Egg: What It Is?

Egg: what it is

characteristics

An egg is surrounded by a thin, hard shell. Inside, the egg yolk is suspended in the egg white by one or two spiral bands of tissue called the chalazae (from the Greek word khalaza, meaning hailstone or hard lump.)

The shape of an egg is an oval with one end larger than the other end. The egg has cylindrical symmetry along the long axis. The larger end contains the air cell that forms when the contents of the egg cool and contract after it is laid.

Shell

Main article: Eggshell

Egg shell color is caused by pigment deposition during egg formation in the oviduct and can vary according to breed, from the more common white and brown to pink or speckled blue-green. Although there is no significant link between shell color and nutritional value, there is often a cultural preference for one color over another. For example, in most regions of the United States, eggs are generally white; while in the northeast of that country and in the United Kingdom, eggs are generally light-brown.

White (Albumen)

Main article: Egg white

Yolk

Main article: Egg yolk

The yolk in a newly laid egg is round and firm. As the yolk ages it absorbs water from the albumen which increases its size and causes it to stretch and weaken the vitelline membrane (the clear casing enclosing the yolk). The resulting effect is a flattened and enlarged yolk shape.

Yolk color is dependent on the diet of the hen; if the diet contains yellow/orange plant pigments known as xanthophylls, then they are deposited in the yolk, coloring it. A colorless diet can produce an almost colorless yolk. Farmers may enhance