2'6S ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



but no reliable method has heretofore been available, and experiments 

 are being conducted by the Dairy Division with a view to arriving 

 at such a method. The experiments so far show that such butter 

 contains an excess of calcium, although butter in which a large 

 amount of inferior salt is used shows a similar excess of calcium. 

 Howevei'. the magnesium content of butter is increased by the use of 

 lime, and not by the use of salt. It is hoped, therefore, to establish 

 a ratio of magnesium to calcium for normal butter, and thereby make 

 possible the identification of butter from neutralized cream. 



A common defect in butter is a peculiar flavor known to butter 

 judges as " metallic flavor," which is supposed to be the product of such 

 metals as iron and copper. Investigations regarding this matter are 

 now under way. 



An experiment is being made whereby it is sought to volatilize and 

 condense a suflicient quantity of the flavoring matter in butter so that 

 it may be identified. If this can be done it wnll help to determine 

 the changes that take place in butter and the factors causing them. 

 Most of this work so far has been on apparatus and methods. 



A large number of cultures of lactic-acid-forming bacteria have 

 been collected from various sources, and a study has been made of 

 their cultural characteristics and their ability to ferment different 

 compounds. It was found that while no distinct differentiation could 

 be obtained by means of ordinary cultural characteristics, the fermen- 

 tation of various test substances could be so coordinated that the 

 group could be separated into several distinct varieties. While the 

 work Avill be continued, a part of it is now ready for publication. 



A ver}^ large amount of the farm butter now made is very inferior 

 and sells for a greatl}^ reduced price. Studies are being made by 

 which it is sought to determine the causes of the serious defects in 

 farm butter. The work done so far has been largely of a preliminary 

 character. Sam2:)les of butter made in various sections of the country 

 have been examined, and the methods used on a few of the best farms 

 in Vermont are now being studied. 



In maintaining an efficient inspection of the renovated butter fac- 

 tories and their products, more information relative to renovated 

 butter, the packing stock used in making it, etc., is badly needed. A 

 laboratory is therefore being equipped in which a miniature renovat- 

 ing plant w^ill be installed and the various problems taken up. Only 

 preliminary work has been done so far. 



Neutral lard is doubtless used to adulterate butter, particularly 

 renovated butter. So far no reliable method is available for determin- 

 ing its presence in butter unless it is there in large quantities. A 

 study of this problem is now under way, but the w^ork has not pro- 

 gressed far enough to w\Trrant positive conclusions. 



MILK INVESTIGATIONS. 



An extensive study has been made of the bacteriology of commer- 

 cially pasteurized and raw market milk, the milk used being pur- 

 chased in Washington, New York, and Boston. All of the commer- 

 cially pasteurized milk soured normally, due in part at least to the 

 wide distribution of a strain of lactic-acid bacteria possessing excep- 

 tional resistance to heat. All changes due to bacteria are delayed 

 in pasteurized milk for a period depending on the original bac- 



