CREAM-RIPENING. 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 
of butter. This has been demonstrated by Jensen.* 
When cream has been properly ripened, it is practically a 
| 5 Gal 
: 
| 
Fie. 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. 
