Monoglucoside versus Diglucoside Anthocyanin Evolution of Red Wine Produced Using a Fungus-Resistant Grape Cultivar (Downy Mildew and Powdery Mildew) under Oxidative Conditions

The need to reduce the use of pesticides in viticulture is increasing the interest in wines produced using fungal-resistant grapevine varieties, which are characterized by relevant contents of both monoglucoside and diglucoside anthocyanins. Aging in wooden barrels induces oxygen permeation into wine, but little is known about diglucoside anthocyanin evolution. Cabernet cortis wine was subjected to addition of oxygen and oak chips, and the anthocyanin changes were followed for 1 month. Decreases of 90% total monoglucosides, 80% acylated monoglucosides, 65% diglucosides, and 90% acylated diglucosides were observed. Monoglucosides formed pyranoanthocyanins, and the lower steric hindrance favored their polymerization with flavanols. Instead, the decrease in diglucosides was correlated to the number of hydroxyl groups of ring B, indicating the predominant oxidation of aglycones. However, three flavonol-anthocyanin-diglucoside derivatives named (epi)catechin-ethyl-Mv-dihexoside, (epi)catechin-ethyl-Pn-dihexoside, and (epi)catechin-Mv-dihexoside A-type were identified in wine for the first time. These research findings are useful for tuning suitable oenological practices to stabilize the color of these wines (type of barrel, aging times, oxygenation practices) and lower the malvin content, which currently is recommended by the OIV at a maximum of 15 mg/L and is a critical issue for their commercialization.