286 DAIRYING. 



The curds in this test are made under conditions most 

 favorable for developing in them any defects which may be 

 caused by the presence of undesirable bacteria that are 

 brought to the milk by dust, dirt, and other impurities. 



The odor of a curd should be noticed as soon as the cover 

 is taken from a jar. This is often sufficient to convince a 

 patron that the milk is tainted, and may suggest to him the 

 particular cause of the odor by its resemblance to some fa- 

 miliar smell that he recognizes and can remove. 



A solid firm curd shows that the milk is pure and clean 

 and has been properly handled. The rather firm curds 

 which show fine pin-holes when cut with a knife are indi- 

 cations of some of the worst impurities in milk, while the 

 spongy curds show the presence of bacteria which in some 

 cases have developed sufficient gas to float the curd. Per- 

 sons familiar with milk soon learn to use the evidence 

 obtained by this test to distinguish between good and bad 

 milk, and to convince the milk-producers of the value of the 

 test. (Dairy Bull., Wis. Exp. Station.) 



THE FER3IENTATION TEST. 



The Gerber fermentation test (modified by Monrad) fur- 

 nishes a convenient method for discovering tainted milk on 

 the farm or at the factory. The test consists of a tin tank 

 which can be heated by means of a small lamp, and into 

 which a rack fits holding a certain number of cylindrical 

 glass tubes ; these are all numbered and provided with a 

 mark and a tin cover. In making the test the tubes are 

 filled to the mark with milk, the number of each tube being 

 recorded in a notebook opposite the name of the particular 

 patron whose milk was placed therein. The tubes in the 

 rack are put in the tank, which is two thirds full of water ; 

 the temperature of the water is kept at 104-106° F. for six 

 hours, when the rack is taken out, the tubes gently shaken, 

 and the appearance of the milk, its odor, taste, etc., carefully 

 noted in each case. The tubes are then again heated in the 

 tank at the same temperature as before for another six 

 hours, when observations are once more taken of the ap- 



