Brewing consists of five successive processes, which are distinguished by the following names: 1. Mashing ; 2. Boiling 3. Cooling; 4. Fermenting; 5. Cleansing. We shall afterwards give a description and view of the utensils employed in a large London porter brewery, where they have been carried to the greatest perfection. But we conceive it better to give a description of the processes themselves, in the first place, without referring them to any specific form of vessels ; observing only, that the size of all the utensils must be proportional to the quantity of beer which it is proposed to make at once.
1. The specific gravity of malt varies a good deal, according to the way in which it is dried upon the kiln; but its mean specific gravity may be stated at 1-201. In general the specific gravity of big-malt is rather inferior to that of malt from barley. Let us suppose, for the sake of stating the comparative quantities, that it is our object to employ in a single brewing fifty bushels of malt. The first thing to be done is to grind the malt in a mill, and the best kind of mill for the purpose is that iu which the malt is made to pass between two iron rollers.
We must be provided, with a copper boiler capable of containing at least the fifty bushels of malt; or its solid contents must, at the smallest, amount to 382 ale gallons, which are rather more than 107,521 cubic inches, or 62£ cubic feet. This copper boiler must be placed over brick-work upon a furnace, and there must be conveniences for filling it with water, and for letting the water off when sufficiently heated, into the mash-tun.
The mash-tun is a wooden vessel composed of stave? properly fixed by means of iron hoops, and usually placed in the middle of the brew-house. It has a false bottom full of holes at some little height above the true bottom. Its capacity varies according to the extent of the brewery establishment; but a mash-tun capable of mashing fifty bushels of malt must be at least one-third larger than the bulk of the malt, or it must be capable, at least, of containing seventy-five bushels.
A quantity of water, equal at least in bulk to that of the malt, is to be put into the boiler, and heated up to 190° or 180°, according to the fancy of the brewer and the quality of the malt; but the best brewers, in general, employ the lowest temperature.
The boiler should contain a quantity of water, about two-thirds more than the quantity of finished ale required. That is to say, to brew twenty barrels of ale, the open boiler should hold thirty-five barrels of wort.
When an upper back is used, or when a condensing pan is placed on the top, less room is required for ^he wort; but it is always better for the brewer to have the boiler above the standard than under it.
There are two methods of mashing; first, by letting the water rise up through the malt from the false bottom of the mash-tun. The first mash at 170° heat, the second at 190°. The second method is by first filling into the mash-tun the whole quantity of water for the first mash at 180p of heat, and running the malt into it from the hopper above, stirring, at the same time, either with oars or by the ftiacliine. The second mash at 190°.
The temperature of the water in the first mash is lowered in both methods about 40°; but the mash afterwards rises 20° from the chemical action of the malt upon the water.
The quantity of water for the mash must be regulated by the required strength of the wort.
Edinburgh brewers fix the prices of their ales at from £3, £4, £5, £6, £7, and £8, per hogshead, according to the price of barley, &c.
The flowing of the wort takes time according to the quantity in operation. In large mash-tuns the stop-cock is made large in proportion to the size of the mash-tun, making allowance for the velocity with which the worts escape by the pressure. In a brewing of thirty barrels, the wort will flow in half an hour. But when sparging is taken into account, it may take six hours to finish the mashing and flowing of the wort.
After the water is mixed with the malt, the mixture is completely stirred and all the clots broken, either by workmen, who use for the purpose very narrow wooden shovels, or, when the capacity of the mash-tun is very great, as in the London breweries, by a machine which is driven by a steam-engine. Great care must be taken to break all the clots, because the whole of the malt within them would otherwise escape the action of the water, and be lost to the brewer. When the water and malt are sufficiently mixed, the mash-tun is covered and left in this state about three hours. But the time varies according to circumstances.
Though the specific gravity of a malt-corn be greater than that of water, yet if it be thrown into that liquid it always swims. The reason is, that between the skin and the kernel there is lodged a quantity of air, which it is not easy to drive away. Accordingly, brewers are in the habit of judging of the goodness of malt by throwing a certain quantity of it into the water, and, reckoning the grains which fall to the bottom, these indicate the proportion of unmalted grain which the malt contains. Of course, the more of them that exist in any given quantity of malt, the worse must the malt be considered. But though malt, when we consider only single corns, is about a sixth heavier than water, yet a bushel of malt does not weigh so much as one-third of a bushel of water. For, on one occasion, the hot water in the mash-tun, before the addition of the malt, stood at the height of twenty-two inches. On adding the malt, it rose to the height of twenty-nine inches. The bulk of the water was fifty-one bushels ; that of the malt before grinding, forty-seyen and a half bushels. We see from this that the real space occupied in the mash-tun by the forty-seyen and a half bushels of malt was only seven inches, while the fifty-one bushels of water occupied the space of twenty-two inches; therefore about two-thirds of the bulk of the unground malt consisted of interstices filled with air.
The temperature of the water is considerably lowered when it is mixed with the malt, but we have been unable to determine how much, from the impossibility of thrusting a thermometer down to the centre of the mash-tun, the only place that would give a correct result. But we may state a few out of the many observations which we have made on the subject ; fifty-one bushels of water of the temperature of 192° were mixed with forty-seven and a fourth bushels of malt; after mixture, the temperature at the surface of the mash was 140°. Two hours and a half after, when the wort began to run off, its temperature was 156°, and at that time the surface of the mash was at the temperature of 136°. If we suppose in this case that the whole mash lost four degrees as well as the surface, and take the mean between the bottom and top, we shall have the mean
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