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 Terentius Varro, Pliny the Elder and others described wooden wine presses that utilized large beams, capstans and windlasses to exert pressure on the pomace. The wines produced by these presses were usually darker, with more color extracted from the skins but could also be more harsh with bitter tannins also extracted. That style of wine press would eventually evolve into the basket press used in the Middle Ages by wine estates of the nobility and Catholic Church leading to the modern tank batch and continuous presses used in wineries today. The exact origins of winemaking (and, thus, of pressing grapes)