Page:Foods and their adulteration; origin, manufacture, and composition of food products; description of common adulterations, food standards, and national food laws and regulations (IA foodstheiradulte02wile).pdf/124

 The quantity of total nitrogen in the form of meat base nitrogen in the best extracts reaches 50 percent. In one of the poorest it is 3.82 percent. The food value of the latter product might be greater than that of the former, but its cost of manufacture and its stimulating value are much less.

Creatin figures are very interesting and of much value in determining the source and value of an extract. Creatin is the principal amido-body found in meat, consequently we expect to find it or creatinin, its hydrated form, in still larger quantities in meat extracts. In several cases which came under our notice where the extract acted suspiciously, the creatin values were nil, and in such cases grave doubts exist as to the source of the extract. Our best extracts give high creatin as well as high meat base figures.

The xanthin bases and ammonia nitrogen figures present a variety of problems. While the xanthin bases are desirable constituents, ammonia in any amount is not. It is questionable whether the ammonia figures obtained by the magnesium oxid method do not give too high results (W. D. Bigelow).

Gelatine.—Gelatine is a substance obtained from the nitrogenous portions of bones, hide, horns, hoofs, connective tissue, tendons and other nitrogenous matter of the animal. One of the principal constituents of these bodies is a substance known as collagen. When this is heated either under pressure or without pressure it is changed to gelatine. Glue is unrefined gelatine or impure gelatine to which usually some substance has been added to increase its holding power. A type of gelatine known as isinglass is made from the bladders of sturgeons.

The general process of manufacturing gelatine is as follows (Whipple, Technology Quarterly, Vol. XV, No. 2, June, 1902):

"The hide scraps are first macerated and subjected to the action of a solution of lime or caustic soda in pits for two or three weeks. This dissolves most of the blood and saponifies the fats. The excess of lime or soda is then largely removed by washing and the solution steamed to dissolve the gelatine, but an excess of heat is avoided. Sulfurous acid is used to bleach the gelatine. When of sufficient strength, the gelatine is allowed to harden in molds or on slabs, and is ultimately dried in sheets on wire nets. Bone gelatine is made in a somewhat similar manner. The bones are crushed, boiled, treated with hydrochloric acid, and the gelatine is dissolved as before, washed, bleached and dried in sheets. The process requires a number of weeks."

Gelatine is also made from bones, fresh as well as old, and from the residues of bones used in the manufacture of buttons. The thin slices of the bones are treated with acid until all the phosphate of lime is extracted. They are then treated with lime and the gelatinous residue is then dissolved in warm water and purified for use.

The use of gelatine as a food has of late years become very common. The ease with which it can be made into jellies, the consistence which