333 
This effect is noted even at temperatures of 80°-90° C. This is 
shown by the following: 
Ten cubic centimeters of milk was heated to the following tem- 
peratures for five minutes, then cooled to 35° C., and 0.5 cubic centi- 
meter of rennin solution added, and time required for coagulation 
noted. The following results were obtained: 
Temperature (°C.). 
Time re- 
quired for 
coagulation 
(minutes). 
Temperature (°C.). 
Time re- 
quired for 
coagula- 
tion (min- 
utes). 
50 
41 
80 
6i 
60 
4 \ 
90 . .. 
8^ 
70 .... 
4i 
100 ... 
! 9* 
The probable explanation of the retardation of the rennin coagula- 
tion resulting from the heating of milk is that the calcium salts are 
partly rendered insoluble, probably through conversion into trical- 
cium phosphate, so that even the mineral constituents of milk seem 
to be somewhat altered by boiling. 
On the other hand there are those, among them Forbes-Ross (54), 
who contend that heat exerts no deleterious effect on the digestibility 
of milk, and that the feeding of infants with boiled milk is not in any 
way responsible for scurvy or rickets, but in reality is a wise precau- 
tion against infantile diarrhea and other bacterial diseases. Simi- 
larly Tjaden, Koske, and Hertel (55) claim that by rapidly heating 
the milk to 90° C., with constant shaking, the chemical and physical 
properties of the milk are in no wise altered nor is the value of the milk 
as a food in any way impaired. 
These fundamental differences of opinion regarding the effect of 
heat on the digestibility of milk can therefore only be settled by fur- 
ther investigations along this line. 
By way of comparison there are given in the subj oined table certain 
data pertaining to the destruction by heat of enzymes in general. 
This table has been compiled from observations recorded by Green 
(56), Oppenheimer (57), and others. 
Name of ferment. Temperature at which destroyed (°C.) . 
1 — — — j : 
Bromelin Weakened at 70. 
Caroubinase 80, weakened at 70. 
Cytase 60. 
Dextrinase 75. 
Diastase (plant) 80. 
Diastase (saliva) -. 65-70, slowly at 58. 
Emulsin 70. 
Enterokinase 65 (slowly). 
Invertase J 70, very slowly at 45-50. 
