Overcooked eggs, green circle around the yolk: what to do?
by Karine Lemoine
The yolk of a hard-boiled egg is surrounded by a thin greenish circle and its texture seems dry and crumbly. Is this egg flawed or even unfit for consumption?
This very common phenomenon is simply a sign of cooking that is a bit too long or too hot. It's not dangerous, but it indicates that a slight adjustment would make for a nicer hard-boiled egg.
Table of Contents
Here's why this circle appears, if the egg is still good to eat, and how to avoid it next time.
Why does the green circle appear
This greyish or greenish border results from a chemical reaction between theironpresent in the yellow and thesulphurpresent in white. Under the effect of cooking for a long time or too hot, these two elements migrate and react on the surface of the yolk, forming iron sulphide, which is responsible for this hue. Iron-rich water can also slightly accentuate the phenomenon.
Is the egg still edible?
Yes, an egg with this green circleremains completely expendable. Iron sulphide is not toxic; it only changes the appearance and, to some extent, the taste, which may become slightly more sulphurous. The texture of the yolk can also be drier and more crumbly than a yolk cooked at the right time, but this does not affect the health of the egg.
How to avoid this problem next time
The most effective is toreduce cooking timeand to immediately cool the eggs after cooking. For a classic hard-boiled egg, about 9 to 10 minutes in simmering water (not boiling to a high boil) is usually enough, depending on the size of the egg. At the end of cooking, immersing the eggs in an ice water bath immediately stops cooking and prevents the formation of the green circle, while making it easier to peel.
Our tips
►Timing the cooking process accurately
Use a timer rather than a rough estimate: a few minutes too long is enough to cause the green circle.
►Immerse the eggs in ice water as soon as they are finished cooking
This thermal shock effectively stops cooking and limits the reaction between iron and sulfur.
►Avoid boiling too violently
Boiling water cooks eggs irregularly and more quickly on the surface, increasing the risk of overcooking.
The green circle around the yolk is nothing to worry about: the egg is still edible, and a better adjusted cooking time is enough to avoid it the next time.
You can also read:How do you make an egg over medium without turning it overandAll you need to know about eggs.
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