2l6 ALCOHOL, VINEGAR, SAUER KRAUT, TOBACCO, SILAGE, FLAX. 
of bacteria. The first of these is sour bread, due to the growth in 
the dough of acid-forming bacteria. This occurs most commonly 
when the raising is allowed to continue too long or at too high a 
temperature. The bacteria in question will not produce trouble 
if fresh yeast be used and the raising be completed in less than 
eight hours' time. A second fault, due to bacteria, is slimy bread. 
This is of rare occurrence, though sometimes it will infect a bakery 
and continue day after day. This bread, when fresh, appears normal ; 
. but after a few hours it becomes slimy, so that, 
^ // when broken, it appears as if filled with cobwebs. 
\f/ 4\ The trouble is due to bacteria, the source of which 
} t may be either the utensils, the flour, or the yeast 
F IG> 47 _The (Fig- 47). The remedy is in cleaning and steriliz- 
bacteria that cause mg a ^ baking dishes. If this does not remove the 
slimy bread. 
trouble it is well to change the brand of flour or 
get a fresh supply of yeast. The trouble may also be relieved by 
keeping the bread cold so as to prevent bacteria growth. The 
addition of a little lactic acid to the dough, or the use of equal 
parts of sour whey and water in mixing the dough, is also recom- 
mended as a remedy, based upon the fact that lactic acid bacteria 
will check the growth of other organisms. 
VINEGAR-MAKING. 
Vinegar is used both as a direct condiment to give relish to foods 
and as a preservative, as in the manufacture of pickles. It is made 
on a large scale in vinegar factories and on a small scale on farms. 
It is always made from some weak alcoholic solution, like cider, 
weak wine, or beer, each locality using as a source the alcoholic 
solution most easily obtained. The essential part of the process 
is the chemical union of the alcohol with oxygen from the air, by 
which it is converted into acetic acid. Such a simple oxidation can 
be brought about by a purely chemical process. As long ago as 
1721, Davy discovered that platinum-black, 4 or finely divided plati- 
num, when mixed with alcohol, causes an active union with oxygen 
to take place, which results in the production of acetic acid. 
