54 



MILK 



more rapidly than single globules, and consequently breaking up 

 of clusters by heat retards creaming. In addition, the liberation 

 of small globules decreases the volume of cream, since they remain 

 in the skimmed milk. These processes are favored by stirring 

 devices which are usually installed in milk-heating tanks. Heated 



Fig. 16. Fat globules in raw milk. In raw milk the fat globules are in 

 masses of varying sizes. These rise to the surface quickly in gravity creaming 

 (Russell and Hastings). 



milk will, therefore, never cream as rapidly as raw milk and the 

 quantity of cream obtained is less. The increased number of 

 small globules in heated milk also renders the cream line less dis- 

 tinct, and this fact has given rise to the erroneous idea that there 

 is less fat in the pasteurized product than in raw milk. 



Fig. 17. Fat globules in heated milk. When milk is heated the masses 

 of globules are broken up and fat globules are uniformly distributed through- 

 out the milk (Russell and Hastings) . 



4. The Depth of the Cream Layer. In shallow layers the glob- 

 ules have less space to traverse than in deep ones and less weight 

 to overcome, so that separation is more rapid and more complete 

 than in deep layers. Therefore creaming is usually carried on in 

 shallow pans, about 2 to 4 inches deep. 



