THE PASTEURIZATION OF MILK 



principle is made use of, and the cool water leav- 

 ing the heater is carried over to the cooler, so that 

 it helps to cool the hot milk flowing into it. 



In choosing a machine of this type, care should 

 be exercised in securing one which may be easily 

 cleaned, especially at the turns and joints. All 

 these should be smooth and readily accessible. 



It should be borne in mind that while a large 

 heating area with many pipes is an advantage in 

 securing an even heating with a low water tem- 

 perature, the difficulties of cleaning are also in- 

 creased. 



It is also readily seen that when powerful pumps 

 force the hot water rapidly through the heating 

 pipes, a relatively lower heating temperature may 

 be employed. 



An objection to the tubular form of heater lies 

 in the fact that the tubes in this system are nearly 

 'horizontal and parallel. There is thus but little 

 inclination or pitch to the tubes, and the milk flows 

 from them rather slowly when they are emptied at 

 the close of operations for the day. This objec- 

 tion has been overcome in some of the more re- 

 cently manufactured machines, by putting the 

 pipes at an incline and not parallel to each other. 

 64 



