Once eggs are out of the carton and in the rack on the fridge door, how do we remember how long they've been there? How long do they last once we've purchased them, anyway? I've been thinking about this since I read in one of my vintage cookbooks that a "good egg" will sink and a "bad egg" will float. I wanted to know more...
How to test an egg for freshness
Place an egg in a cup with enough water to cover it completely.
- If the egg sinks to the bottom and lies on its side, it's very fresh.
- If it stands upright on the bottom, it's still safe, but should be eaten soon.
- If it floats, it should be discarded.
(Once an egg is washed, its protective coating has been removed and it should be cooked to prevent contamination).
The science behind the test
I learned that an egg is porous. Its freshness and shelf life are determined by the amount of air that has entered the shell. So an egg that floats has taken on quite a bit of air and is no longer good to eat.
What, exactly, is wrong with a "bad egg"?
A pasteurized egg stored in your refrigerator should not grow bacteria. But it will lose moisture as it takes on air and dry out, rendering it "the incredible, inedible egg".
What's going on between "very fresh" and "should be eaten soon"?
Apparently, the freshest egg has a well-shaped and properly placed yolk. So only the freshest eggs should be poached or boiled for deviled eggs, while those that have aged a bit would be better scrambled or mixed into a recipe.
The life cycle of a store-bought egg
According to the USDA, farmers must deliver their eggs to stores within 30 days after they're laid. The grocery store must sell them within 30 days, so this is the date usually marked on the carton as the "SELL BY" date. It is recommended that you use them within five weeks of that date.
So the good news is that our eggs have greater longevity than I thought. The bad news, I guess, is that they could be two months old before we even purchase them!
More posts about eggs:
Devilishly Delicious - my favorite deviled egg recipes
Egg Yolk Cookie Paint - cookie decorating fun
Easter Eggs - decorating eggs with shrink wrappers
What's your favorite way with eggs?