Isolation,Identification And Application Research Of Yeast In Traditional Dairy Products

The identification and biodiversity of the yeast involved in Tibet Qula were investigated. The yeast flora of Tibet Qula were analyzed. The influence of2yeasts strains, Kluyveromyces marxianus Ml and Saccharomyces cerevisiae B2,on the characeristics of fermentation milk was discussed. The results provide the basic data for systematically understanding the characteristics of Tibet Qula, give useful information for further utilization of yeast in traditional fermented milk products. The results also provide the theoretical support for developing new fermentation agent and new fermented milk products, so as to promote the dairy industry development.The cotmts of yeast in Qula samples collected from Tibet were ranged from5.70-7.21Log cfu/g. A total of36yeast strains were isolated from11traditional Qula samples in Tibet of China. The traditional physiology method and molecular method were used to identify the yeast strains isolated from Qula in Tibet. The predominant strains proved to be mainly Debaryomyces hansenii(3%.9%of the total isolates) and Saccharomyces cerevisiae (19.4%). Others were identified as Kluyveromyce smarxianus for four strains, Torulaspora delbrueckii for four strains, Candida zeylanoides for three strains, Pichia fermentans for one strain, Clavispora lusitaniae for one strain, Rhodotorula mucilaginosa for one strain, Kluyveromyces lactis for one strain. There existed that yeasts of great biodiversity Qula in Tibet, but quite different from each other. Debaryomyces hansenii-Torulaspora delbrueckii and Debaryomyces hansenii-Candida zeylanoides were the predominant groups in Qula.In details,the growth of lactic acid bacteria during fermentation was inhibited by the addition of Saccharomyces cerevisiae B2. The addition of lactic acid bacteria advanced the growth of Kluyveromyces marxianus Ml and Saccharomyces cerevisiae B2. A positive interaction between Saccharomyces cerevisiae B2and lactic acid bacteria was observed during cold storage to improve the viability of each other. Yeasts on the effect of texture of fermentation milk was not significantly. The samples added yeasts did not produce more peptide. The content of NNH2and free amino acid were decreased.