482 MICROBIOLOGY OF MILK AND MILK PRODUCTS 



PURE CULTURES IN OLEOMARGARINE AND RENOVATED BUTTER. 

 It was previously mentioned that the manufacturer of butter substi- 

 tutes employs the same methods to impart butter flavor to his prod- 

 ucts as does the butter-maker. The oleomargarine manufacturers 

 employ pure cultures of lactic bacteria for the fermenting of milk 

 that is mixed with the fats they employ. The same practice is followed 

 by the manufacturer of renovated butter. Many of the creameries 

 of the western states receive cream that is shipped long distances, 

 and is collected from the farms but once or twice a week. It is thus 

 in an advanced state of fermentation when it reaches the creamery. 

 In order to prepare from this grade of cream, which often has a most 

 undesirable flavor, a merchantable product, various means are em- 

 ployed to remove the flavoring substances and to replace them with 

 desirable flavors from the pure cultures. The acidity may be reduced 

 by the addition of lime so that the cream can be pasteurized; the 

 cream may be aerated by passing air through it, or it may be mixed 

 with water and reseparated. After such treatment it is mixed with 

 a large proportion of milk fermented by a pure culture and churned. 

 The resulting product is constantly sold as the highest grade of creamery 

 butter. 



ABNORMAL FLAVORS or BUTTER. Most of the abnormal flavors of 

 butter are traceable to the partial replacement of the desirable acid- 

 forming bacteria with other types of microorganisms Many samples 

 of butter having abnormal flavors have been examined, and the organ- 

 isms believed to be the cause isolated and studied but it cannot be said 

 that any particular group of microorganisms can be associated with any 

 of the abnormal flavors met. It is asserted that " oily " butter, i.e., that 

 having the taste of machine oil, is caused by bacteria and by microorgan- 

 isms that decompose the fat, as Oidium lactis, yeasts, and liquefying bac- 

 teria. Organisms of the B. coll group that produce a turnip-like flavor 

 in butter have been described by Weigmann. The flavors of putrid 

 butter, fishy butter and also many other abnormal flavors have been 

 ascribed to bacteria. 



Other abnormal flavors may be due to the presence in the milk of 

 certain aromatic principles contained in the feed and excreted in the 

 milk. Cabbage, turnips, and other plants impart their characteristic 

 taste to the milk and butter. 



