Effect of irrigation on quality attributes of olive oil.

Two irrigation treatments were applied to olive trees of the major commercial Cretan variety cv. Koroneiki, (a) irrigation with 0.4 evaporation class "A" pan and (b) rain-feed only, in two successive crop years to assess the effect of irrigation on olive oil quality. Olive fruits were harvested at their semiblack maturity stage. Data obtained indicated that irrigation increased fruit weight and oil content, but the standard quality indices (free fatty acids, peroxide value, K(232), and K(270)) of the oil were not affected significantly. However, irrigation affected some aspects of olive oil composition. There were changes in the proportions of polyunsaturated fatty acids (PUFAs), triacylglycerol molecular species, sterols, and aliphatic alcohols. Furthermore, the concentrations of the dialdehydic form of elenolic acid linked to 3,4-DHPEA (3,4-DHPEA-EDA) and the isomer of oleuropeine aglycon (3,4-DHPEA-EA) were higher in oils from non-irrigated trees. Tocopherol and total volatiles were higher in the oil produced from the non-irrigated trees. Such oil was graded more pungent when compared to oils produced from fruits of irrigated trees, although both oils were graded satisfactory by consumers.