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Egg quality

This fact sheet explains what to look for when assessing the quality of eggs, how to best store them to maintain freshness, and simple steps to avoid the risk of food poisoning from egg dishes.

  • 18 March 2010 | Updated 14 October 2011

Egg quality: what to look for

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If you look closely at an egg shell held against a bright light in a dark room you will be able to see an air gap, usually at the blunt end of the egg.

In a fresh egg this air cell is quite small but as the egg ages, water is lost from the 17 000 pores in the egg and the air cell gets larger.

Also you can see a large moving shadow in the egg which is the yolk floating about in the white.

In fresh eggs the yolk is small and in the centre of the egg. If you hard boil an old egg, you can quite clearly see the air cell indentation in the top of the egg. 

A quick test for freshness is to check if the raw egg in the shell sinks in a basin of water.

When you cut along this hard boiled egg lengthways you will see that the yolk has moved off centre.

A quick test for freshness is to check if the raw egg in the shell sinks in a basin of water.

Fresh eggs stay at the bottom of the bowl while stale eggs stand on end or float because of the large air cell.

Other factors such as a weak shell and fine cracks may also cause the egg to float.

Good quality, fresh eggs display certain characteristics when broken out.

The yolk is small and rounded and stands high in a thick, gel-like egg white which tends to stay compact rather than spread out over a wide area.

As eggs age, the yolk becomes larger and flatter, until it eventually breaks.

The thick egg white becomes thin and runny. By this time the egg will also have developed a stale odour and flavour.