When you encounter a rotten egg, there's nothing subtle about recognizing it—you know it immediately. Smelling a bad egg is "an awful, but worthwhile lesson to learn, two batches of cookie dough later," says harrie. "I can still smell the bad egg if I think about it—plus the egg comes out of the shell in a gross, gray, loose liquid, and it's just disgusting."
But eggs don't go bad for a really, really long time. "I date the cartons and have used eggs that were two MONTHS old and are still perfectly fine. And I mean perfectly," says Nyleve. "My local chicken farmer told me before she started selling them, she used to keep the eggs in her basement covered with straw all winter long," says coll.
How can you tell the difference between a fresh egg and an old egg? Stick them in a bowl of water to see what happens, says Nyleve. "As eggs age and the contents of the shell lose moisture, the air space at the big end of the egg enlarges. A very fresh egg will basically just sink. A little older and it stands on its pointy end. Much older and it will float. This tells you nothing much—just that it is older. It doesn't necessarily tell you if the egg is rotten or not."
Some opacity or cloudy coloring in the white of the egg, with no smell, is a strong indicator of superfreshness, says morwen. "Next time you see it, be sure to use some for poached eggs that day or the next to be able to take advantage of that wonderful freshness!" says weezycom.