You know, when you crack open a hard-boiled egg, the yolk is green and looks back at you. Many people have been confused by this food mystery, but the answer lies in the simple science of cooking.
Too much heat causes the colour to change from sunny yellow to green. If you cook eggs for too long or at too high of a temperature, sulphur chemicals in the egg white react with iron in the yolk to make ferrous sulphide. This is what gives eggs their green colour.
Not only hard-boiled eggs can go green because of this chemical reaction, but so can mixed eggs and omelettes if they are cooked too quickly.
The good news is that green yolks are safe to eat. The strange colour doesn’t mean the food is going bad or is poisonous.
Care must be taken when cooking eggs so that the whites don’t turn green:
Time and gentle heat are very important. Do not cook the eggs for too long, and put them in an ice bath after boiling to stop the cooking.
Eggs will stay bright yellow longer if you cook them at reasonable temperatures.
So, what colour should the yolk be? An egg is fully cooked when it has a rich, sunny yellow colour.
Don’t worry if you end up with eggs that have green yolks. Work your magic! Mix them together and serve with avocado toast. The green will mix in, giving it a unique and tasty twist.
To sum up, the green egg yolk effect is a safe but interesting result of cooking chemistry. We can always have perfectly cooked eggs if we understand the science behind it and change the way we cook.
