Sodium ferrocyanide

Yellow prussiate of soda, as sodium ferrocyanide is commonly known, is an inorganic salt used in food chiefly as an anti-caking agent. Added to table salt and other crystalline ingredients, it prevents particles from bonding together in humid storage conditions, keeping the product free-flowing. It functions by adsorbing onto crystal surfaces and physically interrupting the intermolecular contact that causes clumping.

JECFA first evaluated sodium ferrocyanide in 1965 and established an ADI of 0.025 mg/kg body weight per day. This conservative limit was derived from long-term animal studies and reflects a cautious approach to a compound used in very small functional quantities. Typical dietary exposure from permitted food uses falls substantially below this threshold, meaning habitual consumers of foods containing E535 are not expected to approach the ADI under normal conditions.

Sodium ferrocyanide is approved in the EU and in numerous other jurisdictions primarily for use in salt and salt substitutes. Consumer concern about the word "cyanide" in the name is understandable but not warranted: the ferrocyanide ion contains cyanide groups tightly bound to iron in an extremely stable complex that does not release free hydrogen cyanide under physiological conditions. This structural distinction has been consistently upheld in regulatory reviews. The additive appears in everyday seasoning products including refined table salt, where it ensures reliable performance from the packaging to the table.