Comparison of the antibacterial effects of different fermented milk products; yoghurt, probiotic yoghurt and kefir on E.coli.

The aim of this essay was to investigate the antibacterial effects of different fermented milk products (yoghurt, probiotic yoghurt and kefir) and compare their antibacterial effects on E.coli. My research question was “Do commercial yoghurt, probiotic yoghurt and kefir have antibacterial effect and which of these products has the best antibacterial effect on Escherichia coli? My hypothesis was that; there would be a significant difference in the means of bacteria growth after mixing with the products and probiotic yoghurt would have the best effect. To test the research question and the hypothesis, experiments were conducted. The method used was counting the numbers of colonies that grow on agar media. For this, bacterial suspension containing E.coli was mixed with each test substance separately and diluted. Then these suspensions were inoculated on the agar and the numbers of colonies grown on agar were counted. The results of the experiment was analyzed with the appropriate statistical tests (descriptive statistics and ANOVA), it was seen that there was a significant difference between the means of the bacteria grown for different products, however, the hypothesis was rejected and yoghurt was accepted as the product which has the best antibacterial effect on E.coli followed by probiotic yoghurt and kefir