Exploring the differences in phenolic content of white grape varieties (Vitis vinifera L.): a study on varietal and environmental influence

Varietal selection is a promising strategy in adapting viticulture to the pressures of climate change. However, there is a need to understand the dynamics behind varietal differences. In this work, we studied the colour attributes, phenolic composition, and antioxidant potential of 24 white grape varieties ( Vitis vinifera L.) over two consecutive growing seasons in the Douro Demarcated Region in Portugal. Our objective was to explore how different varieties respond to the same growth conditions. Phenolic compounds were quantified through colorimetric methods and HPLC-DAD, while antioxidant efficacy was assessed using ABTS •+ , DPPH, and FRAP assays. The data revealed notable varietal and year-to-year differences in both phenolic content and antioxidant potential. Some varieties, such as ‘Cerceal Branco’ and ‘Moscatel Galego Branco’ showed significant increases in total phenolic content and antioxidant activity under warmer and drier conditions, suggesting a robust physiological response to abiotic stress. In parallel, ‘Viosinho’ and ‘Chardonnay’ experienced reductions in phenolic content. Moreover, most varieties revealed significant increases in flavonol content, especially quercetin derivatives. Chromatic analysis revealed grapes in 2022 were darker and with a higher chromatic intensity, which correlated strongly with higher ortho-diphenol and flavonoid concentrations. Collectively, this study highlights the importance of studying genetic diversity for climate adaptation in viticulture. By studying and identifying white grape varieties that maintain or enhance quality traits in challenging climates, these insights support targeted varietal selection to maintain wine quality and resilience amid environmental challenges. • Phenolic composition shifts in white grapes under stress is varietal-dependent. • Grape varieties increased in antioxidant capacity under warmer, drier conditions. • Growth conditions influenced antioxidant potential and berry colour development. • Varietal studies are important for climate-resilient white grapevine varieties.