176 MANUAL OF MILK PRODUCTS 



in 1914. The process consists in pasteurizing milk by the 

 holder method at 145 F. for thirty minutes, then bottling, while 

 hot, in hot, steamed bottles. The bottles 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 cir- 

 culation 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 bottling 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 pas- 

 teurization in bottles. The results of these experiments are 

 being prepared for publication. While working 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, 

 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 twenty or 

 thirty minutes and to at least 160 F. for one 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 thirty 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 per- 

 centage of the bacteria that cause milk to sour (lactic-acid 

 bacteria) and only a small percentage of those that cause it to 



