214 Milk Inspection. 



The alcohol test also curdles market milk which has become 

 spoiled (8 to 9 degrees of acidity). 



A positive reaction with fresh samples from individual cows 

 or with samples from separate quarters indicates either a physio- 

 logical or severe pathological inflammatory condition of the milk 

 glands. The milk is mixed with an equal amount of 68% alcohol. 



Recently, the alizarol test has been recommended for the de- 

 termination of spoiled milk. Milk mixed with an equal part of 

 alizarol becomes brownish violet, as long as it is fresh and not 

 spoiled ; otherwise the color turns brown and yellow, and the milk 

 curdles, with the formation of thick flakes. 



For the control of market milk or for the diagnosis of udder 

 diseases the author found that the alizarol test (milk with 68% 

 alcohol and as much alizarin as is soluble) is without any value in 

 testing samples of individual cows or quarters. 



The degree of acidity of the milk is established by titration 

 with standard alkali. 



1. According to Henkel-Soxhlet, with y normal sodium hy- 

 drate solution, fresh market milk has about 6.0 degree of acidity. 



2. According to Thorner and Pfeifer, with TO normal so- 

 dium hydrate solution in 10 c. c. of milk and 20 or 40 c. c. of water, 

 respectively, with 5 drops of a 2% solution of phenolphthalein 

 (the figures thus obtained are multiplied by 10) fresh milk has 

 about 18 degrees of acidity. 



According to Henkel-Soxhlet, the acidity is determined by 

 titrating 50 c. c. of milk, to which 2 c. c. of a 2% alcoholic solution 

 of phenolphthalein have been added, to a faint but permanent 

 pink. Each y 2 c. c. of alkali (i/4 normal sodium hydrate) corre- 

 sponds to a degree of acidity. 



Schern utilizes 10 c. c. of milk and titrates drop by drop with 

 1/40 normal sodium hydrate solution after having added 1 to 2 

 drops of the solution of phenolphthalein. The titration takes place 

 in a mixing cylinder which is so graduated that the difference of 

 the level of the fluid before and after the titration shows the degree 

 of acidity. 



An increased degree of acidity in market milk, for instance, 

 7 or more after the method of Henkel-Soxhlet, does not always 

 indicate a spoiled condition. This can only be presumed when the 

 increase of acidity in a certain time and at a certain temperature 

 is very rapid, in other words, when the curve of acidity is abrupt. 

 After 12 to 24 hours the degree of acidity is again determined. 

 Fresh milk, kept at 20 degrees C., shows from 10 to 15 to 20 de- 

 grees of acidity after 24 hours. Milk at the end of the incubation 

 period, before bacterial multiplication begins, has 25 to 30 degrees 

 of acidity, and old milk 30 to 40 degrees. The increase in degrees 

 of acidity between fresh milk and older milk is caused by the for- 

 mation of lactic acid. One c. c. of !/4 normal sodium hydrate 22 . 5 

 mg. lactic acid, and 1 c. c. of iV normal sodium hydrate=9 mg. 



