Influence of pomace residues on multi-element composition of Extra Virgin Olive Oil (EVOO)

Analysis of elements in Extra Virgin Olive Oil (EVOO) samples is challenging due to the complex matrix as well as their very low concentrations in oil. Optimization of a previously proposed analytical method consisting of ultrasonic acid extraction and subsequent ICP-MS detection is now allowing determination of 27 elements in EVOO a low pg g-1 level for trace elements. Furthermore, EVOO samples are likely to contain residual pomace, which potentially can influence the elements concentration and distribution. Indeed, our study revealed that pomace residues, when present in EVOO even at small quantity (1 g kg-1), significantly alter concentrations and relative proportions of many elements present in EVOO. Comparative analyses of EVOO samples with and without centrifugation prior to ultrasonic acid extraction confirmed significant influence of pomace residues on elements concentrations. Therefore, an adequate sample pre-treatment (removal of pomace residue) through centrifugation is essential for determining real multi-elemental composition of olive oil. This is critical in application of EVOO multi-element composition in traceability studies and determination of geographic origin of oil.