148 



SCIENCE AND PRACTICE OF DAIRYING. 



If milk containing 3*3 per cent of fat be creamed at 30 C., the 

 cream will contain, according as it forms 15 or 20 per cent of the 

 milk, 19 to 20 per cent, or 14 to 15 per cent of fat. 



75. Condition of Cream and Skim-milk from Milk -separators. 

 When the work is carried out intelligently, the creaming of milk 

 by centrifugal force exercises a favourable action on the condition 

 of the cream and skim-milk; and it has long been proved that it is 

 easy to obtain butter which comes perfectly up to all requirements 



from cream obtained by 

 means of separators. The 

 very small loss in material 

 which milk suffers in cream- 

 ing, by a small portion of 

 the nitrogenous matter pass- 

 ing into the so-called sepa- 

 rator mud, is, it would seem, 

 in every respect, and espe- 

 cially so far as the condition 

 of the skim-milk is concerned, 

 quite unimportant. The ob- 

 taining of fine butter is de- 

 pendent upon the fulfilment 

 of the necessary condition, 

 that the cream, coming out 

 of the separator-drum, should 

 be cooled down as quickly 

 as possible, to 5 C., by the 



application of ice. If the cream be exposed for any length of time 

 at the temperature at which it leaves the drum its condition suffers, 

 as does that also of the butter into which it is made. Experience 

 has shown that it is not sufficient only to cool the cream partially 

 to 12 C. For cooling, cream-coolers of different construction may 

 be used. Refrigerators which have been largely used and tested 

 are the Lawrence coolers (fig. 45) coolers in which the cream 

 is cooled by being slowly passed over ribbed and comparatively 

 large metal surfaces in a thin stream, and the Laval cream -cooler 

 (fig. 46). Skim-milk, unless for use, ought to be cooled down, after 

 its removal from the drum, to at least 10 to 14 C. It is admirably 

 suited for use as human food, or for feeding calves and pigs. As it 

 is very poor in fat, however, it forms only a one-sided kind of food. 



Fig. 45. Lawrence's Refrigerator. 



