Fermentation

Fermentation is the process through which grape juice transforms into wine.

Once the crushed grapes are put in a vat, yeast is added to metabolize the glucose and fructose (sugars) within the grape juice into ethanol (alcohol) and carbon dioxide. Since the sugars in the grape juice convert into alcohol over time, the length of the fermentation process determines whether the wine will taste sweet or alcoholic.

The fermentation stage determines the color of the wine. When the grape juice is fermented with the grape skins and seeds, the resulting wine will have a garnet hue (as well as tannins). The longer the juice is fermented with the skins, the darker the red color will be. Fermenting grape juice without the skins and seeds produces the fairly clear liquid of a white wine.

Additionally, different types of vats can be used during fermentation to instill different flavors in white wines. Using a barrel will create a bigger, more complex wine with tannins and hints of oak; using steel or cement containers allow the natural sugars and fruit from the grapes to prevail. For example, a chardonnay fermented in oak will taste completely different than one fermented in stainless steel; the former will be heavy and creamy with a buttery finish; the latter will be light, crisp and fruity.