Hard-boiled eggs often develop a green ring around the yolk. While “it’s completely safe to eat,” the color isn’t very appetizing.
The cause is simple: when eggs are overcooked, “the iron in the yolk reacts with the sulfur in the white, forming a thin layer of iron sulfide.”
To avoid this, control cooking time. Bring water to a boil, add the eggs, then reduce to a simmer for 9–12 minutes, depending on egg size. Overboiling is what creates the discoloration.
Cooling is just as important. “Transfer eggs immediately to an ice bath or cold water.” This stops cooking, prevents the green ring, and makes peeling easier.
For best results, use slightly older eggs, which peel more easily, and refrigerate boiled eggs if not eaten right away. With a little timing and cooling, you’ll get hard-boiled eggs that are tender, flavorful, and free of green rings.
