LIPIDS PRESENT IN EGGS 813 



c. Cholesterol Present in Eggs. Eggs contain a comparatively large 

 proportion of cholesterol. Skarzynski 597 reported values for hens' eggs 

 ranging between 0.38 and 0.56%; each egg was shown to have about 0.25 

 g. of cholesterol. Lange 486 cites the following analyses for the cholesterol 

 content of egg yolk in milligram per cent: yolk, 1347 ; 487 yolk, vacuum- 

 dried, 1750 ; 598 yolk, frozen, 1365 ; 599 Chinese dried yolk, 2810 ; 599 commer- 

 cial dried eggs, 2870 ; 599 yolk, dried, 3900 ; 488 yolk, fresh, 2000. 488 Miya- 

 mori 600 found that the cholesterol content of egg yolks of twenty-two 

 kinds of birds varied only slightly, being 1 to 2% in all but two species. 



d. Lipoproteins Present in Eggs. Alderton and Fevold 601 isolated a 

 lipoprotein, lipovitellin, from egg yolk. This protein was found to com- 

 prise 18% of the egg-yolk solids. About 16 to 18% of the lipoprotein con- 

 sisted of phospholipid, which was largely lecithin. In a later study, 

 Fevold and Lausten 602 isolated another lipoprotein, called lipovitellenin, 

 which contained 36 to 41% of alcohol-extractable phospholipids. This 

 was shown to comprise 40% of the total lipoprotein in egg yolk, and to make 

 up 12 to 13% of the egg-yolk solids. Lipovitellenin is a phosphoprotein 

 similar to lipovitellin, but it contains only one-third as much phosphorus 

 as does lipovitellin. Lea and Hawke 603 showed that the combination of 

 phospholipid with protein stabilized the lipid against the catalytic action 

 of copper and hemin, but not against that of hemoglobin. The lipoprotein 

 could be freeze-dried at a pH of 7.0 with little decomposition; it was com- 

 paratively stable at low temperatures or even at 37 °C, if extremely dry. 604 



{2) Factors Altering the Composition of Egg Lipids 



a. The Effect of Diet. It is well known that the fatty acids of the neu- 

 tral fat and phospholipids of egg yolk are greatly influenced by the fat of 

 the food. As early as 1888, Liebermann 605 demonstrated that the yolk 

 was laid down in successive rings; each ring represented the deposition 

 of yolk material for one day. The bulk of the yolk was shown to be laid 



597 B. Skarzynski, Bull, intern. Acad, polon. sci., Classe sci. math, nat., 1936B, II, 437- 

 452. 

 698 E. Fourneau and M. Piettre, Bull. soc. chim. France [4] 11, 805-810 (1912). 



599 E. O. Haenni, J. Assoc. Official Agr. Chemists, 24, 119-147 (1941); 25, 365-368 (1942). 



600 S. Miyamori, Nagoya J. Med. Sci., 8, 176 (1934). 



601 G. Alderton and H. L. Fevold, Arch. Biochem., 8, 415-419 (1945). 



602 H. L. Fevold and A. Lausten, Arch. Biochem. 11, 1-7 (1946). 



603 C. H. Lea and J. C. Hawke, Biochem. J., 50, 67-73 (1951). 



604 C. H. Lea and J. C. Hawke, Biochem. J., 52, 105-114 (1952). 



606 L. Liebermann, Arch. ges. Physiol. (Pfliiger's), 43, 71-151 (1888). 



