Phenolic Evolution During Extended Skin Contact: Effects of Harvest Maturity on "Orange" Wine Composition and Color

Extended skin contact transforms white wines into polyphenol-rich "orange" wines, yet the optimal combination of harvest maturity and maceration time is not fully established. The evolution of physicochemical, phenolic, and chromatic properties was evaluated in Sauvignon blanc and Fetească regală wines produced with 1, 3, and 6 months of skin contact at technological and advanced phenolic maturity. Phenolic compounds were quantified by HPLC-DAD/MS, global indices by Folin-Ciocalteu (FCI) and total polyphenol index (TPI), and color by CIELAB. Skin-derived monomers were rapidly extracted, whereas seed-derived oligomers (procyanidins B2, C1) and ellagic acid required prolonged hydroalcoholic exposure. In phenolic-mature Sauvignon blanc, total phenolics reached 338.8 mg L^-1 after 6 months, with total flavonoids of 312.8 mg L^-1 and procyanidin B2 of 91.7 mg L^-1. In technologically mature Fetească regală, flavonoids declined from 266.8 mg L^-1 at 3 months to 201.7 mg L^-1 at 6 months. Three-way ANOVA identified significant main effects of cultivar, harvest maturity, and maceration duration on all evaluated phenolic responses (all p < 0.0001), together with significant interactions; cultivar × maturity for total phenolic acids was the only nonsignificant interaction (p = 0.071). In technologically mature Sauvignon blanc, titratable acidity decreased from 6.16 to 4.78 g L^-1 and pH increased from 2.98 to 3.32 between the unmacerated control and 6 months. Exploratory correlations showed inverse associations between titratable acidity and pH (r = -0.830) and between malic (MA) and L-lactic (LA) acids (r = -0.901), without implying causality. Under the conditions examined, 1-3 months of maceration generally provided substantial phenolic extraction while limiting some declines observed after 6 months, particularly in technologically mature Fetească regală.