CREAMERY BUTTER MAKING 225 



To keep the skim-milk in good feeding condition it 

 must be pasteurized at the creamery. The cheapest and 

 most common means by which this is done is to heat_ 

 it with a heater like that shown in Fig. 68. This heater 

 utilizes the exhaust steam from the engine and heats 

 the skim-milk to temperatures ranging from 170 to 

 200 F. The skim-milk enters at one end of the 

 heater while the steam (either live or exhaust) enters 

 through the top near the point at which the^ skim-milk 

 enters. The steam thus comes in direct contact with the 

 skim-milk and condenses, heating it to the above tempera- 

 ture. One end of the pasteurizer is removable so as to 

 permit thorough cleaning. 



Objections have frequently been raised against this 

 method of pasteurizing because of the small quantity of 

 cylinder oil contained in the "exhaust steam. Where judg- 

 ment is used in oiling cylinders no trouble need be 

 anticipated from this source as the oil can be detected only 

 with difficulty. 



Extensive inquiry into the matter of pasteurizing skim- 

 milk has developed the fact that the patrons and the 

 calves must be educated to the change from unpasteurized. 

 to pasteurized skim-milk, and where this has been done 

 pasteurization has given the best of satisfaction indeed 

 the patrons would refuse to accept the skim-milk unpas- 

 teurized. Calves will object somewhat at first to a change 

 from unpasteurized to pasteurized skim-milk (especially 

 if the latter is fed at a temperature of 150 F.) but they 

 will soon begin to like it. 



A difficulty that has always been experienced in pasteur- 

 izing skim-milk is the foam that results from the heating. 

 Various so-called "foam killers" have been placed upon 



