Abstract: The free amino acid composition and volatile aroma components of fermented soybean made with nine Bacillus strains were analyzed by amino acid analyzer and gas chromatography-mass spectrometry (GC-MS) and the obtained data were analyzed by factor analysis with SPSS software. The results showed that all the Bacillus strains played an essential role in the formation of free amino acids and flavor substances during soybean fermentation. The amino acid contents and aroma-producing abilities of the different fermented samples were different. Through factor analysis, it was concluded that esters, alcohols and aldehydes were the main aroma components in Bacillus fermented soybeans. This study can provide a reference for flavor enhancement of fermented bean products.

Key words: soybean fermentation; Bacillus; free amino acids; flavor