Fermentations of Milk. 107 



an agreeable odor. If the gas-forming bacteria are num*- 

 erous, the curd may even be spongy from the abundance 

 of gas holes, and the undesirable odor more pronounced. 

 Such curds are tough and rubbery. In some cases a bad 

 flavor or odor is apparent even though the texture of the 

 curd is not open and full of holes. The curd, the sur- 

 face of which is slimy indicates undesirable organisms, 

 A solid curd of agreeable odor is indicative of the pres- 

 ence of the desirable acid-forming bacteria. Such a milk 

 is excellent from the standpoint of the butter or cheese 

 maker, but may not be so desirable from the standpoint 

 of the milk dealer on account of its poor keeping qual- 

 ities. On the other hand a milk suitable from the stand- 

 point of the milk dealer, on account of its low germ con- 

 tent, and hence good keeping quality, may give a poor 

 curd test. It is certain to contain some bacteria, espe- 

 cially those from the interior of the udder while it may 

 contain none of the desirable acid-forming organisms 

 without which a curd of good texture and flavor can not 

 be obtained. The bacteria in the clean milk will grow 

 rapidly at the high temperatures at which the curds are 

 kept and the changes they will produce as to flavor and 

 odor may be undesirable. The milk might be judged 

 as poor when in reality it might be a most excellent sam- 

 ple, and if kept at the ordinary storage temperatures, it 

 might keep for days. The test when used for market 

 milk should be interpreted with this in mind. 



If the results are to be of any value, the test must be 

 made with care to avoid all sources of error; the tester 

 must know that the bacteria causing the gas and bad fla- 

 vors in the sample were originally present in the milk at 

 the time the sample was taken, and that they have not 

 come from the containers used or from other sources. 



