Why Hard-Boiled Eggs Get a Green Ring (and How to Stop It)
You crack open a hard-boiled egg, slice it in half, and there it is: a dull green ring circling the yolk. It looks a little alarming, and plenty of…
What Actually Causes the Green Ring
The greenish ring is the result of a simple chemical reaction that happens when eggs are cooked for too long or at too high a temperature.
Here is what is going on inside the shell:
- The white contains sulfur compounds, while the yolk is rich in iron.
- When an egg overcooks, the sulfur in the white reacts with the iron in the yolk.
- Together they form a thin layer of iron sulfide right where the white meets the yolk.
- That compound is what shows up as a gray-green ring.
It is completely safe to eat and does not change the flavor in any meaningful way. It is simply not very pretty on the plate, and it usually signals that the egg was cooked a bit longer than it needed to be.