Solid-State Fermentation of Texturized Vegetable Protein using Bacillus subtilis

다국어 초록 (Multilingual Abstract)

The present study aimed to investigate the effect of fermentation on physical properties of texturized vegetable protein (TVP) by using Bacillus subtilis. TVP was prepared by texturizing the mixture of isolated soy protein (50%), wheat gluten (40%) and corn starch (10%) with the use of twin-screw extruder at two different moisture contents (40% and 50%), 100 g min-1 feed rate, 200 rpm screw speed and 130°C die temperature. Then, TVPs were subjected to solid-state fermentation using B. subtilis at 37°C for 60 h. The texture (springiness, cohesiveness, chewiness and hardness), integrity index and color (lightness, redness and yellowness) of TVPs were determined before and after fermentation for 0, 12, 24, 36, 48 and 60 h, respectively. The springiness and cohesiveness did not change significantly after fermentation in all samples. However, chewiness and hardness decreased with increased fermentation time with the lowest values observed at 60 h after fermentation of TVPs (both 40% and 50% MC). Integrity index of fermented TVPs was significantly reduced while fermentation time was increased. Integrity index started to decrease significantly at 36 h after fermentation in TVP extruded with 40% MC. In another TVP (50% MC), the integrity decreased at 24 h after fermentation but it maintained higher integrity index than TVP (40% MC) throughout the whole fermentation period. The significant total color change was observed with increased fermentation time. During fermentation, lightness and yellowness decreased but redness increased significantly. This study pointed out that TVP fermented by B. subtilis still has good texture, and thus has the potential to become an attractive food for consumers who usually avoid fermented foods due to rotten appearance with no texture.