Preparation of Rennet 247 



and is less liable to introduce taints and bad flavors, 

 than a ferment made from sour whey, and with a little 

 care and attention, the fermentation will go on regu- 

 larly from day to day. 



Rennet The ordinary source of rennet is the 

 fourth or digestive stomach of a calf that has not 

 yet ceased to live upon milk, though rennet is also 

 found in the stomachs of puppies and pigs, and the 

 latter have occasionally been used as a source of 

 rennet. The active principle of the rennet- is found 

 in the folds of the lining membrane of the stomach 

 of the animal, and is greatest in amount when a full 

 meal is just digested. 



Rennet causes coagulation of the casein by con- 

 tact, and is not itself affected by the change. Its 

 action, however, is greatly modified by various con- 

 ditions of the milk, the most important of which 

 are the temperature and the condition of certain of 

 the ash constituents. Rennet is most active at tem- 

 peratures near the body heat, 98 F. At temper- 

 atures below 80 F., the action of rennet is corre- 

 spondingly slow. On the other hand as the temper- 

 ature is raised above 100 F., the activity of the 

 rennet- is at first increased, but after about 130 F. 

 is reached the active principle is rapidly weakened 

 and finally destroyed at about 140 F. 



The activity of rennet is also intimately connected 

 with the lime salts in the ash of the milk, and par- 

 ticularly with their condition as to solubility. The 

 presence of soluble salts of lime renders rennet much 

 more active, while the insoluble salts of lime have 



