The average weight of a hen's egg in the shell is two ounces.
The egg consists of the shell, the white, and the yolk. The shell is composed of carbonate of lime, - that is, chalk. It is full of minute pores or holes through which the air passes for the use of the young bird in the process of hatching. Now as it is the air which causes putrefaction by its chemical effect, we can only preserve eggs by making them air-tight. Whatever, therefore, will perfectly close the pores in the egg-shell will preserve the egg.
Rubbing the new-laid egg over with fat or oil, or gum answers well; and there are several other modes of closing them, as packing them in bran, or just dipping the egg once or twice in boiling water. Saw-dust packing gives a bad flavour to the eggs. The best way is to grease them over or gum them, and turn them occasionally from side to side.*
An egg contains fifty-five parts of carbon, sixteen of nitrogen, seven of hydrogen, and the remaining twenty-two are oxygen, phosphorus, and sulphur. The offensive smell of stale eggs is caused from the hydrogen of the egg combining with its sulphur and phosphorus, and thus forming sulphuretted or phosphuretted hydrogen - two gases which have a horribly bad smell.
I lb. of Shelled Eggs contains -
Albumen . . . .
Extractive matter .
Oil or Fat ....
It is the sulphur in the egg which uniting with the silver of an egg-spoon tarnishes it as soon as it is moistened with the saliva. This tarnish is sulphuret of silver. It can be removed by rubbing it with table salt.
"The yolk of the egg," says Dr. Hunter, "is a natural soap, and in all jaundice cases no food is equal to it. When the gall is too weak, or by accidental means is not permitted to flow in sufficient quantity, our food which consists of watery and oily parts cannot unite so as to become chyle. Such is the nature of the yolk of an egg, that it is capable of uniting water and oil into a uniform substance, thereby making up for a deficiency of natural bile".
The shell forms more than a tenth part of the weight of the egg, the white six-tenths, the yolk three-tenths.
The white of the egg is the substance known to chemists as albumen; in a nutritive sense it answers to the gluten of vegetables and fibrin of meat.
The yolk consists of fat and a variety of albumen. It contains also a trace of milk sugar.
The egg is much richer in fat than beef, and is, in fact, only equalled in it by pork and eels.
Eggs are, therefore, very nutritious. The white is constipating, and the egg is better eaten without it by invalids or children - we mean simply the yolk should be eaten by them.
Fat eaten with eggs makes them more laxative, hence "bacon and eggs "form a judicious mixture.
The white of the egg has a glairy consistence, which enables it, when mixed up with moistened flour, arrowroot, sago, etc., to retain the globules of air or of steam which are produced by heat, and thus it enables the mixed materials to swell up into a porous mass. Therefore white of egg gives lightness to puddings, cakes, etc. When we speak of eggs in puddings we mean hen's eggs, because they are the only eggs to be had all the year round.
Turkey and goose-eggs are too valuable for eating in the early summer, but in autumn turkey eggs are often used and are excellent. Ducks' eggs are common enough, but they are richer and not so delicate as hens' eggs.
* M. Burnouf recommends in a French journal of agriculture the following method of preserving eggs: - Dissolve in two-thirds of warm olive oil one-third of beeswax, and cover every egg completely with a thin layer of this pomade with the end of the finger. The egg-shell by degrees absorbs the oil, and each of its pores becomes filled with the wax, which hermetically seals them. M. Burnouf affirms that he has eaten eggs kept two years in this manner in a place not exposed to too great extremes of temperature. He thinks also that the germ may in this way be preserved for a considerable time.
A fresh egg feels heavy in the hand; but the best way to prove them is to try them in water. Put an egg into a basin of water, if it stands upright on the end it is bad; if it lies obliquely it is not quite fresh; if it floats it is bad; if it lies at the bottom it is quite fresh. A fresh egg takes half a minute longer to boil than a stale one. The yolk of an egg sets before the white does, and if it is put into cold water, before the water boils; the white becomes fixed at the temperature of scarcely boiling water. Very little heat is required therefore for sauces made with yolk of egg; a little more when white and yolk are boiled together. If boiled custard, or any milk and egg custard, boils in the dish, the egg runs to whey, and the dish is spoiled; quick boiling converts the white of egg into a leathery substance, while the yolk is still moist. The way to make water boil slowly - i.e., to delay its boiling, while it gets extremely hot - is, as we have said in "Domestic Science," to add a body to it less volatile than itself.
Salt does it, and it is therefore used for poaching eggs, which are plunged suddenly into boiling salt and water, in order to set the albumen speedily.
There are many modes of cooking eggs. We insert a few delicate modes of dressing them: -