YEASTS AND MOULDS. 



149 



In beer making, the barley grain is first acted upon by the starch enzyme 

 (diastase) which converts the starch into maltose (malt) and the maltose is in 

 turn converted into alcohol by the Saccharomyces. If the fermentation 

 product (as grape wine, apple cider, beer, porter, etc.) is exposed to the air 

 for a time, the Mycoderma aceti enters and at once begins to convert the 

 alcohol into acetic acid and we finally have vinegar. "Hard cider" is simply 

 apple wine in which the acetic acid fermentation has progressed to an ad- 

 vanced stage. 



In the manufacture of the Japanese and Chinese rice wine (sake) 

 the maltose fermentation of the starch (in the rice grain) is brought about 

 by the Aspergillus oryzce as already stated. The process of beer and sake 

 manufacture may be compared as follows: 



BEER. 



SAKE. 



i. Material Used. 



Carefully selected barley is cleaned in 

 running water, then macerated in water 

 to induce germination. Rice, wheat and 

 other cereals may be added. Hops are 

 used. 



A good quality of rice is thoroughly 

 washed in cold water, then softened by a 

 steaming process. No hops used. 



2. Diastase Fermentation. Malting. 



During the germinating process a fer- 

 ment or enzyme (diastase) is liberated 

 which converts the starch into saccharine 

 compounds. The ferment is unorganized 

 (non-living) and is soluble in water. The 

 germinating and fermenting grain consti- 

 tutes the beer wort. 



The steamed rice is spread on mats and 

 inoculated with the spores and hyphae of 

 Aspergillus oryza. This fungus liberates 

 an enzyme (diastase) which converts the 

 starch into saccharine substances. The 

 enzyme produced by the fungus is soluble 

 in water. Fermentation takes place in" a 

 warm room. 



3. Alcoholic Fermentation. 



The beer wort (Bierwiirze) is now ready 

 to be acted upon by the yeast organisms 

 (Saccharomyces cerevisece) which enter from 

 the air or which may be added in pure 

 culture. The yeast organisms convert the 

 saccharine substances into alcohol and 

 carbonic acid gas (CO 2 ). 



The diastase and the yeast ferments are 

 both active during this process. 



The sake wort (moto) is prepared by mix- 

 ing the steamed rice and fungus (A . oryzoz) 

 in vats. Yeast cells (Saccharomyces of 

 sake) enter from the air and cause alcoholic 

 fermentation, converting the saccharine 

 substances into alcohol and carbonic acid 

 gas (C0 2 ). 



The diastase ferment (produced by A. 

 oryza) and the alcoholic ferment (Saccha- 

 romyces) are active during the entire 

 process. 



