| The flavor quality of traditional Zhenjiang aromatic vinegar is easily influenced by the environment,which leads to the difference of vinegar quality in four seasons.In the samples of vinegar pei collected in the four seasons fermentation process were high-throughput sequencing,and the environmental factors,organic acids,free amino acids and volatile flavor substances in the four seasons were analyzed,and the differences of microorganisms and flavor substances in vinegar fermented grains in different seasons were analyzed.By analyzing the correlation between environmental factors in four seasons and microorganisms and flavor substances in vinegar fermented grains,the environmental factors that have significant influence on flavor substances and microorganisms in different seasons were anchored.By analyzing the correlation between microorganisms and flavor substances in vinegar fermented grains in different seasons,the main difference microorganisms related to flavor substances in different seasons were determined,which provided theoretical basis and technical support for clarifying the mechanism of flavor quality difference of traditional Zhenjiang aromatic vinegar in different seasons and improving the flavor quality of Zhenjiang aromatic vinegar in solid state fermentation.The main results are as follows:1.The contents of organic acids,free amino acids and volatile flavor substances during the four seasons fermentation were analyzed.It was found that the total contents of acetic acid in spring,lactic acid in winter and succinic acid and pyroglutamic acid in autumn were the highest.In terms of amino acids,Zhenjiang aromatic vinegar is the most delicious and sweet in autumn,the most bitter in winter,and the quality difference between summer and other seasons is the biggest.Among the volatile flavor compounds,62 flavor compounds were detected in vinegar fermented grains of the four seasons,and the volatile flavor compounds in autumn were more abundant than those in other seasons.By partial least squares(OPLS)analysis,it was found that the main volatile flavor compounds in the fermented grains of Zhenjiang Aromatic Vinegar were isooctanol,γ-nonlactone and ethyl acetate.The main difference organic acids are oxalic acid and pyruvic acid;The main difference amino acids are phenylalanine,alanine and glutamic acid.2.The bacterial and fungal communities in the fermented grains of Zhenjiang aromatic vinegar during acetic acid fermentation were analyzed by high throughput sequencing.It was found that the absolute dominant microorganisms at the phylum level were chlamydia,proteus and ascomycetes;at the genus level,the absolute dominant microorganisms were Lactobacillus,Acetobacter,Yeast and Aspergillus;at the species level,the absolute dominant microorganisms were Lactobacillus food,Lactobacillus acidophilus and Acetobacter pasteureus.In addition to dominant bacteria such as Acetobacillus pasteuricus and Lactobacillus food,differential bacteria and fungi such as Lactobacillus acidophilus,Bacillus subtilis,Aspergillus aspergillus,Rhizopus occultus,and Pichia pastoris also play a crucial role in the fermentation process.3.The internal and external environmental factors such as temperature,humidity,reducing sugar,p H and total acid of Zhenjiang aromatic vinegar fermented grains in four seasons were analyzed.It was found that in terms of temperature,the internal and external temperatures of Zhenjiang aromatic vinegar fermented grains were higher in summer,and the external temperatures of Zhenjiang aromatic vinegar fermented grains were lower in spring and winter,with obvious fluctuations.In terms of humidity,the environmental humidity in spring and winter is obviously lower than that in spring and autumn;In terms of reducing sugar content,the content in summer after fermentation is the highest compared with other seasons;In terms of total acid,the sequence of total acid content after fermentation is: winter >spring > autumn > summer.4.The correlation analysis between environmental factors and microorganisms shows that the main environmental factors affecting microbial structure composition are room temperature and p H,in addition,the microbial structure composition in spring is highly correlated with reducing sugar,humidity,total acid,room temperature and other environmental factors;The microbial structure composition in summer,autumn and winter is highly correlated with environmental factors such as total acid,reducing sugar and fermented temperature.The correlation analysis between environmental factors and flavor substances showed that the main environmental factors affecting the structural composition of flavor substances were p H and total acid,and the structural composition of flavor substances in spring was highly correlated with environmental factors such as fermented temperature and reducing sugar.The structural composition of flavor substances in summer and autumn is highly correlated with environmental factors such as reducing sugar,fermented temperature,room temperature and humidity.The structural composition of flavor substances in winter is highly correlated with environmental factors such as reducing sugar,fermented temperature and room temperature.The correlation analysis between microorganisms and flavor substances showed that the bacteria with high correlation with organic acid composition were Lactobacillus alimentarius,Streptococcus parasanguinis,and the fungi were Aspergillus caesiellus,[Pichia] Myanmar,lavodon ambrosius,etc.Bacteria with high correlation with free amino acid composition include Leuconostoc lactis,Lactobacillus brevis,Prevotellaceae bacterium,and fungi include Xeromyces bisporus,Keissleriella bambusicola,etc.Bacteria with high correlation with volatile flavor components are Tilletia vankyi,Sarocladium strictum,Malassezia furfur,etc.Fungi include [Pichia] myanmarensis,Peniphora Crassitunica,Aspergillus flavus,etc. |
