CHAPTER XV 

 THE RELATION OF BACTERIA TO DAIRY PRODUCTS 



The presence of bacteria in dairy products is of great im- 

 portance for the following reasons : 



First. They are responsible for most of the difficulties met 

 with in the handling of milk and the products manufactured 

 therefrom. 



Second. The making of dairy products is dependent on 

 their action, and 



Third. The presence or absence of certain types of bacteria 

 determines the wholesomeness of dairy products for the con- 

 sumer. 



It may be truthfully said that the dairy industry rests on 

 the science of bacteriology, and that nearly all the methods 

 employed in the production and handling of these products 

 are based on bacteriological principles. Dairy products always 

 contain bacteria, and the success of the operator depends on 

 his ability to control their activities. 



KELATION OF BACTERIA TO MILK 



Sources of bacterial contamination of milk 



Interior of udder. 



When milk is secreted in the udder, it is free from bacteria, 

 but as soon as it flows into the milk ducts, it comes into con- 

 tact with the organisms which always exist there. If the cow 

 is healthy and the udder free from disease, the number of 



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