PASTEURIZATION 213 



quantity of milk to be heated to a definite temperature 

 for a definite time (Russell). They must be easy to control, 

 the milk must be heated uniformly throughout, the appar- 

 atus must be simple in construction, easily cleaned, eco- 

 nomical in use, and arranged to safeguard against re-infec- 

 tion of the milk. Further, an efficient pasteurizer must not 

 heat any part of the milk appreciably higher than the tem- 

 perature desired. Finally, provision must be made for 

 rapid cooling. 



Given an apparatus of proper construction, more de- 

 pends upon the intelligence and care with which it is run 

 than upon the machine. No pasteurizer is automatic, no 

 pasteurizer is fool-proof. For instance, I have found milk 

 pasteurized in a standard machine containing many 

 more bacteria after the process than before. This was not 

 the fault of the machine, but due to negligence and unclean- 

 liness. It is better to depend upon mechanical thermo- 

 regulation than to attempt to regulate the degree of heat 

 to which the milk is subjected by hand. Pasteurizers 

 should all be provided with automatic thermometers which 

 record upon a revolving dial just what takes place. This 

 automatic instrument should be under the lock and seal of 

 the health officer. 



The best way to pasteurize milk is in the final container. 

 This has the advantage of eliminating the possibility of 

 re-infection. For a long time it was said that the pasteuriza- 

 tion of milk in the bottle was not a commercial possibility. 

 The difficulties, however, have been overcome by brewers, 

 who pasteurize beer in the bottles, and recently a progres- 

 sive dairyman of Boston has introduced a method of pas- 

 teurizing milk in bottles which is entirely satisfactory 

 from every standpoint. The bottles are stoppered with a 

 crown-cork and seal and are then immersed entirely in a 

 water bath, which is gradually heated until the temperature 

 of the milk within the bottles registers 148 F. This tem- 

 perature is maintained for thirty minutes, when the water 



