Relation of Bacteria to Cheese. 77 



When the milk is clean and a pure-culture starter is 

 used the cheese is generally of good quality. If the milk 

 is dirty, because of careless methods on the farm, a large 

 number of gas-forming bacteria will be present. These 

 grow in the curd together with the lactic acid bacteria, 

 causing the curd to be filled with holes due to the impris- 

 oned gas, and greatly injuring the flavor of the cheese. 

 The greatest trouble with which the cheese maker has to 

 contend is gassy milk. Milk of this nature can be de- 

 tected by the use of the Wisconsin curd test (p. 63). 



Other kinds of bacteria than the gas-forming types 

 may also injure the cheese. If the acid-forming bacteria 

 do not grow quickly in the milk, putrefactive organisms 

 may develop and cause offensive odors. In case of some 

 of the foreign types, the cheese may change from a firm 

 to a soft, slimy mass which has a most offensive odor and 

 bitter taste. The putrefactive bacteria can not develop 

 in a normal cheese because of its acid reaction. Chro- 

 mogenic bacteria may grow in the milk and cheese and 

 produce colored spots in the cheese. A trouble met with 

 in Canada and New York is called the ' ' rusty spot. ' ' It 

 does not injure the taste of the product, but causes it to 

 have a strange and unappetizing appearance and of 

 course lowers its commercial value. 



Foreign types of cheese. There are on the American 

 markets many types of cheese that have been imported 

 from the countries to which they are peculiar. Among 

 the most important of these are the Swiss cheese or Em- 

 menthaler, made in Switzerland, Roquefort from France, 

 Gorgonzola from Italy, Stilton from England, Lim- 

 burger from Germany, and Camembert and Brie from 

 France. Because of the high price that these cheese 



