THE APPLICATION OF RENNET IN PRACTICE. 211 



the firmer the coagulum becomes. The firmness of the coagulum 

 depends, in the first instance, on the strength of the rennet used, 

 on the length of the coagulation period, and on the temperature 

 during coagulation. The percentage of water in the coagulum is in 

 inverse proportion to its firmness. Experience has shown that 

 the coagulum, of each of the many different kinds of rennet cheeses, 

 requires a certain definite percentage of water, and a certain definite 

 firmness. Since these two things are unalterably determined by the 

 nature and method in which the separation of the milk is effected, 

 and since that depends on slight delicate differences, the coagulation 

 of milk by means of rennet demands the greatest attention and 

 care. This is all the more the case, as the firmness and the per- 

 centage of water of the coagulum is not merely dependent on the 

 period of coagulation, and the temperature and the quantity of 

 rennet used, but is also dependent on the percentage of the fat, and 

 the acidity of the milk. In the manufacture of very soft cheeses, 

 the milk is separated at a temperature of from 20 to 28 C., and the 

 period of coagulation is at the same time lengthened. On the other 

 hand, if hard-keeping cheeses, suitable for keeping for a long time, 

 are to be prepared, the coagulation is effected at from 28 to 35 C., 

 and its duration is shortened. If coagulation take place very 

 slowly, that is to say, if it occupy about an hour or more, certain 

 dangers arise which have to be watched, and subsequently, if pos- 

 sible, have to be guarded against. The longer the coagulation period 

 the more difficult it is to keep the milk during the whole time at 

 an equable temperature. In the case of the manufacture of cheese 

 from whole -milk, this difficulty manifests itself in the collection 

 of the fat in the surface layers of the coagulum. Too short a 

 coagulation period can also give rise to undesirable results. The 

 coagulum, when formed too quickly, may become so firm that it is 

 impossible to work it in mass, and to break it up as finely as is 

 necessary. In the manufacture of the same kind of cheese, it is 

 necessary, in winter, to raise the coagulation temperature a little 

 above that maintained on an average. This is also necessary in the 

 case of milk which contains more than the average percentage of 

 fat, or which is relatively less acid. 



The object of all operations in the separation of milk is to obtain 

 a coagulum which is of a perfectly uniform nature. This has to be 

 kept in view in practice before everything else in coagulating with 

 rennet. 



