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THE BOOK OF BUTTER 



36. Effect of stirring milk during cooling in tanks. 

 According to Ross and Mclnerney, 1 " The cooling pro- 

 cess, in order to be thorough, requires more than setting 

 the can of milk in a tank of ice water ; the milk must be 

 stirred frequently. If the milk is not stirred, that which 

 is near the walls of the can will become cold, while that 

 in the center of the can will, for a 

 long time, maintain a high temper- 

 ature favorable to the growth of 

 bacteria. Results showing the rate 

 of cooling when milk was and was 

 not stirred during the cooling pro- 

 cess are given in Table XI. In each 

 experiment in Table XI can 1 was 

 stirred at intervals of five minutes, 

 and the temperature recorded ; can 2 

 was stirred at intervals of ten min- 

 utes, and the temperature recorded ; 

 can 3 was not stirred at all, but the 

 temperature of the milk in the center 

 FIG. 12. End view of o f the can was recorded at intervals 

 The water^pace^nder f ten minutes ; can 4 was stirred 

 the can aids in rapid continuously, and the temperature 

 recorded at intervals of ten minutes. 

 "In each experiment, with the exception of one, recorded 

 in Table XI the milk in can 4, which was stirred con- 

 tinuously, registered the lowest temperature at the end 

 of an hour ; while the milk in cans 1 and 2, which was 

 stirred every five minutes and every ten minutes, respec- 

 tively, registered about the same final temperature but 

 not so low as that obtained in can 4. The milk in can 3, 



1 Ross, H. E., and Mclnerney, T. J., Cooling Milk, Cornell 

 Beading Course Lesson No. 102, 1915. 



