Secondary fermentation (wine)

Lore & Background

In red wine production, the maceration process was traditionally done in large vats where the fermentation process would begin, as noted by the presence of carbon dioxide bubbles. Secondary fermentation would take place when the wine is transferred to a second container such as a carboy or oak barrel. In sparkling wine production, the secondary fermentation often takes place in the wine bottle that the wine will be sold in, most commonly known as the méthode champenoise or 'Champagne method' after the region most noted for sparkling wine production. When the base wine (or cuvee) has been produced from single grape varietals or a blend, the wine is bottled with a mixture of yeast and fresh sugar known as the 'liqueur de tirage'. This secondary fermentation, also known as bottle fermentation, is the process that makes the wine 'bubbly' due to the containment of carbon dioxide which is normally released as a by product in regular fermentation. In still wine production, particularly of red wines and some white wines like Chardonnay, the secondary fermentation process can also usher in the use of malolactic fermentation (or MLF) where the hard, green apple-like malic acid is converted into softer, butter-like lactic acid. In the case of a stuck fermentation, a winemaker may wish to transfer the must to a second vessel and use stronger, more aggressive yeasts with high fermentation temperatures to re-initiate the fermentation process. A similar process known as governo has been used by Tuscan winemakers since the 14th century with the isolation after harvest of a batch of grapes that can be added later to the wine to help prevent (or recover from) a stuck fermentation.

Reader's Guide

Secondary fermentation is significant in winemaking for its role in both still and sparkling wine production. In sparkling wines, the containment of carbon dioxide during bottle fermentation creates the characteristic bubbles, while dead yeast cells known as lees must be removed in a process called disgorgement prior to corking. For still wines, secondary fermentation often involves malolactic fermentation, which softens acidity by converting malic acid to lactic acid, a technique used for red wines and some white wines like Chardonnay. The term also covers the practice of transferring fermenting must to a second vessel to restart a stuck fermentation using stronger yeasts and higher temperatures. The historical governo method from Tuscany, dating to the 14th century, similarly addresses stuck fermentation by adding reserved grapes. Overall, secondary fermentation is a flexible concept that encompasses multiple techniques for managing fermentation, adjusting flavor, and achieving desired wine styles.

Did You Know?

• In sparkling wine production, secondary fermentation often takes place in the bottle the wine will be sold in.
• The byproduct of secondary fermentation in sparkling wines is carbon dioxide, which makes the wine 'bubbly'.
• Dead yeast cells known as lees are produced during secondary fermentation and must be removed by disgorgement.