Effect of three irrigation regimes on Arbequina olive oil produced under Tunisian growing conditions

This study investigated the effect of irrigation amount on the concentration of phenolic compounds in olive (Olea europaea L., cv. Arbequina) oil obtained from an intensively-managed orchard in a semi-arid area with a Mediterranean climate in Tunisia. Different irrigation treatments 50% Etc, 75% Etc and 100% Etc were applied to the olive orchard. Oil quality, evaluated using the parameters established to determine the quality level of virgin olive oils (acidity, K232, K270 and peroxide index) was slightly affected by irrigation. However, results showed that irrigation positively affected both fruit and oil quality. In fact, the least irrigation regime (T1), showed a significantly higher content of oleic acid (70.08%), whereas olive oils from more irrigated trees (T2 and T3) had higher contents of palmitic acid (11.64% and 13.14%, respectively) and lower of linoleic acid (approximately 12.7%). However, content of phenolic compounds (hydrophilic and lypophilic), in the oils extracted, strongly differed. In fact, different irrigation regimes applied not only affected the total amount of phenols which were proportional to irrigation (193.2 and 271.87 mg kg−1 for T1 and T3, respectively) except for T2 but also their HPLC profiles. Contrarily to phenols, insignificant differences were observed in the concentration of α-tocopherol between the irrigation treatments studied.