414 



CREAM. 



The following is the average composition of well-prepared 

 separated milk : 



Water, 

 Fat, . 

 Milk-sugar, 

 Casein, 

 Albumin, 

 Ash, . 



90-48 per cent. 

 0-12 

 4-88 

 3-22 

 0-42 

 0-78 



Control of Separators. The most important point in the 

 control of separators is the estimation of the fat left in the separ- 

 ated milk. A separator leaving a proportion of fat appreciably 

 higher than that deduced from the formula given above is working 

 badly, and the cause should be investigated at once. It is im- 

 portant that the speed be properly maintained, that the milk 

 be at the right temperature, and that the exit tubes be not 

 clogged up ; the chemist should make a practice of visiting the 

 separators daily while they are running and of checking the 

 speed and temperature of the milk. At least one sample of 

 separated milk should be tested from each " run " of the separ- 

 ator ; these samples should be taken from the skim outflow 

 tube, at some period of the run, preferably not immediately after 

 starting. 



A further means of controlling the separators is to compare 

 the total weight of the fat in the cream, separated milk, and 

 the milk left in the drum after separating, with the total weight 

 of the fat in the milk separated. This is done by weighing each 

 product, multiplying the weight by the percentage of fat and 

 dividing by 100. The total weight of fat in the cream and 

 separated milk should be nearly equal to that in the milk, the 

 difference representing loss in separating ; the average loss 

 should not amount to more than 2 per cent, of the total fat in 

 the milk. 



Separator Slime. After running a separator a viscous sub- 

 stance is found pn the inside of the drum. It is usually of a 

 dirty white colour ; but if the milk contains much solid impurity, 

 as happens most frequently in the winter, it may be distinctly 

 brown. 



This by no means consists, as is often considered, of dirt and 

 cow-dung, though it naturally contains these impurities if present 

 in the milk. Microscopical examination shows it to contain 



1. Inorganic impurities i.e., dust gathered during transport, 

 and earthy matters due to uncleanliness. 



2. Vegetable matters derived from the dust of the food given 

 to the cattle e.g., bark of hay, fine particles of cake, etc. ; in 

 many cases portions of leaves with stomata developed may be 



