PHYSICAL PROPERTIES OF MILK 77 



of yellow. In other words, it is possible to match the exact 

 color of an "unknown" much more closely when its color is 

 below 30 to 35 units of yellow than when its color is above this 

 value. In a great many cases, and this nearly always applies 

 to butter-fat, it is possible to match the tint of the fat, but the 

 color of the fat is more brilliant than that of the combined 

 standard glasses. In this case an exact match can be obtained 

 by ' damping down ' the butter-fat color by inserting in front of 

 it equal units of the three colors, yellow, red, and blue, and re- 

 cording this as 'light.' 



"Before reporting the data dealing with the variation in the 

 color of the butter-fat it may be possible to convey some idea 

 of what the various colors mean when applied to butter-fat by 

 stating that rendered 'June' butter in the one-inch cell will 

 give a color of from 80 to 60 units of yellow. Color readings 

 between 45 and 25 units of yellow would accordingly indicate 

 a fairly well-colored to light-colored butter, between 20 and 8 

 units of yellow would be called light to very light-colored butter, 

 while below these limits, ranging down to 1 or 2 units of yellow, 

 would be called white to 'dead' white, especially if the fat 

 was still in the form of butter." 

 Source of the yellow color in milk-fat (Palmer and Eckles) . 



A pure-bred Jersey was changed from a ration rich in carotin 

 and xanthophylls to a ration containing a very small amount of 

 these pigments. The ration rich in carotin and xanthophylls 

 consisted of alfalfa hay and yellow corn. The ration poor in 

 these pigments was composed of bleached clover hay and white 

 corn. 



The change from a ration rich in carotin and xanthophylls to 

 one poor in these pigments caused the color of the butter-fat to 

 drop from 43 units of yellow to 8.5 units of yellow, from a well- 

 colored to a very light-colored fat. This change of color was 

 very gradual and required twenty-nine days. It should be 

 stated, however, that the cow did not relish her non-pigmented 



