424 Bacteria in Relation to Country Life 



Fahr., and a pure-culture starter of lactic-acid bacteria 

 is added. After the desired degree of acidity is developed 

 by the bacteria, the casein is coagulated by means of 

 rennet, the curd is cut, stirred and dipped into forms. 

 It is then allowed to drain, without artificial pressure, 

 for four or five hours, and is inoculated with spores of 

 the proper mold. After being salted, the cheese is ready 

 to go through the ripening process, which requires 

 about four weeks for its. completion, and which involves 

 the gradual change of the hard curd into a soft, waxy 

 substance. 



The softening begins near the surface and slowly 

 spreads towards the center of the mass. " When in prime 

 condition, the cheese is soft enough to spread upon bread 

 or crackers, but not soft enough to run. An over-ripened 

 cheese, however, becomes still Softer, until, in time, the 

 whole interior of the cheese below the rind is converted 

 into a nearly liquid consistency, which will run out of 

 the cheese readily, if the rind is broken. On the other 

 hand, an under-ripened cheese will show more or less 

 of the sour curd in the center, which has not been affected 

 by the softening agents. The cheeses purchased in the 

 market are, very frequently, in one of these two con- 

 ditions, either over-ripe or under-ripe." 



The lactic-acid bacteria of the milk and the starter 

 soon become predominant in the cheese, almost entirely 

 excluding the other species. In some of the experiments, 

 the lactic-acid bacteria reached a maximum number 

 of about 900,000,000 per cubic centimeter in two days, 

 constituting then practically a pure culture. This 

 number was maintained throughout most of the ripening 



