Screening Of Excellent Strains Of Traditional Homemade Koumiss And Development Of Pure Culture Starter

Koumiss is a kind of traditional fermented dairy product with rich nutrition and unique taste,which is deeply loved by Mongolian and Kazakh minorities in China.Koumiss has many physiological functions,such as improved gastrointestinal system and enhanced immunity,reduce blood press and blood fat,adjunctive treatment with tuberculosis,to mention a few.At present,koumiss can only be fermented by traditional starter,and traditional starter is a natural fermentation culture,it can be easily changed by the cultured environment and the geographical sources.In the industrial production of traditional starter,the limitations,volatility and unknown microorganisms of traditional starter restrict its further development.In order to solve these shortcomings,this study mainly focuses on the following three aspects,the screening and identification of excellent strains of traditional homemade koumiss,the development of pure culture starters and optimization of fermentation,and the development of DVS koumiss starter cultures.The result will provide the basic theory for industries.The main conclusions are as follows.Firstly,10 dominant strains were screened out by acid production and fermentation performance tests.The results showed that 2 strains of Lactobacillus plantarum,2 strains of Lactobacillus paracasei,and 1 strain Lactobacillus casei,3 strains of Kazachstania unispora,1 strain Candida glabrata,and 1 strain Pichia fermentans.The fermentation characteristics of the six strains were studied.The six strains was suitable for the production of fermented dairy products and was conducive to improving production efficiency.The fermentation characteristics analysis showed that the six strains was suitable for the production of fermented dairy products.Secondly,the six kinds of traditional homemade koumiss were evaluated on sensory and flavor.Koumiss ZK showed the best flavor and sensory.The volatile components analysis showed that the content of aromatic substances in koumiss ZK is very high.It matched to the result of sensory experiments.The pure culture starter was developed-(Lpcs:Lcs:Lpl:Y2:Y7=3:1:2:1.5:1.5).The flavor of fermented koumiss is very close to the koumiss ZK.Compared with koumiss ZK,the novel fermented milk showed the higher nutritional value,and its potential probiotic properties is better.It demonstrated the experiment was successful.The optimum fermentation process conditions were determined as follows:inoculum concentration was 2.79%,fermentation temperature was 23.4℃ and fermentation time was 73.59h.The maximum predicted value of koumiss sensory score was 79.56.Thirdly,PB and orthogonal experiment design were used to study the effects of different protective agents on the survival rate of freeze-dried bacteria.The optimum protective agent formulation was 15%skimmed milk,15%trehalose,10%sorbitol,and 5%sodium glutamate.The survival rate of Lactobacillus reached 86.54%and the survival rate of yeast was77.78%.Pure culture of the lactobacteria and yeast still kept high activity for starting fermentation.By using this pure culture,the inoculation ratio could be reduced by more than 100 times compared with the fresh strain.This is consistent with the inoculation requirement of direct inoculant fermentation.