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 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.
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.
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.
An egg will be buoyant (float) if the weight of the egg is less than the weight of the water it displaces. The egg sinks if it weighs more than the weight of the water that is displaced. Ships float for the same reason. Their physical weight is less than the weight of the water that is displaced.
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.
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.
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.
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.
Anyway, as the egg gets older it ends up with more gas inside and less water, and the gas is lighter than the water. Overall, this makes the egg lighter and in fact less dense than water so that a stale egg floats.
Eggs older than 3 months will likely float and should be tossed out.
Fresh eggs can be kept refrigerated for up to 6 weeks but always check the use by date displayed on the carton. It is best to put eggs in the fridge as soon as you get them home.
As long are they are kept refrigerated at 45 °F or lower, fresh shell eggs are safe to be consumed four to five weeks beyond the carton's Julian date (the date eggs were packed).
Generally speaking, you recover when you ate rotten egg in just a couple of days. When sick, make sure to hydrate with diluted sports drinks, ginger ale and water. For those that are very young or old, or have an immune system problem, a visit with the doctor is highly recommended.
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. Spoiled eggs could be contaminated with salmonella, a bacterial infection that leads to diarrhea, vomiting, fever, and cramps.
Place your eggs in the water. If your eggs sink to the bottom and lie flat on their sides, they are very fresh. If your eggs stand on one end at the bottom, they are a few weeks old, but still fine to eat. If your eggs float to the surface, they are no longer fresh.
Some egg cartons have sell-by dates on them, while others have expiration dates. Neither should be regarded as an indication of when the eggs are no longer safe to use. Both the Food and Drug Administration and Egg Safety Center agree that eggs are usually good for several weeks past the stamped date.
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.
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.
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.
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.