412 BACTERIA IN THE ARTS AND INDUSTRIES 



Bacterium schufaenbachi and several related species are the main 

 factors in the production of vinegar by the quick-vinegar process. 

 The organisms vary considerably in size 0.3 0.4/u x 3 6/x. Their 

 optimum temperature is 25 30 C. They produce as high as 

 11.5 per cent, acetic acid. In the absence of sufficient alcohol the 

 acetic acid may be oxidized by them to carbon dioxid and water. 



Two methods of preparing vinegar are in general use (1) the 

 Orleans and (2) the Quick, or German Method. 



1. The Orleans Method is the oldest commercial method and 

 produces vinegar of the highest quality. There are many modifica- 

 tions of this method but they all contain essentially the same 

 principles. The filtered wine is placed in barrels or covered vats 

 furnished with openings so the entrance of air is facilitated and can 

 be controlled. The receptacle is filled about two-thirds full of a 

 mixture of four parts of good, new vinegar and six parts of wine, 

 preferably that which has been pasteurized at 55 C. At times 

 there is placed a light wooden grating which floats and helps to 

 support. the bacterial film. A small quantity of a good bacterial 

 film is placed in as a starter. Periodically a portion of the contents 

 is drawn off and replaced by wine, and so the process continues. 



2. In the Quick or German Method the liquid to be acetified 

 is allowed to trickle through barrels filled with beech chips, the 

 pressed pomace of re4 w r ines, rattan shavings, corn cobs, or charcoal. 

 Although the main function of these is to increase aeration, yet the 

 best results are obtained with the beech shavings or pomace. 



Sauerkraut. The cabbage is cleaned, cut into pieces of con- 

 venient size, and tightly packed with from 1 to 3 per cent, of salt 

 into wooden or earthen vessels on the top of which is placed a 

 weighted perforated cover. This, together with the osmotic press- 

 ure of the salt, draws from the vegetable considerable water. The 

 respiration of the cells of the leaf and the yeast soon remove all 

 oxygen. The mass undergoes lactic acid fermentation which in 

 time reaches from 0.5 to 1 per cent. The brine is then drawn off 

 and replaced by 4 to 8 per cent, salt solution. In this the vegetable 

 will keep for a considerable time. Many substances are produced 

 in the process, the chief of which are lactic acid, alcohol, succinic 

 acid, volatile acids, mannite, amid bodies, carbon dioxid, hydrogen, 

 methane, and various aromatic esters. 



The bacteria responsible for the process come from the vegetable. 

 Although Weiss has isolated 65 different species of bacteria from 

 sauerkraut, probably the principal changes are due to a few species. 

 The lactic acid is usually produced by Streptococcus lacticus and 

 Bacterium lactus acidi. 



By similar means other vegetables stringbeans, cucumbers, 

 etc. may be preserved. 



