Ginger contains a great deal of alcohol. This fact accounts for the formation of the so-called ginger habit to which the victim becomes a slave as to the whiskey, opium, or tobacco habit. Indulgence in this habit is more dangerous because ginger is supposed to be harmless.
A careful qualitative examination of the character of the extracts at times may reveal the presence of an adulterant, but the chief dependence is examination under the microscope. The microscope, however, will not reveal the presence of exhausted ginger, and a careful study of the effect of exhaustion on the proximate composition of the ground root is, therefore, desirable. It would naturally increase the relative percentage of fiber and albuminoids and starch, and diminish that of the extract matter.
There is a variety of ginger known and cultivated by the Chinese under the name of Galangal A. officinarom. It is very thick and slightly flattened and is prized by the Siamese and Chinese as a substitute for ginger. In Siam it is known as Alpinia. There is also a variety found and cultivated in Siam similar to Alpinia allughas, called luk reu or bastard cardamom, which has the cardamom-like fruit. Ginger usually comes to New York in 110 to 120-pound bags and 130-pound barrels.
The yield of oil from ginger is from 1.9 to 2.7 per cent., having a specific gravity at 15 degrees C. of 0.880 to 0.885, and an optical rotation of 25 to 40 degrees in a 100-millimeter tube.
The chemical composition of ginger oil remains unknown, but it is known to contain camphene and other ingredients; its complex nature is indicated by the wide range of its boiling point.
When distilled, after drying over CaCl2, the boil begins to pass over at 140 degrees C., accompanied by a few drops of aqueous fluid, the temperature constantly and rapidly rising to about 240 degrees, the chief portion of the oil coming over between 240 degrees and 270 degrees C. and a little passes over between 270 degrees and 300 degrees, but evidently accompanied by decomposition products, a transparent, brown, tenacious, semi-solid residue remaining in flask.
The lower boiling products retain the ginger aroma, which is noted when diluted with spirits, and are much more soluble in rectified spirits than higher fractions. Oil of ginger is yellow in color and its odor is intensely like that of the root; that of Jamaica is the most fragrant, but has not the burning, pungent taste of ginger, which is due to gingerol, the active pungent principle of the root.
Gingerol exists in the dried rhizomes to the extent of from 0.600 to 1.450 per cent. It is of a pale straw color and odorless, with a pungent, bitter taste. It is soluble in alcohol in even 50 per cent. dilution; it is also soluble in benzene, volatile oils, carbon disulphide, solution of potash and ammonia, and glacial acetic acid, and very slightly soluble in petroleum ether, consisting of resin, starch, mucilage, and paraffine, organic acids, oxalic acids as CaC2C4 cellulose albuminoids, etc., which constituents of ginger are found to be odorless and tasteless.
The alcoholic solution is neutral in reaction and gives no precipitate with the acetates of lead nor with lime, and does not yield glucose when treated with diluted sulphuric acid. Strong sulphuric acid dissolves it with the production of a brown color; hydrochloric acid does not affect it. Nitric acid converts it into a blood-red resinous substance.
Adulterants of ginger are sago, tapioca, flour of rice, wheat, and potatoes, Cayenne and mustard hulls, and tumeric and exhausted ginger. The foreign starches, Cayenne, and mustard hulls are easily detected, but the tumeric (East India arrowroot) cells, from their resemblance to the resin globules of the ginger, are most confusing. For detection of exhausted ginger recourse must be had to proximate analysis.