Simply fill a bowl with cold tap water and place your eggs in it. 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.
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.
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.
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.
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.
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).
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.
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.
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.
Adding salt to the water increases the density of the solution because the salt increases the mass without changing the volume very much. When enough salt is added to the water, the saltwater solution's density becomes higher than the egg's, so the egg will then float!
Place an egg in a bowl of water. Older eggs will float because a large pocket of air forms in the base, but fresh eggs will sink. This is one of the simplest ways to test for freshness. An egg will immediately smell bad if it is off.
Hard-boiled eggs, peeled or unpeeled, are safe to eat up to seven days or one full week after they were cooked. To make sure they stay fresh, allow the cooked eggs cool a bit, and then store them in a sealed container in the refrigerator.
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.
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.
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.
While it is ideal to eat eggs before this date has passed, they are often still be safe to eat after this date, but its quality may have decreased. For example, you might notice changes in colour, flavour or texture if you choose to eat eggs after the best before date.
The bottom line: Eggs typically last three to five weeks in the fridge (even if beyond their sell-by date). To confirm an egg is safe to eat, check it for any changes in appearance or smell.
Always purchase eggs before the Sell-By or EXP (expiration) date on the carton. After the eggs reach home, they may be refrigerated 3 to 5 weeks from the date they are placed in the refrigerator. The Sell-By date will usually expire during that length of time, but the eggs are perfectly safe to use.
The Shelf Life of Fresh Eggs
This coating helps to keep air and bacteria out of the egg, resulting in an egg that will last longer. 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.
If that's the case, then why are eggs not stored in fridges at the supermarket? Well, there's a simple explanation for that. It's apparently because store temperatures are kept below 20ºC, so refrigeration is unnecessary. 'This also prevents significant temperature fluctuations.