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Brown shelled eggs
© Denzil Green

An egg is an oval or round organic object, laid by a female bird, reptile, fish, or invertebrate, in which an embryo develops and grows to become the young of the species. In the world of cooking, the term is generally taken to mean bird eggs, and more specifically, chicken eggs. (Caviar is a term generally used for fish eggs.)

Eggs can be used as food items on their own, or as ingredients. When used as ingredients, they are usually used either to bind, or to help something rise.

Despite the current trend to look down on eggs produced by today's technologically controlled environments, and the nostalgia about chickens roaming backyards and laying eggs in places you had to hunt for, the city dweller has probably experienced a gain in egg freshness and quality. The eggs now have prompt gathering, inspection, and proper refrigeration from the outset.

Though people in the United Kingdom generally don't refrigerate their eggs, and supermarkets there in fact sell them on ordinary, unrefrigerated shelves, an egg degrades as much in one day as during a week under refrigeration.

The albumen of an egg thins as it ages, and becomes clearer. This thinning results in eggs that are more likely to break in the pan. As an egg ages, losing carbon dioxide and moisture through its shell, the mass inside shrinks and the small air cell at the wide end of the shell therefore increases. Thus arises an age-old housewife test: place in water, and if it sinks quickly, it is fresh; the higher it floats in the water, the older it is. This simple test no doubt would have been important when you found an egg while walking through the backyard and needed to know whether it was still good for eating or not.

The darkness of the yolk does not indicate freshness or flavour. The darkness of the yolk depends, rather, on what the birds were fed, and what breed they are.

The egg shell is porous, and speeds aging. It is best to keep eggs refrigerated in their container to help keep in the moisture, rather than in the open racks built into most North American refrigerators, especially with refrigerators being the driest place in the house. The shell colour, white or brown, has no nutritional significance. White hens produce white eggs; brown or red hens produce brown eggs

Egg acts as a thickener because as heat energy is applied, the proteins in it unfold, and come into contact with each other and bond. The higher the heat, they more tightly they cling to each other. Heated and cooked past that, the protein bonding starts to break down and release the water they had held: the water runs off, and what gets left is the rubbery protein.

Diluting eggs makes it harder for the protein molecules to coagulate together, as they are further apart. Sugar has the same effect, because its molecules coat each protein molecule making it harder for them to bond with each other. Salt and acid, on the other hand, speed coagulation.

Hard-boiled eggs are easily spun around on their sides and stopped. This is because inside a raw egg, the liquid insides build up a momentum of their own, and if you stop a spinning raw egg quickly and then release it, it may start spinning again a bit because the liquid insides will still be spinning.

Very fresh eggs, when hard boiled, are hard to peel; they are easier when they are about 3 days old (refrigerated.)

Buy brown eggs one shopping trip, and white the next. This helps you keep track of which eggs to use first.

You may have noticed that supermarket eggs are packed in their cartons with the larger end facing up. This helps to keep the yolk centred within them, making for more appealing boiled eggs with the yolk right in the middle.

If you are buying eggs with an eye to whipping egg whites, smaller eggs are actually better: their whites are more concentrated, less diluted with water.

Raw eggs are generally called for in recipes such as ice creams, royal icing, Caesar salad dressing, eggnog and mayonnaise. There is some concern over using eggs raw these days owing to possible salmonella contamination. In America, pasteurized eggs are now available. They are more expensive, so are perhaps best reserved for use in these recipes. You could also substitute powdered egg if you are concerned, or especially if preparing food for pregnant women, seniors or young children.

Egg production and sale in Canada continues to be controlled through a government mandated supply management system, even though the UK did away with their Egg Marketing Board in 1971.

Egg Sizes

In terms of how much weight of egg a consumer gets for an egg designated large, small, etc, British consumers get the most egg, followed by American consumers. Canadian consumers get the least.

Egg SizeUKAmericaCanada
Very large73g plus
Jumbo71g plus69g plus
Extra Large64g to 71g64g to 69g
Large63g to 73g57g to 64g56g to 63g
Medium53g to 63g50g to 57g49g to 55g
Small53g and less43g to 50g42g to 48g
Peewee35g to 43gunder 42g

In America, though eggs are ostensibly sold by size per dozen, they are actually sold by weight per dozen. 1 dozen large eggs will weigh 1 1/2 pounds (680g.) Small eggs can often be the best buy, in terms of price per pound. Consumers often buy large eggs, however, because a recipe calls for them, and people don't know the ratio for swapping in small or medium eggs.

Egg Size
Weight of 1 dozen
30 oz / 850g
Extra Large
27 oz / 765g
24 oz / 680g
21 oz / 595g
18 oz / 510g
15 oz / 425g

Eggs in the UK

In the UK, close to 95% of eggs sold are individually both date stamped, and stamped with a Red Lion logo. It means that the eggs are vaccinated against salmonella, and you can use them safely in items where eggs don't get cooked fully or at all, such as mayonnaise. Eggs used in the restaurant business, however, may come from outside the UK and therefore outside of the Red Lion scheme.

European legislation kicked in 1 January 2004, adding an additional stamp to the eggs. All eggs sold retail have to be stamped with a producer code that identifies the country and production method, as well as the farm or origin. Eggs sold from the farm or door to door don't have to be stamped (as the assumption is that the origin is already known.)

1st digit of code = circumstances under which the egg was laid.
0 = organic
1 = free range
2 = free range indoors
3 = battery or cage

The letters following this show country of origin, e.g. UK.

The last 5 digits are a number representing the farm.

The code is followed by a BB -- best before -- date. The best before date can be no more than 3 weeks after the laying date. Stores cannot sell to consumers eggs more than 3 weeks old.

Though the EU is trying to pressure the UK into requiring that store-sold eggs be washed, the UK egg industry is resisting because egg shells can easily allow detergents to pass through into the eggs, and because egg shells have an outer layer on them called the "cuticle", which blocks the porous surface of the shell, keeping freshness in and microbes out, but this is destroyed by washing.

Cooking Tips

If you really want to make a clear broth or stock, or make a consommé without wasting the egg white normally used to clarify one, rinse egg shells, add to the broth and simmer for about 10 minutes. The shells will attract sediment in the broth or stock. Strain.

Add a teaspoon of sherry to your next batch of scrambled eggs. Somehow it makes the taste come alive. Even better, a snip of fresh dill at the same time. Don't overdo the sherry, though, as you can easily go from enhancing the taste to killing it.

When boiling eggs, don't actually boil them. Keep the water at a gentle simmer. Eggs turn black or green when overboiled because the egg white releases hydrogen sulfide gas. This reacts with the iron in the yolk, forming "iron sulfide", and voilà, eggs with green rings inside them. Placing boiled eggs in cold water stops the reaction right away.

Egg shells can be composted. Or let them dry, whiz them in your blender to a fine powder, and sprinkle in your garden -- roses particularly appreciate the calcium. Some say that crushed egg shells will deter slugs and squirrels in your garden, but most people say this doesn't really work.

Pasteurizing your own egg yolks can be done at home in theory, but the practice seldom works. The process involves putting the egg yolks in a heatproof bowl and then into a pot of simmering water. You stir them constantly until they are about to set -- and then keep them at the temperature for about 3 minutes further. Should the phone ring, kids come running in, a microwave timer go off or your mind just plain wander, you end up of course with scrambled egg yolk. And even if you do manage to stay focussed on the task at hand, they usually end up setting on you, anyway.

Egg white coagulates between 140 to 150 F (60 to 65 C.) Both egg white and egg yolk set at 158 F (70 C.) Salmonella is killed instantly at 160 F (71 C.)

Rubbery fried eggs are caused by applying too high a heat to them for too long, which causes the proteins to cling together.


In making baked goods, you can substitute for 1 egg the following: 1/2 tsp baking powder plus 2 tsp butter or shortening plus 2 tbsp flour plus 2 tbsp liquid OR in cake, 1/2 teaspoon of baking soda plus 1 tbsp of vinegar, added at the very end of mixing.

There are many commercial egg-replacement products on the market now. See their package directions for how to substitute. Sometimes, you may want to add a tsp of oil such as canola per every two eggs being replaced, as the egg substitute is generally very low in fat, which could make your recipe drier.


The British Food Standards Agency (FSA) now says (2005) that you don't need to limit the number of eggs you eat, though you may not want, for instance, to make that a fried egg every day.
Weight Watchers®
Per 1 egg

* PointsPlus™ calculated by CooksInfo.com. Not endorsed by Weight Watchers® International, Inc, which is the owner of the PointsPlus® registered trademark.


1 cup eggs = 5 - 7 medium eggs = 5 large eggs

1 cup of egg whites = 8 to 10 medium eggs = 6 - 7 large eggs
1 cup of egg yolk = 12 - 14 medium eggs = 11 - 12 large eggs
1 cup egg, hard-cooked and chopped = 4 large eggs
1 large egg, hard-cooked and sliced = 6 slices
1 large egg, raw = 3 tbsp raw egg
1 yolk = 1 1/2 tbsp yolk = 1 large yolk
1 egg white = 2 tbsp egg white
1 large egg = 4 tablespoons (1/4 cup) liquid egg substitute

Storage Hints

You can store egg yolks covered in the fridge for up to 5 days. After that, freeze them for up to 4 months.

To freeze whole eggs, crack them, beat them lightly, pour into a container, then label the container before you freeze it as to how many eggs are in there.

Egg yolks frozen by themselves can be a bit gelatinous when you thaw them. To prevent this, mix in either 1/3 tsp salt or 1 1/2 tsp sugar per 4 egg yolks. (You don't need to worry about this when freezing whole eggs; the egg white will stop the yolk from becoming gelatinous.) Label the frozen egg package or container as either sweet or savoury, so that you know what to use them for. Don't forget as well to note how many egg yolks are in there.

Frozen egg whites will take about 5 hours to thaw at room temperature.

(Just to be totally clear here; you never freeze eggs right in their shells.)

History Notes

The domesticated chicken as we know it dates back to only about 3000 BC. Chickens were probably chosen as a fowl to domesticate because, while most birds while lay a certain number of eggs, chickens will keep laying until they accumulate a certain number of eggs.

The Romans used chicken eggs and left many recipes for them.

You couldn't eat eggs during Lent, until it was over on Easter Sunday, because eggs were classed as "meat" by Church dietary laws.

You may you wonder what they did with the eggs that chickens laid during that time. Eggs don't store for a long time, even with perfect refrigeration, and there was no point in solving the problem by killing the hens, as meat couldn't be eaten, either, unless you made a point of eating all your chickens before Lent started.

The older breeds available back then wouldn't have laid eggs in the winter anyway, in the first part of Lent, but they would have swung into high gear as spring and the end of Lent approached. Eggs could be preserved by pickling them, covering them in wax or a fat such as butter or lard, packing them in salt, or packing them in brine or water with lime in it. They could be dried, then used as a powder later.

Language Notes

French Terms for eggs:

Oeufs à la Coque (very soft-boiled)
Oeufs Brouillés (scrambled)
Oeufs Durs (hard-boiled)
Oeufs Frits (fried)
Oeufs Mollets (soft-boiled)
Oeufs Pochés (poached)
Oeufs sur le plat (baked)


Prince, Rose. Savvy shopper: Eggs. Daily Telegraph, London. 1 January 2005.

United States Department of Agriculture. Agricultural Marketing Service. Poultry Division. "United States Standards, Grades, and Weight Classes for Shell Eggs". April 1995. Retrieved May 2004 from http://www.ams.usda.gov/poultry/pdfs/AMS-EggSt-1995.pdf


Buttered Eggs (1); Coddled Eggs; Devilled Eggs; Duck Eggs; Egg Corrals; Egg Cups; Egg Cutters; Egg Day; Egg Nog; Egg Poached in Clingfilm Recipe; Egg Slicers; Egg Wash; Eggs Benedict Day; Eggs; Free-Range Chickens; Frittata; Meringue; Omelette; Pasteurized Eggs; Pickled Eggs; Poaching; Preserving Eggs; Quail Eggs; Safe Cooking Temperatures; Separating Eggs; Tortilla (Egg); Waxed Eggs

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Also called:

Oeufs (French); Ei, Eidotter, Eigelb, Eiklar, Eiweiß (German); Tuorlo, Uova (Italian); Huevos (Spanish); Ovos (Portuguese); Ovum (Roman); Tamago (Japanese)


Oulton, Randal. "Eggs." CooksInfo.com. Published 11 September 2002; revised 14 September 2012. Web. Accessed 06/23/2018. <http://www.cooksinfo.com/eggs>.

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