THE ALCOHOL TEST IIST EELATION TO MILK. 7 



cow might reveal some pathological condition, or there might be 

 some physiological reason for a slight variation in the composition 

 of the milk. If the test were performed on the milk from a few cows 

 a positive reaction might be caused, as Auzinger (3) believes, by the 

 mixing of milk which is changed by physiological or pathological 

 conditions with milk from normal cows. If there were a large per- 

 centage of abnormal milk which gave an alcohol test with a coagula- 

 tion with large flakes, the mixed milk might show a positive alcohol 

 test in which the coagulation would be in the form of small flakes. 

 When mixed milk from a large number of sources gives a positive 

 alcohol test it must be interpreted in an entirely different manner, 

 and this leads us to another phase of the subject. 



THE ALCOHOL TEST IN RELATION TO MARKET MILK. 



Since 1900 a considerable number of papers have appeared on the 

 use of the alcohol test in its relation to market milk. According to 

 Kirchner (15), Morres in 1905 showed that the alcohol test was of 

 value for determining the keeping quality of milk and indicating its 

 acidity. Reiss (26) in 1906 pointed out the practical value of the 

 test, and Morres (18) again in 1909 showed the value of the alcohol 

 test as a means of determining the keeping quality of milk. He added 

 2 c.c. of milk to 2 c.c. of 68 per cent (by volume) alcohol, and states 

 that if the milk coagulates with alcohol then decomposition has 

 already started and the extent is shown by the size of the flakes. 

 If the precipitate is in fine flakes then the acidity corresponds to 

 4 degrees Soxhlet; however, the coagulation may not be due to an 

 increase in acidity, but may be due to the action of rennet-forming 

 bacteria. In later work Morres has combined the alcohol and 

 alizarin tests. This will be discussed later. Morres considers that 

 the coagulation of mixed market milk is due largely to the formation 

 of acid or the action of rennet-forming bacteria- or to a combination 

 of both. Henkel (12) concludes from his work that the alcohol test 

 does not afford a proper means for determining acidity, but that the 

 value of the test lies in the fact that it gives a knowledge of the souring 

 and other changes in the properties of milk or in variations from the 

 normal properties which the acid test does not show. Other investi- 

 gators believe that the alcohol test is of value only as a preliminary 

 test. Fendler and Borkel (10) after a large number of tests to 

 determine the relation of the acidity of milk to the alcohol test con- 

 cluded that the double test with 70 per cent alcohol was not a proper 

 criterion for the freshness of market milk, including infants' milk 

 and superior grades of milk. They state that the double test using 

 50 per cent alcohol is suitable as a preliminary test for food in- 

 spectors, but the milk should be submitted to further tests. These 

 authors also found that no consistent relation existed between the 



