110 SCIENCE AND PRACTICE OF DAIRYING. 



equable creaming temperature. The time occupied in cream-raising, 

 the form and the material of the vessels used in the cream-raising, 

 the depth of the milk-layer in the vessel, the rules laid down with 

 regard to the condition of the room in which the cream-raising is 

 carried on, and the method in which the cream is removed, also vary 

 according to the method adopted. In all methods of cream-raising 

 the milk possesses an equable temperature during only a portion of 

 the entire cream-raising period. During the first hours, that is, 

 until it has been gradually cooled down to the prescribed tempera- 

 ture, milk creams at a comparatively higher temperature, since 

 the resistance offered to the fatty globules is comparatively less. 

 The creaming temperature is, therefore, the lowest temperature to 

 which milk is cooled down, and at which milk is sought to be kept. 

 It varies in the different methods of cream-raising here considered 

 between 9 and 24 C. 



The more particular conditions under which the coagulation of 

 the caseous matter is unfavourable for creaming have been already 

 dealt with in 21, when discussing milk which creams with 

 difficulty. 



It is always a disadvantage if the highly favourable conditions 

 which exist during the first hours after milking are not utilized for 

 creaming. Experience has taught that milk which has been kept 

 for some time after milking and has been cooled, or again disturbed, 

 or left temporarily quiet, and again disturbed, always yields a less 

 satisfactory quantity of cream than milk derived from the same 

 source which is at once set after milking. 



That the slightest disturbance of milk during cream-raising 

 exercises an appreciable influence on the collection of fat in the 

 cream can be easily understood when we remember the compara- 

 tively small quantity of fat globules distributed throughout the 

 milk. For this reason, it is only natural that under like conditions, 

 the less milk is disturbed, the greater the quantity of fat obtained in 

 the cream. The collection of fat on the surface of milk at first 

 takes place very rapidly, and diminishes the longer it proceeds. Even 

 when the cream-layer which has been formed is no longer increased, 

 its percentage of fat nevertheless continues to increase steadily as 

 long as the creaming continues. For this reason, in every method 

 of cream-raising, there is a certain period of time, the so-called 

 cream-raising time, at the conclusion of which the cream is removed, 

 since the increase in the percentage of fat in the cream after this 



