Other names for the additive (synonyms)
General information
The food additive E535 — sodium ferrocyanide — belongs to the category of technological food additives intended to improve the flowability of products and is used in the food industry mainly as an anti-caking agent in salt.
Sodium ferrocyanide does not occur naturally. It is an additive of synthetic origin obtained by controlled chemical synthesis.
Despite the presence of the term “cyanide” in its name, the additive is not a source of free cyanide and is chemically stable under normal conditions of use.
Ferrocyanides have been known since the 18th century as products of inorganic chemistry and were initially used in pigments and metallurgy. The food use of sodium ferrocyanide as the food additive E535 became widespread in the 20th century, when its effectiveness as an anti-caking substance for table salt was demonstrated.
The chemical formula of sodium ferrocyanide is Na₄[Fe(CN)₆]·10H₂O (decahydrate). The food additive E535 appears as yellow or yellowish-white crystals or powder, is readily soluble in water, thermally stable, and non-volatile. In acidic media under extreme conditions, sodium ferrocyanide may decompose; however, such conditions do not occur in foods.
For the food industry, the food additive E535 is produced by synthesis from inorganic iron salts and cyanide complexes, followed by purification and control of impurity levels, in particular nickel.
Effects on the body
Benefits of Additive E535
Sodium ferrocyanide is not a natural substance for the human body and does not perform any physiological or nutritional function. It is not absorbed as a source of minerals and has no vitamin activity.
The benefit of the food additive E535 is exclusively technological — preventing caking of table salt, which ensures stable product quality, uniform dosing, and reduced food losses.
Risks of Additive E535
Potential risks associated with the food additive E535 are considered low when regulatory use levels are observed. Sodium ferrocyanide has very low bioavailability, and the cyanide groups in its structure are bound in a stable complex and do not release toxic cyanide in the gastrointestinal tract. However, if permitted intake levels are exceeded or if non-food-grade E535 is used, undesirable effects may occur. Particular attention is paid to nickel content, which may cause allergic reactions in sensitive individuals.
The EFSA (European Food Safety Authority), in its 2018 scientific opinion on additives E535, E536, and E538, confirmed that the use of ferrocyanides as anti-caking agents in salt does not pose a risk to consumer health when intake levels are respected.
The Panel established a group acceptable daily intake (ADI) for sodium, potassium, and calcium ferrocyanides of 0.03 mg/kg body weight per day, expressed as ferrocyanide ion.
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) also concluded that ferrocyanides have low toxicity and may be used for food purposes within established limits. The U.S. Food and Drug Administration (FDA) permits the use of ferrocyanides as anti-caking agents in salt in limited amounts.
Uses
In the food industry, the food additive E535 is used exclusively as an anti-caking agent. The main area of application is table salt and salt mixtures.
The food additive E535 prevents lump formation, ensures stable flowability of the product, and facilitates storage and transportation. Sodium ferrocyanide is not used directly in finished food products but is added at the salt production stage in very small concentrations.
Legal Status
In the European Union, sodium ferrocyanide (food additive E535) is permitted under Regulation (EC) No 1333/2008 as a food additive with a maximum permitted level. In Ukraine, the food additive E535 is permitted for use in food-grade salt in accordance with sanitary standards harmonised with the EU.
In the United States, the food additive E535 is permitted by the FDA as an anti-caking agent in salt. In Canada and Japan, the use of ferrocyanides is also permitted with clear ADI limits.