Detection of olive oils authenticity by determination of their sterol content using LC/GC

Abstract

The content of selected sterols as declared in the EU Commission Regulation was used to prove the authenticity of olive oils. A modified method using the preparative LC with silica gel packed column and gradient elution with three mixtures of hexane and diethyl ether was used to separate undesirable interfering compounds in the unsaponifiable fraction before the determination of sterols using GC. Model experiments based on the determination of D-7-stigmastenol and campesterol (addition of sunflower and soybean oils), or brassicasterol (addition of rapeseed oil) were used to verify that this method is capable of identifying adulteration of olive oils by additions of sunflower, soybean or rapeseed oils. An elevated content of these marker sterols, in comparison with their permitted contents, enables the identification of an addition of 5–10% of the above oils to the olive oil. This method was also used to evaluate the authenticity of five samples of olive oils from the SIAL exhibition (Paris) and ten samples of virgin olive oils obtained on thePrague markets. It was revealed that none of the samples showed the signs of adulteration.