87Sr / 86Sr isotopic characterization as a tool for the designation of origin and geographical indication: Application to volcanic rocks, soils, grapes and wines from Brazil and Italy

Science advances, an increased interest by consumers in the origin of the products they are buying, as well as the multifunctionality of research groups have increased the recent number of publications focusing on the use of strontium isotope ratios (87Sr/86Sr) as a geographic tracer of agri-food products. Determining the geographical origin of wines using Sr isotope composition has been made within the last three decades in many countries, including Italy, South Africa, Romania, Canada, Portugal, Argentina, France, Chile, China, Kosovo, U.S.A., and Australia. The method is based on the principle that plants absorb bioavailable elements from the soils they are growing on, inherently carrying information related to their corresponding geology settings. Due to their similar valence and ion radius, Sr behaves similarly to calcium (Ca) in many geological and biological processes, and they can thus substitute one for the other. Strontium is first absorbed by the roots of the plants, then passes to the grapes and finally to the produced wine, without any isotope fractionation compared to the initial 87Sr/86Sr value in the soil and rocks. Thus, the analysis of the Sr isotope ratio in the final product (i.e., wine) directly correlates to its geological origin. The present work aims at using the 87Sr/86Sr systematics to authenticate wine origin in volcanic districts from Italy (Ponza Island, Ventotene Island, Somma-Vesuvio, Salina Island, Mount Etna, and Pantelleria Island) and Brazil (Vale dos Vinhedos). Nine soil samples, 9 grape samples, 9 leaf samples and 9 bottled wine samples from 6 different wine producers in Italy and 3 soil samples, 3 grape samples and 3 leaf samples from 3 different wine producers in Brazil have been sampled, during the 2018 harvest. Additionally, a study of a soil profile in the Somma-Vesuvio area was performed, including a detailed 87Sr/86Sr characterization of the various soil horizons as well as of parts of the grapevine (root, steam, grape, grape pulp, grape seed and grape skin). Soil characterization from Italian sites has also been used in order to better understand the complex equilibria in the soil-plant chain. The results indicate that the analyzed samples from different districts can be actually distinguished from each other based on 87Sr/86Sr values