CAROTIN THE PRINCIPAL NATURAL YELLOW PIGMENT OF 

 MILK FAT JPART II.* 



Chemical and Physiological Relations of Pigments of Milk Fat to the 

 Carotin and Xanthophylls of Green Plants. 



LEROY S. PALMER AND C. H. ECKLES 



For a number of years the great variety of yellow animal pig- 

 ments have been classified under the general name lipochrome. Recent 

 investigations by Willstatter and Escher, 1 and by Escher 2 have shown, 

 however, that some of these pigments are in reality very closely related 

 or identical with the carotin or xanthophyll pigments of plants. Will- 

 statter and Escher have analyzed the pure lutein of egg yolk and 

 found it to be isomeric with the crystalline xanthophyll of green 

 plants; and Escher has identified in the same manner the lipochrome 

 of the corpus luteum as a true carotin. The isolation of both pig- 

 ments was attended with great difficulty. In the case of the egg yolk 

 pigment the yolk of 6,000 hen eggs yielded only four grams of crude 

 crystalline pigment, while in the case of the corpus luteum pigment 

 less than 0.5 gram of crystals were obtained from 10,000 cows' ovaries. 



The natural yellow pigment of butter is the most commonly ob- 

 served of all animaF lipochromes. It is also more important from a 

 commercial standpoint than any other animal pigment; the public 

 judges the richness of dairy products by their yellow color, and de- 

 mands that butter especially shall have a standard shade of yellow. 

 The pigment of butter fat, however, has been the least investigated 

 of all animal lipochromes. Thudichum's 3 classical investigation in- 

 cluded the pigment of butter fat under the general classification lutein, 

 which he proposed. No other study of the butter fat pigment has 



1. Zeit. f. Physiol. Chem. 76, pp. 214-225 (1912). 



2. Zeit. f. Physiol. Chem. 83, p. 198 (1913). 



3. Proc. Roy. Soc. 17, p, 253 (1869). 



* See Res. Bui. No. 9, p. 312, for statement of co-operation with U. S. 

 Dept. of Agriculture. 



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