The common chicken eggs found in grocery stores are primarily white or brown. The shell color is a superficial characteristic, determined entirely by the hen that lays them. Simply put, the presence of a pigment on the shell’s surface dictates the final hue, a variation rooted in avian genetics and the specific breed of chicken.
How Chicken Genetics Determine Egg Color
The color of an eggshell is a trait inherited from the hen’s parents and is primarily controlled by the breed. For instance, Leghorn chickens lay white eggs, while breeds like the Plymouth Rock or Rhode Island Red produce brown eggs. A rough, but often accurate, physical indicator of the color a hen will lay can be found in the color of her earlobes. Hens with white earlobes typically lay white eggs, and those with red or brown earlobes tend to lay colored eggs.
All eggshells begin as white, since the base structure is composed of calcium carbonate. The coloring occurs late in the egg formation process, which takes place over about 26 hours within the hen’s oviduct. Brown coloration is caused by the deposition of a pigment called protoporphyrin IX, a derivative of hemoglobin. This pigment is secreted in the shell gland during the final hours, effectively coating the white shell with a brown layer. The amount of protoporphyrin IX deposited determines the intensity of the brown color.
What Shell Color Doesn’t Tell You
The most common misconception about eggs is that a brown shell signifies a more nutritious or higher-quality product than a white one. Scientific analysis consistently shows that the shell color has virtually no impact on the nutritional content, flavor, or cooking quality of the egg inside. A large egg, regardless of its shell color, contains around 70 calories and 6 grams of protein.
Differences in the nutritional profile of an egg are a result of the hen’s diet and living conditions, not the shell’s color. For example, eggs from hens fed a diet supplemented with flaxseed will contain higher levels of Omega-3 fatty acids, regardless of whether the egg is white or brown. Similarly, the richness of the yolk color is determined by the hen’s diet, specifically the presence of yellow-orange pigments in the feed, such as marigold petals or corn. The taste of an egg is also more closely related to its freshness and the hen’s diet than to the shell’s hue.
Why Brown Eggs Sometimes Cost More
Consumers often observe that brown eggs carry a higher price tag than white eggs. This price difference is tied to the commercial breeds that lay each color. The breeds that lay brown eggs, such as Rhode Island Reds, tend to be larger birds than the White Leghorns, which are the main producers of white eggs.
Larger hens generally require more feed to maintain their body weight and sustain egg production. This increased feed consumption translates directly into a higher production cost for the farmer per dozen eggs. Additionally, the brown-egg laying hens are often slightly less efficient at converting feed into eggs compared to the White Leghorn breed. Therefore, the higher price for brown eggs reflects the greater cost of raising and feeding the specific breeds that produce them.