Impact of meteorological conditions on fatty acid composition and isotopic signatures in Slovenian extra virgin olive oil: A long-term study

The olive tree (Olea europaea L.), a key crop in Mediterranean regions, is increasingly affected by climate variability. Meteorological factors such as temperature, rainfall, and humidity can influence the biosynthesis of fatty acids (FAs) in olives, potentially altering their concentrations and affecting the oil's compliance with established quality standards. In this study, we analyzed the FA composition of authentic Slovenian extra virgin olive oils (EVOOs) from 1993 to 2019. We also measured the δ 13C, δ 18O and δ 2H of bulk oil and the δ 13C of individual FAs for selected harvest years (2006–2008, 2019) to explore their relationships with changing meteorological conditions. The study was further extended to EVOO samples from other Mediterranean countries (Croatia, Italy, Spain, and Montenegro) to investigate the influence of regional meteorological parameters on the stable isotope composition of EVOOs. Our findings indicate that temperature significantly affects the FA composition of Slovenian EVOOs, with higher temperatures associated with lower oleic acid and higher linoleic and palmitoleic acid contents. Linear regression analysis indicated that δ 18O values of Slovenian samples primarily respond to the frequency of hot days and relative humidity, while δ 2H values demonstrate a strong relationship with temperature. Spanish samples, characterized by the highest average annual temperatures and the lowest rainfall, show significantly higher δ13C, δ2H, and δ18O values. This study provides insights into how climatic variability affects EVOO quality and supports efforts to ensure authenticity and traceability.