YEASTS AND MOLDS IN BUTTER 305 



arrives at the creamery, but if it be efficiently pasteurized and 

 kept from subsequent contamination, the mere fact of their 

 presence in the raw cream does not mean that the butter made 

 from this cream will be either defective in flavor, when made, or 

 lacking in keeping quahty. 



A study, by Bouska and Brown, of a large number of pack- 

 ages of butter placed in cold storage showed that the number of 

 yeasts and molds present in butter, when made, is a fair cri- 

 terion from which to judge of its keeping quality. To put it 

 in another way, the number of yeasts and molds present in 

 butter, as it comes from the churn, is a good indication as to the 

 efficiency of pasteurization and the subsequent handling of the 

 cream to prevent re-contamination. 



The laboratory of the American Association of Creamery 

 Butter Manufacturers has, for a number of years, made counts 

 of the number of yeasts and molds in samples of butter sent in 

 by its members, for this purpose. As a result of this work, and 

 the advice and assistance given, many of the creameries have so 

 improved their methods and equipment as to practically elim- 

 inate yeasts and molds from their butter, and make a product 

 possessing good flavor when fresh and good keeping qualities. 



Where the number of yeasts and molds in butter is reduced 

 to ten or less per cubic centimeter — colonies counted without the 

 aid of a magnifying glass — this is regarded as excellent work; 

 and several of the creameries have reached this stage of effi- 

 ciency. A strong effort should be made by every creamery to 

 keep the number of yeasts and molds as low as possible, that is, 

 to thoroughly pasteurize the cream and prevent subsequent 

 contamination. 



Whether or not the yeasts and molds present in butter are a 

 direct cause of deterioration is not definitely known, although 

 there are reasons for belie^'ing that this is not necessarily so. 

 Hastings found yeasts to be present in butter which won first 

 prize in a Wisconsin educational contest. The presence in 

 butter of yeasts and molds in large numbers usually means the 

 presence of other undesirable organisms in the cream, due to 

 one or more of the following causes: 



