64 THE BOOK OF CHEESE 



patron is too ripe to be received. The acidity of other 

 materials, such as whey and starter, can be determined 

 as well as that of milk. The disadvantages are that it 

 is difficult to get the alkali solution of the proper strength 

 and the solution is liable to deteriorate on standing. It 

 requires a careful exact operator to make the test. 



The advantages of the rennet test are that it is easy to 

 make, and it requires no materials that are hard to re- 

 place. The disadvantage is that the milk must be 

 warmed to the same temperature before a comparative 

 test can be made. The size of the outlet in cups varies. 

 It does not indicate the percentage of acid present in the 

 milk. It is simply a comparative test. To obtain the 

 best result, both tests should be used in conjunction. 



85. Control of acid. The control of acidity in curd and 

 cheese is dependent on the control of the moisture or 

 water-content. The control of both factors is very impor- 

 tant in relation to the quality 1 of the cheese. Often acio> 

 ity is spoken of when moisture is really intended, and 

 vice versa. The close relation between the moisture and 

 acidity is due to the presence of the milk-sugar in solution 

 in the milk-serum which becomes the whey of cheese- 

 making. Water or moisture in cheese consists of the 

 remnant of this whey which is not expelled in the making 

 process. During manufacture and the ripening process, 

 the milk-sugar is changed to lactic acid. A cheese may 

 be sweet when first made and after a time become sour 

 because it contains too much moisture in the form of 

 whey. Excess of whey carries excess of milk-sugar 

 from which fermentation produces intense acidity. 



1 Doane, C. F., The influence of lactic acid on the quality of 

 cheese of the Cheddar type, U. S. Dept. Agr. Bur. An. Ind. Bui. 

 123, pages 1-20, 1910. 



