EXPERIMENT STATION REPORTS. 159 



The research work on the ''Keeping quaUties of butter," was continued 

 along the hne of the work done last j^ear. At the October meeting of the 

 Lansing section of the Society of American Bacteriologists, a paper was read 

 on the subject, ''Metallic flavor in dairy products with special reference to 

 butter". The following is an abstract of this paper, which appeared in the 

 March, 1921, issue of "Abstracts of Bacteriology": 



Experiments were conducted in which iron lactate and copper lactate at the 

 rate of 200 parts per million were added to cream that was made into experi- 

 mental butters. The latter were studied both when fresh and after a period 

 of cold storage. It was found that both salts were capable of producing the 

 flavor in fresh butter. In storage butter the metallic flavor was followed by 

 tallowiness and fishy flavor in the case of the addition of copper lactate, and 

 of indefinite off flavors in the case of iron lactate. 



Two bacteria of the B. suhtilis group, one isolated from metallic flavored 

 butter and the other from a sample of bitter milk, when inoculated into the 

 cream which was then made into butter, produced the flavor very faintly 

 when the butter was fresh, but after varying periods of storage produced the 

 flavor to a notable degree. 



Other members of the B. subtilis group Avhen inoculated into fresh milk, 

 produced the flavor in 24 to 72 hours when the milk was held in an ice box. 

 The rapidity of development of the flavor seemed to be correlated with the 

 abihty of the microorganisms to produce peptonization of litmus milk when 

 held at 37° C. The members of the B. subtilis group which were found to 

 produce metallic flavor were (1) B. mycoides; (2) B. megatherium; (3) B. 

 vulgatus, {mesentericus vulgatus); (4) B. ramosiis; (5) B. subtilis (laboratory 

 strain) and (6) B. subtilis (American museum of natural history strain)., A 

 control tube was not metallic but the addition of Difco 'peptone' resulted in a 

 flavor very similar to metallic. 



Further experiments are in progress and will be reported fully later. 

 . Since the above abstract was written it has been discovered that one of the 

 bacteria referred to in the paragraph beginning 'Two bacteria of B. subtilis 

 group', etc., is not a member of the B. subtilis group, but is probably B. fluor- 

 escois liquefadens. This is the organism which was isolated from bitter milk, 

 reported two years ago. (See Ann. Report Bact., 1919). A more rigid 

 examination of the above mentioned organisms may result in a revision of 

 names. 



A summar}^ of the same data appeared also on page 103 in the February, 

 1921 issue of the Experiment Station Quarterl.y under the title of "Off-flavors 

 in Butter". A fuller account of these investigations is being prepared for 

 presentation to a suitable journal. 



It is planned to continue this work and other similar work as soon as suffic- 

 ient funds are available to support it. In the meantime a study is being made 

 of the microflora of off -flavored butters, with the view to comparing their 

 floras AAath those of good flavored butters. In this way it is hoped to lay the 

 foundation for future work in this field. 



I suggest that it would be well to ask the Chemistry section to cooperate 

 with us on this problem, even to the extent of becoming jointly responsible 

 for the project (Adams lb) . I find it impracticable to do the necessary chemi- 

 cal work myself. At the present time it is desirable to determine whether 

 certain off-flavored butters have appreciable amounts of iron, copper, lead or 

 zinc salts present and, if so, to what extent. Some of the work which I have 

 done, and work done at other places, suggests that these salts are the exciting 

 cause of certain off-flavors, notably metallic p.nd tallowy flavors. A large 



