EXPERIMENT STATION BULLETINS. 509 



with a little vinegar and thoroiiglilj stirred iuto the cask. With some 

 vinegars it is necessary to add a little tannin, from one-half to one- 

 seventh the amount of the isinglass used. This tannin should be added 

 at least twentj-four hours before the finings." Gelatin may also be 

 used. For proportions see page 514. 



"When the finings have settled and the vinegar is perfectly bright it 

 is ready for bottling. The bottles after filling and corking should be 

 pasteurized by heating in a water bath to 140 degrees F. Vinegar treated 

 in this way will keep for years without deteriorating." 



Pasteurization: After the acetic fermentation is complete, in order* 

 to prevent further fermentation changes, pasteurization is often resorted 

 to before storing. This is heating the vinegar to 140 degrees F., a tem- 

 perature suflQcient to destroy all forms of life which would be injurious 

 to the vinegar. During this heating the vinegar should not come in 

 contact with metal of any sort. In the ordinarj^ household, only the 

 highest quality, uuchipped and uncracked enamelware kettles should be 

 used. 



The barrels or casks in which the vinegar is to be stored should be 

 clean and thoroughly scalded just previous to pouring in the pasteurized 

 vinegar, filled, bunged, and stored in the manner before noted. 



THE '"'^QUICK VINEGAR PROCESS." 



As the acetic bacteria need air to oxidize the alcohol in cider, etc., 

 it is evident that in the ordinary vinegar barrel the surface of the 

 alcoholic liquid exposed to the air is very small in proportion to the 

 volume of the liquid. This is the reason why vinegar made by the 

 household method is formed so slowly. 



In the "quick vinegar process" the vinegar generator is so constructed 

 as to multiply many hundred times the area of the surface of the alco- 

 holic liquid thus increasing the activit}^ of the vinegar bacteria by as 

 many hundred times. The best type of "quick process" generator is 

 constructed of a slightly conical wooden vat, having two perforated false 

 heads, one near the bottom and the other near the top. The space be- 

 tween these two false heads is filled with shavings of beech-wood or strips 

 of rattan which have been thoroughly extracted, first with water, then 

 with good strong vinegar. (See Fig. 6.) Various substitutes for beech 

 shavings such as corn cobs, etc., have been used with more or less success. 



When the generator is in operation the alcoholic liquid is distributed 

 intermittently by some automatic device over the top false head in small 

 amounts. The liquid is supplied intermittently rather than continu- 

 ously so that it will not tend to run in streams in certain parts of the 

 vat and thus cause a loss of acetifying surface. If the flow is too rapid 

 the bacterial film is washed down from the ui)per part of the mass of 

 beech shavings and only the lower part is effective. 



On the surface of the shavings, the vinegar bacteria grow in a thin mem- 

 brane and as the fermented liquid trickles in a thin film over the bac- 

 teria, the alcohol is rapidly oxidized to acetic acid. 



By the time the alcoholic liquid has reached the lower false head the 

 larger amount of it has been acetified. It is generally necessary to pass 

 the alcoholic liquid through the same vat from two to five times, or 

 through a series of vats, to change all the alcohol into acetic acid. 



