The yeast troughs belonging to the union casks are in almost all instances fitted with attem perating pipes. The attemperating pipes of yeast troughs are sometimes so fitted, that by means of cords passing over pulleys fixed to the ceiling, they can be lifted up clear of the troughs, when the latter have to be cleaned. The union casks also are fitted with attenaperatora. A good arrangement consists of a hollow brass plug screwed bate a suitable mounting on the top of the cask, this plug having two nozzles, which respectively communicate each with one of the tinned copper pipes extending from the plug into the cask. These pipes are connected at their inner ends, and a current of water can be made to enter at one nozzle, flow through the corresponding pipe, and return by the other pipe to be discharged by the second nozzle. The nozzles are reapectively connected by flexible tubing to cold water and return pipes led along the sides of the yeast trough. These attemperators can be readily removed, and the holes through which they were inserted being closed by plugs, the cask can be rotated for cleansing in the usual way.
To reduce the labour incidental to the disconnection of the casks for clea.ning, the plan of filling and feeding each oask through one of its axles has been introduced. At one end of eaoh cask, the axle or trunnions, cast in one piece with tho east-iron cross fixed to the head, is hollow, and is fitted with a brass bush secured by a nut. At the inner end, the brush or tube is made conical, so that it fits tightly into the hole in the head of the cask, whilst, at the other end, it has a spherical bearing formed on it, which fits into a corresponding seat at the end of the branch pipe from which the cask is filled. The spherical bearing and its scat are hold in close contact by bolts, the nuts of which exert their pressure through spiral springs. By this means a joint is obtained, that, although perfectly tight, does not interfere with the rotation of the cask. The main pipe running along each range of union casks, communicating both with the feed reservoir and with the fermenting tuns, is furnished with cocks, by which the supply from either source eau be regulated. Each branch pipe is also furnished with a cock for regulating the supply to the particular oask to which it belongs, and each branch is also formed for a portion of its length of flexible tubing to enable the lower end to be readily disconnected. For turning the easks, spur wheels and crank handles are provided.
The " Untergahrung," or system of bottom fermentation followed by tho Bavarian brewers, differs materially from any adopted in this country. The object of the Bavarian process is to completely
clear the wort of gluten, and, by removing the oxidizable matters, render the beer incapable of being soured by even a prolonged exposure to the atmosphere. To effect thc separation of the gluten, the Bavarian brewers, instead of adding ordinary yeast to the wort, mix it with the peculiar kind of deposited yeast termed " untcrhefe." The fermentation is effected in comparatively shallow backs or squares, placed in cool cellars, where the atmospheric temperature is not allowed to exceed 8° to 10° (48° to 50° F.). The process requires three or four weeks, the earbonic acid gas being disengaged in very minute bubbles, that carry up a mere film of froth. The insoluble gluten or yeast is depoeited at the bottom of the fermenting vessels as te viscid sediment, the unterhefe. This deposited yeast is gluten oxidized in a state of eremacausis, or slow combustion, whilst the ordinary surface yeast is gluten oxidized in a state of putrefaction, and the former, when added to wort at a low temperature, is incapable of causing the direct oxidation of the gluten dissolved in the wort, although it possesses the power of causing the transformation of the saccharine matter into alcohol and carbonic acid. In the Bavarian process, the oxidation of tbe gluten has to be effected by .the action of tho atmosphere, and the large area exposed by the fermenting vessels, together with the freedom of the surface of the hoer from any proteeting layer of yeast, gives every facility for this atmoapberic action. It might be suppoaed that the atmospheric action which causes the Bavarian heer to deposit its gluten would also induce an acetic fermentation iu the wort. Such an occurrence is prevented by the low temperature maintained in the fermenting rooms, a temperature below that at which acetic fermentation of alcohol will take place.
The unterhefe employed by thc Bavarian brewers may, by some expenditure of time and trouble, be prepared from ordinary yeast. If some of the latter be added to wort at the low temperature of 8° to 10°, and a slow fermentation allowed to take place, the yeast will be partly deposited and partly carried up to the surface. If this deposited yeast be e,ollected to produce another fermenta tion, thia will result in the depoaition of a bottom yeast still more resembling unterhefe ; and by repeating these operations, unterhefe is at length obtained.