Silicon Dioxide
The short version
An amorphous silica powder used as an anti-caking agent in powdered foods, table salt, and spices.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
Silica is one of the most abundant materials on earth. Food-grade material is produced by precipitation from sodium silicate solutions (precipitated silica) or by hydrolysis of silicon tetrachloride (fumed silica).
How it's used
Used as an anti-caking agent in powdered foods, table salt, spices, and powdered drink mixes (typically 1–2%). Also a clarifying agent in beer and wine. The amorphous food-grade form is distinct from crystalline silica (quartz), which is a respiratory hazard.
Safety profile
ADI not specified by JECFA. EFSA re-evaluated in 2018 and noted uncertainty around the nanoparticle fraction; a follow-up review is anticipated. Crystalline forms are not permitted in food. Inhalation of any silica powder is hazardous regardless of form.
Physical & chemical properties
White amorphous powder, insoluble in water. Extremely high surface area — adsorbs moisture, preventing caking. Inert in most chemical conditions.
Regulation worldwide
Permitted globally for anti-caking use. Specific particle-size and crystallinity specifications apply.
Educational information only. Not medical or dietary advice.