II.— THE COMPOSITION OF CIDER AS DETERMINED BY DOMI- 
NANT FERMENTATION WITH PURE YEASTS. 
By Wm. B. Alwood, R. J. Davidson, and W. A. P. Moncure. 
WORK OF 1901-2. 
INTRODUCTION. 
In the autumn of 1901 a series of experiments upon the manufacture 
of eiders with pure yeast cultures was begun at the Blacksburg station 
in cooperation with the Bureau of Chemistry. 
The apple must or juice used for this experiment was made with the 
power mill belonging to the station from ordinary mixed apples. 
mostly of inferior varieties. Immediately after pressing, the juice 
was placed in sound, clean, 50-gallon casks, and these were at once 
bunged to prevent further access of organisms to the juice until it 
could be sown with yeast. These casks, or 50-gallon barrels, were 
placed on the second floor of the factory building and were sown with 
yeast cultures about three hours after grinding the fruit. In these 
experiments, which were made on a scale comparable with commercial 
work, the juice or must was not sterilized or pasteurized before sow- 
ing with the pure yeast cultures. While the destruction by use of 
heat of the many microscopic organisms always present in fresh fruit 
juice is practicable, even on a large scale in factory work, as yet it has 
not been found to be desirable for commercial ciders. Heating the 
must causes such changes in the flavor that the most careful cellar 
work and use of pure ferments has failed to counteract this effect, and 
thus the fine natural flavors are quite commonly injured by attempts 
at sterilization. 
Control or dominant fermentation is easily secured if one sows a 
sufficient amount of fresh culture of a strong yeast into the newly 
made must. The question of the relative activities of the pure fer- 
ments in comparison with mixed yeasts and " wild" ferments in steril- 
ized and unsterilized must will be treated in a subsequent paper which 
will deal more specifically with the ferment organisms. The station 
i^ without suitable cellars or fermentation rooms, and therefore this 
work was done under such varying conditions of temperature that the 
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