Potassium ferrocyanide

Potassium ferrocyanide is an inorganic coordination compound serving as an anti-caking agent in table salt, salt substitutes, and certain other powdered food ingredients. Like its sodium counterpart, it prevents crystalline particles from sticking together by adsorbing onto crystal surfaces and blocking the intermolecular contacts responsible for caking — a critical function in humid climates and during extended storage.

JECFA evaluated potassium ferrocyanide in 1965 alongside related ferrocyanide salts and established an ADI of 0.025 mg/kg body weight per day. This figure reflects the very low use levels needed to achieve technical function: only trace amounts are required to coat salt crystals effectively. Dietary exposure from typical use is well below the ADI, giving a wide margin of safety for regular consumers.

Approved across the EU and in many countries worldwide, E536 is used almost exclusively in salt-based products where free-flow properties are commercially important. The term "ferrocyanide" raises understandable questions, but it refers to a stable iron-cyanide complex that is chemically distinct from toxic cyanide compounds: the bound cyanide ions are not liberated during digestion. Regulatory bodies including JECFA and EFSA have consistently found no meaningful exposure risk at permitted use levels. Potassium ferrocyanide appears most visibly in anti-caking-treated table salt sold in retail and food service markets.