Dynamics of Physicochemical Properties, Flavor, and Microbial Communities of Salt-Free Bamboo Shoots during Natural Fermentation: Correlation between Microorganisms and Metabolites

Sour bamboo shoot is a Chinese fermented vegetable with unique flavors and is favored by local consumers. In this study, at different fermentation times, the texture of bamboo shoots and the changing rules of pH, titratable acid (TA), reduced sugar, and nitrite in bamboo shoot fermentation broth were explored. Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to investigate the dominant aroma compounds. 16S rRNA high-throughput sequencing technology (HTS) was employed to investigate the core microbial communities. The results show that the chewiness, fracturability, hardness, and pH decreased, while TA increased during the 60-day fermentation. The contents of reducing sugar and nitrite peaked on the 14th day of fermentation and then decreased. A total of 80 volatile compounds were detected during sour bamboo shoot fermentation, with 2,4-Di-tert-butylphenol having the highest concentration. Among them, 12 volatile compounds (VIP &ge: 1) were identified as characteristic aroma substances of sour bamboo shoots. The dominant bacterial phyla in sour bamboo shoots were Firmicutes and Proteobacteria, while Bacillus and Acinetobacter were the dominant genus. Correlation analysis showed that Firmicutes exhibited a positive correlation with 3,6-Nonadien-1-ol, (E,Z)-, Oxalic acid, isobutyl hexyl ester, and (-)-O-Acetylmalic anhydride, whereas Bacillus exhibited a negative correlation with Silanediol, dimethyl-, and Oxime-, methoxy-phenyl-. A detailed picture of the microbial community of fermented bamboo shoots has been provided by this study, and it may provide insight into the Chinese traditional fermented vegetable microbial structure.