The methodology developed by the researchers has been recently described in the journals Food Chemistry and Food Control, and is based on the analysis of sesquiterpene hydrocarbons, organic compounds consisting of three isoprene units, which have proven to be excellent markers of the origin of olive oil.

If you want to read the articles, you can click on the following links:
Geographical authentication of virgin olive oil by GC–MS sesquiterpene hydrocarbon fingerprint: Verifying EU and single country label-declaration.
Geographical authentication of virgin olive oil by GC-MS sesquiterpene hydrocarbon fingerprint: Scaling down to the verification of PDO compliance.