Iron Oxides
What it does
Red/yellow/black colours.
How it's made
Manufactured iron oxides/hydroxides.
Iron oxides and hydroxides are natural mineral pigments giving yellow, red, orange, brown and black shades. In food they are used to colour products such as sweets, cake decorations, some meat and fish pastes, and pill and tablet coatings, providing earthy, stable colours.
The colours correspond to different forms of iron oxide: red from ferric oxide, yellow from iron oxide hydroxide, and black from a mixed iron oxide, with browns produced by blending these. Food-grade iron oxides are almost always made synthetically rather than mined, by precipitating iron salts from solution and then controlling the heating and oxidation to develop the required colour and particle form; synthesis gives much better purity than natural ores.
The precipitated pigments are washed, dried and milled to fine powders. Because they are insoluble, they colour by dispersion rather than dissolving, and the food-grade material is made to strict limits on heavy metals and other impurities, giving very stable, light- and heat-resistant colours.
Possible reactions
Generally safe and inert.