Simply Science: Is your egg fresh or ready for the trash?

GOLDEN VALLEY, Minn. - No matter how long they've been in the fridge, all eggs look the same from the outside. The carton's expiration date may say your eggs are past their prime, but a quick science experiment could reveal otherwise.

Put the egg in a bowl of water.

  • If it sinks to the bottom the egg is fresh.
  • If it stands upright on the bottom, it's still good, but may go bad soon.
  • And if it floats, the egg is no good. None of the eggs in our experiment were floaters.

The reason why lies with thousands of tiny pores that speckle the egg's shell.

Microbiologist andKitchen Pantry Scientist, Liz Heinecke says, "The shell is porous. The egg white loses carbon dioxide. It absorbs air, and as it sits that air pocket gets bigger."

The air pocket that forms is what makes the aging egg float.

Of course many of us will be hard boiling eggs for Easter weekend. If you're using eggs right from the hen, strong protein structure clings to the shell tightly, but those proteins start to lose structure quickly.

Heinecke says, "As the egg sits, even for a couple of days, the egg becomes more acidic and these denatured proteins don't cling as tightly to the membranes next to the shell so, it's easier to peel."

If you find your yolk isn't a bright yellow shade next time plunge them in ice water immediately after boiling them.

"If you don't stop the cooking process there's a chemical reaction that will actually turn the yolks a bluish green. And this reaction is between the iron in the yolks and some of the sulfur containing proteins in the whites," she explains.

Don't worry, you can still eat them. The discoloration is harmless. They still taste eggcellent! See more egg science experiments at

There are literally thousands of recipes for hard-boiled eggs. Each one tried and true.

Boiled egg recipe
Lance Kapps, Executive Chef ofThe Saint Paul Hotel has given us "his" recipe for the perfect hard-boiled egg this Easter:

Take desired number of eggs from the refrigerator and let the eggs rest at room temperature for about 25 minutes. Place eggs in cold water to completely immerse eggs to a depth of 1 inch. Do not over crowd the pan. Only put one layer of eggs in the bottom of the pan, do not place eggs on top of one another.

Bring the water to a boil, reduce the heat, and let eggs simmer for 15 minutes. For extra large eggs simmer eggs for 17 minutes. Set timer for 15 minutes once you turn the egg down to a simmer and turn heat off when timer goes off.

Remove eggs from the hot water and place in an ice bath to stop the eggs from cooking. The ice bath should cover the eggs with cold water by an inch or two and ice cubes should cover the water of the container being used to chill the eggs. Be careful to not drop the ice on the eggs this can crack the shells.

Let eggs rest in the chilled water for 25 minutes to completely chill.

To peel hard-boiled eggs, tap the egg gently all over and crack shell. Too loosen the shell roll the egg on a flat surface. The egg should peel easily now that the shell is loose.

You can use cold running water to clean the egg shells off the hard boiled eggs.

Note: Eggs can be stored for up to one week unpeeled in the refrigerator.


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