146 MANAGEMENT OF DAIRY PLANTS 



Example: State amount of steam used for pasteurizing a 

 definite amount of cream in a ripener when the circulating 

 water weighs 428 pounds at 50 F. (10 C.). Final temperature 

 of circulating water being 158 F. (70 C.), and amount of over- 

 flow being equal to 236 pounds. 



Answer : 



The amount, by weight, of circulating water overflowing by 

 being heated from 50 F. to 158 F. is 



428X1.02260 1.00026^ 



- = 9-35 pounds. 

 1.02260 



Amount of steam used for pasteurization is 



236 9.35 = 226.65 pounds. 



3. Difference in Amount of Steam Used for the Continuous or 

 Flash Method and the Holding Method of Pasteurization. By 

 the continuous method of pasteurization the milk or cream 

 is heated to a higher temperature, about 180 F., and the con- 

 densed steam is also discharged at a higher temperature, usually 

 at from 200 F. to 210 F. When pasteurizing by the hold- 

 ing method the cream is heated to about 145 F. and the 

 condensed steam is discharged at a temperature of about 

 150 to 1 60 F. This saving in heat by the latter method is 

 somewhat reduced, due to the fact that a certain amount of 

 circulating water has to be heated most often from a tempera- 

 ture of about 50 F. to about 150 F. The additional amount 

 of steam required for heating the circulating water is reduced 

 per pound of butter fat as the amount of milk or cream in the 

 vat is increased. Therefore when pasteurizing in the vat the 

 steam required for pasteurization per pound of butter fat is 

 greater when the vat is only half full of cream than when it is 

 full. The following examples illustrate fairly well the amount 

 of steam required for pasteurization under practical conditions. 



Example: 



i. Determine amount of steam required per pound of butter 

 fat when pasteurizing 2,000 pounds of 30 per cent cream from 

 60 F. to 185 F. by the continuous method of pasteurization, 



