UNITED STATES DEPARTMENT OF AGRICULTURE 



fill bulletin No. 342 mm 



.$\/p*^^L 



Contribution from the Bureau of Animal Industry 

 A. D. MELVIN, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



January 8, 1916 



THE PRESENT STATUS OF THE PASTEURIZATION 



OF MILK. 



By S. Henry Ayers. Bacteriologist, Dairy Division. 



CONTENTS. 



Page. 



Meaning of the term ' ■ pasteurization " 1 



Value of pasteurization 1 



Extent of pasteurization in the United States. 3 



Methods of pasteurization 4 



Advantages of low-temperature pasteuriza- 

 tion 5 



Temperature and methods most suitable for 



pasteurization 6 



Supervision of the process 7 



Handling pasteurized milk 8 



Cost of pasteurizing milk 9 



Bacteria which survive pasteurization 9 



Modern theories of pasteurization 13 



The necessity for pasteurization 15 



References to literature 16 



MEANING OF THE TERM " PASTEURIZATION." 



The term " pasteurization," as applied to milk, should mean a 

 process of heating to 145° F. and holding at that temperature for 30 

 minutes, but as applied under commercial conditions it is the process 

 of heating for a short or long period, as the different methods de- 

 mand, at temperatures usually between 140° and 185° F. The process 

 is followed by rapid cooling. The term originated from the experi- 

 ments of Louis Pasteur in France. From 1860 to 1864. in experiment- 

 ing on the " diseases " of wine, he found that heating for a few 

 moments at temperatures of from 122° to 140° F. was sufficient to pre- 

 vent abnormal fermentations and souring in the wine. A little later 

 he found that by a similar heating beer could be preserved from sour- 

 ing. The application of the process gave rise to the term " pasteuri- 

 zation." 



VALUE OF PASTEURIZATION. 



From a sanitary standpoint the value of pasteurization is of the 

 greatest importance when market milk is under consideration. The 



Note. — This bulletin will be of interest to health officers, medical men, scientific dairy- 

 men, and others who may be interested in the subject of pasteurization. 

 14089°— 16 



