CHAPTER VII. 



MILK AXD CREAM. 



In order to realise the proper manipulation and methods oi 

 dealing with milk either for butter-making, cheese-making, or 

 retailing, it is necessary to understand its composition, its charac- 

 teristics and peculiarities. 



Milk is composed of a number of substances held in solution 

 or suspension in water. The proportions of these vary greatly in 

 different animals, and even in individuals of the same breed a con- 

 siderable amount of variation is found, more especially in the per- 

 centage of butter fat. The chief constituents of cow's milk are : 

 water, varying from 82 to 88 per cent. ; butter fat, from i"j to 6*6 

 per cent. ; casein, from 2'8 to 5^5 per cent. ; albumen, from '38 to 

 60 per cent. ; milk sugar, 2-9 to 5-25 per cent. ; mineral substances, 

 6 to 9 per cent. These are about the outside limits of variation, 

 but the following may be taken as a fair average composition of 

 ordinary milk : 



I'CT cent. 



Water - - 87-60 



Fat - 3-25 



Albumen 0-45 



Casein - 3-40 



Su<jar . 4 -- 5 



Ash or mineral substances 



ICO'OO 



Milk when drawn from the udder of the cow, if she be quite 

 healthy, is free from germs of any kind, and if put into a vessel 

 thoroughly sterilized, without being allowed to be contaminated 

 with any of the germs that are constantly floating in the air, or 

 that are continually falling from the body of the cow, will keep for 

 months or even years in a perfectly sweet condition, and will not 

 turn sour ; but, unless the most extraordinary precautions are 

 taken, it is almost impossible to obtain the milk germ-free, and, 

 commercially, it is impracticable. 



In diseased animals germs of the particular disease by which 

 they are infected pass through with the milk, and may thus cause 

 disease in the systems of those who drink the milk. This is 

 especially the case in tuberculosis, which is readily conveyed from 

 an affected cow to the human system ; in fact, it has been 

 pointed out by many scientists, who have made this matter a 

 careful study, that this dreaded disease is rarely ever found 

 among those who do not use cow's milk or flesh in any form, 



