Application of the FTIR technique as a non‐invasive tool to discriminate Portuguese olive oils with protected designation of origin

Three Portuguese olive oils with PDO (‘Azeite do Alentejo Interior’, ‘Azeites da Beira Interior’ and ‘Azeite de Trás-os-Montes’) were studied considering their physicochemical quality, antioxidant capacity, oxidative stability, total phenols content, gustatory sensory sensations and Fourier transform infrared (FTIR) spectra. All oils fulfilled the legal thresholds of EVOOs and the PDO's specifications. Olive oils from ‘Azeite da Beira Interior’ and ‘Azeite de Trás-os-Montes’ showed greater total phenols contents and antioxidant capacities, while ‘Azeites da Beira Interior′ presented higher oxidative stabilities. Linear discriminant models were developed using FTIR spectra (transmittance and the 1st and 2nd derivatives), allowing the correct identification of the oils’ PDO (100 % sensitivity and specificity, repeated K-fold-CV). This study also revealed that multiple linear regression models, based on FTIR transmittance data, could predict the sweet, bitter, and pungent intensities of the PDO oils (R2≥0.979±0.016; RMSE≤0.26±0.05, repeated K-fold-CV). This demonstrates the potential of using FTIR as a non-destructive technique for authenticating oils with PDO. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020) and to the Associate Laboratory SusTEC (LA/ P/0007/2020). The authors are also grateful to the “Project OLIVE4ALL – Olive Heritage for Sustainable Development: Raising Community Awareness of Living Heritage” (ref. JPICH/ 0001/2020), financed by FCT (Portugal). Nuno Rodrigues thanks the FCT – Foundation for Science and Technology, P.I., for the National funding through the institutional program contract for scientific employment. Sandra Lamas also acknowledges the Ph.D. research grant (2022.10070.BD) provided by FCT.