ENZYMS OF MILK AND BUTTER 1 
By R. W. Thatcher, Director , Minnesota Agricultural Experiment Station , and A. C. 
Dahlberg, Assistant Dairy Husbandman , Agricultural Experiment 
Station. 
INTRODUCTION 
The deterioration of butter during storage is often attributed to the 
enzyms in the buttermilk which it contains. There has been some 
experimental study of the matter; but most of the published results of 
these investigations yield little information concerning the actual enzym 
content of butter, because of the fact that the studies dealt chiefly with 
the chemical changes in the butter itself during storage, and sufficient 
care was not used to prevent possible contamination by microorganisms. 
In fact, a survey of the literature dealing with the enzyms of milk and 
its products shows a lamentable lack of clearness on the part of the 
investigators in distinguishing between the enzyms of milk itself and 
those which are due to bacterial infections. 
Rogers (16) 2 found lipase to be the cause of the increase in the acidity 
of canned butter on standing. Rahn, Brown, and Smith (13) stated 
that 
all (storage) butter investigated showed an increase of “ amid nitrogen, *' i. e., nitrogen 
not precipitated by copper sulphate, tannic acid, or phosphotungstic acid. 
Their methods were shown to be at fault by Rogers, Berg, Potteiger, 
and Davis (77), who could observe 
no evidence of an increase in soluble nitrogen in butter on long standing at o° F., 
even when the conditions of manufacture were most favorable to such changes. 
They could detect no proteolysis in buttermilk held a long period of 
time in cold storage to which 18 per cent of sodium chlorid had been 
added, but active bacterial proteases, pepsin, and trypsin were not 
completely inhibited in their action by these adverse conditions. Lac¬ 
tose, they concluded, was oxidized only when a trace of iron and peroxid 
were added. 
During the summer of 1915 one of us (Dahlberg), as a part of his 
duties in the Division of Dairy and Animal Husbandry of the Minnesota 
Agricultural Experiment Station, prepared several lots of butter under 
carefully controlled conditions of manufacture and placed them in stor- 
1 Published, with the permission of the Director, as Paper No. 71 of the Journal Series of the Minne¬ 
sota Agricultural Experiment Station. 
2 Reference is made by number (italic) to “ Literature cited," pp. 448-450. 
Journal of Agricultural Research, 
Washington, D. C. 
kt 
(437) 
Vol. XI, No. 9 
Nov. 26,1917 
Key No. Minn.—23 
