PRODUCTION, COMPOSITION AND CHARACTERISTICS 25 



6,128,000. The effect of temperature upon the growth 

 of bacteria is shown graphically in the cut. 



But even frost does not kill the bacteria. If milk 

 which has been kept sweet or at the desired degree of 

 sourness by cooling is allowed to get warm again, the 

 bacteria which have been kept dormant will get a fresh 

 start. For this reason milk and cream for city supply 

 should not only be cooled strongly, but must be kept 

 thoroughly chilled up to the time they are used, which 

 means that they should be delivered cool to the con- 

 sumer, and kept on ice in the house, never being allowed 

 to warm up until used. 



Disinfectants. — Antiseptics, such as benzoate of soda, 

 formalin, boracic acid, etc., are not permissible in 

 milk, but disinfectants such as soda, lime, washing 

 powders, etc., should be freely used in cleaning uten- 

 sils, bottles, floors and walls where milk is handled, 

 so as to prevent as far as possible 

 any infection. 



PASTEURIZATION 



Pasteurization depends upon the 

 fact that almost all bacteria, and 

 especially the disease-producing spe- 

 cies, are checked in their growth and 

 made harmless, if not totally de- 

 stroyed, by instantaneous exposure t • t^ . 

 . J. . r i^7ro 17 Louis Pasteur, 



to a temperature of 175 1^., or a French scientist and 



more or less prolonged exposure to originator of the proc- 

 a lower temperature, for instance ess of pasteurization 

 for 20 minutes to 157° or 30 minutes to 145°. These 

 lower temperatures are recommended in the case of new 

 milk to be consumed as such, in order not to change its 



