The Science of Cooking an Egg

The egg white coagulates (turns from liquid and solidifies) at a temperature between 144 and 149 degrees Fahrenheit (62 and 65 Celsius). Egg yolk coagulates between 149 and 158 degrees Fahrenheit (65 and 70 Celsius). This difference in coagulation is why you can fry an egg and have the white fully solidify while the yolk remains runny or, for the sake of this chapter, how you can cook a soft-boiled egg so that the white is fully opaque while the yolk is still runny.

The coagulation is referred to as curdling in older recipes. It does describe the chemical reaction within the egg. When eggs are heated, the long chains of amino acids unfold and straighten out, and then as the temperature increases (to the ideal coagulation point), the proteins create stronger, firmer new bonds. The biological terminology for this is denaturing the protein. Denaturing is what happens when you cook an egg: in frying, when it forms a solid mass, and in scrambling, when it turns into soft lumps, or curds.

However, the current scientific definition of curdling is syneresis. (Syneresis is the separation of liquid from a coagulated mass, such as what happens in cheese-making when whey separates from the cheese curds.) In the case of eggs, their protein becomes overcoagulated and “breaks.” When this happens, liquid is forced out of the lumps of protein. Without liquid, the protein binds together more tightly. The result is a lumpy, almost granular texture.

Too high a heat or an overly long cooking time can cause this. When it happens, the cooking term (when one is talking about a sauce, for instance) is that it breaks. A break is considered to be a total and utter failure of the sauce, the custard, the emulsion.

Newer cookbooks and recipes on the Web try to slap on scientific names (used in other cooking science such as cheese-making) that are not a good fit. The point is that the modern definition that associates egg curds with syneresis (instead of denaturing) is confusing. Borrowed descriptive terms are not a good fit for cooked eggs.

Egg Proteins Altered

There are three ways to change the proteins in eggs: heat, beating, and chemical reaction.

1.) Heat causes the proteins to unfold and reconnect. Moderate heat (medium or medium-low) is better than high heat, which causes the bonds to connect too strongly, resulting in a rubbery, tough cooked egg. If you boil an egg on too high a heat, you may see a greenish tinge on the cooked egg yolk if the iron sulfide in the yolk reacts with the hydrogen sulfide in the white (This does not change the quality or the flavor of the egg, but it looks unattractive.)

2.) Beating or whisking egg whites causes the protein bonds to break and reconnect. The new bonds are stronger and cross-linked. Once an egg yolk is whipped into a foam, it will not return to a liquid.

3.) Chemicals that can denature, or break, the protein bonds in eggs include vinegar, lemon juice, cream of tartar, and alcohol. Numerous recipes call for the addition of an acid to egg whites for meringues, soufflés, sponge cakes, and the like, because it lengthens the protein strands and allows for stiffer egg white foam.

Egg whites are easier to alter than egg yolks, because the proteins in egg yolks are more resistant to change.

Old Cookbooks: Columbia Cook Book, 1902

In my old first edition (1898), Columbia Cook Book, which was written by the Ladies Aid Society of the First Baptist Church of Colombia, Tennessee, there are some egg recipes that I have never come across in my quest for egg recipes.   Eggs are discussed at great length in this compiled book. It was back in the day when every home had chickens in the yard. The recipes have been copied exactly as they were written in the cookbook.  In old cookbooks the recipes were written by many different people, and not well edited, or formatted to list ingredients first, and then instructions. In some cases the wording is awkward, and who knows what they’re talking about.  It’s a little odd to read, but the variation and scope of the use of eggs as a meal. Its interesting to revisit these old gems..

colombia cookbook

Columbia Cookbook 1902 , the Bradley & Gilbert Company

There are so many ways of cooking and dressing eggs that it seems unnecessary for the ordinary family to use only those that are most practical.

The first point of importance is to see that your eggs are perfectly fresh by putting them in a pan of water, and if fresh they will sink immediately, or float if doubtful.  Or, hold them before a strong light, and if the yolk appears round and the white surrounding clear, the chances are that it is good.

Eggs are highly nutritious, pleasing to the palate, and easy of digestion, and are said to contain all that which is required for the sustenance of the human body.  So that they should form part of the daily bill of fare for every family.

The fresher eggs are, the more wholesome, although new-laid eggs require to be cooked longer than others. Eggs over a week old will do to fry, but not to boil. Do not mix eggs in a tin: always use earthenware.

The best and safest plan to feel assured of the freshness of an egg before using is to break each egg into a saucer before cooking, for if one egg is slightly tainted, it will leven the whole.

Boiled Eggs

The fresher laid the eggs are the better. Put them in boiling water; if you like the white set, about two minutes’ boiling is enough. A new-laid egg will take three minutes if you wish the yolk set. To boil hard for salads or made dishes will take ten minutes.

Poached Eggs

Two eggs, two tablespoonfuls of milk, half a tablespoonful of butter. Beat the eggs and add the salt and the milk. Put the butter in a small sauce-pan, and when it melts add the eggs. Stir over the fire until the mixture thickens, being careful not to let it cook hard. About two minutes will cook it. The eggs, when done, should be left soft and creamy. Serve immediately

Creamed Eggs

Break as many eggs in a buttered pie-dish as it will hold without crowding each others. Sprinkle with pepper and salt, and put a bit of butter on each. Have ready a cup of hot milk in which has been cooked for one minute a teaspoon of corn-starch, or better yet arrowroot wet up with cold water. Pour this, a spoonful at a time, about the raw eggs, and bake it in a quick oven until the eggs are fairly set. Five minutes should do it. Send to table at once in the pie-plate.

Baked eggs

Soak a cupful of bread-crumbs in a half a cupful of hot milk for twenty minutes, stir in a teaspoonful of butter, the yolk of an egg, a tablespoonful of grated cheese, two tablespoonfuls of savory broth, a little minced onion, and a teaspoonful of minced parsley. Pour the mixture into a neat pie-plate, and set, covered in a quick oven. In six minutes lift the cover, break as many eggs on the bubbling surface as the dish will hold, sift the fine crumbs on top and leave in the oven for three minutes longer. Serve in the dish.

Fricasseed Eggs

Boil for fifteen minute, throw at once into cold water, and let them lie there for the same time. Peel, cut each in half length-wise; extract the yolks and rub smooth with a teaspoonful of anchovy paste, a little made mustard, and the tiniest suspicion of cayenne. Mold this pasty mixture into balls of the same shape and size as the yolks, put them into the cavities left in the halved whites, fasten them in place by tying firmly with cotton twine when you have skewered them together with wooden toothpicks, once through each bisected egg. Have ready in a sauce-pan a good cupful of drawn butter (drawn with milk, not water), season with pepper, salt, and minced parsley. Lay the eggs in carefully; set the sauce-pan covered in boiling water, and cook gently, keeping the water outside at a slow boil for ten minutes. Arranges the eggs in a pile on a heated platter, and pour the sauce over them.

Meringued Eggs

Whip the whites of the eggs very stiff. Lay great spoonfuls of the standing froth on a platter that will stand the oven heat. With the back of a tablespoon make a hollow in the middle of each heap, and put a raw yolk in it. Set in the oven until the meringue begins to color faintly, sprinkle with pepper and salt, lay a bit of butter on each egg, and serve in the platter in which they were baked.

Fried Eggs

Melt some butter in a frying pan, and when it hisses drop in the eggs carefully. Frey three minutes; dust with pepper and salt, and transfer to a hot dish

Scrambled  Eggs

Heat the spider, and put in a little butter; have the eggs broken into a dish, salt and pepper them,; add a small piece of butter; beat up just enough to break the eggs, then our into the buttered spider; scrape the up from the bottom with a thin knife, to prevent their cooking fast; do not cook too dry

Buttered Eggs

Four eggs, two ounces of butter, two tablespoonfuls of cream, a little grated tongue, pepper, and salt to taste, pieces of buttered toast. Break four eggs into a basin, and beat them well; but two ounces of butter and two tablespoonfuls of cream into a saucepan; add a little grated tongue, pepper and salt to taste; when quite hot add the eggs, stir until nearly set, then spread the mixture on pieces of buttered toast and serve.