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The main goal of this study was to investigate the effects of moderate saline water irrigation in the “Chemlali” olive cultivar grown in Sfax, an arid region of Tunisia, on the composition and quality of the resultant virgin olive oil in comparison to a control plot grown under rain‐fed conditions. Free acidity, peroxide value, specific ultraviolet absorbance (K232, K270), fatty acid composition, induction time, total polyphenol and total chlorophyll contents were determined and reported. The irrigation did not affect free acidity and peroxide value. Whereas, specific ultraviolet absorbance (K232, K270), fatty acid composition, induction time, total polyphenol and total chlorophyll contents were affected by irrigation. Rain‐fed virgin olive oils showed a statistically significant higher content of oleic and linoleic acids. Virgin olive oils extracted from moderate saline water irrigated trees had higher contents of palmitic, palmitoleic, stearic and linolenic acids and a longer shelf‐life. A positive correlation was noted between polyphenol content and oxidative stability. PRACTICAL APPLICATIONS Olive trees are quite widespread in the south of Tunisia. They grow in semi‐arid environments. It is a species with high resistance to drought. However, irrigation allows productivity to increase in olive growing areas where rainfall is scarce. Irrigation is a determinant parameter for olive oil quality. In fact, high olive oil quality can not be obtained from olive fruit suffering from a high degree of water stress. The main purposes of this paper are to investigate the effects of moderate saline water on the commercial quality, the fatty acid composition, and the induction time, total polyphenol and total chlorophyll contents of “Chemlali” virgin olive oil in Tunisia.

The aim of this work was to study the effect of the irrigation with treated wastewater (TWW) on the quality parameters of "Chemlali" olive oil through two crop seasons (2004/2005 and 2006/2007). The results showed that irrigation with TWW did not affect the examined oil quality indices (free acidity, specific ultraviolet absorbance K 232 and K 270 ). During the two crop seasons, the mean values of these parameters are lower than the upper limits established for the best commercial olive oil quality designated as "Extra Virgin." However, a significant increase of palmitic, palmitoleic, linoleic, linolenic and stearic acid contents was found in the 2006/2007 crop season in the plot irrigated with TWW as compared to the one treated with well water. In addition, a decrease of oleic acid and polyphenol content was observed at the end of experimental period. PRACTICAL APPLICATIONSThe availability of fresh water is very scarce in the Middle East and North Africa. Yet consequently, good quality water is used to irrigate crops more sensitive to water shortage than olive trees. Brackish water or recycled wastewater can be used for irrigation, minimizing the exploitation of natural water 4 Corresponding author. S. Bedbabis, Olive Tree Institute,