360 



MICROBIOLOGY OF MILK AND MILK PRODUCTS. 



they are evenly distributed throughout the mass of the cheese except 

 near, the surface. 



The cheese is made from as fresh milk as it is possible to secure. 

 The rennet used is prepared by placing a piece of the dried rennet in 

 whey and incubating the same for twenty-four to thirty-six hours at 30. 

 This is employed in place of the commercial extract used by the Cheddar 

 maker. It serves not only to curdle the milk, but adds to it a large 

 number of acid-forming bacteria that have grown in the rennet solution 

 during the period of incubation. The number is not, however, sufficient 

 to cause any development of acid during the making process which 

 differs from the preparation of Cheddar cheese in the method of firming 



* * 



FIG. 84. Typical development of "eyes" in Swiss cheese. (Original.) 



the curd. This is accomplished by heating the curd to 52 to 60, and by 

 cutting it into pieces scarcely larger than grains of wheat. The salt is 

 applied to the exterior of the cheese by immersion in brine for one to four 

 days and by sprinkling salt on the surface. 



The fermentation of the lactose proceeds rapidly during the pressing 

 and subsequent thereto, so that within a few days the sugar has disap- 

 peared. The lack of the development of acid during the making probably 

 results in a somewhat different relation between the acid and protein 

 from that existing in a Cheddar cheese, which, together with the absence 

 of salt gives a somewhat different environment, thus making possible 

 the development of a different flora. There is no ground for believing 

 that the agents concerned in the proteolytic changes are other than those 

 that function in Cheddar cheese. The flavor must, however, be due to 

 other factors; this is indicated by the fact that if the milk is ripened as in 

 the Cheddar process, or if salt is added to the curd the flavor will approxi- 



