Sugars in wine The technique allows for a better extraction of wine polysaccharides. 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
Phenolic content in wine into wine, most notably vanillin which adds vanilla aroma to wines. Most wine phenols are classified as secondary metabolites and were not thought to be active in the primary metabolism and function of the grapevine. However, there is evidence that in some plants flavonoids play a role as endogenous regulators of auxin transport. They are water-soluble and are usually secreted into the vacuole of the grapevine as glycosides. "Vitis vinifera" produces many phenolic compounds. There is a varietal effect on the relative composition. In red wine, up to 90% of the wine's phenolic content falls under the classification of flavonoids.