Screening Of Aroma-producing Microorganisms In High-temperature Daqu And Application Of Aroma-producing Microorganisms

Because of the special manufacturing process,high temperature Daqu has collected a lot of aroma-producing microorganisms which plays an important role in the formation of Baijiu flavor.With the deepening of research,aroma-producing microorganisms of high temperature Daqu has achieved a good application effect in improving the quality and enriching the flavor of Bajiu.In this study,aroma-producing microorganism were isolated and screened from high temperature Daqu,and the screened strains were identified and the growth characteristics were studied.The strains were made into pure seed enhancer and the optimal preparation process was determined.The application of the fortifier in Xiaoqu Baijiu and its effect in liquor application were studied,which provided certain data support for the application of the fortifier,and also provided theoretical and practical basis for the improvement of Xiaoqu Baijiu quality and technical innovation and development.The research content and results of this paper are as follows:(1)Screening,identification and properties of functional aroma-producing microorganism.XJ-12 and JM-3 were screened from the high-temperature Daqu samples by traditional isolation and screening methods combined with flavor components analysis of solid-state fermentation.XJ-12 and JM-3 were identified as Bacillus licheniformis and Saccharomycopsis fibuligera respectively by morphological observation,physiological and biochemical experiments and molecular biology.The main volatile products from Bacillus licheniformis XJ-12 solid-state fermentation were 2,3,5,6-tetramethylpyrazine,acetoin,phenylethyl alcohol,phenol,ethyl phenylacetate,etc;the volatile flavor substances of Saccharomycopsis fibuligera JM-3 solid-state fermentation mainly included phenylethyl alcohol,4-ethyl guaiacol,acetic acid,isovaleric acid,etc,and the content of esterswere affluent.XJ-12 grew rapidly and reached the growth stationary phase about on the 18 th hour.It could grow at 55? and inhibited at pH 3.5.XJ-12 could tolerate 8% ethanol,17% NaCl and 25% initial sugar content.JM-3 has a good ability to produce amylase.It entered the rapid enzyme production period on the 10 th hour and reached the highest value around on the 14 th hour.Yeast JM-3 grew well between 31 and 40?,and was inhibited when the pH value was below 2.5.JM-3 could tolerate 14%ethanol,17% NaCl and 25% initial sugar content.(2)Study on preparation process of bacterial enhanced starter.The effects of different proportion of raw material,different initial moisture content,different inoculation quantity,different fermentation temperature and time on the enhanced starter were studied.According to the results of single factor test,the orthogonal experiment was designed to optimize the preparation process of bacterial fortifier.The results showed that: Fermentation time is the main factor which influences the bacterial solid state fermentation and water content is the secondary factor,fermentation temperature has the least effect.The optimum preparation conditions were as follows: wheat: bran=9:1,initial water content of 55%,inoculum amount of 8%,and solid state fermentation at 40? for 20 h.Based on the single factor experiment,the Box-Behnken design was used to optimize the preparation process of yeast fortifier.The results showed that: The order of influence of various factors on the activity of glucoamylase is: inoculum size>fermentation time>moisture content.The optimal preparation conditions for the yeast fortifier combined with actual production are rice pulverization degree 60-90 mesh,initial water content 60%,yeast seed liquid inoculum amount 9.5%,solid state fermentation for 73 h at 30?.(3)Application of pure koji enhancer in the brewing of Xiaoqu Baijiu.The process of Xiaoqu Baijiu fermentation was simulated in the lab in which the enhancer was added in different ways respectively.The results showed that the better results were obtained when the bacterial intensifier and the mixed grain were piled up and fermented for 72 hours.While the yeast fortifier was added before saccharification,the fermentation effect was better.On the basis of the brewing process of Chuanfa Xiaoqu Baijiu,the experimental group with the addition of fortifier and the blank group with only the commercially available Xiaoqu were compared and analyzed.The dynamic tracking test of the physical and chemical indicators of the liquor cellar during the fermentation process showed that the changes of temperature,moisture,acidity,reducing sugar content and starch content in the experimental group and the blank group were basically the same,but the indexes of the experimental group were better than the blank group.The fermenting grains and the Baijiu samples were analyzed by GC-MS.The result showed that the variety and contents of the volatility components in the experimental group were higher than that in the blank group,especially esters and aromatic substances.The content of ethyl acetate was about 1125.804mg/L and increased by 64.41%.The total acid and ester of the liquor samples were 0.536g/L and 1.373g/L respectively.The Baijiu was limpid and transparent,sweet and refreshing,natural aroma,pure and elegant,slightly honey and roasted,tastes more mellow,coordination and long aftertaste.Three different Xiaoqu marketed were used to determination of physical and chemical indicators and Xiaoqu Baijiu before and after fermentation.The results showed that the physicochemical data of the liquor cellar in the experimental group were better than those in the blank group,and the wine yield increased by 4.95%,4.59%,2.85% respectively.initially indicating that the fortifier has a certain role in different songs,and has wide applicability.The results showed that the intensifiers had positive effects on the fermentation of Xiaoqu Baijiu and had good applicability.