| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 97 === For this study, kefir fermented milk from screened with potential physiological activity and fermentation ability of a good orange juice, and fermentation can be maintained after the antioxidant capacity of orange juice the strains. Research will be activated after the use of fermented milk kefir flat MRS medium, were selected for better growth of 32 strains. According to the definition of lactic acid bacteria as Gram-positive bacteria, bacilli or cocci, such as the lack of activity indicators catelase. Tested for catalase activity, litmus milk test, as well as Gram-stain microscopy, to identify a total of 12 strains of lactic acid bacteria. To PCR-DGGE technology will remove duplication strains can separate 4 groups of different strains of lactic acid bacteria. Use of 16s rDNA fragment identification can be found k1 and Lactococcus lactis subsp. Lactis 98% of similarity. k2 strains and Lactobacillus plantarum, with 99% of similarity. K3 strain and the Lactobacillus kefiri, with 98% of the degree of similarity. 10 ℃ under a 48-hour fermentation, the strains were screened out of the fermentation of orange juice can not be effective. At 20 ℃ and 37 ℃ under a 48-hour fermentation, k2, k3, are fermented orange juice has a good capacity. k2, k3 strains can produce organic acids in orange juice resulted in decreased pH values, to avoid spoilage organisms in the processing of the pollution. Fermentation process, k2, k3 emerged within 48 hours of fermentation to make orange juice under the sampling point to increase its total content of phenolic compounds. At 20 ℃ and 37 ℃ using k2 and k3 orange juice fermentation, 24 hours later, the fermentation broth of DPPH free radical scavenging ability than the other three strains a stronger orange juice fermentation. Fermentation at 37 ℃ under the conditions of the majority of the fermentation samples of its total antioxidant activity are slightly lower than that of orange juice is not fermented, and the orange, after the fermentation broth of the reducing power and did not upgrade. k2, k3 strains in the 20 ℃ and 37 ℃ under the fermentation conditions, the organic acids generated features, will give a good flavor of fermented beverages. Their safety, processing suitability, functional, and can show that k2, k3 strains have become a good orange juice fermentation capacity of the potential of probiotics. And Lin, the results of 2001 compared to k2 and k3 can be found with the strains B. longum, L. acidphilus, L. bulgaricus comparison, in addition to acid resistance of L. acidphilus than k2 and k3 strong strains, the other two acid resistance of k2 and k3 are relatively weak strain. k2 and k3 strains will be a slight inhibition of bile salt, but it still has a salt tolerance, the tolerance levels are Level 2 (number of strains bile salt tolerant), from the above we can see that, by the fermentation of kefir Lactobacillus strains isolated from the k2 and k3, suitable for the processing of an orange, and has become a potential probiotic.
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