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
Phenolic content in wine Average total polyphenol content measured by the Folin method is 216 mg/100 ml for red wine and 32 mg/100 ml for white wine. The content of phenols in rosé wine (82 mg/100 ml) is intermediate between that in red and white wines. In winemaking, the process of maceration or "skin contact" is used to increase the concentration of phenols in wine. Phenolic acids are found in the pulp or juice of the wine and can be commonly found in white wines which usually do not go through a maceration period. The process of oak aging can also introduce phenolic compounds