236 CREAM RIPENING 



not to be recommended, it has the same objections as the use 

 of buttermilk. Then, again, the butterfat as well as the non-fatty 

 constituents in this sour cream are thus exposed to a double 

 ripening period; this is considered undesirable because of the 

 possible action of the acid on these cream constituents, lower- 

 ing their resistance to oxidation, if not actually starting oxida- 

 tion, or cleavage by hydrolysis, thereby jeopardizing the quality 

 of the butter. . 



Spontaneously soured milk or skim milk starter is pref- 

 erable to either buttermilk or sour cream, provided that in its 

 preparation a high sanitary quality of raw material, milk or 

 skim milk, has been selected. Otherwise, the ripening of cream 

 by the use of such starters may be no better than the natural 

 ripening of cream. 



Milk or skim milk starters and possibly starters made from 

 condensed and powdered milk, soured with pure cultures of 

 lactic acid bacteria, are the only really dependable starters and 

 it is the use of this group of starters which will be exclusively 

 considered in the discussion of artificial cream ripening. 



The ripening of cream by means of pure culture starters is 

 a practice which has come into more general use in this country 

 only within the last score of years. Its application is largely 

 the result of investigations of Storch. 1 



Artificial cream ripening may be divided into two classes, 

 namely, ripening by the addition of a sufficient amount of 

 starter to raw cream to control fermentations, and 2. ripening 

 of cream in which the majority of bacteria and other ferments 

 have been destroyed by pasteurization and which, after cooling 

 has been inoculated with a lactic acid starter. 



Either of these methods is preferable to the natural ripen- 

 ing process, inasmuch as they both assist in regulating fermenta- 

 tion by accelerating the development of desirable lactic bacteria 

 to the partial* exclusion of other organisms. In the case of 

 artificial ripening of raw cream, the control of the fermentations 

 may, however, be less complete and the final results less cer- 

 tain than when the cream is first pasteurized. The raw cream 

 has a mixed flora which may consist of both desirable and un- 



1 Storch, Eighteenth Annual Report of Danish Experiment Station, 1890. 



