PRESENT STATUS OF PASTEURIZATION OF MILK. 5 



for the added expense of caps. It is now possible to pasteurize milk 

 in this manner without using water-tight caps. This is accomplished 

 by the aid of devices which fit over the tops and necks of the bottles, 

 thereby protecting the ordinary paper caps from the water which is 

 sprayed on the bottles for the purpose of heating or cooling. This 

 method of protecting the tops permits the use of the ordinary caps 

 and removes the possible danger of polluted water infecting the milk. 



Another method of pasteurization, or, rather, a modification of the 

 present holder process, is that of bottling hot pasteurized milk. 

 Work on this process was begun in 1911, and the process was first 

 suggested by the author (4) in 1912; further work on this subject 

 may be found in an article published in 1914 (5). The process con- 

 sists in pasteurizing milk by the holder method at 145° F. for 30 

 minutes, then bottling, while hot, in hot, steamed bottles. The bot- 

 tles are steamed for two minutes immediately before filling. After 

 filling with hot milk and capping with ordinary caps the bottles 

 may be cooled at once by any of the systems in which the caps are 

 protected and the bottles sprayed with water, or the forced cold-air 

 circulation may be used. 



The use of forced-air circulation for cooling milk is entirely new, 

 and while only suggested in the paper describing the process of bot- 

 tling hot pasteurized milk, recent experiments with it for cooling 

 indicate that it is practicable. We have obtained bacteriological 

 results which show that this process is always as good as', and often 

 superior to, the process of pasteurization in bottles. The results of 

 these experiments are being prepared for publication. While work- 

 ing on this process of bottling milk hot it was found that a similar 

 process was patented several years ago. It was described by De 

 Schweinitz (6), and recently two other patents on the process have 

 appeared. 



ADVANTAGES OF LOW-TEMPERATURE PASTEURIZATION. 



In general the trend of pasteurization is toward the holder process, 

 and with this tendency the use of lower temperatures is becoming 

 more common. As a general rule, when the holder process is used 

 milk is heated to 145° F. for 20 or 30 minutes and to at least 160° F. 

 for 1 minute when the flash process is used. From bacteriological, 

 chemical, and economical standpoints it is highly desirable that milk 

 be pasteurized at low temperatures. 



From a bacteriological standpoint, pasteurization at 145° F. for 30 

 minutes gives assurance, so far as we know, of a complete destruction 

 of disease-producing bacteria, and at the same time leaves in the 

 pasteurized milk the maximum percentage of the bacteria that cause 

 milk to sour (lactic-acid bacteria) and only a small percentage of 



