PASTEURIZATION OF MILK 



125 



Section of thermos bottle. 

 (After Hoadley.) 



can gain entrance. This is done 

 usually by boiling fruits or vege- 

 tables, sometimes with sugar or 

 salt, and placing them immediately 

 in sterile jars and then sealing them 

 tightly. They may also be canned 

 by simply placing food uncooked 

 but clean in cans, closing the cans, 

 and then sterilizing by boiling for 

 a considerable period of time. The 

 United States Government, De- 

 partment of Agriculture, Farmers' 

 Bulletin No. 839 gives full direc- 

 tions for canning by this last method, called the cold-pack 

 process. Some vegetables such as peas, beans, and corn are 

 very difficult to can, probably because of spores of bacteria 



which are attached to them, and 

 it requires a longer heating to kill 

 the spores. Fruits, on the other 

 hand, are usually much easier to 

 sterilize. The main thing to bear 

 in mind is to have the jars as well 

 as the material that goes into 

 them, sterilized, that is, absolutely 

 free from all living matter. This 

 can be done best by long boiling. 

 Pasteurization of milk. Milk 

 is one of the favorite foods of 

 bacteria. It is also a very im- 

 portant food for children, and 

 since a baby's digestive system 

 is easily upset, we should pro- 



Pasteurizing apparatus, an arrange- 

 ment by which milk is conven- 

 iently heated to destroy disease 

 germs. The thermometer tells 

 the degree of heat used. 



