142 Dairy Bacteriology. 



nently suited to their development, e. g. the lactic-acid 

 class, are either neutral or beneficial in their effect on 

 butter. 



Use of Starters. Experience has amply demonstrated 

 that it is possible to control the nature of the fermentative 

 changes that occur in ripening cream to such an extent as 

 to materially improve the quality of the butter. This is 

 frequently done by the addition of a " starter." While 

 starters have been employed for man}' years for the purpose 

 mentioned, it is only recently that their nature has been 

 understood. A starter may be selected from widely diver- 

 gent sources, but in all cases it is sure to contain a large 

 number of bacteria, and the presumption is that they are 

 of such a nature as to produce desirable fermentative 

 changes in the cream. 



In the selection of these so-called natural starters, it fol- 

 lows that they must be chosen under such conditions as 

 experience has shown to give favorable results. For this 

 purpose, whole milk from a single animal is often used 

 where the same is observed to sour with the production of 

 no gas or other undesirable taint. A skim-milk starter 

 from a mixed supply is recommended by many. Butter 

 milk is frequently employed, but in the opinion of butter 

 experts is not as suitable as the others mentioned. 



It not infrequently happens that the practical operator 

 may be misled in selecting a starter that is not desirable, 

 or by continuing its use after it has become contaminated. 



In 1890 1 a new system of cream ripening was intro- 

 duced in Denmark by Storch that possesses the merit of 

 being a truly scientific and at the same time practical 

 method. This consisted in the use of pure cultures of 



Storch, Milch Zeit., 1890, p. 304. 



