RESUMO
The oxidative stability of extra virgin olive oils (EVOO) from the Greek island of Crete was evaluated by electron paramagnetic resonance (EPR) spectroscopy and the spin trapping technique. The spin trap N-t-butyl-alpha-phenylnitrone (PBN) was added to the olive oil samples and the production of free radicals was monitored during heating at 70 degrees C. Induction time for the accelerated oxidation of virgin olive oils at 70 degrees C was determined. The EPR results were compared with the oxidative stability values provided by the Rancimat method at 110 degrees C and high linear correlations were found (r=0.922). EPR spin trapping provides a sensitive and rapid method for evaluating the oxidative stability of EVOO. The same samples of Greek extra virgin olive oils were also examined for their radical scavenging activity (RSA) toward the stable galvinoxyl radical by EPR spectroscopy. The decrease of the intensity of the EPR signal upon incubation time was followed. Both oxidative stability and radical scavenging activity of EVOO samples were correlated to their content in polyphenols and tocopherols.
