248 PRACTICAL DAIRY BACTERIOLOGY 



product. 1 The growth of these two organisms together neu- 

 tralizes the acid of the curd at the surface of the cheese and 

 renders it slightly alkaline. 



In the meantime the mold has secreted a chemical ferment, 

 an enzyme, which has the power of digesting the curd. As fast 

 as the acidity of the curd is reduced and the enzyme secreted, 

 the latter acts upon the curd, changing it from a hard con- 

 sistency to a soft texture. This softening begins over the whole 

 of the cheese, immediately underneath the mold on the surface, 

 and extends its way toward the center. At first, the cheese 

 is a hard, solid curd from surface to center, but as this enzyme 

 acts beneath the mold there is seen a thin layer of softened 

 material. This laye^r grows deeper and deeper as it encroaches 

 upon the curd. The enzyme produces a profound change in 

 the casein, converting it first into peptones and similar bodies; 

 later, these break down into still simpler bodies, or "end 

 products," among which ammonia may always be detected. 

 These latter end products give the flavor, and appear to be 

 produced by bacteria rather than by the action of the enzymes 

 secreted by the mold. During the ripening the cheese will be 

 found to have a core of a sour, acid curd in the center, sur- 

 rounded by a layer of soft, digested material. (Fig. 65.) The 

 cheese ripens thus from the surface inward and is not com- 

 pletely ripened until the soft-layer reaches the center. One of 

 the difficulties in making a satisfactory cheese is to have the 

 ripening reach the center so as to ripen the cheese com- 

 pletely before it becomes too soft at the outer edge over- 

 ripe. The degree of softness varies greatly. Sometimes the 

 cheese becomes so soft that it will run out like cream when the 

 cheese is cut, a condition that is prized by some connoisseurs. 

 More commonly it is of a waxy or soft, buttery texture, not 

 soft enough to "run." The waxy brands are less highly flavored 

 and in general more popular. 



!Maze. Rev. Gen. d'Lait, iv., p. 472, 1905. 



