A LACTOSE FERMENTING YEAST PRODUCING FOAMY 



CREAM 



O. W. HUNTER 



Dairy Bacteriologist, Karisas Agricultural Experiment Station 



Received for publication, June 11, 1917 



Large amounts of cream are lost during the hot summer 

 months from an undesirable fermentation known as ''foamy 

 cream." This loss is due chiefly to the mechanical action of the 

 fermentation, rather than to the effect of undesirable odors and 

 flavors, for often one-third to one-half of the cream is lost from 

 the can through foaming while in transit. The fermentation is 

 best identified by this characteristic foaming action and by the 

 yeasty or fruity odor imparted to the cream. 



EXAMINATION OF CREAM 



Numerous samples of foamy cream collected from different 

 parts of Kansas by the State Dairy Commissioner have been sent 

 to the bacteriological laboratory for analysis. The microbial 

 flora as revealed by direct microscopic examination and by 

 plate cultures proved to be similar for all samples. The cream 

 was plated on whey and lactose agar respectively. The latter 

 medium was acidified with 1 cc. of a 1 per cent tartaric acid solu- 

 tion per tube of medium. 



Yeast cells were very prominent, as well as rod shaped bacteria, 

 which appeared as short or long filaments and showed numerous 

 granules on staining. The latter organism upon isolation proved 

 to be a member of the B. bulgaricus group. 



All cream showing such a flora caused foaminess when placed 

 in raw or sterile cream ; and the inoculated cream always exhibited 

 a microbial flora identical with that of the original product. 



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