12 
The Colorado Experiment Station 
germs. This may be carried out in a number of different ways, 
but preferably by means of a pure culture of a desirable organism 
which has been selected because of its ability to produce strong 
acetic acid and to impart an agreeable flavor to the vinegar. In 
place of the pure culture starter, one may add two to four quarts 
of good cider vinegar containing more or less “mother” for each 
barrel. The introduction of a desirable organism is left to chance 
in this case. A serious objection to this latter method is that some¬ 
times one introduces foreign organisms with the “mother” which 
may prove detrimental to the vinegar. The pure culture starter 
is free from this objection. On the whole, the indiscriminate use 
of “mother” alone is to be discouraged, since the popular idea of 
what constitutes “mother” is apt to be wrong. Pure “mother” is 
made up exclusively of acetic acid bacteria and is recognized as the 
thin, white, glistening, gelatinous membrane that forms on the 
surface of vinegar. It seldom becomes one sixteenth of an inch 
in thickness and should be translucent or white in color. It is en¬ 
tirely distinct from the thick, tough, dark brown, slipping, leathery 
masses which form in vinegar and are usually regarded as “mothy 
of vinegar.” Such accumulations contain the acetic acid germ, in . 
all probability, but in an impure state. In addition to this organ¬ 
ism there may be present yeast cells and numerous bacteria which 
are positively harmful to the vinegar. Often these growths undergo 
decomposition and give the vinegar a flavor of rotten oranges. 
Again the germs present may cause the partial or complete loss of 
the acid, particularly if the barrels are not full and tightly stop¬ 
pered. All things taken into consideration, the use of this sort of 
“mother” is a rather dangerous procedure. 
With the acetic fermentation, as with the alcoholic, the higher 
temperatures favor the changes. Experimental work shows that 
hard cider to which no acetic acid bacteria were added other than 
those that came from the air, and kept at 65 degrees F., when six 
months old, contained 7.03 per cent, of acetic acid, while that held 
at 55 degrees F. showed only 3.63 per cent. 
The addition of some kind of an acetic acid starter, either 
as a pure culture of the acetic organism or as good vinegar, hastens 
the fermentation and reduces appreciably the time required for 
making marketable vinegar. 
For most satisfactory results we would recommend using the 
pure cultures and holding the vinegar at a temperature of 6q to 75 
degrees F. Under these conditions, salable vinegar can be obtained 
in three to six months in nlace of two to three years, as is often 
