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.
If eggs sink to the bottom of a bowl of cold water and lie flat on their sides, they are very fresh. If they are less fresh but still good to eat, they will stand on one end at the bottom. If they float to the surface, they are no longer fresh enough to eat.
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.
Carefully lower your eggs into fresh cold water using a spoon (you can do this in the pan if you're about to boil them). If the eggs stay at the bottom they're fresh; if the eggs float, however, they're stale and best avoided.
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.
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.
Salmonella is common in eggs, whether they are good or bad. However, salmonella is cooked out of eggs with heat. As eggs go bad, they develop other types of bacteria like E. Coli that lead to severe illness.
If it stands straight up but still sinks to the bottom, it's losing some freshness but won't make you sick. However, if the egg floats, it has gone bad and should be discarded. Eggs that are "expired" might stay fresh for a few weeks after their date, but if an egg is spoiled, it should not be eaten.
Fresh eggs are more dense than fresh water and therefore will sink. However, as the water's salt content increases, it becomes denser. The eggs float in the two beakers with the added salt.
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.
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.
To check if it is safe to eat, crack the egg in a bowl and check for an off-odor or unusual appearance before determining whether to use or discard. A spoiled egg has a terribly unpleasant odor when you crack it open — whether raw or cooked.
Best practice is to store eggs in the fridge; that way the temperature is always at a constant and your eggs will be fresher!
An egg can float in water when its air cell has enlarged sufficiently to keep it buoyant. This means the egg is old, but it may be perfectly safe to use.
The good news is Salmonella is killed instantly at 74oC. So even if you are unlucky enough to get an egg with bacteria on it, the food will become safe by cooking it properly.
If it floats, throw it out. The smell test will only identify severely rotten eggs, while the float test will hint at how well the egg will perform as a binder in baking recipes.
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.
What happens if you use old eggs. If you use older eggs, the cakes will not rise as well and pavlovas will be flatter than they should be. Generally, the cakes will still work as long as you get some volume from beating, they just won't be as tall or light-as-air as they should be.
Eggs older than 3 months will likely float and should be tossed out.
How Long Can Eggs Sit Out? According to the USDA, refrigerated eggs should not be left out for more than two hours.
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.