Analysis Of Bacteria Group For Fermented Milk With Tibetan Linggu And Study On Compound Starter

At present, there is a dairy product called"Tibetan Linggu", It is said that: it come from a small village of Tibetan and it has many biological functions, and is widely consumed in urban areas. However people do not really understand the bacteria colony type and the fermentation mechanism of Tibetan linggu dairy, many people hold the suspicion to its fermentation dairy products, there exists lots of misapprehensions when consumed. In view of this question, correct understanding and the appraisal by using sciencific method for Tibetan linggu fermentation dairy products has become currently urgent. The experiment studied the fermentation technology of symbiosis bacterium grain,the isolation and identification of main strains of Tibetan linggu dairy,the relationship between change of microbial colony and other substances,the bacteriostatic action of fermented milk with Tibetan Linggu,screening of pure culture starters and fermentation technology et al. The result will direct people how to sciencifically eat and provide the basic theory for industries. The main research content and results are listed as follows:1. Through single test and orthogonal seleting optimal fermentation conditions of Tibetan Linggu fermented milk. three factor conditions which were the inoculation volume of starter culture, fermentation temperature and time were selected. The result indicated that, the inoculation volume of starter culture is 5%, fermentation temperature is 25℃, fermentation time is 20h, final Tibetan linggu fermented milk was chracterized as follow: smooth taste and good flavor.2. This paper investigated the variation of microbial colony, sugar content, ethanol production, and acid content in the fermented milk with Tibetan Linggu, and analyzed the intrinsic reason of the change of microbial colony by correlating it with the change of other substances. At the first 18h, Lactococcus is the most, the less ones are Lactobacillus, Leuconostoc, Acetobacter, and yeast. Lactococcus lowers from 18h, Leuconostoc and yeast lowers from 21h, and Acetobacter lowers from 24h. Lactobacillus keeps enhancing during the whole fermentation period. The change trend of microbial colony is not related to the physiological property of each microorganism, but also to the substances contents in the milk.3. The bacteriostatic action of fermented milk with Tibetan linggu in fermentative process were examined, and its effective dose and the heat-resisting performance were also studied. The result indicated that the Tibetan linggu had a certain inhibitory effect on the growth of EPEC,Staphylococcus aureus,Salmonella; the inhibitory effect of the mycelium containing fermented milk was stronger than fermented milk without mycelium, its bacteriostatic diameters is 13.1mm 18.0mm and 12.5mm 16.0mm respectively; Fermented milk has the strongest bacteriostatic to Staphylococcus aureus, next is the EPEC, and least resistance to salmonella; At the 21h, the bacteriostasis activities of fermented milk on several kinds of pathogens reached to the higher level; Both reducing the fermented milk concentration and heat-treatment were able to reduce its bacteriostatic action.4. Based on isolation,purification and appraising their physiology and biochemistry properties of microorganisms in fermented milk with Tibetan linggu, lactococcus, lactobacillus, yeast and acetobacter acetic in fermented milk of Tibetan linggu were confired as the predominance microflore of which. Lactococcus was attributed to 5 genus, as enterococcus faecalis,Enterococcus durans,Lactococcus lactis subsp cremoris,Leuconostoc. pseudomesenteroides,Leuconostoc Paramesenteroides,Lactobacillus respectively belonged to 3 genus, L.brevis, L.casei, L.acidlophilus; Yeast respectively belonged to 5 genus, Saccharomyces, Brettanomyces, Candida, Saccharomycodes; Acetobacter acetic was identified as Acetobacter rancens.5. Through predominance microflora which isolated from Tibetan Linggu yogurt, Tibetan linggu yogurt starter was producted by screening the fermentation performance Lactococcus, Lactobacillus and yeast. The optimal fermentation conditions were determined by the three factors and three leves orthogonal experiments L₉(3⁴). The optimal fermentation conditions were as follows: 2:2:1 of Cococus, Bacillus and Yeast; fermentation temperature is 34℃, fermentation time is 18h. The Tibetan linggu yogurt products had excellent texture, smooth taste, moderate sweetness and aciditions, dense alcohol and easter aroma, and short solidify time.