An Analytical Simplification for Faster Determination of Fatty Acid Composition and Phytosterols in Seed Oils

Abstract

The fatty acid composition and the amounts of individual and total sterols in vegetable oils are the main analyses applied in the food industry to establish the oil nature. While the fatty acid composition is a relatively simple, fast analysis, the determination of phytosterols requires a laborious and time-consuming sample preparation. Both methods require a relatively large amount of oil, which may be an important drawback when only small samples are available. In this study, an analytical procedure that combines the sample preparation of both determinations is proposed to analyze small amounts of seed oils. From a single sample preparation, the total analysis time was considerably shortened. By applying a total methylation, the triacylglycerols and free fatty acids were transformed into fatty acid methyl ester (FAME) derivatives. Likewise, free sterols were completely released from their conjugated forms. Then, the derivatized oil was fractionated by solid-phase extraction into two fractions containing the FAME and free sterols, respectively. Both fractions were analyzed by gas-liquid chromatography. The analytical changes introduced provided reliable results for the main fatty acids and the major sterols in terms of accuracy and repeatability. Compared to the standard procedures, the time for sample preparation was reduced by half. In addition, it was much less laborious and required less volume of organic solvents, which reduced considerably the total cost of analysis and solvent waste. Consequently, the method proposed can be adopted as routine analysis in laboratories of oil quality control in the food industry.