Secondary fermentation (wine)

An example of this would be starting fermentation in a carboy or stainless steel tank and then moving it over to oak barrels.

This is 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".

In still wine production, particularly of red wines[2] 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.

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.

In red wine production, the maceration process was traditionally done in large vats where the fermentation process would begin (in the picture this is 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.
With sparkling wines , the by product of secondary fermentation is the containment of the carbon dioxide bubbles which makes the wine "sparkling" as well as dead yeast cells known as lees (visible in the picture) that must be removed in a process known as disgorgement that happens prior to corking.