What is typically added to wine bottles before secondary fermentation occurs in sparkling wine production?

In sparkling wine production, before secondary fermentation occurs, sugar and yeast are typically added to the wine bottles. This process is known as méthode traditionnelle or méthode champenoise, where the initial fermentation produces a base wine. During the secondary fermentation, the added sugar (approximately 24 grams of sugar per liter for traditional sparkling wines) acts as a food source for yeast, leading to carbon dioxide production and thus, the bubbles characteristic of sparkling wine.

Adding sugar and yeast is crucial for achieving the desired pressure and effervescence in the final product. The yeast also contributes to the development of complex flavors and aromas during the aging process in the bottle. This step differentiates sparkling wine from still wine, which does not undergo this second fermentation.

Although additional base wine could theoretically be added to balance flavors, it is not standard practice at this stage of production. The use of water or flavoring agents would be atypical in the context of creating traditional sparkling wines, as they do not align with classic methods that emphasize maintaining the integrity and purity of the wine's character.