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
History of the wine press their wine. By at least the 18th dynasty, the ancient Egyptians were employing a "sack press" made of cloth that was squeezed with the aid of a giant tourniquet. The use of a wine press in winemaking is mentioned frequently in the Bible but these presses were more elaboration of treading lagars where grapes that were tread by feet with the juice running off into special basins. The more modern idea of a piece of a winemaking equipment used to extract the juice from the skins probably emerged during the Greco-Roman periods where written accounts by Cato the Elder, Marcus