The Isolation And Identification Of Lactic Acid Bacteria And Their Application As Cheese Starter

The lactic acid bacteria were isolated and identified from five samples collected, which were screened and used as cheese strain of Chinese tastes for making cheese starter. Through studying the value changes of physico-chemical characteristics and microrganism during cheese ripening, The work was as follow:15 strains of lactic acid bacteria, 10 and 5 strains were lactobacillus and lactococcus respectively, were selected and initially identified as 5 genera that were Lactobacillus, Enterococcus, Streptococcus, Lactococcus and Leuconostoc including 4 Lactobacillus plantarum (L.plantarum), 3 strains of Lactobacillus pentosaceus (L. Pentosus), 2 strains of Lactobacillus casei (L.casei) and 1 strain of Lactobacillus rhamnosus (L.rhamnosus). Among them 7 strains were better by detecting whey output, style and acid production in culture of skim milk during 14 hours clotting of fermented, and which were used to assay pH4.6 soluble nitrogen content, viscosity and acid conditions in fermented milk. The results showed that Lactobacillus strains K-2 (L.lantarum) and lactic acid streptococcus F-1 (Streptococcus lactis) were selected, and theirs acidity during the milk curd, respectively, were 75.2 and 76.3. Besides, amount of growth of mixed culture, K-2 and F-1, was much higher than that of K-2 or F-1 alone at the time of stable stage. In addition, acid output of mixed strains was more than that of ones. Therefore, K-2 and F-1 strain have a good alternate role that can be used as the preferred mixed yeast strains for semi-hard cheese starter. In the study, we have further determined best ratio of K-2 and F-1 that was 5:1, and the optimum dosage was 5% (v / v). Testing various physical, chemical and microbial indicators during cheese ripening process demonstrated that: pH 4.6 soluble nitrogen and 12% TCA soluble one rised but texture decreased. For pH, the value reduced rapidly during 2 weeks, lately it rised slowly and kept invariable. The number of microorganisms decreased rapidly early and kept stable eventually, In conclusion, we could knowed that the time of best quality of cheese was about 6 weeks .