There are two types of secondary fermentation: malolactic fermentation, in which malic acid is converted into lactic acid, and second fermentation.
Secondary fermentation is a slow alcoholic fermentation that turns into alcohol the sugar that remains in wine after racking. It takes place after that the first fermentation has converted the must into wine. Two types of secondary fermentation exist: malolactic fermentation and the fermentation that, instead, takes place the bottle during the production of sparkling wine and Champagne.
