BUTTER 601 



Creaming is facilitated if the milk is cooled rapidly after draw- 

 ing, and also by diluting it with about an equal volume of water, 

 by which means the viscosity is reduced and the rising of the fat 

 hastened. Dilution with water, however, usually leaves more 

 fat in the skimmed milk than is left by undiluted milk , and, furth- 

 ermore, the skimmed milk is so highly diluted that it is not suit- 

 able for further use. Diluting the milk for creaming is, there- 

 fore, not a common practice. 



Cream is now more generally separated from milk by means 

 of centrifugal separators. The advantages of the separator 

 method over that of gravity are so great that the original outlay 

 for a separator is soon compensated for. Centrifugal force sep- 

 arates the cream more completely than does gravity, so that the 

 ■ separated milk frequently contains less than 0.1 per cent, fat, often 

 as little as 0.05 per cent. This is one important gain, and another is 

 the fact that a concentrated cream containing 60 or more per cent, 

 butter-fat can be obtained, while gravity cream rarely contains 

 more than 20 per cent, butter-fat. However, it is not desirable 

 to use a cream of more than 45 per cent, fat for butter making, 

 as otherwise the viscosity becomes so great that a part of the cream 

 adheres to the sides of the churn, making proper agitation impossi- 

 ble and causing the yield of butter to suffer. 



A further advantage of separator cream is derived from the 

 fact that it is separated while perfectly fresh, still warm with 

 animal heat. Bacterial decomposition has no time to take place 

 and the ripening process can be more efficiently controlled. As a 

 matter of fact, a large number of micro-organisms are thrown out 

 by the centrifugal force. 



When milk is subjected to centrifugal force it separates into 

 three parts, namely: 1, the cream — being the Hghtest part — moves 

 toward the center; 2, the separator milk, and 3, the heaviest parts 

 of the milk — consisting of insoluble salts, dirt, casein, cellular 

 elements, and micro-organisms — are thrown on the wall of the 

 bowl. These last constituents form a thick, slimy mass, known 

 as the separator slime or bowl sediment. 



The richness of the cream is controlled by a screw with a hole 

 through which the cream — in some machines — or the skimmed 

 milk— in others — flows. The nearer the hole in the screw is to 

 the center, the richer is the cream, or if the screw controls the 

 skimmed milk, the nearer the hole is to the periphery, the richer 

 is the cream. The rate at which the milk flows into the separator 

 also influences the richness of the cream. A low rate of speed in 

 the machine produces a leaner cream than a high rate, and finally 

 a high temperature causes a rapid flow of cream of low fat con- 

 tent. The temperature, however, should not be so low as to in- 



