Study On The Isolation, Identification And Applying Of Predominate Microbiology From The Dried Beef

The microbiological change during the natural fermenting and ripening processing of dried beef by the selective Medias including PCA(Plate Count Agar), PCA+, MRS (de Man, Rogosa, Sharpe Agar) , MRS+ and VJ(Vogel Johnson Agar) were analyzed. The result showed that the total bacteria and the population of Micrococcus, Lactic acid bacteria, Lactobacillus, Staphylococcus had a lightly increase, but the population of different species had a slight decrease at the end of the processing. The population of Micrococcus was 107~108cfu/g and the other species was 105 ~ 107cfu/g in the dried beef product.There were 70 strains isolated from each of the MRS and VJ at the different stage of the processing of dried beef. Staphylococcus warneri, Staphylococcus sciuri, Staphylococcus auricularis, Bacillus subtilis, Staphylococcus xylosus, Staphylococcus saprophyticus, Lactobacillus plantarum and Pediococcus pentosaceus were 8 predominate bacteria. The growth curve of predominate bacteria was studied. The result showed that growth of Pediococcus pentosaceus was faster than that of Lactobacillus plantarum; the growth of Staphylococcus sciuri is fastest and Staphylococcus auricularis was slowest.The endurance to salt and nitrite of the 8 stains isolated from dried beef was studied, the result showed that the endurance to salt of Staphylococcus sciuri, Staphylococcus xylosus and Staphylococcus saprophyticus was most strong, they could grow at the salt content of 15%. The endurance to salt of Pediococcus pentosaceus is higher than Lactobacillus plantarum. 8 strains isolated all had the ability to resist the nitrite.The lipolytic and proteolytic activities of the 8 strains by the special Media were studied. It showed that Staphylococcus warneri, Staphylococcus saprophyticus and Lactobacillus plantarum had the proteolytic activity. The proteolytic activity of Staphylococcus sciuri was weak, and the liplolytic activity of Staphylococcus xylosus was weak. Lactobacillus plantarum had lipolytic activity. Bacillus subtilis not only had the lipolysis but also had proteolysis.Single strain's fermenting experiment showed that, the effect of different strain to the pH, acidity, the total amino acid were not signifient, Pediococcus pentosaceusand Lactobacillus plantarum could improve the content of free amino acid in dried beef. Staphylococcus sciuri, Staphylococcus auricularis, Bacillus subtilis, Staphylococcus xylosus and Staphylococcus saprophyticcus affected the content of different free amino acid. Staphylococcus auricularis, Staphylococcus xylosus and Pediococcus pentosaceus had a signifient effect to the sensory quality of dried beef, Pediococcus. pentosaceu had a most signifiennt effect to improve dried beef's quality. According to all the factors, Staphylococcus xylosus, Lactobacillus plantarum and Pediococcus pentosaceus were proved to be appropriate.The fermented traits including acidity, free fatty acid and animo acid basic nitrogen in dried beef were studied. Optimum proportion of Staphylococcus xylosus, Lactobacillus plantarum and Pediococcus pentosaceus were gained by orthogonal test L 9(3)4. The result showed that, the optimum proportion of Lactobacillus plantarum Pediococcus pentosaceus and Staphylococcus xylosus was 1:1:1, the viable cell counts was 107cfu/g.