Many solids melt as they get hotter, but eggs do not. They start as quite liquid in the fresh state and when they are heated, they go solid. This odd behaviour is a result of the effect of the heat on the proteins they contain. The strands of protein in both the egg yolk and white are folded into precise shapes, each molecule forming a minute ball called a globular protein. But when these proteins are heated, some of the interactions holding the protein molecules into their precise globular shapes are broken and the molecules begin to unravel. This allows the separate protein chains to become entangled with one another and new and stronger interactions can form, which form a solid three-dimensional network of protein molecules, leading to a soft-boiled or eventually a hard-boiled egg.
China produces about 160 billion per year – the largest number in the world - and in the USA, more than 65 billion eggs are produced per year by about 260 million hens.
In the nineteenth century British collectors, eager to obtain the eggs of rare birds, wiped out entire species such as the osprey, sea eagle and goshawk.
The green-grey colour surrounding the yolk of a hard boiled egg (and the rotten smell of sulphur that often accompanies it) comes from the reaction of iron in the egg yolk and sulphur in the egg white. When heated, the two combine to make green-grey sulphide and hydrogen sulphide gas. To avoid getting a green yolk, cook your eggs just long enough to reach the desired doneness and quickly plunge the cooked eggs into cold water to stop the cooking process and minimize the iron-sulphur reaction.
The word “egg” is commonly thought to come from an Indo European word meaning bird. And “yolk” comes from Old English and Greek and means “yellow”.
December 3rd 1988 was Black Saturday for eggs when Edwina Currie, then Junior Health Minister, stated during an impromptu interview for ITN, that “Most of the egg production in this country, sadly, is now infected with salmonella”.
Next time you’re boiling eggs, try putting lemon juice or vinegar into the water. Make a hole with a pin (you’ll need to twist it slightly) in the side of each egg. A side is better to pierce than an end. Get two small saucepans of boiling water ready. Into one of them, put a couple of teaspoons of vinegar or lemon juice to make the water slightly acidic. Lower half your pierced eggs gently into one pan, and the rest into the other. Scientists say that acid causes the protein in the egg white (albumen) to coagulate (go solid) more quickly. Does your experiment show that? Cook the eggs for about 3 minutes and then enjoy eating them!
Yolk colour tends to be thought of as important. The hen cannot make the pigments for egg yolk colour herself. But ‘free-range’ hens, able to roam around and scavenge for food have access to a wide range of plant material and the pigments from these materials colour the yolks. Although nutritionally suitable, the artificial diet fed to hens reared intensively, may not contain plant pigments. Besides, natural pigments are not very stable, so artificial agents to colour the yolks may need to be added. It’s said that maggots, coloured red for freshwater fishing, have been fed to hens (which love them – and maggots are very nutritious) and then the hens have laid eggs with crimson yolks!
Eggs contain all the essential protein, minerals and vitamins, except Vitamin C. And egg yolks are one of few foods that naturally contain Vitamin D.
Chickens have been domesticated, and laying eggs for us, for nearly five thousand years.
Eggs have been seen as an especially good food for invalids from at least the eighteenth century. Mrs Beeton gives this recipe for "egg wine". Beat an egg with a little water. Warm a glass of sherry with half a glass on water, pour it onto the egg, stir in some sugar and nutmeg’. Sounds delicious!
To make an egg stand on its end, first make a little pile of salt on a hard dry smooth surface, such as a plate. Stand the rounded end of the egg on the salt. Carefully blow the salt away from around the egg. The egg doesn‘t fall over. A few tiny cubes of salt remain under the egg and make a pedestal which supports it.
An African ostrich egg will feed up to 10 people at a time and it would take about 40 minutes to boil.
The “Lion” stamp on British eggs shows you that the egg has been produced according to a set of industry standards, such as hens being vaccinated against salmonella. As well as the red lion, there is also a ‘best-before’ date on them (21 days after laying). There is also a number which identifies the way that the hens are kept – 0 for organic, 1 for free range, 2 for barn eggs and 3 for cage eggs. This number is followed by a country code (e.g. UK) and a set of numbers which identifies the farm from which the egg originated.
A hen starts laying eggs at 19 weeks of age and, on average, lays about 259 eggs a year. As she grows older she produces larger eggs.
The largest chicken egg on record was nearly 12 oz, measuring 12 ¼” around.
The largest recorded number of yolks in one chicken egg is nine.
The record for laying the most eggs is seven in one day.
Did you know that some breeds of chickens can lay coloured eggs? Sure enough, the Ameraucana and Araucana can lay eggs colored in shades of green or blue, depending on the breed and its ancestry.