Application Of Lactobacillus Plantarum K25in Fermented Milk

Recently, the probiotics, of which80%were used in fermented dairy products, are widely applied in food industry at a rate of yearly growth as high as25%in our country. However, most of the domestic probiotic dairy products are manufactured with the foreign starters, and the industrialization of probiotic products which have independent intellectual property rights and are suitable for Chinese physiological features has not been achieved. In this study, the technological properties of a potential probiotic strain. Lactohacillus plantarum K25isolated from Tibetan kefir as well as its application in fermented milk were studied. Furthermore, the effects of fermented milk containing L. plantarum K25on the cholesterol-lowering and antioxidative abilities of mice were also investigated. The research results were showed as following:(1) The technological properties of a probiotic strain L. piantarum K25were studied. The results showed that the strain displayed weak milk-coagulating activity, moderate proteolytic activity and strong autolytic activity.The strain also showed a strong antimicrobial activity against Shigella. while no inhibition was observed towards the commercial yogurt starters. Antibiotic susceptibility test found that the strain was sensitive to erythrocin. Among all the bacteria-inhibiting agents in the test. low concentration bacteria-inhibiting agents did not significantly affect the growth of the strain. Furthermore, the strain maintained high viability in fermented milk during storage at4℃. and it did not cause post-acidifying profile to fermented milk.(2) Probiotic fermented milk containing L. plantarum K25was made.The results showed that the strain had no undesirable effect on the quality of fermented milk During the21days of storage at4℃. the strain exhibited no inhibition towards the commercial yogurt starters and could maintain high survival ability in fermented milk, with viable counts more than10CFU/mL at21d.Compared with the probiotic fermented milk and control fermented milk, there were no significant differences(P>0.05) in pH value, titratable acidity.gel strength.water-holding capacity.viscosity and diacetyl content of fermented milk.The results of sensory evaluation toward the fermented milk showed probiotic fermented milk containing L. plantarum K25had no undesirable influence on taste, texture or color.Furthermore. the score of probiotic fermented milk was slightly higher than that of control.Based on above conclusions, L. plantarum K25is suitble for the manufacture of probiotic fermented milk making as an adjunct culture.(3) The effect of fermented milk containing L. plantarum K25on the cholesterol-lowering ability of mice fed on high-fat diet was studied. The results showed that L. plantarum K25 fermented milk significantly lowered the levels of serum total cholesterol, low-density lipoprotein cholesterol and atherosclerotic index. The level of serum low-density lipoprotein cholesterol increased significantly (P<0.05).In addition. L. plantarum K25fermented milk significantly increased the population of lactobacilli in the fecal (P<0.05). but it did not change the number of Escherichia coli as compared to control.(4) The antioxidative effect of fermented milk containing L. plantarum K25on the aged model mice induced by D-galactose was also studied. The results showed that L. plantarum K25fermented milk could significantly increase the SOD activity. GSH-Px activity and total antioxidant capacity (T-AOC) in aged mice liver tissue, whereas significantly lower the MDA content in serum (P<0.01)...