Changes In Microbial Community Structure And Flavor Compounds During The Fermentation Of Congee

In order to explore the structural changes of microbial flora in the fermentation process of acidic gruel and its impact on the flavor substances of acidic gruel,this study took acidic gruel(fermented with introduction)in the fermentation process as the research object,detected and analyzed the dynamics of bacterial and fungal community by high-throughput sequencing technology,and monitored the changes of flavor components at different fermentation time points by gas chromatography-mass spectrometry,electronic nose technology and electronic tongue technology,The correlation between them is analyzed.The main research contents and results are as follows:(1)The changes of physical and chemical properties during the fermentation of acidic gruel were detected,and it was found that the acidity,soluble solids and protein contents of acidic gruelsamples showed a stepwise upward trend with the progress of fermentation,and the total sugar content first increased and then decreased.With the prolongation of fermentation time,the L~* value of acidic gruel showed a decreasing trend,and the a~* value and b~* value increased slowly.(2)The Illumina Miseq sequencing technology was used to analyze the changes in the microbial community structure during the fermentation process of acidic gruel.The results showed that the bacteria in the acidic gruel samples at different fermentation stages were mainly Lactobacillus and Kosakonia,Enterococuss.The fungi are mainly composed of Yarrowia,Dipodascus and Pichia.The relative content of dominant bacterial genera fluctuated significantly during the whole fermentation process.The bacterial species involved in fermentation were more than fungi.Lactobacillus,Yarrowia and Dipodascus were always the absolute dominant bacterial genera.(3)The results of detecting the congee during fermentation by Gas Chromatography Mass spectrometry showed that esters and alcohols were the main flavor substances,and the esters showed a trend of rising and then falling during the whole fermentation process.The alcohols showed an increasing trend.The volatile acids showed an increasi ng trend with the extension of fermentation time,while the aldehydes showed a decreasing trend followed by an increasing trend.Among them,ethyl acetate,eucalyptol,nonanal,ethyl heptanoate and acetic acid were the key flavor substances.In addition,a total of 16 amino acids were detected from the samples,and the total amino acid content at 48 h of fermentation increased to twice that at 0 h of fermentation,with the highest content of glutamic acid and aspartic acid.Using the electronic nose technique,it was found that the sensors with high response intensity to the sour porridge samples included W5S(Nitrogen oxides),W1S(Methyl group)and W1W(Sulfide Sensitive).For taste,the strongest response signals were found for sour porridge sour,sweet and salty.(4)Statistical analysis of the correlation between the dominant microbial genera and key flavor substances during sour porridge fermentation revealed that Lactobacillus,Kosakonia,Enterococcus,Cronobacter,Dipodascus and Pichia played an active role in the production of key flavors.