—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 (P2O5), | 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 the contrary, contain the other elements that are in protein but do not have the sulfur element. They belong to that class of bodies which is known as simple amido compounds. All of these bodies are mixed together in meat juice or beef extract, and it is an important task of the chemist to separate them, both from an analytical point of view and the determination of their relative abundance. There is also another soluble or semisoluble protein substance in these extracts derived from the tendinous tissues and bones, namely, the gelatine or glue. This is quite a common product, being the soluble protein procured by the digestion of the tendons and bones. It is important, therefore, that the chemist should distinguish between the gelatine and the amido bodies. There is also a true and a false protein form of these soluble bodies, the true one being formed by natural proteolytic ferments and the false one being formed by heat or digestion under pressure of steam. The chemist should also be able to distinguish between the true extract formed directly from the meat and the yeast extract used as an adulteration.
It is not the purpose of this manual to enter into the details of how these different bodies may be distinguished from one another, as that is purely a chemical study. It is due, however, to the general reader that some explanation be given of the different classes of bodies which are contained in these extracts.
Relation between the Price of an Extract and its Nutritive Value.
—The studies made in the Bureau of Chemistry show that there is little relation between the price of a beef extract and its real nutritive value. In three cases of extract which are all well known brands and are of the thick or pasty variety, showing that a dissolved meat had been added to them, the average weight of a package costing 45 cents was only 55 grams, or nearly a cent a gram. In another three samples of extract, also well known brands, of the same pasty variety and costing little more per package, it was found that the weight of the more expensive variety was double that of the first, costing only one-half cent per gram. In the case of the liquid extracts where no pasty material is incorporated there is still greater variation in the relation of the price to the nutritive constituents. An extract which retails for one dollar per bottle contains 91.69 percent of water and only .42 percent of nitrogen. Another so-called meat extract which retails at 60 cents per bottle must have been wholly an artificial product, since it contained no creatin or creatinin at all. It was also preserved by the addition of alcohol and contained an artificial coloring matter.