| The eastern foothills of Helan have favorable geographical and climatic conditions,the growing area of wine grapes is growing,and the winemaking industry has developed rapidly,and has become one of the special industries in Ningxia.As the global climate warms,the sugar content of grape fruits rises,and the potential alcohol content increases,making Saccharomyces cerevisiae more severe alcohol stress in the alcohol fermentation stage,resulting in incomplete fermentation,which affects the wine quality and storage conditions.In this paper,by studying the effect of exogenous trehalose,inositol and proline on the ethanol tolerance of Saccharomyces cerevisiae,the best exogenous additives and addition amounts were screened out to further study the change trend of the physical and chemical indicators of the fermentation process and the fermentation characteristics of Saccharomyces cerevisiae.And applied it to Cabernet Sauvignon fermentation experiment,aiming to provide a certain theoretical basis for improving the quality of Cabernet Sauvignon wine.The specific research content and experimental results are as follows:(1)Ethanol tolerance experiment:select Ningxia native Saccharomyces cerevisiae NX 11424(Saccharomyces cerevisiae NX 11424)as the experimental strain,trehalose,inositol and proline as additives,set the experimental alcohol degree to 12,14 and 16,and explore its Effects of Saccharomyces cerevisiae ethanol tolerance.The results showed that:300mg/L trehalose was added to make the Saccharomyces cerevisiae density reach a maximum value of 0.955;the maximum trehalose content of the cell body was 132.58mg/mL;the maximum intracellular ATP content was 4430.548?mol/gport;plasma membrane H+-ATPase Vitality 4.266 mgprot/mL;the maximum content of ergosterol in the bacterial body is 550.8 ?g/mL.Add 150 ?g/L inositol to make the density of Saccharomyces cerevisiae reach a maximum value of 0.792;the maximum trehalose content of the cell body is 109.928 mg/mL;the maximum intracellular ATP content is 4411.506 ?mol/gport;the plasma membrane H+-ATPase activity 4.103 mgprot/mL;the maximum content of ergosterol in the bacteria is 490.8 ?g/ml.Adding 200mg/L proline can make the Saccharomyces cerevisiae density reach a maximum of 0.7905;the maximum trehalose content of the cell body is 109.15 mg/mL;the maximum intracellular ATP content is 4233.776?mol/gport;the plasma membrane H+-ATPase activity is 4.024 mgprot/mL;the maximum content of ergosterol in the bacterial body is 482.8 ?g/mL.A comprehensive analysis of the cell density,cell trehalose content,intracellular ATP content,plasma membrane H+-ATPase activity and cell ergosterol content of each fermentation group in different alcoholic degrees revealed that these three substances were resistant to S.cerevisiae ethanol The order of force is trehalose>inositol>proline.(2)Simulated grape juice fermentation experiment:Through experiment(1),it is determined that the additive is trehalose,and the addition amount is 300 mg/L.According to the conversion rate of sugar alcohol,the wine degree of simulated grape juice was set to 12,14 and 16,and the influence of trehalose on the fermentation characteristics of Saccharomyces cerevisiae NX11424 in the early,middle and late fermentation period was explored.The results show that trehalose can improve the fermentation power,fermentation speed and wine production rate of Saccharomyces cerevisiae NX11424,increase the alcohol content of the fermentation broth,and have little effect on the total acid and pH value.(3)Cabernet Sauvignon fermentation experiment:After sterilizing Cabernet Sauvignon grape juice,it is connected to Ningxia native Saccharomyces cerevisiae NX11424 and 300mg/L trehalose.By measuring the physical and chemical indexes,phenol content,chromaticity,hue and aroma components of each fermentation group after fermentation,the effect of trehalose on the quality of Cabernet Sauvignon fermentation broth was explored.The results showed that compared with the control group,the content of residual sugar,total acid and volatile acid in the trehalose fermentation group decreased,the content of phenols and the color value increased,and there was no significant difference between the two groups in alcohol content,pH value and color value.The trehalose fermentation groupincreased the type and content of aroma substances,and the content of isoamyl acetate,hexyl acetate,ethyl caprylate,isoamyl caprylate,ethyl laurate,isoamyl laurate and caprylic acid increased,giving the wine a rich flavor Floral and fruity.2-methyl-1-butanol,ethyl heptanoate,phenethyl acetate,ethyl palmitate and 2,6,8-trimethyl-4-nonanone increase the variety of aroma substances,giving the wine more complex Aroma.The content of n-decanoic acid and acetic acid is reduced,no isoamyl alcohol is detected,which reduces the bad flavor substances in the wine and improves the taste of the wine. |
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