Determination of Fatty Acids in Fish, Egg and Milk: A Comparison of Different Extraction Methods

In this study, direct methylation was compared with two conventional extraction methods (Soxhlet and Folch) in terms of extraction yield, the stability of configuration of fatty acids chemical structures and their effect on saturated and unsaturated fatty acids profile. Also, by evaluating and comparing fat extraction methods for fish, egg yolk and milk samples, the efficiency of these methods was determined according to the sample tissue. After extraction and esterification procedures, fatty acids were determined by gas chromatography method. The statistical method of ANOVA using GLM technique was applied to compare the mean of data. The fatty acid profile was subjected to analysis similarities based on cluster analysis to check how the methods would affect the fatty acid profile and to evaluate how much differences are between the methods. The obtained results indicated that the Soxhlet had the lowest efficiency for the extraction of fatty acids, especially in a sample of dry milk, but it was the highest precision compared with the Folch and direct methylation methods. It was also found that the methods have different ability to extract fatty acids based on their unsaturation degree. In general, extraction methods, in addition to affecting the fatty acid profile, have a different effect rate, depending on the sample tissue. Therefore, in order to select an effective method for extracting fat, it is necessary to consider the sample tissue.