Comparative Study On The Characteristics And Microbial Community Of Fermented Grains Of Strong-aroma Baijiu Made By Mechanized And Traditional Brewing

Strong-aroma flavor Baijiu,as one of the four traditional flavor Baijiu types,is deeply loved by consumers.it is made by solid fermentation in mud cellar,distillation,aging and blending.The traditional brewing method of Strong-aroma flavor Baijiu mainly depends on individual operation skills and experience to control the quality,which has many unstable factors.With the development of modern science and technology,mechanized equipment has been applied to the brewing of Strong-aroma flavor Baijiu.With the development of modern science and technology,mechanized equipment has been applied to the brewing of Strong-aroma flavor Baijiu,which reduces the labor intensity and improves the labor efficiency.However,the application of mechanized brewing method in Strong-aroma flavor Baijiu production,along with the change of operation mode and workshop environment,will have an impact on brewing,which needs to be further studied.In this study,the fermented grains and raw liquor made by mechanization and traditional brewing methods of Strong-aroma flavor Baijiu were studied,the texture characteristics of fermented grains in different brewing processes were determined by using texture analyzer,high-throughput sequencing technology was used to analyze the microbial community structure of fermented grains in different brewing methods,and then HS-SPME technology was used to determine flavor substances in fermented grains.GC-FID was used to analyze the flavor substances of original wine with different brewing methods.The main research conclusions are as follows:(1)The water content of fermented grains in CT workshop(traditional brewing method)was significantly higher than that in mechanized brewing method,it indicated that the water measurement by hand had a great influence on the water content of fermented grains,because the water consumption was affected by the workers’ experience through the water measurement by hand.The mixing method and steaming method in JXA workshop and JXB workshop(mechanized brewing method)had a great influence on the hardness of fermented grains,both of the two operation methods can reduce the hardness of the grains and lead to the decrease of the bone strength of the fermented grains.(2)A total of 54 flavor substances were detected by HS-SPME-GC-MS(headspace-solid phase micro extraction-GC-MS)in the fermented grains from the pit of CT workshop,JXA workshop and JXB workshop,The contents of ethyl caproate,ethyl butyrate,hexyl caproate,acetic acid,butyric acid,heptanoic acid,octanoic acid,phenylethanol,n-amyl alcohol,n-butanol and other flavor substances in fermented grains produced by different brewing methods were significantly different.The contents of ethyl caproate,butyric acid and n-butanol in fermented grains produced by the traditional brewing method were higher than that by the mechanized brewing method.The contents of hexyl caproate,ethyl butyrate,acetic acid,heptanoic acid,octanoic acid and n-amyl alcohol in fermented grains produced by mechanized brewing method were higher than those by traditional brewing method.(3)There were Weissella,Lactobacillus,Staphylococcus,Thermoascus,Aspergillus and Thermomyces in the fermented grains of the CT workshop.there were Bacillus,Saccharopolyspora,Thermoactinomyces,Thermoascus,Thermomyces,Aspergillus in the fermented grains of JXA workshop,there were Weissella,Lactobacillus,Saccharopolyspora,Aspergillus,Thermomyces,Thermoascus in the fermented grains of the JXB workshop.Venn analysis showed that 78.33%,69.05% and 76.23% of the bacteria from Daqu in the fermented grains from CT workshop,JXA workshop and JXB workshop were from Daqu,55.10%,57.14% and 55.88% fungal genera from Daqu.Lactobacillus,Weissella,Pichia,Kazachstania,Saccharomyces and Naumovozyma may be derived from the brewing environment.(4)Through the sensory evaluation of raw Baijiu with different brewing methods,it was found that the ester aroma intensity of raw Baijiu in JXA workshop was higher,the floral and fruit aroma intensity of raw Baijiu in JXB workshop was higher,and the aroma intensity of original wine cellar in CT workshop was higher.Through GC-FID(gas chromatography with hydrogen flame ionization de-tection)technology,a total of 50 flavor substances were determined in raw Baijiu of different brewing methods.Through OPLS-DA analysis and VIP value,26 important flavor compounds with different flavors were screened out from the samples.The content of ethyl caproate in the second grade raw Baijiu of JXA workshop was higher than that of CT workshop and JXB workshop,the ethyl acetate content of the second grade raw Baijiu in the bottom grains of CT workshop was higher than that in JXA workshop and JXB workshop,The content of ethyl butyrate in the second grade raw liquor of the upper and lower grains in JXB workshop was higher than that in CT workshop and JXB workshop.In conclusion,the mechanized operation mode will affect the hardness of grains,thus leading to the increase of the dosage of bran husk.Besides,the brewing microorganisms of different brewing methods may come from Daqu and the brewing environment,thus affecting the fermentation.