In Bavaria, a country remarkable for the excellence of its beer, the wort is made to ferment at a low temperature, until all the substances which favour acetification have been rendered insoluble, and have separated from
the liquor. The fermentation is conducted in wide, open, shallow vessels, which afford free and unlimited access to atmospheric oxygen; and this in a situation where the temperature does not exceed 45° to 60° Fahr. A separation of the nitrogenous constituents thus takes place simultaneously on the surface, and within the whole body of the liquid. The clearing of the fluid is the sign by which it is known that these matters have separated. The fermentation usually occupies three or four weeks, and is conducted during the cooler portion of the year only, and in a situation removed as much as possible from the influence of atmospherical changes of temperature. The sedimentary yeast (unterhefe), and not the surface yeast (oberhefe), of the Bavarian fermenting backs is employed.
The beers of England and France, as well as most of those of Germany, become gradually sour by contact with the air. This defect, as observed by Liebig, does not belong to the beers of Bavaria, which may be preserved, at pleasure, in half-full casks, as well as in full ones, without suffering any material alteration. This precious quality must be ascribed to the peculiar process employed for fermenting the wort, called by the German chemists ‘untergährung,’ or fermentation from below; and which “has solved one of the finest theoretical problems that had long taxed the ingenuity and patience of both the scientific and practical brewer.” (Liebig.)
The ‘Comptes Rendus,’ lxxvii, 1140-1148, contains a paper by M. Pasteur on the manufacture of an ‘unalterable beer.’ In this communication he states that the liability of beer to turn sour, ropy, &c., is due to the presence of special ferments derived from the air, and from the materials used. By boiling the infusion of malt and hops, cooling out of contact with air, and fermenting with pure yeast[232] in vessels to which only carbonic acid or pure air is admitted, a beer is produced of superior quality, which may be preserved without trouble for any time. Even a partial adoption of these precautions is attended with valuable results. In preparing pure yeast to start with, the author makes use of the fact that oxygen favours the growth of true yeast, but hinders the propagation of the other ferments. Pure yeast being obtained, the beer is afterwards fermented in an atmosphere nearly destitute of oxygen, as its quality is thereby improved. Pure yeast when kept in pure air undergoes no change, even at summer temperature. The mycoderma vini does not, as the author once thought, become changed into beer-yeast on submersion in a nutritive fluid; under these circumstances it acts as an alcoholic ferment, but does not propagate itself.
[232] M. Pasteur does not state how this is to be obtained.
“In the ordinary fermentation of grape-juice and worts these liquids do not furnish a quantity of alcohol equivalent to the sugar which they contain; and this because a certain portion of the sugar serves for the oxidation of the gluten, and is not transformed like the rest. But wherever the liquor has arrived at the second period of transformation, the product in alcohol ought to be equivalent to the quantity of sugar present, as actually happens in all fermentations (sedimentary) which are not accompanied with a formation, but a disappearance of the yeast. According to Dr Ure, worts furnish, in the Bavarian breweries, from 10% to 20% more alcohol than they do by the ordinary process of fermentation (obergährung), or that excited by the use of ‘oberhefe’ or top-yeast.”
East-India Ale or Pale Ale, for exportation, is brewed from worts of a sp. gr. of from 1·063 to 1·070. For the best varieties, 15 to 16 lbs. of the finest East Kent hops are used to every quarter of pure malt. The pale ale or bitter beer of the publicans is commonly a very weak liquor (mere table beer), highly bittered with the hop, and too often with quassia, wormwood, and other still more objectionable substances. The process now adopted by the great brewers of pale ale at Burton-on-Trent combines all the most admirable points of both the Bavarian and Scotch systems of brewing.
Berlin White ale or Pale beer is brewed from wheat-malt mixed with about 1⁄6th part of barley-malt, the ‘wort’ being boiled with hops, 1⁄2 lb. to the bushel, and slightly fermented with ‘top-yeast,’ at a rather higher temperature.
The desire of evading the duty led to the discovery of its being only necessary to employ 1⁄3rd, or less, of the grain, in the form of malt; this portion being sufficient to convert into sugar, in the process of mashing, the starch of the unmalted grain forming the other part. This plan answers well when the wort is merely intended for the production of ‘grain spirit,’ but beer so made is insipid and inferior in quality to that brewed wholly of malt. Inferior kinds of beer have also been made from other ingredients than barley-malt, among which may be named the grain of the cheaper cereals, bran, potatoes, turnips, beet-root, carrots, parsnips, pea-shells, and other vegetable substances rich in starch and sugar, all of which will produce beer by being mashed with water in the common way, with about 9% or 10% of barley-malt.
One quarter of the best barley-malt yields, by skilful mashing, fully 84 lbs. of ‘saccharine,’ or soluble sweet extractive matter. This concentrated within the compass of one barrel (33 galls.) gives a sp. gr. of 1·234. In the process of mashing about 4⁄7ths of this quantity of saccharine (or 48 lbs.) is generally carried off in the first wort; 2⁄7ths (or 24 lbs.) in the second wort; and 1⁄7th (or 12 lbs.) in the third wort; the strengths of the worts being to each other respectively as 4, 2, 1. The average gravity obtained by the common brewers from malt of current quality ranges from 80