FERMENTATION AND ALCOHOL 43 



the term fermentation is used alone. An adjective signifying the 

 special form of fermentation is used to indicate any other form than 

 the alcoholic. Thus there is acetous or vinegar fermentation, and 

 putrefactive fermentation. 



52. Bread making. By the growth of yeast plants in 

 bread dough some of the sugar in the flour is changed 

 to carbonic acid gas and alcohol. The gas bubbles up 

 through the dough, making it porous and light. When 

 the bread is baked, alcohol is driven off and the yeast 

 germs are killed by the heat. They are eaten with the 

 bread, for they are perfectly wholesome. When germs 

 of vinegar or other acid fermentations enter the bread 

 and grow, the bread sours. These germs grow more 

 slowly than yeast, and usually do not have time to de- 

 velop. But if the bread is a long time in rising, they 

 may grow and make the bread sour. 



53. Fermented drinks. Man uses the same process to 

 produce drinks, which are erroneously supposed by many to 

 act as a beneficial food, quenching thirst and giving strength 

 to the body and power and joy to the mind. There are 

 three classes of such drinks, all containing alcohol as an 

 essential part. 



54. Malt liquors. The commonest form is what is 

 known as malt liquors. Barley and other grain are mois- 

 tened and permitted to sprout until the new stalk is about 

 one half inch in length. This changes much of the starch 

 of the grain to sugar. The sugar is dissolved out by boil- 

 ing the grain along with hops and various other flavoring 

 substances. Then yeast is added and alcoholic fermen- 

 tation occurs. The result is beer. It contains from one 

 to ten per cent of alcohol. Much of the flavoring which 

 is often added to it is not only injurious, but actually 

 poisonous. 



