Phenolic content in wine - quercetin. Like other flavonoids, the concentration of flavonols in the grape berries increases as they are exposed to sunlight. Some viticulturalists will use measurement of flavonols such as quercetin as an indication of a vineyard's sun exposure and the effectiveness of canopy management techniques. Anthocyanins are phenolic compounds found throughout the plant kingdom, being frequently responsible for the blue to red colors found in flowers, fruits and leaves. In wine grapes, they develop during the stage of "veraison" when the skin of red wine grapes changes color from green to red to black. As the sugars in the grape
Acids in wine influencing the taste of the finished wine. In most plants, this organic acid is rare, but it is found in significant concentrations in grape vines. Along with malic acid, and to a lesser extent citric acid, tartaric is one of the fixed acids found in wine grapes. The concentration varies depending on grape variety and the soil content of the vineyard. Some varieties, such as Palomino, are naturally disposed to having high levels of tartaric acids, while Malbec and Pinot noir generally have lower levels. During flowering, high levels of tartaric acid are concentrated in the grape flowers and then