Fermentation of Pea Protein Isolate by Enterococcus faecalis 07: A Strategy to Enhance Flavor and Functionality

Pea protein isolate (PPI) is a plant protein with high nutritional value, but its application in food is limited by an unpleasant beany flavor. This study aimed to investigate the feasibility of improving the flavor of PPI through fermentation with Enterococcus faecalis 07. PPI was subjected to fermentation by E. faecalis 07 for different durations (0 H, 24 H, 48 H, and 72 H). After fermentation, pH, viable cell counts, free amino acid contents, electronic tongue analysis, and volatile organic compounds were determined. The results showed that fermentation significantly reduced the bitterness of PPI and enhanced its umami intensity. A total of 64 volatile organic compounds were identified in the fermented samples, 42 more than in the unfermented sample. Quantitative analysis revealed that hexanal (grass-like odor) decreased by 92% after 72 h of fermentation, 1-octen-3-ol (mushroom-like odor) decreased from 6.94 mg/kg to 1.73 mg/kg, and trans-2-octenal decreased to 0.59 mg/kg; meanwhile, aromatic compounds such as esters and ketones were produced. Along with changes in the physicochemical properties, organic acids, and free amino acid composition of PPI, correlation analysis between electronic tongue data and volatile compounds further indicated that changes in volatile components simultaneously affected the perception of five taste attributes of PPI (bitterness, sourness, sweetness, saltiness, and umami). In conclusion, this study demonstrated the feasibility of fermenting PPI with E. faecalis 07, which effectively improved its sensory attributes and physicochemical properties to a certain extent.