Fermenting for flavour: Lactiplantibacillus plantarum improves flavour and functional properties of textured soy protein in meat analogue applications

The demand for plant-based meat analogues is increasing, whereas their sensory properties often fail to satisfy non-vegetarian consumers. To address this issue, this study explored how Lactiplantibacillus plantarum fermentation affected the functional and flavour characteristics of texturized soy protein (TSP) through solid-state fermentation. TSP samples were fermented at 50% and 70% moisture content and analysed at every 24-hour interval up to 168 hours. The analysis focused on microbial growth, functional properties, colour characteristics, and flavour profiles, including volatile compounds and free amino acids. A decrease in pH and an increase in viable cell count to 120 hours indicated successful fermentation. The water-holding capacity (WHC) decreased under both moisture conditions. The oil-holding capacity (OHC) remained stable at 0.8 g/g at 50% moisture but significantly increased at 70%, peaking at 72 hours before declining. Fermented TSP at 70% moisture showed higher L* (lightness) and b* (blue to yellow) colour values at 72, 120, and 144 hours compared to the 50% condition. Twenty-three key aroma compounds were identified, including alcohols, aldehydes, ketones, pyrazines, and furans, with several (e.g., methyl octanal, pyrazine, 2-heptanone, benzaldehyde, and hexanal) contributing to a meat-like aroma. The 50% moisture condition resulted in higher concentrations of umami and sweet-tasting amino acids, whereas the 70% condition maintained a steadier release of free amino acids. Overall, fermentation with Lactiplantibacillus plantarum demonstrated the potential to modify the flavour-related volatile profile and improve key functional properties of TSP, which increases its potential as an appealing plant-based meat alternative ingredient.