Why is sugar added to sparkling wine?

Liqueur de tirage: sugar for the bubbles

The bubbles in sparkling wine come from a second fermentation. To get it started, the finished base wine receives a liqueur de tirage, the French term for the tirage dosage. This is a solution of sugar and yeast, often combined with a riddling aid that makes it easier for the yeast to settle out later. A typical benchmark is around 24 grams of sugar per liter. This generates about 6 bar of pressure in the sealed bottle.

The yeast processes almost all of this sugar. What remains is carbon dioxide, which dissolves into the wine under pressure, and a bit more alcohol. Under EU law, the liqueur de tirage may raise the cuvée's total alcohol by at most 1.5% by volume. This step has nothing to do with sweetness. A Brut Nature goes through it just the same as a Demi-Sec.

An example makes the roles clear. A Brut sparkling wine with 8 grams of sugar received around 24 grams of sugar per liter before the second fermentation. Virtually none of that remains. The 8 grams in the finished wine come almost entirely from the liqueur d'expédition and the small natural residue. The yeast therefore processed many times more sugar than what's ultimately tasted in the glass.

The riddling aid serves a practical purpose. After fermentation, the dead yeast needs to slide down into the neck of the bottle as a compact plug. If it sticks to the glass wall, riddling doesn't work well. This additive has nothing to do with sweetness—it ensures a clean, clear bottle.

Liqueur d'expédition: balancing the acidity

Grapes for sparkling wine are picked earlier than for still wine, based on acidity rather than sugar ripeness. The reason lies in style. A sparkling wine should feel fresh and lively, and the second fermentation needs a lean base wine without too much alcohol. The result is a wine with high acidity that often tastes sharp and harsh on its own.

The carbon dioxide intensifies this impression, since it further stimulates the tongue. A few grams of sugar round this off without the wine being perceived as sweet. Sugar and acidity act like counterweights here. Anyone who's had lemonade without sugar knows this—it's barely drinkable. In sparkling wine the amounts are much smaller, but the principle is the same.

How much balancing a wine needs depends on grape variety and origin. Riesling often brings very pronounced acidity, Chardonnay from warm sites considerably less. A Riesling-based sparkling wine can therefore often handle a few extra grams of dosage without tasting sweet. The same amount could make a low-acid wine feel heavy and flat.

Is dosage sweetening? What EU law says

Legally, neither the liqueur de tirage nor the liqueur d'expédition counts as enrichment or sweetening. This is stated in Annex II of Regulation (EU) 2019/934. Enrichment means raising the potential alcohol; sweetening means adding sugar to a finished wine afterward. Both are regulated separately for sparkling wine. The cuvée itself—the base wine before the second fermentation—may not be sweetened.

The distinction sounds like splitting hairs, but it carries weight. It makes clear that the dosage is part of the production process, not a fix for a flawed wine. Carbon dioxide is regulated too. In sparkling wine and quality sparkling wine, it may only come from fermentation. Anyone who adds carbon dioxide must label the product as sparkling wine with added carbon dioxide.

Sweeter in the past, drier today: how dosage has changed

In the 19th century, sparkling wine was generally drunk much sweeter than today. The names of the sweetness categories still reflect this, as Station 2 shows. Since then, taste has shifted step by step toward dryness. Brut is now the standard category for Champagne, and Extra Brut as well as Brut Nature have gained more followers in recent years.

Climate affects the dosage too. In warm years, grapes ripen further, acidity drops, and the base wine brings more richness of its own. Many producers then need less sugar to achieve the same balance. Still, less dosage isn't proof of quality on its own. A well-balanced Brut with 8 grams can feel more harmonious than a sparse Brut Nature made from underripe grapes.