Cochineal is a water-soluble natural dye that is reasonably stable against light, heat, and oxidation. Because of the use of aluminium from alum for complexing, carmine can be described as a “semisynthetic” dye (Dapson, 2007). Amino carminic acid is used in acidic foods; the somewhat insoluble calcium carmine is used in many solid foods.
The European Commission has assigned an E-number of E120 (I) for purified carmine, while the number given for raw dye from ground insects with a carminic acid content of about 20% is E120 (II). Since January 5, 2011, a US FDA regulation requires all foods and cosmetics containing cochineal to declare it in the ingredients list.
There is an azo dye, E124, that is close to cochineal called “cochineal red.” The color is similar but E124 is synthetic.
According to the FCC, carmine comes as bright red, friable pieces or as a dark red powder. It is the aluminium or calcium-aluminium lake on an aluminium hydroxide substrate. Carmine acid crystallizes from water as bright red crystals that darken at 130 °C and decompose at 250 °C. It is freely soluble in water, alcohol, and ether but insoluble in petroleum ether and chloroform.