434 SCIENCE AND PRACTICE OF CHEESE-MAKING 



In all other respects, the details of the methods pre- 

 viously given are followed. All conditions must be 

 kept alike in the different tests. The strength of the 

 rennet-extracts is shown by the rapidity with which 

 the milk is coagulated; the stronger the rennet, the 

 less the time of coagulation. 



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 1-3000, 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. 



TESTS FOR FERMENTS AND INSOLUBLE 

 DIRT IN MILK 



Those forms of micro-organisms or ferments that 

 make trouble in cheese-making are not readily per- 

 ceptible to the senses when milk is delivered at the 

 cheese-factory, but the results of their work develop 

 later either during the cheese-making process or later 

 in ripening cheese. When such ferments appear, 

 it is desirable to locate them in some particular herd 

 or herds with a view to removal of the causes of 



