Study On The Effect Of Microorganism On The Production Of Biogenic Amines During Sufu Fermentation

Sufu is a traditional fermented bean product favored and loved by consumers.It has the unique flavor and rich nutrition with a wide market consumption base.However,the content of biogenic amines in sufu is relatively high,and the impact of microorganisms on biogenic amines in the process of sufu production is not clear,which has become a bottleneck restricting the industrial development of sufu,seriously affecting market consumption and quality improvement.In this study,the succession of microbial community structure,the production rule of biogenic amines,and the correlation between microbial community and biogenic amines during sufu fermentation were studied,and the aminogenic bacteria were isolated,their metabolism under different conditions was studied,in order to reveal the microbial pathway of the production of biogenic amines in sufu and lay a foundation for the control of biogenic amines in sufu.The main results are as follows:1.The high-throughput sequencing technology was used to study the succession of bacteria and fungi during the fermentation of sufu.For the bacterial community structure,the results showed that in the tofu the relative abundances of norank_c_Cyanobacteria and Kurthia were 72.80%and 20.11%,respectively;the dominant bacteria in the pehtze and salted pehtze were Acinetobacter;in the post fermentation process,Acinetobacter,Enterococcus and Streptococcus were the main genera.For the community structure of fungi,the dominant genera were Trichosporium,Aspergillus and Actinomyces,and Actinomyces accounted for a relatively high proportion(44.74%)in the pehtze;in the process of post bottling fermentation,the sum of Aspergillus and Monascus accounted for more than 95%,becoming the dominant fungi in the post fermentation stage.2.The changes of biogenic amines and main components during sufu fermentation were studied.It was found that no biogenic amines were detected in the tofu.In the pre-fermentation process,the growth of biogenic amines was not significant.The main biogenic amines in the pehtze and salted pehtze were phenylethylamine and cadaverine.When the salted pehtze was fermented with soup,the content of all biogenic amines increased,and tryptamine and spermidine began to appear.As the most toxic amine,histamine was detected in high concentration(105.86 mg/kg)on the 28th day of fermentation.With the progress of fermentation,the content of histamine gradually increased to 210.52 mg/kg in the end of fermentation,becoming the main biogenic amine.In general,the content of biogenic amines was higher in the post fermentation.In the process of fermentation,the activity of alkaline protease was lower than that of neutral protease,and the content of polypeptide was increasing until the fermentation reached 14.59 g/100g(dry basis).3.Partial least square regression(PLSR)and Pearson correlation analysis were used to clarify the correlation between biogenic amines and bacterial community composition,protein degradation related indicators.The results showed that there was a certain correlation between bacteria and biogenic amines,for example,histamine had a good correlation with and unclassified_f_Enterobacteriaceae;phenylethylamine and tryptamine had a certain correlation with Enterococcus,Streptococcus and Staphylococcus.The Pearson correlation analysis showed that there was a significant positive correlation between the synthesis of biogenic amines and polypeptides,amino nitrogen and the activity of neutral protease,and the correlation coefficients were all above 0.8,indicating that the synthesis of biogenic amines was closely related to the degree of protein degradation.4.The strains producing biogenic amines in sufu were studied.59 strains of biogenic amines producing strains were screened by plate color method combined with chromatography.The capacity of biogenic amines producing strains under different temperature,pH,amino acid,carbon source,ethanol and salt content was measured.The actual fermentation experiment was carried out.The results showed that the biogenic amines content of the fermentation group inoculated with biogenic amines producing strains was significantly higher than that of the control group,among which histamine,tryptamine and cadaverine were mainly produced by Bacillus tropicus inoculation group,while more tyramine and tryptamine were produced by Bacillus subtilis inoculation group.