The Theory and Practice of Brewing

by Michael Combrune

To the several reflections, before made, I thought proper to add the surer help of experience. I therefore made the following trial, with all the care I was capable of. If the effects of it appear satisfactory, by gaining two limited and distant degrees, we may determine and fix the properties of the intermediate spaces, in proportion to their expansion.

In an earthen pan, of about two feet diameter, and three inches deep, I put as much of the palest malt, unequally grown, as filled it on a level to the brim. This I placed over a little charcoal, lighted in a small stove, and kept continually stirring it from bottom to top.

At first it did not feel so damp as it did about half an hour after. In about an hour more, it began to look of a bright orange color on the outside, and appeared more swelled than before. Every one is sensible that a long-continued custom makes us sufficient judges of colors, and this sense in a brewer is sufficiently exercised. Then I masticated some of the grain, and found them to be nearly such as are termed brown malts. On stirring, and making a heap of them, towards the middle, I placed therein, at about half depth, the bulb of my thermometer; it rose to 140 degrees: the malt felt very damp, and had but little smell.

At 165 degrees, I examined it in the same manner as before, and could perceive no damp; the malt was very brown, and on being chewed, some few black specks appeared.

Many corns, nearest the bottom, were now become black, and burnt; I placed my thermometer nearly there, and it rose to 175 degrees: but, as the particles of fire, ascending from the stove, act on the thermometer, in proportion to the distance of the situation it is placed in, through the whole experiment an abatement of five degrees should be allowed, as near as I could estimate.—Putting, a little after, my thermometer in the same position, where about half the corns were black, it shewed 180 degrees. I now judged that the water was nearly evaporated, and observed the heap grew black apace.

Again, in the centre of the heap, raised in the middle of the pan, I found the thermometer at 180 degrees; the corn tasted burnt, the surface appeared, about one half part a full brown, and the rest black. On being masticated, still some white specks appeared, which I observed to proceed from those barley-corns which had not been thoroughly germinated, and whose parts cohering more closely together, the fire, at this degree, had not penetrated. The thermometer was now more various, as it was nearer to, or farther from, the bottom; and, in my opinion, all the true-made malt was charred, for their taste was insipid, they were brittle, and their skins parting from the kernel.

I, nevertheless, continued the experiment, and, at 190 degrees, still found some white specks on chewing the grain; the acrospire always appearing of a deeper black, or brown, than the outward skin; the corn, at this juncture, fried at the bottom of the pan.

I still increased the fire; and the thermometer, placed in the middle, between the bottom of the pan, and the upper edge of the corn, shewed 210 degrees. The malt hissed, fried, and smoked abundantly. Though, during the whole process, the grain had been kept stirring, yet, on examination, the whole was not equally affected by the fire. A great part thereof was reduced to perfect cinders, easily crumbling to dust between the fingers, some of a very black hue, without gloss, some very black, with oil shining on the outside. Upon the whole, two thirds of the corn were perfectly black, and the rest of a deep brown, but more or less so, as the grains were hard, steely, or imperfectly germinated. This was easily discovered by the length of the shoot: most of the grains seemed to have lost their cohesion, and had a taste resembling that of high-roasted coffee.

In the last stage of charring the malt, I placed over it a wine glass inverted, into which arose a pinguious oily matter, and tasted very salt. It may, perhaps, not be unnecessary to say, that the length of time this experiment took up, was four hours, and that the effect it had, both on myself, and on the person who attended me, was such as greatly resembled that of inebriation.

Though, from this experiment, the degree of heat at which malt charrs, is not fixed with the utmost precision, yet we see that black specks appeared, when the thermometer was at 165 degrees; some of the corns were entirely black at 175, others at 180. In proportion as fire causes a deficiency of color, it must occasion a want of fermentable properties, the whole of which are certainly dispersed, when the grain becomes of an absolute black. Thus we may conclude, with an exactness surely sufficient for the purposes of brewing, that true germinated malts are charred in heats, at about 175 degrees: as these correspond to the heat at which pure alcohol, or the finest spirit of the grain itself, boils, it seems to require this heat, wholly to extricate itself from the more tenacious parts of the corn; which, when deprived of this etherial enlivening principle, remains inert, incapable of forming a fermentable must or wort, and indicates to us, that the constituent parts of vegetables may be resolved by heats, equal to those between the first degree which formed them, and the last, which ultimately destroys their properties; though the extracts will possess different qualities or virtues, according to the determinate heat which is applied.