No abstract

Nowadays, a significant increase in intensively and irrigated managed olive orchards has occurred in Tunisia in the hope to increase the olive production. Aromatic profile with sensory analysis were considered in virgin olive oils from Arbequina, Coratina and Koroneiki cultivars grown intensively under three irrigation treatments (T1, T2 and T3 equivalent to 50%, 75% and 100% ETc.). Results showed that the aromatic quality depends first on the irrigation level applied and second on the cultivar. From sensory analysis, hay-like and greasy were the principal off-flavour detected. As the amount of supplied water increased, volatiles showed different behaviours depending on cultivar and the most important changes occurred in the release of the three alcohols ((E)-2-penten-1-ol, 1-hexanol, (E)-2-hexen-1-ol and phenylethyl alcohol) and hexanal. The most effective by irrigation regimes in separating cultivars were (E)-2-hexenal, (Z)-2-penten-1-ol, (E)-2-hexen-1-ol, fruity, bitter and pungent sensory descriptors. In conclusion, the data obtained herein proved the heavy influence of the cultivar in comparison with irrigation regimes.

The impact of different irrigation regimes based on two ripeness index, on the quantity and quality of virgin olive oil from the introduced olive cultivar Olea europaea L. Koroneiki grown at a high-density olive orchard in northern Tunisia, was assessed. Olive trees were subjected to three treatments (T1, T2 and T3) that received a seasonal water amount equivalent to 50%, 75% and 100% of the estimated local evaporative demand by a drip irrigation system and olives were collected in two different ripeness index. The olive oil content decreased when the water applied was increased but rose during ripening. The quality indexes and fatty acid composition were less affected by the irrigation schedule but most significantly by the maturity of olives. Moreover, phenol contents increased according to fruit ripening whereas no clear cut differences or consistent effects were observed by irrigation. a-tocopherol decreased slightly in the oils as ripening progressed while insignificant differences between the irrigation treatments studied were obtained. Consequently, a restitution of 75% of crop evapotranspiration (ET c. ) was sufficient to achieve good minor compounds; however, higher water volumes (100% ET c. ) gave little additional a-tocopherol and phenols increases.