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/120

 advantage over fresh meat. On the contrary, for theoretical and practical reasons, it is certain that it is less valuable.

Composition of the Ash of Meat Juice and Meat Broth.—The principal mineral component of the natural juice of meat broth or meat extract is phosphate of potassium, though there are also small quantities of magnesium and smaller quantities of calcium present. In addition to this there is a certain quantity of common salt present, which is determined, however, largely by the method of preparation. The following analysis shows the composition of the ash of a meat juice to which little or no common salt has been added:

Potassium (K),                    34.40 percent Sodium (Na),                       9.70    " Calcium (Ca),                        .36    " Magnesium (Mg),                    2.55    " Phosphoric acid (P_{2}O_{5}),      27.00    "

Other constituents are not determined in this analysis. The phosphate of potassium may therefore be regarded as the principal natural ash constituent of meat extract and meat juice. (Zeitschrift für Biologie, Vol. XII, 1876.)

Adulteration of Meat Extract.—The principal adulterations of meat extract have already been mentioned. The substances used in preserving it are of the greatest hygienic consequence. These are chiefly salt and glycerol or alcohol. The use of all of these substances is reprehensible. Fortunately they are seldom used. Another adulteration which has been practiced is mixing the meat extract with extracts of yeast. The extract of yeast has valuable dietetic properties and contains the active principles of fermentation. It also resembles, in many respects, physically and chemically, the extract of meat, and can, therefore, be mixed with meat extract, and, being a cheaper article, forms a mixture which can be sold at a greater profit. The presence of yeast extract in meat extract can easily be determined by treating the mixture with a strong solution of sulfate of zinc and filtering. In meat extract the filtrate obtained is always quite clear, but when a yeast extract is present the filtrate is turbid.

Active Principles Contained in Meat Extract.—Attention has already been called to some of the more important active principles, namely, meat bases which form a valuable portion of meat extract. There are various forms of nitrogenous bodies, however, besides meat bases, which become soluble naturally in meat or by the treatment of meat with digestive ferments. Lean meat, as is well known, consists almost exclusively of protein matter and water. This protein matter is principally insoluble. Under the action of digestive ferments the protein of meat becomes broken up into more soluble bodies, known as albumoses, proteoses and peptones,—the latter being the final product of solution. These bodies are still true protein bodies containing the elements of sulfur as one of their essential constituents. The meat bases, on