If your hard-boiled eggs have a green or gray-green ring around the yolk, it usually means the eggs were overcooked or cooked for too long at a high temperature.
What causes the green ring?
Eggs naturally contain sulfur in the whites and iron in the yolks. During prolonged cooking, these compounds can react where the egg white meets the yolk, producing ferrous sulfide, which gives the familiar greenish-gray ring.
It does not mean the egg is rotten and, by itself, does not indicate that the egg has lost its nutritional value or become poisonous.
Does it mean the egg is safe to eat?
Usually, yes. If the egg:
-
was cooked properly,
-
was refrigerated promptly,
-
hasn’t been stored for an excessive amount of time, and
-
doesn’t have an unusual rotten smell or other signs of spoilage,
the green ring itself isn’t a reason to throw it away
