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In this study, probiotic homemade yogurt was made by using a commercial probiotic culture and its quality parameters were investigated on the 1 st , 5 th , 10 th and 15 th days of storage. For this purpose, probiotic and non-probiotic commercial yogurts were also investigated as control groups. According to the results obtained; level of total lactic acid bacteria, Lactobacillus acidophilus and Bifidobacterium animalis ssp. lactis and pH values were not significantly changed in storage time for all samples (P >0.05). Any significant number of coliforms, mould or/and yeast were not observed in all samples (<10 CFU/g). Dry matter values were found similar among the milks used in yogurt makings, while fat and protein values showed difference. The homemade yogurt was not highly preferred by the panellists; however, it did not show any significant difference in the evaluation compared to the other yogurts (P >0.05).

Background: The detection of lactate is an important indicator of freshness, stability, and storage stability of products as well as degree of fermentation in food industry. In addition, it can be used as a diagnostic tool in patients’ healthcare since it is known that the lactate level in blood increases in some pathological conditions including septic shock, tissue hypoxia, and sepsis. Thus, determination of lactate level plays an important role in not only food industry but also health fields. At this point, biosensor has become important to detect lactate due to having many advantages like rapid, cheap and easy to use. Methods and Results: In the current study, amperometric lactate biosensors based on lactate oxidase immobilization (with nafion 5% wt) were designed and limit of detection, linear range and sensitivity values were determined, which were found as 31 μM, 50-350 μM and 0.04 μA.μM-1.cm-2, respectively. Then, it was used for the measurement of lactic acid produced by 6 different and morphologically identified presumptive lactic acid bacteria (LAB) which were isolated from different naturally fermented cheese samples for this study. Then, the biosensors were used to perform lactate measurements successfully within 3 minutes for each sample even few of them were out of the limit of detection. Conclusion: Electrochemical biosensors should be alternative and quick solutions for measurement of lactate metabolites instead of using classical methods which are required long working time. Besides, it is the first study to measure lactate produced by foodborne LAB as real sample with a biosensor.