About Sr isotopes in coffee ‘Bourbon Pointu’ of the Réunion Island

Demonstration of the regional source of a high-quality product is nowadays essential to protect it from commercial transactions and cheatings. In this study, Sr isotopes are proposed as a tool to identify the regional source of a vegetable, on the basis of a combined geochemical investigation on a Coffea Arabica var. Laurina cultivation plot located on th Réunion Island. The Sr isotopic composition (⁸⁷Sr/⁸⁶Sr) of the produced coffee beans (called Pointed Bourbon) and of their growing environment, including soils, parent rocks, waters and fertilizers are determined. Flux of Sr in coffee beans is mainly dominated by soil solutions that can be influenced by Sr-rich fertilizers. This influence is however low enough to detect the cultivation soils’ Sr isotopic ratio in the vegetable product, even after roasting. It also allows discrimination of coffees produced on varied geological areas. Measurements performed on the same variety of coffee beans produced in New Caledonia strengthen the demonstration.