PRESERVATION OF MILK AND ITS TREATMENT 93 



75 C. 1 Low temperature pasteurisation (holder process) is best 

 carried out in closed bottles completely immersed in water, as is 

 done in the Danish beer pasteurising apparatus ; treated in this 

 way, the milk does not lose its carbon dioxide, while the bottles 

 are pasteurised as well. As the milk does not give off its loosely 

 combined carbon dioxide at the temperatures employed, no 

 appreciable pressure is developed in the bottles. If the milk is 

 pasteurised in bulk and then bottled, the bottles must be sterilised 

 beforehand. Ayers and Johnson 2 propose to bottle the milk 

 warm in a warm room, and to let it stand for ten minutes before 

 cooling ; as the temperature will only fall about 5 C. at the 

 most during this period, the organisms which have gained access 

 to the milk in the bottle during 

 filling will generally be destroyed, 

 and the milk will keep as well as 

 if it had been pasteurised in the 

 bottle. 



Milk which has been pasteur- 

 ised rationally according to the 

 methods suggested above still 

 gives a positive Starch's reaction, 

 and is consequently not recognised 

 as pasteurised according to the 

 Danish law, the definition being 

 reserved for the milk which has 

 been strongly heated so as to give 

 a negative test. In any legisla- 

 tion on this subject, it is highly 

 desirable that distinction should 

 be made between high and low 

 temperature pasteurised milk. In the case of skim milk or 

 buttermilk, however, the Storch test may quite well be employed 

 as the criterion. Milk which is to be retailed to the public should 

 either be raw, in which case it should be derived from herds kept 

 under strict veterinary supervision, or it should be pasteurised by 

 the low temperature process ; in addition to control by inspec- 

 tion of the recording thermometer charts in the dairy, the 



1 Tholstrup Pedersen proposes simply to slime centrifuge the milk- after 

 it has been warmed to 70 C. This proposal is worthy of consideration, 

 especially as Prescott and Breed ("Journal of Infectious Diseases," 1910, 

 vol. 7) have shown that the white blood corpuscles, which carry much dirt 

 and many bacteria with them, are more readily separated from warm milk. 

 Unfortunately the cream line is affected by this treatment, as was shown in 

 the trials made with the first Laval cleaning centrifuge (" Deutsche milch- 

 wirtschaftliche Zeitung," 1912, No. 12). Milk is, therefore, now cleaned 

 by centrifuging at 10 to 12 C. instead of at 70 C. 



2 U.S. Dept. of Agric., Bureau of Animal Industry, Bull. 240 1915. 



FIG. 59. Hygienic Stopper. 



