An Analytical Simplification for Faster Determination of Fatty Acid Composition and Phytosterols in Seed Oils
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.
KeywordsPhytosterols Fatty acids Seed oil Solid-phase extraction SPE
This work was funded by “Junta de Andalucía” through project P12-AGR-4622 and the Spanish Ministry of Economy, Industry and Competitiveness through project AGL2013–45110-R. The authors thank to Irene Pérez de la Rosa for her technical assistance.
Compliance with Ethical Standards
Conflict of Interest
Aída García-González declares that she has no conflict of interest. Joaquín Velasco declares that he has no conflict of interest. Leonardo Velasco declares that he has no conflict of interest. M. Victoria Ruiz-Méndez declares that she has no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
- Alberici RM, Fernandes GD, Porcari AM, Eberlin MN, Barrera-Arellano D, Fernández FM (2016) Rapid fingerprinting of sterols and related compounds in vegetable and animal oils and phytosterol enriched-margarines by transmission mode direct analysis in real time mass spectrometry. Food Chem 211:661–668. https://doi.org/10.1016/j.foodchem.2016.05.057 CrossRefGoogle Scholar
- AOCS (1997) Method Ch 6-91 in official methods and recommended practices of the American Oil Chemists’ Society. AOCS Press, ChampaignGoogle Scholar
- Codex Alimentarius (2001) Codex standard for named vegetable oils. CODEX STAN 210–1999Google Scholar
- EEC (1991) Commission regulation no. 2568/91. Determination of the composition and content of sterols by capillary-column gas chromatography. Official Journal of the European Communities. No. L 248/15–22Google Scholar
- Frankel EN (2012) Free radical oxidation. In: Frankel EN (ed) Lipid oxidation, 2nd edn. Woodhead publishing limited, Cambridge, pp 15–24Google Scholar
- ISO (1991) Method 6799. Animal and vegetable fats and oils—determination of composition of the sterol fraction—method using gas chromatography. International Organization for StandardizationGoogle Scholar
- ISO (1999) Method 12228–2. Determination of individual and total sterols contents—gas chromatographic method. International Organization for StandardizationGoogle Scholar
- IUPAC (1992) Standard methods for the analysis of oils, fats and derivatives, 7thedn. International union of pure and applied chemistry. Blackwell Scientific, OxfordGoogle Scholar
- Magnusson B, Örnemark U (2014) Eurachem guide: the fitness for purpose of analytical methods—a laboratory guide to method validation and related topics. Available: http://www.eurachem.org [Accessed June 24, 2015]