94 



THE STORY OF MILK 



and loss of butter-fat in the whey. Most cheesemakers 

 therefore prefer rennet when they can get it. 



The rennet having been added, the milk is left un- 

 disturbed until a firm curd has been formed. When 

 the curd breaks or splits sharply before the finger 

 pushed slowly through it, it is ready to be ''cut." 



Cutting. — Two sets of curd knives are used, each 

 consisting of a metal frame in which tinned steel blades 



are hung, in one vertically 

 and in the other horizontally. 

 The vertical knife is first car- 

 ried slowly through the curd 

 lengthwise and crosswise; the 

 horizontal set of blades is 

 then moved carefully through 

 the length of the vat. When 

 the cutting is over, the entire 

 mass should be in cubes about 

 half an inch square. 



The whey that begins to 

 separate out should be clear 

 and yellow. Milky whey is a 

 sign that the butter-fat is es- 

 caping in it; the curd has 

 been broken up too violently. 

 In curdling, the casein encases 

 the butter-fat and the object of the breaking up of 

 the curd in the vat is to expel the whey but retain the 

 fat in the cheese. 



" Cooking " the Curd. — Gentle heat is now applied to 

 raise the temperature gradually to 98° or 100° in the 

 course of about 30 minutes. Meanwhile the small 

 pieces of curd are kept floating in the whey by gentle 



Curd knives 



