Sugars in wine Sugars in wine Sugars in wine are at the heart of what makes winemaking possible. During the process of fermentation, sugars from wine grapes are broken down and converted by yeast into alcohol (ethanol) and carbon dioxide. Grapes accumulate sugars as they grow on the grapevine through the translocation of sucrose molecules that are produced by photosynthesis from the leaves. During ripening the sucrose molecules are hydrolyzed (separated) by the enzyme invertase into glucose and fructose. By the time of harvest, between 15 and 25% of the grape will be composed of simple sugars. Both glucose and fructose are six-carbon
History of the wine press from olives. This press would entail laying the grapes out underneath several planks of wood and then weighing the planks down with rocks to press the juice out from the grapes. The wine made from these rudimentary pressing wasn't held in high esteem by the Greeks, often tainted with impurities and having a short shelf life. Much more prized was the wine produced from "free run" juice that was released by the grapes under their own weight before any treading or pressing. This wine was believed to be the most pure and was often used for medicinal purposes. In the