The higher the burning point of a fat, the more valuable is the fat for frying purposes, as it will retain a greater amount of heat before it carbonizes. Butter has a low burning point, hence carbonizes easily and is a poor fat to use for frying.

Experiment 74

Take temperature of fat when it begins to heat with a laboratory thermometer that will register 450° F. Note temperature of fat when it bubbles. What is the cause of the bubbling? Heat until it stops bubbling and begins to smoke. Note temperature. Drop in a slice of potato. What causes the bubbling in the fat? What is the temperature of fat when it is hot enough for frying ? Note odor of acrolein.

Experiment 75

Heat in separate pans small amounts of butter, lard, cottolene, and other commercial fats. Which burns most easily? Which has the highest burning point?

Cost Of Fat For Frying

When making doughnuts put a definite weight of lard and any fats used locally for frying, in kettles of the same size. Fry an equal number of doughnuts in each. Weigh the lard and the other fats which are left after frying, computing the amount and cost of the fats used. Estimate the cost of frying a dozen doughnuts in each kind of fat.

Rule For Testing Fat

When the fat begins to smoke, drop in an inch cube of bread from the soft part of the loaf. If it browns in forty seconds the temperature is right for frying any cooked mixture, as croquettes; if it browns in sixty seconds it is right for uncooked mixtures, as doughnuts.