Studies on Fermentation: The diseases of beer, their causes, and the means of preventing themPasteur, Louis
Science
Studies on Fermentation: The diseases of beer, their causes, and the means of preventing them
Pasteur, Louis
Beer; Fermentation
“Fig. 6 (Fig. 28 in this work) represents a very interesting variety of
alcoholic ferment. It happens pretty often, especially in the Jura,
where the vintage takes place about October 15th, when the season is
already cold and little favourable to fermentation, that the wine is
still sweet at the moment when it is put into casks. This is especially
the case in good years, when the sugar is abundant and the proportion of
alcohol high, a circumstance which prevents the completion of
fermentation when effected at a low temperature. The wine remains sweet
in cask sometimes for several years, undergoing a continuous but feeble
alcoholic fermentation. In such wines we have always observed the
presence of this peculiar ferment. In form it consists of a principal
stem, forming nodes at various points, from which short branches arise,
ending in spherical or ovoid cells. These cells readily detach
themselves, and act as spores of the plant. It is rarely, however, that
we see so perfect a vegetation as we have represented, because the
different parts fall to pieces, as we have shown in the left half of the
figure.”
What is the origin of cellular plants of this remarkable type? Where and
how are the ferments of the grape generated?
In Chapter III. § 3 we were on our way to a solution of this question.
It has been shown that fermentation cannot take place in the juice of
crushed grapes if the must has not come into contact and been mixed with
particles of dust on the surface of the grapes, or of the woody part of
the bunch. It would, however, be sufficient that a vintage vat, of any
capacity whatsoever, should receive the particles of dust existing on a
single bunch in some cases, on even a single grape, for the whole mass
to enter into fermentation.
[Illustration: Plate 8. Fertile Mould-cells from the Outer Surface of
Grapes.]
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