MICRO-ORGANISMS AND ENZYMS 



309 



stances, which are used in milk as preservatives. The 

 foregoing table shows the results of some work done 

 at the New York experiment station on this point. 



It has been shown at the Wisconsin experiment 

 station that some metals exert a retarding effect on the 

 coagulating action of rennet. As a practical applica- 

 tion, it is pointed out that in rusty milk-cans enough 

 iron may be dissolved by milk that is at all acid to 

 interfere with the rennet coagulation. 



(5) Finely divided, inert matter, like starch or 

 sawdust, added to milk, hastens the coagulation by 

 rennet. 



(6) The temperature of the milk affects (i) the 

 time of coagulation, and (2) the character of the 

 curd. 



(a) For complete coagulation, the time de- 

 creases when the temperature increases. 



Temperature, F. 

 Time, seconds. . . 



75° 

 270 



80° 

 140 



85° 

 110 



90° 

 80 



95° 

 65 



Stated in another way, the coagulation in a given 

 time is most complete at 106° to 108° F. and less 

 complete at temperatures above and below these 

 limits. Fleischmann gives the following figures, 

 indicating the proportion of milk-casein coagulated in 

 the same period of time required to effect complete 

 coagulation at 106° to 108° F. 



Proportion of milk- 

 Temperature casein coagulated 



68° ; 18 per cent 



77° 44 per cent 



86° 71 per cent 



95° 86 percent 



104° 98 per cent 



106°. 100 per cent 



113° 89 per cent 



122° SO per cent 



