Bacteria in the Cheese Industry. 163 



When new factories are constructed it is of advantage 

 to introduce this necessary germ in quantities, and the 

 practice is sometimes followed of rubbing the walls and 

 cellars of the new location with material taken from the 

 old established factory. In this custom, developed in 

 purely an empirical manner, is to be seen a striking illus- 

 tration of a bacteriological process crudely carried out. 



In the Stilton cheese, one of the highly prized moldy 

 cheese of England, the desired mold fungus is intro- 

 duced into the green cheese by exchanging plugs taken 

 with a cheese trier from a ripe Stilton. 



In all probability, the breaking down of the casein is 

 attributable in part, at least, to the action of the inherent 

 ferments of the milk, although with some of the softer 

 cheese, this may be aided by bacterial action. 



172. Ripening 1 of soft cheese. The type of ripen- 

 ing which takes place in these softer cheese is materially 

 different from that which occurs in the first class. In 

 many cases, the peptonizing action does not go on uni- 

 formly throughout the cheese but is hastened on the ex- 

 terior by the development of organisms that exert a 

 solvent effect on the casein. For this reason, soft cheeses 

 are usually made up in small sizes, so that this action 

 may be facilitated. The bacteria that take part in this 

 process are those that are able to form unorganized fer- 

 ments (similar in their action to trypsin, galactase, etc.) , 

 and these soluble ferments gradually diffuse from the 

 outside through the cheese. 



Most of these peptonizing bacteria are hindered in their 

 growth by the presence of lactic acid, so that in many 

 cases, the appearance of the digesting organisms on the 

 surface is delayed until the acidity of the mass is re- 

 duced to the proper point by the development of other 

 organisms, principally molds, which prefer an acid sub- 



