Why do hard-boiled eggs have a weird green ring around the yolk?

The greenish ring that sometimes forms around the yolk of a hard-boiled egg is caused by a chemical reaction between sulfur in the egg white and iron in the yolk. This reaction typically occurs when eggs are overcooked.

When eggs are boiled too long or at too high of a temperature, the sulfur in the egg white reacts with the iron in the yolk to form iron sulfide, which has a greenish-gray color. The longer the eggs are cooked, the more likely this reaction is to happen, especially if the eggs are cooked at a high temperature for a prolonged period.

To prevent the green ring, you can try:

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1. Avoiding overcooking: Cook the eggs for the right amount of time (usually about 9-12 minutes for hard-boiled eggs, depending on the size).
2. Cooling quickly: After boiling, place the eggs in ice-cold water or run cold water over them to stop the cooking process.
3. Cooking at a lower temperature: You can also try to cook eggs at a gentler simmer rather than a full rolling boil.

These steps help prevent the conditions that cause the green ring and keep your eggs looking and tasting their best!