Olive oil shelf life in relation to extraction system and composition of phenolic compounds
1995
Kotsifaki, F.
The present study was carried out to examine the effect of two different extraction plants on the composition and concentration of phenolic compounds and to correlate the constituents of this complex phenolic fraction with the oxidation stability of olive oil. To be sure that the only factor affecting the oxidation stability of the oil is the extraction method applied, olives bof koroneiki cultivar from the same field were harvested at one harvesting period (17/1/1994). Half of them were extracted in a classical press system and the rest in a continuous centrifugation system. Both oils were extracted commercially. Qualitative parameters of the oil samples were measured. Also, the polyphenol content of both oil samples was determined colorimetrically with a UV-vis spectrophotometer at 725 nm and chromatographically with RP HPLC coupled with a Diode-Array detector. An approach to the identity of this complex olive oil polar fraction and semi quantitative evaluation of its peaks was achieved by RP HPLC. Two main fractions appeared in the chromatogram profiles of both oil samples. Hydroxytyrosol, tyrosol, vanillic acid, syringic acid, p-coumaric acid, and o-coumaric acid were tentatively identified in the fraction 1. The second fraction, fraction 2, was found to contain many non identified peaks. Quantification of fractions 1 and 2 with RP-HPLC using tyrosol as an external standard showed that reductions in the concentrations of the two fractions during storage were more pronounced in fraction 2 than in fraction 1. This indicates a possible important role of this fraction in the oxidation stability of virgin olive oil
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