100 THE BOOK OF BUTTER 



enough to remain above 145° F. for 30 minutes. This 

 pasteurizes the milk in the final container and increases 

 the keeping qualities of the skim-milk." 



If the skimmed-milk is cooled by the creamery, it is 

 put into cans that are not thoroughly scalded and imme- 

 diately the pasteurized skimmed-milk is seeded by the 

 organisms that are already in the can. The skimmed- 

 mUk should be cooled by the farmer after he returns 

 home, for it will remain sweet much longer than if it is 

 not cooled. It should keep sweet at least twenty-four 

 hours. It is well to note the fact that the creamery can- 

 not afford to cool the skimmed-milk, that is returned to 

 the farmer. The patron is the person who profits most 

 by the pasteurization of the skimmed-milk, and he should 

 be willing to cool it in case he wishes to feed it 

 sweet. If he is not willing to cool it, he ought at 

 least not to complain about it. Dotterrer and Breed ^ 

 refer to the fact that the Pennsylvania law requires the 

 heating of dairy by-products to a temperature of at least 

 178° F.; Iowa, 185° F.; Minnesota, 180° F. ; while 

 Michigan requires 185° F. or 145° F. for thirty minutes. 

 According to Rosenau ^ the temperature necessary to 

 kill pathogenic bacteria is 140° F. (60° C.) for twenty 

 minutes. Russell and Hastings ^ say that 160° F. or above 

 for one minute is sufficient to destroy the virulence of 

 bovine tubercle cultures. These are the two reasons for 



' Dotterrer, W. D., and Breed, Robert S., The Pasteurization 

 of Dairy By-Produots, N. Y. State Agri. Exp. Sta., Bui. 412, 

 pp. 582-590, 1915. 



2 Rosenau, M. J., Pasteurization, Hygienic Lab., Bui. 41, 

 p. 698, 1908. 



' Russell, H. L., and Hastings, B. G., Effect of Short Periods 

 of Exposure to Heat on Tubercle BaoilK in Milk, Univ. of Wis. 

 Agri. Exp. Sta., Ann. Rpt., p. 192, 1904, 



