Separation of Whey 249 



the rennet for use from the skins. In the prepara- 

 tion of the extract, the skins are soaked in warm 

 water to which a little salt has been added until the 

 active principle has been completely removed from 

 them. The resulting extract is filtered, and preserva- 

 tives, in the shape of salt and a little saltpetre, 

 are added. Rennet so prepared will retain its 

 strength and purity for a considerable length of 

 time, if kept in a cool, dark place. 



Removal of whey. After the coagulation of the 

 milk is complete its constitution is as follows : 92.5 

 parts soluble, 7.5 parts insoluble. The soluble por- 

 tions are made up of water 87, sugar 4.5, albumin 

 .75, ash .25. The insoluble are made up of casein 

 3.25, fat 3.75, ash .5. The separation of these two 

 is the chief task of the cheese maker, and is brought 

 about partly by mechanical and partly by chemical or 

 physical agents. The chief mechanical agents in 

 the separation are cutting the curd, stirring, and the 

 application of pressure. The chemical and phys- 

 ical agents in effecting the separation are : First, 

 application of heat ; second, development of lactic 

 acid ; third, addition of salt ; fourth, curing fermenta- 

 tion. These various agents may be applied in va- 

 rious degrees and in various ways, all of which have 

 a greater or less effect upon the character of the 

 resulting cheese, producing an almost endless variety 

 of product. The process that we shall describe is 

 one in common use in America, although first prac- 

 ticed in England. It it known as the American 

 Cheddar process, and is a modification in minor de- 



