I have already pointed out, in the article BEER, how the starch is
transformed into a saccharine condition, by malting and mashing; and how
a fermentable wort may be obtained from starchy meal. By like operations
may all vegetable substances, which consist chiefly of starch, become
materials for a whiskey distillery. To this class belong all the
farinaceous grains, potatos, and the pods of shell fruits, as beans,
vetches, horse-chesnuts, acorns, &c.
1. _Whiskey from corn._ All those species of corn which are employed in
breweries answer for distilleries; as wheat, rye, barley, and oats; as
well as buckwheat, and maize or Indian corn. The product of spirits
which these different grains afford, depends upon the proportion of
starch they contain, including the small quantity of uncrystallizable
sugar present in them. Hermstaedt, who has made exact experiments upon
the subject, reckons a quart (Prussian or British) spirits, containing
30 per cent. of the absolute alcohol of Richter, for 2 pounds of starch.
Hence 100 pounds of starch should yield 35 pounds of alcohol; or 4·375
gallons imperial, equal to 7·8 gallons of spirits, excise proof.
100 pounds of the following grains afford in spirits of specific gravity
0·9427, containing 45 per cent. of absolute alcohol (= 9/11 of British
proof,) the following quantities:--
Wheat, 40 to 45 pounds of spirits; rye, 36 to 42; barley, 40; oats, 36;
buckwheat, 40; maize, 40. The mean of the whole may be taken at 40
pounds, equal to 4-1/4 gallons imperial, of 0·9427 specific gravity =
3·47 gallons, at excise proof. The chief difference in these several
kinds of corn consists in their different bulks under the same weight; a
matter of considerable importance; for since a bushel of oats weighs
little more than the half of a bushel of wheat, the former becomes for
some purposes less convenient in use than the latter, though it affords
a good spirit.
Barley and rye are the species of grain most commonly employed in the
European distilleries for making whiskey. Barley is mostly taken either
partly or altogether in the malted state; while the other corns are not
malted, but merely mixed with a certain proportion of barley malt to
favour the saccharine fermentation in the mashing. It is deemed
preferable to use a mixture of several sorts of grain, instead of a
single one; for example, wheat with barley and oats; or barley with rye
and wheat; for the husks of the oats diffused through the wheat flour
and rye meal keep it open or porous when mashed, and thus favour the
abstraction of the wort; while the gluten of the wheat tends to convert
the starch of the barley and oats into sugar. When the whole of the
grain, however, is malted, a much more limpid wort is obtained than from
a mixture of malt with raw grain; hence the pure malt is preferable for
the ale and porter brewer, while the mixture affords a larger product,
at the same cost of materials, to the distiller. When barley is the only
grain employed, from one-third to one-sixth of malt is usually mixed
with it; but when wheat and rye are also taken, the addition of from
one-eighth to one-sixteenth of barley malt is sufficient. Oats are
peculiarly proper to be mixed with wheat, to keep the meal open in the
mashing.
The following are the proportions used by some experienced Scotch
distillers.
250 bolls, containing 6 bushels each, being used for a mashing,
consist of,
---
25 bolls of oats, weighing 284 lbs. per boll, or 47-1/3 lbs. per
bushel;
42 malt 240 40
25 rye 320 53-1/3
158 barley 320 53-1/3
--- ------
250 mean 48-1/2
--- ------
From each boll, weighing 291 lbs., 14 imperial gallons of proof whiskey
are obtained on an average; equivalent to 11·2 gallons at 25 over proof.
The malting for the distilleries is to be conducted on the same
principles as for the breweries, but the malt ought to be lightly
kiln-dried, and that preferably at a steam heat, instead of a fire,
which is apt to give an empyreumatic smell to the grain that passes into
the spirits. For such persons, indeed, as relish the smell of burned
turf, called peat-reek in Scotland, the malt should be dried by a turf
fire, whereby the whiskey will acquire that peculiar odour.
But this smell, which was originally prized as a criterion of whiskey
made from pure malt, moderately fermented and distilled with peculiar
care, has of late years lost its value, since the artifice of
impregnating bad raw grain whiskey with peat-smoke has been extensively
practised.
Dr. Kolle, in his treatise on making spirits, describes a malting kiln
with a copper plate heated with steam, 18 feet long, and 12 feet broad,
on which a quantity of malt being spread thin, is changed every 3 or 4
hours, so that in 24 hours he turns out upwards of 28 cwt. of an
excellent and well-kilned article. The malt of the distiller should be
as pale as possible, because with the deepening of the colour an
empyreumatic principle is generated.
When Indian corn is the subject of distillation, it must be malted in
the same way as described in the article BEER. According to Hermstaedt,
its flour may be advantageously mixed with the crushed malt in the mash
tun. But its more complete dissolution may be accomplished by Siemen’s
mode of operating upon potatos, presently to be described.
1. _Mashing._ Barley and raw grain are ground to meal by millstones, but
malt is merely crushed between rollers. If only one-tenth or one-eighth
of malt be used with nine-tenths or seven-eighths of barley, some husks
of oats are added, to render the mash mixture more drainable.
When 40 bushels of barley and 20 of malt form one mashing, from 600 to
700 gallons of water, heated to 150° F., are mixed with these 60 bushels
in the mash tun, and carefully incorporated by much manual labour with
wooden oars, or in great concerns by the mechanical apparatus used in
the breweries. This agitation must be continued for 2 or 3 hours, with
the admission from time to time of about 400 additional gallons of
water, at a temperature of 190°, to counteract the cooling of the
materials. But since the discovery of _diastase_, as the best heat for
saccharifying starch is shewn to be not higher than 160° F., it would be
far better to mash in a tun, partially, at least, steam encased, whereby
we could preserve the temperature at the appropriate degree for
generating the greatest quantity of sugar.
If the wort be examined every half-hour of the mashing period, it will
be found to become progressively sweeter to the taste, thinner in
appearance, but denser in reality.
The wort must be drawn off from the grains whenever it has attained its
maximum density, which seldom exceeds 150 lbs. per barrel; that is, (360
+ 150)/360 = 1·42, or 42 per cent. As the corn of the distiller of raw
grain has not the same porosity as the brewer’s, the wort cannot be
drawn off from the bottom of the tun, but through a series of holes at
the level of the liquor, bored in a pipe stuck in at the corner of the
vessel. About one-third only of the water of infusion can thus be drawn
off from the pasty mass. More water is therefore poured on at the
temperature of 190°, well mixed by agitation for half an hour, then
quietly infused for an hour and a half, and finally drawn off as before.
Fully 400 gallons of water are used upon this occasion, and nearly as
much liquor may be drawn off. Lastly, to extract from the grains every
thing soluble, about 700 gallons of boiling hot water are turned in upon
them, thoroughly incorporated, then left quietly to infuse, and drawn
off as above. This weak wort is commonly reserved for the first liquor
of the next mashing operation upon a fresh quantity of meal and malt.
The English distiller is bound by law to make his mixed worts to be let
down into the fermenting tun of a specific gravity not less than 1·050,
nor more than 1·090; the Scotch and Irish distillers not less than
1·030, nor more than 1·080; which numbers are called, gravity 50, 90,
30, and 80, respectively.
With the proportion of malt, raw grain, and water, above prescribed, the
infusion first drawn off may have a strength = 20 per cent. = spec.
grav. 1·082, or 73 lbs. per barrel; the second of 50 lbs. per barrel, or
14 per cent.; and the two together would have a strength of 61·2 lbs.
per barrel = 17 per cent., or spec. grav. 1·070. From experiments
carefully made upon a considerable scale, it appears that no more than
four-fifths of the soluble saccharo-starchy matter of the worts is
decomposed in the best regulated fermentations of the distiller from raw
grain. For every 2 lbs. so decomposed, 1 lb. of alcohol, spec. grav.
0·825 is generated; and as every gallon of spirits of the spec. grav.
0·909 contains 4·6 lbs. of such alcohol, it will take twice 4·6 or 9·2
lbs. of saccharine matter to produce the said gallon. To these 9·2 lbs.,
truly transmuted in the process, we must add one-fifth, or 1·84 lbs.,
which will raise to 11·04 the amount of solid matter employed in
producing a gallon of the above spirits.
Some distillers mash a fourth time; and always use the feeble wort so
obtained in mashing fresh grain.
2. As the imperfect saccharine infusion obtained from raw grain is much
more acescent than the rich sugary solution got from malt in the
breweries, the distiller must use every precaution to cool his worts as
quietly as possible, and to keep them clear from any acetous taint. The
different schemes of cooling worts are considered under BEER and
REFRIGERATION. As the worts cool, a quantity of starchy matter is
precipitated, but it is all carefully swept along into the fermenting
tun, and undoubtedly contributes to increase the production of alcohol.
During the winter and temperate months, when the distilleries are most
actively at work, the temperature at which the worts are set is usually
about 70° F. When much farinaceous deposit is present, the heat may be
only 65°, because, in this case, a slow fermentation seems to favour the
conversion of that starch into sugar. In some German distilleries a
little chalk is mixed with the worts, to check acidity.