CURD-MAKING 63 



with the milk, using the small spatula to stir it. 

 The rennet and milk should be mixed until it has run 

 down at least one-half space on the scale in the cup. As 

 the rennet begins to coagulate the milk, it runs slower 

 from the hole in the bottom of the cup, until it finally 

 stops. When it stops, the point on the scale indicated 

 by the surface of the coagulated milk is noted. The 

 test is recorded by the number of spaces the surface of 

 the milk lowers from the time the rennet is added until 

 it is coagulated. This test depends on three factors : 

 the strength of the rennet extract, the temperature of 

 the milk, the acidity of the milk. The more acid, the 

 quicker the milk will coagulate. To measure any one 

 of these factors, the other two must be constant. 

 The variable factor is the acidity of the milk. This test 

 will not indicate the percentage of acid in the milk, but is 

 simply a comparative test to be used from day to day; 

 for example, if the rennet test to-day shows three spaces, 

 and the operator makes that milk into cheese and the 

 process seems to be normal, it shows that for good results 

 in this factory, milk should be ripened to show three 

 spaces every day. If the next day the milk showed four 

 spaces, it should be allowed to ripen more until it shows 

 three spaces. If it shows only two spaces, this indicates 

 that the milk has too much acid development or is over- 

 ripe. A cheese-maker will have to determine at what 

 point to set his milk, because the test will vary from one 

 factory to another. 



84. Comparison of acid and rennet test. Each of 

 these tests has its advantages and disadvantages. The 

 advantage of the acid test is that it can be made as 

 well of warm as cold milk. This is of great impor- 

 tance in determining whether the milk delivered by any 



