Abstract

Ouni Youssef, Flamini Guido, Douja Daoud and Zarrouk Mokhtar

This paper evaluates the usefulness of three chemical parameters (composition of volatiles compounds, total phenols and fatty acids) as a tool to discriminate the olive oils obtained from three varieties (Oueslati, Chemlali and Chetoui). These varieties are included among the cultivars permitted by the disciplinary for the production of the ‘‘Kairouan olive oil’’, a Tunisian protected designation of origin (PDO) product. The olives were collected during the year crop 2009/2010 from the same orchard (calcareous soil), in order to eliminate geographical and climatic influences. Analysis of the effect of cultivar on the different analytical values, revealed statistically significant differences in some parameters, mainly in free fatty acid and phenol contents and oxidative stability. Furthermore, most of the quality indices and fatty acid composition showed significant variations among olive varieties. Oueslati variety had the highest values of oleic acid, whereas Chetoui was noteworthy for its high content of phenolic compounds. The major volatile component was the C6 aldehyde fraction whose content varied greatly between the different varieties: the (E)-2-hexenal content ranged from 20.9% in the oil obtained from the Oueslati variety to 7.7% in the case of Chemlali one; the amount of hexanal ranged from 10.2% in Oueslati to 3.7% in Chetoui. These results suggest that the genetic factor (cultivar) influences the volatiles formation.