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DAIRY BACTERIOLOGY 



serve to protect the milk from flies and dust after the bottle has 

 been opened and the milk partty used, and they allow of the 

 shaking up of the milk in order to distribute any cream which may 

 have separated. The best stopper of this description is that 

 shown in Fig. 59. It consists of a fairly stout porcelain stopper 

 which is held firm by being simply clamped against the under side 

 of the collar on the bottle neck ; it is easily removed when the 

 bottle is opened, and is therefore easy to clean ; the joint is made 

 by a paraffined paper ring which should constantly be renewed ; 



FIG. 58. Laval's Cleaning Separator. 



rubber rings are not so good, as they are not always free from 

 smell. (Another method which is largely used on grounds of 

 economy is to close the bottle by a paraffined cardboard disc which 

 fits tightly inside a groove in the neck of the bottle ; this method 

 is less satisfactory than those described above, for after the disc 

 has been removed and replaced, it easily becomes soaked through 

 with the milk, and the internal groove in the neck of the bottle 

 is objectionable on grounds of cleanliness. Translator.) 



Milk is often pasteurised', the better to overcome the difficulties 

 which beset the problem of keeping it good until it can be retailed. 

 For the reasons stated above, this should be accomplished by the 

 low temperature process or by short heating (flashing) to 70 to 



