THE DAIRY. 123 



cream from 1001b. of new milk '07 to '20 lb. of fat was 

 left in the buttermilk. 



Cheese. — This substance is prepared by the action of 

 rennet on milk. The rennet solidifies the milk by 

 separating the casein from solution ; the fat globules are 

 separated at the same time, being entangled in the curd 

 formed. Rennet is a watery extract prepared from the 

 fourth stomach of the calf; its power of coagulating milk is 

 apparently due to the presence of a ferment, which doubt- 

 less plays a similar part in the ordinaiy process of diges- 

 tion in the calf's stomach. The action of rennet is very 

 slow in the case of cold milk, it becomes much more 

 energetic as the temperature rises; at 135° Fahr. it ceases 

 to act. Milk becomes sour when curdled by rennet, but 

 the production of acid (lactic acid) is not essential to the 

 curdling. 



The composition of cheese depends principally on that 

 of the milk from which it is made ; rich cheese is made 

 from new milk, cream being sometimes added to the milk 

 for the production of the richest sorts ; poorer kinds of 

 cheese are made from milk wholly or partially skimmed. 



The temperature at which the milk is curdled is of 

 great importance. If the temperature is low, the curd 

 is very tender and the whey difficult to separate ; if, on 

 the other hand, the heat is too great, the curd shrinks too 

 much, and becomes hard and dry. A temperature from 

 74° to 84° is generally employed, the lower temperature 

 for thin cheeses, the higher (80° to 84°) for thick. 



When the curd is sufficiently firm it is carefully cut in 

 all directions, and the whey allowed to drain off. To 

 facilitate the drainage of the whey the curd is often 



