Fermentation may be a natural process, but winemakers don’t always let it run its full course. Sometimes, stopping fermentation early is the key to creating a wine that’s sweeter, more stable, or uniquely expressive. In this article, we’ll explore why and how winemakers stop fermentation, and how these choices impact the style and taste of the final wine, from off-dry whites to dessert and fortified wines.

Why stop fermentation?

Fermentation stops naturally when all the sugar in grape juice is converted into alcohol, or when the yeast dies off due to high alcohol levels or extreme conditions. But winemakers often intervene to halt the process before it finishes. The reasons include:

• To retain natural sweetness

• To control alcohol levels

• To preserve certain aromas or freshness

• To prevent refermentation in bottle

• To stabilize the wine for storage and shipping

Techniques to stop fermentation

1. Chilling

Lowering the temperature of the fermenting wine (often below 10°C / 50°F) slows or stops yeast activity. This method is gentle and common in off-dry and semi-sweet wines, especially whites like Riesling or Moscato.

2. Filtration

Using fine filters or sterile filtration, winemakers can remove the yeast from the wine, stopping fermentation in its tracks. This is often combined with chilling.

3. Sulfur addition (SO₂)

Adding sulfur dioxide (a common and legal preservative) can kill or inhibit yeast, halting fermentation while also protecting the wine from oxidation and spoilage.

4. Fortification

A technique used in producing fortified wines, where a neutral grape spirit (brandy) is added to the fermenting wine to instantly raise alcohol levels, killing the yeast.

How stopping fermentation shapes the wine

Stopping fermentation influences key elements like sweetness, alcohol, mouthfeel, and balance. Here’s how it plays out in different wine styles:

Off-dry wines

• Slight sweetness remains to round out acidity.

• Fresh, light-bodied, and easy to drink.

Medium-sweet to sweet wines

• More residual sugar and lower alcohol.

• Lush, fruity, and smooth.

Dessert wines

• Very high residual sugar.

• Some are naturally stopped (by chilling or sulfur), others fortified.

Fortified wines

• Yeast killed by high-proof spirit.

• Sweet and strong, often aged in barrel.

Natural wines

• Minimal intervention; some fermentation stops are uncontrolled.

• Result can be unpredictable, and refermentation in bottle is possible.

• Some natural winemakers chill and bottle quickly, relying on low temperature and minimal sulfur to “pause” fermentation.

The Swirl perspective: Understanding the craft behind sweetness

At Swirl, we believe that knowing how a wine was made gives you deeper appreciation for its style and helps you find wines that truly match your taste. Whether you love a dry red or a softly sweet white, our app helps you explore wines based on sugar levels, body, and production style. No more guessing, just better wine choices, guided by insight.