Screening Of Metschnikowia Pulcherrim And Its Application In Winemaking

In this paper,seven native Metschnikowia pulcherrim strains?Mp1?Mp2?Mp3?Mp4?Mp5?Mp6?Mp7?were investigated.Firstly,the growth and fermentation characteristics of Metschnikowia pulcherrim strains were analyzed.Then,the mixed fermentation of Metschnikowia pulcherrim and Saccharomyces cerevwasiae was analyzed to explore the changes of related enzyme activities during fermentation process.Headspace solid-phase micro-extraction?HS-SPME?,gas chromatography with mass spectrometry?GC-MS?were employed to analyze the aroma components in different wine samples during fermentation process.The above mentioned strains were used in dry white wine brewing using Chardonnay grape as the raw material,which study provided theoretical basis for the application of Metschnikowia pulcherrim strains in winemaking.The main results are as follows:?1?Mp1,Mp2,Mp4 and MP7 have short growth delay and the biomass are of high level.They have strong tolerance to sugar,alcohol and SO₂,and can adapt to extreme fermentation conditions.In addition,the Mp4 has higher?-glucosidase activity,and the Mp7 has higher esterase activity.Metschnikowia pulcherrim can inhibit the growth of Torulaspora delbrueckii,Cryptococcus albidu and Hanseniaspora uvarum during fermentation process,but it can not inhibit the growth of Saccharomyces cerevwasiae and lactic acid bacteria.?2?A study of substrate specificity?C2^C8?for esterase activity was studied,the results are as follows:C8>C6>C2>C4.In the mixed fermentation process,the esterase activity increased and reached a high level during the first 1 to 3 days.Then the esterase activity began to decrease and reached a stable level.The esterase activity of mixed fermentation of Mp7 and Saccharomyces cerevwasiae was the highest,at the same time,the accumulation of esterase activity was the highest,which was 372.93mU/mL.Through the determination of ester aroma,and found that compared with fermentation using single strain of Saccharomyces cerevwasiae,the addition of Metschnikowia pulcherrim strains significantly increased the types of ester volatile flavor compounds.When the fermentation was carried out for 2 to 3 days,the types and contents of volatile flavors were of high level,and then decrease and stabilize.Some esters such as ethyl octanoate and ethyl citrate always exist in the fermentation process.?3?During the whole fermentation process,?-glucosidase activity was higher in the early and middle stages of fermentation process,especially the mixed fermentation of Mp4 and Saccharomyces cerevwasiae,which reached the highest on the second day,being 12.8 mU/mL.In the late stage of fermentation process,the?-glucosidase activity of Saccharomyces cerevwasiae fermentation alone was higher than other treatments.Through the determination of terpene aroma,?E?-b-Farnesene was unique for the mixed fermentation of Mp1 and Mp2 with Saccharomyces cerevwasiae.Terpinolene was unique for Saccharomyces cerevwasiae fermentation alone and mixed fermentation of Mp2 and Saccharomyces cerevwasiae.Myrcene was unique for mixed fermentation of Mp2 and Saccharomyces cerevwasiae.It was found that the content of terpenes was generally low.The main terpenes were linalool,geraniol and citronellol.On the first day of fermentation process,less terpenoids were detected,most of which were in the form of glycoside bonds and had no volatility.?4?Fermentation techniques of the Chardonnay dry white wine was studied.The main volatile components were alcohols,acids and esters.Isoamyl alcohol,phenylethanol,hexanol and isobutyl alcohol were the main alcohols.Ethyl decanoate,ethyl lactate,ethyl octanoate,ethyl acetate,ethyl laurate,ethyl acetate,ethyl hexanoate and isoamyl acetate were the main esters,which bring more floral and fruity aroma.Octanoic acid,acetic acid and decanoic acid were the main acids.The content of other volatile substances was low,and the difference was not significant.Among the Chardonnay dry white wine by clarified juice fermentation technology,the mixed fermentation of Mp7 and Saccharomyces cerevwasiae has higher content of ethyl acetate and ethyl octanoate,which were 11.15 mg/L and 13.37 mg/L,at the same time,the citronellol content was higher,which was 1.15 mg/L and can bring more abundant rose and citrus aroma.The alcohols content was relatively low,which can reduce green flavor.Among the Chardonnay dry white wine made by grape skin maceration fermentation technology,the mixed fermentation of Mp1 and Saccharomyces cerevwasiae has higher content of isoamyl alcohol and phenylethanol,which were 57.69 mg/L and 33.54 mg/L.Phenylethanol has honey and rose fragrance.Citronellol content was the highest,which was 0.46 mg/L and can bring more abundant rose and citrus fragrance.The mixed fermentation of Mp7 and Saccharomyces cerevwasiae has higher content of ethyl lactate,ethyl acetate,isoamyl acetate,ethyl caproate,ethyl octanoate and ethyl decanoate,which were 13.49mg/L?5.19 mg/L?3.05 mg/L?3.08 mg/L?3.38 mg/L and 3.79 mg/L,the ester fragrance was richer and more balanced.