In this work the Rancimat technique (temperature 110 degreesC and air flow 20 I/h) was used in order to test the catalytic effect induced by Cu(II)-and Fe(III)-ions on olive oil oxidation. Different amounts of Cu(II)- and Fe(III)-cyclohexanebutyrates were added to a refined olive oil. Copper was shown to be a more active catalyst than iron. In fact, the induction time of the oil was halved by the addition of about 120 ng/g of copper versus 9000 ng/g of iron. The effect of copper and iron was also evaluated on the oil enriched with increasing quantities of caffeic acid (50, 100 and 200 mg/kg). The addition of this phenol induced a significant protective effect which delayed the oxidation of both the control and the oil samples enriched with metals. However, copper-catalyzed oxidation also in the presence of the antioxidant, thus decreasing the oil oxidative stability approximately three times compared to the control.
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