1 42 MILK [vin 



In cheese made from rennet-curd the ripening pro- 

 cess goes on throughout the whole mass. Further- 

 more in rennet-curd the calcium phosphates which 

 are in suspension in the milk are entirely enclosed 

 in it, whereas acid-curd, it will be found, only en- 

 closes a small quantity of these phosphates, and this 

 for the reason that most of them are dissolved by 

 the lactic acid. Lastly, acid-curd contains more fat 

 than rennet-curd. 



Nature of Action of Rennet. Now, if we ex- 

 amine into the nature of the rennet coagulation we 

 shall find first of all, as Hammarsten found in his re- 

 searches, that it is entirely independent of the forma- 

 tion of an acid in the milk, and that the reaction of the 

 curd is not changed during the curdling. Although 

 the curd does, as a rule, exhibit an acid reaction, this 

 is due to the action of micro-organisms. Hammarsten, 

 secondly, proved that the action of rennet is entirely 

 independent of milk - sugar. This he proved by 

 curdling solutions of casein, which had been entirely 

 freed from sugar, with rennet. Now these two 

 points alone are sufficient to distinguish the acid 

 coagulation of milk from the rennet coagulation ; for 

 it is known that the acid coagulation of milk, as 

 effected in milk which is allowed to spontaneously 

 coagulate, is due to the action of true or living fer- 

 ments, to which the name lactic ferments has been 

 applied, which act upon the milk-sugar, decomposing 



