202 Milk and Its Products 
perhaps indefinitely, but such a starter will often 
improve in flavor qualities, particularly if propagated 
continuously in clean, sound, fresh, whole or skimmed 
milk. Many butter makers employ to advantage the 
practice of cultivating continuously in suitable small 
glass vessels several “mother” starters, from which 
they make selections from day to day of the best 
flavored for use in ripening. 
The use of starters in ripening has another advan- 
tage in that it makes it possible to first pasteurize the 
cream before ripening and so get rid of or reduce the 
effect of any undesirable fermentations that may be 
already present. This is of particular advantage where 
many lots of cream from many sources are brought to 
a central factory for churning. Such creams vary 
very much, even where, as is not often the case, none 
are already actually contaminated with some actually 
bad fermentation. By pasteurization and ripening with 
a good, pure culture starter, such creams can be made 
into butter of a good, uniform quality that would be 
‘entirely impossible without pasteurization. 
The amount of starter used will vary from 2 to 50 
per cent. Where a small amount is used, the purpose 
is to start and encourage the development of lactic 
acid through the whole mass of cream. Hence some 
time must elapse before the full effect of the starter is 
secured. Where a large amount is used, the purpose 
is not so much to encourage the formation of the acid 
as it is to impart directly the flavor already developed 
in the acid of the starter itself. 
The purer, the fresher, and the better flavored the 
