Optimization of Soybean Isolated Protein Enzymatic Process and Its Application in Fermented Seasonings

With the aim of improving the processing added value of soybean isolate protein, the single factor and response surface testing method were used to optimize the enzymatic conditions of soybean isolate protein using hydrolysis degree and protein recovery as evaluation indexes. The enzymatic digest of soybean isolate protein fermented by Corynebacterium glutamicum was used to prepare the seasoning, which was evaluated by glutamic acid content and sensory evaluation. The results showed that the optimal enzyme digestion conditions were 2.0 g/100 g of enzyme, pH7.0, 15 g/100 mL of substrate, 54.0 ℃, and 13.0 h. The hydrolysis degree (37.1%) and protein recovery (70.3%) of the optimized enzyme solution were 1.7 times and 0.8 times higher, respectively, than those before the optimization. In the shake flask fermentation conditions, the glutamic acid content of the enzymatic digest fermentation (32.1 g/L) was increased by 32.1% compared to that before optimization. Under the batch replenishment condition of 20 L tank, the glutamic acid yield was (83.6 g/L) 10.0% higher than before optimization. The results of sensory evaluation of the seasonings prepared by fermentation with batch replenishment showed that the freshness of the fermented seasonings was significantly improved (P<0.05), the bitterness was significantly reduced (P<0.05), and the overall taste was more delicious and flavor harmonized. The findings greatly enhance the utilization value of soybean isolate protein.