PART VIII.--CONDIMENTS: MUSTARD,

PEPPER, &c.

MUSTARD.

§ 293. Mustard is made from the seeds, finely ground, of the Sinapis nigra, or black mustard, or from those of the Sinapis alba, or white mustard, or again, from a mixture of both varieties. The manufacturer reduces the seeds to powder, and passes the product through a series of sieves. The portion in the first sieve is called the dressings, that which passes through is an impure mustard flour. The impure flour, on being passed through a second sieve, yields the pure flour of mustard and a second quantity of dressings. The

dressings are utilised, by being submitted to pressure, for the sake of the fixed oil they contain.

Microscopical Structure of the Seed.The white mustard seed is made up of the husk and the seed proper. The seed p proper is simple in structure, consisting entirely of minute oil-bearing cells; their size averages 00041 inch in the finely powdered seed; and they look extremely like starch corpuscles, but neither polarise light nor strike a blue colour with iodine.

The complicated structure of the husk of the mustard seed, in part unravelled by Hassall, has more recently been fully investigated by the labours of Semplowskis and v. Höhnels.* It is built up of no less than six layers (see fig. 67).

(1.) The most superficial is composed of almost quadratic thin-walled cells (051 micro-millimetre in diameter) covered with a thin cuticle. The lumen

Fig. 67.-Section through the coats of the seed of Sinapis alba.sk, The outer skin, filled with swollen mucus; p, the polygonal cells in section, their form better seen in fig. 68; w, the layer of wine-glass shaped cells; t,a thin-walled parenchyma; g, a layer of gluten-like cells; i, the inner seed coating. Potash preparation x 160 (after MOELLER).

* Moeller's "Mikroskopie," p. 261.

is narrow, and the cells are almost entirely filled with a gelatinous substance. On the addition of water the cells swell up to several times their original volume, and the gelatinous substance escapes from some of the ruptured cells. If looked at from the surface these cells are hexagonal (see fig. 68), and the

Fig. 68.-A superficial view of elements delineated in section in fig. 67; the same lettering has been followed-e, embryonal tissue. Potash preparation × 160 (after MOELLER).

central lumen or cavity is seen surrounded by ring-like layers of the mucilage.

(2.) The second layer is formed out of large, roundish, polygonal cells with thickened walls; their form is not so well seen on section as on the surface. The cells present differences in different species of mustard, the white mustard has cells with two distinct layers, and with intercellular spaces; the black mustard has larger cells, with only a single homogeneous cell-wall, while the Russian mustard has likewise cells singlewalled, but irregularly polyhedral in outline.

(3.) The third layer can only be seen properly in section; it consists of cells which have been likened to wine-glasses, though their outline rather suggests to the author the soles of narrowheeled shoes (see fig. 67). A striking peculiarity of these cells is that they vary in length or height; the surface of the seed is mapped out into small pits; in the middle of each of these small pits the cells are lowest, at the borders highest. The cells are colourless in Sinapis alba, but red-brown in Sinapis nigra.

(4.) The fourth layer is a thin-walled parenchyma filled with pigment in black and Russian mustard, but colourless in white mustard.

(5.) The fifth layer belongs morphologically rather to the substance of the seed than the husk. It is a thick-walled, single layer of polyhedral cells, containing a granulated sub stance.

(6.) The sixth layer is composed of an irregular parenchyma of transparent, colourless cells (see fig. 68), well seen from the surface, but indistinct on section (see fig. 67).

As a rule none of the husk is found in commercial ground mustard, the main bulk being made up of the substance of the seed.

§ 294. The accompanying tables (XLVI., XLVII.) give some careful analyses by C. H. Piesse and Lionel Stansell* of black and white mustard::

TABLE XLVII.-ANALYSES OF ASH OF MUSTARD SEED.

§ 295. The Chemistry of Mustard is extremely interesting; both seeds, white and black, contain a fixed oil (from about 36 per cent.), and a sulphocyanate of sinapin and myrosin. Black mustard seeds contain, in addition to the foregoing, myronate of potash (about 5 to 6 per cent.) When the powdered black mustard seeds (or the mixed black and white) are moistened with water, the myronate of potash acts upon the myrosin, and produces the volatile oil of mustard. White mustard seeds, on the other hand, contain also a sulphur principle, sinalbin, not found in black.

Sinapin, C16H2NO-Sinapin exists as a sulphocyanate, both
Analyst, 1880, p. 161.

in black and white mustard seeds, as well as in the seeds of Turritis glabra, L. It was first prepared by Henry and Garot in 1825. The best process for extraction of the sulphocyanate on a small scale is (according to Von Babo) to exhaust the oil from the seeds by ether, then to treat with cold absolute alcohol, which only takes up a little of the sulphur compound, and lastly, to dissolve the sulphocyanate of sinapin out with alcohol of 90 per cent. The excess of alcohol is then separated by distillation, and the substance crystallises out, yielding about 1.1 per cent.

Sinapin itself cannot be obtained pure, but a watery solution may readily be prepared by decomposing a solution of the bisulphate with a proper quantity of baryta. After filtering away the sulphate of baryta, the filtrate is of a yellow colour and intensely alkaline reaction; it precipitates many metals from their solution, but on evaporation its colour changes through green and red into brown, and at last it leaves behind an uncrystallisable brown residue. On boiling a solution of sinapin with the alkalies or alkaline earths, the sinapin splits up into sinkalin and sinapic acid,

C16H23 NO5 + H2O

=

CHINO + C11H12059

and similar treatment of the sulphocyanate of sinapin produces the same decomposition. To sulphocyanate of sinapin is ascribed the formula CH23NO,CNHS. It forms colourless, transparent, truncated prisms, in warty or starlike groups, without odour, but of a bitter taste, of neutral reaction, melting at 130° to a yellow fluid, solidifying again in an amorphous mass. The sulphocyanate is readily soluble in water; but ether, turpentine, and bisulphide of carbon do not dissolve it. If to a hot solution in alcohol concentrated sulphuric acid be added, bisulphate of sinapin, C6H2NO5, SH2O4 + 20H2, separates on cooling in rectangular plates. From this salt the neutral sulphate may be obtained by solution in water, and precipitating half the sulphuric acid by baryta.

23

44

Sinalbin, CH4N2S2O16, a substance which exists only in white mustard, and may be supposed to take the place of myronate of potash. It splits up into sugar, bisulphate of sinapin, and sulphocyanide of acrinyl, CH,NSO. The last, on treatment with alkalies, yields ammonia and the salt of an acid melting at 136°, to which the formula C.HO, is ascribed.

8 3

Myrosin, a substance analogous to emulsin, has not yet been obtained albumen- or lime-free; its solution froths on being shaken; it is coagulated by warming to 60°, as well as by acids and alcohol.