Bacteria in Cheese. 185 



cheddared than in sweet curd cheese. When acidity is pro- 

 duced, these gassy fermentations ar^ checked, and in good 

 cheddar the body is so close and firm as not readily to per- 

 mit of gaseous changes. 



In Swiss cheese, which is essentially a sweet curd cheese, 

 these fermentations are very troublesome. Where large 

 holes are formed in abundance (blahen), the trouble reaches 

 its maximum. If the gas holes are very numerous and 



FIG. 34. Block Swiss cheese showing " gassy " fermentation. ' 



therefore small it is called a " nissler." Sometimes the 

 normal " eyes " are even wanting when it is said to be 

 it blind"ora"glasler." 



One method of procedure which is likely to cause trouble 

 in Swiss factories is often produced by the use of sour, 

 fermented whey in which to soak the natural rennets. 

 Freudenreich and Steinegger J have shown that a much more 

 uniform quality of cheese can be made with rennet extract 

 if it is prepared with a starter made from a pure lactic fer- 

 ment. 



The cause of the difficulty has long been charged to va- 



i Cent. f. Bakt. 1899, p. 14. 



