528 MILK 



final package method than does the determination of the bacterial 

 counts." 



Pasteurization in bottles has then two advantages: 1, It min- 

 imizes the danger of reinfection after pasteurization; and 2, loss of 

 milk caused by evaporation and by adhesion to machinery is 

 avoided. Its disadvantages are the possible breakage due to im- 

 mersion of hot bottles in cold water and the expense of water- 

 tight caps. The last disadvantage does not obtain in Ayers and 

 Johnson's modification. 



It is usually stated that after pasteurization milk should be 

 cooled rapidly, because it is thought that there is considerable 

 bacterial multiplication during the period of cooling and that 

 rapid cooling aids in the destruction of bacteria. Ayers and 

 Johnson have shown that there is no greater increase in the num- 

 ber of bacteria if the process of cooling occupies as much as five 

 hours than if it is done in a shorter time. They explain this on 

 the basis of the influence of pasteurization temperature on bac- 

 teria. Those which survive are temporarily weakened and re- 

 quire some time to recover their natural vitality, but rapid cool- 

 ing does not increase the destructive effect of pasteurization. 



The most important advantage of pasteurization lies in the 

 destruction of pathogenic bacteria. In order to accomplish this 

 object pasteurization must be efficient. To make it universally 

 so, pasteurization plants should be under supervision of health 

 officers, who should provide for the following points: 



1. No milk should be used for pasteurization if it is derived 

 from a filthy dairy. Pasteurization cannot do away with dairy 

 inspection. As a tentative standard for admission of milk to 

 pasteurization it might be required that the dairy whose milk is 

 to be pasteurized should score at least 55 on the government 

 score card. 



2. Milk should be kept cool during transportation to prevent 

 excessive multiplication of bacteria. Health officers should test the 

 temperature of the milk upon its arrival at the pasteurization plant. 



3. The holding process should take the place of the flash 

 process. The flash process as usually practised, by heating milk 

 to 160 F. for a fraction of a minute, is not to be depended upon 

 to render the milk safe. It is essential that dealers as well as 

 consumers should understand that pasteurized milk 'means milk 

 heated at sufficiently high temperature to surely destroy patho- 

 genic bacteria. A clear definition of the term "pasteurization" 

 should be decided upon by boards of health. It is safe to de- 

 fine pasteurization as the process of heating milk to 145 F. and 

 holding it at this temperature for thirty minutes, or heating to 

 160 F. for five minutes. 



