152 MODERN DAIRY PRACTICE. 



ventor has patented in Germany, lies in the peculiar 

 method of closing the bottles. 



Scherff s milk will keep beyond question; both bacteria 

 and their spores are killed by this treatment. But even 

 by the application of this method the milk undergoes all 

 kinds of changes, as is natural at such a high temperature, 

 so that its usefulness is greatly impaired. The milk 

 assumes a cooked taste, which often approaches that of 

 burnt milk: and the color is often brownish, showing 

 that a caramel formation has taken place. Munk even 

 found that Scherff's milk had to be mixed with four 

 times the customary quantity of rennet to effect a coagu- 

 lation, and that this process took place more slowly than 

 usual in spite of this liberal addition of rennet. 



The other method of sterilizing milk by heating is to 

 boil it at ordinary pressure. Experiments were made 

 in sterilizing milk by heating to 212 F. for two hours, 

 but this method proved unsatisfactory, as no reliable 

 sterilization was obtained. It has been found that spores 

 of several bacteria will survive this process. The spores of 

 the hay bacillus, which, as before mentioned, is often found 

 in milk, are not killed by such a heating continued even 

 for six hours. The spores of the butyric-acid bacillus are 

 so tenacious of life that they survive boiling from one to 

 two hours. The same is true for Duclaux's Tyrothrix 

 tennis. 



This temperature having proved insufficient, experi- 

 ments were made by heating the milk to a higher degree. 

 Pasteur found that a single heating to 225-227 F. is ordi- 

 narily sufficient to sterilize the milk. Other investigators 

 again state that it is necessary to heat the milk 230-239 F. 

 to make certain of complete sterilization. Other difficul- 



