Abstract
Sufu is a traditional fermented soybean food produced in China. However, the microbial compositions and metabolites of different types of sufu have not been studied in detail. Accordingly, in this study, we evaluated the differences in bacterial communities and metabolites between commercial red sufu (RS) and white sufu (WS). Principal coordinate analysis and the unweighted pair group method with arithmetic means analysis of 16S rRNA genes revealed that the bacterial community structures of RS and WS differed dramatically. At the phylum level, the relative abundances of Firmicutes and Proteobacteria were significantly different between RS and WS (P < 0.01). Moreover, the abundances of Lactococcus and Tetragenococcus genera were significantly different between RS and WS (P < 0.01). Among metabolites, most free amino acids, few of volatile flavor compounds, and some organic acids showed significant differences between RS and WS (P < 0.05). Additionally, correlations between microbiota and metabolites were determined. Aggregated boosted tree analysis showed that formic acid had the highest relative influence (20.27%) on bacterial community diversity (Chao 1), following by arginine (5.38%), propanol (4.57%), oxalic acid (4.46%), and hexanol (4.43%). Moreover, Streptococcaceae and Moraxellaceae had the highest relative influence on the concentration of formic acid (12.84% and 8.75%, respectively). The profiles obtained in this study improve our understanding of the relationships between bacterial flora and metabolites in different types of sufu. These findings may help us interpret the roles of bacterial communities in the flavor and characteristics of sufu.
Highlights
Sufu is a traditional fermented soybean food in China that shares similar shapes, textures, and fermentation mechanisms with cheese (Xie et al, 2018)
The bacterial abundances of the 16 sufu samples were enumerated by counting viable cells on Plate Count Agar (PCA)
The results showed that Lactococcus were positively correlated with volatile flavor compounds (VFCs) and organic acid, but negatively related to amino acid
Summary
Sufu ( called “oriental cheese”) is a traditional fermented soybean food in China that shares similar shapes, textures, and fermentation mechanisms with cheese (Xie et al, 2018). RS contains red colorant (angkak), whereas WS is free of colorant (Ho et al, 1989; Han et al, 2001b) These two types of sufu contain different contents of metabolites, such as free amino acids (FAAs), organic acids, and volatile flavor compounds (VFCs; Han et al, 2001b, 2004b; Xie et al, 2018, 2019), and show differences in lactic acid bacteria (LAB) compositions (Han et al, 2001a). The dressing mixture of RS mainly consists of salt, angkak (red kojic rice), alcoholic beverage, sugar, and flour or (soybean) paste and some spices. Exploration of the relationships between microbial communities and metabolites is crucial for improvement of the quality of sufu (Huang et al, 2018; Xie et al, 2018)
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