Potassium Metabisulphite
The short version
A potassium metabisulfite preservative — common in winemaking as a low-sodium sulfite source.
A sulfite preservative (common in wine and pickles). Sulfites can trigger breathing problems in people with asthma and reactions in other sensitive people, so labels must declare them. That's why we flag it.
Where it comes from
Produced by reaction of SO2 with potassium carbonate. The potassium analog of the more common sodium metabisulfite. Chosen when sodium content is a concern.
How it's used
The dominant sulfite source in commercial and home winemaking — both as preservative in finished wine and as sanitizer for equipment. Also in cider, beer, and some pickled vegetables.
Safety profile
ADI of 0.7 mg/kg body weight (combined sulfites). Same allergen profile as all sulfite forms. The potassium content is generally beneficial vs. sodium but the SO2 exposure and asthma trigger risk are identical.
Physical & chemical properties
White to slightly yellow crystalline powder. Soluble in water releasing SO2 in acidic conditions. Pungent sulfur odor.
Regulation worldwide
Permitted globally with strict maximum levels. Mandatory allergen declaration as SO2.
Educational information only. Not medical or dietary advice.