[Sidenote: Composition and formation of fats and oils]
The fats and oils in food products, whether of plant or animal origin,
contain the elements carbon, hydrogen, and oxygen. These fats are
formed by uniting the fatty acids with glycerin, which belongs to the
alcohol group. The particular fat that is formed takes its name from the
acid which enters into its composition; thus stearic acid unites with
glycerin to form the fat stearin.
The following table gives the names of a few of the more common fatty
acids and their corresponding fats:
Stearic acid Stearin
Palmitic acid. Palmitin
Oleic acid Olein
Butyric acid Butyrin
[Sidenote: Distinction between tallow and lard]
A fat from any source will usually contain several of these chemical
compounds. The ordinary animal fats, such as tallow and lard, are formed
chiefly of the two fats stearin and olein. The different proportions of
these fats will determine the melting point or hardness of the mixed
product. Olein is a liquid at ordinary temperature, while stearin is
solid. The reason that tallow is a firmer fat than lard or butter is
because it contains a larger per cent of stearin.
Olive-oil, cottonseed-oil, and other vegetable oils contain large per
cents of olein, which accounts for their being liquid at ordinary
temperature.
[Sidenote: Dairy butter vs. artificial butter]
Butyrin is a fat found in small quantities in dairy butter, and does
not exist in cottonseed-oil and other fats from which oleomargarin is
manufactured. This is the reason that artificial butter lacks the flavor
of the dairy product, and this is remedied to some extent by churning
the fats of the cottonseed-oil and tallow with fresh cream, which
imparts a small quantity of the butyrin and similar compounds to the
oleomargarin and gives the characteristic flavor of butter.
[Sidenote: Oils as active poisons]
Besides the more common fats herein mentioned there are many other fats
that exist in certain vegetable oils in small proportions. These fats
give the oils their characteristic properties, and may render them unfit
for food. Some oils are active poisons, such as croton-oil, which is the
most powerful physic known. The power of all physics and cathartic drugs
is measured by the active poisons they contain.
[Sidenote: Packing-house uses of stearin and olein]
When fats are heated to a high temperature they decompose and form
various products, some of which are irritating and poisonous to the
human system. In the manufacture of packing-house and cottonseed
products the stearin is often separated from the olein. The granular
appearance of pure leaf lard is due to crystals of stearin. In the
packing-house stearin is separated from the tallow in large quantities.
The stearin is used to make candles, etc., while the olein is used
for food purposes in this country in the form of oleomargarin, while
in Europe it is used under its right name as a cooking product. It is
equally as wholesome, if not more so, than lard.
[Sidenote: Rancid fats made edible]
Fats may become rancid; this is caused by the decomposition of fat due
to its uniting with the oxygen of the air. Rancid fats and nut-kernels
can be restored and made edible by heating them in an oven until the
oxidized fat is neutralized by the heat.