670 BACTERIA IN ARTICLES OP FOOD. 



the bacteria which produce unwholesome chaL-g^s in milk are several 

 which cause it to become viscous or soapy. Among these we may 

 mention Micrococcus lactis viscosus of Conn, Micrococcus Freuden- 

 reichi of Guillebeau, Bacillus mesentericus vulgatus, and Bacillus 

 lactis saponacei of Weighmann and Zirn. A considerable number 

 of bacilli are known which give rise to the production of butyric 

 acid fermentation in milk and its products. Some of these are an- 

 aerobic and some aerobic. The list includes the following : Bacillus 

 butyricus of Prazmowski, Bacillus of Liborius, Bacillus of Botkin, 

 Bacilli of Kadrowski. 



The bitter taste which milk and cheese sometimes acquire is due 

 to the presence of special bacterial ferments ; among these the best 

 known are an aerobic, liquefying micrococcus described by Conn, a 

 bacillus described by Weighmann, Micrococcus casei amari and Ba- 

 cillus liquefaciens lactis amari of De Freudenreich (1895). 



In fresh butter of good quality comparatively few microorganisms 

 are found, but the researches of Conn show that the characteristic 

 and agreeable flavor of fresh butter is due to, or at least may be imi- 

 tated by, a bacillus which is concerned in the ripening of cream 

 under normal conditions. Cultures of this bacillus (Bacillus 41 of 

 Conn) have already been used in a practical way by butter makers 

 to improve the flavor of their product. 



Krenger (1890) obtained from "cheesy butter," having a disa- 

 greeable odor, various bacteria. Among these the most numer- 

 ous were an oval micrococcus (Micrococcus acidi lactici, Kreuger), a 

 slender bacillus resembling Bacillus fluorescens, and Bacillus acidi 

 lactici of Hueppe. 



Klecki (1894) has isolated from rancid butter several bacteria not 

 previously described, one or more of which are no doubt concerned 

 in the production of the rancid taste and odor. These are described 

 under the following names: Bacillus butyri, Diplococcus butyri, a 

 bacillus resembling lodococcus vaginatus of Miller, Tetracoccus 

 butyri, Bacillus butyri No. 2. 



Duclaux (1887) has isolated from different kinds of cheese no less 

 than eleven different species of bacteria, which he believes are con- 

 cerned in the "ripening process." Seven of these are aerobic and 

 four anaerobic species. Adametz (1889) has also isolated and studied 

 a number of species to which he attributes the ripening of cheese. 



More recently Henrici (1895) has studied the bacterial flora of 

 cheese, and Marchal (1895) has shown that the ripening of certain 

 kinds of cheese (fromages mous) is probably due to Oidinm lactis. 



Meats, even when salted and smoked, may contain living patho- 

 genic bacteria which were present prior to the death of the animal, 

 and, when not properly preserved, are of course liable to be invaded 

 by putrefactive bacteria. 



