Changes in some properties of strained (Süzme) goat's yoghurt during storage

In this study, certain criteria pertaining to the quality of strained yoghurt produced from goat's milk were studied over a period of 45 days in storage. The titratable acidity of initial (set) and strained yoghurts was found as 56.04 and 108.91 °SH, respectively. The lactic acid and tyrosine values of the strained yoghurt were determined 1.38 mg 100 g−1 and 0.22 mg g−1, respectively. These properties remained almost constant over the period of storage. The acetaldehyde, acetone, and butanone-2 content of strained yoghurt on the first day were found 8.36, 3.01 and 1.62 mg kg−1, respectively, but diacetyl was detected in trace amounts. While the total amount of free fatty acids (FFA) in goat's initial yoghurt was 263.45 mg kg−1, total amount of FFA in goat strained yoghurt was 468.60 mg kg−1. The total amount of medium-long chain free fatty acids (293.16 mg kg−1) in strained yoghurt was significantly higher than those of short-chain (96.22 mg kg−1) and unsaturated free fatty acids (79.22 mg kg−1). Butyric, capric, myristic, palmitic, stearic and oleic acids were predominant free fatty acids in both yoghurts. Sharp decreases (except for C6) were observed in the level of individual FFA in strained yoghurt over the first 15 days. After this period, the level of FFA remained almost unchanged or increased slightly. Aroma and flavour score of strained yoghurt was higher than that of initial yoghurt. Panelists did not perceive any off flavour in strained yoghurt until the 45th day of storage.