Why do we observe a greenish ring around the yolk of hard-boiled eggs?

Have you ever cracked open a hard-boiled egg thinking you’d overcooked it because a green ring surrounded the yolk? Don’t worry: this very common phenomenon is nothing to be alarmed about. And yet, it’s always a bit disappointing when you were hoping for a perfectly golden, crisp, and appetizing yolk. Fortunately, a few simple steps are all it takes to say goodbye to that greenish border and get eggs worthy of a Parisian brunch.

Why does this green circle actually appear?

The explanation is purely natural. When an egg is cooked for too long or at too high a temperature, two elements inside—the iron in the yolk and the sulfur in the white—react together. The result: a slight greenish deposit forms around the yolk.
Good news: it’s neither dangerous nor a sign that the egg is spoiled. It’s simply the mark of overcooking!

Perfect cooking: the foolproof method

There is a simple technique, approved by all those who want perfect hard-boiled eggs, without unwanted coloring.

1. Always start with cold water

Place your eggs in a saucepan, cover them with a few centimeters of cold water and heat gently.

2. Once boiling, stop everything.

As soon as the water starts to boil vigorously, turn off the heat. This prevents the egg from overheating.

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