The decorticated seeds of Hordeum distichon, Linné.
COMMON NAMES: Barley, Pearl barley.
ILLUSTRATION: Bentley and Trimen, Med. Plants, 293.
Botanical Source.—There are several kinds of barley, the more general ones being the following: Hordeum vulgare, Linné, has an erect, smooth, fistular culm or stem, from 2 to 4 feet in height, with alternate, carinate, lanceolate, linear, and roughish leaves; the sheaths are auriculate at the throat. The flowers are all hermaphrodite and awned; the spikes thick, and about 3 inches long; the spikelets 3, all fertile, 1-flowered, with an awn-like rudiment at the base of the upper paleae. Glumes 2, subulate, nearly equal, and awned. Paleae 2 and herbaceous; the lower one lance-ovate, concave, and long awned; the upper obtusely acuminate, and bicarinate. The stamens are 3 in number; ovary hairy at the apex. Stigmas 2, sessile, somewhat terminal, and feathery. Scales 2, ciliated. Caryopsis adhering to the paleae. Fruit or seeds in 4 rows (L.—W.).
Hordeum distichon, Linné, differs from the preceding by having a compressed spike or ear, with the lateral spikelets abortive and awnless; the spikelets on the edge only being fertile, and the fruit is disposed in 2 rows.
Hordeum hexastichon, Linné, has the fruit in 6 rows.
History and Description.—Barley is thought to be a native of central Asia, but the subject is involved in much uncertainty. The seeds are the parts employed. They are oblong-ovoid, with a furrow on one side running lengthwise, yellow outside, white internally, of a feeble odor, and a moderately saccharine taste. When the seeds are stripped of their husks, and made round by a particular process, it constitutes pearl barley (Hordeum Perlatum), which is the best form for use; when this is ground into a coarse flour it forms barley meal. Pearl barley occurs in subspherical or nearly ovoid grains, of a white, starchy aspect. Sometimes remaining portions of the husk give to it a yellowish cast. This is especially the case along the longitudinal groove. Its taste resembles that of the farinaceae in general. When the seeds are but partially decorticated it is known as hulled, Scotch, or pot barley. When the entire grain is moistened and exposed in mass to a summer temperature until it begins to germinate, and is then devitalized at a definite stage of the germinating process, by a stronger heat, it is converted into MALT, which is extensively employed in making ale, beer, and porter. During the process of making malt, the temperature rises appreciably, much carbon dioxide is given off, and the nitrogenized matter in the seeds undergoes a change, being in part converted into a peculiar ferment, called diastase. It has the power, peculiar to infusions of malt, of converting large quantities of starch into dextrin and a fermentable sugar, maltose. To obtain the greatest possible yield of diastase from a given amount of barley, at the same time reducing the loss of carbohydrates to a minimum, is the object of successful malting (see special works on brewing, etc., for details of this process).
Chemical Composition.—König (Nahrungs und Genussmittel, 3d ed., 1893, Vol. II, p. 467) gives the following percentage composition of barley seed, the results being the average of 766 recorded analyses of barley from many countries, including the United States: Water, 14.05; nitrogenous matter, 9.66; fatty matter, 1.93; sugar (maltose), 1.51; dextrin, 6.39; starch, 59.09; fibre, 4.95; ash, 2.42. The nitrogenous matter consists of gluten-casein, gluten-fibrin, mucedin, and albumin. The gliadin contained in wheat being absent, it is therefore impossible to obtain gluten from barley (see Avena). Albumin varies in barley from 0.5 to 1.77 per cent. As regards carbohydrates, sugar is stated to predominate over dextrin in American barley. Stellwaag (1886) found the fatty matter in barley to consist of 13.62 per cent free fatty acids (containing hordeic acid, or lauro-stearic acid of Beckmann, 1855), 71.78 per cent neutral fats, 4.24 per cent lecithin, and 6.08 per cent phytosterin.
J. C. Lermer, in 1863 (Wittstein's Vierteljahrsschrift, Vol. XII, p. 4), made a comparative analysis of barley seeds and the malt obtained therefrom, and observed a loss in starch of 14.57 per cent, and an increase of sugar by 2.03 per cent, also the fatty oil became reduced in quantity, while dextrin, cellulose, and proteids remained constant. Mr. Frank X. Moerk has more recently (Amer. Jour. Pharm., 1884, p. 366 and 465) made some diligent analyses of Canada barley as well as the malt prepared from it, to which articles the reader is referred. A peculiar, optically laevogyre carbohydrate, sinistrin (synanthrose), was found in hordeum by Kühnemann (1875). The ash of barley seeds contains chiefly phosphate of potassium, magnesium and calcium, and large amounts of silica (in the husks).
A peculiar principle has been found in barley seeds subsequent to the germinating process, by MM. Payen and Persoz, which they have named diastase. The same substance has likewise been found in the seeds of oats and wheat, and in the potato, but only after these have undergone germination. Diastase may be obtained by macerating ground malt in cold water, subjecting to pressure, and filtering and heating the liquid to the temperature of 70° C. (158° F.). Another nitrogenous body existing in the liquid is thus coagulated and removed. The liquid, being filtered again, is to be mixed with a sufficient quantity of alcohol to throw down the diastase. To obtain the diastase pure, it should be again dissolved in water, and thrown down by alcohol, and this ought to be repeated several times. Diastase thus obtained is solid, white, amorphous, insoluble in alcohol, but soluble in water and diluted alcohol. Its aqueous solution possesses neither acid or alkaline qualities, and has little taste. Diastase, after purification, is best obtained in the dry state by exposing it in thin layers to a current of air at about 44.3° C. (110° F.). Its aqueous solution is not precipitated, like that of starch, by lime, baryta, or acetate of lead; on keeping it becomes acid. Its most remarkable property is that of converting starch in the presence of water, at a temperature of about 50° C. (122° F.), into a peculiar sugar (maltose, C12H22O11) and dextrin. It has no action upon either gum or sugar, and yet 1 part of it added to 2000 parts of starch, suspended in water, causes the starch globules speedily to burst, the teguments separating from the contained granulose, which readily undergoes this extraordinary conversion without any perceptible difference in the weight of the substance employed. Diastase has also been called maltine. A second ferment, peptase, forms during malting, whose action is to change the proteids into peptones and parapeptones, the beer depending upon the latter bodies for its (asserted) nutritive qualities (Wagner, Handbuch der Chem. Technologie, 1889, p. 901).
The different kinds of beer, ale, and porter are made from malt, with the addition of hops and other articles. Malt has a sweetish, mucilaginous, rather agreeable taste. An infusion of it at 71.1° C. (160° F.) completes the conversion of the starch into sugar and gum; yeast being then added at a temperature between 15.5° and 26.6° C. (60° and 80° F.), vinous fermentation takes place, carbonic acid gas is disengaged and alcohol formed. The sugar is the source of the alcohol existing in malt liquors, while the gummy dextrin is the cause of their viscidity, and the permanence of their effervescence and frothy top.
Action, Medical Uses, and Dosage.—Pearl barley in decoction is nutritive and demulcent, and, on account of its mild and unirritating qualities, is much used as an article of diet for the sick and convalescent, acting at the same time, if the barley itself be swallowed, as a gentle aperient. The decoction is employed for suspending powdered drugs insoluble in water, and also as a drink in febrile diseases, catarrh, dysentery, inflammation of the bladder, gonorrhoea, and chronic mucous inflammations. Combined with hops, or in the form of beer, ale, or porter, it forms a valuable tonic in many chronic exhausting diseases, and in convalescence. From 2 to 4 ounces of malt boiled in a quart of water, afford a more demulcent and nutritious liquor than barley, and is consequently better adapted to cases requiring a sustaining course of treatment. In making the decoction of barley, 2 ounces must first be washed with cold water, and all extraneous matters removed, then place the barley in ½ pint of water, boil for a short time, strain off the water, and throw it away, as this is only employed to remove mustiness, or any disagreeable flavor which the barley may have acquired. To the barley thus prepared, add 4 pints of boiling water, boil down to 2 pints, and strain. The decoction may have other articles added in the course of its preparation, varied to suit the taste of the patient, as sugar, sliced figs, raisins, liquorice-root, etc. It may be drank freely.