Sodium Bisulphite
The short version
The sodium bisulfite salt — a common solid sulfite source that releases SO2 on contact with acid.
It's allowed, but comes with clearer cautions — such as reactions in sensitive people, stricter limits, or contested safety. The Safety section below explains why.
Where it comes from
Produced by reacting sodium hydroxide or sodium carbonate with sulphur dioxide. A convenient solid form of the bisulfite ion, the dominant sulfite species at moderate pH.
How it's used
Used in wine, fruit pulp, and industrial processing where the bisulfite ion is preferred over metabisulfite. Releases SO2 on contact with acid. Typical residual SO2 contributions similar to other sulfite forms.
Safety profile
ADI of 0.7 mg/kg body weight (combined sulfites, expressed as SO2). Same allergen concerns as all sulfite-class additives — asthma trigger, anaphylaxis risk, thiamine destruction. Mandatory allergen labelling above 10 mg/kg SO2.
Physical & chemical properties
White crystalline powder, very soluble in water. Releases SO2 in acidic solutions. Pungent sulfur odor.
Regulation worldwide
Permitted globally with strict maximum levels per category. Mandatory allergen declaration.
Educational information only. Not medical or dietary advice.