Naturally occurring iron oxides can not be used because it is difficult to clean then and the color is difficult to control. They are more commonly known as rust… E172 will be syntactically produced occurring pigments of iron, which can be yellow, red, orange, brown or black in colour. there is no maximum limits as to how much can be added into the foods.
Manufactured by treating a solution of ferrous sulphate or chloride with an alkali and oxidising the precipitate in hot air. As the iron present in these oxides is in the ferric form it is not very actively available to body tissues.
Also check out these good links on nutrition
Can be found in cake and dessert mixes, meat paste, salmon and shrimp paste.
Toxic at high doses, and it has been banned in Germany.
