72 THE BOOK OF CHEESE 



rennet. Within this range of temperature, the curd has 

 the physical characters demanded for making most vari- 

 eties of cheese. 



95. Strength of coagulating materials. Rennet and 

 pepsin preparations vary in strength and in keeping 

 quality. With a particular stock, changes go on to such 

 a degree that the last samples from a barrel of rennet are 

 much weaker than the earlier ones. Each sample, barrel, 

 keg or bottle should be tested before used. In continuous 

 work the results of each day's work furnish the guide for 

 the next day's use of a particular lot of rennet. 



96. Amount of coagulating materials to use. For 

 most varieties of cheese, sufficient rennet extract or 

 pepsin is added to the milk to give a firm curd in twenty- 

 five to forty minutes. Of the ordinary commercial rennet 

 extract, this requires from two and one-half to four 

 ounces to one thousand pounds of milk. This gives a 

 maximum of one part rennet for each four to six thousand 

 parts of milk. The great strength of the rennet extract 

 is thus clearly shown. 



97. Method of adding rennet. Before rennet is 

 added to the milk, it is diluted in about forty times its 

 volume of cold water, which chills the enzyme and retards 

 its action until it can be thoroughly mixed with the milk. 

 If the material is added without such dilution, the 

 concentrated extract produces instant coagulation in 

 the drops with which it comes in contact, forming solid 

 masses from which the enzyme escapes only slowly to 

 diffuse throughout the mass. Uniform coagulation thus 

 becomes impossible. After the rennet extract has been 

 diluted with cold water, it should be distributed the 

 entire length of the vat in an even stream from a pail. 

 It should then be mixed with the milk by stirring from 



