Isolation And Screening Of Aroma Formers From Luzhou-flavor Daqu And Optimization Of Flavor Component Formation Conditions

This article mainly talked about the main flavor component of Luzhou-flavorDaqu,and some bacteria and yeast were isolated from daqu in different fermentatedtime.These microorganisms were used to form flavor components. And then,theinfluence factors of flavor components formed ability were researched,finallyoptimized.The main conclusions of this article were as follows:The volatile components of11samples of superior quality Luzhou-flavor Daquwere detected by the method of SPME-GC-MS.Principal component analysis andrelative odor activity value were used to analyze the flavor component in daqusamples.Finally,pentylfuran,hexanal,1-octen-3-ol,phenethyl alcohol,guaiacol andtrimethyl pyrazine were confirmed to be the main flavor components of superior qualityLuzhou-flavor daqu.Bacteria and yeast were separately isolated from daqu samples of differentfermentation time.The results showed that22kinds of bacteria and6kinds of yeastwere isolated. Each bacteria and yeast was used to form flavor components, and4kindsof bacteria and2kinds of yeast showed formation ability of flavor components. Amongthem,1bacteria and1yeast showed the extraordinary formation ability of flavorcomponents.The bacteria and yeast were coded as X19,J3seperately. SPME-GC-MSmethod was used to detect the volatile components in the fermentation product of thetwo strains, results showed that abundant flavor components belonged to superiorquality Luzhou-flavor Daqu were detected in the fermentation products of the twostrains.Molecular biology technique was applied to identify the two strains.Theidentification results showed that X19belonged to Bacillus licheniformis,J3belonged to Pichia anomala.Different conditions of temperature,charge amount,moisture content andinoculation amount were considered as key factors to disscuss the effection to the flavorcomponents and enzyme activities in the fermentation products of X19and J3seperately.The results showed that these factors could affect growth metabolism andenzyme activity of X19and J3,and then the formation or transformation process offlavor components were effected.The factors of temperature,charge amount andmositure content had a most significant effect on the varieties and content of flavorcomponents of X19, meanwhile,the factor of inoculation amount effected lesssignificantly.At the same time,the factors of mositure content,temperature,andinoculation amount had a less significant effect on the varieties and content of flavorcomponents of J3compared with the factor of charge amount.With the fermetationprocess continued,the fermentation product became more and more fragrant and theflavor components became abundant.The formation conditions of flavor components of X19were optimized byresponse surface optimization.And the best level of each factor was figured out by theDesign Expert8.0.5software and the results were as follows:35.950℃of temperaturecondition,47.040%mositure content,139.620g/250mL charge amount and predictedpeak area of flavor components was5.602×108.After the confirmatory experiment,theaverage peak area of flavor components was572271523.618,very close to the predictedone.Compared with superior quality daqu,the content of guaiacol in the optimumcondition product had increased the number of nearly10times, trimethyl pyrazinenearly26times.The formation conditions of flavor components of J3were optimized by responsesurface optimization.And the best level of each factor was figured out by the DesignExpert8.0.5software and the results were as follows:34.390℃of temperaturecondition,45.690%mositure content,44.890g/250mL charge amount and predicted peakarea of flavor components was1.768×108. After the confirmatory experiment,theaverage peak area of flavor components was173225090.951,very close to the predictedone. Compared with superior quality daqu,the content of pentylfuran in the optimumcondition product had increased the number of nearly1.8times, phenethyl alcoholnearly2.8times.