FERMENTED DRINKS 89 



separated from the alcohol by distillation, producing a 

 liquor with a much higher percentage of alcohol, — the 

 distilled liquors, like rum, brandy, whisky, etc. 



In the making of wines the process is, in a way, simpler, 

 and reliance is usually placed upon the wild yeasts which 

 produce a spontaneous fermentation. The skin of the 

 grape becomes the lodging place of numerous micro- 

 organisms which collect there while the grape is growing. 

 These include molds and bacteria as well as yeasts, and 

 when the juice is squeezed from the grape it is certain to 

 contain some of this wild yeast. Fig. 37 shows some of 

 the wild yeast thus spontaneously inoculated into grape 

 juice. The juice is set aside and a spontaneous fermen- 

 tation begins. The fermentation is not very vigorous and 

 may require many weeks for its completion. 



So sure is the grape juice to contain yeasts that unless 

 some means of preventing their growth is adopted fer- 

 mentation cannot be avoided. Li making what is called 

 unfermented grape juice the yeasts are destroyed by heat. 

 The grape juice is heated to a temperature of about 170° 

 for a few minutes. This operation is usually performed 

 twice, after which the wine is bottled and sealed. The 

 process is really the same as that of preserving food by 

 canning, which will be described later, the only essential 

 difference being that the grape juice does not require boil- 

 ing for its preservation. It will be noticed from Fig. 37 

 that there are other organisms besides yeasts upon the 

 grape skin. These may have some effect upon the wine, 

 and various devices are used to get rid of them. 



Yeasts are also used in the manufacture of homemade 

 wines which are produced from juices of fruit such as grapes, 



