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E550Anti-caking agentLow concern
Sodium Silicate
In plain words
The short version
Water glass — a niche anti-caking agent now largely replaced by silicates of calcium and magnesium.
Why it's green
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Safety profile
ADI not specified — historically considered safe at trace residual. The deprecation reflects formulation preference rather than safety re-evaluation.
The detail
Manufactured by reaction of sand with sodium carbonate at high temperature. The aqueous solution is the historic 'water glass' used for egg preservation (the alkaline glass coating sealed eggshells against bacterial entry).
Largely deprecated for direct food use — replaced by the calcium and magnesium silicates (E551–E553) in modern formulations. Some niche use remains. Major non-food applications in detergents and silica-gel manufacturing.
Colorless to slightly yellow viscous solution or white solid. Soluble in water with strongly alkaline solution.
Not on the EU list of authorised food additives. In the US, sodium metasilicate is affirmed as GRAS as a processing aid (for example in washing and lye peeling of fruits, vegetables and nuts), and sodium silicate is GRAS as a substance migrating to food from paper and paperboard packaging.
Sources
- 21 CFR 184.1769a — Sodium metasilicate (affirmed GRAS) — eCFR / US FDA, 2026. US status: sodium metasilicate GRAS only as a processing aid (washing/lye peeling of produce and nuts, tripe denuding, hog scald, bottled-water corrosion preventative)
- 21 CFR 182.90 — Substances migrating to food from paper and paperboard products — eCFR / US FDA, 2026. US status: sodium silicate GRAS as a substance migrating from food-packaging paper
- Regulation (EC) No 1333/2008 on food additives — consolidated text of 18.08.2026 (Annex II, Union list) — EUR-Lex / European Union, 2026. EU status: E 550 / sodium silicate is not on the Union list (list goes from E 541 to E 551)
Checked against these sources on .
Educational information only. Not medical, dietary or veterinary advice. Spotted an error? Tell us.