| At present,Lujiu has been positioned as a unique traditional Chinese wine for promotion by the China Alcoholic Drinks Association.The mechanized production of Xiaoqu liquor is mainly made of sorghum and Xiaoqu saccharification and fermentation.The production cycle is 7 to16 days.It has a clean body and a good fusion with other flavor components.It is one of the most suitable liquor varieties for base liquor.For the purpose of stabilizing and improving the quality of mechanized Xiaoqu liquor and reduce the labor intensity,Strengthening the research on the key volatile compounds and related microorganisms of mechanized production of Xiaoqu liquor has important scientific significance and practical value for improving the quality of its body and liquor.Taking the Xiaoqu liquor produced by a mechanized process in a winery in Hubei as the research object,this paper uses comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry technology combined with gas chromatography-mass spectrometry.The qualitative and quantitative analysis of volatile compounds in Xiaoqu liquor was carried out by combined use and gas chromatography-scenting method,aiming to identify the key volatile compounds in Xiaoqu liquor.On this basis,the differences mechanism in the key volatile compounds of mechanized production of Xiaoqu liquors of two different quality grades are also analyzed,and it is clear that esters and higher alcohols are important compounds that affect the quality of this type of liquor.Furthermore,high-throughput amplicon sequencing is used to reveal the community structure and changing laws of microbes in Xiaoqu,the random forest algorithm is used to determine the different microbes,and the correlation analysis algorithm is used to determine the related microbial species formed by key volatile substances.Finally,using spore hybridization technology and using the higher alcohol content of key volatile components as the screening index,an attempt was made to breed low-yielding fusel oil brewing yeast strains.The main conclusions are as follows:1.The identification of the key volatile compounds of mechanized Xiaoqu Qingxiang liquor and the analysis of its flavor contribution.A total of 141 species were obtained,including 51 esters,20 alcohols,8 acids,17 aldehydes and ketones,18 aromatic compounds,21 hydrocarbons,and 6 other kinds by HS-SPME,GC/GC-TOFMS analysis.On this basis,through GC-O analysis,the dilution factor FD was used to find out 57 kinds of compounds that contribute to the flavor of Xiaoqu liquor,such as ethyl caprylate,among which the main ester compounds were ethyl caprylate,ethyl acetate and lactic acid.The alcohol compounds,in addition to ethanol,the higher OAV values were higher alcohols,such as isobutanol,n-propanol,1-octene-3-ol,etc.;aldehydes were mainly acetaldehyde and benzene Acetaldehyde and so on.Through aroma reconstruction and omission tests,it was proved that there are 32 key aroma substances in Xiaoqu liquor.Among them,ethyl caprylate and ethyl acetate have the most significant contribution to flavor in ester compounds,and the contribution of higher alcohols to aroma was second.Acetic acid was an indispensable acid compound.2.Analysis of the difference of key volatile compounds in mechanized production of Xiaoqu fresh-flavor liquors of two different quality grades.Two different quality grades of Xiaoqu liquor were selected from the brewing factory for detection and analysis.Through qualitative identification of the two samples,95 volatile components were identified,and of which 86 common components in the last result.It reflects that the main aroma characteristics of Xiaoqu liquor are basically the same.In order to further clarify the key compounds that affect the quality of Xiaoqu liquor,through the quantitative analysis of 47 compounds,and the partial least square discriminant analysis(PLS-DA)classification model,the visual trend analysis of volatile compounds was found.There were 6 compounds with VIP value greater than1,namely: isoamyl alcohol,isobutanol,ethyl acetate,acetaldehyde,acetic acid,ethyl lactate.It can be seen that in addition to esters,isobutanol and isoamyl alcohol in higher alcohols significantly affect the quality of Xiaoqu liquor.3.Correlation analysis between key flavor components and microbial populations in Xiaoqu Liquor produced by mechanization.Through high-throughput amplicon sequencing to reveal the microbial community structure and changes in Xiaoqu,and combined with headspace solid-phase microextraction and GC-MS,analyzed the volatile components of three Xiaoqu liquors produced by Xiaoqu.On this basis,the random forest algorithm is used to determine the different microorganisms,and the correlation analysis algorithm was used to determine the correlation between the microorganisms in Xiaoqu and the higher alcohols and esters in the corresponding Xiaoqu fragrant liquor.Herbaspirillum,Weissella and Rhizopus are the common dominant genera in the three Xiaoqu.Candida genus and ethyl acetate show a positive correlation;Klebsiella genus and ethyl caprylate and ethyl caproate show a positive correlation trend.Weissella,Staphylococcus,Lactobacillus,Acetobacter,Sphingobacterium,Klebsiella,Enterobacter,Apiotrichum,and Aspergillus had a significant positive correlation with acids.4.Breeding of a low-yield higher alcohol yeast.By using the yeast hybridization technology,the high alcohol content of the key volatile component in the liquor was selected as the screening index,and the low-yielding fusel oil brewing yeast was selected,and the yeast was tested in the workshop.The results showed that the acetaldehyde content increased by 0.06 g /L,the increase rate was 25.66%;the content of methanol,n-propanol,ethyl acetate,and fusel oil decreased by 0.01 g/L,0.08 g/L,0.09 g/L,and 0.25 g/L,and the rates of decrease were 8.56%,10.86%,13.75%,and 9.83% respectively.This result shows that the hybrid yeast Y249 test song has a significant effect on reducing the content of fusel oil. |
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