94 



As by the addition of pure yeast fermentation starts up sooner, and also runs its 

 course more quickly, the temperature of the fermenting rooms must not be too high, 

 or else too violent a fermentation will be induced. It is sufficient to Avarm the fer- 

 menting rooms or cellars to about 55° to 60° F. Also it is best to leave plenty of 

 space in the casks for foam and vegetable matter thrown up by fermentation. 



With pure yeast cider will be finished earlier and clear itself sooner than when 

 fermented without the addition of pure yeast; therefore, with this method cider 

 must be racked off earlier than in case of spontaneous fermentation. 



OBSERVATION AND CONTROL OF FERMENTATION. 



The theoretic di.sciission of the physical phenomena involved in this 

 process is not to be attempted here, and the brief discussion given is 

 only warranted in such a report as this for the sake of rendsring com- 

 prehensible the operations and details described. 



DEFINITION AND DESCRIPTION OP FERMENTATION. « 



There was a time when this word was used to indicate the entire 

 range of chemical changes which might occur in organic substances. 

 To-day, with more exact knowledge on the subject, fermentation is 

 limited to those changes which are induced by the growth of micro- 

 scopic plants in organic substances. In the case of fruit juices, these 

 organisms are bacteria and the true fungi, principally the latter. The 

 fungous organisms considered belong to the group known as the 

 Saccharomyces, or yeast fungi, to other closely related nonnwcelial 

 forms, and to the Mucorini and some few other true mycelial forms. 



Fermentation as I'elates to the physical phenomena involved may be 

 defined as the breaking up of organic substance in solution as a result 

 of the chemical activities of certain substances secreted during the 

 growth of these microscopic plants; and alcoholic fermentation, as 

 the result of the breaking up of sugars into alcohol and carbonic acid, 

 caused by the action of zymase, a ferment secreted during the growth 

 of the yeast plants. Incidentally, sugar may be broken up into alcohol 

 and carbon dioxid by a few other fungous forms. The j^easts, or Sac- 

 charomyces proper, are, however, the true alcoholic ferments. Other 

 forms need be only incidentally considered. The normal substratum, 

 or place of growth of the yeasts proper, is the sugar solutions con- 

 tained in the juices of fruits, or sugary compounds, in whatever parts 

 of various plants they may occur. As a result of the growth of these 

 yeast fungi, alcohol and carbon dioxid are formed. The first remains 

 in the liquid and the second largely escapes as a gas. Theoretically, 

 about 51.11 parts of alcohol will be formed and al)out -18.89 parts car- 

 bon dioxid. Or we may say in general terms that the alcohol formed 

 by properly controlled fermentation will practically equal one-half the 

 sugar destroyed. The yeasts are said to consume a small percentage 

 of the alcohol. 



« Adapted from a paper presented by the writer before the American Pomological 

 Society, September, 1901. 



