Abstract: In order to understand the difference in the quality of traditional fermented soybean paste products, sensory evaluation of fermented soybean paste samples from Changchun of Jilin province, and Huanan, Baoquanling and Heihe of Heilongjiang province (designated as ChangC, HuaN, BaoQL, and HeiH) was carried out by quantitative descriptive analysis (QDA). Meanwhile, microbial community structure was analyzed using high-throughput sequencing and free amino acid composition was detected on an amino acid analyzer; the correlation between them was investigated. The results showed that BauQL was ranked the best of the four samples in sensory evaluation. The microbial community compositions of different soybean paste samples varied greatly, and so did the dominant bacteria and the dominant fungi. The dominant bacteria in HuaN and HeiH were both Tetragenococcus, while those in ChangC and BaoQL were Lactobacillus and Weissella, respectively. The dominant fungus in both HuaN and HeiH was Penicillium; the dominant fungus in ChangC was unclassified-k-Fungi; the dominant fungus in BaoQL was Aspergillus. According to principal component analysis and comprehensive evaluation, the free amino acid contents of these four samples were different. The free amino acid score of BaoQL was the highest, followed by ChangC, and HeiH was the lowest. A partial least squares regression (PLSR) model was used to analyze the correlation between microbial diversity and free amino acid composition of soybean paste. It was found that the species and abundance of the flora had a great influence on the composition and contents of free amino acids, thus affecting the product quality. Free amino acid content was largely influence by the bacterium Weissella and the fungi Millerozym and Aspergillus. The correlation between free amino acids and microbial community composition in soybean paste that we found in this study provides a theoretical basis for the industrial production of soybean paste products.

Key words: fermented soybean paste, microbial community structure, free amino acid, microbial diversity, sensory evaluation