Gelatin

Gelatin, protein substance obtained by boiling animal bones and connective tissue containing collagen in water or dilute acid. It is colorless, transparent, brittle, odorless, and tasteless in a purified form. Gelatin dissolves in hot water and forms a gel or jelly upon cooling. It is insoluble in organic solvents, such as ether, chloroform, and benzene. When placed in cold water, gelatin takes up five to ten times its own weight and swells to an elastic, transparent mass.

Gelatin in its purest form is used as a constituent of foods, being highly nutritious and easily digested and absorbed. It cannot, however, completely replace other proteins because it lacks some essential amino acids. Gelatin is used in making jams and jellies, ice cream and marshmallows and as a setting for other foods in aspics. It is employed in photography in the preparation of film, plates, and paper; in bacteriology as a culture medium; and in medicine as a coating for capsules, pills, and some surgical dressings. It is also used in dyeing and in photomechanical printing processes.

Glue is an impure form of gelatin. A purified form of gelatin obtained from the air bladders of certain fishes, including sturgeon, cod, catfish, and carp, is called isinglass.