CHAPTER VIII. 

 TESTING THE PURITY OF MILK. 



153. The Wisconsin curd test. Cheese makers are 

 often troubled with so-called floating or gassy curds 

 which produce cheese defective in flavor and texture. 

 These faults are usually caused by some particular lot 

 of milk containing impurities that cannot be detected 

 by ordinary means of inspection. The Wisconsin curd 

 test is used to detect the source of these defects and 

 thus enable the cheese maker to exclude the milk from 

 the particular farm or cow to which the trouble is 

 traced. This test is similar in principle to tests that 

 have long been in use in cheese-making districts in 

 Europe, notably in Switzerland, 1 but was worked out 

 independently at the Wisconsin Dairy School in 1895 

 and is now generally known as the ''Wisconsin Curd 

 Test." 2 



154. Method of making the test. Pint glass jars, 

 thoroughly cleaned and sterilized with live steam, are 

 provided; they are plainly numbered or tagged, one 

 jar being provided for each lot of milk to be tested. The 

 jars are filled about two-thirds full with milk from the 

 various sources; it is not necessary to take an exact 



1 Herz, Unters. d. Kuhmilch, Berlin, 1889, p. 87 ; Siats, Unters. landw. 

 wicht. Stoffe, 1903, p. 140. 



2 Wisconsin experiment station, twelfth report, p. 148. The appar- 

 atus used for the test was greatly improved in 1898, and a description 

 of the improved test is given in bulletin No. 67 and the annual report 

 of the StHtion for 181)8 (fifteenth report, pp. 47-53'), from which source 

 the accompanying illustration is taken (see fig. 46). 



