When hard-boiled eggs develop a green ring around the yolk, it usually looks unappetizing, but it’s generally harmless. The green or grayish layer forms due to a chemical reaction between iron in the yolk and sulfur in the egg white. This happens mostly when eggs are overcooked or cooked at too high a temperature.
Why It Happens:
Iron + Sulfur Reaction – The yolk contains iron, and the egg white contains sulfur. When heated too long, these two elements combine to form iron sulfide, which appears as a greenish ring.
Overcooking – Boiling eggs for more than 10–12 minutes increases the chance of this reaction.
Storage Factors – Eggs that are older or stored at room temperature before cooking can also be more prone to this discoloration.
Safety:
Read more on the next page
