202 SCIENCE AND PRACTICE OF DAIRYING. 



fermentation, and that it is directly caused by ferments. Hammarsten has 

 carried out the most elaborate and trustworthy researches on this subject. 

 If we take a solution of caseous matter prepared according to his directions, 

 and precipitate or coagulate it with rennet, and then perfectly separate the 

 whey, obtained by steaming and the careful addition of acetic acid, from 

 the small quantity of rennet coagulum which is still present, and then 

 filter from the filtrate, we can separate out by means of alcohol, tannic acid, 

 or Millon's reagent, a protein body, which, in its chemical behaviour, 

 differs essentially from albumin and casein, and which is also free from 

 bodies of the nuclein type. Hammarsten names this body whey-protein, 

 and suggests with regard to the nature of rennet coagulation the following 

 theory: The rennet ferment acts, within certain definite temperatures, 

 directly on the casein, and decomposes it, by means of hydration, into two 

 new albuminoids, in which the one, the whey-protein, remains in solution, 

 but the other, in the event of soluble lime salts being present, is precipi- 

 tated as a coagulum. Schulze, of Zurich, suggests that the albuminoid 

 bodies which Hammarsten designates by the term cheese, a term which 

 admits of different meanings, should rather be designated by the term 

 paracasein. Soldner has shown that Hammarsten's statement, that the 

 rennet coagulation only takes place in the presence of dissolved calcium 

 phosphate, is so far incorrect, and it has been already shown that it does 

 not depend on the presence of soluble calcium phosphate, but chiefly on 

 the presence of soluble lime salts. 



According to Hammarsten's own researches, or those carried out under 

 his supervision, casein, paracasein, aud whey-protein have been shown to 

 contain the following quantities of carbon, oxygen, and nitrogen : 



Casein. Paracasein. Whey-protein 



Carbon, 52-96 52-88 50-33 



Oxygen, 7'05 7 '00 7 '00 



Nitrogen, 15-65 15-84 13-25 



As has already been mentioned, rennet coagulation has to be regarded 

 as a fermentation process. Fermentation processes are chemical processes 

 of a particular nature, in which organic bodies are decomposed into simpler 

 compounds by union with water. The characteristic of fermentation pro- 

 cesses consists in the fact that they can be induced by a particular fermen- 

 tation starter, an unorganized or organized ferment, and that for this purpose 

 a comparatively small quantity of ferment suffices; but the ferment does 

 not enter into a stable chemical combination either with the fermentable 

 body, or with the decomposition products formed. The progress of all 

 processes of fermentation is influenced to a large extent by the ferment, by 

 the percentage of water in the fermenting mass, and by the temperature 



