You must have encountered boiled eggs yolk grey at least once. Upon cutting, you will see a grey-green ring on the yolk. But what does it mean? Is it dangerous to eat? Does it affect the taste? Or maybe alter the nutrients in the egg? Let’s find out more about what causes yolks to have the grey ring and if you can do something about it.


What Causes Boiled Eggs Yolk Grey

The grey coloration is a compound called ferrous sulfide. This compound is the result of heating iron and sulfur. As you know, egg yolk is high in iron, while the whites have sulfur. The oxidation process when you boil an egg creates ferrous sulfide.

Despite the name and how it looks, this grey yolk is safe to eat. The difference in thickness only means the eggs have different sulfur and iron content. As well as telling you how long you have overcooked the egg.


Several Ways To Avoid Grey Yolk

If you dislike seeing the grey layer on your egg, here are several things to do to avoid seeing the result.


  • Time Your Boiling Point
    It’s a common misconception to think that a timer is only necessary when you only want soft-boiled eggs. You also need to time your hard-boiled eggs perfectly. This will prevent the sulfur and iron to heat up and oxide and create the greenish-grey layer.


  • Store Your Egg Properly
    Even though you have timed your eggs perfectly, you may still see the thin grey layer outside of the yolk. It means that you are boiling older eggs with a higher sulfur content.

Naturally, eggs already have sulfur content. But the content increase as they age. Sulfur is the one responsible for the smell of a rotten egg. Therefore, you need to know how to store them properly.

The rule of thumb is, storing eggs at room temperature for a day ages them faster than storing them for a week in a refrigerator.


Some Egg-citing Trivia

Do you think you know about eggs? There are numerous trivia about eggs that you may not know.


  • Different Egg Color Doesn’t Affect Its Taste
    You may find blue and even pink eggs. These eggs are natural eggs without any artificial enhancement. What makes their coloration unique is the different breeds of chicken that lay them. Some farmers claim they can tell the egg color from the chicken’s ears.  As for their nutritional values, they are all just like your regular brown eggs.


  • Egg Yolk is a Single Cell
    Yes, egg yolk consists of only one cell. As one of the largest cells in the world, egg yolk is also high in nutrients, primarily protein and iron.


One true and tested tip to have the perfect hard-boiled eggs is to put them in a bowl of ice to stop the heating process. One last tip on boiling eggs is to put the eggs in a bowl of ice to stop the heating process. This will prevent you from seeing boiled eggs yolk grey ever again.


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