188 AGEICULTUEAL AND INDU8TEIAL BACTERIOLOGY 



possess the power to ferment lactose'. A few species are 

 known, however, which do have the power of developing 

 lactase, therefore they are capable of fermenting milk. 

 Alcoholic milk beverages have been prepared in many coun- 

 tries. The alcoholic fermentation in this case is usually 

 accompanied by the formation of lactic acid as well, the 

 product being a type of sour milk with a low percentage of 

 alcohol. 



Beer and ale are prepared by soaking malt in water to 

 allow the action of the diastase upon the starch, transform- 

 ing it into the sugar maltose. Certain proteolytic enzymes 

 at the same time dissolve portions of the protein content of 

 the malt. The solution is termed beerwort. To this, both in 

 order to control undesirable fermentation and to impart a 

 desirable flavor, an extract of hops is added. This hopped 

 wort is then placed in large fermenting vats and yeast 

 added, usually in pure culture. Fermentation proceeds 

 until the desired concentration of alcohol has been secured. 

 When fermentation is complete, the beer is clarified and put 

 in bottles or kegs for distribution. The character of the 

 product depends in large measure upon the kind of yeast 

 used, particularly upon the use of bottom or top yeast. , 



Preparation of Distilled Liquors.— By a process of dis- 

 tillation the percentage of alcohol present in the final 

 product may be greatly increased. Rum is prepared by 

 fermenting molasses, the resulting alcoholic solution being 

 distilled and flavored. Brandy is prepared by the prepara- 

 tion of wine or eider. Whisky is prepared by the inocula- 

 tion of a mash made of malt and either ground grains or 

 potatoes, which is then inoculated with yeasts. "When the 

 alcohol content has reached a sufficient degree of concentra- 

 tion and the fermentation is "complete, the alcohol is distilled 

 over and the product aged in suitable containers. 



Manufacture of Commercial Alcohol. — The primary 

 requisite for the manufacture of alcohol on a commercial 



