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 

 as 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 011 

 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, 



