250 THE BOOK 'OF CHEESE 



Paracasein (formed by the action of the rennet on the 

 casein). Insoluble in brine and warm 5 per cent salt brine. 



Protein. Soluble in warm 5 per cent salt brine. 



Protein. Insoluble in warm salt brine or water. 



Paranuclein. A protein soluble in water and precipi- 

 table by dilute hydrochloric acid. 



Caseoses and proteases. Protein derivations soluble in 

 water and not coagulated by heat. 



Peptones. Protein derivations simpler than the pro- 

 teoses, soluble in water and not coagulated by heat. 



Amido acids. Protein derivations soluble in water, 

 least complex except ammonia. 



Ammonia. The simplest protein derivations. 



From the discussion of the constituents in the milk 

 and cheese, it is evident that practically all the prin- 

 cipal ripening changes are concerned with those taking 

 place in the proteins. 



236. Causes of ripening changes. Authorities dis- 

 agree as to the exact agents which cause the ripening 

 changes. Some think they are due to the action of the 

 enzymes in the rennet and those secreted in the milk. 

 Others hold that these changes are due entirely to 

 bacterial action. A combination of the two seems prob- 

 able. The action of the rennet extract renders the 

 casein insoluble and in the ripening process the pro- 

 teins become soluble, the degree depending on the length 

 of time the cheese is ripened. The amount of water- 

 soluble proteins and protein derivatives is used as a meas- 

 ure of the extent of cheese ripening, considered from a 

 chemical standpoint. 



237. Action of the rennet extract. Some authorities 

 hold that rennet extract contains two enzymes, rennin 

 and pepsin, while others think it is a single peptic fer- 



