COMMERCIAL GLUCOSE. The term glucose is also applied to mixtures of the substance de scribed above with other carbohydrates, the various mixed products being otherwise called `starch-syrup,' corn-syrup,"starch-sugar,"corn sugar,' etc. Starch is the favorite material for the manufacture of commercial glucoses. Potato starch is largely used for this purpose in Europe; in this country corn-starch is at present practi cally the only commercially possible raw ma terial. The manufacture of corn-starch and the conversion of it into glucose are generally con ducted in the same establishment, the two proc esses together constituting a very large industry. It was estimated in 1898 that the glucose in dustry of the United States annually consumes approximately 35,000,000 bushels of corn. In 1884 6,773,115 pounds of glucose and grape sugar, valued at $212.628, were exported by the United States; while during the fiscal year end ing June 30, 1901, the exports of these commodi ties amounted to 204,209,974 pounds, -valued at $3,113,898.
For the manufacture of glucose from corn, the grain is first softened by treatment, for two or three days, with water containing a small per centage of sulphurous acid; then coarsely ground; and then treated with 'starch-milk' (a mixture of starch and water) of such a density that the lighter embryos, or 'germs,' float on the surface, whence they are removed, while the heavier parts of the kernels sink to the bottom of the liquid. The 'germs' are dried and sold for stock-feed after the extraction by hydraulic pres sure of the oil they contain. This oil is found in commerce under the name of corn-oil or maize oil. The parts of the kernel that sink are finely ground. The starch is thus set free so that it can be separated from the ground grain by wash ing on sieves. It is afterwards purified by suc cessive mixing with water and sedimentation, or by deposition on 'starch-tables,' over which the washings from the sieves are allowed to flow. The starch, which is much heavier than water and the impurities from which it is to be freed, collects at the bottom of the settling-vats in a hard white layer which, when drained, is called `green starch' and is ready for conversion into glucose. The residue retained by the sieves and the nitrogenous matter, as well as the small amount of starch left in the wash waters, are col lected, pressed, dried, and sold for stock-feed. See GLUTEN MEAL AND GLUTEN FEED.
For converting the starch into glucose (hydro lysis), hydrochloric acid is now very generally used, although for certain products sulphuric acid in mixture with a minute quantity of nitric acid is used. The operation is conducted in steam heated, closed copper 'converters,' under a pres sure of two or three atmospheres (30 to 45 pounds per square inch). This high pressure
greatly lessens the quantity of acid and the time necessary. In the case of sulphuric acid, from one to three pounds are used per 100 pounds of dry starch; in the case of hydrochloric acid, only one-half to three-quarters of a pound of the con centrated acid is necessary. The starch is mixed with a considerable quantity of water before the acid is added; the time required for the conver sion varies from 10 to 30 minutes, according to the character of the required product, the time being much longer for solid starch-sugar than for syrupy glucose. By the action of the acid, the starch is first converted into dextrin and mal tose; by continued treatment, these bodies are changed to grape-sugar. The syrupy products con tain in some cases as much dextrin as grape sugar, and a very large percentage of maltose, while in some of the dry products only traces of dextrin and maltose are found. As the liquor comes from the 'converter,' the acid is neutral ized with chalk or marble dust, if sulphuric acid is used, or with soda if hydrochloric acid is used. In the former case, the gypsum or sulphate of lime formed crystallizes out, and is separated by filtration; in the case of hydrochloric acid, the neutralization product is sodium chloride (common salt), of which the quantity is so small that it does not injure the quality of the finished product. The neutralized liquid is decolorized by filtration through boneblack, and concen trated in vacuum evaporators to form a syrupy or a dry product, as may be desired. • Among the products of glucose factories, those of greatest commercial importance are 'mixing glucose,' used by syrup and molasses manipula tors; 'jelly glucose,' used in making jellies from evaporated apple-juice and other materials; 'con fectioners' glucose'; 'brewers' glucose,' used as a substitute for malt in brewing; and 'anhydrous starch-sugar.' Well-made glueoses must be re garded as a perfectly wholesome product, as they are composed of substances of frequent and abun dant occurrence in foods that have been in use from time immemorial, and which are similar to the products into which starch is normally trans formed by the processes of digestion. The objec tion to their use in the preparation of foods lies mainly in the fact that the consumer is fre quently misled in regard to the value of the com modities containing them, and that they are fre quently used in the fabrication of inferior, a-rtigeial or highly diluted, or otherwise adulter ated goods.
Consult: Wagner, A Practical Treatise on the Manufacture of Starch, Glucose, Starch-Sugar, and Dextrin, translated by Frankel and Hutton (Philadelphia, 1881) ; Hallock, Bibliography of (Washington, D. C., 1884).