Microbial Screening And Fermentation Technology For Low Alcohol Milk Wine

The core of koumiss fermentation is the selection of strain and optimization of fermentation technology.Therefore,separation and screening of high-quality yeasts and the research and improvement of key control points in the koumiss fermentation lay a good foundation for the development of low-alcohol dairy products with new tastes and functions.In this research,the yeasts are separated and screened out from special dairy products,such as Kefir Grains,natural fermented milk and Kefir fermented liquid.Then,WL differential medium is used to identify the culture and conduct morphological taxonomy of saccharomycetes,26S rDNA PCR-RFLP molecular identification method is used to identify that the yeasts reach the species level and a high-quality yeast that is grown and fermented in the cow's milk is screened out through the physical and chemical property test,such as only carbon source of lactose and heat resistance.By determining the pH value,alcoholic strength and other index,the interaction of the yeast with lactic acid bacteria(Streptococcus thermophilus and Lactobacillus bulgaricus)in the koumiss fermentation is studied by combining the Saccharomyces cerevisiae.Finally,the optimal fermentation technology and conditions of low-alcohol koumiss are confirmed by the orthogonal experiment of milk content,sugar content and other factors.166 strains yeast were isolated from Kefir Grains,natural fermented milk and Kefir fermented liquid in this study.Among them,43 strains yeast were isolated from Kefir Grain,87 strains yeast were isolated from naturally fermented milk,36 strains yeast were isolated from Kefir fermentation liquid.Observation of colony morphology and microscopic morphology using WL differential medium that the yeasts were divided into 14 types,after 26S rDNA PCR-RFLP molecular identification and sequencing were divided into 10 kinds of different species of yeast,there were Kluyveromyces marxianus,Ciyptococcus sp.,Saccharomyces cerevisiae,Candida tropicalis,Issatchenkia terricola,Pichia guilliermondii,Rhodotorula mucilaginosa,Candida zeylanoides,Pichia fermentans and Torulaspora delbrueckii.The Kluyveromyces marxianus that is screened out by the physical and chemical experiment is grown and fermented well in the cow's milk and the generated alcohol is up to 5%by using the lactose.By combing the Saccharomyces cerevisiae and after adding lactic acid bacteria in fermentation,the total number of yeasts increases by 2 times,the generation of alcohol strength is increased and the taste of koumiss is improved.There is a mutualistic symbiosis relation between yeasts and lactic acid bacteria.The milk content,sugar content,initial pH value and fermentation time that affect the fermentation technology are studied.Two types of koumisses are obtained by the orthogonal experiment of four factors and three levels:primrose pure koumiss and milky thick koumiss.The optimal fermentation conditions of pure koumiss are:milk of 60%,sugar of 100g/L,initial pH value of fermentation of 3.5 and fermentation time of 3d.The alcoholic strength of final koumiss product is about 4.0%,characterized by elegant and pure frankincense,full body and refreshing property.In conclusion,by combining the traditional morphological taxonomic method and molecular biological method,this research separates and identifies the yeasts screened out from special dairy products,studies the physical and chemical property of yeasts and optimizes the koumiss fermentation technology,thus laying a theoretical foundation for the making of new koumiss products to promote the development of dairy product industry in China.