Fermentation of texturized vegetable proteins extruded at different moisture contents: effect on physicochemical, structural, and microbial properties

To investigate the effect of fermentation on texturized vegetable protein (TVP), TVPs extruded at 40 and 50% feed moisture contents (MC) were fermented using Bacillus subtilis at 37 °C. Physicochemical, structural and microbial properties of TVPs were determined at 0, 12, 24, 36, 48, and 60 h after fermentation. Integrity index of fermented TVPs did not change significantly until 24–36 h after fermentation. Springiness and cohesiveness remained stable after fermentation in all samples. Significant total color change was observed during fermentation. The pH values dropped initially and rose again with a coincident increase in nitrogen solubility index and viable cell count of B. subtilis. During fermentation, TVP extruded at 50% MC maintained higher chewiness, hardness, integrity index, and layered structure than that extruded at 40% MC. The study demonstrated that fermenting the TVP extruded at 50% MC has potential to produce a new type of TVP based B. subtilis fermented food.