I’m a nutritionist and I’ll explain the mistake you should never make when preparing hard-boiled eggs

It may happen, when opening a hard-boiled egg, that you find a greenish area around the yolk and wonder if it is normal. Many underestimate it, considering it something of little importance, but in reality that color indicates that something in the cooking didn’t go as it should.

Doctor Silvia Petruzzelli, Nutritional Biologist, explains it well in a post on Facebook, specifying that it is not simply an aesthetic problem, that edge in fact signals the formation of iron sulphide, a substance that is best avoided.

How does the greenish halo form? It all starts from natural chemical reactions between the components of the egg:

How to cook hard-boiled eggs to avoid the formation of iron sulfide

Dr. Petruzzelli’s practical advice is simple but effective:

So, the mistake you should never make when preparing hard-boiled eggs is to let them cook for too long without control or not to cool them immediately. With the right technique, you can enjoy perfect eggs.

Because it is better to avoid the formation of iron sulfide

The formation of iron sulphide, which occurs when the egg white and yolk reach high temperatures for a prolonged period, does not make the egg dangerous – this substance can only be harmful in high quantities – but it is still an indication of incorrect cooking and can lead to some unwanted effects:

In practice, avoiding the greenish edge means obtaining eggs that are more pleasant to eat, more digestible and also more inviting in appearance.