E552 - Calcium silicate

At a glance

• What it is: A fine, white mineral powder made from calcium and silica; also called E552.
• What it does: Prevents clumping by absorbing moisture; keeps powders easy to pour.
• Where it’s found: Table salt, seasoning mixes, powdered soups and sauces, drink mixes, and some grated or shredded foods.
• Common swaps: Silicon dioxide, tricalcium phosphate, magnesium carbonates, cellulose, and, in salt, potassium ferrocyanide.
• Safety: Recognized by the FDA in the U.S. and specified by the EU for use as an anti-caking agent when used as intended.

Why is Calcium silicate added to food?

Food makers add calcium silicate to stop powders from clumping and to help them flow and measure well. It works by absorbing moisture and oil on particle surfaces, which keeps salt crystals and other dry particles separate.¹

In the EU, E552 is listed with specifications as an anti-caking agent, which sets purity and identity requirements for food-grade material.²

What foods contain Calcium silicate?

You’re most likely to see E552 in free-flowing table salt and salt blends, dry seasoning mixes, powdered soups and sauces, instant drink mixes, and sometimes in grated or shredded products where clumping is a risk. It can also be used in certain meat, poultry, and egg products in the U.S., where it appears on ingredient statements as “calcium silicate” or “E552.”³ EU product categories also allow its use as an anti-caking agent when listed and within specifications.²

What can replace Calcium silicate?

Depending on the recipe and regulations, manufacturers may switch to:

• Silicon dioxide for moisture control in many powders
• Tricalcium phosphate in salts, spices, and powdered mixes
• Magnesium carbonates as a flow aid
• Cellulose in grated or shredded foods as an anti-caking dust
• In table salt specifically, potassium ferrocyanide is another common anti-caking agent

The best choice depends on taste neutrality, label goals, cost, and the food’s moisture and fat levels.

How is Calcium silicate made?

Food-grade calcium silicate is typically produced by reacting a soluble calcium source (such as calcium chloride or lime) with a soluble silicate (such as sodium silicate) to precipitate calcium silicate hydrates. The material is then filtered, dried, and milled to a fine, porous powder.⁴ Chemically, calcium silicate is represented by CaSiO3 (often in hydrated, amorphous forms for food use).⁵

Is Calcium silicate safe to eat?

In the United States, calcium silicate is listed by FDA as an anti-caking agent that is Generally Recognized As Safe (GRAS) for use in foods under good manufacturing practice, including a limit in table salt.¹ In the European Union, E552 appears in the specifications regulation that sets identity and purity criteria for its use as a food additive.²

Toxicology reviews of silicates report low oral toxicity and very limited absorption from the gut at typical dietary levels.⁴ When used as intended, E552 does not meaningfully change a food’s taste or nutrition.

Does Calcium silicate have any benefits?

• It keeps powders free-flowing, which makes mixing and measuring more reliable.
• It helps reduce hard lumps in salt and spice blends, especially in humid conditions.
• It is neutral in taste and works at very low levels, so it has little effect on flavor or texture beyond improving flow.

Who should avoid Calcium silicate?

Most people do not need to avoid E552 when it is used as intended in foods. If a healthcare professional has advised you to avoid added silicates or specific anti-caking agents, check labels. People who must avoid dusty environments for respiratory reasons should handle bulk powders carefully in the workplace; this is a handling issue and not about eating foods that contain E552.

Myths & facts

• “It’s glass.” Fact: Calcium silicate is a mineral-based powder used for moisture control; it is not ground glass.
• “It adds lots of calcium.” Fact: It is used at very small amounts, so it does not make a meaningful contribution to dietary calcium.
• “It’s only in cheap foods.” Fact: Anti-caking agents like E552 are used across budget and premium brands to keep powders free-flowing.

Calcium silicate in branded foods

On labels, look for “calcium silicate” or “E552.” You’ll most often find it on:

• Table salt and salt blends labeled “free-flowing” or “pourable”
• Dry spice and seasoning mixes, rubs, and bouillon powders
• Instant soups, sauces, and drink mixes
• Some grated or shredded foods where clumping is a concern
• Certain meat, poultry, and egg products in the U.S., as listed in the FSIS Safe and Suitable Ingredients list³

References

Footnotes

1. Food Additive Status List — U.S. FDA. https://www.fda.gov/food/food-additives-petitions/food-additive-status-list ↩ ↩²

2. Commission Regulation (EU) No 231/2012 (additive specifications, including E552). https://eur-lex.europa.eu/eli/reg/2012/231/oj ↩ ↩² ↩³

3. FSIS Directive 7120.1: Safe and Suitable Ingredients Used in the Production of Meat, Poultry, and Egg Products — USDA. https://www.fsis.usda.gov/policy/directives/7120.1 ↩ ↩²

4. Silicates (including calcium silicate) — WHO/FAO JECFA Monograph. http://www.inchem.org/documents/jecfa/jecmono/v05je04.htm ↩ ↩²

5. Calcium silicate — PubChem, National Institutes of Health. https://pubchem.ncbi.nlm.nih.gov/compound/Calcium-silicate ↩