192 THE BOOK OF CHEESE 



from 0.16 to 0.18 of 1 per cent, but no definite statement 

 can be given for the rennet test. This can be determined 

 only by comparison from day to day. For opera- 

 tion of rennet test see Chapter V. During this period 

 of two and one-half hours, the curd is formed, then cut, 

 and the temperature is raised from 84 or 86 F. (the 

 temperature at which the rennet extract is added) to about 

 98 to 100 F. The curd must be kept agitated so that 

 the particles will not mat together; this is necessary to 

 obtain sufficient contraction of the particles of curd with 

 the proper reduction of water-content. If the milk 

 becomes too ripe (too sour) before the rennet is added, 

 there will not be sufficient time for these steps to take 

 place naturally. In such cases special means are re- 

 quired to firm the curd. These result in a loss of both 

 quality and quantity of cheese. On the other hand, if 

 the milk is not ripened, but the rennet extract added, 

 regardless of the acid development, one of the important 

 natural forces for expelling the moisture is lost. The 

 time required for the particles of curd to contract is much 

 prolonged, the expulsion of whey is usually inadequate and 

 the curd remains in a soft or wet condition. Using too 

 much starter is almost equally bad, for although it hastens 

 the making process, it produces a sour or acid cheese. 



195. Setting or coagulating. The milk for Cheddar 

 cheese-making is heated to 86 to 88 F. or occasionally 

 a slightly lower temperature. This temperature is found 

 by experiment to give the texture of curd most favorable 

 for the desired results. Although some cheese-makers 

 work as low as 84 F., the texture of such curd is too soft 

 and coagulates too slowly. The very slight change of 

 2F. produces curd which coagulates more quickly and 

 is tougher and firmer. 



