Geographical traceability of extra virgin olive oil from Valdichiana Senese (Tuscany, Italy)

Extra virgin olive oil (EVOO) is derived from the pressing of the drupes of the Olea europaea tree and is renowned for its health benefits due to the presence of several monounsaturated fats, antioxidants, and polyphenols. Indeed, EVOO is a typical food used in the Italian gastronomic tradition because the terroir of Italy allows the production of high-quality olive oil. For this reason, to ensure transparency, to prevent fraud and enhance consumer confidence, methods were developed to determine the geographical origin and authentication of EVOOs. Methods like elemental chemical analysis, compositional analysis, and isotopic analysis play central roles in determining the geographical origin. The area selected for the study is Valdichiana Senese, in Southern Tuscany, Italy, acclaimed for its EVOOs, renowned for its bitter and spicy attributes and its high-quality. This thesis is divided in four parts: The concentrations of 12 potential toxic elements (As, Cd, Co, Cr, Cu, Ni, Pb, Sb, Tl, U, V, and Zn; PTEs) were determined in soils and EVOOs collected in 2019-20 with the aim of assessing the potential risk for human health related to PTE intake from the consumption of Valdichiana Senese EVOO as well as to identify any contamination by PTEs in olive grove soils and evaluate the associated ecological risk. The data, obtained by ICP-MS analyses, were used to calculate the Health Risk Index (HRI) for EVOOs and the Potential Ecological Risk Index (PERI) for soils. The results indicated that although EVOOs from Valdichiana Senese may present somewhat slightly high concentrations of Cu and Zn, the associated health risk is negligible. The concentration of PTEs in olive grove soils was comparable to their geochemical background in soils from Southern Tuscany. A low to moderate Cu contamination emerged only in two cases, probably because of the diffuse use of Cu-based products in agriculture. Overall, the ecological risk was very low. In order to establish the geographical traceability of Valdichiana Senese EVOOs were considered physical and chemical properties of the olive grove soils and the concentration of 36 elements in the olive grove soils (total content and bioavailable fraction), in olive pulps and EVOOs collected in 2020-21. In the pursuit of relationships between soil, olive fruit and EVOO chemical composition, REEs were excluded due to their undetectability in olives and EVOOs. Pearson correlations revealed Sb as is the only element correlated between bioavailable soil fractions and olives among all farms. Instead, in soils with only marine sands and sandstones substratum, positive correlations were observed between total contents of Fe and V in soils and EVOOs and the content of U with olive pulps. Also, were found correlations of Pb and Sb in the soil bioavailable fraction and olives. Volatile organic compounds (VOC) and fatty acid (FA) profiles in EVOOs collected in 2021-22 and 2020-21 from Valdichiana Senese and Alentejo, Portugal, were compared to classify EVOOs according to their origin area. Utilising HS-SPME-GC/MS and GC-FID analysis were identified 107 compounds in Italian EVOOs, while 77 in those Portuguese, with only 43 in common. Volatiles were divided in classes (alcohols, aldehydes, alkanes, esters, and terpenoids) and 2-Hexenal is the compound most abundant in both EVOOs. For FAs, oleic, palmitic, and linoleic are the acids with the highest percentages. Discriminant analysis confirmed that volatile compounds and fatty acids are valid to distinguish EVOOs based on their year and area of production. Additionally, the study evaluated the quality of EVOOs from 2019 to 2021, focusing on free acidity, peroxide values, and total phenols content. Valdichiana Senese EVOOs showed an excellent ability to maintain unaltered characteristics. Weather conditions were observed to affect the quantity of phenols. In addition, the same parameters were used to reveal insights into stability and factors influencing quality parameters in Valdichiana Senese EVOO from the 2021-22 harvest to 12 months later. The linear regression analysis allowed to see that the peroxide values and the phenols content were highly influenced by the time, but not acidity.