_Vanilla_;[2444] F. _and_ G. _Vanille_.
=Botanical Origin=—_Vanilla planifolia_ Andrews—Indigenous to the hot
regions (_tierra caliente_) of Eastern Mexico, diffused by cultivation
through other tropical countries. The plant, which is rather fleshy
and has large greenish inodorous flowers,[2445] grows in moist, shady
forests, climbing the trees by means of its aërial roots.
=History=—The Spaniards found vanilla in use in Mexico as a condiment
to chocolate, and by them it was brought to Europe; but it must have
long remained very scarce, for Clusius, who received a specimen in
1602 from Morgan, apothecary to Queen Elizabeth, described it as
_Lobus oblongus aromaticus_, without being in the least aware of
its native country or uses.[2446] In the _Thesaurus_ of Hernandez
there is a figure and account of the plant under the name of _Araco
aromatico_.[2447]
In the time of Pomet (1694) vanilla was imported by way of Spain, and
was much used in France for flavouring chocolate and scenting tobacco.
It had a place in the materia medica of the London Pharmacopœia of
1721, and was well known to the druggists of the first half of the 18th
century, after which it seems to have gradually disappeared from the
shops. Of late times it has been imported in great abundance, and is
now plentifully used, not only by the chocolate manufacturer, but also
by the cook and confectioner.
=Cultivation=—The culture of vanilla is very simple. Shoots about
three feet long having been fastened to trees, and scarcely touching
the ground, soon strike roots on to the bark, and form plants which
commence to produce fruit in three years, and remain productive for
thirty to forty.
The fertilization of the flower is naturally brought about by insect
agency. This was practised as early as 1830 by Neumann in the Jardin
des Plantes at Paris, and in 1837 by Morren,[2448] the director of the
Botanical Garden of Liège, since which the production of the pods has
been successfully carried on in all tropical countries[2449] without
the aid of insects. Even in European forcing houses the plant produces
fruits of full size, which for aroma bear comparison with those of
Mexico.
In vanilla plantations the pods are not allowed to arrive at complete
maturity, but are gathered when their green colour begins to change.
According to the statements of De Vriese,[2450] they are dried
by a rather circuitous process, namely by exposing them to heat
alternately uncovered, and wrapped in woollen cloths, whereby they are
artificially ripened, and acquire their ultimate aroma and dark hue.
They are then tied together into small bundles.
[2444] Diminutive of the Spanish _vaina_, a pod or capsule.
[2445] Beautifully figured in Berg and Schmidt’s _Offizinelle
Gewächse_, xxxiii. tab. _a_ and _b_ (1862).
[2446] _Exotica_ (1605) lib. iii. c. 18. 72.
[2447] _Rerum Medicarum Novæ Hispaniæ Thesaurus_, Romæ, 1651. p.
38.—The original drawing was one of a series of 1200, executed at
great cost in Mexico by order of the King of Spain during the previous
century.
[2448] _Ann. of Nat. Hist._ iii. (1839) 1.
[2449] In Réunion it was introduced in 1839 by Perrottet, the
well-known botanist. See Delteil, _Etude sur la Vanille_, Paris, 1874.
54 pages, 2 plates.
[2450] _De Vanielje_, Leyden, 1856. 22, with figures.
In Réunion the drying of the pods is performed since 1857 by dipping
them previously in boiling water.
=Description=—The fruit when fresh is of the thickness of the little
finger, obscurely triquetrous, opening longitudinally by two unequal
valves. It is fleshy, firm, smooth, and plump; when cut transversely
it exudes an inodorous slimy juice, abounding in spiculæ of oxalate of
calcium.[2451] It is one-celled, with a three-sided cavity, from each
wall of which projects a two-branched placenta, each branch subdividing
into two backward-curling lobes. There are thus in all 12 ridges, which
traverse the fruit lengthwise, and bear the seeds. Fine hair-like
papillæ line as a thick fringe the three angles of the cavity, and
secrete the odorous matter, which after drying is diffused through the
whole pod. The papillæ likewise contain drops of oil, which is freely
absorbed by the paper in which a pod is wrapped. That the odorous
matter is not resident in the fleshy exterior mass we have ascertained
by slicing off this portion of a fresh fruit and drying it separately;
the interior alone proved to be fragrant.
The vanilla of commerce occurs in the form of fleshy, flexible,
stick-like pods, 3 to 8 inches long, and ³/₁₀ to ⁴/₁₀ of an inch wide,
of a compressed cylindrical form, attenuated and hooked at the stalk
end. The surface is finely furrowed lengthwise, shining, unctuous, and
often beset with an efflorescence of minute colourless crystals. The
pod splits lengthwise into two unequal valves, revealing a multitude of
minute, shining, hard, black seeds of lenticular form, imbedded in a
viscid aromatic juice.
The finest vanilla is the Mexican. _Bourbon Vanilla_, which is the
more plentiful, is generally shorter and less intense in colour, and
commands a lower price.
=Microscopic Structure=—The inner half of the pericarp contains about
20 vascular bundles, arranged in a diffuse ring. The epidermis is
formed of a row of tabular thick-walled cells, containing a granular
brown substance. The middle layer of the pericarp is composed of large
thin-walled cells, the outer of which are axially extended, while those
towards the centre have a cubic or spherical form. All contain drops of
yellowish fat and brown granular masses, which do not decidedly exhibit
the reaction of tannin. The tissue further encloses needles of oxalate
of calcium and prisms of vanillin.
On the walls of the outer cells of the pericarp[2452] are deposited
spiral fibres, which occur still more conspicuously in the aërial roots
and in the parenchyme of the leaves of other orchids. The placentæ are
coated with delicate, thin-walled cells.
[2451] This juice like that of the squill has an irritating effect on
the skin, a fact of which the cultivators in Mauritius are well aware.
[2452] Vanilla grown in Europe is devoid of such cells. We can fully
corroborate this statement (first made by Berg) from the examination
of very aromatic pods produced in 1871 at Hillfield House, Reigate.
We have even failed in finding those cells in any vanilla of recent
importation (1878).
=Chemical Composition=—Vanilla owes the fragrance for which it is
remarkable to _Vanillin_, which is found in a crystalline state in the
interior or on the surface of the fruit, or dissolved in the viscid
oily liquid surrounding the seeds. It was formerly regarded as cinnamic
or benzoic acid, and then as cumarin, until Gobley (1858) demonstrated
its peculiar nature.
The admirable researches of Tiemann and Haarmann performed in
Hofmann’s laboratory at Berlin (1874-1876) have shown that vanillin is
constituted according to the formula
{OCH₃
C₆H₃ {OH.
{CHO
It is the aldehyde. It is the aldehyde of methyl-protocatechuic acid,
and like other aldehydes yields a crystallized compound with the
bisulphites of alkalis. This is obtained by shaking an ethereal extract
(_e_) of vanilla, with a saturated solution of bisulphite of sodium.
The vanillin compound remaining in aqueous solution is mixed with
sulphuric acid and ether; the latter on evaporation affords crystals of
vanillin. They melt at 81°, and may be sublimed by cautiously heating
them. Vanillin is but sparingly soluble in cold water, and requires
about 11 parts of it at 100° C. for solution; it strikes a fine dark
violet with perchloride of iron.
The said chemists have further demonstrated that vanillin may be formed
artificially. In the sapwood of pines there occurs a substance called
_Coniferin_, C₁₆H₂₂O₈ + 2 H₂O, first observed in 1861 by Hartig. By
means of emulsin coniferin taking up H₂O, can be resolved into sugar
and another crystallizable substance:—C₁₆H₂₂O₈ + H₂O = C₆H₁₂O₆ +
C₁₀H₁₂O₃. The second substance thus derived may be collected by means
of ether, which dissolves neither coniferin nor sugar. By oxidizing it,
or coniferin itself, by bichromate of potassium and sulphuric acid,
_Vanillin_ is obtained. The latter has been for sometime manufactured
in that way by Tiemann, but now eugenol (see p. 285) is used for that
purpose. Another source for vanillin is benzoin (p. 409).
The amount of vanillin was stated by Haarmann and Tiemann to be 1·69
per cent. in Mexican vanillin, from 1·9 to 2·48 in the Bourbon variety,
and 2·75 in that from Java. The so-called _Vanillon_ affords only 0·4
to 0·7 per cent. of vanillin.
From the above-mentioned ethereal solution (e), after it has been
deprived of vanillin, vanillate of sodium may be removed by a dilute
solution of carbonate of sodium. On acidulating the aqueous solution
crystals of _vanillic acid_,
{OCH₃
C₆H₃ {OH are precipitated.
{COOH
If the ether of the solution (_e_), after it has been treated with
carbonate of sodium, is allowed to evaporate, a mixture of fatty
substances and a resin are obtained. The latter has a peculiar odour,
somewhat suggestive of castoreum; vanillic acid is almost inodorous.
Leutner (1872) also found in vanilla fatty and waxy matter 11·8, resin
4·0, gum and sugar 16·5 per cent.; and obtained by incineration of the
drug 4·6 per cent. of ash.
=Production and Commerce=—The chief seats of vanilla-production in
Mexico are the slopes of the Cordilleras, north-west of Vera Cruz,
the centre of the culture being Jicaltepec, in the vicinity of
Nautla.[2453] The finest specimens were contributed in 1878 to the
Paris Exhibition from Agapito, Fonticilla, Misantla, Papantla, also
from Teziutlan, province of Puebla. There are likewise “_Baynillales_,”
plantations of vanilla, on the western declivity of the Cordilleras
in the State of Oaxaca, and in lesser quantity in those of Tabasco,
Chiapas, and Yucatan. The eastern parts of Mexico exported in 1864, by
way of Vera Cruz and Tampico, about 20,000 kilo. of vanilla, chiefly to
Bordeaux. Since then the production seems to have much declined, the
importation into France having been only 6,896 kilo. in 1871, and 1,938
in 1872.[2454]
[2453] _Culture du vanillier au Mexique_, in the _Revue Coloniale_,
ii. (1849) 383-390; also J. W. von Müller, _Reisen in ... Mexico_, ii.
(Leipzig, 1864) 284-290.
[2454] _Documents Statistiques réunis par l’Administration des Douanes
sur le Commerce de la France_, année 1872, p. 64.
The cultivation of vanilla in the small French colony of Réunion or
Bourbon (40 miles long by 27 miles broad), introduced by Marchant in
1817 from Mauritius, has of late been very successful, notwithstanding
many difficulties occasioned by the severe cyclones which sweep
periodically over the island, and by microscopic fungi which greatly
injured the plant. In 1849 the export of vanilla from Réunion was 3
kilogrammes, in 1877 it reached 30,973 kilogrammes. The neighbouring
island of Mauritius also produces vanilla, of which it shipped in 1872
7,139 lbs., in 1877 the quantity was 20,481 lbs. There is likewise a
very extensive cultivation of vanilla in Java.
Vanilla comes into the market chiefly by way of France, which country,
according to the official statistics, imported in 1871, 29,914 kilo.
(65,981 lbs.); in 1872, 26,587 (58,643 lbs.); in 1874 that quantity
amounted to 34,906 kilo.
=Uses=—Vanilla has long ceased to be used in medicine, at least in this
country, but is often sold by druggists for flavouring chocolate, ices,
creams, and confectionery.