Why are there differences in yolk colour?
Yolk colour depends on the diet of the hen. If she gets plenty of yellow-orange plant pigments known as xanthophylls, they will be deposited in the yolk. Hens fed mashes containing yellow corn and alfalfa meal lay eggs with medium yellow yolks, while those eating wheat or barley yield lighter-coloured yolks. A colourless diet, such as white cornmeal produces almost colourless yolks. Natural yellow-orange substances such as marigold petals may be added to light-coloured feeds to enhance yolk colour. Artificial colour additives are not permitted. Most buyers in this country prefer gold or lemon-coloured yolks. Yolk pigments are relatively stable and are not lost or changed in cooking. Sometimes there is a greenish ring around hard-cooked egg yolks. It is the result of sulphur and iron compounds in the egg reacting at the surface of the yolk. It may occur when eggs are overcooked or when there is a high amount of iron in the cooking water. Although the colour may be a bit unappealing, the
