BITTER MILK 177 



workers have pointed out that certain foods and certain diseases of 

 the udder produce bitter milk. Advanced lactation is said also to 

 bring about this condition under certain circumstances. 



There can, however, be little doubt that the chief cause of 

 bitterness in milk is due to the growth of micro-organisms. Such 

 bitterness appears, not immediately after milking, but only after 

 an incubation period. 



Amongst the organisms now generally recognised as prime 

 agents in the causation of the disease, are : — 



1. The bacillus von bittere milch of IVeigtnann. — A small, thread- 

 like, motile, spore-bearing bacillus of 1-5 to i-8 mm. in length. 



This bacillus was found in sweet milk, and turned sterilised 

 milk bitter in twenty-four hours. It does not digest casein, nor 

 does it produce butyric acid. VVeigmann thought the bitterness 

 was due to the decomposition of the albuminoids of milk. 



2. Conn's micrococcus of bitter milk is an aerobic coccus isolated 

 from bitter cream, which, inoculated into nutrient gelatine, liquefies 

 it and makes it slimy and of bitter taste. It coagulates milk, with 

 subsequent gradual liquefaction of the precipitate, and production 

 of an intensely bitter flavour and a slight acid reaction. The 

 presence of butyric acid was determined in the culture, and butter 

 made from the bitter milk soon became rancid. This organism is 

 of particular interest as being the first microbe of bitter milk 

 naturally experienced. 



Although, as we have already said, the above two organisms 

 may be looked upon as the principal agents in the causation of the 

 disease, it must be noted that many other organisms, and especially 

 those of the Hay bacillus group, almost all of which seem to have 

 the power of peptonising casein with the production of a markedly 

 bitter flavour, are endowed with the property of producing a 

 bitterness in milk and its products. Amongst these may be cited : 



3. TJie bacillus of bitter milk of Bleisch — A facultative anaerobe, 

 motile, flagellated, spore-bearing bacillus, liquefying gelatine, and 

 producing a whitish-grey growth upon agar and potato. It was 

 first isolated from imperfectly sterilised milk. According to 

 Bleisch, the spores of this organism can withstand boiling for a 

 lengthened period.^ 



4. The micrococcus casei aniari of Freudenreichr- — Isolated from 

 bitter cheese, and which, inoculated into milk, produces a markedly 

 bitter flavour both in it and the resultant cheese. This organism 



^ Zeitschrift f. Hyg., Bd. xii., 1893, P- 81. 

 * Ann. de Micrographia^ Bd. vii,, 1895, p. i. 



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