SKIMMILK AND BUTTERMILK 133 



keeping it sweet ; the other is to kill the tubercle bacilli 

 that may be found in it. 



To secure the greatest feeding value of skimmilk it 

 must be fed sweet. During the summer months skim- 

 milk as it is ordinarily returned from creameries keeps 

 sweet but a short time, a fact which has compelled many 

 a farmer to purchase a hand separator and separate the 

 milk at the farm. 



The danger of spreading tuberculosis among cattle and 

 swme through creamery skimmilk is so well established 

 now that several states have passed laws making pasteur- 

 ization of skimmilk compulsory. Indeed such laws have 

 existed in Denmark for many years. 



Either of the above purposes should be sufficient to 

 cause butter makers and creamery managers to feel it 

 their duty to pasteurize the skimmilk without being 

 driven to it by law. 



Where the skimmilk is returned hot from the cream- 

 ery, pasteurization has the additional advantage of steriliz- 

 ing the milk cans. 



Pasteurizing Temperature. The minimum tempera- 

 ture should be placed at 176° F, which makes it possible 

 to determine by means of Storch's test (see appendix) 

 whether the skimmilk has been pasteurized or not. 



This minimum limit is necessary to insure a thor- 

 ough destruction of bacteria. It is hardly necessary to 

 fix a maximum limit of temperature since it is difficult 

 to exceed 190° F, and little objection can be raised to 

 approaching this temperature. Indeed it is believed that 

 where thorough pasteurization is desired it is advisable 

 to keep the temperature close to 190° F. 



Methods of Pasteurizing. Pasteurization is accom- 



