A study on yoghurt production from frozen stored goat, sheep and buffalo milk and properties of yoghurt

In this research, it was aimed to determine the physical, chemical and sensory properties of yogurt made from frozen and freeze-storage the milk of goat, sheep and buffalo. For this purpose, pasteurized goat, sheep and buffalo milk were frozen and stored at -20 °C for three months. In the 0., 1., 2., and 3. months of storage, frozen milk was thawed and yoghurt was made with set type yogurt production, and the physical, chemical and sensory properties of the stored yoghurts were examined on the 1st, 7th and 14th days. According to the results obtained it has been determined that freezing and storing of milk does not cause a statistically significant change (p>0.05) in dry matter, fat, protein, titration acidity and pH values in yoghurt samples. An increase in titration acidity and a decrease in pH values occurred, during the 14 day storage period of yoghurt. Sheep yogurt showed the lowest amount of whey separation and highest water holding capacity, while goat yogurt showed the lowest water holding capacity and highest whey separation. During the storage period, the amount of whey separation increased and water holding capacity decreased in all three yoghurt types. The amount of phenolic content in yoghurts decreased due to the freezing of milk and this decrease was found statistically (p <0.05). Changes in color values occurred and L* values decreased significantly (p<0.05) during freeze storage. The best textural properties showed buffalo yogurt, followed by sheep yogurt and then goat yogurt. In sensory evaluations the parameters of all samples examined by panelists were liked and goat yogurt was close to good, sheep and buffalo yogurt were more than good. In addition, it was observed that the raw material of yogurt was made of different milk, and the physical, chemical and sensory properties of yoghurts produced differences. Sheep yogurt showed the best features, while goat yogurt received the lowest values. Key words: Yogurt, frozen milk, goat yogurt, sheep yogurt, buffalo yogurt