Although there is a date stamped on the side of an egg carton, that isn't always a good indication of whether the eggs inside are fresh. Some dates are when they were packed (and often written in code) while others are best-buy dates. The American Egg Board recommends eggs be used four to five weeks after they were packed, but we may not always know when that was. In addition, if you remove the eggs from the carton when you return from the store, or purchase fresh eggs from a farm, you may be uncertain how old they are.
Luckily, there are three easy ways to determine if your eggs are still safe to eat, and all you need are your senses, a bowl, and some cold water. Keep in mind that if one egg tests bad it doesn't mean the rest of the eggs should be tossed.
The Sink or Float Test
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, a bowl, and cold water. Fill the bowl with enough cold water to completely cover the egg, then gently drop the egg into the bowl of water.
Your egg can do one of three things and each will determine its freshness. If it sinks to the bottom, turns 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. (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.)
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.
The Egg White Test
This test is a good choice if you plan on cracking the egg before cooking it or adding to a baked good recipe. Crack the egg onto a plate or other flat surface and look closely at the consistency of the egg white—it should 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
Often when there is a sulfur odor—whether it has to do with eggs or not—it is described as "rotten eggs." That is because eggs that have gone bad emit a strong sulfur smell. 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.
Whether to Toss or Use
Obviously, if your egg fails any of these tests, 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.
Proper Egg Storage
Eggs should be stored in the refrigerator in the carton they came in. The packaging helps keep out odors and flavors from other foods in the fridge and protects the eggs from breakage. Also, you can use the date stamped on the carton as a guide. Make sure to keep the eggs upright, so the larger end is facing up; the yolk is more prone to spoiliage than the white, and this position keeps the air cell at the top, reducing the chances of harmful bacteria from making its way into the yolk. You can also freeze eggs for longer storage.
Egg Cooking Safety
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 cooked eggs. While it's true that most eggs are not contaminated, if one is, you can get very sick.
If someone in your home has a compromised immune system, is pregnant, or is young or elderly, consider buying pasteurized eggs. (Pasteurized eggs are also good to use in recipes calling for raw eggs, like hollandaise sauce.) 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.
- 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 make into candle molds. You can also save for your indoor or outdoor fires as they make great fire-starters.
American Egg Board. Storage tips: how long do eggs last? Published July 14, 2020.
Whiley H, Ross K. Salmonella and eggs: from production to plate. IJERPH. 2015;12(3):2543-2556. doi:10.3390/ijerph120302543
Centers for Disease Control and Prevention. Salmonella and Eggs. Published February 16, 2021.