What is Sulfites?

Understanding Sulfites

Sulfites (sulfur dioxide, or SO₂) are both a natural byproduct of fermentation and an additive used by winemakers to preserve wine. All wines contain some sulfites—yeast naturally produces small amounts during fermentation—but most winemakers add additional sulfites to protect the wine from oxidation and unwanted bacterial activity. Sulfites act as an antioxidant and antimicrobial agent, keeping wine fresh, stable, and true to the winemaker's intention from bottling through years of storage. The amount varies significantly: sweet white wines typically contain the most (up to 300 ppm), while dry reds tend to contain less (50-150 ppm) because their tannins provide natural antioxidant protection. Wines labeled "no sulfites added" or "organic" in the US must contain less than 10 ppm total, though they still contain trace amounts from fermentation.

Examples

• 1US law requires a "Contains Sulfites" label on any wine with more than 10 parts per million
• 2Dried apricots contain roughly 10 times more sulfites than a glass of wine
• 3White wines generally contain more sulfites than reds because they lack tannins for natural preservation
• 4Natural winemakers minimize sulfite additions, relying on careful cellar practices to protect the wine

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