PASTEURIZATION I47 



the condensed steam leaving the pasteurizer at 212° F., 900 

 B. T. U. of heat being obtained for each pound of steam used. 



2. Determine amount of steam required per pound of butter 

 fat when pasteurizing same cream in a vat, heating it to 145° F., 

 the condensed steam leaving at a temperature of 155° F., 500 

 pounds of circulating water being used, initial temperature of 

 this water being 50° F. and final temperature 160° F. 



3. Determine amount of steam required per pound of butter 

 fat when 1,000 pounds of 30 per cent cream are pasteurized 

 under the same conditions as specified in 2. 



Answer : 



, 2000 X 0.84 X 125 , , 



(.1) = 2^z.^Ti pounds of steam 



900 



'-^-^ = 0.389 pound of steam per pound of butter fat. 



2,000 X 0.30 



, , 2,000X0.84X85+ SooX no ^ ^ , , 



(2 j — - — : ^ — = 206.69 pounds of steam. 



900 + (212-155) 



:^--^ — = 0.344 pound of steam per pound butter fat. 



2,000 X 0.30 



,, 1,000X0.84X85+500X110 „ J r , 



(3) 1 — — r = 132.08 pounds of steam. 



900+ (212—155) 



■ = 0.440 pound of steam per pound of butter fat. 



1,000 X 0.30 



n. Cost of Cooling. — The cost of cooling depends primarily 

 on the amount of water required to remove the quantity of 

 heat taken up by the milk or cream during the process of pas- 

 teurization. A small part of this heat, however, is removed 

 by evaporation. This latter factor is of greater importance 

 when using an open cooler, such as a tubular, while of less signif- 

 icance when cooling in a cream ripener. 



The amount of water required for doing a certain amount of 

 cooling decreases in proportion to the number of heat units 

 taken up by each pound of water. Therefore the greatest 

 cooling efficiency is obtained when the difference is the greatest 

 between the temperature of the cooling water as it enters the 



