egg

An egg is a reproductive body produced by female animals of many species, but the egg most commonly consumed by humans is the chicken egg. Eggs consist of a yolk, a surrounding white (albumen), membranes, and a hard outer shell. They are laid in a shell that protects the contents and provides pores for gas exchange.

Fertilized eggs, if incubated, can develop into embryos, while unfertilized eggs used for food do not contain developing animals. Shell color ranges from white to brown depending on breed and pigments; size varies by country and breed. The shell's protective layers, including the cuticle, help keep bacteria out.

Commercially produced eggs come from poultry farms and can be graded by weight or quality. They should be refrigerated to slow bacterial growth. Pasteurized eggs are heated to destroy pathogens while preserving liquid contents. Safe handling includes avoiding raw eggs in vulnerable populations.

Nutritionally, eggs are a source of high-quality protein, vitamins A, D, B12, riboflavin, and minerals such as selenium. A large egg provides about 70 calories, and contains cholesterol, which has modest impact on most people's blood cholesterol when consumed within a balanced diet. In cooking, eggs act as binders, emulsifiers, foaming agents, and thickeners.

Culinary uses span from boiled and fried eggs to eggs in baked goods, custards, meringues, and mayonnaise. Throughout history, eggs have been valued as a versatile food and symbol in various cultures; domestication of the chicken in parts of Asia and the Near East contributed to widespread egg consumption.