This section is from the book "The American Woman's Cook Book", by Ruth Berolzheimer. Also available from Amazon: The Domestic Arts Edition of the American Woman's Cook Book.
This is one of the most important things for a good cook to know. If the cook can tell how much flour or corn-starch to use to make sauces or pastes of any desired thickness, and knows how to mix and cook these sauces and pastes to make them smooth, velvety and fine in flavor, he or she has learned one of the hardest cooking lessons and is in possession of information that will help in making a great variety of dishes.
With Each Cup Of Liquid:
1/2 tablespoon flour or
Makes a very thin sauce, which may be used in making thin cream soups.
1/2 teaspoon corn-starch
1 tablespoon flour or
Makes a thin sauce, which may be used in making cream soups of aver-age thickness.
1 teaspoon corn-starch
2 tablespoons flour or
2 teaspoons corn-starch
3 tablespoons flour or
Makes a thick sauce, which may be used for creamed meats or vegetables, scalloped dishes, gravies or sauces where a thick sauce is desired. A sauce containing this amount of flour has considerable body and spreads rather than runs.
1 tablespoon corn-starch
4 tablespoons flour or
4 teaspoons corn-starch
When the Liquid Used is Milk, use a little more milk or a little less starch than for a water sauce, because milk already contains about 12 per cent, solids.
When the Liquid Used is Acid, as vinegar, a fruit-juice or tomatoes, the hot acid acts on the starch and gradually changes it, just as dry heat does, to dextrin. Dextrin has not the thickening power of starch. Therefore, when an acid liquid is to be thickened, more of the thickening agent may be needed, and the time for cooking may be shortened. No statement can be made as to exact differences because acids differ greatly in strength.
When the Flour is Browned, the dry heat changes part of the starch to dextrin and the flour may lose a considerable part of its thickening power. Either more browned flour must be used than uncooked flour or browned flour may be used for color and uncooked flour for thickening.
Corn-starch Requires Longer Cooking Than Flour, and a quickly cooked corn-starch mixture always has a raw taste.
If a Sauce is Too Thick, it can be thinned without trouble by adding more liquid.
If a Sauce is Too Thin, it must be thickened by adding more of the thickening agent and by recooking it. A starchy sauce or a cream soup is always thinner when hot than when cold. Even the amount of cooling which occurs in transferring a starchy sauce, gravy or soup from the cooking utensil to the serving dish perceptibly thickens it. This must be taken into account in making creamed dishes of various kinds.
If a Sauce is Lumpy, because proper precautions have not been taken in mixing and cooking the thickening agent with the liquid, the sauce should be strained; but such a sauce never has the creamy, smooth texture of a well-made one.