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A TREATISE ON
vinegar. 5th. The
putrid fermentation,
which is
exhibited in its most marked form in the putrefac–
tion of animal substances.
As the first applies more particularly to the pro–
cess of fermenting grain, it will be alluded to again
under the head of "Malting."
The second, the
<ilcolwlic
or
vinous fermentation,
we will now speak of in detail, as applicable to the
fermentation of the juice of the grape. This stage
of
ferm~ntation
converts sugar into alcohol, by the
peculiar decomposition which sugar undergoes under
certain circumstances, by which carbonic acid is
eliminated and alcohol obtained. The presence of
a ferment is essential to excite this fermentation, as
a solution of perfectly pure sugar will remain unal–
tered, even though exposed to a temperature of 70°
to 75° F., which is the most favorable forits produc–
tion. But
if
a small portion of yeast, or of a similar
saccharine solution, whose molecules are in a state
of motion, be added, the usual symptoms offermenta–
tion will rapidly occur, and will continue until nearly
the whole of the sugar is decomposed, when the
liquid will become clear, and be found to consist of
diluted alcohol, while the yeast will have precipitat–
ed to the bottom and have lost its power of fermenta–
tion.
In
the juices of
sweetfruit,s,
and in those vegetable
Digitized
by