Olfactory fingerprint of extra virgin olive oils: Fast analysis by Flash Gas Chromatography (FGC) Electronic Nose and coupling with sensory data

The control of authenticity of extra virgin olive oil (EVOO), one of the most frauded food in the world, is based on many determinations of chemical and compositional parameters and, by the law, also on sensory analysis. It is well known that the sensory descriptors of an EVOO, both positives and negatives, are due to the presence of many specific volatile compounds, perceived by olfactory receptors. In particular, the compounds responsible for the recognized defects (winey, fusty, muddy, musty, rancid), and their biosynthetic or chemical origin are widely investigated in literature. On the other hand, also the presence of positive olfactory notes resembling herbs/fruits/vegetables can be linked to the olive varieties/quality and/or geographical origin, being the lipoxygenase enzymatic pathway influenced by both genetic and environmental factors. At now, the volatiles profile and/or the presence of specific volatile markers are not indicated as legal requirements to verify the authenticity of an EVOO, in terms of assessment to the quality category or belonging to specific quality standards (for example monovarietal or protected designation of origin/PDO). In this work, a large set of samples sold in Italian markets as EVOOs, but different for geographical origin and price, were analysed by a FGC Electronic Nose to develop a fast gas chromatographic separation of volatile molecules by two short metal capillary columns of different polarities, mounted in parallel and connected to separate flame ionization detectors. The two chromatograms are elaborated to give a global olfactory fingerprint of the EVOO samples subsequently combined with sensory data of EVOOs obtained by COI Panel test method, using an EC Reg. 640/2008 profile sheet, with the addition of descriptive peculiar olfactory notes to be evaluated by the assessors. Moreover, to confirm the identity of selected volatile molecules in the headspace of EVOOs, a solid phase micro-extraction (SPME) coupled to gas chromatographic separation and mass detection (GC-MSD) was used.