Why do boiling eggs crack

But this method takes longer and gives you less control over the cooking time. How long it takes the water to reach boiling depends on the size and shape of your pot, among other things.

Starting with boiling water offers more control over timing but this may cook the whites into a rubbery state. And it has another disadvantage: The egg is more likely to crack because the air in the egg has less time to escape as the egg heats up. New egg or old? The age of your egg affects your end result. Very fresh eggs tend to be more difficult to peel. Cold-water plunge? The longer you cook the egg, the more likely you are to end up with a rubbery white and a green yolk.

Why does the yolk turn green? The green-gray color and the whiff of sulfur smell that often accompanies it comes from the reaction of iron in the egg yolk and sulfur in the egg white. When heated, the two can combine to make green-gray ferrous sulfide and hydrogen sulfide gas.

To avoid getting a green yolk, cook your eggs just long enough to reach the desired doneness—no more. And quickly plunge the cooked eggs into cold water to stop the cooking process and minimize the iron-sulfur reaction. Place the eggs in cold water and bring to a boil. Reduce the pressure of the air pocket as it expands. Some people poke a small hole in the bottom of the egg to allow the air to escape when it expands 2. Avoid cooking the eggs at a hard rolling boil. Add some salt to the water.

A bit of vinegar or lemon juice in the water will have the same effect. First, place the eggs in a saucepan. Add enough water so that there is an inch of water covering the eggs. Let the eggs sit in the hot water for 25 minutes, then plunge them in ice water. If the shell appears dry and undamaged, crack the egg into a clean, white bowl or plate before using. Look for any pink, blue, green or black discoloration in the yolk or whites, as this may indicate bacterial growth 3, 4.

Put the pot over high heat and bring to a boil. Once the water is at a rolling boil, turn off the heat and cover the pot with the lid. Bacteria can enter eggs through cracks in the shell. Never purchase cracked eggs. The white of a freshly laid egg has a pH between 7. After the protective coat is washed off the egg shell the egg becomes porous and begins to absorb air and loose some carbon dioxide contained in the albumen.

This reduces the acidity of the egg which causes after several days in the refrigerator the pH to increase to around 9. At higher pH the inner membrane does not stick as much to the albumen so the shell peels off easier.

In addition, as the egg gets older it will shrink and the air space between the egg shell and the membrane will get larger. Research shows that the reduced acidity helps with peeling.

The tradeoff, however, is that in older eggs the yolk tends to move further from being centered. This happens because the white gets thinner and is less able to hold the yolk in place. The best compromise is to use eggs that have been stored on their sides in the refrigerator for 7 to 10 days. What is the best way to peel a boiled egg so the egg white does not stick to the shell?

Here are several responses, although all bets are off for eggs only a couple days old. Cover eggs in cold water and let set for a couple of minutes. Leave water and eggs in pan and peel, using water to rinse away excess shells. Peel the egg under cold running water starting with rounded top where the air pouch is. The bottom, rounded end of an egg contains a small air bubble.

As the egg heats up, the air inside the bubble expands. As the hot air pushes outwards, it puts pressure onto the shell, making it crack.

You can prevent this by making a pin-pick in the bottom rounded end of the egg. This will let the expanding air escape. You can also prevent cracking by letting eggs come to room temperature before cooking them.

Add the eggs to tap water and then apply the heat. Do not add eggs directly into boiling water. Adding either salt or vinegar in the water will not prevent the egg from cracking but will congeal the white if it starts to leak out of the shell from a small crack, making the cracked egg, still pleasing to look at.