98 SKIMMING EFFICIENCY OF THE SEPARATOR 



The skim milk can be pasteurized more economically sepa- 

 rately by the use of exhaust steam. In order to accomplish ex- 

 haustive skimming of cold milk heated to the desired temper- 

 ature for separation, the milk must be held at that temperature 

 for a reasonable length of time so as to give the fat globules a 

 chance to warm and expand and thereby to regain their buoyancy. 



In some factories the milk is heated without the use of a 

 special heater, but by turning steam direct into the milk. 

 Experience has shown this to be a very undesirable practice. 

 At best, much of the steam used condenses in the milk, dilut- 

 ing the milk and the skim milk. Then, again, the steam is 

 often associated with impurities, such as cylinder oil from the 

 engine, boiler compounds used in the boiler, scales from the 

 inside of the steam pipes, etc. The turning of steam direct 

 into the milk has also been found to be injurious to the quality 

 of the finished product causing both the cream and the butter 

 to take on an oily flavor. 



Effect of Position of Cream or Skim Milk Screw on the 

 Skimming Efficiency of the Separator. As already explained, 

 the purpose of the cream screw, or skim milk screw, is to reg- 

 ulate the ratio of cream to skim milk and to control the rich- 

 ness of the cream. Most makes of separators permit of a rather 

 wide range of fat content in cream, without sacrificing their 

 skimming efficiency. Some machines, however, when they are 

 so adjusted as to produce cream testing below 18 per cent fat 

 or above 50 per cent fat, skim less completely. In the case of 

 some machines, especially those with relatively narrow bowls, 

 there is a tendency for the bowl to clog, when attempts are 

 made to produce cream testing 50 per cent fat or more. 



Generally speaking, it is safe to state that the machines 

 now on the market have reached such a degree of perfection 

 that they can be depended on to do close skimming when set 

 to produce cream containing not less than 18 per cent fat, nor 

 more than 50 per cent fat. This range of richness is sufficient 

 to embrace cream of any richness commercially advantageous. 



Effect of Smoothness of Running on the Skimming Effi- 

 ciency of the Separator. The separator cannot be expected to 

 do efficient work unless it runs smoothly. When the bowl re- 

 volves smoothly and without jarring, the skim milk and cream 



