Screening Of Superior Strains And In-situ Fermentation Process Research In Fermentation Of Shanxi Aged Vinegar

Yeast?Lactic Acid Bacteria and Acetic Acid Bacteria are important microorganisms in the fermentation process of Shanxi aged vinegar.The acetic acid produced by Acetic Acid Bacteria laid the foundation for the acetic acid taste of Shanxi aged vinegar.The presence of non-volatile organic acids such as lactic acid produced by Lactic Acid Bacteria can alleviate the strong irritantness caused by excessive acetic acid content.The vinegar tastes mild sour and tasty.The ester-producing Yeast can convert acids and alcohols into ester compounds under the catalytic action of enzymes and release aroma substances,such as ethyl acetate,ethyl lactate,etc.They can increase the fragrance of Shanxi aged vinegar,This experiment selected high lactate-producing Lactic Acid Bacteria and ester-producing Yeast from the fermentation process of Shanxi aged vinegar.Intensified application to the Alcohol fermentation stage of Shanxi's aged vinegar.On this basis.Lactic Acid Bacteria and Acetic Acid Bacteria were applied to the acetic acid fermentation stage.Optimize the fermentation process through single factor experiments and response surface design to determine the optimal process parameters.The dominant strains were co-fermented to enhance their role in the fermentation process,to increase the lactic acid content and aroma components,reduce biting tasteand and lay the foundation for upgrading the quality of Shanxi aged vinegar.The result is as follows:(1)Through the acid production quantitative test and tolerance test,35 strains of lactic acid bacteria isolated during the fermentation of Shanxi aged vinegar were screened.Finally screened out strains with high acid production and good tolerance:JL6,CL21.The acid production amount was 10.02g/100mL and 9.73g/100mL respectively.Higher than commercial strains Lactobacillus thermophilus(2.21g/100mL)and Lactobacillus acidophilus(3.09g/100mL).The 16S rDNA was identified as Lactobacillus fermentum and Lactobacillus caseu respectively.(2)The 15 strains of yeast isolated during the fermentation of Shanxi aged vinegar were screened to determine the ability to produce esters,compared with the commercially used Angelica fragrant dry yeast.and a series of ethanol-tolerance,high-sugar?tolerance,and low-pH resistance were adopted.Tolerance tests.such as the screening of a more advantageous ester-producing yeast.The ester production test showed that the ester production of five strains of Y11-Y15 was higher than that of Angel's dried sweet yeast(2.68g/100mL),of which Pichia pastoris Y12 produced the highest ester yield,reaching 3.86g/100mL.The results of temperature,alcoholity,acidity and sugar tolerance tests showed that strain Y12 with the highest ester-producing capacity had strong tolerance to alcohol,but had poor tolerance to acidity,and ester production of strain Y13 was slightly lower than that of strain Y12.Y12 showed the smallest difference in the four?factor tolerance test.In combination with the ester-producing test and tolerance test,the strain that was selected for the next phase of enhanced application was Pichia pastoris Y13.(3)The selected high-tolerance lactic acid bacteria Lactobacillus fermentum JL6 and ester-producing yeast Pichia pastoris Y13 were jointly applied to the winery stage of Shanxi aged vinegar.The content of total esters and total acids in the wine is used as an indicator,Based on single factor tests.Design and optimization of the optimum process parameters for the mixed fermentation of the winery stage:The total inoculation of lactic acid bacteria was 3.67%,the ratio of lactic acid bacteria to yeast was 1.9:2.0,and the fermentation time was 7.5 days.The average value of total esters measured under this process condition was 1.50 g/100 mL,and the average value of total acid was 1.74 g/100 mL.Application of Lactobacillus casei CL21 and Acetobacter pasteurium A3-8 in the vinegarification stage.On the basis of single-factor tests,optimization of the optimal process parameters through response surface tests is:The inoculation of lactic acid bacteria with acetic acid bacteria was 3.3%,the ratio of lactic acid bacteria with acetic acid bacteria was 1.10:1,the inoculation time was 2.5 d,and the total acid reached 6.15 g/100mL.Through the determination of aroma components,lactic acid content and total acid,non-volatile acids,total esters and other basic physical and chemical indicators.The commercial Shanxi old vinegar was used as a control.Discovered optimized mixed fermentation process increased vinegar's total acid content by 4.77%,Total ester increased by 3.57%,Lactic acid content increased by 8.72%,Aroma components have increased in type and relative content.lt shows that the strengthening of lactic acid bacteria,yeast and acetic acid bacteria can effectively increase the content of aroma components such as lactic acid and esters in Shanxi aged vinegar,improve taste and improve quality.