No. 6. DEPARTMENT OP AGRICULTURE. 616 



apart, additional fat is lost. Therefore, as soon as the curd is cut, 

 the whole mass is kept in gentle motion bj careful haod-stirring 

 or with a wire basket made for the purpose. Care must be taken 

 to avoid anj rough treatment that would crush or break the curd 

 particles, the object of the agitation being simply to keep the par- 

 ticles of curd moving through the whey and thus preventing their 

 settling and matting. Pains must be taken to keep the curd from 

 settling in the corners of the vat or attaching itself to the sides, 

 since, if left in such places, it will be heated too high later. The 

 whey should appear clear and be fairly free from small particles 

 of floating curd. The curd contracts and hardens during this stir- 

 ring, but the shrinking takes place more quickly upon the outer sur- 

 face of the curd particles than upon the inside. This hardening 

 of the out surface prevents the curd particles from sticking together 

 so readily, but offers some opposition to the further rapid escape of 

 whey. In order to favor the continuous expulsico of whey, heat is 

 used at this stage. The term "cooking" is commonly applied to this 

 part of the operation, but the word is misleading, since we use 

 only a gentle heat and in no sense '^cook" the curd. The object 

 of heating is to favor the contraction of the curd and the escape of 

 whey. The cause of the shrinking of curd is probably due to unioa 

 of lactic acid with the paracasein, forming a new compound which 

 has the property of contracting. The heat favors the formation of 

 this new substance, and the more rapidly it forms the more readily 

 the curd shrinks and forces out the whey. Heat is applied gradu- 

 ally and the stirring is kept up constantly. Under normal condi- 

 tions ,the heat is applied so as to raise the tempertaure of the curd 

 and whey about one degree in five minutes, and rarely more than 

 two degrees in five minutes. The heating should be somewhat slower 

 up to 90 degrees F. than above that poiiit, since the shrinking of 

 curd takes place less rapidly below than above 90 degrees F. The 

 contents of the vat should be heated finallv to 98 degrees F. As the 

 the temperature is increased, the curd jjarticles become less tender, 

 and toward the end of the heating they can be stirred much more 

 vigorously without risk of injury. When the temperature of 98 

 degrees F. has been reached, the curd is allowed to settle to the 

 bottom of the vat and remain quiet with only an occasional stirring, 

 until a certain amount of acid has been formed or rather until a 

 certain amount of the comj)ound of lactic acid and paracasein has 

 been formed. 



55. Removing the Whey from the Curd. 



The whey should be removed from the curd when a certain amount 

 of lactic acid has* combined with the curd (paracasein) or, as the 

 cheese-maker commonly says, when there is '^enough acid on the 



