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Antioxidant Potential of Monovarietal Virgin Olive Oils from Autochthonous Istrian Olive Varieties

Olive oil is a rich source of phenolic compounds many of which contribute to the resistance of olive oil to oxidative rancidity and act as strong antioxidants and radical scavengers. Istria (Croatia) is a region with old tradition of olive cultivation and many autochthonous varieties, still not completely investigated, have subsisted in this area. The aim of the present study was to compare antioxidant potential of Istrian autochthonous monovarietal virgin olive oils. The oils were obtained from four autochthonous varieties (Rosinjola, Buža, Istarska Bjelica and Duga) and one introduced (Leccino), each represented with three trees. All the parameters influencing the levels of antioxidants in olive oil, excluding variety, were equal. Total phenolic content was determined with the Folin-Ciocalteau reagent and the antioxidant activity of the phenolic fraction of virgin olive oils by the DPPH test. Olive oil quality parameters (free fatty acids, peroxide value and UV spectrophotometric indexes) were determined according to EEC regulations. Significant differences (P < 0, 01) between varieties were found, both for antioxidant activity and for total phenolic content. Rosinjola olive oil showed the highest total phenolic content (347, 14 &#177; ; 15, 22 mg caffeic acid/kg) and antioxidant activity (1, 976 &#177; ; 0, 1 mmol TE/kg) as well, which distinguished this variety from the others at a level of significance (P < 0, 01) in both cases. Rosinjola oil also showed the best quality characteristics which might indicate a good state of preservation of this oil, probably due to the high content of antioxidants. For investigated oils a high positive correlation between total phenolic content and antioxidant activity was found (R2 = 0, 8564, P < 0, 01). In order to compare the antioxidant potential of Istrian autochthonous olive varieties with other Mediterranean varieties, an approximate conversion of expression units was performed.

monovarietal olive oil; antioxidant activity; phenols; autochthonous variety; DPPH

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