Detection of pressed hazelnut oil in admixtures with virgin olive oil by analysis of polar components

Analysis of the polar fraction from virgin olive oil and pressed hazelnut o il by high-performance liquid chromatography showed marked differences in t he chromatograms of the polar components in the two oils. Six commercial sa mples of pressed hazelnut oil and 12 samples of virgin olive oil (or blende d olive oil including Virgin olive oil) were analyzed. The phenolic content of the pressed hazelnut oil samples was 161 +/-6 mg.kg(-1) Inspection of t he chromatograms showed that the pressed hazelnut oil extracts contained a component that eluted in a region of the chromatogram that was clear in the olive oil samples, and consequently this component could be used to detect adulteration of virgin olive oil by pressed hazelnut oil. The component ha d a relative retention time of 0.9 relative to 4-hydroxybenzoic acid added to the oil as an internal standard. The ultraviolet spectrum of the compone nt showed a maximum at 293.8 nm, but the component could not be identified. Analysis of blends of oils showed that adulteration of virgin olive oil by commercial pressed hazelnut oil could be detected at a level of about 2.5% .