Flavour Compounds Of Atoma Producing Yeast And Its Application In Fuqu Liquor

Fuqu baijiu has the characteristics of high liquor yield,but its flavor substance is relatively thin,which seriously affects the quality of Fuqu baijiu.Therefore,it is of great significance to breed the flavor-producing microorganisms and develop the new process of fuqu liquor production suitable for the flavor-producing microorganisms for the improvement of production efficiency and the development of high quality liquor enterprises.In this paper,the aromatic yeast AY12 1-C and the lactic acid bacterium Pea 30 with high acid and ethanol tolerance were screened from the laboratory bacteria bank.The interaction between the two was revealed through mixed fermentation.On this basis,applying two strains of bacteria in the process of bran koji liquor fermentation,through conditions optimization methods to development of new technology of bran koji liquor,using gas chromatography mass spectrometry technology in determination of optimum technological conditions of bran koji liquor flavor substances,and combining with high throughput sequencing technology to explore microbial community succession law of bran koji wine fermented grains and interaction.The main results are as follows:(1)Selection of fermentation strains.It was found that there was little difference between ethanol production capacity and fermentation capacity,and the ethyl acetate content increased in a gradient manner.In order to achieve the flavor balance of solid Fuqu liquor,yeast AY12 1-C with medium ethyl acetate yield was selected as the subsequent fermentation strain.The fermentation performance of 12 strains of lactic acid bacteria was analyzed.It was found that the alcohol content and ethyl acetate were higher,the alcohol tolerance was stronger,and the yield of lactic acid was the highest.Therefore,Pediococcusacidilactici Pea 30 was selected for subsequent solid state fermentation.(2)Interaction between yeast and lactic acid bacteria.The yeast and lactic acid bacteria were mixed in different proportion and the interaction between yeast and lactic acid bacteria was studied by the change of fermentation index.The increase in the number of lactic acid bacteria slightly inhibited the growth and ester production of yeast.Yeast had inhibitory effects on fermentation indexes such as biomass,p H change and ethyl lactate yield of lactic acid bacteria,but this inhibitory effect weakened with the increase of the number of lactic acid bacteria..(3)Development of fermentation technology of Fuqu liquor under new technological conditions.The fermentation conditions of Fuqu liquor by the co-fermentation of Saccharomyces cerevisiae and Lactic acid bacteria were optimized.Fermentation time,ratio of sorghum to lees,water content of fermented grains before fermentation and so on.The results showed that the optimal conditions were as follows: ratio of sorghum to lees was 1∶4,inoculation of 3% liquid yeast AY12 1-C and 15% Pediococcusacidilactici Pea30,ratio of Fuqu to Daqu was 4∶1,and water intake was about 55%,and fermentation at26℃ for 7 days.The content of ethyl acetate and ethyl lactate was 596.32 mg/L and 96.59mg/L respectively.(4)Analysis of physical and chemical indexes and volatile substances of Fuqu liquor brewed under new technological conditions.Under the optimal technological conditions,the content of lactic acid and titrated total acid in Fuqu liquor increased gradually with time.The volatile components of Fuqu liquor were determined by gas chromatography-mass spectrometry(GC-MS).A total of 64 volatile compounds were detected in all samples,including 35 esters,13 alcohols,5 acids,6 aldehydes and ketones,and 5 phenols.The main volatile substances in fuqu liquor were phenyl ethyl acetate(120.1 μg/m L),iso-amyl acetate(106.88 μg/m L),phenylethanol(4.5 μg/m L),etc.Under the optimal technological conditions,fuqu liquor had the most abundant esters and the highest content(2-15 times higher than the other three groups).(5)Microbial community composition and dynamic changes.The microbial community diversity in 16 samples(four groups)of bran koji Baijiu was determined by high-throughput sequencing technology.Among them,Lactobacillus and Pediococcus are the main dominant bacteria in the four groups of fermented grains,while Pichia and Aspergillus are the main dominant fungi in the four groups of fermented grains.The average clustering coefficient is the highest under the optimal process conditions,indicating that the concentration of flora in the topological network diagram is higher and more stable.The redundancy analysis showed that the influence of Thermoascus on ethanol,total acid,ethyl acetate and ethyl lactate in fermented grains changed from negative correlation to positive correlation,and promoted the formation of esters.