92 GUIDE TO DAIRYING IN SOUTH AFRICA 



when working in clean milk, a healthy ferment when 

 the organisms are living and not harmful as a food. 

 But should the milk have been standing three or 

 four days and there is no more acid being formed, 

 it is nothing but a putrid mass and should never be 

 eaten. 



Cream. 



Cream may ordinarily be described as that part 

 of the milk which rises to or near the surface when 

 it is left standing for a short while. The milk fat 

 being the lightest part of milk naturally rises, and 

 thus cream is composed mostly of milk fat. The 

 method of gathering cream by letting the milk stand 

 is too long for present-day use. We therefore use 

 a centrifugal machine which on receiving whole 

 milk into its works divides it into two parts, the 

 lightest and the heaviest. The machine used, of 

 course, is the ordinary separator. Now the separator 

 does not take out the fat in its pure form, but a 

 certain proportion of water and other parts of the 

 milk go with it. Thus, if we put 100 Ibs. of milk 

 through a separator at suitable temperature, 85 F. 

 to 90 F., we shall get on an average 20 Ibs. of 

 cream and 80 Ibs. of skim milk. The fat left in the 

 separator milk, or skim milk as it is called, will vary 

 from 0*05 % to as high as 0x25 %, while the pro- 

 portion of milk fat in cream will vary from 8 % 

 to as high as 60 %, according to the thickness at 

 which the cream is taken or method of working the 



