Study On The Influence Of The Yeast On Lipids Metabolism In Traditional Dairy Products

Lipids, one of three main nutrition, had attracted more and more attention from the popularity. And also yeast is a kind of microbe which people understand most deeply. At the same time, dairy products is the focus of the topic in social life now. The combination of the three will determine the future direction of research and detonate the enthusiasm of the people.In this environment, using the reconstructed milk as the substrate, research the interaction conditions of the lactic acid bacteria and yeast and explore the influence on lipid metabolism while adding some yeast. In addition, determine the influence on the texture, the flavor substances and some other factors while adding some yeast.First, dealing from the chosen of the yeast in the article, as the index to level of producing lipase enzyme, choose two kind of yeast—Saccharomyces cerevisiae and Kluyveromyces as the strains studied whose level of producing lipase enzyme is higher in the five kind provided by the lab. Study the growth curve of the lactic acid bacteria and yeast, and research the symbiotic condition of the two strains. As the index to the colony counts of the lactic acid bacteria, determine the optimal reaction conditions of the lactic acid bacteria and yeast by single factor and orthogonal experiments:the temperature of36℃, the concentration of the reconstructed milk of8%, the inoculum106(cfu/mL) and the proportion of inoculation30:1in order to get the most lactic acid bacteria survival numbers. Prove that the survival number of the lactic acid bacteria will reach2.83×10cfu/mL.Secondly, in the main part of the experiment, reach the metabolism of the lipids such as cholesterol, fat and some main fatty acids while adding the yeast into the fermentation broth or not. The content of the cholesterol reduce significantly after adding the yeast and the decline will reach21.04%., The influence of adding yeast on fat metabolism is exactly the same situation with cholesterol, and the massive accumulation of the fatty acids confirms this conclusion from the side. By means of the experiment conclusion above, it proves that adding the yeast into the fermentation broth will promote the decomposition of the cholesterol and the fat and also promote accumulation of the fatty acids. All these phenomenon illustrate the argument inadequately that yeast will promote the lipid metabolism.Finally, determine the influence of adding yeast into fermentation broth on the characteristics of texture and the content of the flavor substances. It proves that the content of flavor substance shows a substantial increase in the tend on the whole after adding the yeast into the fermentation broth, and the textural properties of the fermentation broth changes even more obviously. And determine the changes of pH and the acidity after adding the yeast.The final results of the experiments shows that the mixed fermentation broth after adding yeast not only promote the metabolism of the lipids and the accumulation of the fatty acids, but also increase the content of the flavor substances and the indexes of the characteristics of texture. All the conclusions above proves that adding some yeast as a beneficial bacteria into fermented dairy products is definitely more good than harm.