GLUTEN (Lat., glue). One of the most im portant constituents of the varieties of corn used as food. It is obtained by mixing flour with water, and thus fornfing a paste or dough. This paste is placed in a bag of fine linen, and kneaded in water, which must be repeatedly changed, till it ceases to assume a milky appearance. A gray, tenacious, viscous, tasteless substance, having the appearance of bird-lime, is left in the bag. This substance consists mainly of gluten, mixed with traces of bran starch and of oily matter. The gluten thus obtained from wheat and from rye is far more tenacious than that which is obtained from the other cereals, and it is the great tenacity of this constituent that especially fits these flours for conversion into bread. It is found, by analysis, that the proportion of gluten contained in wheat grown in hot countries is considerably higher than in wheat grown in colder countries; and the hard, thin-skinned wheats contain more of this ingredient than the softer varieties of the grain. Gluten in a moist state rapidly putrefies, the mass acquiring the smell of decaying cheese; but when dry, it forms a hard, brownish, horny-looking mass, that does not very readily decompose. On treating gluten with hot alcohol, it resolves itself into at least two distinct substances, one of which is soluble, and the other insoluble in that fluid. The in
soluble portion is vegetable fibrin. It is a gray, tough, elastic substance, insoluble in water or in ether, but readily soluble in dilute alkalies, from which it is precipitated by neutralization with acetic acid. It is also soluble in very dilute hy drochloric acid, from which it is thrown down by the neutral salts. The soluble portion is in part precipitated from the alcohol on cooling, in the form of flakes, which have the composition and properties of casein; while a third substance, known as gliodin, remains in solution, giving to the alcohol a syrupy consistence. It separates, on the addition of water, as a white substance re sembling albumen. All these constituents of gluten contain carbon, hydrogen, nitrogen, oxy gen, and sulphur, in much the same proportion as the proteids, and they all doubtless belong to the flesh-forming group of foods. The action of gluten in the manufacture of bread is probably a double one; it induces, by constant action, an alteration of the starch, and subsequent fermenta tion, while by its tenacity it prevents the escape of carbonic-acid gas.
The large quantities of gluten obtained as a by-product in the manufacture of starch are at present utilized for the manufacture of certain articles of food.