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Malting is a process by which germination to a limited extent is artificially induced in barley or other grain with the object of providing an eligible saccharine material for the use of brewers, distillers, &c. During this process a small quantity of a peculiar substance termed diastase is produced, which transforms a portion of the starch* of the grain into gum, and thence into sugar, and has also the property of saccharifying the whole of the remaining starch when the malt is subsequently infused in hot water, as in the mashing operation of the brewer. Wheat, rye, oats, and maize, or Indian corn, are each occasionally made into malt, but barley is found to be the most economical, and the best suited to the purposes of the brewer. Both wheat and rye being destitute of husk, do not afford that protection to the germ or vital portion of the grain, which is found in barley and oats ; hence the germ is easily mutilated, and the grain, in consequence, soon becomes mouldy and undergoes decomposition. Oats, on account of their thick husk, small kernel, and slowness in germinating, are unprofitable, whilst the malt made from maize has not hitherto been used with any great success in the brewing of beer.
Structure of the Cereal Grains.-A seed may be considered as containing a complete plant in the smallest possible space. In barley it consists of an embryo or germ, embedded in starch, the whole being enveloped by three or more skins termed teste, in addition to the husk.
That portion of the seed in which the embryo is embedded, and which is intended by nature for the sustenance of the germ during its incipient growth, or until it is able to extract nourishment from the soil, is by botanists termed albumen, although it is not in any respect analogous to the chemical body of the same name. The nature of this substance varies in different plants, being farinaceous, or composed of starch, in the cereals; fleshy in the almond ; oily in the poppy; and horny in the coffee berry. The embryo-which may be readily perceived in any of the cereal grains by raising the skin from the rootlet end of the back of the seed opposite the furrow-includes the radicle or future root, the plumule or future stem, (called acrospire by maltsters,) and usually one or more cotyledons or seed leaves. On the number of the latter are based the three great classes into which the vegetable kingdom is divided, namely, acotyledonous, to which belong plants having no seed leaves, as ferns, mosses, and sea-weeds ; monocotyledonous, those having one cotyledon, as the cereals and grasses, and dicotyledonous, those having two or more cotyledons, as herbs and trees in general. The division which more immediately concerns us is the monocotyledonous, to which barley belongs.
Germination.-Before the embryo can begin to grow and assimilate its food, which is stored up in the albumen and cotyledons, it must be supplied with a due proportion of moisture, heat, and air. Moisture softens the skin, penetrates the
* Recent observations tend to prove that it is chiefly the cellulose or woody fibre of the grain, which is transformed into sugar, and that most of the starch remains unchanged This point will be adverted to in the text a little further on,
seed, causes the embryo to swell, and produces changes in the albumen and cotyledons, which render them better adapted to supply the young plant with the first materials of its nutrition. Too much moisture, however, is found to be worse than too little, as it prevents germination at the proper time, from the air being excluded while the excess of water is evaporating, and also because it abstracts a portion of the soluble matter designed for the young plant. . From experiments made by Edwards and Colin, and quoted by Lindley, Balfour, Schleiden, and other botanists, it appears that the highest limit of prolonged temperature which barley, wheat, and rye, can bear without injury to their power of germination, is in water 95° F., in sand 113° F., in soil 122° F., in vapour of water 140° F. and in dry air 167° F. ;* a medium temperature of 60° F. seems, to be the most suitable.
Air, or at least oxygen, is one of the chief requisites of healthy germination. Seeds will not grow in an atmosphere containing no free oxygen, such as one composed of hydrogen, carbonic acid, or nitrogen. An excess of oxygen gas is favourable, but if applied too long, the seed becomes rapidly exhausted, and dies. Different opinions exist as to the source from which the seed derives its oxygen during germination, some holding that it is obtained from the air, whilst others think that a portion of the water which the seed absorbs, is decomposed, its oxygen forming carbonic acid with the carbon of the seed, and its hydrogen uniting with some of the principles of the grain, to form acetic acid, oils, and other bodies essential to its growth. It is, however, admitted by all, that during germination, the carbon of the seed combines with oxygen to form carbonic acid, and that in consequence, much heat is generated. Light, though necessary to the plant when it appears above ground, is injurious during the first stages of growth, probably, because it tends to fix the carbon of the seed, and thus prevents the formation of carbonic acid.
With a due supply of moisture, air, and warmth, the embryo or germ, after a greater or less time, according to the quality or nature of the grain, begins to grow, the radicle shooting downwards, and at the same time sending into the cotyledons and albumen minute vessels in search of nourishment; whilst the plumule, shooting upwards, appears above ground in a few days as a green blade. At this stage, the albumen is generally exhausted, but the germ, now become a plant, is able to derive nutriment through its roots, and with the aid of its blade, to decompose the carbonic acid which it absorbs from the atmosphere, and fix the arbon in its tissues for the increase of the plant.
In the cereals and grasses, the cotyledon remains within the seed, and never shifts its position, but in seeds with two cotyledons, the latter generally rise to the surface, one on each side of the plumule, and when the plant is able to provide for itself, wither away. During germination, some of the gluten which all seeds contain, is changed into the body before-mentioned, termed diastase; this substance then converts a portion of the starch, which is insoluble in water, into dextrin and sugar, which are soluble, and they in their turn, being thus prepared for assimilation by the plant, contribute to the growth of the embryo.
* From experiments made in the Inland Revenue Laboratory, it was found that the vitality of good Chevalier barley was not destroyed until the temperature 130° F. had been attained in water, and 150° in air. It is very probable, however, that the intensity of vital power in the grain varies greatly in the numerous descriptions of barley, and in different seasons.
The chief constituents of the cereal grains are, starch, sugar, gum, and gluten. According to Hermstadt, 100 parts of barley consist of
Starch . . . . . . . . 60.50
100.00 Barley belongs to the botanical family Graminacex, and the varieties used in malting are, the two rowed barley (hordeum distichon,) and bere or bigg (hordeum hexastichon,) which is six rowed.
In the manufacture of malt, four operations are necessary, namely, steeping, couching, flooring, and kiln drying.
Steeping. The barley properly screened and cleansed is placed in a vessel called a cistern, and is kept covered with water, during a period of not less than 40 hours. While in steep the grain softens and increases, by the absorption of water, over a fifth in bulk* and nearly fifty per cent. in weight, and some of the carbon of the grain combines with oxygen to form carbonic acid, which dissolves in the steep. water along with a portion of colouring matter from the husk. Sometimes, especially in warm weather, a slight fermentation arises from the organic matter in the steep water acting on the decayed grains, and hence it is accasionally necessary to replace the water during the period of steeping. The barley remains covered with water for a period varying from 40 to 80 hours, according to the season, temperature, and description of grain. If a corn taken from any part of the heap and held lengthwise between the first finger and thumb readily breaks down into a pulpy state when squeezed, the steeping is judged to be complete. The water is then drained off, and the grain thrown into the couch-frame where it is kept in a mass of considerable depth, for at least, 20 hours, in order that heat may be developed and germination induced.
Couching and Flooring.–Very little apparent change takes place in the grain for from 30 to 48 hours, after removal from the cistern. The temperature of the grain then begins to rise, oxygen is absorbed, and carbonic acid gas evolved, and the radicle, or as the maltster terms it, the “chick” or “cbit,” may now be seen emerging from the base of each corn. In about two days afterwards the grain becomes moist on the surface, or “sweats," and emits an agreeable odour, compared by sonce persons to that of apples; the fibrils of the radicle burst through the root-sheath, and at about the same time, the plumule passing the boundary of the cotyledon, is seen making its way in an opposite direction to that of the radicle. To lower the temperature and thereby moderate the germination, the grain is now spread rather thinly on the floor and frequently turned. By this means the floor is kept at an average temperature of about 60° F., germination proceeds slowly and regularly, and the starchy matter of the grain becomes white . The legal assumption is, that barley steeped for 40 hours, swells on the average 22-7 per cent
sott, and friable, and sweet tasted so far as the plumule or acrospire has advanced. In ten or twelve days after the grain has been emptied from the cistern, the frequent turnings and exposure to the air, together with the growth of the rootlets and acroepire, have dissipated the greater portion of the moisture absorbed in the steeping, and the rootlets wither. It is then laid a little thicker on the floor to generate heat, liberate more moisture, and render it mellow, and by this time the acrospire ought to have grown to two-thirds or three-fourths the length of the corn. The grain, now properly malted, is dried on a kilu to arrest germination, which, if suffered to proceed beyond this point, would exhaust the seeds of their soluble contents, and also to enable the malt to be kept in store without further change.
Many maltsters work their floors on a plan somewhat different from the preceding. The floors are kept thick, and germination is forced, abundance of rootlets being formed. The heat generated in this process dissipates a part of the moisture absorbed by the grain while in steep, long before the plumule has grown to a sufficient length. Hence, it is requisite to sprinkle the corn with water, in order to stimulate germination. In a few of the malting districts, however, sprinkling is not resorted to as a practice, it being thought unnecessary and injurious. But when a maltster works for « out-come” or “out-cast," as it is termed, that is, with a view chiefly to a large increase of produce over the quantity of barley steeped, rather than with the desire to obtain malt of fine quality that will tend to the profit of the brewer, it certainly proves of advantage to water the corn on the floor, as that treatment has the effect of increasing the bulk of the finished malt. In other words, sprinkled grain, “ measures well” off the kiln.*
Kiln-drying. The process of kiln-drying varies according to the purpose for which the malt is required. There are three varieties of kiln-dried malt, namely pale, amber, and brown, the difference between these depending solely on the degree of heat to which each has been subjected, and the manner in which the heat has been applied. Pale malt is usually made from the best barley, and occupies from two to three days in the drying, the temperature being slowly raised from about 90° F. to 120° F., and the grain frequently turned. Amber malt is treated in a similar manner, until it is almost dry, when, to give it a slight scorching, the temperature is raised to 160° F. For brown or porter malt, the grain is placed to the depth of about half an inch on the floor of the kiln, which in this case usually consists of perforated iron plates or wire net-work, while a strong, blazing fire, produced by the ignition of fagots of wood, is applied below. During this process, the temperature rapidly rises to 180° F., or higher ; a portion of the starch and sugar of the malt becomes carbonised, while, as some allege, the pyroligneous acid, and other products evolved from the burning wood, impart to the malt that peculiar flavour so much esteemed by the porter drinker.
In the process of malting, barley loses from 8 to 12 per cent. in weight, and increases from 3 to 10 per cent. in bulk.
The grains of malt are generally free from wrinkles, although, sometimes, they have a slightly shrivelled appearance. The husk has a lighter colour than that of barley, and remains open at the end from which the rootlets have protruded.
It is commonly supposed that the starch of a grain of barley is changed during the operation of malting, into sugar, just so far as the acrospire or plumule has
There is also an important reason for the practice of sprinkling, which arises from the system of levying the duty on malt. This will be explained in another part of the work, when ti eating of traders' operations in relation to the Exciso laws.
extended; but this opinion hardly seems correct, since microscopical observation shows, that the flour--whether taken from the immediate neighbourhood of the embryo, or from the unmalted part of the seed, beyond the acrospire-differs in no respect from ordinary barley stareb, except in the somewhat greater size of the granules, which latter circumstance, is, no doubt, the result of the high temperature to which the grain has been subjected. In all plants, starch-granules, wherever found, are invariably enclosed in cells composed of a vegetable tissue termed cellulose, which in chemical composition is identical with starch. In malt, so far as the acrospire has grown, this tissue is found to have almost wholly disappeared, and it is not unreasonable to conclude that it is chiefly to the transformation of the cellulose into sugar, that the sweetness and friability of malt are due.
A bushel of good barley weighs from 49 to 56 lbs ; a bushel of fairly-made malt weighs from 38 to 43 lbs.
No complete or satisfactory analysis of malt has as yet been published, but from the preceding account of the process of malting, it may be inferred that the principal differences between ungerminated and germinated corn, consist in the greater proportion of sugar and gum, and the smaller proportion of gluten in the latter substance.
Roasted malt, patent malt, or black malt, as it is variously called, is used by brewers for the purpose of giving to porter its rich, deep brown colour and peculiar flavour, and in some districts, as in Lancashire, for the purpose also of deepening the colour of ale and beer worts. The preparation of this sub. stance is carried on by persons specially licensed, and is a trade quite distinct from that of malting. Ordinary malt, as has already been stated, (page 268,) may be rendered suitable for porter brewing by raising the heat of the kilns at the end of the drying process, or by subjecting the malt to the action of & wood-fire, but as a great portion of the fermentable matter is destroyed by this method, recourse is generally had to the use of roasted malt, a small quantity of which imparts to the worts of pale malt all the colour and flavour that can be desired.
The process of roasting malt is very similar to that of roasting coffee. The malt is placed in a metal cylinder, which is made to revolve over a charcoal or coke fire ; by this means the malt is slowly roasted at a temperature varying from 360° to 4009 F., until it assumes a dark chocolate colour. Caramel, or burnt sugar, a blackish brown substance, exceedingly soluble in water, and of a bitter, empyreumatic flavour is thus produced, while at the same time part of the grain is unavoidably carbonised, or reduced to charcoal.*
Caramel, although formed from sugar, will not ferment or afford alcohol, and in this respect is of no use to the brewer. Its principal value consists in its colouring 'power, whilst at the same time it adds considerable density to the worts. Brewers occasionally avail themselves of the law, permitting them to prepare
* If the heat exceed 420°, the malt becomes almost wholly decomposed, leaving nothing but a mass of porous charcoal. Caramel, when pure, is nearly tasteless. The substance met with in commerce under that name, is prepared from cane-sugar, and generally exists as a thick, syrupy, dark brown liquid, of bitter taste, and intense colouring power. It is largely used by rectifiers to impart a browu tint to compounded spirits.