Shell

The egg’s outer shell accounts for 9 to 12 percent of its total weight and is the egg’s first line of defense against bacterial contamination. A protective coating called the cuticle, or bloom, covers the surface of the shell and serves to preserve freshness and prevent microbial contamination of the contents by blocking the pores in the shell. The strength of the shell is greatly influenced by the vitamins and minerals in the hen’s diet—the higher the consumption of calcium, phosphorus, manganese, and vitamin D, the stronger the shell. There are as many as eight thousand almost infinitesimal pores covering the shell of a typical chicken egg. These pores permit air to enter the egg and allow moisture and carbon dioxide to escape.