Eggs are a kitchen staple, though you can't tell just by looking at an egg whether it is fresh or not. The good news is that there is a very simple way to test the freshness of any egg and there's no need to crack it.
Check Your Egg's Freshness
Egg producers place sell-by-dates on a carton of eggs, though they are not accurate in telling you how fresh the eggs really are. Whether you buy eggs from the store or from a local farmer, all you need is a bowl of water to do a quick freshness check.
Fill a deep bowl, pan, or tall glass 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 between one and three weeks old, which is perfectly acceptable to eat.
- If the egg floats on the surface, it is bad and should be discarded.
Why Does This Work?
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.
Signs of a Bad Cracked Egg
We don't always think about checking the freshness of our eggs before cracking them. That's why it's also good to know how to 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 which doesn't spread much. The yolk will stand up and have a nice, rounded dome.
- If the egg white is quite thin and spreads, it 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 egg.
- When in doubt, give it the sniff test. The smell of a rotten egg is unmistakable and should be apparent immediately upon cracking. If it smells bad, don't eat it.
Choosing and Storing Eggs
Now that you know how to test your eggs, it's time to get a few buying and storage tips.
- 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 which 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.
- Eggs which 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.