216 OUTLINES OF BACTERIOLOGY 



particularly obnoxious, if they multiply, for a small quantity of butyric 

 acid can go a long way towards spoiling the whole brewing. 



(b] Whiskey. The preparation of whiskey does not differ in essen- 

 tials from the process just described for the production of beer, except 

 that, as a much higher percentage of alcohol is desired, distillation is in 

 addition resorted to, in order to achieve this end. There are two 

 varieties, viz., malt whiskey and grain whiskey. The former, which is of 

 finer quality, is made principally from malted barley, or, more rarely, 

 from rye. The latter is cheaper, but stronger, and is made from 

 various substances, as sugar, molasses, potatoes, but principally from 

 unmalted grain, as Indian corn, barley, oats, etc., dried and ground up. 

 The principal ingredient in all these substances is either starch or 

 sugar. The fermentation is essentially the same, and as a matter of 

 fact most of the distilleries in this country get their yeast either 

 directly or indirectly from the breweries. The fermentation, however, 

 is of a more difficult nature, because the liquid to be fermented, the 

 " sweet goods," as it is called, instead of being self -clarifying, like wort, 

 and thus easily separated from the yeast, is usually a thick mash in 

 which the yeast cannot settle down. Instead, therefore, of directly 

 adding the yeast to the " sweet goods " contained in the principal 

 mash-tun, a preliminary and important fermentation is effected, which 

 is very instructive as illustrating the manner in which a desired 

 fermentation can be accomplished under difficulties. The distiller 

 removes a certain small amount of " sweet goods " from the principal 

 mash-tun, and adds to this crushed green malt which has been mixed 

 with water, and gradually warmed to 67-70 C. The whole mixture 

 is next allowed to sweeten for about two hours at 70 C. Sweetening 

 will take place because the diastase in the malt will change the starch into 

 sugar. Now, a sugary solution of this nature is an unusually good 

 nutrient medium for all kinds of bacteria, and the ones that are most 

 to be feared are the species belonging to the butyric-acid bacteria, 

 which unfortunately are almost always present. If these multiply to 

 any appreciable extent, the whole fermentation will be destroyed. To 

 remove all risk of this happening, the distiller acts as follows : He first 

 introduces lactic-acid bacteria to a small portion of the " sweet goods." 

 Now it is known that these organisms thrive best between 47 C. and 

 52 C., whereas the butyric-acid bacteria prefer a temperature near 

 40 C. He therefore keeps the temperature of the mixture at about 

 50 C., with the result that the acidity which develops is due to lactic 

 acid. Then, when the necessary degree of acidity has been attained, 

 sufficient heat is applied to cause the death of the lactic-acid bacteria. 



