Analysis of the main flavor compounds and bacterial flora in the fermentation process of stinky tofu brine

Taking the brine used for making stinky tofu produced by a certain company in Hunan Province as the research object, the physicochemical properties of the brine were determined, and the quality differences of the brine samples (labeled as Ⅰto Ⅵ) with different fermentation time (454 d, 455 d, 456 d, 462 d, 463 d and 829 d) were investigated. The volatile flavor components of the brine related to the production of stinky tofu were analyzed by using solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS), and the bacterial flora of the brine at different fermentation stages were analyzed by 16S rDNA sequence. The results indicated that a total of 115 volatile flavor substances were identified in the samples of stinky tofu brine, mainly including acids, esters, phenols, indoles, alcohols, ethers, ketones, etc. A total of 10 dominant bacterial genera were identified in the brine, including Sporanaerobacter, Clostridium sensu stricto 7, Clostridium sensu stricto 1, Clostridium sensu stricto 15, Caproiciproducens, Prevotella, unclassified f Clostridiaceae, Haloimpatiens, Streptococcus and Caldicoprobacter. Among them, Sporanaerobacter, Clostridium sensu stricto 1 and Caproiciproducens were the main dominant bacterial genera in the brine. The results showed that for sample No.Ⅱ (fermentation time 455 d), the salt content was 3.01%, and the nitrite content was the lowest of 0.08 mg/kg. The contents of amino acid nitrogen and total acid were relatively high, which were 0.73 g/100 ml and 14.17 g/100 ml, respectively. The relative content of the main volatile flavor substance methyl phenol was the highest of 78.20%. The research results could provide scientific basis for the quality control of brine in the production of stinky tofu.