Bacteria in Butter-Making. 133 



the same. This destroys for the most part the vegeta- 

 tive bacteria, leaving the latent spore forms in the cream. 

 The addition then of a properly propagated starter gives 

 the selected organism snch an impetus that it should be 

 able to overcome any other organism in the cream. Where 

 pure cultures are employed extensively, as in Denmark 

 and Germany, this method of cream-ripening is followed. 



The attempt has been made to use these culture start- 

 ers in raw sweet cream, but it can scarcely be expected 

 that the most beneficial results will be attained in this 

 way. This method has been justified on the basis of the 

 following experiments. Where cream is pasteurized and 

 no starter is added, the spore-bearing forms frequently 

 produce undesirable flavors. These can almost always 

 be controlled if a culture starter is added, the obnoxious 

 form being repressed by the presence of the added starter. 

 This condition is interpreted as indicating that the addi- 

 tion of a starter to cream which already contains devel- 

 oping bacteria will prevent those originally present in the 

 cream from growing. 1 This repressive action of one 

 species on another is a well-known bacteriological fact, 

 but it must be remembered that such an explanation is 

 only applicable in those cases where the culture organ- 

 ism exercises a direct prejudicial influence on the exist- 

 ing flora of the cream. 



If the culture organism is added to raw milk or cream 

 which already contains a flora that is eminently adapted 

 for development in this medium, it is quite doubtful 

 whether the culture organism would gain the supremacy 

 in the ripening cream. The above method of adding a 

 culture to raw cream renders cream-ripening details less 

 burdensome, but at the same time Danish experience, 



1 Conn, 9th Storrs Expt. Stat., p. 25, 1896. 



