From rock to bottle: strontium isotopes (87Sr/86Sr) as indicator of provenance for the volcanic wines of altitude from São Joaquim, southern Brazil

Studies worldwide, particularly in Canada, Italy and Brazil, have demonstrated that the ⁸⁷Sr/⁸⁶Sr ratio is a reliable indicator of the geographic origin of wines. We present here the first ⁸⁷Sr/⁸⁶Sr isotope study for the Wines of Altitude of Santa Catarina geographical indication that was recently created in the state of Santa Catarina, southern Brazil. The goal of this study is to evaluate the forensic application of strontium isotope ratios as an indicator of provenance for the wines of São Joaquim, the main wine-growing region in the state of Santa Catarina, which produces wines from European grape varieties (Vitis vinifera L.) grown in soils formed by the weathering of volcanic rocks of the Serra Geral Group (Paraná Magmatic Province). The ⁸⁷Sr/⁸⁶Sr of rocks, soils (bulk and labile fractions), vines (leaves and grapes) and wines (Sauvignon Blanc and Cabernet Sauvignon) from three wineries from São Joaquim were determined. Bedrock ⁸⁷Sr/⁸⁶Sr ratios ranged from 0.705362 for the basaltic-andesitic rocks to 0.724819 for dacites, consistent with reported values for these types of rocks. We identified a strong correlation between the ⁸⁷Sr/⁸⁶Sr ratios of the grapes and leaves, but in contrast to most previous studies there was no correlation between those of the soil (both bulk and labile fractions) and wine samples. This indicates that although the Sr isotopes in grapes and leaves behaved conservatively, the Sr isotopes in the soils may have been modified by vineyard agricultural practices, such as fertilization and liming. We thus recommend that soil sampling be done at depths >60 cm to avoid external addition of strontium. As the ⁸⁷Sr/⁸⁶Sr ratios of commercial wines represent the average isotope ratio of a given vineyard, the isotope correlation between wines and the other samples may be challenging. Despite that, it was possible to distinguish the ⁸⁷Sr/⁸⁶Sr ratios of the wines from São Joaquim, state of Santa Catarina, from the wines from Bento Gonçalves, state of Rio Grande do Sul. Even though the wines from both regions are made from grapes cultivated in the same geological unit, i.e., volcanic rocks from Serra Geral Group (Paraná Magmatic Province), the wines yield different Sr signatures.