348 MICROBIOLOGY OF MILK AND MILK PRODUCTS. 



quality of the product will not be impaired by the use of temperatures 

 approximating the boiling point. The cheese maker is much more 

 dependent on the original quality of the milk, since effective pasteuri- 

 zation so changes the milk as to effect profoundly the expulsion of the 

 whey from the curd and the development of flavor during the ripening 



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FIG. 81. The type of curd obtained from milk in which the acid-forming flora consists 

 largely of organisms of the Bact.coli aerogenes group. Many gas holes and few irregu- 

 lar-shaped, angular, mechanical holes due to imperfect "matting." (Original.) 



process. If harmful forms of microorganisms are present in the milk, 

 they will pass into the cheese and there produce their harmful effects. 

 Through the addition of pure lactic cultures to the milk the proportion of 

 desirable bacteria can be increased and a partial control of the fermen- 

 tation thus secured. 



