BUTTER DEFECTS 529 



filings of these metals out of their paper pulp and that, in order to 

 guard against their appearance in the paper, the manufacturers are 

 employing diverse devices, such as magnets, etc., in the process of 

 manufacture. 



The original source of these minute specks of metallic lustre 

 in the parchment paper lies in the rags which constitute a portion 

 of the raw material from which parchment paper is manufactured. 

 In spite of the manufacturers' efforts to eliminate them, metal but- 

 tons and buckles of discarded overalls and of similar rags occa- 

 sionally escape detection, pass into the process with the rags and 

 are thus ground into fine particles or filings which later appear in 

 the finished parchment paper. 



Whenever particles of these metal filings become incorporated 

 in the parchment wrapper and the butter is wrapped in such wrap- 

 pers, the salt and acid in the butter attack the copper contained in 

 these minute specks, forming verdigris. This in turn starts the 

 formation of a small green circle on the butter and on the wrapper, 

 where the metal speck is located. 



The green circle grows as the butter ages and the action con- 

 tinues. Around the green coloration there is often also white, 

 bleached butter with an intense tallowy odor. This oxidation, un- 

 der favorable conditions, may ultimately involve the entire print, 

 causing the whole package to be greenish white and tallowy. 



In other cases the green coloration may occur in the interior 

 of the butter. In this case it is also due to particles of copper or 

 an alloy containing copper, but the source of the copper lies in the 

 manufacturing process. It is especially prone to occur when the 

 strainer over the forewarmer or over the pasteurizing vat sags and 

 scrapes the revolving coil, or when accidentally a can cover or other 

 obstruction drops into the bottom of the forewarmer and becomes 

 wedged in between the forewarmer and the revolving coil. 



In such instances and other similar cases, particles of the copper 

 of the coil and possibly of the strainer are filed off into the cream 

 and are later worked into the butter. The metal particles may be 

 very small and hardly perceptible to the naked eye, but their corro- 

 sion by the salt and acid of the butter is inevitable, causing the 

 appearance of green verdigris in the interior of the butter. 



It is obvious that this defect is highly objectionable, verdigris 

 is poisonous and the green coloration is offensive. It can be easily 



