32 



THE STORY OF MILK 



special care and in Denmark where the country is fairly 

 permeated with the lactic acid bacilli used in ripening 

 the cream for the celebrated Danish butter and where 

 careful buttermakers often maintain their starters for 

 months or even for years without '^renewal/' 



There are many different varieties of bacteria which 

 convert sugar of milk into lactic acid, at the same time 

 developing flavors more or less agreeable and charac- 

 teristic for the various 

 products. In the bac- 

 teriological laboratory 

 certain species are se- 

 lected which will pro- 

 duce the results de- 

 sired for the particular 

 purpose in view. 



Starters. — Beginning 

 with a commercial dry 

 culture in the form of 

 a powder as generally 

 used in the creamery 

 or the cheese factory 

 as well as for the prepa- 

 ration of commercial buttermilk, or with buttermilk tab- 

 lets as used in the ordinary household or the hospital, 

 such culture is added to a small quantity of thoroughly 

 pasteurized milk. If fresh, sweet skim milk is available it 

 is preferable to whole milk as the butter-fat in the latter 

 only interferes with the process; but either can be used. 



Milk for starters should be strongly pasteurized by 

 being kept at a temperature near the boiling point — 

 at least 180° — for 40 to 60 minutes, then cooled to the 

 degree at which it is to be set, usually between 65° and 



Typical lactic acid bacteria 

 (L. A. Rogers) 



