Effect of the bacterial community on the volatile flavour profile of a Chinese fermented condiment - Red sour soup - During fermentation.

Red sour soup (RSS) is a traditional fermented seasoning used by people in Guizhou Province, China. The volatile compounds were detected by gas chromatography ion mobility spectrometry (GC-IMS), while the bacterial community compositions were revealed by 16S sequencing. A total of 70 volatile substances were assessed, and esters, terpenes, and alcohols played a dominant role in RSS. Lactic acid bacteria (LAB) were dominant in the microbial community. During fermentation, multiple volatile flavour substances and various LAB were mainly derived from the secondary fermentation stage. The core bacteria with an important influence on volatile flavour substances were analysed by the Mantel test, identifying Bacteroides, Lactobacillus, Lactococcus, Enterobacteriaceae, Pantoea, Clostridium, Enterobacter, unclassified genera, Caproiciproducens, Nitriliruptoraceae, Halomonas, Bradyrhizobium, Pediococcus, Caulobacteraceae, Weissella, Ligilactobacillus, and Levilactobacillus and et al.. This study provides us with useful information about flavour-generating bacteria among RSS fermentation periods. The abundances of these bacteria may be controlled to enrich the desired flavour metabolites while eliminating unwanted metabolites.

Deep insights into fungal diversity in traditional Chinese sour soup by Illumina MiSeq sequencing.

Sour soup is a traditional condiment in Guizhou Province, China. The purpose of this study was to investigate the differences in the fungi present in 5 types of sour soup (tomato sour soup, chili sour soup, cherry tomato sour soup, spoiled tomato sour soup, and red sour soup made from blended tomato and chili sour soup subjected to secondary fermentation) and to determine the reasons for the deterioration of tomato sour soup by comparing the fungal communities in normal and deterioratedtomato sour soup. A total of 5 phyla were detected in all 5 samples, including Ascomycota (69.38%), Basidiomycota (7.63%), Zygomycota (1.59%), Chytridiomycota (0.01%) and unclassified phyla (21.39%). Ascomycota was the main phylum in each sample except the red sour soup made from blended tomato and chili sour soup subjected to secondary fermentation. That sour soup contained many unrecognized phyla. At the genus level, there were major differences among the different samples. Dekkera spp. and Pichia spp. were the main dominant fungus in tomato sour soup, Saccharomyces spp. and Pichia spp. were the dominant fungus in chili sour soup, and Pichia spp. were the dominant fungus in cherry tomato sour soup. When sour soup went bad, the fungus of sour soup changed greatly, and the unknown fungal genera, Cladospora spp., Saccharomyces spp. and Emericella spp. became the dominant fungal genera. In addition, after the secondary fermentation of tomato and chili sour soup mixed with garlic and ginger, the fungal genera of the base fermentation were replaced by unknown fungal genera. Moreover, there were various spoilage fungi in sour soup, which indicated that there were safety risks in naturally fermented sour soup and should be further controlled. This study revealed the fungal flora in sour soup made from different vegetables and compared the fungal diversity of spoiled and normal tomato sour soup and thereby provided a basis for understanding the fungal diversity of sour soup in China and guiding the production of sour soup.