Pasteurisation of Milk and Cream. 



33 



2. Where milk is exposed under conditions that would enable a pellicle or mem- 



brane to form on the surface the tubercle organism is able to resist the 

 action of heat at 140 deg. Fahr. for considerably longer periods of time. 



3. Efficient pasteurisation can be more readily accomplished in a closed recep- 



tacle such as is most frequently used in the commercial treatment of milk 

 than where the milk is heated in open bottles or open vats. 



4. It is recommended in order to thoroughly pasteurise milk so as to destroy 



any tubercle bacilli which it may contain, without in any way injuring its 

 creaming properties or consistency, to heat the same in closed pasteurisers 

 for a period of not less than 20 minutes at 140 deg. Fahr. 



Under these conditions one may be certain that disease bacteria such as the 

 tubercle bacillus will be destroyed without the milk or cream being injured 

 in any way. For over a year this new standard has been in constant use 

 in the (Wisconsin) University Creamery, and the results from a purely 

 practical point of view reported last year (1899) have been abundantly con- 

 firmed. 



The pasteurisation of milk for butter-making also formed 

 the subject of a series of experiments during the past year at 

 the Ontario Agricultural College. Vats of milk were 

 heated before separating to the following temperatures 

 — viz.: between 140 and 150 deg., 150 and 160 deg., 170 

 and 180 deg., 180 and 190 deg., and 190 and 200 deg.; 

 and the results were compared with vats of similar 

 milk heated to a temperature ranging between 90 deg. and 

 100 deg. before separating. In all the trials the milk was 

 thoroughly mixed in a large vat and then equally divided, 

 one-half being heated to a temperature varying from 90 

 to 100 deg., and the other half to temperatures ranging 

 between 140 and 200 deg. The principal results indicated 

 that milk heated to temperatures between 140 and 200 deg. 

 be c ore being separated showed that more fat remained in both 

 the skim milk and butter milk than in the case of milk 

 separated at 90 to 100 cleg. The separated cream from 

 the milk pasteurised at the higher temperatures was less in 

 bulk, but contained a higher percentage of fat, churnei in 

 less time, and produced slightly more butter. There was 

 more sediment or " mud " in the separator bowl after running 

 through the pasteurised milk than there was from the 

 unpasteurised milk. 



The creaming property of milk by the gravity process 

 decreased with an increased temperature before setting. The 

 whole milk averaged 4*08 per cent, fat, and the skim milk 

 contained 3-08 percent, fat when the whole milk was heated to 



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