Effect of proteases on the functional properties of pea protein isolates

Plant proteins are promising candidates for the green transition in foods, but they have low functionality. Partial hydrolysis is gaining interest as a way to modify the functionality of plant proteins. The degree of hydrolysis (DH) is the “golden standard” to characterize partial hydrolysis. In this work, we hydrolyzed pea protein isolate (PPI) with three enzymes (Novozym, Alcalase, and Neutrase) at a range of enzyme concentrations, and we characterized the hydrolysates for DH and a range of food relevant functionalities including fermentation induced gel formation. The results indicate that the DH was insufficient to correlate with functional properties. For example, hydrolysis increased viscosity in all systems, with more extensive hydrolysis resulting in a greater increase in viscosity for individual enzymes. However, at low DH (≈ 0.5–1%), Alcalase hydrolysates exhibited ~ 400% higher viscosity than those from Novozym, while Neutrase hydrolysates showed the lowest viscosity despite having the highest DH. Similarly, hydrolysis increased the foaming ability of PPI, but the sample with the highest DH (hydrolyzed with Neutrase) showed a medium effect, and at a similar DH, Alcalase hydrolysis increased foamability to a larger extent. These findings indicate that DH alone was insufficient to explain variations in PPI functionality, and that enzyme specificity, leading to distinct hydrolysate compositions, played a key role. Moreover, hydrolysates formed harder gels during fermentation (4–171 g) only when transglutaminase was added.