High temperature soybean fermentation using microbial strains isolated at high temperatures

Microbial strains isolated from the soil in Korea were used to ferment soybeans. Volatile aldehyde concentrations of soybeans fermented at 50degreesC were higher than those fermented at 60degreesC. Soybeans fermented for 72 hr at 50degreesC or 48 hr at 60degreesC with HT-24 strain scored highest in sensory evaluation compared to commercially produced Chungkukjang. Highly viscous residue produced during fermentation reduced growths of Escherichia coli O157:H7 and Listeria monocytogenes by 45 and 5 log CFU/g, respectively. Protease from soybeans fermented with HT-24 strain showed stable activity above pH 8 between 50 and 70degreesC. Our results indicate that the isolated microbial strains may be valuable for improving industrial production of soybean products through high-temperature fermentation.