What do eggs gradually lose as they get older?

* Moisture: Water evaporates through the pores in the shell, making the egg lose its plumpness and become smaller.

* Carbon dioxide: This gas also escapes through the pores, which leads to a higher pH (more alkaline) inside the egg. This change in pH weakens the egg white's ability to bind water.

* Quality of the egg white: As the egg ages, the egg white thins and becomes more watery. This is because the protein structure of the white breaks down.

* Quality of the yolk: The yolk becomes more flat and spreads out. Its color may also fade. The yolk also becomes more runny.

* Freshness: This is a general term encompassing all the changes that occur, resulting in a less desirable egg.

These changes can affect the quality of the egg in cooking and baking. Older eggs may be harder to beat into a stiff meringue, and the yolk may not hold its shape as well when cooked.

How to tell if an egg is old:

* The Float Test: Place the egg in a bowl of cold water. A fresh egg will sink to the bottom and lie flat. An older egg will stand on its end or even float.

* Smell Test: A fresh egg should have no odor. An older egg may have a slightly unpleasant smell.

* Look at the Yolk: The yolk of a fresh egg will be round and firm. The yolk of an older egg will be flat and spread out.

* Check the Date: While not always accurate, the date on the egg carton is a good indicator of its freshness.

It's best to use eggs as soon as possible after purchase. They can be stored in the refrigerator for up to 3-5 weeks.