EFFECT OF LOW TEMPERATURES 



Ill- 



been suggested as a simple method of determining the pre- 

 vailing type of organisms and will be considered in detail on 

 p. 197. 



The development of bacteria in milk at low temperatures 

 was especially studied by Re venal, Hastings and Hammer. 23 

 Two samples of milk differing widely in bacterial content were 

 stored at C. and the count made at intervals on lactose 

 agar by incubating at 37 C. 



TABLE XLV 



That profound modifications had occurred was shown by 

 the fact that at the end of the experiment over 70 per cent of 

 the caseinogen was digested. The total nitrogen decreased, due 

 to liberation of nitrogen in the free state. Pennington 24 also 

 found a digestion of caseinogen when milk was stored at low 

 temperatures, over 50 per cent being digested in five to six 

 weeks at 29-32 F. 



The above results show the importance of storing, milk at 

 as low a temperature as is practicable; although 50 F. may be 

 regarded as the critical point for bacterial development, efforts 

 should be made to lower the temperature of milk samples as 

 far as possible if more than a few hours (3-4) elapse between 

 collection and examination. If the samples are immediately 

 surrounded with ice they may be kept for twenty-four hours 

 without altering the significance of the results although the 



