Have you ever questioned yourself what is the green ring around the yolk of hard boiled eggs? Surprisingly, it occurs because of your fault and it should not happen.
A greenish, blackish ring around the yolk of an egg is a sign of an improper cooking. It is evidence that the egg was cooked for a long period. But this does not mean the egg is not edible and it tastes bad.
The resulted color or a longer cooking is formation of iron sulfide where the yolk and white parts of the egg encounter. The iron from the yolk responds with hydrogen sulfide from the white. It is not dangerous, but it should not occur.
How to avoid the discoloration:
You just need to learn what the right amount of time for cooking is.
Cook your eggs in a large saucepan, enough to hold the eggs in a single layer.
Cover the eggs with water and let it boil. Put a lid over the saucepan.
The eggs need to sit in the boiled water for 15 minutes.
Next, apply cold water over the eggs to stop cooking any further.
That’s all. Now you can prepare beautiful yellow yolks.