76 MANUAL OF MILK PRODUCTS 



hitherto been considered to be in the animal body is in reality 

 merely the carotin and xanthophylls of the food, which are 

 absorbed by the body and subsequently secreted in the milk-fat. 

 Numerous feeding experiments show that when the food is 

 deficient in carotin and xanthophylls for a period of time, the 

 milk-fat slowly decreases in color and eventually approaches a 

 colorless condition. The experiments also show that when 

 foods rich in carotin and xanthophylls are given to a cow whose 

 milk-fat is deficient in lipochrome, the color of the milk-fat at 

 once increases in proportion to the amount of pigments fed. 

 This is true, regardless of whether the carotins and xanthophylls 

 are associated with chlorophyll as in green feeds, or whether 

 chlorophyll is completely absent and xanthophylls almost so, 

 as in carrots. 



"The pure filtered fat was analyzed colorimetrically by means 

 of the Lovibond tintometer and its standard color glasses. The 



color of the fat was always 



compared in one-inch layer. 



The Lovibond tintometer is 



shown in Fig. 4. 



"The solution (in the present 



case melted butter-fat) whose 



color is to be measured is placed 

 FIG. 4. Lovibond tintometer in a cell with glass ends (one 

 milk flt r determining the color f inch apart in all this work), and 



the color matched by standard 



color glasses of various units of yellow, red, or blue, and the color 

 of the solution read by adding together the various glasses of 

 color, used to match the unknown color. Melted butter-fat 

 having an orange tint requires only yellow and red to match its 

 color. All readings are made with the instrument pointing 

 towards the daylight (not sunlight). The instrument is quite 

 sensitive towards the yellow glasses below 25 units of yellow, 

 but the sensitiveness decreases considerably above 40 units 



