Mustard

Mustard (Sinapis), a genus of plants of the natural order Cruciferae, now generally included as a sub-genus of Brassica. Three species, all annuals, of Sinapis contribute their seeds to the manufacture of mustard. (1) Black Mustard (S. nigra), a native of the middle and the south of Europe, also of Britain, but rare in Scotland; a rather coarse plant, two or more feet high, having the lower leaves lyrate and usually hispid, the upper leaves linear-lanceolate, entire, and hairless. The flowers are yellow, in slender racemes. The pods rarely exceed half an inch in length, closely pressed to the stem. The seeds are deep brown. (2) White Mustard (S. alba), a native of southern Europe and western Asia, naturalised in the southern parts of Britain and in Ireland, and in the United States. The whole plant is more or less hairy, the leaves pinnately lobed. The flowers are large compared with those of the preceding species; the pods nearly twice as long, with a long flattened beak, and five prominent nerves; and the seeds are pale yellow. (3) The Wild Mustard (S. arvensis), in nearly all parts of the country better known as Charlock, is a weed of cultivation only too common throughout Britain and Ireland in cornfields, and in some parts of the United States. It is from the ground seeds of the two first named that mustard is chiefly obtained, but those of the last named are also used in the manufacture of that condiment. The wild mustard is reputed to have yielded the original Durham Mustard, but its seeds are now only gathered for mixing with those of the two preceding species. The black mustard is the most pungent, and is almost exclusively used in the manufacture of mustard on the Continent. White mustard is most favoured in Britain, chiefly because the skin is more easily separated from the seed. The greatest bulk of it is grown in the fens of Lincolnshire and Cambridgeshire, also in Kent and Essex. White mustard is sown in gardens, and used as a small salad. Much of the mustard seed imported from India is Sarepta Mustard (S. juncea). Mustard is often adulterated (see ADULTERATION); but 'mustard condiment,' made of mustard flour and wheaten flour or starch flour, is less bitter and stinging than pure mustard, and keeps better. Both black and white mustard seed yield by expression a non-drying fixed oil, which is known as oil of mustard, and is free from pungency. When the residual cake, possessing in itself little pungent odour, is treated with water it immediately becomes powerfully irritating to the skin. This is due to a chemical action between an albuminous body, myrosin, and complex bodies differing in the two varieties of seed which are present in the cells. These in presence of water react, giving, in the case of black mustard, a volatile oil, having the composition of isosulphocyanate of allyl, $C\_3H\_5SCN$, while in the white seed the non-volatile sulphocyanate of acryl, $C\_2H\_5SCNO$, is produced. This action is similar to that of oil of bitter almonds (see ALMONDS). It is to the formation of these vesicating substances that the pungency and activity of a mustard plaster are due. As the white seed contains more myrosin than the black, it is usual to mix the two, so as to fully develop the action of the latter. The use of boiling water is of course inadmissible in forming such a poultice, as it rapidly dissipates the volatile oil, on which the virtues partly depend (see BLISTER). 'Mustard papers,' used as vesicants, are made of mustard flour deprived of its fixed oil. The cake that remains after the oil is extracted may be given to cattle as a condiment. The Mustard-tree of Scripture has been supposed to be Salvadora persica, a small tree of the natural order Salvadoraceæ, a small order allied to Myrsinaceæ; but other interpreters insist that the ordinary black mustard is meant in the proverb.