342 MICROBIOLOGY OF MILK AND MILK PRODUCTS. 



improved. This has been found to be true in practice and it is now 

 believed that pure cultures are of value not only in the ripening of sweet 

 cream, but that the addition of a relatively large amount of starter to 

 cream that is already fermented will enhance the value of the butter. 



USE or PURE CULTURES IN PASTEURIZED CREAM. It is evident that 

 the maker has but imperfect control over the fermentative processes when 

 raw cream is treated with a pure culture. To insure more perfect con- 

 trol the destruction of the contained bacteria and the subsequent inocula- 

 tion of the cream with a pure culture is indicated. The introduction 

 of the process of pasteurization of cream for butter making was due to 

 Storch. In Denmark this method is used almost exclusively. It has 

 been introduced into the other dairy countries of the world and is con- 

 stantly spreading. Pasteurization combined with the use of the pure 

 culture represents the highest type of modern butter making, and where 

 the raw product can be obtained in a fresh condition the butter maker 

 has perfect control over the bacteria that cause the ripening; hence can 

 control the flavor of the butter, both qualitatively and quantitatively. 



The intensity of flavor of butter is dependent upon the amount of 

 acid that is developed in the cream or on the ratio between the amount of 

 fat and the by-products of the acid fermentation. If these by-products 

 are small in amount, as in cream having a low acidity, the flavor of the 

 butter will be low. If the acidity is allowed to reach the maximum, 

 the flavor will be much higher. Thus the maker can control the intensity 

 of flavor of butter as accurately as he can the kind o.J flavor. With rich 

 cream, the acidity that can be developed is small and the ratio between 

 the fat and the products of fermentation is low; thus, the flavor of butter 

 made from very heavy cream is certain to be low. 



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 pro- 

 ducts 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 cream- 

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



