THE DETECTION OF PASTEURIZED MILK 
W. D. Frost 
The necessity for pasteurizing all milk destined to be used 
as human food is becoming more and more firmly established 
ag the dangers from the use of raw milk are more generally 
recognized. But in order to further safeguard the public 
health it is necessary to control the methods of pasteurization. 
The range of temperatures permissible in pasteurization is 
very narrow. In order to render a milk safe it must be heated 
above the thermal death point of Bacillus tuberculosis. Only 
a few degrees above this necessary temperature the physical 
properties of milk are altered. The cream line is changed and 
a ‘‘cooked taste’? may be acquired. Both of these changes 
lessen the commercial value of the milk. Hence there is con- 
stant temptation for the milk dealer to underheat his milk. 
Public health authorities must therefore be constantly on 
the alert to prevent the sale of underheated or improperly 
pasteurized milk. 
How determine whether or not milk has been properly 
pasteurized? So far as I know the milk analyst is helpless 
unless he makes use of the method discussed here. 
It is true, of course, that various methods have been sug- 
gested. One of these proposes to regulate the temperature 
and time of holding in pasteurization. To this end certain 
municipalities require the use of automatic thermoregulators 
and recorders on all pasteurizing apparatus. A bacteriological 
test tells whether or not a milk is high or low in bacteria, but 
cannot always, by any means, indicate the thoroughness 
of the process of pasteurization. Other tests have been advo- 
cated which depend upon the changes which the protein under- 
goes in heated milk. These have not proved applicable in 
practice. Still others have been suggested which depend 
on the presence of oxidizing enzymes in milk. Of these, 
