Geochemical fingerprinting of extra virgin olive oils based on radiogenic strontium isotopes

Ensuring an efficient Extra Virgin Olive Oil (EVOO) traceability is fundamental to support a sustainable produced food. To date assessing geographical origin of EVOO is a challenging issue, especially if the authenticity is evaluated based on objective parameters beyond subjectivity or paper certifications. Consequently, technical approaches are becoming increasingly complex, such as the use of radiogenic ⁸⁷Sr/⁸⁶Sr to link the soil of the origin to the EVOO. We present a novel database of geological and organic ⁸⁷Sr/⁸⁶Sr values (n = 133) from Tuscany, using newly analyzed samples and literature data, to establish the first comprehensive bioavailable Sr isotope baseline for this region. We show that the ⁸⁷Sr/⁸⁶Sr of EVOO is a powerful fingerprint if we consider the olive mill processes. To this end a two-component mixing approach based on olive fruits and tap water was used to assess the contribution of different sources of ⁸⁷Sr/⁸⁶Sr to EVOO. The isoscape of bioavailable ⁸⁷Sr/⁸⁶Sr was generated using a novel geoinformatics framework for a representative Tuscan territory with an high quality standard EVOO production. Results show that the ⁸⁷Sr/⁸⁶Sr values of Tuscany EVOOs range from 0.70854 to 0.70974. The median value, equal to 0.70911, is higher than Tunisian (0.70861) and northern Spanish (0.70837) EVOOs. The proof of concept shown in this research is highly relevant for geographic EVOO traceability as it allows a complete evaluation of the critical path in using the Sr isotope signature for provenance study.