Determination of sterols by capillary column gas chromatography. Differentiation among different types of olive oil: Virgin, refined, and solvent-extracted

Compositional analysis of the sterol fraction of olive oil can be used to assess the degree of purity of the oil and the absence of admixture with other plant oils. This determination also permits characterization of the type of olive oil in question: virgin, refined, or solvent-extracted. In the present work, 130 samples of olive oil were analyzed, the sterol fractions were separated from the unsaponifiable fraction by silica gel plate chromatography, and later they were analyzed as the trimethyl silyl ether derivatives by capillary column gas chromatography. From the results obtained, it was concluded that this methodology is able to differentiate among virgin, refined, and solvent-extracted olive oils. Stigmasterol, clerosterol, Delta 5-avenasterol, Delta 7-stigmasterol, and Delta 7-avenasterol permit the differentiation of the three types of oil from one another. Campesterol, Delta 5,23-stigmastadienol, beta-sitosterol, and Delta 5,24-stigmasladienol permit the differentiation of only two oils from each other but confirm the conclusions obtained for other sterols. Correlations between the different sterols of virgin, refined, and solvent-extracted olive oil also have been obtained.