Boiling chicken eggs can often fill the kitchen with a disgusting aroma. Following the correct cooking techniques will prevent this smell. Properly boiling an egg will also produce a pleasantly colored yolk and an easy-to-peel shell.
Chicken eggs produce a sulfurous smell when they are boiled for too long. Overcooking the egg coagulates the egg's protein and creates an excess of hydrogen sulfide in the whites of the egg. The sulfide reacts with the iron in the yolk. This leads to an unpleasant odor and a green sulfur coat on the yolk.
A medium-sized chicken egg that is cooked for 11 to 12 minutes has less chance of producing a sulfurous smell and a green yolk. Also, plunging the boiled egg in ice water immediately after removing it from the pot will stop the internal cooking process, reduce the smell and keep the yolk golden yellow. The egg whites and yolk will slightly shrink in size when placed in cold water, making it easier to peel the shell.
An overcooked egg is not a rotten egg. The potent smell and green yolk produced from boiling an egg too long are harmless. The egg is still perfectly fine to eat.
The boiling time should reflect the size of the egg. Large eggs can be boiled up to 15 minutes, and extra-large eggs can be boiled up to 18 minutes.
Cooking too many eggs in one pot can have an adverse effect. All eggs should be fully submerged in the water while cooking. The eggs should not be stacked on top of each other. One inch of water above all eggs is an adequate amount of water.
If placed in rapidly boiling water, the whites of the eggs will overcook before the yolks harden. The heat can be turned down to a simmer to prevent overcooking the eggs. Another method is to bring the water to a boil, remove it from the heat entirely and allow the eggs to cook in the cooling water.
Hard-boiling an egg removes its bloom, a natural protective coating produced by the hen. The bloom prevents bacteria and other contaminants from permeating the pores in the shell. Thus, hard-boiled eggs should be kept refrigerated and eaten within a week after boiling.
Do not boil rotten eggs. A chicken egg that is rotten will float to the top of a pot of water. A fresh egg will sink. Fresh eggs have more moisture than rotten eggs. As the egg ages the moisture leaves the permeable shell, creating a small air pocket in its base. This air pocket makes a rotten egg float.