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The influence of olive variety and harvest time on the bitterness and phenolic compounds of olive oil

The influence of harvest time on the intensity of bitterness and the level of phenol compounds in olive oil from the region of west Istria obtained from two local (Bianchera and Busa) and one introduced, Italian variety (Leccino) was studied. Olive fruits were harvested at three different harvesting periods, during four successive crops seasons. Immediately after harvesting, the fruits were processed under the same conditions in a pilot plant. Basic quality parameters, the content of total polyphenols, o-diphenols and the intensity of bitterness were determined in oil samples. Samples of oil obtained from the Bianchera and Busa varieties were additionaly tested for stability at elevated temperature (98 °C) and under the influence of UV-light. The results elaborated statistically showed the level of phenol compounds and the intensity of bitterness to be significantly influenced by both the harvest time and olive variety, with the influence of harvest time being more pronounced. The applied tests for accelerated deterioration of oil indicated a more rapid increase in the peroxide value in oil samples of both varieties exposed to UV light than in those exposed to elevated temperature. Both tests showed better stability of the oil obtained from the Bianchera variety.

harvesting time; olive variety; oxidative stability; polyphenols; virgin olive oil

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