Fermentation &j of M'dk. 101 



Butter milk is also prepared by allowing milk to sour 

 and then breaking up the curd by stirring. If the type 

 of fermentation is controlled as may be done (see Chap- 

 ter VII), such a form of fermented milk is a most de- 

 sirable drink. It is probably as healthful and has all 

 the therapeutic properties that are ascribed to other 

 forms of fermented milks such as the Bulgarian "Yog- 

 hurt." 



This type of fermented milk is produced by an acid- 

 forming organism that can form large amounts of acid, 

 2.0 or 3.0 per cent. The casein is dissolved to some ex- 

 tent and the remainder so changed, that it will remain 

 in suspension for a long time in a finely divided form, 

 after the curd has been broken up. Such milk is sold 

 under various names at home and abroad. One of the 

 authors (H) has found such organisms in practically all 

 milks examined. If raw milk is kept warm (98 to 100 

 F.) in a stoppered bottle which is filled full, the acidity 

 will be found to increase slowly from day to day, reach- 

 ing a maximum in ten to fourteen days. If the milk, is 

 then examined, it will be found to contain large num- 

 bers of an acid-forming organism very different in ap- 

 pearance from the bacteria causing the rapid souring 

 of milk at ordinary temperatures. This organism is 

 very similar if not identical with the one found in the 

 Bulgarian milk to which the name B. Bulgarians has 

 been given. The use of the milk fermented by this or- 

 ganism has spread rapidly because it is claimed by cer- 

 tain European bacteriologists that it has a favorable 

 effect on the health of people, especially those suffering 

 from intestinal troubles. It is not at all certain that 

 ordinary sour milk or butter milk will not have the same 

 effect; in fact in many of the fermented milks sold in 



