| China's grape production ranks first in the world year after year,but grape processing products are relatively backward,in which the wine production is far lower than the world average level[1],while in China,mainly based on fresh grape cultivation and fresh wine has a large market.Prospects and market size,starting from the above issues,the purpose of this study was to screen the yeasts that were fermentated on table grapes,and to isolate and identify the yeasts in the soil and in the branches or leaves of fresh grape plantations,and to investigate their fermentation performance.GC-MS was used to determine the types and contents of aroma compounds in different yeast fermentated wines.The characteristic aroma components of different fermentated wines were explored in combination with OAV values.The overall acceptance of different fermentated wines was analyzed by means of sensory evaluation.The better-flavored Saccharomyces cerevisiae was made bioactive dry yeast.The main findings are as follows:?1?Separation and identification of yeasts in collected soil and fruit leaf samples.The results showed that the strains S1,S2,and S3 were Saccharomyces cerevisiae,and the strain S4 was an abnormal Wickerhamomy ces anomalus.The results showed that the optimal growth temperature of S1 and S2 was 28?,the optimal growth temperature of S3 and S4 was31?,and the four yeast strains entered the logarithmic phase at about 5 h.About 15h into the growth balance period.?2?Using GC-MS to analyze the aroma compounds of different fermentated wines,the results showed that compared with commercial yeast fermentated wines,S1 fermentated wine has higher content of ethyl octanoate,ethyl decanoate,ethyl laurylate,and S2 fermentation.The content of ethyl caprate,phenylethyl alcohol,octanoic acid,decanoic acid,geranyl acetone,2,6-di-tert-butyl-p-cresol,4-vinyl-2-methoxyphenol,S3 fermentated wine had high ethyl acetate content and ethanol content,S4 fermentated wine had a higher acetic acid content.?3?The OAV value was used to analyze the characteristic aroma compounds of fermented wine.The results showed that among the aroma compounds of fresh wine fermented by strain S1,ethyl decanoate,phenylethyl alcohol and other compounds accounted for a large contribution rate,and also for S2 fermented wine.The major contributors include ethyl butyrate and ethyl heptanoate.Analysis of the main aroma compounds in strain S3fermented wine is similar to that of commercial yeast.?4?Study on the preparation technology of active dry yeast for strain S3.The results showed that the optimum substrate species and concentration conditions in the medium were as follows:the carbon source material was sucrose?50 g/L?,the optimal nitrogen source material was yeast extract?18 g/L?,and the inorganic salt substance was dihydrogen phosphate potassium?4.5 g/L?and auxin were nicotinamide?0.12 g/L?.In the screening experiment of centrifugal conditions,the optimum rotation speed of the yeast liquid was5000r/min,and the time was 15 min.The yeast yield under this condition was 92.69%.In the single factor experiment of yeast freeze-dried powder protectants,the lyophilized powders under the action of 13 kinds of protective agents were free of bacterial infection,and the highest number of viable cells was obtained under the action of three protective agents.They were glucose?45.4%?and malt paste respectively.maltodextrin?41.7%?and sorbitol?32.6%?,the optimal composite protectant ratio and composition were 9%glucose,5%sorbitol,and7%maltodextrin.?5?Study on the preparation technology of active dry yeast for strain S3.The results showed that the optimal substrate composition and concentration conditions in the medium were:the optimal carbon source material was sucrose?50 g/L?,the optimal nitrogen source material was yeast extract?18 g/L?,and the optimal inorganic salt material was It is potassium dihydrogen phosphate?4.5 g/L?and the optimal auxin is niacinamide?0.12 g/L?.At the same time,in the centrifugal process parameters,when the rotation speed is 5000r/min and the time is 15min,the yeast yield under this condition is 92.69%.In the single factor experiment of yeast freeze-dried powder protective agent,the lyophilized powders under the action of 13kinds of protective agents were free of bacterial infection,and the highest number of viable cells was obtained under the action of three protective agents.They were glucose?45.4%?and malt paste respectively.Semen?41.7%?and sorbitol?32.6%?,the optimal composite protectant ratio and composition were 9%dextrose,5%sorbitol,and 7%maltodextrin.?6?The results of the rehydration activation test of yeast lyophilized powder showed that the amount of 2.5%-4.5%freeze-dried powder,the 4%-6%sucrose aqueous solution,and the 39-41? rehydration activation temperature were rehydration-activated The optimal experimental parameters for the experiment;compound experiments using the above three parameters for rehydration activation showed that the optimal composite protectant ratio and composition were 3%of freeze-dried powder and 4%of sucrose aqueous solution.Reactivation temperature of 40?. |
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