150 MANAGEMENT OF DAIRY PLANTS 



2. Cost of Pasteurization by Vat Method. — Taking for granted 

 that the vat used for pasteurization is of proper size, the amount 

 of steam required per pound of butter fat when pasteurizing a 

 30 per cent cream has been estimated at 0.344 pound. The 

 value of this being equal to 



0.344 X 1550 



—^-^ 2^ = 0.017 cent. 



5.5 X 2,000 



The total expenses may be summarized as follows: 



Cost of steam 0.017 cent 



Cost of cooling 0.021 " 



Cost of labor and equipment 0.040 " 



Total 0.078 " 



Bowen ' estimates the cost of pasteurizing one gallon of milk 

 at 0.313 cent and one gallon of cream at 0.634 cent. The 

 same investigator found that it requires approximately 17 per 

 cent more heat for flash pasteurization than for vat pasteuriza- 

 tion. 



It is possible to reduce the expenses of pasteurization slightly 

 by utilizing exhaust steam instead of live steam as has been 

 considered in the above. 



B. THE ECONOMIC EFFICIENCY OF PASTEURIZING 

 MACHINERY 



The economic efficiency of pasteurizing machinery depends 

 on the amount of heat that in a definite time wiU be transmitted 

 to milk or cream in the heating chamber from steam or water 

 in the surrounding chamber, known as the steam chamber. 

 The amount of heat thus transmitted depends on: First, size 

 of heating surface; second, thickness of the heating wall; third, 

 difference in temperature on the two sides of heating wall, and 

 fourth, thermal conductivity of the metal from which the 

 heating wall is constructed. 



' Bui. 85, U. S. Dept. of Agriculture, 1914. 



