Analysis On Wine Aroma Enhancement By Mixed Fermentation Using Hanseniaspora Uvarum And Killer Saccharomyces Cerevisiae

With in-depth research on non-Saccharomyces cerevisiae,non-S.cerevisiae could bring wine the flavor,which may be due to the difference in enzyme activity between S.cerevisiae and non-S.cerevisiae Previous research found that it is preferred to have a strain of H.uvarum,which can effectively increase the content of medium chain fatty acid ethyl ester with fruity characteristics,but also has the risk of causing bad smell-nail odor.In order to solve the above problems,this study adopted the mixed fermentation of the killer S.cerevisiae and the preferred yeast strain to suppress the growth of the H.uvarum,in order to inhibit the poor performance of H.uvarum.In the experiment,the simulation grape juice was used as the fermentation system,and the killer group and the non-killer group were designed.The two groups were inoculated with killer S.cerevisiae（RV002）and non-killer S.cerevisiae（RV171）as control.At the same time,simultaneous inoculation and 24 h inoculation with H.uvarum were designed to was treated experimentally.The growth kinetics,esterase activity and content of esters in the fermentation process were studied,and the aroma and brewing effects were verified in the mixed fermentation of the real fermentation system of Riesling and Garanior grapes.The main conclusions are as follows:（1）Cell growth kinetics during mixed fermentation.The mixed fermentation of simulated grape juice was monitored by CO₂ weight loss and reducing sugar content,and the result was a normal alcohol fermentation curve.The microbial biomass of different yeast strains in the mixed fermentation process was monitored by the dilution coating plate method.The initial inoculation concentration of the fermentation was about 10⁶ cfu/ml.The results of growth kinetics showed that the grape juice was spores throughout the fermentation process.The selected H.uvarum did not affect the leading position of S.cerevisiae in the whole fermentation process.The biomass of the bacteria is about 4×10⁷cfu/ml.The mixed fermentation can ensure the successful completion of the alcohol fermentation.In the simultaneous inoculation fermentation process,the selected H.uvarum of killer group disappeared on the 2nd day of fermentation,and the selected H.uvarum of the non-killer group disappeared on the 3rd day.In the sequential inoculation fermentation process,the selected H.uvarum of the killer group disappeared on the 4th day.Disappeared,the selected H.uvarum of the non-killer group disappeared on day 7.The results showed that the killerf S.cerevisiae in the mixed fermentation process can significantly inhibit the growth of the selected H.uvarum.（2）Esterase activity during mixed fermentation.In the mixed fermentation process of simulated grape juice,the esterase activity was monitored by p-NP method.The results showed that the esterase activity fluctuated daily during the simulated juice fermentation,but the cumulative value of esterase activity showed an increasing trend.In the experimental group,the accumulation of esterase activity was the highest（287 m U/m L）in the simultaneous inoculation fermentation process.And the esterase activity was specific to the substrate in C2～C8,and the accumulation of C8 esterase activity was the highest（82～178 m U/m L）,the accumulation of C4 esterase activity was the lowest（15-21 m U/m L）;the esterase activity of C2,C6 and C8 in the killer group was higher than that of non-killer group by 7.8%,35.1%and 34.8%,respectively.The cumulative activity of C2～C8esterase activity in the killer group was higher than that in the non-killer group by 25.5%.The results showed that the killer group had higher accumulation of C2,C6 and C8 esterase activities,and had the potential application on wine aroma enhancement.（3）Ester substances in the mixed fermentation process.In the mixed fermentation process of simulated grape juice,the HS-SPME-GC-MS method was used to monitor the change of main ester content.The results showed that OAV>1 of ethyl acetate,ethyl butyrate,ethyl hexanoate,ethyl octanoate,isoamyl acetate and 2-phenylethyl acetate.The killer group was simultaneously inoculated with fermented ethyl acetate（93150.2μg/L）,ethyl butyrate（129.8μg/L）,ethyl octanoate（679.1μg/L）and 2-phenylethyl acetate（511.5μg/L）.Compared with the non-killer group,the growth rate was 39%,52%,298%,and96%,respectively;the killer group was sequentially inoculated with ethyl acetate（93534.8μg/L）and ethyl hexanoate（120.0μg/L）.Ethyl octanoate（122.1μg/L）and 2-phenylethyl acetate（288.3μg/L）were increased by 6%,1693%,1280%,and 111%,respectively.The results showed that the killer treatment group significantly increased the content of acetate and medium chain fatty acid ethyl ester.（4）The aroma components and aroma characteristics of the wine.The mixed fermentation of Riesling and Carnival wines was carried out by HS-SPME-GC-MS method.The aroma components in the wine samples were determined.The sensory quantitative evaluation method was used to evaluate the aroma characteristics of white wine of Riesling and red wine of Garanior.In the killer group,the acetate content in the Riesling wine sample was increased by 6%,the short-chain fatty acid ethyl ester content was decreased by 11%,and the medium-chain fatty acid ethyl ester content was increased by 1%.The content of compounds increased by 11%;the content of acetate in carnival wine samples increased by 6%,the content of short-chain fatty acid ethyl ester decreased by 4%,the content of medium-chain fatty acid ethyl ester increased by 19%,and the content of phenethyl-based compounds increased less than 1%.The killer group simultaneously inoculated with sequential inoculation of Riesling mixed fermentation significantly enhanced the sour fruit and floral notes;the non-killer group only significantly enhanced the floral,but the sequential inoculation fermentation significantly reduced the tropical fruit aroma.Although the sequential inoculation fermentation of the killer group has hardly effect on the aroma of the wine,and even reduces the aroma of the tropical fruit,the simultaneous inoculation of the mixed fermentation in the killing group significantly enhances the sour fruit and the floral fragrance,which is the same as the result of the Riesling wine.;the non-killer group only significantly enhanced the aroma of the fruit,but the sequential inoculation fermentation significantly reduced the tropical fruit and floral aroma.