MARKET MILK 



173 



for thirty minutes, but as applied under commercial conditions 

 it is the process of heating for a short or long period, as the 

 different methods demand, at temperatures usually between 

 140 and 185 F. The process is followed by rapid cooling. 



Pasteurization, when first practiced by milk-dealers in this 

 country, was carried on secretly, and, except as a means of 

 preserving the milk, was regarded by them as a process of no 

 value. As the practice became more general, the subject of 

 pasteurization was studied, and its value as a means of destroy- 

 ing disease-producing bacteria was recognized. In conse- 

 quence of the recognition of the merits of the process there has 

 been during the last ten years a rapid increase in the quantity 

 of milk pasteurized, particularly in the larger cities. 



The general tendency in this country to-day is toward the 

 pasteurization of all market milk, with the exception of cer- 

 tified and inspected milk from tuberculin-tested herds. Some 

 idea of the extent of pasteurization may be gained from the 

 following table. The figures 1 were supplied by the milk-in- 

 vestigations section of the Dairy Division and were obtained 

 from replies to circular letters sent to health officers. 



EXTENT OF PASTEURIZATION OF MILK IN CITIES IN THE UNITED STATES 



1 These figures were obtained through the kindness of Mr. Ernest 

 Kelly and Mr. L. B. Cook. 



