You may have bought some eggs and are unsure of their freshness or, if you have free range chickens like me, you might just find a cheeky nest full of eggs where your hens have been laying for a while without you knowing!
Here’s how to tell if eggs are fresh by using an egg float test.
What’s going on inside the egg?
Egg shells are porous. In nature, this allows a chick to get oxygen from the outside world during its development.
A pocket of air (called the air-sac) is situated at the broad end of an egg. This increases in size as the egg gets older. The contents of the egg shrink as moisture is slowly evaporating through the shell
Before it hatches, a chick pokes it’s beak into the air-sac to take it’s first breath of air. It then ‘pips’, making a small hole through the shell with a special ‘egg tooth’ attached to the beak so it can start breathing air from the outside world.
As an egg ages and the air-sac increases in size, the egg becomes more buoyant with the additional oxygen.
Egg float test
The egg float test is really quite simple. Take a clear jug or other container that you can see through and fill it with water. Gently place the egg in the water.
- If the egg sinks, it’s fresh.
- If the broad end of the egg lifts up from the bottom, it is a few weeks old.
- If the egg floats, it’s stale and should be discarded.
Cracking the egg open
As well as the egg water test, once you open an egg, it is also possible to tell how fresh it is. A fresh egg will have the yolk standing upright with an inner, gelatinous ring of albumen (egg white) around it. There will be a little thinner egg white spreading around that.
As an egg ages, the egg white will become more watery and the egg will spread out when you crack it on a flat surface (like a frying pan).
Some eggs will have watery whites. This can be caused by disease or by the age of the hen so it’s not always a reliable indication of the freshness of an egg. The egg water test is the best way to estimate the freshness of an egg.