Unveiling geological identities: use of 87Sr/86Sr in food and beverages traceability, focusing on wines from Solopaca (Campania, Italy)

Research on food and beverages traceability, i.e., assessing their environmental origin, has advanced significantly in recent years thanks in large part to strontium isotope geochemistry. The unique Sr isotope signature (⁸⁷Sr/⁸⁶Sr) found in soils, plants, and waters makes the relation between food/beverages and environment achievable. This signature is derived from the local geological substratum and is influenced by age and initial concentration of rubidium in the rocks, and to geological processes. The release of strontium ions from the bedrock due to weathering processes, resulting from the interaction of circulating fluids with rocks, contributes to the accumulation of Sr in waters and soils. Part of this Sr is bioavailable and its ⁸⁷Sr/⁸⁶Sr ratio can be used as a valid tracer to identify the region of origin of wines. Considering an original ⁸⁷Sr/⁸⁶Sr ratio in rocks and soil of a given locality, it is demonstrated that strontium is first absorbed by plant roots, then by grapes, and finally by wine, without isotopic fractionation. As a result, the analysis of the wine' Sr isotope ratio establishes a precise connection between the product and its geological provenance, giving each wine a unique geofingerprint. This study aims to verify the strong relationship between the product (wine) and its region by building on these foundations. The final objective is to make the wine recognizable and distinguishable from comparable products so that it can be protected from fraud and adulteration. Using the ⁸⁷Sr/⁸⁶Sr systematics, coupled with traditional analyses such as thermal, XRD and FTIR analyses, 24 samples (8 soil samples, 8 grape samples and 8 microvinification samples) from Solopaca (Campania, Italy) were investigated. In order to provide a thorough Sr-isotopic characterization, soil samples were analyzed for both total and bioavailable Sr fractions. This method improves the investigation of environmental processes at every stage of the wine-making process.