Phenolic composition and extractability of Chilean ‘Syrah’ grapes and wines under contrasting climatic conditions

Climate change poses significant challenges to wine-producing regions, particularly due to rising temperatures that accelerate sugar accumulation in grapes and promote the decoupling between technological maturity (related to sugar and acid content) and phenolic maturity (associated with anthocyanin accumulation and seed coat lignification). This study aimed to evaluate the phenolic composition and extractability of ‘Syrah’ grapes and wines from two Chilean valleys with contrasting climatic conditions. Agroclimatic characterization was performed using long-term and seasonal bioclimatic indices, confirming the warm conditions of the Maipo Valley and the cooler climate of the Casablanca Valley. Phenolic compounds (anthocyanins and flavanols) and their extractability were analyzed in skins, seeds, and wines from grapes harvested at the same technological maturity. Warmer conditions in the Maipo Valley reduced phenolic content in the skins but enhanced their extractability. They also favored the extraction of phenolic compounds from seeds and increased soluble polysaccharide release compared with cooler conditions. Overall, rapid sugar accumulation and the decoupling of technological and phenolic maturities negatively affected the phenolic composition of the resulting wines. These findings highlight the influence of climate conditions on phenolic development in grapes and provide insights into the potential consequences of climate change for red wine quality.