Study On The Relationship Between Ethyl Carbamate Precursors And Microorganisms In Soy Sauce

Ethyl carbamate(EC)is one of the most common compounds in fermented food,which has been proved to be carcinogenic.Based on the main soy sauce producing area of guangdong province,this paper investigated the current situation of EC content in soy sauce sold in guangzhou.In this paper,the dynamic changes of microbial flora during the fermentation of soy sauce were studied,and the microbial flora related to EC precursor substances in soy sauce was analyzed based on the physical and chemical properties and the changes of EC precursor substances during the fermentation of soy sauce.The test results are as follows:(1)the EC content in 35 soy sauce samples sold in guangzhou was analyzed,and the results showed that the EC content in the soy sauce mainly ranged from 0 to 20 g/kg,accounting for 82.86 % of the total samples,indicating that most of the soy sauce sold in guangzhou was safe.Considering that the EC content in soy sauce is higher than 20 g/kg,which accounts for 17.14%,and the EC content in one sample is higher than 100 g/kg,the EC problem in soy sauce cannot be ignored.The content of EC in super grade soy sauce is obviously higher than that in other grades,which may be related to its technology.There are obvious differences in the content of EC in soy sauce from different manufacturers,which may be related to the different fermentation time,sterilization process and preparation process of each soy sauce brewing factory.(2)the bacteria and fungi in soy sauce fermentation were analyzed at the level of genus and species respectively.The results showed that the bacterial flora in the sauce mash belonged to 5 phyla and 41 genera.In the fermentation process of soy sauce,weisiella is the dominant bacteria,the proportion has been maintained between 46 % and 51 %,and relatively stable.In addition,the abundance of bacillus,lactobacillus and klebsiella was relatively high during the whole fermentation process.At the species level,bacteria are not well matched.Fungal flora in mash belongs to 3 phyla and 12 genera.In the first 11 days of soy sauce fermentation,aspergillus dominated,and from the 6th day,combined yeast also became the dominant bacteria in the fermentation process.After 42 days of fermentation,candida also became the dominant bacteria in the fermentation process.At the level of species,the fungus with relatively high abundance identified 16 days before fermentation was candida tropialis.After 16 days,the zygotes rougii,the main fermentation yeast,began to dominate.On the 42 nd day of fermentation,salt-tolerant yeast became the fungus with the highest abundance.(3)the changes of pH,content of salt,content of reducing sugar,content of total acid and content of amino acid nitrogen in the whole brewing process of soy sauce were studied,and the dynamic changes of ethyl carbamate and its precursors: urea,arginine,citrulline and ethanol in the fermentation process of soy sauce were analyzed.Ethyl carbamate was detected on the 11 th day of fermentation,after which its content increased slowly and tended to be stable.The change rules of citrulline and arginine were similar,both of which showed that the content of citrulline increased rapidly in the early stage of fermentation and tended to be stable after 11 days.Urea showed an overall downward trend,and the downward trend was gentle after 11 days.The ethanol content has been increasing throughout the fermentation process.The change trend of EC and ethanol content is consistent,which may be due to the high correlation between EC production and ethanol content in soy sauce.(4)the bacteria with positive correlation with ethanol content were mainly the genus of weisiella,the genus of platycoccus and the genus of lactobacillus,while the bacteria with negative correlation were mainly the genus of acinetobacter,pseudomonas and bacillus.The fungi with positive correlation with ethanol content were mainly zygomyces rougei,while the fungi with negative correlation were mainly ascomycota and aspergillus oryzae.The bacteria with positive correlation with urea content were mainly halobacterium,acinetobacter and halomonas.The bacteria with negative correlation were mainly lactobacillus and leuconostoc.Aspergillus oryzae and saccharomyces cerevisiae were the major fungi positively correlated with urea content,while the major fungi negatively correlated with urea content were zygomycosis rougii.The bacteria with positive correlation with citrine content were mainly candida,weisiella and candida,while the negative correlation was mainly acinetobacter,halomonas and halobacterium.The fungi with positive correlation with citrulline were mainly zygomyces rougei,and the fungi with negative correlation were mainly mortierella and Apiotrichum loubieri.The bacteria with the strongest positive correlation with arginine were leuconostoc and lactobacillus,while the bacteria with the strongest negative correlation were halomonas,halobacillus and acinetobacter.The fungi with the strongest positive correlation with arginine content were zygomyces rougei,while the fungi with the strongest negative correlation were sporophora and Apiotrichum loubieri.