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900 | REPORT OF THE COMMISSIONER OF AGR 
The temperature at which the fermentation is carried on has a 
very decided influence upon the character of its product, and the 
practice differs in different countries in this respect. In California, ai 
Spain, South of France, Austria, and Hungary fermentation is con- — 
ducted at a comparatively high temperature, 15° to 20° C., while in ~ 
Germany a low temperature, 5° to 15° C.,isemployed. As with beer, — 
the yeast of either variety of fermentation, high or low, reproduces 
the same kind of fermentation in musts to which it is added, but the 
subject of the different ferments as applied to wine has not been so- 
carefully studied as with beer. The high fermentation is said to — 
give a wine rich in alcohol but lacking in bouquet, while the reverse 
is the case with the low fermentation. 
The duration of the fermentation varies with the temperature, the . — 
amount of sugar to be transformed, etc. ; the completion of the pro- 
cess may be known by the cessation of the disengagement of carbonic 
acid gas and by the diminution of the specific gravity of the liquid, 
so that the areometer marks zero or less. aes ; 
After fermentation is complete, the wine is drawn off from any ~ 
sediment it may contain into casks or barrels, where a second slow 
fermentation takes place, continuing sometimes several months. 
When it is over, the wine is ‘‘ racked off ” into fresh casks, which are - 
closely bunged up. The operation of racking off may have to be 
repeated several times, and it is sometimes necessary to addiisinglass — 
or other gelatinous material, which serves to clarify the liquid, acting © 
on the tannin which it contains. This operation is called ‘‘ fining.” 
CHANGES PRODUCED BY FERMENTATION. 
The principal change in the chemical constitution of the must pro- 
duced by fermentation is the conversion of the sugar into alcohol .~ 
and carbonic acid. One hundred parts of sugar produce 50 parts of 
alcohol, inround numbers. All the sugar, however, is not converted 
into alcohol and carbonic acid ; a small part isconverted into glycer- 
ine and succinic acid. 
The bitartrate of potash, being-insoluble in alcohol, is gradually: 
deposited as the content of alcohol in the wine increases, and forms 
the substance known as ‘‘argol” or crude tartar. This distinctive 
constituent, tartaric acid, constitutes the superiority of grapes over 
other fruits for wine-making purposes, the comparative solubility 
of its acid salts furnishing a means of removing the excess without 
the addition of other chemical agents. 
Other changes take place, especially during the slow second fer- 
mentation, not so well defined or so well understood as those men- 
tioned, but of great importance in their relation to the quality of the 
final product. These changes, which continue after the fermentation 
has ended, constitute what is caHed the ‘‘ageing” of the wine and 
produce its *‘ bouquet” or flavor, generally attributed to the ether- 
ification produced by a slow action of the acids upon the alcohols. 
Wine improves with age, but there isa limit after which it degener- 
ates again and loses its flavor. 
METHODS FOR “‘IMPROVING™ WINES. 
-In France and Germany several methods are in use for increasing \ 
the yield of wine or improving its quality. These are especially re- ~ 
sorted to in unfavorable seasons, when the want of suificient sun 
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