TESTS USED IN CHEESE-MAKING 433 



rennet-extract is added to the milk is noted by the 

 second hand of a watch, and then again when the 

 milk has coagulated; the number of seconds re- 

 quired to coagulate the milk is recorded. The 

 exact point of coagulation can be seen more 

 sharply by scattering a few particles of charcoal 

 (as the blackened end of a partly burned match) 

 on the surface of the milk, and then with the ther- 

 mometer starting the surface into motion around the 

 dish. The black particles stop the instant the milk 

 coagulates. By using a stop-watch great accuracy 

 and delicacy can be attained. Care should be taken 

 to keep the temperature of the milk at the one desired 

 point, testing frequently with the thermometer; and 

 in case the temperature drops, it can be raised by 

 placing the basin of milk in warm water. In ordinary 

 cheddar cheese-making, milk is ready for the addition 

 of rennet when it coagulates in 30 to 60 seconds under 

 the foregoing conditions. 



METHOD OF TESTING RENNET-EXTRACTS 



Different brands of rennet-extract vary somewhat 

 in their strength , that is, the rapidity and completeness 

 with which they coagulate milk when used in the same 

 amount. It is therefore important to have a means of 

 testing their strength, in order that their value may 

 be definitely known and that cheese-makers may be 

 able to know in advance of using how much they must 

 use for the best results. The Monrad and Marschall 

 tests are available for this purpose. 



In order to test the comparative strength of differ- 

 ent rennet-extracts, one treats different portions of 

 the same milk with the different extracts to be tested. 



