Ripening of Cream. 



355 



different years, and the author believes that the tests must be 

 continued before definite conclusions can be drawn, 



Ripening of Cream. 



The Centralblatt jur Bakteriologie contains, in Nos. 2 1 and 

 22, 1901, an account of detailed investigations conducted by- 

 Messrs. H. W. Conn and W. M. Esten into the ripening of 

 cream. The conclusions to be drawn from these experiments 

 are summarised by the authors as follows : — 



Milk as it is drawn from the cow contains great quantities 

 of bacteria ; most of these are miscellaneous forms of lique- 

 fying bacteria and other non-acid species. At the outset the 

 number of acid bacteria is very small. 



All species of bacteria increase during the setting of the 

 milk for the separation of the cream. 



For a few hours the alkaline and other miscellaneous 

 bacteria increase rapidly, while the lactic bacteria are hardly 

 evident. 



After about 12 hours the lactic bacteria have increased 

 so much as to be as numerous as the others, and from this 

 time on they continue to increase with great rapidity until a 

 maximum is reached at about 48 hours ; after this the 

 numbers gradually decrease, and they finally practically 

 disappear. 



The ripened cream contains prodigious numbers of bac- 

 teria, larger numbers than are known in any other natural 

 medium. They are, however, nearly all lactic bacteria. 



After the first 12 hours all species of bacteria except the 

 two lactic species decrease in relative numbers, and finally 

 absolutely disappear. 



The two commonest species increase regularly from the 

 beginning of experiments until the maximum. 



The cream which is received by a creamery is already half 

 ripened, as indicated by the immense numbers of bacteria it 

 contains. All the changes which occur in the cream under 

 the influence of the miscellaneous bacteria have already 



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