Production of tofu by lactic acid bacteria isolated from naturally fermented soy whey and evaluation of its quality

- One hundred and sixty three strains of lactic acid bacteria were isolated from fermented soy whey.
- L. plantarum JMC-1 strain showed greater capability of acid production and could be used as tofu-coagulant.
- Significant changes were observed in organic acid levels during the fermentation by L. plantatum JMC-1.
- The content of lactic acid was the highest among the organic acids in fermented soy whey.
- Compared to bitter tofu and gypsum tofu, JMC-1 tofu had a better quality attributes.

Fermented soy whey (FSW) is a traditional tofu coagulant used extensively in China. In this study, 112 Lactobacillus spp., 18 Streptococcus spp. and 33 yeasts were isolated and identified from naturally fermented soy whey (NFSW). Lactic acid bacteria were found as the major effective strains, and 7 lactic acid bacterial strains could produce enough acid to coagulate soy milk. The pH values and acid production were also monitored during fermentation. The JMC-1 strain showing Gram-positive and rod-shaped was determined to have a high acid-producing activity among the 7 strains. API 50 CHL strip and phylogenetic analysis of 16S rDNA gene sequence demonstrated that the JMC-1 strain was identified as Lactobacillus plantarum. Lactic acid and acetic acid were the major organic acids in fermented soy whey, which increased during the fermentation. High-performance liquid chromatography revealed that the concentrations of these acids increased significantly as fermentation time was prolonged. Compared with CaSO4 tofu and MgCl2 tofu, the tofu prepared by L. plantarum JMC-1 was of better quality in terms of sensory evaluation, texture, yield, and retention capacity.