This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The sweet almond is the seed of Prunus Amygdalus, Stokes, var. dulcis, Baillon (N.O. Bosaceoe). The tree is a native probably of Persia and Asia Minor, but is cultivated in all the countries that border on the Mediterranean, and produces ripe fruit even in the south of England. The seeds - almonds - as well as the oil pressed from them, were well known in Greece and Italy long before the Christian era; during the Middle Ages they became an important article of commerce in Central Europe.
The almond tree produces in early spring handsome pink flowers, which are succeeded by green, velvety, drupaceous fruits about the size of a plum, but differing from it in possessing a firm, felt-like mesocarp. As the fruit ripens the mesocarp gradually dries, splits, and falls away (or is easily removed), carrying the thin epicarp with it, and leaving the seed, enclosed in the endocarp or shell, attached to the tree. Sometimes almonds are exported enclosed in their endocarps (almonds in the shell), but more frequently the shells are broken and the seeds alone exported.
Sicily and southern Italy are the chief almond-producing countries. Spain, Portugal, the south of France, the Balearic Islands, and Morocco also export considerable quantities.
The endocarp or shell of the almond is yellowish buff in colour and flattened-ovoid in shape, the outer surface being usually pitted with small holes; frequently it has a more or less fibrous nature. Sometimes it is thin and friable (soft-shell almonds), sometimes extremely hard and woody (hard-shell almonds). The seed is rounded at one end, pointed at the other, and covered with a thin, brown, scurfy seed-coat. The hilum is long, and situated on the acute edge of the seed near the pointed end; the raphe is distinguishable as a dark line running from the hilum to the broad end of the seed, where it terminates in a dark spot, the chalaza, from which a number of veins radiate.
Fig. 91. - Almond: a, Sweet Almond; b, same, cut longitudinally, c, Bitter Almond; d, same, cut transversely. Natural size. (Holmes).
After maceration in water the thin seed-coat is easily separated; the kernel consists of two, large plano-convex, oily cotyledons, enclosing a small plumule and radicle. The seed is exalbuminous, there being no endosperm. Sweet almonds have a bland nutty taste, and yield, when triturated with water, a white emulsion destitute of any marked odour. The latter character is important, as it is the only definite one by which the sweet almond can be distinguished from the bitter.
The student should observe
(a) The elongated shape (of the Jordan almond),
(b) The thin seed-coats and two cotyledons without endosperm,
(c) The bland taste and odour (of the emulsion).
Sweet almonds contain from 40 to 46 per cent, of a bland fixed oil, which can be obtained by pressing the seeds, and about 20 per cent, of proteids, amongst which is included a mixture of enzymes known as emulsin. They contain also a little sucrose, gum, and asparagin.
Emulsin may be isolated by infusing powdered blanched sweet almonds in water, straining, acidifying with glacial acetic acid, filtering, and precipitating with four volumes of alcohol. It contains lactase, β-glucosidase, β-galactosidase, and cellase (cellobiase), and is capable of hydrolysing a large number of (lsevo-rotatory) glucosides.
Almond oil is pressed both from the sweet and the bitter almond. It consists chiefly of olein accompanied by a small proportion of linolein, etc.; it is characterised by its specific gravity (0.915 to 0.920), by the quantity of iodine it is capable of combining with (93 to 100 per cent.), by the melting-point of the mixed fat acids obtainable from it (not over 15°), and by the whitish colour when shaken with a cooled mixture of equal parts by weight of sulphuric acid, fuming nitric acid, and water. Drying oils such as cotton seed, etc, combine with larger proportions of iodine; sesame, ground nut, and certain other oils yield fat acids, melting at a much higher temperature. Apricot kernel oil gives a reddish colour with the nitric acid test.
Jordan (French ' jardin ') almonds, exported from Malaga, constitute the official variety; they are characterised by their narrow, elongated shape and thin skin.
Valencia: these are broadly ovoid, shorter, and have a thicker, dusty brown, scurfy coat.
Sicilian and Barbary: both of these closely resemble the Valencia, but are rather smaller; they occasionally contain admixtures of bitter almonds.
East Indian: these are the seeds of the cashew nut Anacardium occidentale, Linne (N.O. Anacardiaceoe); the pericarp of the fruit contains an oily, vesicating liquid, cardol, but the seeds are edible.
Sweet almonds are demulcent and nutritive. They are used as a non-starchy food for diabetic patients.