Boiled chicken eggs are a nutritious and familiar dish in many families. However, sometimes when cutting a boiled egg in half, we notice a mysterious green layer surrounding the yolk. This green ring often makes people worry that the egg has gone bad and could cause illness if eaten, so they throw it away. So, what is the green ring around a boiled egg yolk, why does it appear, and is it harmful to eat?

In fact, this green circle appears due to the way the egg is boiled, not because the egg itself is spoiled. It happens when the egg is boiled for too long.

The reason is that the egg white contains hydrogen sulfide (H₂S), while the yolk contains iron. Under prolonged heat, these two substances react with each other to form iron sulfide (FeS), which has a greenish-black color.

Is the green ring around the yolk harmful?

Basically, this green ring does not affect the taste of the egg or the eater’s health. It only makes the boiled egg look less appealing when cut open.

How to boil eggs without the green ring?

To avoid having the green ring, you should not overboil the eggs. The proper way to boil eggs is as follows:

• Place the eggs in a pot, add water, and bring to a boil.

• Once the water is boiling, continue cooking. The boiling time depends on whether you prefer soft-boiled or hard-boiled eggs. You can refer to the chart below for the exact number of minutes.

After boiling, place the eggs in cold water. Once they have cooled slightly, peel and enjoy.

Note: Do not remove the lid while boiling the eggs.