Nov. 26, 1917 
Enzyms of Milk and Butter 
441 
Sample 5 was buttermilk obtained from a small hand churning and 
probably contained 1 per cent of butter fat. Since fat destroys the 
anesthetic property of chloroform by combining with it, the results of 
No. 5 should not be considered. In every other case 1 per cent of chlo¬ 
roform in skim milk or buttermilk completely inhibited proteolysis. 
(< d) The influence of sodium cheorid on proteoeysis. —The pos¬ 
sibility that the sodium chlorid present in ordinary butter might inhibit 
proteolytic activity led us to make a study of the effect of varying per¬ 
centages of sodium chlorid added to skim milk upon the rate of produc¬ 
tion of soluble nitrogen by galactase. After the period of incubation 
the unchanged casein was precipitated from the milk by means of dilute 
acetic acid and the soluble nitrogen in the filtrate determined by the 
Kjeldahl method. The samples were preserved during the incubation 
by 0.75 per cent chloroform. The following results were obtained 
(Table III). 
Table III .—Influence of sodium chlorid on the proteolysis of milk (with 0.75 per cent of 
chloroform) 
Sodium chlorid added. 
Total 
nitrogen. 
Initial 
soluble 
nitrogen. 
Soluble 
nitrogen 
after 
21 days. 
Soluble 
nitrogen 
after 
72 days. 
Increase. 
Per cent. * 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
0.0 boiled. 
O. 0561 
O. 0055 
O. 0051 
0. 0034 
“ 3 * 74 
• 0561 
. 0121 
. 0188 
. 0198 
13. 72 
. 0561 
. 0121 
. 0171 
8. 91 
. . 
. 0561 
. 0121 
. 0142 
. 0131 
x. 78 
I c.O. 
. 0^34 
. 0121 
. 0110 
— 2. 06 
. 0528 
. 0121 
. 0120 
■ 0103 
- 3 - 40 
The effect of sodium chlorid is marked; both 15 and 20 per cent, the 
concentration of the salt brine in butter, stopped all proteolysis. The 
very slight increase in the soluble nitrogen content of the skim milk 
containing 1 per cent of the salt is partially due to the excessive chloro¬ 
form used, as the following tests, in which only 0.5 per cent of the anes¬ 
thetic was used, will show (Table IV). 
Table IV .—Influence of sodium chlorid on the proteolysis of milk (with 0.5 per cent of 
chloroform) 
Sodium chlorid added. 
Total 
nitrogen. 
Initial 
soluble 
nitrogen. 
Soluble 
nitrogen 
after 
S days. 
Increase. 
Per cent. 
0.0 boiled. 
Per cent. 
0. 0586 
. 0586 
. 0586 
. 0586 
Per cent. 
O. 0033 
. 0108 
. 0108 
. 0108 
Per cent. 
0. 0034 
. 0242 
. 0201 
• 0143 
Per cent. 
O. 51 
22 . 86 
15 - 87 
5-97 
.o. 
.8 .-. 
7 .0. 
