Acids in wine ripened grapes. While concentration varies among grape varieties, it is usually found in higher levels with red wine grapes. The acid is created as a byproduct of the metabolization of nitrogen by yeast cells during fermentation. The combination of succinic acid with one molecule of ethanol will create the ester mono-ethyl succinate responsible for a mild, fruit aroma in wines. Acidity is highest in wine grapes just before the start of "veraison", which ushers in the ripening period of the annual cycle of grape vines. As the grapes ripen, their sugar levels increase and their acidity levels decrease. Through the
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