Phenolic compounds, tocopherols and other minor components in virgin olive oils of some Tunisian varieties

The phenols, alpha-tocopherols, fatty acids and oxidative stability of six monovarietal virgin olive oils (VOOs) were determined. Fourteen phenolic compounds were detected and quantified by solid phase extraction and reversed phase-high performance liquid chromatography. Dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol, oleuropein and ligstroside aglycones were the main components in all samples. Pinoresinol was the most abundant component in lignan fraction. The total phenol content of these monovarietal oils varied from 66.82 mg/kg in Neb Jmel oil to 662.74 mg/kg in El Hor oil. A wide range of alpha-tocopherol contents was also noticed; it varied from 141.94 mg/kg in Semni variety to 364.23 mg/kg in Jdallou variety. With regard to pigments, chlorophylls and carotenoids were found at variable concentrations: with median values of 11.33 and 3.10 mg/kg, respectively. Among the studied varieties, Oueslati and El Hor were characterized by the lowest levels of palmitic and linoleic acids and the highest values of oleic acid.