644 MICROBIOLOGY OF ALCOHOLIC FERMENTATION 



which the proper amount of liquid is added every day after a correspond- 

 ing amount of vinegar has been removed. These two vats constitute a 

 unit, several of which, usually six, are united in a battery. A factory 

 includes several of these batteries. 



The batteries are fed from a large vat or reservoir, where the mixture 

 of wine and vinegar is prepared and stored. The vinegar drawn from 

 the batteries runs directly to filters, thence to a pasteurizer, and finally 

 to the storage casks. 



The output of these batteries is from two to five times as great per 

 square meter of acetifying surface as that of the old method; the cost 

 of the operation is considerably less, the loss by evaporation much 

 reduced and the quality equal and much more under control of the 

 manufacturer. 



RAPID METHODS. In all the methods described, the surface of the 

 liquid exposed to air, where alone acetification occurs, is small compared 

 to the volume of the liquid. In order to hasten and therefore cheapen 

 the process, various devices for increasing the surface in contact with 

 air have been devised. The simplest of these is one sometimes em- 

 ployed in wine-making countries. The pressed pomace of red wine is 

 broken up and placed loosely but uniformly in a tall narrow vat. In a 

 few days, acetic fermentation commences in all parts of the mass. 

 Wine is then sprinkled periodically on top and trickling down over the 

 pomace, it is changed to vinegar by the bacterial film which encases 

 every particle of the mass. The " quick " or German method of vinegar- 

 making is based on this principle. 



The apparatus used in this method consists of a tall cylindrical or 

 slightly conical wooden vat provided with a perforated false head a few 

 inches from the bottom and another, similar in structure, at the same 

 distance from the top. The space between these two false heads is filled 

 with long thin chips or shavings of beech wood which have been thor- 

 oughly extracted, first with water and then with good strong vinegar 

 (Fig. 1 60). Various substitutes for beech chips have been used with 

 more or less success. Rattan shavings and wastes are suitable; dried 

 corn-cobs can be used but are not durable; wood charcoal in lumps is 

 used successfully; coke is as effective as wood charcoal and more 

 durable and is now used extensively in the manufacture of alcohol 

 vinegar. 



In operation, the liquid to be acetified is distributed over the top 

 false head intermittently in small amounts. This intermittence of 



