This section is from the book "Elements Of The Theory And Practice Of Cookery", by Mary E. Williams. Also available from Amazon: Elements Of The Theory And Practice Of Cookery; A Textbook Of Domestic Science For Use In Schools.
But of course, dirty eggs must be washed, and any egg may be wiped with a clean damp cloth just before being broken. Eggs spoil because of bacterial growth in them. Even new-laid eggs contain some bacteria. Eggs keep losing water by evaporation through the shells. Air enters to take its place, and with the air bacteria. (Explain why a stale egg often rattles, and why a very stale one may float.) Clean eggs kept cool remain for a week or more practically as good as when laid. But gradually they develop an unpleasant taste and odor, and the yolk clouds the white. Eggs not quite fresh enough to taste good cooked by themselves are all right for other uses. No housekeeper will use really bad eggs, but unless the government prevents their sale, we are in danger of eating such eggs in cakes and other foods made by unscrupulous bakers and manufacturers.
As hens lay best in spring and early summer, it is necessary to preserve some eggs for winter use. One way of doing this is to seal the pores of the shells against bacteria. The best covering is a solution of water-glass. This method can be used at home.
The second method is cold storage, used by dealers. Eggs do not freeze at 32° F., and at this temperature, although some changes take place, they remain fit for use for several months.
Cook one egg (a) in boiling water for three minutes; another (6) in boiling water for ten minutes; put a third (c) into boiling water enough to cover it (about one pint in a small saucepan), remove the saucepan from the fire, and let it stand covered on the table from six to ten minutes. Break the eggs and compare their contents. In which is the white hard and the yolk unchanged? In which is the white hard and the yolk sticky or partly dry? In which is the white a tender jelly and the yolk thick?
An egg put into boiling water and removed from the heat is, at the end of about ten minutes, evenly cooked through, the temperature of the water falling during this time to about 168° F. The temperature of the egg averages about 185° F.
Put a little white-of-egg in a test-tube; hold the test-tube and chemical thermometer in a vessel of water. Heat the water gradually. How does the white-of-egg look at 150° F.? at 180° ? Stir with glass rod or a stick to show degree of solidity. Note appearance and degree of solidity at 212°. Keep the water boiling for several minutes; then take out some of the white-of-egg and examine it.