| Stinky mandarin fish is a characteristic food made by traditional fermentation technology with unique flavor and large scale of industry.However,its flavor substance and its formation mechanism are still worth further study.Microbe is a key factor that influences the quality of the smelly mandarin fish flavor,6 smelly mandarin fish as the research object,based on the identification of the smelly mandarin fish flavor substances and microorganisms,through salt resistance,antibacterial,capacity of lipase,protease,such as evaluation index,select three high-quality fermentation strains,lactobacillus casei,lactobacillus casei,and summarized the yeast,single strain and its strengthening fermentation was studied in the smelly mandarin fish flavor formation,the influence of the results are as follows:(1)GC-MS was used to identify the flavor substances of six kinds of mandarin fish,and the odor activity values were calculated by using the threshold values of literature.It was found that acetic acid,indole,trimethylamine,linalol,1-octene-3-alcohol,propionic acid,n-hexanol,n-hexanal and other characteristic common flavor substances.Orthogonal partial least squares analysis was performed on electronic nose results and GC-MS results by using Simca software to find the correlation between volatile substances and electronic nose data,and a regression model was established for key flavor substances such as trimethylamine,indoles and linalol and electronic nose data.(2)High-throughput microbial sequencing was performed on six types of smelly mandarinfish,and it was found that the common functional microorganisms of The mandarinfish,such as Free-roaming coccus,Clostridium,Lactobacillus,and Hufnias,were respectively 38.02%,14.46%,14.99%,and 3.01%.Through the correlation analysis of the R software Complex Heatmap package,the Heatmap map was made,and it was found that the microorganisms with significant positive correlation with the acetic acid of the key flavor substances were Shivella and Enterococcus.Lactobacillus was significantly positively correlated with 1-octenol.Bacteroides,Clostridium,and Lactobacillus were significantly positively correlated with n-hexanol.(3)In order to obtain excellent microbial strains,the microbes such as yeast,lactobacillus and bacillus in stinky Mandarin fish were isolated and purified with specific properties.The results showed that 22 strains of lactic acid bacteria,2 strains of yeast and 3 strains of bacillus were isolated from stinky Mandarin fish.Lactic acid bacteria is the culturable dominant bacteria of stinky Mandarin fish,which verified the results of highthroughput sequencing.Three excellent strains,Lactobacillus casei,Lactobacillus paracei and Pichia pastoris,were screened by evaluating the growth characteristics,stress resistance,salt tolerance,lipase production,protease production and bacteriostasis of the isolated strains.(4)A single-strain fermentation model for the optimal bacteria Lactobacillus casei,Lactobacillus paracei and yeast was established.It was found that the yeast treatment group produced such flavoring substances as secooctanone,linalool,3-octanol,1-nonanol and lauryl alcohol.The flavoring substances such as linalool,3-octyl alcohol and trimethylamine were produced in the group treated by Lactobacillus casei.Lactobacillus paracei produced nonanoic acid,ethanol,diisobutyl phthalate and other flavor substances.These results preliminarily revealed the relationship between the formation of microbial and flavor substances in stinky Mandarin fish.(5)The fermented system of enhanced stinky Mandarin fish with different preferred strains was established to explore the feasibility of standardized production of stinky Mandarin fish.The study found that yeast plays a key role in the main flavor substances,such as 1-octene-3-alcohol,2-methyl-butyric acid,n-hexaldehyde,trimethylamine and indole.Lactobacillus casei plays a key role in the production of trimethylamine,acetic acid,butyric acid,4-methylpentanoic acid and 1-octene-3-alcohol.Lactobacillus paracornis plays a key role in the production of indoles,1-octene-3-alcohols,anisole brain,4-methyl-pentanoic acid and other flavor substances.At the same time,it can be seen that the enhanced inoculation of the three kinds of bacteria can reduce the content of trimethylamine in stinchy mandarin fish.To sum up,the above research results provide a theoretical basis for the preparation and standardized production of stinky Mandarin fish. |
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