FERMENTATION OF CARBOHYDRATES 185 



and most easily available form of carbohydrate. Inasmuch 

 as these cannot be attacked directly by yeasts, if they are to 

 be used in alcoholic fermentation they must be hydrolyzed 

 into sugars which can be directly attacked. Several methods 

 have been worked out for this purpose. 



When starch or cellulose are heated in the presence of 

 acids and water they are more or less- rapidly broken down 

 into dextrins and finally into dextrose. Some attempts have 

 been made upon a commercial scale to hydrolyze the cel- 

 lulose of sawdust and wood to dextrose, utilizing" the sugar 

 formed for yeast fermentation. The commercial manu- 

 facture of glucose from starch is based upon the acid 

 hydrolysis. 



A much more convenient method of preparing sugar from 

 starch, preliminary to alcoholic fermentation, is by the use 

 of malt. Malt is usually prepared from barley. This is 

 steeped or soaked in warm water for twenty-four hours, 

 drained and kept exposed to the air, thoroughly stirred and 

 moist, until it germinates. Various mechanical devices are 

 used for this purpose. In some cases large revolving drums 

 containing the moist barley are used. In other cases large 

 tanks with mechanical stirrers are employed, and in still 

 others the malt is spread out on the floor and turned over 

 with shovels, by workmen. An examination of a barley 

 grain, or the grain of any grass, will show that the young 

 plant or germ lies on one side near the base of the starch or 

 endosperm of the seed. The major portion of this germ is 

 made up of a comparatively large shield-shaped organ 

 called the scutellum. When the seed is soaked and started 

 to germinate, certain cells of this scutellum form consider- 

 able quantities of the enzymes amylase or diastase. As the 

 plant begins to grow this diastase diffuses out into the 

 endosperm, transforming the starch into soluble sugars, 

 which may be absorbed by the growing plantlet and used as 

 food. The maltster has learned to recognize that stage in 



