Comparison of homemade yoghurt and manufactured yoghurts in terms of their pH change during shelf life as an indication of lactic acid production due to the presence of probiotic bacteria

摘要

The aim of this experiment is to show the differences between pH changes of homemade yoghurt and four different manufactured yoghurts by looking at their lactic acid production during shelf life which is an indication of increase in number of lactic acid bacteria.ududMy research question was “Is there a significant mean difference between homemade and manufactured yoghurts in terms of their pH change during shelf life which is an indication of lactic acid production and number of increase in probiotic bacteria?”ud udIt was hypothesized that there will be a significant mean difference between the homemade and manufactured yoghurts in terms of lactic acid production during shelf life which is an indication of increase in number of probiotic bacteria. Homemade yoghurt will be the most acidic yoghurt, followed by the four different manufactured yoghurts.ududTo answer the research question and to test the validity of the hypothesis, pH values of the yoghurts which are incubated at 4ºC for seven days are measured by pH meter. Due to the increase in the number of probiotic bacteria, pH values of the yoghurts change because those bacteria make fermentation which produces lactic acid. The data is analyzed in order to specify if there is a significant difference after seven days of incubation in terms of the acidic property of the yoghurts.ududAs a result, yoghurts are placed in petri dishes and their pH values are measured at the end of 7 days (for control the data is taken each after 24 hours). Anova results showed that there is a significant mean difference between the homemade and the selected manufactured yoghurts which were incubated at 4ºC with respect to their pH change after 7 days incubation.ud