74; THE BOOK OF CHEESE 



(6) Heavily watered milk. 



(7) Use of badly rusted 1 cans. 



(8) Milk containing small amounts of casein or cal- 

 cium salts. 



Causes of uneven coagulation: 



(1) Uneven temperature of the mix in the vat, due 

 to lack of agitation. 



(2) Uneven distribution of the rennet extract. 



(3) Adding rennet to vat too soon after heating, while 

 the sides and bottom are still hot, causes curd to stick 

 to sides and bottom of the vat making cutting difficult. 



(4) Sloshing after the milk begins to thicken breaks 

 the curd and causes it to whey off. 



98. The curdling period. The time allowed for 

 rennet action also affects the texture of the 'curd. The 

 enzymes of rennet (rennin and pepsin) do not cease acting 

 with the thickening of the milk. In many cheeses, the 

 handling process begins as soon as the curd has become 

 solid enough to split cleanly before a finger thrust into 

 it. If let stand further, the same curd mass will con- 

 tinue to harden with the progressive separation of whey ; 

 this shows first as drops (" sweating ") on its surface, 

 which then increase in number and size until they run 

 together and form a sheet of whey. The limit of such 

 action is difficult to measure. The solidifying process 

 ceases in a period of hours. The further action of the 

 enzymes is digestive in character and goes on slowly. It 

 requires a period of weeks or even months to accomplish 

 measurable results at the working temperatures in use 

 in the trade. Other ripening agents with more rapid 



1 Olson, G. A., Rusty cans and their effect upon milk for 

 cheese-making, Wis. Exp. Sta. Bui. 162, pages 1-12, 1908. 



