220 TWENTY-FIFTH ANNIVERSARY REPORT. 
the butter. It was thought that the more concentrated brine had 
the effect of deepening the yellow color of the fat, the lighter por- 
tions being the unsalted or lightly salted areas. 
The following points were studied with reference to their pos- 
sible relations to mottled butter: (1) Richness of cream, (2) de- 
gree of ripeness of cream, (3) temperature of churning, (4) size 
of butter-granules, (5) temperature of wash-water, (6) working 
of butter. When the churning was so managed as to make the 
butter-granules of the size of rice-grains or wheat-kernels and 
these were carefully washed twice with water below 45° F., re- 
moving most of the buttermilk adhering to the outer surface of 
the granules, no mottles were obtained, however much conditions 
were varied in other respects. Mottles were always found when 
the buttermilk was not sufficiently removed. 
The amount of proteid (usually free casein) in mottled butter 
is greater in the light portions than in the darker portions and is 
the cause of the lighter color of the mottles. Salt-brine does not 
change in any way the color of butter-fat. Salt-brine, as it com- 
monly occurs in butter, has the power of hardening and localizing 
the proteid particles, the action requiring several hours for com- 
pletion. Butter which is free from buttermilk adhering to the 
outer surface of the granules does not produce mottles when salted, 
whether the salt is evenly or unevenly distributed. Mottles do not 
occur in unsalted butter. In mottled butter, the light portions 
usually contain less salt than the darker portions. 
Mottles in butter are due, primarily, to the presence and uneven 
distribution of buttermilk adhering to the outer surface of the small 
granules; and, secondarily, to the hardening and localizing effect 
of salt-brine upon the protein of the buttermilk thus retained in 
butter. The light portions of mottled butter owe their lighter color 
to the presence of localized protein, usually free casein. The yellow 
or clear portions occur when the spaces between the butter-granules 
are filled with clear brine and are comparatively free from casein. 
Several hours are required to complete the action of brine upon 
the protein of butter. In the absence of buttermilk in butter- 
granules, we have no mottles. In the absence of salt we have no 
mottles. The combined conditions necessary to produce mottles are | 
(1) the presence of sufficient buttermilk unevenly distributed, and 
(2) the presence of salt-brine. Mottles in butter can be prevented 
by avoiding those conditions that retain buttermilk in the butter and 
observing those conditions that favor the removal of buttermilk 
