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Egg

The astonishing and unintentional gift from birds to human beings, the acme of food packaging, and a prime resource of occidental and oriental cooks alike. It is also the ultimate measure of ignorance and incompetence in the kitchen; ‘he/she can't even boil an egg,’ she/he will say, whether fondly or resentfully.

A reference to ‘an egg’, with no qualification, is assumed almost everywhere to mean a hen's egg, which is what this essay is about. For other eggs, see Duck, ostrich, quail. The hen's egg is usually the one which carries symbolic significance (the renewal of life, e.g. in spring festivals and Easter foods). Symbolic meanings and folklore and associated topics are admirably dealt with by Venetia Newall (1971).

Eggshells

Whether they are white or brown or speckled is immaterial to the cook. What does matter is that they are porous. One consequence of this is that eggs may absorb unwanted odours, a risk to which textbooks often call attention but which in practice seems to be slight. Another is that the carbon dioxide which begins to be formed within the egg as soon as it is laid can get out. Loss of carbon dioxide increases alkalinity and causes a slight diminution in the protein content of the egg. Egg processors prevent this by dipping their cleaned eggs in a special colourless and tasteless machine oil which seals the pores of the shell. By this means they also prevent another undesirable development, which is a gradual loss of moisture from within the egg and a corresponding increase in the size of the air pocket. They also, no doubt unwittingly, make it impossible to execute some kinds of egg cookery which are typical of the Middle East, notably ‘hamine’ eggs, in which whole eggs are simmered overnight, very gently, with oil and onions, whose flavour permeates the contents. A more exotic example is provided by Œufs à la constantinopolitaine, a recipe given by Mrs Leyel and Olga Hartley (1925), which calls for cooking eggs in their shells very slowly for at least twelve hours in a mixture of olive oil and Turkish coffee. The mixture eventually penetrates the shells, making the whites amber and the yolks orange and imparting a flavour of chestnuts.

There is one recipe which is unusual in that it involves the consumption of the eggshells. It is given by Dr Fernie (1905), in the guise of a tonic:

For delicate persons of all ages, the following preparation, which will contain egg shells in solution, has been found most singularly useful. Take six fresh eggs, six lemons, half a pound of castor sugar, and half a pint of white rum. Put the eggs in their shells inside a jar, without injuring the shells, peel the lemons, and, after removing their pith, squeeze the fresh juice over the eggs, then lay above them the rind and the pulp. Cover the jar lightly, and put it in a cool place for seven days, not forgetting to shake it well on each day. At the end of that time strain through muslin, when it will be found that the lemon juice has dissolved the eggshells. Add the sugar, and the rum; then bottle and cork it tightly. A wineglassful taken each morning before breakfast is the full dose, but at first it may be desirable to give only half this quantity.

Since the shell of an egg, surprisingly, constitutes a tenth of the whole, and since it contains a lot of calcium and even a little protein, this can be represented as an economical procedure for those with access to a free supply of rum.

Egg proteins

These are what make an egg so important a source of nutrition, and such a versatile ingredient for the cook. Consider the composition of an egg, as shown in the table.

It will be apparent that the white, apart from its large water content, is almost pure protein; and that the yolk contains proportionately less water, more protein, and much more fat. White and yolk can therefore be expected to, and do, behave differently when cooked. Moreover, the proteins in the yolk are not the same as those in the white, and coagulate at a distinctly higher temperature.

(Many books refer to egg white as ‘albumen’, which has the same meaning. However, this term can be confusing because there is also the word ‘albumin’ which refers to a class of proteins, all soluble in water, which includes albumen and others too.)

The protein in egg whites starts to coagulate in the temperature range 55–60 °C (131–40 °F) and definitely coagulates at about 65 °C (150 °F) or a little less. Those of egg yolks begin to thicken at 65 °C (150 °F) and coagulate at just over 70 °C (158 °F). Thus the yolk always sets after the white, whether an egg is being boiled (when this would be bound to happen anyway because the heat reaches the yolk later than the white) or being fried.

Methods of cooking eggs

The poaching of eggs is a subject best introduced by the eccentric Dr Kitchiner (1818) who has this to say as a preface to the mysterious ‘Moost Aye's receipt to Poach Eggs’: ‘The Beauty of a Poached Egg, is to have the yolk seen blushing through the white, which should only be just sufficiently hardened, to form a transparent Veil for the Egg.’

However, ‘Moost Aye’, if there was such a person, omitted one important step in the preparation of an aesthetically satisfying poached egg. A little vinegar must be added to the boiling water before the egg goes in. The reason for this is that the acid promotes coagulation and reduces the tendency for long streamers of egg white to form. It is also helpful to whirl the water round and then break the egg into the centre of the whirlpool.

(Many people have ‘egg-poachers’ which consist of one or several shallow metal containers, each of a size to take one egg and fitting into a larger container in which water is boiled. The small containers are buttered and the eggs broken into them. The results are quite pleasing but are not, strictly speaking, poached eggs. Indeed it is hard to know how to classify them. They are really closer to fried eggs, although steaming plays a part in their cookery.)

Boiling eggs calls for little comment, except for the admittedly fundamental one that it is best not to boil them. If they are put in simmering water, just below boiling point, the risk of overcooking the white (to which the heat penetrates first) before the yolk (to which it passes later) is done is reduced; and so is the risk of the shell cracking owing to the egg being bumped around by violent agitation of the water.

If hard-boiling (American hard-cooking) eggs, do not choose absolutely fresh eggs, in which the white adheres closely to the shell, making it more difficult to remove the latter. The eggs should be rinsed under cold water after removal from the pan; this halts the cooking process, which would otherwise continue for a while and leave a disfiguring dark green colour where the yolk meets the white.

The frying of eggs (in a shallow pan, in butter, bacon fat, or oil) presents one problem. Since the heat is all coming from below, the upper parts of the white and the yolk will be last to cook, and in the meantime the lower parts may become overcooked. Putting a metal lid over the pan, to reflect heat downwards, is one solution and should produce an evenly cooked ‘sunny-side-up’ effect. Flipping the eggs over, to produce American ‘up-and-over’ eggs, is another.

Since the addition of liquid to an egg mixture raises the temperature at which the protein coagulates, the scrambling of eggs (or making an omelette) will call for a higher temperature. However, scrambled eggs are best cooked very gently, and it is advisable to remove the pan from the heat just before the mixture reaches the desired final consistency; to halt the cooking at that point by adding a few knobs of cold butter or a little cream; and then to stir some more.

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