UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 944 



&J&r^LrL 



Contribution from the Bureau of Animal Industry 

 JOHN R. MOHLER, Chief 



jf^"^BU-fc, 



Washington, D. C. 



May 12, 1921 



THE ALCOHOL TEST AS A MEANS OF DETERMIN- 

 ING QUALITY OF MILK FOR CONDENSERIES. 



By A. O. Dahlbeeg and H. S. Garner, Research Laboratories, Dairy Division. 



CONTENTS. 



Page. 



Review of previous work 1 



Test methods used 2 



Experiments at Grove City creamery- 4 

 Comparison of acidity and alcohol 



tests of milk for condensing 4 



Relative value of acidity and alco- 

 hol tests 8 



Experiments at condenseries 9 



Work at Factory A 9 



Work at Factory B 11 



Conclusions 13 



List of references 13 



REVIEW OF PREVIOUS WORK. 



The urgent necessity for some means of determining the quality 

 of milk received at condenseries and other dairy manufacturing 

 plants has resulted in the continued use of the acid test even after 

 its defects have become generally recognized. This test is based on 

 the assumption that a titratable acidity above the normal for fresh 

 milk indicates an increase in acidity due to bacterial action. 



It is well known, however, that a certain part of the alkali added 

 to milk to obtain an end point with any given indicator is combined 

 with constituents of the milk other than the acids. While this has 

 been recognized it has not been generally realized how great a varia- 

 tion in the apparent acidity may be due to this cause. It has been 

 recently pointed out by Rice (I) 1 that the casein and the phosphates 

 both combine with alkali and are subject to a sufficient variation to 

 cause in some instances an apparent high acidity in fresh milk. 



Our own experience, which is not unusual, has shown that not 

 infrequently milk rejected because of high acidity was fresh milk 

 in which bacterial action was highly improbable. In making evapo- 

 rated milk the most essential characteristic is the ability of the milk 



1 See list of references at end of bulletin. 



27179° — 21 



