95 



The following 1 is quoted from Dr. Cluss: a 



Under fermentation in its widest sense we understand every change in a substance 

 that is brought about, either directly or indirectly, by the activity of low plant forms. 

 Under fermentation in a narrower sense, or alcoholic fermentation, we understand 

 every change in a substance by which certain kinds of sugar are decomposed through 

 the activity of germs, so that, as the principal products of this decomposition, alcohol 

 and carbonic-acid gas appear. 



In alcohol fermentation, as in every form of fermentation, we must consider three 

 principal factors: 



(1) The fermentation material, or the substance which is to be decomposed. 



(2) The fermentation products; that is, those bodies that arise from the decompo- 

 sition of the sugars. 



(3) The controlling organisms of the fermentation; i. e., those plant forms which 

 cause the decomposition. 



The fermentation material for alcoholic fermentation is provided by certain kinds 

 of sugar, but not all kinds of sugar are capable of being fermented. Among those 

 that can be fermented are grape sugar, fruit sugar, r^alt sugar, and cane sugar. But 

 while in the brew mash and in the wort of the breweries malt sugar predominates, 

 in fruit juice grape sugar and fruit sugar play the principal role as fermentation 

 material. 



The principal products of alcoholic fermentation are ethyl alcohol (badly named 

 alcohol) and carbon dioxid (CO 2 ); but there are also small quantities of sulphuric 

 acid, glycerin, and other by-products, among these being certain aromatic sub- 

 stances of great importance in wine fermentation. If the sugar were separated 

 evenly into alcohol and carbon dioxid, then out of 100 parts of grape sugar there 

 would arise 51.11 parts of the former and 48.89 parts of the latter. But only about 

 94 or 95 per cent of the sugar is consumed in the pure alcoholic fermentation, and 

 the remaining part serves for the building up of these minor products and for the 

 nourishment of the yeast germs. Thus it must be concluded, according to Pasteur, 

 that out of 100 parts of grape sugar arise 48.5 parts alcohol, 46.6 parts carbonic acid, 

 3.3 parts glycerin, and 0.6 part sulphuric acid, while about 1 per cent of the orig- 

 inal sugar is used for the building up of the yeast cells. 



We have the yeasts in the widest sense of the word that is, the different kinds of 

 fungi, as the sprouting fungi, mold fungi, and splitting fungi, which may form 

 alcohol; but above all the rest the sprouting fungi, as the yeast in a narrower sense 

 of the word, play the most important role. 



While the stages of fermentation as they should normally occur in 

 the casks or vats will now be dealt with, it should be noted that there 

 is always a possibility that mal-organisms may at any time gain con- 

 trol of the must and produce results very different from those desired. 

 These accidents of the fermentation room are due to some of the fun- 

 gous plants and bacteria which are constantly associated with the true 

 alcoholic ferments under all ordinary conditions. 



FIRST OR TUMULTUOUS FERMENTATION. 



Given the proper temperature conditions, apple must at once takes 

 on a very active fermentation, which has been variously denominated 

 as ''tumultuous," "stormy," etc. The activity is greater in weak, 

 acid juice than in rich must of good quality. Its progress is marked 



" Free translation from Dr. A. Cluss, "Apfelweinbereitung," pp. 63-64, 1901. 



