isms from entering the egg. A colourless wax membrane called the cuticle surrounds the outer shell. It is highly alkaline and therefore acts as a bacteriostatic agent – i.e. it prevents bacteria from reproducing. This wax membrane is dissolved by washing, which is why in Denmark it is not allowed to wash eggs before sorting.
Air cell Chalazae Eggshell
Egg yolk
Air cell When the egg leaves the hen, it has a temperature of 39 °C. As it cools, its contents contract, allowing air to penetrate through the shell. In the heavy end of the egg, the outer and the inner shell membrane split apart, and the air cell is formed here. The older the egg is, the larger the air cell, as water continuously evaporates from the egg during storage. Egg white The egg white makes up approx. 60 % of the eggs weight. It consists of 88 % water and 12 % dry matter, primarily protein. The egg white is made of three parts: an inner and an outer liquid layer and in between those a more viscous liquid part. The egg white is heat regulating, adjusts the humidity and supplies nutrition to the chicken foetus. It also prevents
Egg white Chalazae Shell membranes
external bacteria from penetrating the yolk. Bacterial retardant properties The egg white protects the yolk, for example due to its contents of the enzyme lysozyme, which splits the beta-(1.4)- glycoside bond in the cell wall of gram-positive bacteria; this destroys the bacterial cell. The protein ovotransferrin is also a bacteriostatic
agent, in that the binding of iron to ovotransferrin limits the possibilities for certain bacteria’s growth. Colour of the egg white The egg white’s pale yellow-green colour is due to the presence of riboflavin (vitamin B2). Completely fresh eggs contain lots of small air bubbles that can give the egg white a dull milky appearance. This is because of carbon
Egg structure | 7