The color of the egg yolk and of some birds such as the red Belgian canary, and the flamingo are due to the deposition of xanthophyllic carotenoids. These substances can be found naturally in foods such as corn, annatto, carrots, turmeric and in a synthetic form such as canthaxanthin, widely used for coloring the egg yolks of laying hens and quails.
Classification of carotenoids
These are known as pro-vitamin A carotenoids, and are composed exclusively of hydrocarbons. Of the various carotenoids found, only 50 are precursors to vitamin A.
Xanthophylls are also known as inactive carotenoids. These have antioxidant and dye function. As for their composition, they differ from carotenes in that they have functional groups such as ketone, in addition to having oxygen. In order to have coloring, a minimum of 7 double bonds is required, which may be cis or trans. The more double bonds the more intense the staining, those under 7 are colorless.
Canthaxanthin can be found in nature, and has a red color, being in the group of carotenoids with some antioxidant action. However, those used in feed are manufactured industrially, which makes them synthetic.
It is the most widely used synthetic pigment in the food and cosmetic industry.
In animal production it is widely used to intensify the color of the egg yolk of laying hens and to give color to the carcass. It is also widely used as a color enhancer for domestic birds.
Because it is a carotenoid with several double bonds, canthaxanthin oxidizes easily due to temperature, incidence of light and pH, and some care in storage is important.