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 they provide solid evidence of wine making, they don't necessarily provide evidence of how the wine was made and if the modern concept of pressing (i.e. extracting juice from the skins and separating it from the skins and seeds) was used. Winemaking in ancient Egypt probably used people's feet for crushing and pressing the grapes, but tomb paintings excavated at Thebes showed that the ancient Egyptians developed some innovations to their wine presses-such as the use of long bars hanging over the treading basins and straps that the workers could hold onto while treading. Hieroglyph and paintings also showed the