Isolation,Identification And Influence Of Wine Quality Of Malolactic Bacteria From Hexi Corridor In Gansu

Lactic Acid Bacteria is a fermentation bacterium of Malolactic fermentation?MLF?,which converts L-malic acid into L-lactic acid,reduces the acidity of wine,and improves its microbial stability and flavor quality.However,most of the lactic acid bacteria that currently dominate MLF in China are imported commercial strains,which makes the quality of wine in different producing areas more serious.In addition,the long-term domestication of these commercial strains will pose a“species invasion”threat to the unique microbial resources in China,which is not conducive to the development of domestic wines.Therefore,it is of great significance to strengthen the screening and application of lactic acid bacteria in local apple-milk fermentation,and to present and shape domestic wines with regional characteristics.In this experiment,the lactic acid bacteria were isolated from the dried red wine of Gansu Qilian Wine Industry Co.,Ltd.using modified MRS medium.The lactic acid bacteria were screened by physiological and biochemical identification,malic acid decomposition and fermentation tolerance determination.And carry out wine brewing trials.On the basis of physical and chemical index determination and safety evaluation,the effects of preferred strains on the aroma components,color parameters and sensory quality of wine were analyzed,in order to provide theoretical basis and technical support for the collection and application of local lactic acid bacteria.The results of this study are as follows:1.24 strains of lactic acid bacteria were obtained by modified MRS separation medium.Five strains of lactic acid bacteria with good acid-reducing ability were screened by physiological and biochemical identification,malic acid decomposition,etc.,and three Pediococcus parvulus of Pediococcus were obtained by 16S rDNA analysis.Tolerance analysis experiments showed that P.parvulus C30 has low fermentation temperature?15°C?,high SO ₂ concent?50 mg/L?and high ethanol?14%?tolerance.2.The winemaking experiment showed that the P.parvulus C30 could complete the malolactic fermentation,and had no significant effect on the total phenol,tannin and total anthocyanin content in the wine sample.Compared with the commercial strains,the fermentation time?21 d?was shorter,the total anthocyanin content was significantly higher,the acid-reducing ability and the extracellular polysaccharide concent were not significantly different,and the biogenic amine and ethyl carbamate content is in line with international limit standards.3.Compared with commercial strains,the P.parvulus C30 fermented wine samples have fewer aroma substances,and the substances that exhibit floral and fruity aroma?ethyl hexanoate,diethyl succinate,phenylethyl alcohol,etc.?are low in content.However,the content of special aroma substances?n-pentanol,ethyl undecanoate,rose rosin,etc.?such as rum scent and baking scent is high.4.According to the analysis of color parameters,compared with the non-MLF wine sample,the L*value and the yellow b*value of the P.parvulus C30 fermented wine sample increased,the red a*value and the color saturation C*value decreased.Compared with commercial strains,the b*value,C*value and H*value of the wine sample were not significantly different,indicating that it had no significant effect on wine color.