Carotenoids are biological pigments found in plants and photosynthetic microorganisms such as algae, some fungi and some bacteria. There are over six hundred types of carotenoid. Essentially carotenoids are divided into two classes: xanthophylls and carotenes. Xanthophylls are oxy and hydroxy derivatives of carotenes. The main example is lutein. The contribution of lutein in the color of egg yolk is approximately 70. Xanthophylls are the ones that give the chicken skin a yellow color. At the same time, bright yellow color in durum wheat is formed by lutein pigment from xanthophyll group.

Of the carotenoids, especially xanthophylls are the most common color pigments in poultry feeds. Xanthophylls in feed have an important role in the formation of skin color. Poultry cannot synthesize carotenoids. Therefore, these substances must be administered externally, either naturally or synthetically. Natural or synthetic color substances are added to the feed of laying hens and broilers. Plants containing natural xanthophylls include alfalfa, paprika, marigold and algae. Maize also contains natural coloring compounds that contain high amounts of xanthophylls. If synthetic pigments are to be added to the feed of poultry, it is important that the red and yellow color substances are present in the feed in the correct proportions.

In the authorized laboratories, xanthophyll determination studies are carried out by using High Performance Liquid Chromatography (HPLC) device in animal feeds within the scope of chemical tests. The HPLC method, which is a very sensitive method, gives highly sensitive results in the separation of non-volatile or easily degradable compounds at temperature. Some of the standards considered in these studies are:

• TS 6078 Animal feed - Determination of carotene and xanthophylls
• TSE CEN / TS 16233-1 Foodstuffs - Determination of xanthophylls in fish meat by HPLC method - Part 1 Determination of astaxanthin and cantaxanthin
• TSE CEN / TS 16233-2 Foodstuffs - Determination of xanthophylls in fish meat by HPLC method - Part 2: Determination of enantiomer ratio of astaxanthin