-treated counterpart with a DH of 11.9%. Sequential treatment increased the DH up to 50%. The hydrolysis process significantly changed the protein’s secondary structure characterized by decreased ordered structures and increased disordered structures. The more notable changes occurred for those that were treated sequentially. Protein banding patterns of the hydrolysates were also markedly changed, especially for those treated by Alcalase in which no visible band was observed. Furthermore, hydrolysates had a significant (P < 0.05) increase in the solubility, emulsifying capacity, and DPPH· scavenging capacity. The changes in DH and protein secondary structure significantly correlated with functional properties and DPPH· scavenging capacity. DH presented a significant inverse association with emulsifying stability (r = − 0.940), but a positive correlation with DPPH· scavenging activity (r = 0.951). β-sheet was found to be negatively correlated with both solubility (r = − 0.979) and DPPH· scavenging activity (r = − 0.979). However, an opposite trend was observed for β-turn which positively correlated with both solubility (r = 0.881) and DPPH· scavenging activity (r = − 0.909). The results reveal that hydrolysis enhanced the functional properties and antioxidant activity of chickpea protein which may be beneficial for potential functional food ingredient applications.