Physicochemical and rheological properties, volatile flavour components, fatty acid composition and conjugated linoleic acid content of kökez strained yoghurt produced by traditional method

In this study, some chemical, microbiological and rheological properties as well as the volatile flavor components, fatty acid compositions and conjugated linoleic acid (CLA) contents of Kökez strained yoghurt samples (n=29) produced and obtained in 7 different months (August 2017, November 2017-April 2018) in the Kökez village of the Burdur city center were determined. As a result of the chemical analysis of strained yoghurt samples, average dry matter, protein, fat, fat in dry matter, pH, and acidity values were 26.84±1.49%, 11.24±1.58%, 8.40±0.61%, 31.33±1.77%, 3.58±0.19 and 1.80±0.21%, respectively. The average L*, a* and b* color values of the samples were 89.82±2.03, 2.27±0.64, and 8.92±0.71, respectively, while the average apparent viscosity was 14.06±5.23 Pa.sn, consistency coefficient 208.43±81.79 Pa.sn, flow behavior index 0.19±0.04, and thixotropy value was determined as 22007±21423 Pa/s. Although the free fatty acid composition of the strained yoghurts differed in general, capric and lauric acids as medium chain fatty acids and oleic, palmitic and myristic acids as long chain fatty acids were dominant fatty acids, respectively. In yoghurts, 43 volatile compounds belonging to the chemical groups of alkanes (4), esters (4), acids (3), ketones (12), aldehydes (8), alcohols (4) and terpenes (8) were determined as volatile components, among these, terpenes, ketones and alkanes were the dominant volatile flavor components. The average CLA content of the samples was 3.64±0.54 mg/g fat. Average lactobacillus spp., lactococcus, total aerobic mesophilic bacteria and yeast-mold counts of strained yoghurt samples were 9.09±0.13, 8.60±0.46, 8.25±0.54, and 3.92±1.57 log cfu/g, respectively, and coliform bacteria were not present in the samples. Results indicated that there were significant differences among the producers in terms of the composition and physico-chemical properties of Kökez strained yoghurts with the exception of the protein contents of samples (p<0.05). The chemical composition and apparent viscosity values of samples were generally higher than those reported in the literature or industrial strained yoghurts.