ENZYMES. 37 
destroyed, but it will be rendered much weaker. These high 
temperatures do not destroy the power of the rennet instantly 
but gradually. 
75. Rennet Does Not Exhaust Itself. 
As has been said concerning enzymes, rennet does not seem 
to spend its energy, but will act over and over again. Ifa 
quantity of milk is coagulated and the whey applied to a like 
quantity of milk, the milk will be coagulated; this might be done 
indefinitely, if it were not for getting a larger volume of whey 
than we have of milk. 
76. Effect of Acid on the Action of Rennet. 
It has been said that the rapidity in the action of rennet is 
greatly affected by the temperature of the milk, but we find, if 
the temperature of the milk is held constant, the more lactic acid 
there is in the milk the faster the rennet will act, or if some acid 
be artificially added to the milk in quantities not sufficient to 
coagulate it, the action of the rennet will te hastened; on 
the other hand, if alkali be added to the milk, the action of the 
rennet will be retarded. 
77. Rennet Extracts Not Alike. 
Another cause for varying rapidity of rennet action is the 
difference in the strength of the rennet extracts used. Rennets 
vary as to the amount of ferment contained in them, and it is 
very unlikely that two lots of extracts will be exactly alike in 
their action. 
78. Rennet Action Dependent on Three Factors. 
It has been shown that the ‘rapidity with which rennet co- 
agulates milk is dependent on: 
1. The strength of the rennet extract. 
2. The temperature of the milk. 
3. The acidity of the milk. 
If the same rennet is used at the same temperature of the 
milk each time, the variation in the rapidity with which the co- 
agulates the milk, must be due solely to the acidity or ripeness 
of the milk. 
