|Authors: ||P.M. Vossen, M.J. Berenguer, S.R. Grattan, J.H. Connell, V.S. Polito|
|Keywords: ||fatty acids, polyphenols, olive oil quality, sensory evaluation, super-high-density|
A comparative study was conducted to evaluate the influence of seven different levels of irrigation applied to cv.
Arbequina I-18 olive trees grown in a super-high-density orchard (1,656 trees per hectare) in the Sacramento Valley of California (USA). Water was applied differentially by drip irrigation at rates of 15, 25, 40, 57, 71, 87, and 107% ET. Oils were made using an Abencor extraction system from three different replications of each treatment and analyzed in a laboratory.
Total polyphenol levels and oxidative stability (rancimat) hours decreased as the trees received more water, especially with the three lowest irrigation treatment levels.
Overall saturated fatty acids did not significantly change, but the mono-unsaturated levels declined and poly-unsaturated levels increased.
The individual fatty acids most affected were palmitoleic, linoleic, and linolenic, which increased, and heptadecanoic, heptadecenoic, and stearic, which decreased.
Total sterol content increased by almost 25% in oils made from trees receiving more irrigation water.
Free fatty acid levels increased in treatments receiving more water, but peroxide levels were relatively unchanged.
Oil sensory properties were also evaluated by an IOOC recognized taste panel.
The intensity levels of fruitiness, bitterness, and pungency all declined in oils made from trees receiving more water.
The lowest irrigation levels produced oils that were characterized by excessive bitterness, very high pungency, and woody, herbaceous flavors.
Intermediate irrigation levels of (40% and 57%) produced oils with balance, complexity, and characteristic artichoke, grass, green apple, and some ripe fruit flavors.
Higher irrigation levels produced relatively bland oils with significantly less fruitiness and almost no bitterness or pungency.
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