Jacinta Bowler
It’s Easter and I have done nothing but eat chocolate eggs for days.
But eggs are more than just an Easter treat. The science of eggs is pretty fascinating too.
How do chickens make an egg?
Let’s start with how eggs are made.
Just like humans, a hen has thousands of ova – or baby egg yolks – inside of her body from birth. When a yolk is ready, it moves along the tubes (again just like humans) to get bigger. Then the yolk enters an area called the magnum, where the white part of the egg is added.
Next the membrane skin of the egg is quickly created in an area called the isthmus. Then its shell time. The egg moves into an area called the shell gland, and the shell forms layer after layer of calcification over the next 20 hours.
After all that – out pops an egg!
Why are eggs different colour?
Because the Easter bunny paints them! Not really…
But what makes most of our eggs brown? And why are American eggs white? Plus what about the beautiful blue eggs of home grown chickens?
A study published last year in Nature Ecology & Evolution has found that birds living in cold climates and with open nests tend to have eggs with darker shells. The team suggested that the darker pigmentation allows the egg to maintain its internal temperature for longer when exposed to the sun.
But for the Australian brown eggs, verses the American white eggs, it just comes down to genetics! In Australia, commercial farms normally use Hy-Line Brown, ISA Brown and Hi-Sex Brown breeds. These breeds also have brown feathers.
America mostly uses Leghorn chickens. These hens have white feathers and white eggs!
How to tell if an egg is bad?
So with all that effort going into making a carton of eggs it’s important to know when you can eat it (or when it’s best to roll it down a hill for easter instead).
Refrigerated eggs will last anywhere from 3 to 5 weeks, and although there are lots of myths about floating in water or shaking the egg, the best way to tell if an egg is off is by cracking it and seeing if it looks, or smells off.
Most importantly, don’t use methods like water glassing to be able to extend the life of your eggs. This can cause botulism due to the pickling lime used and can potentially allow other bacteria in the eggs to grow over time and make you sick.
Can you squish an egg in your hand?
This is probably my favourite egg fact – you can’t squeeze an egg in your hand to break it (take your rings off first)!
The reason for this is the egg shape. Squeezing the egg along it’s long sides allows the pressure to spread along the whole egg.
This is particularly important for the hens themselves, because they wouldn’t want an egg to break inside the shell gland or cloaca. Of course, if you want to break an egg, all you need to do is create a blow in one spot from a sharp object, anything from a table to a ring would do it!