PASTEURIZATION 155 



efficiency than washing powder, but this should not be used 

 unless necessary, as it has a dissolving effect on the tin. The 

 following are the most significant causes for milk burning on 

 to the heating surface. 



A. Too Thin Metal. As the copper wall becomes extremely 

 thin the heat is conducted so readily through the wall that the 

 heating surface becomes too hot. The albumin when striking 

 this surface is coagulated and burns on. The increase in the 

 thickness of the heating wall will represent a comparatively 

 slight decrease in efficiency. This decrease, however, is in- 

 significant as compared to that caused by burned-on milk and 

 as copper is so efficient as a thermal conductor it is advisable 

 to have a copper wall of not less than one-twentieth of an inch 

 in thickness. Copper of such thickness will not cause the milk 

 to burn on readily and the pasteurizer, furthermore, becomes 

 of sufficient durability. 



B. Too High Heat in Steam Chamber. The heat in the 

 steam chamber should not exceed 214 F. The higher the heat 

 the greater the danger of burning on. The amount of heat in 

 the steam chamber of pasteurizer (Fig. 28) is controlled by 

 steam trap A. Through this trap all water condensed in the 

 pasteurizer escapes. The higher this water column extends 

 above the bottom of the pasteurizer the greater the steam pres- 

 sure and temperature in the steam chamber. Steam should 

 never be allowed to escape through this trap, as this will repre- 

 sent a loss of heat and indicate that the pasteurizer is operated 

 above its capacity. 



C. Too High Pasteurizing Temperature. It is natural 

 that the heating surface has to be kept at a much higher degree 

 of heat when the high pasteurizing temperatures are employed, 

 thus causing more of the milk to burn on. It is often noticeable 

 that a ring of burned-on milk is formed around on the upper 

 part of the heating surface where the milk has reached its 

 highest temperature. 



D. Too Hot Steam Coming in Contact with the .Warm 

 Milk. The steam when entering the pasteurizer, if of high 

 pressure, is considerably above 214 F. and it is most important 



