PASTEUEIZING MILK. 



15 



milk bottles for each sample were inoculated with equal amounts of 

 sour milk. One of these infected bottles was then steamed for two 

 minutes and filled with hot pasteurized milk and the other contami- 

 nated bottle not heated was filled with some of the same pasteurized 

 milk, which had been previously cooled in a sterile bottle. An exami- 

 nation of Table 4 shows, when the figures in columns A and C are 

 compared, that the infectious material added to the bottle was en- 

 tirely destroyed by the method of bottling, at least so far as bac- 

 teriological methods can detect, since any marked increase in column 

 C would show infection. Column B shows the bacterial counts 

 obtained by putting cold pasteurized milk into infected bottles. From 

 these results it is evident that the process of bottling hot pasteurized 

 milk in hot, steamed (two minutes) bottles entirely eliminates the 

 factor of bottle infection, which may often be serious in the ordinary 

 processes of pasteurization on a commercial scale. 



Table 4. — Destruction of bottle infection during the process of bottling hot 



pasteurized milk. 



Sample No. 



Raw milk. 



Hot pasteur- 

 ized milk in 

 hot steamed 

 bottles. 



Cold pasteur- 

 ized milk in 

 cold infected 

 bottles. 1 



Hot pasteur- 

 ized milk in 

 steamed in- 

 fected bot- 

 tles.! 





A 



B 



C 



24 



Bacteria 

 per c. c. 



24, 900 

 94, 000 

 235, 000 

 176, 000 

 97, 000 

 230, 000 

 124, COO 

 190,000 



Bacteria 

 perc.c. 



380 

 860 

 5,400 

 2,200 

 5,900 

 6,300 

 920 

 7,500 



Bacteria 



per c. c. 



6, 400, 000 



5, 600, 000 



1,330,000 



1,510,000 



235, 000 



355,000 



305,000 



Bacteria 

 per c. c. 



460 



25 



600 



27 2 



4,800 



28 



2,400 



29 2 



4,100 



30 2 



5,800 



312 



950 



35 2 



8,800 









1 Bottles bad been previously infected with several cubic centimeters of sour milk. 



2 Bottle infected with old, sour, pasteurized milk. 



The question naturally arose as to whether or not pasteurization 

 in bottles would destroy infection in bottles specially infected before 

 being filled with raw milk. To determine this point nine samples 

 of milk were pasteurized which had been previously steamed and 

 cooled. The results are shown in Table 5. One bottle for each 

 sample was steamed, cooled, infected with several cubic centimeters 

 of sour milk, and filled with some of the original raw milk. Samples 

 were then plated from this bottle to show the extent of the infection, 

 the results of which may be found in column B of the table. The 

 bottle of infected raw milk was capped with a seal cap and the milk 

 pasteurized directly in the bottle. Plates were made directly after 

 the heating and the bacteriological results are shown in column C. 

 Any increase in the counts in column C over those in column A shows 



