174 ILLINOIS DAIRYMEN'S ASSOCIATION. 



Aeraton. This is very essential. Pasteurize the cream with 

 as little curdling as possible. Avoid exposing large quantities of 

 cream to a small heating surface. An efficient cooler in opera- 

 tion with the pasteurizer is needed. The cooler should be of 

 sufficient cooling capacity to allow the pasteurizer to be operated 

 at its full capacity. 



The cream should be thoroughly mixed before it is allowed 

 to flow into the pasteurizer. Observe directions pertaining to the 

 starting of the machine. The first cream in the machine should 

 not be heated to regular pasteurizing temperature, but start the 

 flow of cream into the pasteurizer in time to force the first cream 

 into the cooler at a temperature of 140 degrees F ,and rapidly 

 increase the temperature to 170 to 185 F. 



It is apparent that the curdling of sour hand-separator cream 

 is greater as the percent of butter fat decreases and acidity in- 

 creases. Also that the curdling of the first cream entering the 

 pasteurizer is greater if it is heated to 170 or 180 degdees F, in- 

 stead of 140, before it leaves the machine. 



Pasteurized sour cream should be cooled to a lower temper- 

 ature for churning than the same grade of unpastuerized cream. 

 It should be held at low temperature for some time in order to 

 give results desired. In the factories where the cream warms 

 again after it has once cooled, it should be cooled so that at churn- 

 ing time the temperature will be 48 degrees F. 



The excessive loss of butter fat in buttermilk from pasteur- 

 ized sour cream can, by the above method, be reduced to the mini- 

 mum. The pasteurization of sour cream containing less than 30 

 or 32 per cent of butter fat will curdle part of the casein in the 

 cream. The curdled particles of casein will contain a certain 

 amount of fat which can not be incorporated with the butter ob- 

 tained by churning; hence a greater loss. Results of several 

 tests show that the curdled casein will contain in the neighbor- 

 hood of 20 per cent of fat and in a few cases as high as 30 per 

 cent has been found. 



The following table shows the acidity of the cream and the 



