MILK SUPPLY 51 



should be kept in glass bottles, tightly corked. The bottle con- 

 taining the stock solution should be glass-stoppered. 



The Boiling Test. Inspection by Heating. The heating-to- 

 the boiling point of samples of suspicious milk furnishes a most 

 reliable means to determine the fitness of such milk for condens- 

 ing. In many instances milk may satisfactorily pass the other 

 tests and yet it may not be in condition to stand the heat to 

 which it will be subjected in the process. If it curdles, when 

 boiled, it is obviously unfit for use. This test shows more than 

 the acid test above. By its use the operator is able to detect 

 milk otherwise abnormal, such as milk containing colostrum, etc., 

 or the proteids of which are unstable for other reasons. 



Making the Test. The boiling test is simple and can be 

 manipulated rapidly. A sample of the questionable milk is taken 

 into a small dipper. The dipper is held up against a steam jet 

 turned down into the milk. Direct steam is turned into the 

 milk until it comes to a boil. If flakes or specks of curd cling 

 to the sides of the dipper, the milk is unfit for use. 



An alcohol lamp or gas burner on the platform may be used 

 for heating the sample. In this case a few cubic centimeters 

 of the milk are discharged with an ordinary pipette into an ordi- 

 nary test tube, such as are in common use in the chemical labo- 

 ratory and can be obtained from the drug store. The tube is 

 held over the flame and the milk comes to a boil in less than 

 a minute. If the milk is in good condition the sides of the glass 

 tube remain perfectly clear. If it curdles upon heating, the sides 

 of the tube show fine specks of the curd. The appearance of 

 these specks condemns the milk. 



In the case of milk intended for evaporated milk, the boiling 

 test is not sufficiently severe to reveal the fitness of the milk; 

 for the sterilizing process. For the reliable detection of unde- 

 sirable milk for this purpose, the use of t the pilot sterilizer or test 

 sterilizer is recommended. Suspicious samples of milk are filled 

 into tins, the tins are sealed and placed into the pilot sterilizer 

 where they are given the same process of sterilization as is 

 used for the finished product. Milk that withstands this sterili- 

 zation can be depended upon to also pass safely through the 

 process of manufacture. Milk that curdles in this test steriliza- 



