Microclimate Effects on Quality and Polyphenolic Composition of Once-Neglected Autochthonous Grape Varieties in Mountain Vineyards of Asturias (Northern Spain)

In the southwestern region of Asturias (Northern Spain) lies one of the few mountainous viticulture areas in the world, representing only 5% of global viticulture. The complex topography and differences in altitude, slope, and orientation of mountainous viticulture areas create highly variable microclimates even among nearby plots, with distinct mean temperatures, relative humidity, and solar radiation. These factors strongly influence grape and wine quality, as well as polyphenol concentration. Several production parameters and basic chemical characteristics of must were analyzed over multiple years, along with polyphenol content, in grapes from the same clones of Albarín Blanco and Verdejo Negro (autochthonous genotypes of this viticultural area), grown in geographically close vineyards with different topographies and microclimates. The results revealed significant differences in all analyzed parameters. Both varieties showed polyphenol concentrations slightly higher than those reported in the scientific literature, which may be related to the typical conditions of mountain viticulture or intrinsic genetic factors of these varieties. The best grape and must quality, regardless of variety, was obtained in plots located in sunny, well-ventilated areas with steep slopes and low-fertility soils. These plots exhibited higher potential alcohol content and greater concentrations of anthocyanins, hydrocarbons, and total polyphenols. When comparing varieties, Verdejo Negro showed the highest levels of anthocyanins, flavonols, and total polyphenols, whereas Albarín Blanco exhibited the highest concentrations of total phenolics and hydrocarbons.