38 THE BOOK OF CHEESE 



paracasein molecule being one-half of the casein mole- 

 cule. Moreover, Bosworth (1913) has shown that, if the 

 rennin cleavage be carried out under conditions which 

 avoid autohydrolysis, no other protein is formed ; also 

 that, if the calcium caseinate present be one containing 

 four equivalents of calcium, the paracaseinate does not 

 precipitate, save in the presence of a soluble calcium 

 salt, while, if the calcium caseinate be one of two equiva- 

 lents of base, rennin does cause immediate coagulation. 

 Bosworth concludes that the rennin action is a cleavage 

 (probably hydrolytic) of a molecule of caseinate into two 

 molecules of paracaseinate, the coagulation being a 

 secondary effect due to a change in solubilities, dicalcium 

 paracaseinate being soluble in pure water but not in water 

 containing more than a trace of calcium salt, and the mono- 

 calcium caseinate being insoluble in water. The alkali 

 paracaseinates, as well as casemates, are soluble. This 

 explanation seems to promise to harmonize the observa- 

 tions with regard to acidity and the effects of the presence 

 of soluble salts. This theory represents, therefore, many 

 years of continuous work at the New York Experiment 

 Station centered primarily on American Cheddar cheese. 

 Disputed points remain for further study but these 

 workers have contributed much toward a clear descrip- 

 tion of the chemical constitution of casein as affected by 

 rennet action and bacterial activity. 



The investigations of these authors and of Hart with 

 regard to the changes which the paracasein, the calcium 

 and the phosphorus undergo during the ripening of cheese 

 (Van Slyke and Hart, 1902, 1905 ; Van Slyke and Bos- 

 worth, 1907, 1913; Bosworth, 1907) contributed to this 

 interpretation. 



