Study On The Change Of Microorganism And Related Indexs In Fermentation Of Allium Chinense With Different Salinity

Allium chinensis is a plant of Allium chinense in the family liliaceae.It is mainly cultivated in southern China.Hunan is a major province of planting and processing a.chinense.The export volume of canned and processed a.chinense accounts for more than 40% of the national total,mainly to Japan.Hunan province,the production of pickled a.chinense is mainly concentrated in Xiangyin county,its processing technology is generally clean and dry fresh a.chinense after a period of high salt pickling after desalination,enzyme inactivation,seasoning,filling sterilization into products,the process of pickling microbial community will cause changes in flavor and other indicators.This thesis by adding different salinity(5%,10%,15%,20%)for a.chinense,study its fermentation from15 to 90 days different times volatile composition and the change rule of physiochemical parameters through the analysis of microbial diversity and purification of lactic acid bacteria strengths,to explore the mechanism of a.chinense fermentation process and the quality change,tracking main indicators of change,in the process of fermentation for a.chinense processing production and provide theoretical guidance to establish the system of quality standards,the specific research results are as follows:1.The volatile components of a.chinense with different salinity during fermentation were analyzed by solid phase microextraction and gas chromatography-mass spectrometry(gc-ms).The results showed that the main volatile aroma components included alcohol compounds,ester compounds,acid compounds and sulfur compounds.Of sulfur-containing compounds is the main components of the excitant odour of a.chinense,including dimethyl disulfide,dimethyl sulfide,Methyl(1-(methylthio)propyl] persulfide,Trisulfide,(e)1-1-propen-1-yl propyl,3,6-diethyl 1,2,4,5-tetrathiane,etc.Fermentation chinense produced the most flavor substances at a salinity of 5%.2.The total acid,total sugar,pectin and organic acid in the fermentation process of a.chinense at different salinity and at different time were measured and it was found that the lower the salinity was in the fermentation process,the higher the total acid was.The content of total acid in a.chinense at a salinity of 5% increased from 15 to 45 days to 6.62 g/kg,then decreased and stabilized at 4.63 g/kg.The content of total acid in a.chinense at a salinity of 10%,15% and 20% increased from 15 to 30 days and remained stable in the later period.The contents of total sugar and pectin in a.chinense with different salinity showed a decreasing trend during fermentation,and the lower the salinity,the faster the decrease.Through the determination of six organic acids in the fermentation process,it was found that the change trend of organic acids in different salinity was not the same,and lactic acid was the main organic acid in the fermentation process of a.chinense.Tartaric acid was not detected during fermentation.Lactic acid was increasing all the time,and the rate of increase of 5%salinity was significantly higher than that of the other three salinity(P < 0.01).The content of acetic acid increased first and then decreased and tended to be stable.At the 15 th day,the content of acetic acid was the highest and the content of 5% salinity was significantly higher than that of other salinity(P < 0.01).The content of citric acid showed a decreasing trend and the change was not significant(P > 0.05).The content of oxalic acid increased first and then decreased.The higher the salinity was,the higher the content was.The lower the salinity,the lower the content of malic acid.3.The changes of microbial communities in a.chinense during fermentation with different salinity were compared.A total of 6118962 valid data including 20363 OTUs were obtained by 16 S r RNA high-throughput sequencing technique.The composition of the bacterial community changes throughout the fermentation process.The higher the salinity,the more diverse the bacterial flora and the more abundant the bacterial species.PCA analysis showed that the bacterial flora of chinense at 5% salinity was significantly different from that of other salinity at 15-30 days fermentation.The bacterial flora of a.chinense was similar to that of a.chinense at a salinity of 10% after fermentation for 45-90 days.Based on the analysis on the level of phylum,it was found that Proteobacteria was the dominant phylum in the fermentation process,followed by Firmicutes and Bacteroidetes.On the genus level,Lactobacillus was always dominant in a.chinense with a salinity of 5%,and its content was more than that of other genera,making it an absolute dominant genus.In a.chinense with 10% salinity,the dominant bacteria were Lactobacillus,Acetobacter and Weissella,respectively.The dominant bacteria in a.chinense(15% salinity)were Acetobacter and Staphylococcus.The dominant bacterium in a.chinense with 20%salinity was Acetobacter.4.The main lactic acid bacteria in the pickling process of a.chinense were obtained by pure culture method.The lactic acid bacteria in the fermentation process were determined and purified by combining MRS culture medium and calcionolysis ring while sampling and analyzing the diversity through high-throughput sequencing technology.A total of 17 strains of lactobacillus were isolated,and the microscopic observation was dominated by bacillus.The 16 S r DNA identification results showed that the 17 strains were lactobacillus plantarum,lactobacillus bacillus bacillus and lactobacillus pentose,respectively.The lactic acid bacteria were counted in each fermentation period and it was found that the total number of lactic acid bacteria was1.2×106CFU/m L at the 60 th day of a.chinense with a salinity of 5%.