. Colour of burnt coffee.
We have given this table, not on account of any information which it contains, but to put our readers on their guard against the false conclusions of this writer. We have taken malt dried at the temperature of 175°, put it into a garden-pot filled with soil, and have seen it vegetate apparently as well as raw grain placed in the same situation. Now, this is only one degree lower than that in which Mr Combrune says malt is converted into charcoal, and it is four degrees higher than that in which his malt assumed the colour of burnt coffee. Certainly malt reduced to the colour of burnt coffee by heat would be deprived of the power of vegetating. Mr Combrune's .ex-periments were made by putting malt into an earthen pan, which he placed over a charcoal fire in a stove, while he kept stirring the malt the whole time of the experiment. The bulb of the thermometer was placed half-way between the upper surface of the malt and the bottom of the vessel. Now the reader will perceive at once that the earthen pan would be mhich hotter than that part of the malt where the thermometer was placed. By the constant stirring of the malt, the whole of it was gradually exposed to the burning action of the surface of the pan. Had the experiment been made without stirring the malt at all, and had the thermometer been placed near the surface, in that .case the changes in the colour of the malt at the surface would have indicated the tempe-ture to which it was exposed. But in the way that Mr Combrune conducted his experiments, the temperatures which he obtained were entirely fallacious. We have not the least doubt that the temperature of the earthen pan, towards the end of his experiment, was above 400°.
Mr Combrune's law, however, that the heat of the water in mashing ought to be regulated by the colour of the malt; namely, that the paler the malt is, the lower ought the temperature of the mashing water to be, is founded on accurate observations. The fact is, that boiling water would answer better than any other for mashing, because it would dissolve most speedily the soluble part of the malt. The only reason for not Using it is, that the tendency of the malt to set increases with the temperature of the water. Now the higher the colour of the malt, the less is its tendency to set; but we may nevertheless use water of a Tiigher temperature to mash with it. For the same reason, when raw grain is used, the temperature of the mashing water must be still lower than when malt is employed; because raw grain has a very great tendency to set.
The old malt-kilns had a bottom of haircloth in- ' stead of the iron plates full of holes, which constitute a more recent improvement. We have seen the thermometer in such a kiln, when the bulb touched the haircloth, rise as high as 186°. In general, the temperature of the malt-kiln is very carelessly regulated. We have seen malt for the very same purpose dried at a temperature which never rose higher than 136°; while a portion of the very same malt, put into another kiln, was heated as high as 186°. But such a careless mode of drying malt is reprehensible, and must be more or less injurious to the brewer. In general, the more rapidly malt is dried, the more does its bulk increase. This method, ac cordingly, is practised by those who malt for sale, as is the case with most of the English maltsters ; because malt is always sold by measure and not by weight. The brewers would find it more for their interest to buy malt by weight than by measure. In that case the maltsters would dry their malt at as low a temperature as possible. But this would signify very little, or rather would be advantageous to the brewer; because dried malt soon recovers part of the moisture lost on the kiln, when kept for some time in sacks. And when malt is dried at a low temperature, we are sure that none of it is injured by the fire-It will, therefore, go farther in the production of beer. The time of kiln-drying varies considerably, according to the quantity of malt exposed to the action of the heat; but when that quantity is not too great, we may estimate the time of kiln-drying, in general, at two days. After the fire is withdrawn, the malt is allowed to remain on the kiln till it has become nearly cold.
Pale malt is best made by applying a low heat, at first, and increasing it at regular intervals. If done judiciously, the heat may be carried up to 170° without injuring the colour. But such a heat is not; necessary, as the malt becomes dry enough and fit for keeping at 140°.
Brown or porter malt is dried by applying the same heat at first as to pale malt, and after it is half dried, by blowing it (as it is termed) on the kiln. This is done by raising the heat as high as the men who turn it on the kiln can possibly stand. This may be stated at 200° for the first turning, and higher afterwards.
By the kiln-drying, the roots of the barley, or, as the maltsters call them, the comings, are dried up and fall off. They are separated from the malt by passing it oyer the surface of a kind of wire screen, which allows the comings, to drop through, while the wires are too near each other to permit the grains of malt to pass.
If 100 lbs. of barley malted in this manner, with all the requisite care, be weighed just after being kiln-dried and cleaned, they will be found, on an average, to weigh 80 lbs. But if the raw grain be kiln-dried at the same temperature as the malt, it will lose 12 per cent, of its weight. Hence 12 per cent, of the loss which barley sustains in malting must be ascribed to moisture dissipated by the kiln-dry-ing; so that the real loss of weight which barley sustains when malted amounts to eight per cent. This loss, from a great many trials made in the large way, with all the requisite care, we conceive may be accounted for in the following manner:—
Dissipated while on the floor, . . 3*0
Roots separated by cleaning, . . 3*0
These numbers were obtained from above thirty different maltings, conducted in four different malt-ing-houses, with as much attention to every circumstance as was compatible with practical malting. The matter carried off by the steep-water, which amounts to about ^yth of the Weight of the whole grain, we conceive to be dissolved from the skin or husks. It may, therefore, be left out of view. The waste is owing to grains of malt crushed by the workmen while turning the malt on the floor^ and afterwards dissipated or destroyed during the subsequent processes. We were not able to collect these bruised grains and weigh them; the number therefore given for them in the preceding table is hypothetical; but, from a great many circumstances, which it would be too tedious to mention here, we believe that, in our trials, part of the whole very nearly represents the amount of the crushed grains. Thus the real loss of weight by malting (supposing nothing lost by steeping, and no grains crushed) is only six per cent., and of this loss four per cent, may be safely ascribed to the roots ; so that not above two per cent, at most can be assigned to the carbon dissipated by the evolution of carbonic acid on the floor and on the kiln. Indeed we have reason to conclude, from a good many trials, that the greatest part of this loss of two per cent, is sustained on the kiln. For, if malt dried carefully at a low temperature be afterwards kiln-dried, or exposed, as was our method, to the heat of a steam-bath, it never afterwards recovers its former weight by ex posure to the air. And every time this experiment is repeated, by artificially moistening and drying the same malt, a new loss of weight is sustained. The same observation was made by Saussure, who conceived that the loss was to be ascribed to the formation and dissipation of water in the barley-corn. But we have no proof whatever that any sutsh formation takes place. It is more probable that the loss is owing to the formation and escape of carbonic acid gas.
Big sustains a considerably greater loss of weight when malted than barley. The average loss of weight in our trials with barley was only eight per cent., while that of big was fifteen per cent., or nearly double. This, we conceive, is owing to the destruction of a much greater number of. the corns duriog the process of malting big than barley. But in all our experiments on big, that grain was manifestly oversteeped. To this, perhaps, a good deal of the difference may be ascribed. Our maltsters had not been in the habit of malting big, and therefore were not likely to do it so much justice as they did to the barley. Hence it would be improper to venture upon any general conclusions from the experiments which we made upon the malting of big.
The bulk of the malt is usually greater than that of the barley from which it was obtained; but this varies a good deal according to the goodness of the grain and the mode of drying the malt. In our trials, made all in the same way, 100 bushels of the different kinds of grain gave, on an average, the'following results :—
English barley, 109
Scotch barley 103
Scotch big, 100*6
The greatest quantity in bushels obtained from 100 bushels of English barley was 111}, the least 106 bushels. The greatest quantity obtained from 100 bushels of Scotch barley was 109, and the least 98 bushels. The greatest quantity obtained from 100 bushels of big was 103 bushels, the least 97 bushels. Hence it appears, that, on malting English barley, there is a profit of nine per cent., while big yields scarcely any thing more than its bulk before malting. The English maltster makes more bushels of malt than he pays duty for; but the maltster of big, on the contrary, obtains fewer.
We shall subjoin here two tables, which exhibit in one view the result of a considerable number of trials made by the author of this treatise, on malting different varieties of grain. The barley is distinguished by the name of the county where it grew. To understand the first table the reader must know that excisemen estimate the quantity of malt by subtracting one-fifth from the best or highest gauge in the steep or couch, and charge the duty accordingly.
Was this article helpful?