There is an opinion that eggs from domestic chickens are usually white, while those from ground-nesting birds have brown shells. This natural palette helps them blend into their environment, including the pebbles and plant debris that line their nests. However, often the color and pigmentation of the shell are primarily determined by the genetic predisposition of specific breeds. For example, white eggs are laid by white breeds like Leghorns — they possess a gene that promotes the formation of white shells, while brown eggs are produced by breeds like Rhode Island or Brown Hen.
The formation of an egg goes through several stages in the chicken's oviduct. A key moment is the late phase when pigments settle on the shell. Different breeds have varying levels of pigmentation. There are two main types of pigments: porphyrin, which gives the brown color, and avoporphyrin — for bluish eggs. These substances are formed from microsomal cytochromes produced by the bird's liver.
Scientific studies show changes in pigment content depending on the season. This is especially pronounced in free-range chickens: during the summer, their diet is enriched with fresh herbs and insects, which affects the color of the shell.
Conducting experiments with various breeds of chickens, researchers attempted to determine how dietary diversity affects the color of eggs. It turned out that chickens with a more varied diet often produce eggs with a richer color. Thus, it can be stated that a hen's health directly influences the quality and color of its product. This pertains not only to the shell but also to the yolk: its color is determined by the hen's diet and can range from pale yellow to deep orange, and sometimes even have a greenish tint.
The quality and color of the shell can also be influenced by adverse environmental conditions and stressful situations. Poor nutrition can lead to changes in the color of the eggs; a deficiency of minerals and vitamins makes the shell less durable and alters its color.
Preferences regarding egg color vary across different countries. For instance, in Germany and France, brown eggs are more popular and often cost more than white ones due to the stereotype that they are more natural or organic. At the same time, in the USA and other countries, white eggs predominate.
Few people know that egg shells can even be green, olive, and bluish; such eggs are laid by breeds like Grünleger and Legbar. They are characterized by their friendly nature, which makes them popular among backyard poultry keepers.
Many consumers mistakenly believe that brown eggs are healthier or tastier than white ones. In fact, it all depends on the hen's diet and living conditions — the color of the egg does not reflect its nutritional properties or taste.
One should not judge the quality of a product by its color: white and brown eggs can be equally tasty and nutritious. Therefore, when choosing eggs, it is better to focus on their freshness and origin.