Bad eggs on the inside PLUS to wash or not?

Even if the outside of an egg looks perfect, there can be little horrors waiting for you inside.

All those years of cracking open perfect supermarket eggs might have made you think all eggs are like that.

But it’s actually careful management which gets you perfection every time. Eggs sold in large commercial quantities go through a thorough checking process: any eggs with obvious damage or imperfect shells are removed. They then pass over a bright ‘candling’ light which highlights finer cracks and any internal defects. The eggs are then packaged by weight.

For those of us gathering eggs from our own hens, the best advice I can give you is to always crack an egg into a bowl, just in case the contents are not what you’re expecting. That way, you don’t end up with something nasty all through your half-prepared cake mix or omelette.

While many of the unusual findings within an egg are ok to eat, they don’t tend to look appetising. Every now and then, it will be something really disgusting. The worst is an egg gone bad, one that has been invaded by bacteria, creating an explosive green, grey gassy… mixture. There is often nothing on the outside to give you warning.

This is why we advise doing a ‘float’ test (see last month’s issue) too. A freshly-laid, still warm egg white (albumen) may have a slightly cloudy appearance. This is caused by the CO2 within the egg, which soon dissipates through the pores of the shell once the egg cools down.

Any other colours other than this indicate a problem: • yellow indicates an egg is getting old; • green can indicate an excess of riboflavin in the diet; • green can also indicate a bird has eaten a weed called shepherd’s purse; • dark green indicates a bird has eaten

Shell colour

A commercial feed often contains enough Vitamin D3 for birds that would normally be kept inside a commercial shed and not see sunlight.

But this can cause a condition in freerange hens, especially in high sunlight areas like Marlborough. The extra vitamin D3 causes brown eggs to get paler and paler. Excess calcium can also cause brown eggs to become paler.

Shell colour is a breed characteristic and is inherited: • light breeds like Leghorns and Minorcas tend to lay white eggs; • heavy breeds like Rhode Island Reds lay brown eggs; • many breeds lay beige or light brown eggs.

Commercial hybrids like Shaver Browns and Hyline Browns both lay very brown eggs. They are the result of a two-way parent cross which combines the genes from a heavy breed and a light breed in one bird. This emphasises the genes for light body size and high egg numbers of a small breed (eg, Mediterranean breeds), and the egg colour and shell strength of the heavy breeds (eg, Rhode Island Reds).

The ‘brownness’ of an egg is a colour laid over a basic white egg. If you pick up a hot, wet, freshly-laid brown egg, the colour may actually smudge where you touch it.

The saying that birds with white ear lobes lay white eggs and birds with red ear lobes lay brown eggs is almost true, but there are a few exceptions: • Silkies have turquoise blue or dark red ear lobes and lay creamy white eggs; • Sebright bantams have red ear lobes and lay white eggs; • Araucanas have red ear lobes and lay blue or olive green eggs.

The colour of an Araucana egg is a genetic anomaly, connected with bilirubin levels in the liver which contribute to the distinctive blue-green hue. An olive egg is a basic blue with the gene for brown ‘paint’ overlaying the blue, just as the egg is ready to be laid.

It is a strong genetic trait, so a crossbred hen that lays eggs with a green or blue tinge has Araucana in it somewhere.

There are good reasons why eggs should not be washed or even wiped with a damp cloth. Eggs are laid with a cuticle which covers the pores of the shell with a thin film, also often called a ‘bloom’.

The shell is composed of calcium carbonate crystals, forming a surface with up to 8000 microscopic pores. Some of these pores open on the surface, while others do not go all the way through the shell. The pores allow the transfer of oxygen, carbon dioxide and moisture to the developing chick.

But this also allows an entrance for pathogens, notably E. coli and salmonella bacteria.

The shell of an egg is covered with a cuticle just prior to the egg being laid. This cuticle is a thin protein-like mucous deposit which blocks up these openings. As the cuticle dries it forms a layer which prevents bacteria getting access through into the egg itself. Dirty nests, especially those soiled with faecal matter from birds which sleep in their laying area, mean bacteria can gain access through these pores before the egg dries out in the hour or so after it is laid.

Once the egg is cool and the pores are sealed, the risk of contamination drops. But if you then wash the eggs to remove any soiling, the cuticle is also removed and any bacteria in the dissolved faecal material then gets absorbed through the pores and will continue to multiply within the egg, especially when storage temperatures are warmer.

Wiping an egg with a damp cloth can be just as bad, although the number of bacteria from the dirty water is reduced.

Dry scraping or wire wool removes the cuticle but does not add moisture, so the risk of bacteria ingress is reduced.

Some countries, like the USA, insist that commercially-produced eggs must be washed at a set temperature, using approved sanitisers, and must be kept in a fridge. Most European countries do not approve washed eggs as top grade, and Ireland’s Food Safety laws insist washed eggs receive a B grade and may not be retailed as fresh eggs.

If you have to wash an egg, then it should be done in warm water, at least 32°C, not cold. Using cooler or cold water forms a vacuum