GLUTEN (Lat., glue), that part of the protein content of wheat which is insoluble in water. It is a combination of the two proteid substances gliadin and gluten in, the first con; taining 17.66 per cent of nitrogen, and the second, 17.49 per cent.. These components, however, do not combine in the wheat kernel, nor in wheat flour to form gluten: it requires the presence of water to initiate the combina tion. Gluten is insoluble in water containing salts, hut the gliadin component is soluble in distilled water and also in alcohol. As found in wheat flour dough, gluten consists of about two-thirds gliadin and one-third glutenin, and it is this constituent of wheat flour which tauses.the dough to be sticky, entrapping the bubbles of gas from .ferrnentatire action of the yeast, or from the chemical action of baking-powder, and °lightening° the dough into •a °sponge.° Some glUtens are tough and elastic, others soft and The latter lack the quality of absorbing water, and do not hold the sponge made by the yeast, thus making a poorer bread, and fewer loaves to the barrel of flour. The strength of a gluten depends upon the proportion of gliadin to glutenin, and also to the _presence or absence of certain mineral salts. The so-called °hard° wheats and those grown in hot countries have a larger gluten content than the °soft° wheats, or those grown in cold climates. The amount of gluten from any sample of flour, also, in creases with the hardness of the water used and with the time the dough is permitted to stand, this increase ranging up to more than 6 per cent. The Mauve elasticity of the glutens in different samples of flour is some times tested with an instrument called the aleurometer, which operates on the expansion of wet gluten when exposed to a temperature of 300° F., but this test fails in the vital point that the value of a gluten depends not on its quantity, but on its quality. Of two samples of flour containing equal parts of gluten, one may be worth in bread-making more than twice the value of the other.
To obtain gluten from wheat, the grain is reduced to dough, and the starch removed by mechanical the resultant product be ing a grayish, tough, elastic, sticky substance which, when rightly proportioned in its gliadin glutenin content, is capable of being drawn out into long bands or shreds. Crude gluten
consists of about 74 per cent of gliadin and glutenin, 7 per cent of non-gluten proteins and the remaining 19 per cent of fat, carbohydrates, are and mineral salts. In the domestic opera tion of separating the gluten from flour for making gluten bread for diabetic patients, a °strong° flour is made into stiff dough with hard water. This is allowed to stand for about an hour. The dough is then kneaded in water in small portions usually placed in loose muslin bags, the starch escaping through the bag and producIng a milky appearance in the water. The kneading is continued in suc cessive waters until no more °milkiness° washes our.
In its highest refinement, gluten exhibits a Aire molecular structure, delicate and sensitive to atmospheric conditions, and requires, after separation, immediate handling in its prepara tion for food.
About 16 pounds of gluten is obtained from 200 pounds of wheat-flour, On account of its high content of nitrogen, gluten soon deli quesces, sours and spoils after the separation from the starch, and demands an immediate treatment if desired for food purposes. What are known as gluten feeds are by-products in the manufacture of starch and glucose from corn, and the dried residues from the distilling of spirituous liquors. They have a nutritive value about equal to brewer's grains. To the glucose and starch makers corn consists of starch, gluten, germ and bran, all but the starch being by-products. They are separated by mechanical processes. The free germs of the corn are dried, grotind to meal, the oil extracted by solvents leaving oil-cake, a cattle feed extensively used. The wet starch is run through vibratory sieves and over long wooden tables, the starch and gluten forming the mixture which passes through the sieves; the starch being deposited by gravity, the gluten liquid passes off at the ends of the tables. When evaporated, pressed and dried, this con stitutes the gluten-meal of commerce. About five and one-half pounds is obtained from one bushel of corn..