THE PASTEURIZATION OF MILK 



size also tends toward the ease of cleaning, there 

 being no great amount of surface with which the 

 milk comes in contact. 



This very fact, however, that the heating sur- 

 face is small in area, is also a disadvantage, for 

 it renders it necessary to raise the temperature of 

 the heating medium to a point so high that it is 

 frequently very much in excess of that to which 

 it is the desire to heat the milk. The result is 

 that certain portions of the milk reach a tempera- 

 ture so high that a distinctly scorched taste is im- 

 parted to it. This taste persists in the entire 

 body of the treated milk, even though the average 

 temperature of the milk leaving the apparatus is 

 below 145. This is especially noticeable if the 

 flow of milk into the apparatus fluctuates. It can 

 be readily seen that with a very hot heating sur- 

 face, and at the same time a small amount of milk 

 passing through the machine due to a sudden stop- 

 page of flow, this milk would attain a high tem- 

 perature. 



This superheating of even a portion of the milk 

 tends to cause an interference with the normal 

 rising of the cream, after the milk is placed in 

 containers. The vigorous agitation of the hot milk 



46 



