142 GUIDE TO DAIRYING IN SOUTH AFRICA 



The advantages of cooling are that the growth 

 of germ life is checked, and the exposure to the 

 air benefits the milk by getting rid of gases, bad 

 flavours, and animal heat and odours, at the same 

 time absorbing oxygen and light with their health- 

 giving properties. 



A study was made of bacteria in milk at every 

 hour during a period of forty-eight hours. Some 

 of the milk had been aired and cooled, the other 

 had not. The temperature of the room was 93 F., 

 and the milk was cooled down to 54 F., as that 

 was the temperature of the water used. The re- 

 sults showed as much change in the uncooled 

 milk in six hours as occurred in the cooled and 

 aired milk after twenty-four hours. 



PROGENY OF A SINGLE GERM 

 



/\ 



IN /TWELVE \HOURS 



/ \ 



IN MILK / \ IN MILK 



ALLOWED TO COOL/ NATURALLY RUN^OVER COOLER 



Showing the result of cooling milk by the 

 aerator or milk cooler. 



