_White Mustard_; F. _Moutarde blanche ou Anglaise_; G. _Weisser Senf_.
=Botanical Origin=—_Brassica alba_ Hook. f. et Th. (_Sinapis alba_ L.)
This plant appears to belong to the more southern countries of Europe
and Western Asia. According to Chinese authors[294] it was introduced
into China from the latter region. Its cultivation in England is of
recent introduction, but is rapidly extending.[295] The plant is not
uncommon as a weed on cultivated land.
[292] The best _Flour of Mustard_ such as is made by the large
manufacturers, contains nothing but brown and white mustard seeds. But
the lower and cheaper qualities made by the same firms contain flour,
turmeric, and capsicum. Unmixed flour of Black Mustard is however kept
for those who care to purchase it.
[293] _Annual Statement of the Trade and Navigation of British India_,
Calcutta, 1872. 62.
[294] Bretschneider, _Study of Chinese Botan. Works_, 1870. 17.
[295] Morton’s _Cycloped. of Agriculture_, ii. (1855) 440.
=History=—White mustard was used in former times indiscriminately
with the brown. In the materia medica of the _London Pharmacopœia_
of 1720 the two sorts are separately prescribed. The important
chemical distinction between them was first made known in 1831 by
Boutron-Charlard and Robiquet.[296]
=Production=—White mustard is grown as an agricultural crop in Essex
and Cambridgeshire.
=Description=—_Brassica alba_ differs from _B. nigra_ in having the
pods bristly and spreading. They are about an inch long, half the
length being occupied by a flat veiny beak. Each pod contains 4 to 6
yellowish seeds about ¹/₁₂ of an inch in diameter and ⅒ of a grain in
weight. The brittle, nearly transparent and colourless testa encloses
an embryo of a bright pure yellow and of the same structure as that
of black mustard. The surface of the testa is likewise pitted in a
reticulate manner, but so finely that it appears smooth except under a
high magnifying power.
When triturated with water the seeds form a yellowish emulsion of very
pungent taste, but it is inodorous and does not under any circumstances
yield a volatile oil. The powdered seeds made into a paste with cold
water act as a highly stimulating cataplasm. The entire seeds yield to
cold water an abundance of mucilage.
=Microscopic Structure=—The epidermal cells of white mustard afford a
good illustration of a mucilage-yielding layer such as is met with,
under many variations, in the seeds of numerous plants. The cuticle
consists of large vaulted cells, exhibiting very regular hexagonal
outlines when cut across.[297] The inner layer of the epidermis is
made up of thin-walled cells, which when moistened swell and give off
the mucilage. In the dry state or seen under oil, the outlines of the
single cells of this layer are not distinguishable. The tissue of
the cotyledons is loaded with drops of fatty oil and with granular
albuminoid matter; starch which is present in the seed while young, is
altogether absent when the latter reaches maturity.
=Chemical Composition=—White mustard deprived of fatty oil yields to
boiling alcohol colourless crystals of _Sinalbin_, an indifferent
substance, readily soluble in cold water, but sparingly in cold
alcohol. From the able investigations of Will (1870) it follows, that
it is to be regarded as composed of three bodies, namely:
Sulphocyanate of Acrinyl C⁸ H₇ N S O
Sulphate of Sinapine C₁₆ H₂₅ N S O₉
Sugar C₆ H₁₂ O₆
-----------------
so that the formula C₃₀ H₄₄ N₂ S₂ O₁₆
[296] _Journ. de Pharm._ xvii. (1831) 279.
[297] An interesting object for the polarizing microscope.
represents according to Will the composition of sinalbin. It is
actually resolved into these three substances when placed at ordinary
temperatures, in contact with water and _Myrosin_, the latter of
which is a constituent of white mustard as well as of brown (p. 66).
The liquid becomes turbid, the first of the above-named substances
separates (together with coagulated albumin) as an oily liquid,
not soluble in water, but dissolving in alcohol or ether. This
_Sulphocyanate of Acrinyl_ is the rubefacient and vesicating principle
of white mustard. It does not pre-exist, as shown by Will, in the
seed, and cannot be obtained by distillation. By treating it with a
salt of silver, Will obtained crystals of cyanide of acrinyl, C₈H₇NO:
by warming it (or sinalbin itself, or an alcoholic extract of the
seed) with caustic potash, sulphocyanide of potassium is produced. The
presence of the latter may be indicated by adding a drop of perchloride
of iron, when a blood-red coloration will be produced.[298]
_Sulphate of Sinapine_ imparts to the emulsion of white mustard, in
which it is formed, an acid reaction. Sinapine is itself an alkaloid,
which has not yet been isolated, as it is very liable to change. Thus
its solution on addition of a trace of alkali immediately assumes a
bright yellow colour indicating decomposition, and a similar colour is
produced in an aqueous extract of the seed.
The above statements show, that the chemical properties of sinalbin
and its derivatives correspond closely with those of sinigrin (p. 66)
and the substances which make their appearance in an emulsion of black
mustard.
The other constituents of white mustard seed are nearly the same as
those of black. The fat oil appears to yield in addition to the acids
mentioned at p. 67, _Benic_ or _Behenic Acid_, C₂₂H₄₄O₂. White mustard
is said to be richer than black in myrosin, so that, as explained in
the previous article, the pungency of the latter may be often increased
by an addition of white mustard. By burning white mustard dried at
100° C., with soda-lime, we obtained from 4·20 to 4·30 per cent. of
nitrogen, answering to about 28 per cent. of protein substances.[299]
The fixed oil of the seed amounts to 22 per cent. The mucilage as
yielded by the epidermis is precipitable by alcohol, neutral lead
acetate, or ferric chloride, and is soluble in water after drying.
_Erucin_ and _Sinapic Acid_, mentioned by Simon (1838)[300] as
peculiar constituents of white mustard, are altogether doubtful, yet
may deserve further investigation. The sinapic acid of Von Babo and
Hirschbrunn[301] (1852) is a product of the decomposition of sinapine.
=Uses=—White Mustard seed reduced to powder and made into a paste
with cold water act as a powerful stimulant when applied to the skin,
notwithstanding that such paste is entirely wanting in essential oil.
But for sinapisms they are actually used only in the form of the _Flour
of Mustard_ which is prepared for the table and which contains also
Brown Mustard seed.
[298] The red compound thus formed with sulphocyanide is readily
soluble in ether, yet in the case of white mustard we find it _not_ to
be so.
[299] Experiments performed by Mr. Weppen in my laboratory, 1869.—F. A.
F.
[300] Gmelin, _Chemistry_, xiv. (1860) 521 and 529.
[301] Ibid. 521.