E551: Silicon dioxide

What is E551?

Silicon dioxide (E551), also called silica, is a compound of silicon and oxygen. The form used in food is synthetic amorphous silica, a fine, light, white powder with a very large surface area that readily absorbs moisture and oils.

Origin and production

Silica is abundant in nature as quartz and sand, but food-grade E551 is manufactured, typically by precipitation from sodium silicate solutions or by burning silicon compounds at high temperature to produce 'fumed' silica.

Why is it used?

Its main job is as an anti-caking agent and carrier: it coats particles so powders stay free-flowing and do not clump. It is found in spice blends, seasoning sachets for instant noodles, powdered drink mixes, protein powders and dietary supplement tablets and capsules.

Vegan, vegetarian and halal

Silicon dioxide is of mineral or synthetic origin and contains no animal-derived material, so it is suitable for vegans and vegetarians and raises no particular halal or kosher concerns on its own.

Safety and regulation

E551 is authorised in the EU and was re-evaluated by EFSA, which did not identify a safety concern at reported use levels but recommended tighter specifications, including better characterisation of particle size.

Common in