Mineral oil hydrocarbons (MOH) are complex mixtures derived from crude oil. From the analytical point of view, MOH can be separated in mineral oil saturated hydrocarbons (MOSH), and mineral oil aromatic hydrocarbons (MOAH). MOSH consist of linear and branched alkanes and alkyl-substituted cyclo-alkanes, whereas MOAH comprise alkyl-substituted polyaromatic hydrocarbons. MOH occur in food both as a result of contamination and from various intentional uses in food production having as a consequence consumer’s exposure to a range of compounds whose effect in human health is only indirectly documented and which lacks robust risk assessment. MOH are present at specific concentrations in all kind of food, including vegetable oils. The aim of this research was contributing to the monitoring for the food groups making a relevant contribution to the background exposure of MOSH and MOAH. Among those food groups vegetable oil is included in the list that EFSA, in its recommendation, published as ‘classes of food to be included in future monitoring’ (EFSA Journal 2012, 10, 2704).
In this work, using the state-of-the-art on-line HPLC-GC-FID method similar, although updated, to that described by Biedermann (J. Chromatog. A 2012, 1255, 56), we have gathered information on the presence of MOH in a wide number of: extra virgin (104 samples), virgin (14 samples) and lampante (44 samples) olive oils, and olive pomace oil (50 samples), all of them directly provided by the corresponding producers, a fat matrix of the upmost importance for the Mediterranean Diet. We have determined not only their MOSH and MOAH concentrations but also through GCxGC-TOF/MS we have identified the main groups of compound present in both fractions.
As it was expected, our measurements gave chromatographic signals on the C10-C50 range, which is actually the range interesting from the physiological point of view, since hydrocarbons below C10 are not relevant for food contamination due to their high volatility, and those above C50 are scarcely absorbed after digestion. Actually, the C-atom number of MOSH to which humans are exposed via food goes from C12 to C40, centring at C18-C34. Our results confirm this tendency and show a wide range of analyte concentration depending of the origin, extraction process, and quality of the raw material.
We concluded that in all samples both MOSH and MOAH concentrate in the C25-C35 range followed by the C36-C40 range. Besides, the identification of some MOAH subclasses demonstrated that in olive pomace oils only 2-ring MOAH are present, being free of the mutagenic 3-7 aromatic ring species.