| In order to solve the problem of wine homogenization,improve the characteristics and competitiveness of wine producing areas,in this experiment,the local Metschnikowia pulcherrima was used as the object of study,and different Saccharomyces cerevisiae and Metschnikowia pulcherrima were used as the control for the mixed fermentation in simulated grape juice with commercial Saccharomyces cerevisiae.The effect of interspecies differences of S.cerevisiae on the volatile components of the mixed fermentation was investigated,and the effect of M.pulcherrima differences on the aroma of the mixed fermentation was investigated through the mixed fermentation of three different strains of M.pulcherrima and S.cerevisiae.The effect of different fermentation temperatures,different inoculation ratios and S.cerevisiae inoculation times on the volatile substances of mixed bacterial fermentation was determined through the determination and comparative analysis of the volatile components of mixed fermentation under different fermentation conditions,and to further clarify the influence of M.pulcherrima mixed fermentation on volatile components,and provide theoretical reference for the industrial application of M.pulcherrima mixed fermentation of wine.The results show that:(1)Fermentation analysis of three local M.pulcherrima strains and commercial S.cerevisiae DS and their effects on volatile components.The results show that:Different Metschnikowia pulcherrima and Saccharomyces cerevisiae mixed fermentation had alcohol lowering effect,but there were differences among different Metschnikowia pulcherrima mixed fermentation,and sequential inoculation was better than simultaneous inoculation.Mp58 sequential inoculation had the highest alcohol lowering effect,which decreased 1.70% vol compared with S.cerevisiae single fermentation.Mixed fermentation of Metschnikowia pulcherrima could change the proportion of volatile substances,the proportion of higher alcohols was greatly increased,and the proportion of ethyl ester substances was relatively decreased.The proportion of higher alcohols in the simultaneous inoculation fermentation and the sequence inoculation fermentation of three strains of Metschnikowia pulcherrima was Mp54<Mp57< Mp58,and the proportion of higher alcohols in sequential inoculation was higher than that in simultaneous inoculation and fermentation,mainly showing that the yield of phenylethanol,isobutanol and n-hexanol increased.The yield of ethyl ester was opposite to that of higher alcohol.Comprehensive comparison alcohol reduction effect and the composition of volatile composition and proportion,DS-Mp58 mixed fermentation performance is the most preferred,for follow-up study.(2)Fermentation analysis of different commercial Saccharomyces cerevisiae mixed with Metschnikowia pulcherrima Mp58 and its effects on volatile components.The results show that: The intraspecific difference of S.cerevisiae is one of the dominant factors leading to differences in fermentation rate,ethanol reduction efficiency and volatile composition of mixed fermentation.At the same time,Metschnikowia pulcherrima Mp58 plays a role in modifying the type and content of flavor and volatile components of the wine.D254-Mp fermentation had the highest content of ethyl esters,DS-Mp and 4x4-Mp had similar aroma components,and esters and higher alcohols accounted for the highest proportion of total volatile substances.DS-Mp performed the best of all commercial Saccharomyces cerevisiae and Metschnikowia pulcherrima mixed fermentation combinations: DS-Mp had a slower fermentation rate,the highest glycerol yield(7.94 g/L),the lowest ethanol yield(8.42% vol),and the highest yield of higher alcohols,especially phenylethanol.In addition,the types and contents of aroma substances are balanced,and the content of terpene compounds is relatively high,which has positive significance to improve the flavor of wine,so it is more suitable for the production of low-alcohol wine.(3)Different fermentation temperatures had significant effects on the fermentation rates of both commercial Saccharomyces cerevisiae DS single fermentation and DS-Mp58 mixed fermentation.The ethanol yield of DS single fermentation was the lowest at 20℃,while the ethanol yield of DS-Mp58 mixed fermentation decreased with decreasing fermentation temperature.The total acidity of DS single fermentation decreased with decreasing fermentation temperature,while the total acidity of DS-Mp58 mixed fermentation was the opposite.The highest volatile species were found in both DS single fermentation and DS-Mp58 mixed fermentation at 25°C,and the highest percentage of aldehydes and ketones were found in DS-Mp58 mixed fermentation,while the highest percentage of ethyl esters was found at 15°C.It can be seen that the high temperature helps the production of aldehydes and ketones,and the low temperature helps the production of ethyl esters.the higher the percentage of Mp58 inoculation in DS-Mp58 mixed fermentation,the richer the volatile substances,the higher the production of higher alcohols,organic acids and terpenes;the ester substances decrease with the increase of the percentage of Mp58 inoculation,mainly in the production of ethyl octanoate,ethyl decanoate,ethyl 9-decenoate and ethyl heptanoate.In the DS-Mp58 mixed fermentation,the yield of isoamyl alcohol and phenylethyl alcohol gradually increased with the delay of DS inoculation time,and the most abundant volatile substances were obtained after2 days of Mp58 inoculation and then DS inoculation. |
