Study On The Microbial Diversity And Quality Of Natural Fermented Sufu

Fermented bean curd is a common fermented soy product.At present,the industrialized production of fermented bean curd is basically mature.The focus of attention has been put on the industrial production of fermented bean curd.There are a large number of research reports on optimizing fermented bean curd technology at the level of pure fermented bean curd,and there are few researches on naturally fermented sufu.However,as far as the actual situation is concerned,the production method of natural fermentation still exists.Due to the complicated interaction between microorganisms in the fermenting process of fermented bean curd,and the uncontrollability of the production and processing environment and operators,this production method will As a result,the quality of fermented bean curd products cannot be well tested and controlled.In response to this phenomenon,this study conducted studies on microbial diversity,colony structure succession changes,biogenic amine production and changes in physical and chemical indicators of naturally fermented sufu on the market,in order to provide a theoretical basis for the monitoring,evaluation and quality improvement of naturally fermented sufu,The main conclusions of the research are as follows:1.Each fermented bean curd sample has its own unique micro-ecological environment.Various factors such as production environment and production process will have a certain impact on the formation of fermented bean curd micro-ecology.Even samples from the same area are different,but between samples There is also a similar situation.There are 19 bacterial genera shared by all samples and 5 fungal genera shared.Basically,they are the flora that are often detected in fermented foods,such as Acinetobater,Comamonas,Empedobacter,Enterococcus,Lactococcus,Leuconostoc,Pseudomonas,Streptococcus,Weissella,Aspergillus,Wallemia,etc.At the same time,there are some uncommon flora in sufu,such as Stenotrophomonas,Dipodascus,etc.The presence of potentially harmful bacteria such as Shigella in some samples indicates that the hygienic conditions of naturally sufu deserve attention.2.During the natural fermentation of fermented bean curd,the composition of the microbial community changes with the fermentation time.There are significant differences in the microbial composition at different stages,and the fungal composition at each stage is relatively simple.Some bacterial genera only exist in the latter stage,indicating that new species appear during the fermentation process,and the dominant colonies in different stages are different.Some bacterial genera account for a larger amount in the previous stage,but as the fermentation progresses,the abundance Become smaller.In the first stage of fermentation,the main bacteria are Acinetobacter,Lactococcus,Pseudomonas,and the main fungus are Guehomyces and Candida;The main bacteria in the second stage are Myroides,Comamonas and Pseudomonas,and the main fungus is Guehomyces And Candida;the main bacteria in the third stage are Lactococcus and Pectobacterium,and the main fungus are Alternaria and Gibberella.The main genus of bacteria and fungus in different stages is different,which is not only beneficial to fermentation,but also may affect the quality of the product.Acinetobacter,Lactococcus,Pseudomonas,Myroides,Comamonas and yeast are microorganisms throughout the fermentation process.3.There are significant differences in the quality of different naturally fermented sufu samples.The presence of biogenic amines was detected in all samples.Except for 5 samples where spermidine was not detected,the detection rate of other types of biogenic amines was 100%.Amine and histamine are the three types of biogenic amines with the highest detected content.The total amine content of all samples is below 1000 mg/kg,but compared with other fermented soy products,the content of histamine in naturally fermented sufu is higher,Both exceeded 100 mg/kg.The content of biogenic amines in samples from different regions varies greatly.4.The relationship between the physical and chemical indicators in the sufu and the content of various types of biogenic amines can be known through Pearson correlation analysis.Total acid has a very significant positive correlation with tyramine(0.714),and amino acid nitrogen has a significant positive correlation with putrescine(0.865)and cadaverine.There is a very significant positive correlation between amine(0.95)and tyramine(0.721),and cadaverine is highly positively correlated with putrescine(0.911)and tyramine(0.812).5.During the natural pre-fermentation of sufu,the water content decreased by7.93%,the protease activity increased by 13.41 U/g,the total acid content increased by 0.777 g/100g,the amino acid nitrogen content increased by 0.423 g/100g,and the hardness decreased by 75%,elasticity decreased by 10.63%,adhesiveness decreased by 78.11%,brightness decreased,redness and yellowness increased,and the total number of colonies was between 10~5 CFU/g?10~9 CFU/g.