Testing Eggs for Freshness

Testing eggs freshness in water

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We've all probably had this experience: The carton of eggs in your fridge have been there for a while, and the date stamped on the side is just a date—does that mean when they should be sold by or by when they should be eaten? And, considering we don't know when the eggs were shipped and how long they were stored before landing on the store shelf, it is uncertain how fresh they really are. Eggs are generally good for about three weeks after you buy them, but if you don't remember when you purchased the carton, that information isn't much help.

But don't toss out those eggs just yet! Luckily, there are three easy ways to determine if your eggs are still safe to eat. 

Does It Sink or Float?

Like a fun science experiment you may have done in school, this freshness test is not only simple but also can tell you the approximate age of the egg. All you need is the egg and a bowl of cold water. Make sure there's enough water in the bowl to completely cover the egg, then gently drop the egg into the bowl of water. Your egg can do one of four things and each will determine its freshness. If it sinks to the bottom, sits on its side, and stays there, it is very fresh. If the egg sinks but floats at an angle or stands on end, the egg is a bit older (a week to two weeks old) but still okay to eat. If the egg floats, it's too old and should be discarded.

The science behind this is that as eggs age, the shell becomes more porous allowing air to flow through. The more air entering through the shell, the larger the air cell becomes (the pocket of air between the membrane and shell in the larger end of the egg). The air sac, when large enough, makes the egg float.

If you are looking for more of a cut and dry test, dissolve 2 tablespoons of salt in 2 cups of cold water. Put the egg in the water—if it sinks, it's good; if it floats, it's too old.

An Examination of the White

You will need to crack the egg for this test, but if you plan on cooking the egg (other than hard boiling) or adding to a baked good recipe, you would be opening it up anyway. Crack the egg onto a plate or other flat surface and look closely at the consistency of the egg white—you want it to be slightly opaque, not spread out too much, and appear thick and somewhat sticky. If it is watery, clear, and runny, the egg has lost its freshness. This is due to the fact that as eggs age, the white turns liquidy and breaks down. You will also notice the yolk will be slightly flat on top instead of rounded.

The Sniff Test

We've all experienced the smell of rotten eggs, but the odor usually has nothing to do with eggs at all. It is the sulfur that we recognize, which will emit from an egg that has gone bad. If the egg is really past its prime, you may smell it through the shell; but if not and you're concerned about freshness, take a whiff after you crack it.

To Toss or to Use?

Obviously, if your egg smells terrible, you should get rid of it. But if the egg is showing signs of age but not ready for the trash, you can still use it. Older eggs are ideal for hard boiling—since the air cell is larger, there is more space between the shell and the egg, making it easier to peel.

And if you think some of the eggs in your refrigerator are hardboiled but not sure which, you can easily decipher the two. Take the egg and spin it on a flat surface; if the egg wobbles, it's fresh (the insides are moving around). If the egg spins smoothly, it's cooked.

Whether your eggs are okay to use or not, you will still be left with the shells and carton. Don't toss in the trash! Eggshells are great for the compost, as well as cleaning teapots and making sidewalk chalk. And the cardboard cartons are perfect for art projects—use as a paint pallet, turn into a bird feeder, and use them as candle molds. You can also save for your indoor or outdoor fires as they make great fire-starters.

The Danger of Eating Bad Eggs

Because salmonella and other pathogenic bacteria are present in most eggs, it is recommended that you should always cook your eggs to well done. The bacteria can be inside the shell, so even if you wash the egg or soft-cook it, you could get sick if it's undercooked. Always cook fried eggs to well done, cook scrambled eggs until they are 165 F, and cook hard-cooked eggs until they are completely firm. And always refrigerate eggs, whether cooked or uncooked.

While it's true that most eggs are not contaminated, if one is, you can get very sick. There have been large-scale outbreaks of salmonella from shell eggs in the past; in 2010, for example, 60,000 Americans were sickened with salmonella from eggs. If someone in your home has a compromised immune system, is pregnant, or is young or elderly, think about buying pasteurized eggs. These are eggs that have been quickly heated to a temperature high enough to kill bacteria but low enough so the egg remains uncooked. Follow expiration dates to the letter with this product.