178 FERMENTATION IN MILK 



belongs to the class of lactic acid bacteria, coagulating rnilk by 

 acid reaction, the bitter flavour becoming accentuated as the 

 coagulation proceeds. It liquefies gelatine, grows well in broth or 

 nutrient agar, and on potato gives rise to white colonies with yellow 

 margins. 



5. The tyrotJirix geniculatus of Duclaux} — Isolated from 

 Cantal cheese, and producing a bitter flavour both in milk and soft 

 cheeses ; the former, however, according to Duclaux, not proving 

 a favourable medium for the development of the organism. 



6. The bacillus albus of Loffler. — An organism resembling the 

 Bacillus subtilis, and taking in milk the form of threads. Liquefies 

 gelatine very rapidly, and forms a thick layer on agar. It produces 

 peptone and butyric acid.^ 



7. Bacillus liquefaciens lactis ainari of Freudenreich. — Isolated 

 from bitter cream. A motile bacillus of varying length (i«5 to 5 

 or 6 mm.) and averaging -5 mm. in breadth — liquefies gelatine and 

 coagulates milk, producing an intense bitter flavour without acid 

 reaction. 



8. The bacillus pseudo-butyricus of Hueppe is a peptonising 

 organism of the Hay bacillus type, which coagulates milk without 

 production of lactic acid. It liquefies gelatine rapidly, and forms 

 bluish-white growths upon agar. It will be remembered that 

 ordinary butyric fermentation {see p. 159) adds a bitterness to milk, 

 as Hueppe first pointed out. In his first paper, published in Berlin 

 in 1884, he definitely stated that bitterness was not due to lactic 

 acid bacteria, but to others present with them. In his second 

 paper (1891), Hueppe referred the bitter taste to M esentericus 

 vulgatus as well as to B. butyricus. He expressed the view that 

 bitterness was due to peptones, and supported his contention by 

 stating that all the bitter-producing organisms were peptonisers 

 and liquefiers of gelatine. 



To these must be added a series of organisms isolated and 

 studied by Fliigge, and designated by him as Bacillus lactis I., II., 

 III., IV., v., VI., VII., VIII., IX., X., XL, and XII., a description 

 of which will be found in the chapter on " Species." 



9. Torula aniara {Harrison).^ — Owing to the widespread com- 

 plaints as to bitterness, at Guelph in Canada, a careful investigation 

 was made by F. C. Harrison, with the result that amongst many 

 common organisms which were present he isolated a yeast to 



^ Le Lait, Duclaux, pp. 231-233, 



^ Klin. Wochenschr., 1889, p. 630. 



^ Centralb.f. Bakt.^ Bd. ix., No. 6/7, 1902, p. 206. 



