Boza is a dense beverage of sour taste. The taste may vary according to the amount of added sugar, the type of cereals and micro-organisms used, and the length of fermentation. It is a typical beverage found in Albania, Bulgaria, Romania, Turkey and other Balkan countries. In Turkey, warm boza is consumed primarily during the winter due to the effect of warming of the body and as a result it is expected to help against seasonal respiratory infections. In Romania, they drink chilled, refreshing boza, especially during the summer months. As it contains vitamins A, C, E and four types of vitamin B, it is a valuable nutrient for physically active people. It is especially suitable for vegetarians and vegans, since it is entirely plant-based, and is a good source of vitamins and a good substitute for milk drinks. In the present Master's degree thesis, a change in pH of the mixture of flour and bacteria was monitored in order to determine how quickly the pH of mixture decreases. We found that the rate of pH decrease of mixtures from various types of flour and also with the addition of different bacteria types differs. We also found that the pH of the mixtures 48 hours after the addition of bacteria differs according to the type of bacteria added. We also carried out titration of the boza mixture in order to determine the amount of acid produced during the fermentation process. We found that for a boza mixture prepared with starch, the addition of any type of bacteria does not require a lot of base in order to neutralize the acid produced during the fermentation process. We were also interested in the growth of bacteria in the sample, which was assessed with the Petrifilm® plate. We described the growth curve of bacteria obtained from sour cream in an millet flour. By means of gas chromatography and mass spectrometry, the volatile substances in the boza samples were determined qualitatively and quantitatively on several occasions, in order to evaluate if and how these volatile substances change during fermentation. We demonstrated that the content of some of the analyzed volatile substances varies significantly during fermentation. Finally, we reviewed and analyzed the objectives that pertain to our topic in the curriculum for primary schools, to assess how these topics are represented in certified textbooks. On the basis of our experimental work, we developed two worksheets for pupils, as an alternative to the previously described experiments (i.e. acidification of milk) on the topic of fermentation.
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