174 MODERN METHODS OF TESTING MILK 



METHOD OF TESTING PEPSIN 



Pepsin is beginning to be used in cheese-making as 

 a substitute for rennet-extract. Vivian has worked 

 out the important details. The scale-pepsin, of strength 

 known as 1-3,000, prepared from stomachs of sheep, 

 is recommended. It may be used at the rate of 5 

 grams for 1,000 pounds of milk. In testing scale- 

 pepsin by the rennet test, one can dissolve the scale- 

 pepsin at the rate of 5 grams in 4 ounces of water and 

 use this solution exactly like a rennet-extract with 

 milk. It should be tested in comparison with a sam- 

 ple of rennet-extract whose use in cheese-making has 

 been tested, the test being made on different portions 

 of the same milk. 



TESTING THE AGE OF MILK BY RENNET-TEST 



The age of milks and the care with which they have 

 been kept can also be tested in a comparative way by 

 the rennet-test, since with the same rennet-extract or 

 pepsin solution different milks generally coagulate 

 more rapidly in proportion to the amount of acid con- 

 tained in them, especially if the amount of lactic acid 

 is considerable. 



