EXPERIMENT STATION BULLETINS. 209 



PASTEURIZATION OF MILK. 



CHARLES E. MARSHALL. 



Bulletin 147. — Bacteriological Department. 



It is not our purpose to give a general discussion of this topic, for a 

 bulletin devoted to that theme has already been issued from this station 

 by Prof. C. D. Smith. We shall be limited to certain experimental data 

 which will add to the fund of information gleaned from the general 

 consideration. 



Heretofore the study of Pasteurized milk has been confined to the pro- 

 cess in its entirety. Our efforts have been along another line, and we 

 have approached the subject from another standpoint, hoping thereby to 

 gain an insight into the hidden changes of the process. Pasteurization is 

 aimed at the bacteria in milk, and we have endeavored to isolate some of 

 the bacteria remaining after Pasteurization for the purpose of studying 

 them in pure cultures and of ascertaining their relation to Pasteurization. 



Our work and consideration may be resolved into the following heads: 



1. The isolation of species from Pasteurized milk — those species left 

 in milk after Pasteurization and not yielding to Pasteurizing treatment. 



2. Determining the source of such bacteria. 



3. The study of their a ctions upon milk. 



4. The investigation of the thermal dea f h-points of the species isolated. 



5. The effect of sudden cooling after Pasteurization upon the species 

 isolated. 



6. The restraining influence of cold upon ihe species isolated. 



7. The restraining influence of he r d upon the species isolated. 



8. The restraining influence of heat followed by a low temperature 

 upon the species isolated. 



9. Suggestions as to the reduction of infection. 

 10. The value of Pasteurization. 



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