Changes in organic acid composition during fermentation and aging of Noble muscadine wine

The nature and concentration of organic acids during muscadine (Vitis rotundifolia Michx.) grape fermentation and wine aging were determined. Acids identified were tartaric acid, succinic acid, malic acid, lactic acid, and citric acid. Unlike non-muscadine wines, in which tartaric and malic acids normally account for over 90% of the total organic acid content, tartaric and succinic acids were the predominant acids of the muscadine wine studied. The concentration of succinic acid was almost negligible at the onset of fermentation, but increased to 15 mM at the end of this period. This level was maintained throughout the aging period. Malic acid decreased rapidly over 5 weeks while the loss of tartaric acid was gradual. Initial molar ratios of tartaric acid to malic, succinic, lactic, and citric acids were 1:0.39, 1:0.07, 1:0.00, and 1:0.01, respectively. After 7 months, the ratios had changed to 1:0.23, 1:0.77, 1:0.21, and 1:0.21, respectively. Formation of succinic acid appears to be responsible for the characteristic increase in total acidity during vinification of muscadine wines.