DEPARTMENT OF AGRICULTURE. 



PASTEURIZATION. 



From a sanitary standpoint, the value of pasteurization is of 

 greatest importance when market milk is under consideration. The 

 pasteurization of milk, when the process is properly performed, 

 affords protection from pathogenic organisms. Such disease-pro- 

 ducing bacteria as Bacillus tuberculosis , B. diphtherias, B. typhi, 

 and other organisms of the typhoid-paratyphoid group, and the 

 dysentery bacillus, when heated at 140 F. for 20 minutes or more 

 are destroyed, or at least lose their ability to produce disease. 



Occasionally results are reported, such as those of Twiss (30), 1 

 which again open the question as to the destruction of certain patho- 

 genic organisms by pasteurization. Using test organisms of the 

 typhoid-paratyphoid group, she obtained results which indicated 

 that there was not a complete destruction of these organisms when 

 heated in milk at 140 F. and even at 149 F. for 30 minutes. Krum- 

 wiede and Noble (24) , however, using some of the same test organ- 

 isms of the typhoid-paratyphoid group as used by Twiss, found that 

 they did not survive heating for 10 minutes at 140 F. They further 

 pointed out that the apparent heat resistance of the strains used by 

 Twiss was due to the method of determining their thermal death 

 point. 



According to Mohler (25), pasteurization offers protection against 

 foot-and-mouth disease. He makes the following statement : 



Milk which has been pasteurized for the elimination of tubercle and typhoid 

 bacilli will not prove capable of transmitting the disease (foot-and-mouth) to 

 persons or animals fed with it. 



In view of the outbreak of foot-and-mouth disease in this country 

 a few years ago this statement is of importance. 



The abortuslike bacteria in the udders of healthy cows which were 

 demonstrated by Evans (15) may also be considered in a discussion 

 of pasteurization. Although their sanitary significance has not been 

 definitely established, it is interesting to observe that it was found 

 by Evans (16) that both the pathogenic and lipolytic varieties could 

 be destroyed by heating to 125 F. for 30 minutes or to 145 F. for 

 30 seconds. 



Within recent years several epidemics of septic sore throat have 

 been traced to milk. In some of these epidemics it was found 

 possible, by pasteurization, to destroy streptococci which were iso- 

 lated from throats of infected people and which were believed to 

 be the infective agents. Pasteurization, properly performed, seems 

 to protect against epidemics of this kind, but until the organism 



'See References to literature. 



