Sources of Fat

1. Adipose tissue of animals, as beef fat, suet, etc.

2. Bone marrow.

3. Milk. Fat globules are held in suspension in the milk serum. (See Milk, page 108.)

4. Some vegetables. Some vegetables contain a small amount of fat, but they do not form an important source of fat in the diet.

5. Some fruits and seeds. The olive is an important source of fat, furnishing olive oil. The seed of the cotton plant furnishes an important commercial oil, cottonseed oil.

6. Nuts. Nuts contain a large amount of fat. The oil of peanuts and cocoanuts furnish important commercial forms of oil.

Fats are composed of carbon, hydrogen, and oxygen. They contain a larger amount of carbon and hydrogen than do carbohydrates, hence have a greater fuel value.

Carbon

Hydrogen

Oxygen

Carbohydrates .... Fats........

44.4% 76.5 %

6.2% 11.9%

49.4% 11.5%

One pound of fat yields approximately two and one fourth times as much heat and energy as one pound of carbohydrates, hence forms a valuable food in cold climates.

Fats are composed of fatty acids and glycerine. Among the fatty acids are:

1. Stearic acid of stearin.

2. Palmatic acid of palmatin.

3. Oleic acid of olein.

One or more of these acids are found in all fats in combina-tion with glycerine. The fatty acid which predominates gives the characteristic to the fat.

Fats may be split up into fatty acids and glycerine by

(1) Being heated in very hot steam.

stearin glycerine stearic acid

(C17H25O2)3C3H5 + 3H20 = C3H5(OH)3 + 3C17H25COOH

(2) Bacterial action, as when fats become rancid.

(3) Action of fat-splitting enzymes of the digestive fluids.

(4) Action of strong alkalies, as in soap making.

(5) Action of high temperature, as in frying.

Fats are insoluble in water, but are soluble in ether, chloroform, gasoline, etc. To remove grease spots from clothing, moisten the spot with any of the above solvents and rub lightly until dry. The solvent will dissolve the grease and thus free the dust which may have adhered to it. This cleaning process should always be carried on in the open air and away from any flame, as the fumes of gasoline, etc., are very inflammable when mixed with air and ignite easily, often causing serious accidents.