New YorK AGRICULTURAL EXPERIMENT STATION. 293 
favor any movement. The brine present in freshly packed butter 
does not necessarily remain, each particle, in the exact position in 
which it is left when packed and not subject to any further 
mechanical manipulation. The conditions that favor movement 
or limited circulation of the brine in butter are an unequal distri- 
bution of salt brine and buttermilk, producing a variation in the. 
specific gravity which tends thus to become uniform within 
limited areas. When there is an imperfect removal of the but- 
termilk adhering to the outer surface of the small butter-granules, 
the buttermilk is unevenly distributed, being more or less local- 
ized in different portions of the mass of butter. When the salt 
brine comes into contact with these masses of buttermilk, the 
casein lactate is slowly acted upon by the brine, being hardened 
and remaining localized. The yellow or clear portions occur 
where the spaces between the butter-granules are filled with 
clear brine and are comparatively free from casein compounds. 
The fact that time is required to produce mottles is explained, 
first, by the time required for the movement or circulation of 
brine to take place and come in contact everywhere with the casein 
compounds, assuming that this has not occurred in the working of 
the butter, and second, by the amount of time required for brine 
to act upon the casein compounds of butter. 
The discussion presented in the foregoing paragraph is, apart 
from the facts that have been clearly established, intended as a 
theoretical explanation or suggestion of what takes place when 
mottles form in butter. While the data presented point to the 
fact that there is some movement of brine in packed butter, the 
matter has not been studied in sufficient detail to justify any 
specific statement. Such a study is attended with serious diffi- 
culties, but we plan to make further investigation of this phase 
of the subject. 
PREVENTION OF MOTTLES IN BUTTER. 
Since the presence of mottles in butter is primarily due to an 
excess of buttermilk in the mass of butter-granules, the most 
effective method of preventing mottled butter is to free the but- 
ter-granules as completely as practicable from the buttermilk 
adhering to the small granules. In order to accomplish this, 
the churning should be stopped when the granules are about the 
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