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THE COAGULATION OF CONDENSED MILK. 



By R. Greig-Smith, D.Sc, Macleay Bacteriologist to the 



Society. 



Much has been written about the sliminess of milk and of the 

 bacteria which bring about the change. But the literature 

 respecting a similar change in condensed milk is so scanty that 

 I have not been able to find any publication dealing with the 

 subject. It may be that the matter has never been treated, and 

 yet for reasons that will be seen later, the trouble can hardly be 

 unknown to the manufacturers of condensed milk. 



The specimen of coagulated or " Jellitied " milk which I 

 received had been made some six months previously, and when 

 opened, the milk was seen as a stiff, rather dark-tinted jelly of 

 the consistency of stiff starch-paste. Upon vigorously stirring 

 the milk, it became thin but returned to its stiff consistency upon 

 standing. 



The n)icroscopical examination of the jelly showed amongst 

 the crystals of lactose, a number ^of clusters of needle-shaped 

 crystals. These were also seen in normal condensed milk, but 

 were not so numerous. The clusters were not affected by dilute 

 alkali but dissolved in dilute acid, leaving a nucleus or residuum 

 of microbic cells. A small quantity of these crystals was 

 obtained by centrifugalising the diluted milk, and dissolved in 

 nitric acid and tested for phosphoric acid, with negative results. 



It was difficult to say whether the microbes were sarcinae or 

 staphylococci; they were large-sized and stained deeply, the stain 

 being retained by the Gram method. They occurred i?i pairs 

 and in groups, each individual measuring 1'5 fi. Upon cultivation 

 they grew as small cocci, Ifi in diameter. 



The formation of the jelly does not proceed uniformly through- 

 out the milk, but begins at a number of points. These appear as 

 small blobs of the size of millet seed. The thickening then 



