| In this paper,the diversity and brewing characteristics of enzyme producing yeasts in soil samples of Changli,Hebei Province were studied.In order to screen the native enzyme producing yeast with good fermentation characteristics,and provide reference for the research of excellent yeast fermentation strains.The results are as follows:1.A total of 165 yeasts were isolated from four vineyard soils in Changli,including 83 non Saccharomyces cerevisiae and 82 Saccharomyces cerevisiae.There are 108 enzyme producing yeasts in total,among which 24 yeasts produce 3 kinds of enzyme at the same time,30 yeasts produce 2 kinds of enzyme at the same time,and 54 yeasts only produce 1 kind of enzyme.2.According to the color and morphological characteristics of non Saccharomyces cerevisiae in WL medium,12 kinds of non Saccharomyces cerevisiae were obtained,including Brettanomyces,Hanseniaspora uvarum,Pichia membranaefaciens,Hansenula anomala,Pichia kluyveri,Torulaspora delbrueckii,Schizosaccharomyces pombe,Saccharomyces ludwigii,Zygosaccharomyces bailii,Candida zemplininaj,Metschnikowia pulcherrima,a yeast not mentioned in the relevant literature.3.The results showed that: GY1,M9 and J24 had higher activity when sugar concentration was 500g/L;GY13 and M9 could tolerate 15% alcohol;J24 and GY1 had higher activity when pH was 2.5;J24 had better low temperature tolerance.According to the change of alcohol content,the utilization of residual sugar and the growth kinetics of yeast,the fermentation characteristics of active dry yeast and J24 in the process of mixed fermentation are excellent and suitable for mixed fermentation.4.During the brewing experiment,the physical and chemical indexes of the whole fermentation process were monitored.Through the analysis of various wine physical and chemical indexes,it can be concluded that when the fermentation is over,the minimum content of residual sugar in No.5 wine is 3.4g/L,and the maximum content of residual sugar in No.7 wine is 10.0 g/L.The content of residual sugar in other wines was between 3.5-7.3 g/L.The lowest residual sugar content of No.6 wine is 3.5 g/L,the highest residual sugar content of No.8 wine is 7.5 g/L,and the rest is between 4.5-7.5 g/L.The utilization rate of residual sugar in wine by the selected local enzyme producing yeast in Changli is lower than that of the active dry yeast,which can be used in the production of semi dry wine.The changes of pH value in each fermentation process were different,but they were all in the normal range(2.7 ~ 3.8),indicating that different fermentation processes had little effect on the pH value of wine.And its alcohol production ability is equal to that of active dry yeast.During aging,the content of volatile acid and total sulfur decreased.5.Through the comprehensive analysis of color difference,sensory evaluation and GC-MS results,it can be concluded that the enzyme activity of enzyme producing yeast in mixed fermentation(5,6)can clarify the wine body,improve the brightness of wine,improve the color and saturation of wine(? E > 90).The total number of main aroma substances in 10 kinds of wine was 44,68,62,65,29,57,42,52,47 and 61 respectively.The total contents of aroma were 1899.3mg/L,3792.63mg/L,1328.65mg/L,1843.89mg/L,418.94mg/L,516.43mg/L,649.66mg/L,120.73mg/L,1318.93mg/L and 1598.62mg/L,respectively.The main aroma components are esters,alcohols and organic acids.The coexisting substances of 10 kinds of wine are diethyl succinate and ethyl octanoate.The aroma substances of rose wine fermented by natural fermentation and active dry yeast are better than those of Cabernet Sauvignon in terms of category and content;the aroma substances are: there is little difference between the local wild yeast single strain fermentation and active dry yeast single strain fermentation,and the aroma substances produced by mixed strain fermentation are less;the aroma substances content is: natural fermentation > active dry yeast single strain fermentation > Ben Mixed fermentation of native and wild yeasts. |
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