Impact of Medium Toasting Variations and Grain Density of Oak Barrels on the Phenolic Profile and Antioxidant Capacity of Cabernet Sauvignon Wines

This study aimed to investigate the influence of grain density, three variations of the medium toasting process of oak barrels, along with a stainless steel tank, on phenolic profile, chemical composition, and color of two consecutive vintages of Cabernet Sauvignon wine during 12‐month aging. The results demonstrated that vessel type and properties played a significant role in the final composition of wine. Total phenolic content (TPC) increased in all barrels, reaching maximum values in Excellence barrels with medium toasting (up to 3.01 g/L in the 2020 and 3.87 g/L in the 2021 vintage). While the concentration of monomeric anthocyanins decreased significantly, the polymeric color percentage increased by up to 15%, thus increasing the stability of the wine color. The extraction of hydrolysable tannins was most pronounced in Premium barrels with higher grain density (5–7 grains/cm), with concentrations reaching 91.35 mg/L (2020) and 260.17 mg/L (2021) after 12 months of aging. Antioxidant capacity, measured by DPPH, ABTS, FRAP, and CUPRAC assays, followed the increasing trend of total phenolics. The color change (Δ E *) remained below the consumer visibility limit (< 1), despite the chemical transformations and the changes in phenolic composition. The study confirms that by selecting a specific grain density and toasting variation of an oak barrel for Cabernet Sauvignon wine aging, wood tannin extraction and wine phenolic complexity could be modulated in certain ways, offering a practical guideline for selecting barrel characteristics according to the desired wine style.