What causes the grey ring that is sometimes found around the yolk of hard-cooked eggs?
This discolouration is the result of a reaction between the sulfur and iron naturally found in eggs. It occurs when eggs are overcooked, or when there is a high level of iron in the cooking water. Although the colour isn’t very attractive, the eggs are safe to eat and still nutritious and flavourful. An appropriate cooking time and rapid cooling of the eggs after they are cooked will prevent the formation of this grey ring. Check out our recommended method for hard-cooking (hard-boiling) eggs.
