Decoding aroma defects: impact of climatic zoning and maturity on Garnacha Tinta grapes and wines across the Pyrenean foothills through a large-scale study

Abstract

Climate change is increasingly disrupting viticulture by decoupling technological and phenolic maturity, thereby threatening grape aromatic quality. The CLIMAROMA project, initiated in March 2024, investigates the impact of climate and ripening on the aromatic and phenolic composition of Grenache grapes and wines, and aims to develop adaptive strategies. The study spanned two vintages (2024–2025) and includes 28 vineyards (20 in Spain, 8 in France), grouped into three climatically homogeneous zones (A, B, C) using bioclimatic indices and k-means clustering. Grapes were sampled at three ripening stages: P1 (≈21 °Brix), P2 (+10–14 days), and P3 (+10–14 days after P2). Analytical approaches included classical oenological parameters, phenolic profiling (Cromoenos®), volatile compound quantification (SIFT-MS), and aromatic potential assessment via hydrolyzed mistelles. Micro-vinifications at P1 and P2 enabled detailed gas chromatography-based aroma profiling and sensory evaluation. Preliminary 2024 results reveal that sugar concentration is significantly higher at P3 in zone A compared to zone C. At P1 and P2, sugar concentrations were comparable across climatic zones, enabling a valid comparison of aromatic maturity at equivalent technological maturity. Principal Component Analysis (PCA) of hydrolyzed mistelles revealed a progressive increase in the concentration of aroma precursors from early to later ripening stages within P1. However, at P2, the PCA clearly differentiated samples based on their climatic origin, indicating that climate exerts a stronger influence on aromatic potential at more advanced ripening stages. The concentration of extractable anthocyanins (CEA) increased significantly with ripening across all zones. Notably, zone B exhibited the highest CEA values at lower sugar concentrations, suggesting an earlier and more efficient phenolic development. This was further supported by a lower phenolic maturity index in zone B, particularly at P2 and P3, indicating optimal phenolic maturity was achieved earlier compared to other zones. Wine analysis shows distinct aromatic profiles at P1 across all zones. From P1 to P2, wines from zones A and B undergo more pronounced compositional shifts than those from zone C, with A and B converging in aromatic profile at P2, while C remains distinct. Fruity and floral aromas dominate in zone A at P1, whereas woody and spicy notes characterize zone C. In total, 25 aromatic compounds were identified in grapes and 30 in wines, confirming the influence of climate and ripening on aromatic expression. These findings support the identification of viticultural zones better suited to future climatic conditions and inform targeted adaptation strategies for Grenache cultivation.