528 BUTTER DEFECTS 



more butter on the open shelves of their stores than they may rea- 

 sonably expect to dispose of each day, or preferably to reserve a 

 compartment in their refrigerator for all the butter they carry in 

 stock. 



Tig. 83. Unsaltecl butter held at room temperature for 

 3O days, showing- d.eep yellow border at periphery 

 due to evaporation of moisture, while interior retained 

 its original color; moisture in surface layer was 1 

 per cent, in interior 16 per cent. 



Green Spots in Butter. Green spots occasionally appear on 

 the surface or in the interior of butter, other than those described 

 under "moldy butter." This green coloration, especially when found 

 on the surface, usually shows up in the form of small circles or 

 rings, which grow larger with age. 



Microchemical examination of these green spots by Hunziker 

 and Hosman 1 showed these spots to contain traces of copper. When 

 they appear on the surface of print butter they can generally be 

 traced to the presence in the parchment wrapper of very minute 

 specks with metallic lustre. These specks in the wrapper have been 

 found, by the authors, to consist of copper or an alloy containing 

 copper, such as German silver, or brass. 



Further investigation has revealed that the parchment paper 

 manufacturers are experiencing considerable difficulties to keep 



1 Hunziker ahd Hosman, Blue Valley Research Laboratory, 1917-1919. Re- 

 sults not published. 



