Egg producers print sell-by dates on a carton of eggs to give an indication of how long you should be able to use them, but they can't tell you how fresh the eggs really are. Whether you buy eggs from a store or from your local farmer, you can determine how fresh they are with this neat trick that involves only a bowl of water.
Lying, Standing, or Floating
Fill a deep bowl or pan with enough cold tap water to cover an egg. Place the egg in the water.
- If the egg lies on its side on the bottom, the air cell inside is small and it's very fresh.
- If the egg stands up on end and bobs on the bottom, the air cell is larger and it isn't quite as fresh. It is probably one to three weeks old, which is perfectly acceptable to eat.
- If the egg floats on the surface, it is bad and should be discarded.
Air Cell Size Equates With Degree of Freshness
Inside every egg is a thin membrane, and between the membrane and the shell is a tiny air cell. This pocket of air grows larger as the egg ages, so a very fresh egg will have a smaller air cell than an older egg.
When you place a whole egg in water, the air cell affects its buoyancy. The larger the air pocket, the more buoyant the egg becomes and the more it will float, giving you an indication of the egg's age. It's basic egg science that you can use to your advantage in the kitchen.
Testing a Cracked Egg's Freshness
If you neglect to check the freshness of eggs before cracking, you can tell if an egg is bad after it's out of the shell.
- A very fresh egg out of the shell will have an overall thick white that doesn't spread much. The yolk will stand up and have a nice, rounded dome.
- If the egg white is quite thin and spreads, the egg is probably past its peak.
- A flattened yolk or one that breaks very easily is an indication that the egg is old.
- The white of a very fresh egg will be cloudy. A clear egg white indicates an older egg, but not necessarily a bad one.
- The smell of a rotten egg is unmistakable and should be apparent immediately upon cracking. If it smells bad, throw it out.
Choosing and Storing Eggs
Before you use your eggs, there are a few things to consider when buying and storing them to help you have the best experience.
- Grade AA eggs are the highest grade available. They cost more than other eggs but may be a good choice because of their high quality and longer shelf life.
- Pasteurized eggs have been immersed in a temperature-controlled water bath for a specified length of time in order to destroy all bacteria inside without cooking the egg. Pasteurized eggs can be used in recipes that call for raw eggs.
- Store eggs in the refrigerator in their original carton. It's best to point the small end down, so get in the habit of flipping your eggs whenever you bring a new carton home. Putting the small end down keeps the air cell at the top, broad part of the egg and reduces the chance of harmful bacteria finding their way from that cell to the yolk, which is more prone to spoilage than the white.
- Eggs that are a week or so old are easier to peel than very fresh eggs when cooked in the shell. This makes them perfect candidates for hard-boiled eggs. To keep hard-boiled eggs fresh, keep them in the shell until you're ready to eat them.