327 
the milk above certain temperatures. On account of the important 
bearing which the thermal death point of milk ferments may have 
on the pasteurization of milk the following data relative to this 
subject are here submitted: 
Galactase . — According to Babcock and Russell (18), the destruc- 
tion temperature of galactase, the proteolytic enzyme of milk, is 
somewhat higher than the thermal death point of trypsin. So far 
as its proteolytic activity is concerned, these observers found it 
to be weakened by heating for ten minutes at 76°-80° C. That 
such is the case may be seen from the following table, in which is 
shown the percentage of soluble nitrogen which milks which had 
been heated for ten minutes at the temperature indicated, con- 
tained at the end of fifty-three days. 
TABLE I. 
Temperature to 
which the ga- 
lactase was 
heated for 10 
minutes before 
being allowed 
to act on the 
milk. 
Per cent of 
soluble nitro- 
gen after 
53 days at 
37° C.a 
78— 80°C. 
0.05 
76 
.05 
71 
.12 
65 
.20 
60 
.20 
a The soluble nitrogen originally present in the milk used, in these experiments was found to he 0.05 
per cent. 
Similar tests were made upon the proteolytic activity toward gela- 
tin of galactase which had been heated for ten minutes at different 
temperatures, using Fermi’s (19) method. Equal amounts of the 
galactase solution were poured over the surface of carbolized gelatin 
contained in test tubes and kept under observation seven weeks. 
The results of this series of experiments is given in Table II. 
TABLE II. 
[+ + =rapid digestion; +=digestion by galactase; — =no digestion.] 
Reaction of the galactase solu- 
tion. 
Temperature ( ° C. ). 
Alkaline. 
Neutral. 
Acid. 
N/10 ! 
N/20 
N/10. 
65 
++ 
70 
75 
80 
Control 
+ 
++ 
+ 
