Fats and oils are found in both the animal and vegetable kingdom. Fats are solid; oils are liquid; they may be converted into a liquid state by application of heat; they contain three substances, —stearin (solid), olein (liquid), palmitin (semi-solid). Suet is an example where stearin is found in excess; lard, where olien is in excess; and butter, where palmitin is in excess. Margarin is a mixture of stearin and palmitin. The fatty acids are formed of stearin, olein, and palmitin, with glycerine as the base. Examples: stearic, palmitic, and oleic acid. Butyric acid is acid found in butter. These are not sour to the taste, but are called acids on account of their chemical composition.
Among fats cream and butter are of first importance as foods, on account of their easy assimilation. Other examples are: the fat of meats, bone-marrow, suet (the best found around the loin and kidneys of the beef creature), cocoanut butter, butterine, and oleomargarine. The principal animal oils are cod-liver oil and oil found in the yolk of egg; principal vegetable oils are olive, cottonseed, poppy, and cocoanut oils, peanut oil, and oils in various nuts. Butterine and oleomargarine, which must be labelled as such, if of good quality, are nutritious, inexpensive fats to be used in place of creamery butter. Among other fats used for cooking purposes, lard, crisco, and cottolene are the most popular.
Oils are divided into two classes, essential and fixed. Essential oils are volatile and soluble in alcohol. Examples: clove, rose, nutmeg, and violet. Fixed oils are non-volatile and soluble in ether, oil, or turpentine. Examples: cottonseed, peanut and corn oil.
Fats may be heated to a high temperature, as considered in cookery they have no boiling-point. When appearing to boil, it is evident water has been added, and the temperature lowered to that of boiling water, 212° F.
