bottlefermentation

Bottle fermentation is a process used in beverage production, most commonly for champagne and other sparkling wines, as well as some beers and ciders. It involves allowing the secondary fermentation to occur within the individual bottle that the beverage will eventually be sold in. This contrasts with tank fermentation, where the secondary fermentation takes place in a large vessel.

The process typically begins after primary fermentation, where yeast converts sugars into alcohol and carbon dioxide. For bottle fermentation, a small amount of additional sugar and yeast, known as the "liqueur de tirage," is added to the still beverage before it is bottled. The bottles are then sealed, often with a crown cap.

Once sealed, the yeast consumes the added sugars and produces more alcohol and, crucially, carbon dioxide gas. Because the bottle is sealed, this carbon dioxide cannot escape and dissolves into the liquid, creating the characteristic fizziness or carbonation. Over time, the yeast also produces byproducts that contribute to the flavor and aroma profile of the beverage.

Following the secondary fermentation, the dead yeast cells, known as lees, remain in the bottle. For many beverages, particularly traditional method sparkling wines, these lees are then removed through a process called riddling and disgorging. Riddling involves gradually tilting the bottles to collect the lees at the neck, and disgorging involves briefly freezing the neck and then expelling the lees with the pressure from the carbonation. For some beers and ciders, the lees may be left in the bottle, contributing to a hazy appearance and complex flavors. Bottle fermentation is often considered a mark of quality for sparkling beverages.