CHAPTER XI 



Methods of Testing the Sanitary Condition oi 



Milk 



In addition to the compounds contained in normal 

 milk (see Chapter I.), milk, as ordinarily produced 

 and handled, contains other constituents, such as living 

 organisms (especially bacteria), enzyms, and often 

 other products due to abnormal physiological processes 

 in the udder. These constituents affect the value of 

 milk as food and as material for the preparation of 

 dairy products, such as cream, butter, cheese, etc. The 

 presence of micro-organisms, chiefly bacteria, and of 

 enzyms brings about biochemical or fermentation 

 changes in the normal constituents of milk, which 

 affect its healthfulness and keeping quality. Undesir- 

 able ferment-producing constituents and products of 

 fermentation have their origin in dirt and disease. It 

 is important, therefore, to be able, as far as possible, 

 to detect the presence of such undesirable constituents 

 in milk. The method chiefly relied upon for determin- 

 ing the condition of milk in relation to biochemical 

 factors has been by means of thorough bacteriological 

 examination, which is practicable only in the hands 

 of a specialist furnished with adequate equipment. 

 There are, however, other methods for ascertaining 

 the sanitary condition of milk which are available in 

 the hands of any careful worker and which afford 

 most helpful suggestions in regard to the value of 



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