Analysis Of The Stress Resistance Mechanism And Fermentation Performance Of Ice Wine Yeast

Ice wine yeast and grape varieties are one of the main factors affecting the quality of ice wine.Ice wine fermentation is usually carried out at 8-12 °C.Low temperature will reduce the metabolic activity of yeast and slow down the growth rate,thereby prolonging the fermentation cycle and increasing the food safety risks such as bacterial invasion and ice wine failure.In order to ensure normal low-temperature fermentation,it is necessary to have a correct understanding of the low-temperature response of yeast and provide effective technical support.However,the response mechanism of Saccharomyces cerevisiae under low temperature stress conditions is not thoroughly studied,and there are still many doubts.In order to clarify the stress resistance mechanism and fermentation performance of ice wine yeast,this study first screened out yeast strains with different tolerance to low temperature conditions,formed different stress environments through different temperatures and different concentrations of fermentable sugars,combined with fermentation performance parameters and RNA-Seq sequencing technology,analyzed the key factors related to low temperature tolerance of yeast strains,and explored the stress resistance mechanism of ice wine yeast;uses ice grape juice fermentation to study the winemaking performance of different yeasts,and lays the foundation for optimizing the fermentation process of ice wine yeast.The specific research results are as follows:1)Using the yeast L.A.Bayanus with poor low temperature tolerance as the control,with q Value<0.05 and |log2FC| ≥ 2 as the screening conditions,the gene expression differences of different yeasts at 25 ℃ and 12 ℃ were analyzed.The results showed that the expression level of sugar metabolism genes in each yeast strain was higher at 25 ℃,and the expression level was the highest in the yeast L.A.Bayanus,indicating that the strain could carry out normal metabolic activities at normal temperature.12 ℃ can cause low temperature stress to the normal growth and metabolism of yeast strains.Different yeast strains can activate the expression of various stress stress genes,among which a large number of oxidative stress-related genes are activated and expressed,and the expression in different yeast strains is significantly different.The yeast L.A.Bayanus,which is less tolerant to low temperature,resists oxidative stress by increasing the expression level of directly activating antioxidant-related genes;while yeast CECA mainly maintains the normal growth of cells by encoding sulfur-containing compounds involved in oxidative stress.Otherwise,avoid and repair yeast cell wall damage by increasing the expression of the gene NAG1.2)Using yeast CECA、 EC1118、 L.A.Bayanus and VIC to ferment the "Hutai No.8" ice grape juice,it was found that the yeast CECA and EC1118 finished the fermentation on the 24 th day,while the yeast L.A.Bayanus and VIC fermented slowly,on the 29 th day When the fermentation is finished.The types of organic acids produced by different yeasts are different.The organic acids of yeast CECA fermentation products are mainly malic acid and citric acid,and the organic acids of yeast EC1118 fermentation products are mainly malic acid,citric acid and succinic acid.Yeast L.A.Bayanus The organic acids of fermentation products are mainly citric acid,and the organic acids of yeast VIC fermentation products are mainly citric acid and succinic acid.3)The content of aroma components in different yeast-fermented ice wine samples was analyzed,and it was found that isoamyl alcohol,phenylethyl alcohol,monoethyl succinate,2,4-di-tert-butyl phenol in samples fermented with "Hutai No.8" grapes were used to simulate ice wine fermentation.It is the main aroma substance,showing the aroma characteristics of mainly fruity and floral.Especially the fermented product of yeast CECA has a prominent floral and fruity aroma,which is suitable for brewing "Hutai No.8" ice wine.The fermentation products of yeast L.A.Bayanus detected substances with unpleasant odors such as n-heptanoic acid,butyric acid,etc.The yeast started to ferment slowly at low temperature and had a long fermentation time,so it was not suitable for brewing ice wine.