This section is from the book "Mrs. Allen's Cook Book", by Mrs. Ida C. Bailey Allen. See also: The Conscious Cook: Delicious Meatless Recipes That Will Change the Way You Eat.
Deep-fat frying is used for various foods; croquettes, fish-balls, thin meats, like veal steak or chops or chicken, small fish, as oysters, smelts or brook trout, fritters, doughnuts, fried cakes, and several vegetables as well can be cooked in it with much less trouble and better results than in the skillet. It is necessary to know the exact time each must cook before attempting this method.
Croquettes, which are always made of cooked ingredients, as chicken, potato, salmon, etc., simply need to be browned, and re-heated in the hot fat. When it is of the right temperature, they can almost be immersed and then be immediately lifted out - when they will be brown, crusty and hot. Uncooked mixtures, like doughnuts, fritters, and fried cakes, must be cooked more slowly, as, otherwise, the very hot fat will cause a crust to form before they have risen properly, and the expanding gases will burst through the crust, causing the food to "soak fat." Potatoes for French frying need a still longer time, while raw meats cannot cook under five to seven minutes.
The old-fashioned "smoke test" to ascertain the readiness of fat for cookery is not satisfactory, as any fat that smokes is burned, and, therefore, broken up. It is because of this fact that fried food disagrees with so many. The term "when the fat boils" is still in common usage; but fat itself cannot boil; it is the water within it that becomes hot, generates steam, and causes the fat apparently to "boil." That is why, when wet potatoes are submerged in it, the fat rises as in boiling, and, unless the kettle is sufficiently deep, effervesces over the sides to the heat and may cause a fire. The only easy kitchen test for the temperature of fat is with a bit of bread. The length of time which is consumed in browning the bread determines the readiness of the fat for each particular food. The time must be measured by the clock to insure success in using this method. The following table gives the exact time needed to brown the bread in testing for each food:
Croquettes and Oysters
Doughnuts, Fritters, etc.
1 1/2 minutes