After the destemmer the wine is pumped into tanks to begin fermentation. The process of fermentation in winemaking turns grape juice into an alcoholic beverage.
White wines are typically fermented without their skins and other solids, while red wines are fermented in contact with skins and other solids.
By putting grape juice into a container at the right temperature, adding yeast which turns the sugar in the juice into alcohol and carbon dioxide the grape juice will ferment.
During fermentation, yeasts transform sugars present in the juice into ethanol and carbon dioxide (as a by-product). The temperature and speed of fermentation are important considerations as well as the levels of oxygen present in the must at the start of the fermentation. The more sugars in the grapes the higher the potential alcohol level of the wine if the yeast is allowed to carry out fermentation to dryness. We will stop fermentation in some cases early in order to leave some residual sugars and sweetness in the wine for example our Riesling. This can be achieved by dropping fermentation temperatures to the point where the yeast are inactive and then sterile filtering the wine to remove the yeast.
Fermentation may be done in stainless steel tanks, in an open plastic vat or inside a wine barrel. All of our fermentation tanks are heated or cooled by a controlled glycol system that runs through jacketed tanks. Red wine fermentation requires temperatures to reach 78.8 - 86°F for the pigments to be extracted from the grape skins. It is common to warm the fermenting juice artificially to help this happen. This has to be done carefully, as yeast die quickly in the heat. White wine fermentation may require the fermenting juice to be cooled to 53.6 - 59°F to help preserve the delicate varietal characteristics. These flavor and aromatic compounds are destroyed in high temperatures.