212 BACTERIOLOGICAL METHODS 



ration and undoubtedly the microscope alone will in most in- 

 stances reveal the presence of numerous abnormal and objec- 

 tionable organisms, even before the expert taster has been able 

 to appreciate any abnormal alteration in flavor or in bouquet. 



The following is a very brief outline of the principal fermen- 

 tations concerned in the manufacture of alcoholic beverages. 



A. Alcoholic Fermentation. — The alcohol forming ferments or 

 zymases, or yeast ferments proper, are by far the most common 

 and most widely distributed in nature and the most important 

 from a commercial and economic standpoint. The zymases act 

 upon sugars splitting these into alcohol and carbonic acid gas, 

 thus acting upon the end products formed by the diastases and 

 preparing them for the action of the acid forming ferments. 



Zymases are formed by a great variety of plants and animals, 

 more generally by the so-called yeast plants (the Saccharomyces 

 and Torula groups). The alcohol-generating enzymes formed 

 by these plants are capable of being isolated or separated from 

 the living cells which form them and may continue the fermenta- 

 tive activities indefinitely. Alcoholic fermentation is by no 

 means a simple process. The degree of alcohol production 

 and by-product formation varies greatly, depending upon a great 

 variety of factors and influences. To enter into a fuller dis- 

 cussion of the details of the fermentative processes and a de- 

 scription of the organisms involved, is not practicable or essential 

 for the present purpose. The number of saccharine substances 

 capable of undergoing alcoholic fermentation is legion, and it 

 has thus far not been possible to ascertain the number and variety 

 of yeast organisms and associated organisms which are involved 

 in the multitudinous fermentations (natural and artificial) 

 resulting in the formation of alcohol. In commercial practice 

 (in the manufacture of wine, beer, brandy, etc.), a distinction is 

 made between upper yeasts, lower yeasts, wild yeasts, etc. In 

 some breweries lower yeasts are the chief fermenters used and in 

 others the upper yeasts are preferred. For example, it is claimed 



