SOURCES OF DANCER IX MILK 



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This process, called after its discoverer pasteurization, 

 consists in heating milk for twenty minutes al a tempera- 

 ture of 60° C, or to a higher degree for a Bhortei time, and 

 then cooling it rapidly. This procedure kills nearly 

 all the bacteria in the milk and does not change the taste 

 or make it hard to digest. Milk is not rendered abso- 

 lutely sterile, but it is a much safer food, especially for 

 infants. At best pasteurization is only a corrective or 

 precautionary measure, and we should demand that milk 

 be kept clean and thus free 

 from bacteria. 



Most raw milk products have 

 their own forms of bacteria, 

 but most of these forms are 

 helpful. The flavor of June 

 butter is imparted by a bac- 

 terium different from the one 

 in January butter. So with 

 cheese, each brand or flavor 

 receives its taste through the 

 action of a special bacterium. 



At every step in the use and manufacture of milk, it is 

 necessary to know the conditions under which the helpful 

 bacteria work best, and how to keep out the harmful on 



247. Sources of Danger in Milk. — The cow herself may 

 be unhealthy and her disease transmitted through the 

 milk. Of the several diseases which this animal may 

 give, tuberculosis is the most common. Children are 

 more liable than adults to take the disease in this way. 

 There is no necessity to be in doubt about a cow's being 

 infected with tuberculosis, for in 18 l J0 Koch discovered 

 the tuberculin test, which enables the dairyman to detect 

 the disease. This test is now commonly applied and in 

 some cities owners of herds which have been tested and 



Figure 370. — Dirty Milk. 



