374 SCIENCE AND PRACTICE OF CHEESE-MAKING 



compounds as paranuclein, caseoses and peptones and 

 much smaller proportions of amino acids and little or 

 no ammonia. (3) Galactase is able to .perform chem- 

 ical work similar in character to that of rennet-pepsin, 

 but how much insoluble protein it can render soluble 

 in a given period of time, we do not know. (4) 

 None of the three agencies previously mentioned has 

 the power of forming ammonia, as found in normal 

 cheese-ripening. It, therefore, appears that bacteria 

 alone must be responsible for the production of am- 

 monia and of a large proportion of the amino acids. 



It is obvious that the process of cheese-ripening is 

 not as simple as was once believed, but, on the con- 

 trary, is exceedingly complex. We cannot say yet 

 just what part each agent plays nor to what extent 

 each is independent of, or dependent upon, the others. 

 For example, the digesting action of rennet is clearly 

 dependent upon acidity. Does the action of rennet 

 have anything to do with the changing of the in- 

 soluble curd into a brine-soluble substance and back 

 again into a substance insoluble in brine? Or are 

 these changes immediately dependent upon acid-form- 

 ing bacteria? Does the rennet have any digesting 

 effect until the brine-insoluble form of protein ap- 

 pears? What forms of cheese proteins can galactase 

 or other milk enzyms attack and under what condi- 

 tions of acidity, temperature, etc.? When do the 

 bacteria begin their work in rendering soluble the 

 insoluble cheese proteins? Or do they act only upon 

 the products formed by rennet or galactase? Is the 

 bacterial work confined to one specific micro-organism, 

 or is the work associative? 



We thus see that there are many details still un- 

 settled; but, in view of what we think we know now, 



