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Scientific Proceedings (130) 



The number of viable B. acidophilus in milk held in the ice- 

 box at about 9° C. was determined daily. The viable organisms 

 were killed as follows : after 1 day — about 50 per cent. ; after 2 

 days — about 75 per cent. ; after 3 days about 90 per cent., etc. 

 The obvious importance of having a large number of viable or- 

 ganisms is manifested in the necessity for increasing dosage in 

 severe cases. In fact, it is likely that in cases reported as fail- 

 ures, a sufficient increase in the number of viable organisms ad- 

 ministered might have resulted in success. The practice of ice- 

 boxing B. acidophilus has little to recommend it beyond pre- 

 serving the palatability of the culture and it is therefore more 

 desirable to keep B. acidophilus at room temperature. 



A study was made of the influence of time and pressure in 

 autoclaving milk, prior to inoculation with B. acidophilus, with 

 respect to the growth of the organism. Milk was sterilized at 

 15 and 20 pounds pressure in the autoclave for different periods 

 of time and inoculated with B. acidophilus. Subcultures were 

 made from each set of flasks for 3 days on milk identically ster- 

 ilized, thus obtaining acclimatization. On the basis of these 

 comparative tests it was found that milk to be used for inocula- 

 tion with B. acidophilus should be sterilized in the autoclave at 

 20 pounds pressure for 20 minutes, or at 15 pounds pressure for 

 20 to 30 minutes. Under these conditions a maximum number 

 of viable organisms is obtained after incubation. 



It was necessary for certain experimental purposes to pas- 

 teurize B. acidophilus milk. By exposing B. acidophilus milk 

 to different temperatures for different periods of time it was 

 found that it could be completely sterilized in one litre portions 

 in the Arnold steam sterilizer for 10 minutes (with a final tem- 

 perature of 81° C.) In attempting to kill B. acidophilus in milk 

 by freezing, it was found that after 6 days at about 3° C. the 

 original number of viable organisms was reduced 99.95 per cent. 

 This again emphasizes the drastic action of low temperature on 

 this organism. 



