THE EFFECT OF DIFFERENT IRRIGATION LEVELS ON THE QUALITY OF OLIVE OIL IN THE WESTERN COASTAL REGION IN TURKEY

Abstract

The effect of different irrigation levels on olive (Olea europaea ‘Memecik’) oil quality parameters was studied in the Aegean region during the 2007/08 and 2008/09 crop seasons. Six different drip irrigation water levels were tested using Class A pan evaporation technique (I0 (kpc:0), I0.25 (kpc:0.25), I0.50 (kpc:0.50), I0.75 (kpc:0.75), I1.00 (kpc:1.00), I1.25 (kpc:1.25). Fruit characteristics such as ripening index, percent oil extraction and quality indices, K232 and K270 values, bitterness index and fatty acid composition were analyzed. Most of the parameters varied significantly with irrigation water level. The ripening index of olives responded linearly to the amount of water. I0.25 olives had the highest oil content (24.4%). The free acidity of the oils varied between 0.21 and 0.60% and responded negatively to irrigation level and the peroxide value of the oils ranged from 1.29 to 1.64 meq O2/kg oil with no effect of irrigation treatment. The I1.25 application had a low maturation index, which corresponded to the lowest chlorophyll value. The bitterness index and polyphenol content of the oils varied from 0.71 to 1.71 and 179.83 to 281.83 mg/kg, respectively, and both responded negatively to increasing water dosage. While there were significant differences with amount of irrigation water in palmitic, palmitoleic, stearic and oleic acids, and MUFAs, PUFAs, MUFA/PUFA, there were no significant differences in linolenic and arachidic acids, or in SFAs or the PUFA/SFA ratio.