salt to the water?
Egg white solidifies more quickly in hot, salty water than it does
in fresh. So a little salt in your water can minimize the mess if
your egg springs a leak while cooking. The egg white solidifies
when it hits the salt water, sealing up the crack so that the egg
doesn’t shoot out a streamer of white.
To prick or not to prick?
Some people use a pin to make a small hole in the shell at the large
end of the egg before they put the egg in the water. At the large
end of each egg is a small air space. When you hard cook an egg,
this air heats up, expands, and escapes through pores in the shell—but
not before the egg white sets. This leaves the egg with a flattened
end. Pricking the egg provides a quick escape route for the air,
which gives you an egg with a smoothly rounded end. If you prick
an egg, watch for a jet of air shooting from the hole as the egg
Scientists disagree on the other possible benefits of pricking an
egg. Some say that piercing the eggshell with a pin lets water leak
between the shell and the egg’s internal membrane, making
for an egg that's easier to peel. Others claim that providing a
quick way out for expanding gases makes the egg less likely to crack
as it cooks, which may be particularly important for older eggs
with larger air sacs. Still others say that poking a hole in the
shell weakens it, making cracks more likely.
Hot water or cold?
people put their eggs in cold water; others heat the water to boiling,
then drop in the egg. Both methods have advantages and disadvantages.
When you drop an egg in boiling water, you heat it up quickly. When
you start with cold water, you heat it slowly. And the difference
in heating makes a difference in the cooked egg white.
An egg white is about 10% protein and 90% water. It’s the
proteins that cause the egg white to solidify when you cook it.
Egg white proteins are long chains of amino acids. In a raw egg,
these proteins are curled and folded to form a compact ball. Weak
bonds between amino acids hold the proteins in this shape—until
you turn up the heat. When heated, the weak bonds break and the
protein unfolds. Then its amino acids form weak bonds with the amino
acids of other proteins, a process called coagulation. The
resulting network of proteins captures water, making a soft, digestible
If you keep the heat turned up too high or too long when you cook
an egg, the proteins in the egg white form more and more bonds,
squeezing some of the water out of the protein network and making
the egg white rubbery.
Starting with cold water lets you heat the egg more slowly, which
keeps the whites from getting rubbery. 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?
age of your egg affects your end result. Very fresh eggs tend to
be more difficult to peel. The more acidic the egg’s contents
are, the harder the egg is to peel. As an egg ages, carbon dioxide
(which is a weak acid) leaks out through pores in the egg’s
shell, making the egg white less acidic.
you don’t plunge your egg into cold water when you take it
off the heat, it goes on cooking . . . and cooking . . . and cooking.
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.
Some people also say that the cold-water plunge makes eggs easier
How do you hard cook an egg? What’s the right answer?
experimenting with eggs in our own kitchens, we realized why people
had so many answers—and why hard cooking an egg is considered
one of the most basic of culinary skills. It’s hard to mess
up completely. Sure, some methods resulted in egg whites that were
more tender and egg yolks that were yellow without a touch of green.
But clearly there’s more than one way to cook an egg successfully.
Here is a recipe we like:
place the eggs in a saucepan. Add enough water so that there is
an inch of water covering the eggs. Heat the water until it's just
about to boil, then take the pot off the heat and cover it. Let
the eggs sit in the hot water for 25 minutes, then plunge them in