If they sink to the bottom and lay flat on one side, they are fresh and good to eat. A bad egg will float because of the large air cell that forms at its base. Any floating eggs should be thrown out.
The float test works because air builds up inside the egg as it ages, increasing its buoyancy. However, an egg that floats may still be safe to eat, according to the United States Department of Agriculture (USDA).
As an egg ages, this air cell grows larger as the yolk and white further contract. Therefore, an older egg is less dense and more likely to float in boiling water. Store-bought eggs can last several weeks beyond their sell-by date or expiration date. To reduce the chances of eggs going bad, keep them refrigerated.
If the egg stands on its pointed end at the bottom – it is still safe to eat but best used for baking and making hard-cooked eggs. If the egg float – they're stale and best discarded.
Overcooked hard-boiled eggs are safe to eat (in moderation) as they release a minimal amount of iron sulfide, which would be dangerous if consumed in excess. If an egg is overcooked, it'll develop a bluish-green tint around the yolk, but as long as it is fresh, it can be eaten safely. What is this?
The theory is that, as an egg ages, the air pocket inside it grows larger, buoying an old egg to the surface. But, according to Dr. Schaffner, “there is no scientific basis for the egg float test.” So experimenting to see if your egg sinks or swims is not a reliable way to measure its quality.
The best way to test if your eggs are still good after you've boiled them is, again, the smell test. Basically, you'll notice the smell is off if an egg is starting to go bad. This is true for raw eggs and it's true for boiled eggs—the funk doesn't lie.
If the eggs sink to the bottom and lay flat on their side, they're still fresh. However, if they sink, but stand on one end at the bottom of the glass or bowl, they're not as fresh but still edible. Of course, if any eggs float to the top, they shouldn't be eaten.
You can eat eggs past their expiration date. Just be sure to keep your eggs egg-cellent by storing them correctly. If you don't know if an egg is good or not, you can try the float test or give it a whiff. If it doesn't pass the test, throw it away.
After boiling your eggs, ensure that you label and date them. If they are older than the date you mark them, they are likely spoiled and should be thrown away. If the yolk is watery or gray, the egg is likely rotten.
Old eggs should always be disposed of responsibly to avoid contamination and food-borne illnesses. You can choose to compost, feed them to animals, recycle them at local centers, or throw them in the trash. Eggs with foul odors or discoloration may be spoiled and should not be eaten.
For one to four eggs, bring the water to a rolling boil, cover the pot, and turn the heat down to its lowest setting for 12-14 minutes. For five to eight eggs, cook for 15 to 18 minutes. For nine to one dozen eggs, cook for 20 minutes. After cooking, transfer the eggs to a bowl of ice water.
Keeping Hard-Boiled Eggs Fresh
The shell will help to protect the egg from bacteria, and can help prevent them from absorbing odors from other foods in your refrigerator. A quick beginner's tip is that hard-boiled eggs can be preserved up to 7 days in the refrigerator.
Can You Reboil an Egg? Do you have a strong suspicion that you undercooked your boiled eggs, or did a crack tell you the batch wasn't quite done? As long as an egg's shell hasn't been cracked, it's perfectly fine to put it back in hot water and continue cooking it.
Once the water is at a rolling boil, turn off the heat and cover the pot with the lid. Allow the eggs to sit in the hot water for the following times according to the desired doneness: 3 minutes for SOFT boiled; 6 minutes for MEDIUM boiled; 12 minutes for HARD boiled.
Set your timer for 4-5 mins for runny/dippy eggs to serve with soldiers, or 6-7 mins for soft-boiled eggs for a salad. If serving in a salad, plunge the eggs into a bowl of cold water as soon as the timer goes off – this will stop them cooking and cool the shells quickly for peeling.
A boiling start for 30 seconds to a very gentle simmer for 13 minutes, then an ice bath at the end makes perfect, easy-to-peel hard-boiled eggs.
Eggs may be refrigerated three to five weeks from the day they are placed in the refrigerator. The "Sell-By" date will usually expire during that length of time, but the eggs will be perfectly safe to use. Always purchase eggs before the "Sell-By" or EXP (expiration) date on the carton.
An unwashed egg will last for 6 months or more in the refrigerator. If the fresh eggs have been washed, then the shelf life will be similar to a store bought egg - about 4-5 months.
The water test for egg freshness
Very fresh eggs will sink to the bottom and lay on their sides. If an egg stays at the bottom but stands on its small end, it's still acceptable to eat; just not quite as fresh.