CHAPTER V. 



CHEESE AND CHEESE-MAKING. 



107. The Coagulation of Milk and the Properties of the Coagulum. 

 The object of the manufacture of cheese is the utilization of the 

 caseous matter of milk. This is effected by coagulating the milk, 

 by precipitating the caseous matter in it by suitable reagents, and 

 by making the coagulated material, which represents the raw cheesy 

 matter, and which encloses all the remaining constituents of the 

 milk in varying quantities, into cheese, and by ripening fresh cheese 

 in order to render it suitable for consumption. From a very remote 

 period, it has been the custom to separate the solids of milk by 

 allowing it to sour spontaneously, or by treating it with rennet. 

 The coagulum obtained by spontaneous souring and that obtained 

 by the use of rennet were formerly regarded as identical. In the 

 years 1870 to 1875, through the labours of Schmidt and Kapeller, 

 and more especially through the accurate researches of Hammar- 

 sten, which have been already described in 5, it was proved 

 that the coagulums respectively obtained by these two different 

 methods differed from one another. The chemical difference consists 

 in the fact that the coagulum obtained by souring contains nothing 

 but casein, whereas that obtained by rennet contains paracasein, a 

 decomposition product of casein. For that reason a distinction must 

 be made between sour-milk cheese and rennet cheese, and this all 

 the more because both kinds of coagulum have been proved to 

 manifest many other very important differences in their properties. 

 For the sake of simplicity we will call the acid precipitate curd, and 

 the rennet precipitate coagulum or raw cheese. As far as the 

 manufacture of cheese is concerned, the latter is more important and 

 valuable than the former. 



The fresh coagulum obtained at a temperature of 30 to 35 C. is 

 an elastic substance, scarcely soluble in water, and not in the slightest 

 degree sticky or greasy. When properly prepared, it contains a 

 large number of different kinds of spores, but no luxuriantly grow- 

 ing vegetative forms of bacteria or fission spores. It is admirably 

 suited for the manufacture of a large number of different kinds of 



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