GC-MS Analysis of Yogurt Fatty Acids

The fatty acid analysis of the yogurt samples was examined by GC-MS (Agilent Technologies Inc. Santa Clara, CA) following the method outlined by Ajmal et al. (2019) [44 (link)]. In brief, the yogurt samples were subjected to total lipid extraction using a chloroform: methanol (2:1) mixture. Subsequently, 30 μL of the extracted lipid was transferred to a 10-mL centrifuge tube, and 2 mL of hexane and benzene mixed reagent (1:1) was added and gently shaken to facilitate dissolution. Next, 2 mL of a solution containing 0.5 mol/L potassium hydroxide in methanol was added to the mixture, and the contents were shaken. The tube was allowed to stand at room temperature for 30 min, following which distilled water was added to cause the methanol solution in the organic phase to separate and rise to the top of the tube. Lastly, the supernatant was carefully extracted from the top layer after allowing the mixture to stand for 10 min in preparation for further analysis. The extracted samples were subjected to analysis using GC-MS (Agilent Technologies Inc., Santa Clara, CA, USA) with a DB5 capillary column (J&W Scientific, Agilent Technologies Inc., Santa Clara, CA, USA). The identification and quantification of individual fatty acids in the samples were accomplished by comparing their retention times and peak areas with those of corresponding standards.