What does it mean if an egg floats in boiling water?
Old eggs float in fresh cold water because of a large air cell that forms as the egg cools after being laid. As the egg ages, air enters the egg and the air cell becomes larger and this acts as a buoyancy aid. Eggs that tilt so that the large end is up are older, and eggs that float are rotten.
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.
- As eggs age, however, they can grow different kinds of bacteria, called pseudomonas. Though pseudomonas and mold don't cause food-borne illnesses, they can make you sick to your stomach, so if you notice a change in color, odor or appearance of your eggs, play it safe and don't eat them.
- Step 1: Fill a bowl with cold water and place your eggs in the bowl. If they sink to the bottom and lay flat on their sides, they're very fresh. If they're a few weeks old but still good to eat, they'll stand on one end at the bottom of the bowl. If they float to the surface, they're no longer fresh enough to eat.
- Cover them with cool water by 1 inch. Slowly bring water to a boil over medium heat; when the water has reached a boil, cover and remove from heat. Let sit 12 minutes. Transfer eggs to a colander; place under cool running water to stop the cooking.
Eggs have an air cell that becomes larger as the egg ages and acts as a buoyancy aid. An egg can float in water when its air cell has enlarged sufficiently to keep it buoyant. This means the egg is older, but it may be perfectly safe to use.
- As salt concentration rises, density increases, because the salt molecules can occupy spaces between the water molecules. Denser water sinks beneath water that is less dense. As denser water sinks, water must rise somewhere to replace it. You can see for yourself if water can float on water.
- If you throw your eggs out once the date on the carton has passed, you may be wasting perfectly good eggs. With proper storage, eggs can last for at least 3–5 weeks in the fridge and about a year in the freezer. The longer an egg is stored, the more its quality declines, making it less springy and more runny.
- Refrigerated raw shell eggs will keep without significant quality loss for about 4 to 5 weeks beyond the sell date or about 3 weeks after you bring them home. A general rule to follow is that any egg that looks or smells odd should NOT be used. Just crack each egg in a small bowl, smell it – your nose will tell you!
Updated: 18th November 2019