Value-Addition of Defatted Peanut Cake by Proteolysis: Effects of Proteases and Degree of Hydrolysis on Functional Properties and Antioxidant Capacity of Peptides

Abstract

In this study, the effects of types of enzymes and degree of hydrolysis on functionalities, DPPH radical scavenging activity, and molecular weight distribution of the peanut protein hydrolysate (PPH) were investigated. Peanut protein was extracted from the oil cake by isoelectric precipitation method. The protein was subjected to controlled hydrolysis using alcalase and pepsin enzymes to yield products with different degrees of hydrolysis (8–17%). The main functional properties of hydrolysates such as solubility, fat absorption capacity (FAC), emulsifying activity index (EAI), emulsifying stability index (ESI) and DPPH radical scavenging activity were determined. Molecular weight distributions were analyzed using SDS-PAGE gel analysis. The results demonstrated that, under studied conditions, the functionalities of PPH were more dependent on types of enzymes than their degrees of hydrolysis. At the same DH, FAC (3.65–3.88 g oil/g PPH) and ESI (71.6–85.2%) of pepsin hydrolysates were higher than FAC (0.58–1.49 g oil/g PPH) and ESI (34.4–50.5%) of alcalase. However, alcalase PPH had better EAI and radical scavenging activity than that of pepsin. Hydrolyzed peanut protein had molecular weights predominantly < 15 kDa. The enzymes used had different specificities toward peanut protein hydrolysis indicated by the distinct molecular weight distribution and functionalities of the corresponding PPH. The findings, to a certain extent, could serve as an important basis for controlling and optimizing peanut protein hydrolysis for specific applications in food industries.