What is that gray ring around the yolk of your hard-boiled egg, and is it dangerous?
A meatball sandwich with egg, a Niçoise salad, homemade egg salad or simply straight from the shell; hard-boiled eggs for the win! Do you also feel invincible when you take such a perfectly hard-boiled egg out of the pan? Then you probably recognize the disappointment when there’s a nasty gray ring around the yolk. Sometimes it even looks blue or greenish. Yuck! Right? Or are we exaggerating and can we simply eat it?
Let’s reassure you right away: that gray ring is nothing scary or dangerous. Even if it may not look very appetizing, you really don’t have to throw the egg straight into the trash. But it is interesting to know how that ring forms. And how you can prevent it if you want to show off your beautiful eggs from now on.
A chemical process
The gray ring around your egg yolk is caused by a chemical reaction in the egg. The substances involved are sulfur and iron. Sulfur is found in the egg white, while iron is found in the yolk. Here’s how it works: if you cook your egg in water hotter than 70 degrees Celsius, the sulfur produces hydrogen sulfide. When this substance comes into contact with iron, iron sulfide is formed. And that final substance is precisely what causes the grayish ring around the yolk. So it’s a reaction to a reaction caused by heating your egg white. Still with us?
Completely s-egg-ure
Iron sulfide is completely safe. You can eat it without putting your health at risk. It just doesn’t look very appetizing, that gray ring. So how do you prevent it? There are three tricks.
How to prevent that gray ring
First: cook your eggs for a shorter time. The longer the egg cooks, the greater the chance of a gray ring. Take it out of the pan a little earlier and you’ll probably have a beautiful egg. Second: cook your eggs at a lower temperature. You don’t need to reach boiling point. The research team from Keuringsdienst van Waarde, for example, says that 85 degrees Celsius is also a perfectly good temperature for cooking your egg. And finally: shock your eggs. This stops the cooking process and also prevents the formation of a gray ring. If you were already doing this, try ice water. To give them a truly e-gg-streme shock.
This also immediately explains why you don’t get hard-boiled eggs with a gray ring every single time. You probably just used better cooking techniques on all those other occasions.
Also read:
- Why are there fewer and fewer brown eggs in supermarkets?
- Never get eggshells in your pan again: this hack for cracking eggs is genius
- Why you should eat white eggs
Source: Keuringsdienst van Waarde/KRO-NCRV
