Definition: Refermentation

A restart of alcoholic fermentation due to residual sugar or malolactic fermentation in the presence of lactic bacteria in poorly stabilised wine. An accident that can sometimes affect sweet white wines in particular. The significant amount of residual sugar they contain can start to ferment again, with unfortunate consequences: cloudy, acidic and sparkling wine, and corks that leak or pop out. The only stabiliser authorised is sulphur dioxide. It must be used in relatively large quantities, as it combines in part with the sugar in the wine and only its free form is antiseptic. Fortunately, modern analyses make it possible to determine the necessary quantities with extreme precision, thus avoiding the abuses of the past that caused headaches and were partly responsible for the general public's disaffection with sweet and mellow white wines.