Antioxidant activity, sterol and fatty acid compositions of Turkish olive oils as an indicator of variety and ripening degree.

This study was carried out to determine the effect of three ripening stages (green, spotted and ripe) on fatty acid, sterol composition and antioxidant activity of olive oils from three olive varieties (Sarı Hasebi, Gemlik and Halhalı) widely grown in the eastern Mediterranean region of Turkey. The variety had a significant effect on the fatty acids, sterols and total phenolic content. Halhalı oil had the lowest oleic acid content (67.28%), while Sarı Hasebi oil had the highest (75.61%). Total phenolic content varied between 163.02 mg GAE/kg oil and 749.28 mg GAE/kg oil. Halhalı oil showed the highest antioxidant activity (IC50  = 66 µg/ml) whereas Sarı Hasebi oil showed the lowest one (IC50  = 2617 µg/ml). The total content of sterols in olive oils ranged from 358 mg/kg in Sarı Hasebi to 1092.33 mg/kg in Halhalı. The β-sitosterol content of olive oils varied between 80.72 (Sarı Hasebi) and 87.81% (Halhalı). ∆-5-avenasterol content ranged between 3.34 (Halhalı) and 7.30% (Gemlik). Variety and ripening degree significantly affected the β-sitosterol, ∆-5-avenasterol and erythrodiol + uvaol contents of oils. Finally, these results showed that sterol and fatty acid compositions can be used as indicators of variety and ripening degree among virgin olive oils.