Antioxidant capacity of extra-virgin olive oils

In this study, the oxygen radical absorbance capacity (ORAC) of vegetable o ils was investigated using a spectrofluorometric method, which measures the protection of the phenolic substances of the oil on the P-phycoerythrin fl uorescence decay in comparison with Trolox. More than 97% of the phenolic s ubstances was extracted from the ail using methanal, and the methanolic ext ract was then used for the ORAC and the total phenolics assay. We found a s ignificant correlation between ORAC values of different olive oils and the total amount of phenolics. For extra-virgin olive oils, maximal ORAC values reached 6.20 +/- 0.31 mu mol Trolox equivalent/g, while refined and seed o ils showed values in the 1-1.5 mu mol Trolox equivalent/g range. Our method is useful to assess the quality of olive oils and to predict, in combinati on with the rancidity tests, their stability against oxidation.