Origin
Sodium ferrocyanide is the sodium salt of ferrocyanide and as the name suggests it is an iron-cyanide compound. E 535 is produced through a chemical process that results in a solid product consisting of yellow crystals. Cyanide, which is known to be prussic acid, is so firmly bound to the iron ions that only strong acids could release it and thus make it dangerous. E 535 is highly soluble in water.
Usage
The food additive E 535 is used exclusively as an anti-caking agent to improve the flowability of table salt and salt substitutes. The maximum permitted level for this use is 20 mg/kg. However, E 535 is also additionally used to brighten wine.
Risks
The recommended ADI value is at 0.025 mg per kilogram of body weight. Although sodium ferrocyanide contains prussic acid, E 535 is considered safe because the prussic acid cannot be released by stomach acid. Other food acids are also too weak to release the prussic acid contained in E 535.