A distinction must be made between a deliberately induced second fermentation in the bottle in the production of quality sparkling wine and an undesired secondary fermentation in a still wine:
A second fermentation is initiated in the base wine by adding the dosage (filling dosage = sugar and yeast) to the bottle. During the second alcoholic fermentation of this wine, the sugar is converted into alcohol and carbon dioxide, which greatly increases the carbon dioxide pressure in the bottle. In addition, further esters and higher alcohols are produced, which have a positive effect on the flavour of the wine. Bottle fermentation is mandatory by law for champagne, but for other sparkling wines, the second fermentation can also take place in the tank using the méthode charmat. Bottle-fermented sparkling wines are declared on the label using EU-standardised designations. These are Méthode champenoise (only for Champagne), or Méthode classique (also Méthode traditionnelle), which is also permitted in the national language. If there is no indication on the label, it can be assumed that the sparkling wine was not produced according to the classic method.
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Dominik Trick
Technischer Lehrer, staatl. geprüfter Sommelier, Hotelfachschule Heidelberg