No. 6. DEPARTMENT OF AG inCULTUKE. S75 



bj meaus of ceutiifugal force. Hence, we have in use two general 

 methods of cream separation, (1) the gravity system, and (2) the 

 centrifugal or- separator sj'stem. 



18. Gravity Method of Cream Separation. 



The gravity method of cream separation has been used in two dif- 

 ferent forms, one kiiown as the ''shallow-pan" system and the other 

 as the ''deep-setting" system. 



(1.) Cream Raising by Shallow-Pan System. — This is the oldest 

 method employed in separating cream from milk. It is still em- 

 ployed in many small dairies. To obtain the best results with this 

 method, the milk should be placed in the pans at once after milking 

 and should be cooled to 00 degrees F. within a reasonably short 

 time, and should then remain quiet at about that temperature for 

 thirty-sis hours or more. The dej^th of milk in the pao may be 

 from two to four inches, \yhen cold running water can be used to 

 surround the pans ,the depth may be from four to six inches. Ordi- 

 narily a cool, clean cellar, well ventilated, furnishes good condi- 

 tions. Any place where the milk can be exposed to bad odors or to 

 dust should be avoided. There are some serious objections to this 

 method of creaming, among which may be mentioned (a) exposure 

 of a large surface of milk to air for a long time, thus giving unusual 

 opportunity for bacteria to get into the milk; (b) a temperature 

 permitting the rapid increase of bacteria by growth; (c) incomplete 

 separation of fat-globules from the milk serum; (d) wasteful loss 

 of cream in skimming; (e) drying out of cream, making it liable 

 to go into butter in dried chunks and injure the texture. (f) The 

 amount of acid io the cream is apt to become too great, thus injuring 

 the flavor of the butter. It has been found that skim-milk obta-'ned 

 by the shallow-pan system of creaming seldoTu contains less than 

 0.5 per cent, of fat, while the average of actual practice is much 

 higher, amounting to about one-fifth of the entire fat present in the 

 milk. 



(2.) Cream Raising by Deep-Setting System.— This method has 

 been in use between thirty asid forty years, probably reaching its 

 most extensive use ten years ago. It was found that by using long 

 pails or cans, not more than a foot in diameter, and placing these, 

 filled with fresh milk, in a tank; of water kept at 40 degrees F., the 

 cream would separate more completely and in much less time than 

 it w-ould when raised in shallow pa«s, twelve to twenty-four hours 

 being suflficieut for the separation. This system is capable of re- 

 ducing the loss of fat in skim-milk to 0.2 per cent., when the most 



