MICROBIOLOGY OF ALCOHOL AND ALCOHOLIC PRODUCTS. 437 



or four times its weight of water and a little malt to 80 to 85 for about 

 an hour. 



The methods of mashing are very various. They consist in general of mixing the 

 ground malt with warm water, bringing the mass to a temperature of 35 to 45 which 

 is gradually raised to 60 to 65 by the addition of hotter water. The action of the 

 enzymes commences, the heated decoction of unmalted grains is added in various ways, 

 and the temperature controlled by additions of hot water or by heating a portion of 

 the mash. The whole mashing process requires from two to five hours according to 

 the methods used. 



During the mashing the starch is transformed partly into maltose and partly into 

 dextrins. The ratio of these products will vary according to the amount of amylase 

 present and especially according to the temperature used. At about 60 the maximum 

 amount of maltose is produced; at higher temperature (65 to 75) the unfermentable 

 dextrins increase. The amount of alcohol and the amount of extract in the beer there- 

 fore depend to a great extent on the method of mashing. 



During the first part of the mashing, while the temperature is about 

 45, lactic bacteria develop. If their action is too intense they will 

 render the beer unpleasantly acid. If moderate, the acidity they com- 

 municate to the wort is useful in preventing the growth of the harmful 

 butyric bacteria which might develop. 



After mashing, the wort is separated from the solid matters by drawing off, 

 extracting the mash with hot water (sparging), and nitration. It is then boiled from 

 one to eight hours according to the result desired. 



Boiling sterilizes the wort, kills all bacteria and destroys any enzymes 

 which remain. This occurs almost instantaneously owing to the lactic 

 acid present. Coagulation of protein substances is also brought about, 

 effecting a clarification of the wort. This requires one or more hours, 

 according to the nature of the wort. It is necessary also in some cases 

 to concentrate the wort, which is done by prolonged heating in open 

 kettles. This may require several hours. 



The Hopping of the wort takes place during the boiling. Sometimes 

 the hops are added just at the end of boiling; sometimes in two or three 

 portions, one of which may be at the beginning and one after boiling. 

 Hops contain an aromatic essential oil, resins and tannin. The essential 

 oil is quickly soluble and volatile; to preserve its aroma in the beer, the hops 

 must not be boiled too long. The resins are antiseptic and help to pre- 

 serve the beer. They dissolve with more difficulty and require longer 

 boiling. 



