When eggs are subjected to excessive heat, the sulfur
and hydrogen in the egg white combine to form hydrogen-sulfide
gas. When the gas reacts with iron present in the egg
yolk, a gray-green film forms where the white and the
yolk contact each other. While it’s not pretty,
it’s harmless.
We don’t know of any way to remove it, but we do
know how to prevent it from forming in the first place.
Prolonged cooking at excessive heat causes this problem.
In fact, the term “hard-boiled egg” is misleading:
You should never hard-boil an egg.).
Instead,
put the egg in water and bring the water to a boil. Turn
off the element (on an electric stove) or turn the heat
way down (on a gas stove) and let the egg sit for twenty
minutes. Then plunge it into cold water to stop the cooking
process and make it easier to peel.
Here’s to gentle temperatures and no more green
rings!
