FERMENTATION

"FERMENTATION"

The process of fermentation takes about 3-4 days, and is the result of
the action of natural yeast (saccharomyces ellipsoides) on grape sugar. From
white (pale) grapes-white wine is obtained, and from red grapes, white, red and
rose wines are obtained. The skins of the grapes contain most of the pigments;
therefore if the skins are removed from the Must before fermentation, a white
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By the action of yeast
P aper - II Food and Beverages Services - II 73
wine is obtained. If allowed to remain in the Must for a short time (usually a few
hours), a rose wine is obtained. If the skins are removed only after fermentation
is over, a red wine is obtained.
Nowadays, fermentation takes place in thermostatically controlled
fermentation tanks, keeping the temperature within the range of 60 to 80oF.With
the onset of vigorous fermentation, heat is produced. To prevent excessive heat
(which would inactivate the yeast and thus halt fermentation), cold water is run
through pipes embedded in the tanks; this has a cooling effect. If the temperature
is too low, hot water is run through the pipes.
Fermentation takes place on its own. However, to produce a sweet
fortified wine (a fortified wine has an alcohol percentage of 18-25%), a definite
amount of Brandy is added during fermentation. Due to this, the alcohol content
of the wine increases and yeast is inactivated.
For a dry fortified wine, Brandy is added after fermentation (when all
the sugar will have been used up the yeast), which increases the alcohol content
of the wine.
Grapes sugar may be added to wine in certain circumstances. Grapes,
which have a lot of sugar but less yeast, are used for many sweet wines. Whole
grapes that have more yeast but are less sugary used in dry wines.