Mastering Cooking Methods: How to boil an egg

Boiled eggs make a great breakfast idea and are a great grab and go option. However getting to that perfectly boiled egg without bits of the egg white getting stuck to the shell can be a mission. In this week’s blog post we explore the science of boiling an egg and how to get it right every time.

What is the science behind boiling an egg?

Eggs are made up of egg white and egg yolk. Surprisingly the egg yolk has more protein than the egg white (16% vs 12%). Due to the high quantity of protein, a raw egg becomes a hard boiled egg through a process known as denaturation. Due to the heat from the boiling water, the protein bonds become disrupted and solidify. However the water doesn’t need to continue boiling in order to ensure that the eggs cook as the egg protein coagulates at 73.

Green looking eggs after boiling?

In fact if left to boil too long, eggs will become rubbery, develop a green film on the yolk of the egg and it can crack as it is boiling. The green film occurs due to a reaction between the iron ions from the egg yolk and hydrogen sulphide gas from the egg white, creating a substance called iron sulphide. It is still safe to eat. In order to prevent this from happening add salt or vinegar to the water as you boil your eggs and allow them to reach room temperature before you boil them. You can also douse your eggs in cold water after you have boiled them, as this helps to reduce iron sulphide.

How to boil eggs

1. Allow eggs to reach room temperature

2. Carefully place eggs into a pot. Add cool tap water into the pot (enough to cover surface of eggs) with a bit of salt added. Place on stove top and bring the water to a boil.

3. Once the water is boiling, remove the pot from the stove and allow the eggs to sit. For hard boiled eggs allow the eggs to sit for 12 minutes, for medium eggs allow 9 minutes and for soft eggs, allow the eggs to sit for 6 minutes.

4. Drain the eggs and pour cold water over the eggs.

*BONUS TIP* boil your eggs in advance and draw a smiley face on it with a marker so it’s easy to differentiate from the raw eggs in your fridge.

Can I only boil eggs on the stove?

No, you can actually boil eggs in the microwave and in a kettle! However these methods are not ideal and come with some risks which need to be considered before attempting. When microwaving an egg, if it is not covered with sufficient water it will explode as a steam cooker effect occurs within the shell of the egg. When using an electric kettle to boil an egg, special care has to be taken to ensure that the egg doesn’t touch the heating element or the egg will explode, making a mess inside your kettle.

Do you have a unique way you boil or shell your eggs? Leave a comment below


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