174 Dairy Bacteriology. 



quickly, and the curd should be uniform and firm. If it 

 is soft or tender, and does not curdle within the usual 

 time (which will vary, of course, with the proportion of 

 rennet and milk used) it shows an abnormal condition, 

 due generally to the addition of water or chemical sub- 

 stances. Milk from cows advanced in lactation (strip- 

 pers) not infrequently reacts abnormally with the rennet 

 test. This test rests upon the chemical rather than the 

 "biological characteristics of the milk. 



182. Wisconsin curd test. The curd test in some 

 respects is a modification of the fermentation test, yet 

 the method is sufficiently different in detail to merit sep- 

 arate mention. As here outlined it originated at the 

 Wisconsin Dairy School in 1895, as an experimental 

 method of studying the influence of gas- generating bac- 

 teria in cheese-making 1 . 



In the curd test, a small pat of cheese is made in a 

 glass jar from each sample of milk. The advantage of 

 this method over the ordinary fermentation tests lies in 

 the fact that the samples of milk are treated in a way so 

 as to conform more closely to cheese conditions, inasmuch 

 as the whey is removed, thus permitting the ready recog- 

 nition of gas-production in the curd. Nearly all milks 

 contain some bacteria capable of decomposing the milk- 

 sugar and producing gas. In the curd test this slight 

 evidence does not appear, but if the milk contains an 

 abnormally high content of gas- generating bacteria, suf- 

 ficient to injure the quality of the milk for cheese-mak- 

 ing, then such a condition becomes evident when a curd 

 test is made. 



183. Improvised apparatus. A simple, inexpensive 

 apparatus can be readily made by any operator in the 



1 I2th Kept. Wis. Expt. Stat., p. 148, 1895. A full description of 

 this test is given in Bull. 67, Wis. Expt. Stat., June, 1898. 



