12 BULLETIN 240, U. S. DEPARTMENT OF AGRICULTURE. 



for 30 minutes and then drawn off while hot through the outlet pipe 

 into hot milk bottles which had been steamed 2 minutes. As stated 

 before, this method of bottling milk while hot was suggested in Cir- 

 cular 184 of the Bureau of Animal Industry (5), but the suggestion 

 then was to bottle hot milk in cold bottles. In this work it seemed 

 advisable to bottle directly into hot bottles, as it makes it possible 

 to steam the bottles and fill them before infection can take place. 

 Also, this method eliminates the possibility of breaking bottles. 

 While working on this process of bottling milk hot it has been found 

 that a similar process was apparently patented several years ago, but, 

 so far as known, it has never been used to any extent. This process 

 as described by de Schweinitz (7) consisted in pasteurizing the milk 

 at temperatures from 160° to 180° F. and placing it while hot in a 

 sterilized milk jar or fruit jar with a flap top. Special paper caps 

 were used. The jars of milk were cooled by being placed in troughs 

 of iced water. 



COMPARISON OF BACTERIAL REDUCTIONS IN MILK PASTEURIZED 

 IN BOTTLES AND MILK PASTEURIZED IN BULK AND BOTTLED 

 WHILE HOT. 



Since it has been shown earlier in this bulletin that excellent bac- 

 terial reductions may be obtained by pasteurization in bottles, a 

 question of great importance arises as to whether or not as good 

 results can be obtained by pasteurizing milk in bulk and bottling 

 while hot. 



A series of 22 samples of raw milk was pasteurized by both proc- 

 esses at 145° F. for 30 minutes. Part of the milk was pasteurized in 

 bulk in the pasteurizer shown in fig. 7 and bottled hot in hot bottles 

 which had been previously steamed for two minutes. In all these 

 experiments the bottles were capped with ordinary paper caps, no 

 precautions being used in capping by hand. Another portion of the 

 same raw milk was pasteurized in bottles. Both samples of pasteur- 

 ized milk were examined bacteriologically while hot in the bottles. 



In the first series the bottles in which the milk was pasteurized 

 directly were washed with hot water and washing powder imme- 

 diately before they were filled with raw milk. 



