Refermentation

Refermentation refers to the process where yeast or bacteria are added to a fermented beverage, such as wine, beer, or cider, to initiate a second fermentation. This secondary fermentation can occur in the bottle, keg, or tank. In brewing, refermentation is commonly used to achieve carbonation in bottle-conditioned beers. Yeast remaining in the beer consumes residual sugars, producing carbon dioxide that dissolves into the liquid, creating effervescence.

In winemaking, refermentation, sometimes called "prise de mousse," is used for the production of sparkling wines like Champagne. Yeast and a measured amount of sugar, known as liqueur de tirage, are added to still wine, which is then bottled. The yeast consumes the sugar, creating both alcohol and carbon dioxide. Since the bottle is sealed, the carbon dioxide cannot escape and carbonates the wine. This process can also occur unintentionally if residual sugars and active yeast are present, leading to "bottle bombs" if not managed.

In cider and other fermented fruit beverages, refermentation in the bottle can also contribute to carbonation and add complexity to the flavor profile. It can also be a way to re-yeast a cider that has stopped fermenting prematurely. The specific yeast strains used and the temperature at which refermentation occurs can significantly influence the final characteristics of the beverage, including its effervescence, flavor, and aroma. Controlling the sugar levels and yeast activity is crucial to achieving the desired outcome and avoiding over-carbonation.