146 



DAIRY BACTERIOLOGY 



of acid present in the interior of soft cheeses inhibit the action of 

 the ripening factors hitherto considered, they promote the proteo- 

 lytic action of the rennet and conserve its enzyme in an active 

 state for a much longer time than is the case in the hard cheeses *. 

 As will have been gathered from the preceding remarks, the soft 

 cheeses may be divided into two groups : (a) The " smeared " 

 cheeses ; in these the moulds are suppressed and prevented from 

 forming aerial hyphse by daily smearing the cheeses either with 

 a wet cloth or by hand, keeping them moist and protecting them 

 as much as possible from the air by packing them closely together. 

 (b) The mouldy cheeses ; in these the growth of moulds is favoured 

 by touching the surfaces of the cheeses as little as possible, keeping 

 them dry and providing for free access of air. 



The copious production of ammonia on the surface of the best- 

 known of the smeared cheeses, Limburger and Romadour, has been 

 found by the author 2 to be due to a symbiosis of peptonising 

 tetracocci and Bacterium casei limburgensis. The latter is a 

 non-motile, very irregular short rod which does not ferment 

 lactose ; it forms a film on media containing calcium lactate, and 

 oxidises the lactic acid to acetic and carbonic acids ; it does not 

 attack casein, but forms traces of ammonia in milk, from the 

 amino acids, which has a slight solvent action on the casein. 

 This organism is therefore to be classed with the bacteria which 

 produce a soapy taste in milk. Its most characteristic property 

 is its ability to carry further the decomposition of the products of 

 protein hydrolysis which have been produced by other micro- 

 organisms ; this is most strikingly illustrated by inoculating it 

 into milk together with Tetracoccus liquefaciens. 



The smeared crust of Limburger cheese consists, according to 

 the unpublished researches of Freudenreich, chiefly of Bacterium 

 casei limburgensis together with smaller numbers of peptonising 

 organisms (chiefly Tetracoccus liquefaciens, a small spore-forming 



1 Orla Jensen, " Centralblatt f. Bakt.," 2 Abt., 1900, Bd. VI., p. 795. 

 * " Studier over de flygtige Syrer i Ost, etc.", Doctoral thesis, 1904. p. 74. 



