BOILED MILK. 163 



increased in recent years. Of course, a remedy for this would 

 be to use it fresh, but this would take away the chief advan- 

 tage of sterilization, viz., its furnishing a kind of milk which 

 will keep. 



Boiled Milk. A practical method of nearly sterilizing milk 

 by the simple process of boiling is very widely adopted. 

 Boiling milk does not sterilize it and the milk cannot be pre- 

 served indefinitely, but it does destroy most of the bacteria. 

 The simplicity of the process makes it the most convenient of 

 all methods of treating the milk in ordinary households, and 

 for this reason it has been used very widely. It has most of 

 the disadvantages of sterilizing, but has the one very great 

 advantage of being convenient of application. It is used far 

 more widely than any Other method of treating milk and the 

 ordinary households in the large cities, especially among the 

 poor people, adopt the plan of boiling milk very extensively, 

 doing it, however, chiefly to keep it from souring rather than 

 for the purpose of rendering it more wholesome. 



Pasteurization. The disadvantages associated with steril- 

 ization have created a dissatisfaction with this method and 

 have led to a different treatment of milk which, though theo- 

 retically less satisfactory, proves to be practically more useful. 

 This treatment, originally devised by Pasteur for the treat- 

 ment of wine, consists in heating the milk to a temperature 

 of 140-175 F., and then rapidly cooling. In choosing the 

 temperature two facts are considered : 



1. It is desired to use a temperature which produces a 

 minimum change in the chemical and physical nature of the 

 milk, and does not give the taste of boiled milk. The highest 

 temperature to which the milk can be subjected without 

 acquiring these tastes is about 155, although if the heating 

 lasts only a very short time a higher temperature produces no 

 noticeable effect. 



2. It is desired to use a temperature which will destroy 

 most of the bacteria. Pasteurization does not destroy all the 



