Eggshell (11%) is made almost entirely of calcium carbonate (CaCO3) crystals. It is a semipermeable membrane, which means that air and moisture can pass through its pores. An air chamber forms when the contents of the egg cool and contract after the egg is laid. The air cell grows larger as an egg ages. Chalaza’s function is to hold the yolk in place inside of an egg’s albumen but it can tell a lot about the egg’s freshness as well. The egg white (58%) is known as the albumen, which comes from albus, the Latin word for “white.”

Four alternating layers of thick and thin albumen contain approximately 40 different proteins, the main components of the egg white in addition to water. Vitelline membrane is the clear casing that encloses the yolk. The yolk contains (30%) less water and more protein than the white, some fat, and most of the vitamins and minerals. These include iron, vitamin A, vitamin D, phosphorus, calcium, thiamine, and riboflavin. The yolk is also a source of lecithin, an effective emulsifier. Yolk color ranges from just a hint of yellow to a magnificent deep orange, according to the feed and breed of the hen.