210 MILK 



Albtjmin Test for Heated Milk 



When milk is heated to 65.6° C. albumin begins to be coagu- 

 lated. At this temperature the amount is small, but at higher 

 temperature the amount of coagulated albumin is considerable. 

 If the casein is precipitated by acetic acid and the clear filtrate 

 boiled, albumin is precipitated. In the boiled filtrate from milk 

 heated above 65.6° C. the amount of precipitated albumin is less 

 than in that from raw milk. If the milk has been heated to 

 much higher temperatures the albumin is completely coagulated, 

 and therefore the filtrate from the acetic acid precipitate yields 

 no precipitate after boiling. 



Chemical Tests to Distinguish Human Milk from Cow's Milk 



1. Human milk mixed with ammonia and kept at room tem- 

 perature turns reddish violet; the larger the amount of ammonia 

 added, the more intense the color. Cow's milk produces no such 

 color with ammonia. 



2. When equal amounts of human rnili and a 1 per cent, solu- 

 tion of silver nitrate are heated to boiling a brown color develops 

 which has a touch of violet in it. Cow's milk with silver nitrate 

 solution develops no color or, at best, a very faint one. 



3. A 1 per cent, solution of neutral red in physiologic salt 

 solution produces a red color in cow's milk and a yellow color in 

 human milk. A few drops of the solution added to several cubic 

 centimeters of milk will produce this reaction. 



Fermentation Tests 



Fermentation tests are designed to enable the cheese maker 

 to judge the condition of the milk that is to be used for cheese 

 making. Undesirable bacteria sometimes are present in large 

 numbers, and their early detection may prevent financial loss. 

 When the curd is abnormal it becomes expedient to trace the 

 trouble to its origin. It may be that a single cow in the herd is 

 responsible for a contaminated milk. By testing the milk from 

 each cow the real source of the abnormal milk can be found, and 

 the milk can be excluded until it appears to be normal again. 



In countries where cheese is made on a large scale, Switzer- 

 land for example, tests for the purpose of detecting abnormal curds 

 have been practised for some time. These tests consist in curdling 

 a small portion of milk and examining the curds. The test known 

 as the Wisconsin curd test was worked out in the Wisconsin Agri- 

 cultural Experiment Station, and is carried out as follows: Pint 

 jars provided with covers are sterilized in live steam and filled 

 to two-thirds their capacity with the milk samples to be tested. 



