Calcium ferrocyanide

Calcium ferrocyanide is a member of the ferrocyanide salt family approved as an anti-caking agent in food. It prevents crystalline ingredients — particularly table salt — from forming hard lumps during storage by coating crystal surfaces and disrupting the particle-to-particle adhesion that causes powders to clump. Compared with the sodium and potassium variants, calcium ferrocyanide is used somewhat less frequently but serves the same technical purpose.

JECFA assessed calcium ferrocyanide in 1965 as part of its evaluation of ferrocyanide salts and established an ADI of 0.025 mg/kg body weight per day. This conservative limit applies to the additive class collectively, ensuring that combined intake from any ferrocyanide source remains well controlled. The quantities used in food are minute, and normal dietary exposure is far below the established safety threshold.

Calcium ferrocyanide is permitted in the EU and other jurisdictions for use in salt and salt substitutes. The ferrocyanide complex is highly stable and does not break down to release toxic cyanide under normal food-processing or digestive conditions, making it fundamentally different from free cyanide compounds despite the shared chemical terminology. For consumers who read ingredient lists carefully, the presence of E538 in salt products indicates an anti-caking function rather than any flavour or nutritional role. It does not affect the taste, colour, or sodium content of the salt in which it is used.