Source, Etc

Ginger is the dried rhizome of Zingiber officinale, Roscoe (N.O. Scitamineoe), a reed-like plant producing leafy stems a metre high, springing from branching rhizomes. It is a native of Asia, but is cultivated in many tropical countries, notably in the West Indies, in India, Africa, and Japan.

There can be little doubt that ginger was well known in India as a spice from the earliest times. The Greeks and Romans were well acquainted with it, and its use spread in the ninth and tenth centuries through Europe to England. It was introduced by the Spaniards into the West Indies and Jamaica.

In Jamaica the plant is largely cultivated. It is propagated by dividing the rhizome into 'fingers,' each of which contains a bud, and planting these about a foot apart. They grow rapidly and flower in the autumn. When the aerial stems wither the rhizomes are dug up, freed from the roots, and washed. They are then peeled with a narrow-bladed knife, by which the layer of cork and part of the parenchyma of the cortex are removed, after which they are again washed, and dried in the sun. The product is known as unbleached Jamaica ginger. Although the use of a revolving drum for removing much of the peel and of a drying machine for rapidly drying the rhizomes has been suggested, this machinery does not appear to have been successfully introduced.

Much ginger is found in commerce from which the cork layer has not been removed, or which has been deprived of it on the flatter sides only. Such ginger is known as coated' 'or'unscraped,' whilst that which has been completely peeled is called ' scraped.' Sometimes, too, the rhizomes are treated with sulphurous acid or chlorine, or they are dusted over with calcium sulphate or carbonate which imparts to them a whitish appearance; ginger that has been treated so is termed ' bleached ' or ' limed ' ginger. In addition therefore to being obtained from different countries, ginger may vary in appearance according to the way in which it has been prepared for the market. As with nutmegs, limed ginger is undoubtedly less susceptible to the attacks of insect pests. Ginger is commonly washed and limed abroad, but is also usually rewashed and heavily limed in London.

Description

Unbleached Jamaica ginger, which is the official variety and the one that is most esteemed, occurs in flattened branched pieces technically termed 'races' or 'hands.' These vary in length, but average about 7 to 10 cm. From the upper surface of the main rhizome, which is usually straight, numerous branches about 3 cm. in length appear to arise and take an upward course; they are often slightly compressed laterally, enlarged near the rhizome, and, tapering abruptly, terminate in the remains of an undeveloped bud or a small depressed scar indicating the point of attachment of an aerial stem. The branches themselves also produce lateral branchlets. All these branches and branchlets arise from buds on the under surface of the rhizome in the axils of cataphyllary leaves. When the growth of the main axis is terminated by the production of an aerial shoot, one of these buds develops, curves upwards, and itself in due time produces an aerial shoot and develops a lateral branch. Each piece of the drug or ' hand ' is therefore a sympodial branch system.

The colour of the drug is usually pale yellowish buff; the surface is strongly striated or even fibrous, the fibres being the leaf-traces passing through the cortex to the leaves, and laid bare by the peeling of the rhizome. It breaks with a short, mealy or sometimes resinous fracture, short scattered fibres usually protruding from the fractured surface; these are the fibro-vascular bundles in the stele and cortex.

The smoothed transverse section exhibits a large stele which is sharply delimited by a fine yellow line from a narrow cortex, both stele and cortex containing numerous yellow oil-cells. No cork layer is to be discerned. Ginger has an agreeable aromatic odour and a strong pungent taste.

The student should observe

(a) The fibrous surface,

(b) The short fracture with protruding fibres and yellow oil-cells.

Microscopical Characters

The transverse section exhibits a large stele and a cortex free from cork. The parenchymatous cells, which are very abundant, have very thin walls; some contain yellow oleo-resin, but most are filled with starch. The fibro-vascular bundles in the stele contain a few reticulated vessels supported by sclerenchymatous fibres, which have rather thin walls and large cavities; abutting on the vessels are small cells filled with a dark brown secretion. The starch grains are typically Scitaminaceous; they are simple, 12, to 30 long, ovoid or sack-shaped and fiat, the hilum being at the extreme, pointed end.

Microscopical Characters 299Fig. 201.   Ginger. A, transverse section through the rhizome, magnified 3 diam. B, longitudinal section through a branch, natural size. o, cortex; v, endo dermis; b, stele. (Berg.)

Fig. 201. - Ginger. A, transverse section through the rhizome, magnified 3 diam. B, longitudinal section through a branch, natural size. o, cortex; v, endo-dermis; b, stele. (Berg).

Powdered ginger is characterised by the abundant typical starch, by the very thin walls of the parenchymatous cells, by the characteristic sclerenchymatous fibres, and by the oleo-resin cells; the latter are mostly broken, but the suberised walls are always to be found. It should contain no cork, no isodiametric sclerenchymatous cells, and no hairs. It should yield about 7 per cent. of extract to 90 per cent. alcohol, from 12 to 15 per cent. to cold water, not more than 6 per cent. of ash, and not less than 1 .5 per cent. of ash soluble in hot water. The last two data are specially useful in detecting adulteration with exhausted ginger.

Constituents

Ginger contains from 0.25 to 3 per cent. of a volatile oil possessing the aroma but not the pungency of the drug. The latter property is due to a yellowish oily body, gingerol, which is odourless, but has an intensely pungent taste. The drug contains in addition resin and abundance of starch. It yields from 3 to 5 per cent. of ash.

Gingerol is a mixture of homologous phenolic substances of the formulae C17H1604, C18H18O5, etc. Fixed alkalies, especially when heated, destroy its pungency but baryta water splits it up into fatty aldehydes, especially n-heptaldchyde and zingerone. Zingerone, C11H1403, is crystalline and pungent; it has a sweet odour and is allied to vanillin from which it has been synthe-sised; it is 4-hydroxy-3-methoxyphenylethylmethylketone. The pungency of gingerol is destroyed by boiling with 2 per cent. solution of potassium hydroxide, while that of capsaicin or paradol is scarcely affected.

Constituents 301Constituents 302Fig. 202.   Ginger. A, Jamaica; B, African: C, Cochin. All slightly reduced.

Fig. 202. - Ginger. A, Jamaica; B, African: C, Cochin. All slightly reduced.

Uses

Ginger is largely used as a condiment, and medicinally as a carminative and aromatic stimulant.

Varieties

The chief commercial varieties of ginger are Jamaica, Cochin, African, Japanese, and Bengal; an inferior grade of Jamaica ginger, obtained by allowing a part of the ' hand ' to remain in the ground after the first crop has been collected and grow without further attention, is known as 'ratoon' ginger.

Cochin ginger occurs in both the scraped and coated varieties; the latter bears on its ventral and dorsal surfaces, but not on the lateral, portions of a reddish grey cork, coarsely wrinkled both longitudinally and transversely. The lateral surfaces, that have been freed from the cork, are striated and of a rather paler colour. The drug is usually in smaller 'hands' than the Jamaica, the branches (' fingers ') are commonly shorter and thicker, and the aroma less agreeable.

African ginger is a coated ginger, the ventral and dorsal surfaces bearing patches of wrinkled cork of an earthy-brown colour. The cortical tissue that is exposed on the lateral surfaces is sometimes of a dingy grey colour and lighter than the cork, sometimes nearly black and then much darker. The drug in bulk is darker than Cochin ginger and appears discoloured from want of care in the preparation of it for the market. Although deficient in aroma, it is an exceedingly pungent ginger, in this respect excelling the Jamaica drug. It yields about 10 per cent. of alcoholic extract.

Bengal ginger is dark and partly coated; it resembles African.

Japanese ginger usually occurs in small flattened unscraped pieces; it is not produced by Z. officinale, as many of the starch grains are compound and the volatile oil differs in physical properties from that of Jamaica ginger; it has been referred to Z. Mioga, Roscoe.

Ratoon ginger is small, dull, dingy, greyish brown, and bears evidence of having been imperfectly peeled and carelessly cured. It is of inferior aroma and pungency.

Of all the commercial varieties of ginger, Jamaica is the most aromatic and African the most pungent.