Effects Of Different Salt Concentrations On The Bacterial Community Structure And Quality During The Fermentation Process Of Traditional Sichuan Pickled Cabbage

With the traditional Sichuan pickled cabbage as the object,the effects of 2%,5% and8% different salt concentrations on the structure of bacterial community and quality in the fermentation process were studied.The main results are as follows:1.The lower the salt concentration,the faster the p H value decreases and the total acid increases during fermentation of Sichuan pickled cabbage,the lower the reduced sugar and glucose content.The occurrence of times of 2%,5%and 8% salt concentrations of nitrites were 3 d,5 d and 7 d respectively,and the highest peaks of 8% salt concentrations were highest at 15.26±2.59 mg/kg.After entering the maturity stage,the nitrite content was at a low level,with the highest at 8.71±1.49 mg/kg.The lower the salt concentration,the faster the growth rate of lactic acid bacteria,the faster the coliforms disappears.The amount of yeast in the 5-10 d stage of fermentation of 5% and 8% salt concentrations of pickled cabbage was higher than 2% salts concentration.2.The cultureable method study the effect of different salt concentrations on the lactic acid bacteria community structure during the fermentation process of Sichuan pickled cabbage,and 563 lactic acid bacteria strains were isolated by MRS medium,and the types of lactic acid bacteria were more abundant in the pickled cabbage with low salt concentration,but the difference in diversity index was not significant.Lactobacillus pentosus dominates fermentation.2% salt concentration by Lactococcus lactis,Lactobacillus pentosus and Leuconostoc initiated fermentation,5% and 8% salt concentration by L.pentosus and Weissella start fermentation.3.The high-throughput sequencing method studied the effect of different salt concentrations on the structure of bacterial community structure during the fermentation of Sichuan pickled cabbage,and the results showed that the bacterial diversity index in the 2%and 5% salt concentration was significantly higher than that of 8% salt concentration.Pickled cabbage is mainly produced by Lactobacillus,Lactococcus and Leuconostoc start fermentation,Lactobacillus is gradually increased and dominated,Enterobacter is the highest relative abundance when fermentation 1 d.8% Salt concentration compared with 2%and 5% salt concentration,the relative abundance of Lactobacillus is higher,while the relative abundance of Lactococcus and Leuconostoc is lower.4.Lactic acid is the highest content of organic acid,the lower the salt concentration,the higher the content of lactic acid and acetic acid.When fermentation 0-5 d,8% salt concentration of Sichuan pickled cabbage ethanol content is lower than 2% and 5% salt concentration,but in fermentation 7-10 d,8% salt concentration ethanol content increased and exceeded 2% and 5% salt concentrations.A total of 15 free amino acids were measured,the total content of free amino acids showed a first rise and then decline,fermentation 10 d and then rebounded trend,2% and 5% salt concentration content is significantly higher than 8% salt concentration.A total of 81 volatile flavor compounds were detected.After entering the maturity stage,8% salt concentration in the late fermentation of the main volatile flavor components are mainly sulfur-containing compounds,esters and alcohols,2%and 5% salt concentrations in late fermentation sulfur compoundcontent content is higher,its main volatile flavor components contain sulfur-containing compounds,esters,alcohols,aldehydes,acids and phenolic substances.