Pressing (wine) red wine production the timing of when to press is one of the most important decisions in the wine making process since that will be the moment that maceration and phenolic extraction ceases. Some winemakers use the decreasing sugar level (such as brix measurement) scale and press once the wine has reached complete dryness. Often winemakers will use taste to determine if the wine has extracted enough tannins to produce a balanced wine and may press before complete dryness (such as at 3-8 brix). Though removing the skins by pressing often removes some solids that the wine yeast need to
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.