Barrel Fermentation

Barrel fermentation is the process of letting grape juice sit in a large wooden barrel (usually oak), during which time yeast turns the sugar in the grapes into alcohol and the juice is converted into wine. In other words, it is alcoholic fermentation within an oak vat (as opposed to a steel one).

The action of barrel fermentation is especially beneficial to white wines. First, since white wines lack the tannins of reds, the wine can instead draw tannins from the wood barrels. Secondly, since the fermentation process occurs while the wine is soaking up the oak flavor, the wood flavor is weakened. This leaves the light flavors of butter, spice and oak in the wine, instead of an overwhelmingly woody taste. Finally, the wood imparts a rich, almost creamy character to the wine.

Barrel aging is completely different than barrel fermentation. In barrel aging, the already-fermented wine is stored in barrels (of wood, cement or steel) and left to age. It is an optional final step of making a wine and is beneficial for any color wine that needs more time to settle and develop before it becomes drinkable. Barrel fermentation, on the other hand, is a required middle step in the wine-making process and is common for whites.