Bacteria in Cheese. 173 



Digestive bacterial theory. The first theory propounded 

 was that of Duclaux, 1 who in 1887 advanced the idea that 

 this change was due to that type of bacteria which is able 

 to liquefy gelatin, peptonize milk, and cause a hydrolytic 

 change in proteids. To this widely-spread group that he 

 found in cheese, he gave the generic name Tyrothrix 

 (cheese hairs). According to him, these organisms do not 

 function directly as ripening agents, but they secrete an 

 enzym or unorganized ferment to which he applies the 

 name casease. This ferment acts upon the casein of milk, 

 converting it into a soluble product known as caseone. 

 These organisms are found in normal milk, and if they 

 function as casein transformers, one would naturally expect 

 them to be present, at least frequently, if not predominat- 

 ing in the ripening cheese; but such is not the case. In 

 typical cheddar or Swiss cheese, they rapidly disappear 

 (p. 168), although in the moister, softer varieties, they per- 

 sist for considerable periods of time. According to Freud- 

 enreich, even where these organisms are added in large 

 numbers to the curd, they soon perish, an observation that 

 is not regarded as correct by the later adherents to the di- 

 gestive bacterial theory, as Adametz and Winkler. 



Duclaux's experiments were made with liquid media for 

 isolation purposes, and his work, therefore, cannot be re- 

 garded as satisfactory as that carried out with more modern 

 technical methods. Recently this theory has been revived 

 by Adametz, 2 who claims to have found in Em men thaler 

 cheese a digesting species, one of the Tyrothrix type, which 

 is capable of peptonizing the casein and at the same time 

 producing the characteristic flavor of this class of cheese. 



i Duclaux, Le Lait, p. 213. 



Adametz, Oest. Molk. Zeit., 1900, Nos. 16-18. 



