38G EXPERIMENT STATION RECORD. 



The testing of milk by its taste and odor, the detection of foreign 

 matter by allowing a sample to stand in a glass jar and observing the 

 amount of sediment, and testing the acidity by Farrington's alkaline 

 tablets (E. S. E., 0, p. 83; 8, p. 933) are discussed, as are also the use of 

 the rennet test, the detection of antiseptics, and fermentation tests. 

 Gerber's fermentation test, as a means of determining approximately 

 the quality of milk, is described. The more important feature of the 

 bulletin is the description of the Wisconsin curd test, which originated 

 at the Wisconsin Dairy School in 1895. An illustrated description of 

 this test and the method of conducting it and interpreting the results 

 are given. 



To make the test a fruit jar is filled half full of milk and set in a 

 tub about half full of water sufficiently warm to raise the temperature 

 of the milk to 98° F. When this temperature is reached 10 drops of 

 rennet extract is added to the milk and the jar left undisturbed until 

 the milk is curdled, when the curd is broken into small pieces by stir- 

 ring with a case knife. The whey is poured off as soon as the curd 

 settles, and this process is repeated at frequent intervals until the curd 

 mats into a solid mass. The temperature of the surrounding water 

 should be maintained from 6 to 8 hours, to favor the rapid development 

 of the organisms in the curd. 



"If the milk contains no deleterious bacteria, the curd when cut will present a 

 firm, even texture. If gas-producing bacteria are, present the texture of the curd 

 will be more spongy, the cut surface showing a number of holes varying in size, 

 depending upon the prevalence and gas-producing ability of the uudesirable bac- 

 teria. . . . The conditions under which the curd test is conducted accelerate the 

 fermentative action, so that a milk that might show no symptoms of gas formation 

 until the cheese was on the shelf would bo detected when subjected to the curd 

 test. Milks that are sufficiently contaminated to produce floating curds will show 

 a very spongy texture in the test in a few hours. No hard and fast rules can be 

 given for the interpretation of the results of the curd test, but an ordinary opera- 

 tor will very quickly learn to discriminate between milks that should and should 

 not be accepted. ... It is also possible that taints may be produced by bacterial 

 decomposition in cases where no gas is formed. This is particularly true with that 

 class of organisms that act upon the albumen and casein instead of the milk sugar. 

 Those bacteria that find their way into the milk through the introduction of lilth 

 and dust are particularly prone to produce this change, and this type of fermenta- 

 tion is very often found during the summer months. In the curd tests such milks 

 are not condemned upon the texture of the curd, but upon the odor, which is more or 

 less pronounced when the bottle is opened." 



Besides the improvised apparatus for making the test an improved 

 apparatus is described, consisting of a water box with a close-fitting 

 cover which permits the retention of the desired temperature for a 

 longer time, racks for holding the bottles, and bottles better suited to 

 the purpose of the test thau ordinary fruit jars. Such apparatus can 

 now be obtained of some of the dairy supply houses. 



In conclusion, several illustrations are given of the favorable results 

 which have followed the use of the curd test in cheese factories. 

 In one case where the cheese maker was troubled with tainted milk 



