394 MICROORGANISMS 



proteins are attacked by certain bacteria, several bad smelling 

 gases are produced and this process has long been known under 

 the name PUTREFACTION but, while the details of this process 

 are not well known, it is known that it does not differ essen- 

 tially from other processes of fermentation and it is often 

 called PROTEIN FERMENTATION. Numerous other kinds of 

 fermentation are knowji and all are named either after the 

 substance that is fermented or after one of the products that 

 result. 



447. Yeasts and the Production of Alcoholic Liquors. We 

 have said that all intoxicating liquors derive the alcohol they 

 contain from the process of alcoholic fermentation carried on 

 by yeasts. In the making of all the different kinds of liquors, 

 a sugary solution of some kind is always provided. This is 

 INOCULATED with a quantity of yeast and kept at a suitable 

 temperature until the fermentation has gone as far as desired, 

 or until the accumulating alcohol has killed the yeast and 

 stopped the process. In the case of wines, beer, and ale, 

 the mixture is next put into bottles or kegs and is ready for 

 use. In some of these undistilled liquors, the bottling is 

 done before fermentation has entirely ceased, and thus a con- 

 siderable quantity of carbon dioxide remains in the liquor. 

 This adds to the flavor of the liquor and is responsible for its 

 sparkling quality. The color and part of the flavor of wines 

 is derived from the fruit juices used in making them. In the 

 making of distilled liquors, such as whiskey, rum, and brandy 

 the process of fermentation is carried as far as possible and 

 then some of the water of the mixture is removed by the 

 process of distillation (see Art. 24). In making liquors from 

 cereals, such as corn, rye, and barley, the starch of the cereal 

 is first changed to sugar by the process described in Art. 424, 

 and then the sugar is fermented by yeasts. 



448. Yeasts and the Making of Bread. It is the carbon 

 dioxide which results from fermentation which is of use in 

 making bread. The flour which is used in making bread 

 contains some sugar and usually a little more sugar is added 



