Sodium Metabisulfite
The short version
A sulfite preservative widely used in wine and dried fruits — a documented allergen for sulfite-sensitive individuals.
A sulfite preservative (common in dried fruit and wine). Sulfites can trigger asthma and other reactions in sensitive people and must be declared on labels, which is why we flag it.
Where it comes from
Sulfites have been used to preserve foods and wines since Roman times — sulfur-burning was practiced in barrels. Sodium metabisulfite was characterized in the 19th century and is produced industrially by reaction of SO2 with sodium carbonate.
How it's used
Widely used in wine, beer, dried fruits, processed potatoes, and shrimp processing. Acts as a preservative, antioxidant, and antimicrobial. Releases sulfur dioxide on contact with water and acids. Typical residual SO2 in wine: 20–250 mg/L.
Safety profile
ADI of 0.7 mg/kg body weight expressed as SO2. A documented allergen — can trigger severe asthma attacks and anaphylaxis in sulfite-sensitive individuals, particularly asthmatics (estimated 5–10% of asthmatics). Mandatory allergen labelling in the EU, US, and most jurisdictions when SO2 exceeds 10 mg/kg. Destroys thiamine (vitamin B1) in foods.
Physical & chemical properties
White crystalline powder, soluble in water releasing SO2 in acidic conditions. Strong reducing agent. Acrid sulfur odor.
Regulation worldwide
Permitted globally with strict maximum levels per product category. Mandatory allergen declaration above 10 mg/kg as SO2.
Educational information only. Not medical or dietary advice.