CREA M -RIPEN ING. 



193 



fore, to produce butter with good keeping qualities it becomes 

 essential to exclude or suppress all germs which deteriorate 

 butter. It is not of so great importance to exclude germs 

 which do not injure the keeping quality of butter. The germs 

 that produce lactic acid do not cause direct deterioration 

 cf butter. This has been demonstrated by Jensen.* 



When cream has been properly ripened, it is practically a 



gr 



FIG. 127. The old Jensen cream-ripening vat. 



pure culture of lactic-acid-producing germs, while sweet un- 

 pasteurized cream contains a bacterial flora, consisting of a 

 great many types of desirable and undesirable germs. It 

 should be mentioned in connection with this, that it is only 

 properly ripened cream that contains with any certainty, a 

 preponderance of germs producing lactic acid. If the cream 

 is over-ripe, the undesirable bacteria may also gain the ascen- 



* Landwirtschaftliches Jahrbuch der Schweiz. 



