_Peppermint_; F. _Menthe poivrée_; G. _Pfefferminze_.
=Botanical Origin=—_Mentha piperita_ Hudson (non Linn.), an erect
usually glabrous perennial, much resembling the Common Spearmint of the
gardens, but differing from it in having the leaves all stalked, the
flowers larger, the upper whorls of flowers somewhat crowded together,
and the lower separate. In the opinion of Bentham it is possibly a mere
variety of _M. hirsuta_ L., with which it can be connected by numerous
intermediate forms.
Peppermint rapidly propagates itself by runners, and is now found in
wet places in several parts of England, as well as on the Continent. It
is cultivated on the large scale in England, France, Germany, and North
America.
=History=—_Mentha piperita_ was first observed in Hertfordshire by
Dr. Eales, and communicated to Ray, who in the second edition of his
_Synopsis Stirpium Britannicarum_, 1696, noticed it under the name
of _Mentha spicis brevioribus et habitioribus, foliis Menthæ fuscæ,
sapore fervido piperis_; and in his _Historia Plantarum_[1763] as
“_Mentha palustris_ ... _Peper-Mint_.”[1764] Dale, who found the plant
in the adjoining county of Essex, states[1765] that it is esteemed a
specific in renal and vesical calculus; and Ray, in the third edition
of his _Synopsis_, declares it superior to all other mints as a remedy
for weakness of the stomach and for diarrhœa. Peppermint was admitted
to the London Pharmacopœia in 1721, under the designation of _Mentha
piperitis sapore_.
[1759] _Philosophical Magazine_, xiii. (1838) 444.
[1760] _Journ. of Chemical Society_, ii. (1854) 11.
[1761] Flückiger, _Pharm. Journ._ vii. (1876) 75.
[1762] Price from 1824 to 1839, 40_s._ to 48_s._ per lb.
[1763] Tomus iii. (1704) 284.
[1764] I have examined the original specimen still preserved among
Ray’s plants in the British Museum and find it to agree perfectly with
the plant now in cultivation.—D. H.
[1765] _Pharmacologiæ Supplementum_, Lond. 1705. 117.
The cultivation of peppermint at Mitcham in Surrey dates from about
1750,[1766] at which period only a few acres of ground were there
devoted to medicinal plants. At the end of the last century, above 100
acres were cropped with peppermint. But so late as 1805 there were no
stills at Mitcham, and the herb had to be carried to London for the
extraction of the oil. Of late years the cultivation has diminished in
extent, by reason of the increased value of land and the competition of
foreign oil of peppermint.
On the Continent Mentha Piperitis was grown as early as 1771 at
Utrecht; Gaubius[1767] appears to have been the first to notice
“_Camphora Europæa Menthæ Piperitidis_,” i.e. Menthol (see page 483).
In Germany peppermint became practically known in the latter half of
the last century, especially through the recommendation of Knigge.[1768]
=Description=—The rootstock of peppermint is perennial, throwing out
runners. The stem is erect, 3 to 4 feet high, when luxuriant somewhat
branched below with erecto-patent branches, firm, quadrangular,
slightly hairy, often tinged with purple. Leaves all stalked, the
stalks of the lower ½ to ¾ of an inch long, naked or nearly so, the
leaf lanceolate, narrowed or rather rounded towards the base, the
point narrowed out and acute, the lowest 2 to 3 inches long by about
¾ of an inch broad, naked and dull green above, paler and glandular
all over, but only slightly hairy upon the veins beneath; the teeth
sharp, fine, and erecto-patent. Inflorescence in a loose lanceolate
or acutely conical spike, 2 to 3 inches long by about ¾ of an inch
broad at the base, the lowest whorls separate, and usually the lowest
bracts leaf-like. Bracteoles lanceolate-acuminate, about equalling
the expanded flowers, slightly ciliated. Pedicels 1 to 1½ lines long,
purplish, glandular but not hairy. Calyx often purplish, the tube about
1 line long and the teeth ½ a line, the tube campanulate-cylindrical,
purplish, not hairy, but dotted over with prominent glands; the teeth
lanceolate subulate, furnished with short erecto-patent hairs. Corolla
reddish-purple about twice as long as the calyx, naked both within and
without. Nut smooth[1769] (_rugose_, according to our observation). The
odour and taste are strongly aromatic.
In var. 2. _vulgaris_ of Sole, _M. piperita_ β. Smith, the plant is
more hairy, with the spikes broader and shorter, or even bluntly
capitate. colourless, pale yellow, or greenish liquid, of sp. gr.
varying from 0·84 to 0·92. We learn from information kindly supplied
by Messrs. Schimmel and Co., Leipzig, that the best peppermint grown
in Germany, carefully dried, affords from 1 to 1·25 per cent. of oil.
It has a strong and agreeable odour, with a powerful aromatic taste,
followed by a sensation of cold when air is drawn into the mouth. We
find that the Mitcham oil examined by polarized light in a column 50
mm. long, deviates from 14°·2 to 10°·7 to the left, American oil 4°·3.
=Chemical Composition=—The constituent for the sake of which peppermint
is cultivated is the essential oil, _Oleum Menthæ piperitæ_, a
coloureless, pale yellow or greenish liquid, of sp. gr. varying from
0·84 to 0·92. We learn from information kindly supplied by Messrs.
Schimmel and Co., Leipzig, that the best peppermint grown in
Germany, carefully dried from 1 to 1·25 per cent of oil. It has
a strong and agreeable odour, with a powerful aromatic taste, followed
by a sensation of cold when air is drawn into the mouth. We find that
the Mitcham oil examined by polarized light in a column 50 mm. long,
deviates from 14·2° to 10·7° to the left, American oil 4·2°.
[1766] Lysons, _Environs of London_, i. (1800) 254.
[1767] _Adversariorum varii argumenti liber unus_, Leidae, 1771. 99.
[1768] _De Menthâ Piperitide Commentatio_, Erlangæ, 1780.
[1769] This description is borrowed from Mr. Baker’s paper on the
English Mints, referred to at page 480, note 1.
When oil of peppermint is cooled to -4° C., it sometimes deposits
colourless hexagonal crystals of _Peppermint Camphor_, C₁₀H₁₉OH,
called also _Menthol_. We have never observed it, nor are we aware
that menthol has been noticed in America, but it is largely afforded
by eastern mints, and found in commerce under the name of _Chinese_
or _Japanese Oil of Peppermint_,[1770] either liquid, and easily
depositing the camphor, or also forming a crystalline mass impregnated
with the liquid oil.
Pure menthol has the exquisite odour and taste of peppermint; it
forms hexagonal crystals, melting at 42° C., and boiling at 212°
C. By distilling menthol with P₂O₅ it yields menthene, C₁₀H₁₈, a
levogyrate liquid, boiling at 163°, the peculiar odour of which reminds
of peppermint.[1771] The Chinese crystallized oil of peppermint has
sometimes a bitterish after-taste and an odour similar to that of
spearmint, but by recrystallization it assumes the pure flavour.
The liquid part of the oil of peppermint has not yet been thoroughly
investigated; it appears to consist chiefly of the compound C₁₀H₁₈O.
Upon the liquid portions depend the remarkable colorations which the
oil of peppermint is capable of assuming. If 50 to 70 drops of the
crude oil are shaken with one drop of nitric acid, sp. gr. about 1·2,
the mixture changes from faintly yellowish to brownish, and, after
an hour or two, exhibits a bluish, violet or greenish colour; in
reflected light, it appears reddish and not transparent. The colour
thus produced lasts a fortnight. We have thus examined the various
samples of peppermint oil at our command, and may state that the finest
among them assume the most beautiful coloration and fluorescence,
which, however, shows very appreciable differences. An inferior oil
of American origin was not coloured; and a very old sample of an
originally excellent English oil was likewise not coloured by the test.
Menthol is not altered when similarly treated.[1772] The nitric acid
test is not capable of revealing adulterations of peppermint oil, for
the coloration takes place with an oil to which a considerable quantity
of oil of turpentine has been added.
[1770] The Chinese oil is distilled at Canton, and was exported from
Canton in 1872 to the extent of 800 lbs.; it was valued at about 30s.
per lb.—See also Flückiger in _Pharm. Journ._ Oct. 14, 1871. 321. As to
Japan we are informed that there are large plantations of peppermint;
the oil “Hakano Abura” is exported from Hiogo and Osaka, but frequently
adulterated. Mr. Holmes informed me (1879) that he found the mother
plant coming nearest to _Mentha canadensis_.—F. A. F..
[1771] On Japanese Peppermint Camphor see Beckett and Alder Wright,
_Yearbook of Pharm._ 1875. 605.
[1772] _Pharm. Journ._ Feb. 25, 1871. 682.
Remarkable colorations of a different hue are also displayed by the
various kinds of oil of peppermint if other chemical agents are
mixed with it. Thus green or brownish tints are produced by means
of _anhydrous_ chloral; the oil becomes bluish or greenish or
rose-coloured if shaken with a concentrated solution of bisulphite
of sodium. It is worthy of note that oils of different origin, which
cannot be distinguished by means of nitric acid, exhibit totally
different colorations if mixed with either of the liquids just named,
or with vapour of bromine. This behaviour may be of some use in the
examination of commercial sorts of peppermint oil.
As to bisulphite of sodium, it yields a solid compound with certain
kinds of peppermint oil, which we have not yet examined.
=Production and Commerce=—In several parts of Europe, as well as in
the United States, peppermint is cultivated on the large scale as a
medicinal plant.
In England the culture is carried on in the neighbourhood of Mitcham
in Surrey, near Wisebeach in Cambridgeshire, Market Deeping in
Lincolnshire, and Hitchin in Hertfordshire.
At Mitcham in 1850 there were about 500 acres under cultivation; in
1864 only about 219 acres.[1773] At Market Deeping there were in 1871
about 150 acres cropped with peppermint. The usual produce in oil
may be reckoned at 8 to 12 lb. per acre. The fields of peppermint
at Mitcham are level, with a rich, friable soil, well manured and
naturally retentive of moisture. The ground is kept free from weeds,
and in other respects is carefully tilled. The crop is cut in August,
and the herb is usually allowed to dry on the ground before it is
consigned to the stills. These are of large size, holding 1000 to
2000 gallons, and heated by coal; each still is furnished with a
condensing worm of the usual character, which passes out into a small
iron cage secured by a padlock, in which stands the oil separator. The
distillation is conducted at the lowest possible temperature. The water
that comes over with the oil is not distilled with another lot of herb,
but is for the most part allowed to run away, a very little only being
reserved as a perquisite of the workmen. The produce is very variable,
and no facilities exist for estimating it with accuracy.[1774] It is
however stated that a ton of dried peppermint yields from 2½ to 3½
pounds of oil, which equals 0·11 to 0·15 per cent. But we have been
assured by a grower at Mitcham that the yield is as much as 6 pounds
from a ton, or 0·26 per cent.
At Mitcham and its neighbourhood two varieties of peppermint are at
present recognized, the one being known as _White Mint_, the other as
_Black Mint_, but the differences between the two are very slight. The
Black Mint has _purple_ stems; the White Mint, _green_ stems, and as
we have observed, leaves rather more coarsely serrated than those of
the Black. The Black Mint is more prolific in essential oil than the
White, and hence more generally cultivated; but the oil of the latter
is superior in delicacy of odour and commands a higher price. White
Mint is said to be principally grown for drying in bundles, or as it is
termed “_bunching_.”
[1773] _Pharm. Journ._ x. (1851) 297. 340; also Warren in _Pharm.
Journ._ vi. (1865) 257. To these papers and to personal inquiries we
are indebted for most of the particulars relating to peppermint culture
at Mitcham.
[1774] Only the larger growers have stills. These they let to smaller
cultivators who pay so much for distilling a charge, _i.e._ whatever
the still can be made to contain, without reference to weight. Hence
the dried herb is preferred to the fresh, as a larger quantity can be
distilled at one time.
Peppermint is grown on a vastly larger scale in America, the localities
where the cultivation is carried on being Southern Michigan, Western
New York, and Ohio. In Michigan where the plant was introduced in
1855, there were in 1858 about 2100 acres devoted to its growth, all
with the exception of about 100 acres being in the county of St.
Joseph, where there are about 100 distilleries. The average produce
of this district was estimated in 1858 at 15,000 lb.; but the yield
fluctuates enormously, and in the exceptionally fine season of 1855 it
was reckoned at 30,000 lb. We must suppose that it is sometimes much
larger, for we have been informed by Mr. H. G. Hotchkiss, of Lyons,
Wayne County, State of New York, one of the most well-known dealers, in
a letter under date Oct. 10, 1871, that the quantity sent out by him
in the previous year reached the enormous amount of 57,365 lb. It is
further stated by the official statistics of Hamburg for the year 1876
that this port received 25,840 lb. of peppermint oil from the United
States and 14,890 lb. from Great Britain.
From the statistics quoted by Stearns[1775] it would appear that the
produce of oil per acre is somewhat higher in America than in England,
but from various causes information on this head cannot be very
reliable.
Peppermint is cultivated at Sens in the department of the Yonne in
France[1776] and in Germany in the environs of Leipzig, where the
little town of Cölleda produces annually as much as 40,000 cwts. of the
herb.
The annual crop of the world is supposed to yield 90,000 lb. of
peppermint oil.[1777]
Peppermint oil varies greatly in commercial value, that of Mitcham
commanding twice or three times as high a price as the finest American.
Even the oil of Mitcham is by no means uniform in quality, certain
plots of ground affording a product of superior fragrance. A damp
situation or badly drained ground is well known to be unfavourable to
the quantity and quality of oil.
The presence of weeds among the peppermint is an important cause of
deterioration to the oil, and at Mitcham some growers give a gratuity
to their labourers to induce them to be careful in throwing out other
plants when cutting the herb for distillation. One grower of peppermint
known to us was compelled to abandon the cultivation, owing to the
enormous increase of _Mentha arvensis_ L. which could not be separated,
and which when distilled with the peppermint ruined the flavour of
the latter. In America great detriment is occasioned by the growth of
_Erigeron canadensis_ L. Newly cleared ground planted with peppermint
is liable to the intrusion of another plant of the order Compositæ,
_Erechtites hieracifolia_ Raf., which is also highly injurious to the
quality of the oil.[1778]
=Uses=—A watery or spirituous solution of oil of peppermint is a
grateful stimulant, and is a frequent adjunct to other medicines. Oil
of peppermint is extensively consumed for flavouring and cordials.
[1775] To whose paper _On the Peppermint Plantations of Michigan_ in
the _Proceedings of the Americ. Pharm. Assoc._ for 1858, we owe the
few particulars for which we can here afford space.—To be farther
consulted, same _Proceedings_, 1876. 828.
[1776] _Journ. de Pharm._ viii. (1868) 130.—Abstract from Roze, _La
Menthe poivrée, sa culture en France, ses produits, falsifications de
l’essence et moyens de les reconnaître_, Paris, 1868. 43 pages.
[1777] Todd, _Proceedings Am. Ph. Ass._ 1876, 828.
[1778] Maisch, _American Journ. of Pharm._ March 1870. 120.