Eggs
Eggs consist chiefly of two nutrients,—protein, and fat (ten per cent), combined with water, phosphorous, and ash. Eggs are a wholesome source of protein and are, therefore, classed as nitrogenous foods.
The fat and the iron are in the yolk, which is about one-third fat. The yolk also contains phosphorous and some ash. The white is practically free from fat but contains sulphur, phosphorous and a very little ash. The white and the yolk contain almost equal quantities of protein.
The white of the egg is said to be pure albumen; the chief ash constituent is common salt. The total phosphorous in the white of the egg is equivalent to about two per cent phosphoric acid and the total phosphorous in the yolk is equivalent to one per cent.
The dark stain made by eggs on silver is due to the sulphur contained in them. The iron in the egg is valuable to assist in building red corpuscles.
The large part of the egg, as other proteins, is changed, mostly in the stomach, into peptone, absorbed as peptone and then changed back again into protein after absorption. That not digested in the stomach is changed in the intestine, as is the case with other proteins.
Eggs are, no doubt, excellent articles of food for nutrition and for tissue building. They contain more water than cheese, but are more concentrated than milk or oysters. They have practically the same relative value in the diet as meat, and make a very good substitute for meat. Egg yolk in abundance is often prescribed where it is necessary to supply a very nutritious and easily assimilated diet.
One of the best methods of preparing eggs, which is especially valuable for those having delicate stomachs or for those who need to build up red blood corpuscles with the iron in the yolk, is in egg lemonade or orangeade. Thoroughly beat the egg, add the juice of half a lemon or orange, sugar to taste, and fill the glass with water.
The citric acid in these fruits partly digests the egg, changing it into egg albumin,—the egg becomes limpid, no longer stringy. From this condition the gastric juice quickly changes it to peptone.