It is always handy to have hard-boiled eggs on hand since they are so versatile. Indeed, they are not only delicious as is, but also great in sandwiches, to dress up salads, and are the basis of devil-filled egg recipes.
But what is more annoying than having hard-boiled eggs with a green ring around the yolk? It just ruins everything! Luckily, once you boil the eggs properly, you won't ever get that ring anymore!
The grayish-green ring is the result of a reaction between iron, present in the yolk, and sulfur, present in the protein of egg white. During cooking, the proteins, which are normally coiled on themselves, unwind and release sulfur.
This sulfur is attracted to the center of the egg, where the pressure is less. Along the way, it comes into contact with iron on the surface of the yolk and produces iron sulfide, a greenish-colored compound. The longer the egg is exposed to high heat, the more iron sulphide will form.
In order to slow down the rate of the reaction between sulfur and iron, the eggs should be cooked using gentle heat. The recommended technique is to cover the eggs with cold water, bring to a boil, cover and ... remove from the heat. Let the eggs sit off the heat for 15 to 20 minutes, depending on their size. Then run under cold water and peel!
In short; the discoloration, is due to the eggs being cooked for too long.
Do you enjoy hard-boiled eggs? What is your favourite egg recipe?