Screening And Identification Of Quality Yeast Strains In Grape Dry Red Wine

In the process of wine brewing,yeast has a direct influence on the quality of wine and plays an important role in the formation of wine flavor.In order to obtain wine yeast who has good and stable fermentation performance.The Wine yeast was isolated from grape peel,orchard soil and natural fermentation broth,and then its growth characteristics,fermentation performance and bacterial tolerance were studied.Finally,selected 4 strains of yeast,WJ1,Q₁2,S₁2 and S₂1.The results of the study are as follows:1.Using Bengal red culture medium to separate and screen the yeast from the grape fruit,orchard and natural fermenting mash of different producing areas.106 strains of yeast were screened and the strains were numbered.2.The test strains were screened by duer tube and tolerance test.Finally,selected 4strains of yeast,WJ1,Q₁2,S₁2 and S₂1,which had high speed of fermentation and comprehensive tolerance were selected.WL differential medium for the identification and classification of strains,cultivation of colony characteristics based on WL in nutrient agar by observing the combination of yeast,According to the yeast identification manual and identificational theory of WL nutrient agar medium of Cavazza.preliminary determination,strains WJ-1 and Q₁2 is the Torulaspora debrueckii,S₁2,S₂1 is the Zygosaccharomyces bailii.3.Determine the growth curve of yeast strain WJ1,Q₁2,S₁2 and S₂1,and determine the logarithmic growth cycle was 6¹2h.To determine The optimum growth conditions of WJ1,Q₁2,S₁2 and S₂1 were studied:WJ1,PH5.0,temperature 30?,OD₆₀₀ values of1.237.Q₁2 and S₂1,PH4.0,temperature 30?,OD₆₀₀ values of 1.036 and 0.894.The strain S₁2,PH6.0,temperature 32?,OD₆₀₀ of 1.198.The tolerance indexes of WJ1,Q₁2,S₁2 and S₂1 were as follows:alcohol tolerance 16%vol,SO₂ resistance in 350mg/L,acid resistance PH1.6,high sugar 50%.4.Taking French DS yeast as a control,the fermentation characteristics of strains WJ1,Q₁2,S₁2 and S₂1 were studied through grape juice fermentation,and the fermentation rate,residual sugar and alcohol yield of the strain were determined.Strain Q₁2 began to be leavened after inoculation of 8h,and the main fermentation was finished after 9d.at temperature 28?,Compared with strain DS,the fermentation rate of strain Q₁2 was fast and fermented.After fermentation,the yield of alcohol 11.2%vol and residual sugar of strain Q₁2 was 3.5g/L.Compared with the control strain,the fermentation performance of strain Q₁2 was better than that of DS,which is suitable for brewing wine.