Cholesterol and Cholesteryl Esters of Eggs from Various Avian Species

Abstract

A method was developed to analyze the cholesterol and cholesteryl esters of egg yolk by gas liquid chromatography (GLC). After the cholesteryl ester fraction was isolated by chromatography on a silica gel (Hi-Flosil) column, individual esters were quantitatively separated and determined by GLC on glass columns packed with SP-2340. The cholesterol content and nature of the cholesteryl esters in eggs from various avian species were determined. Birds were classified according to feeding habits as follows: 1) domestic fowl eating grain and plant materials –White Leghorn chicken, Silver-penciled Plymouth Rock chicken, turkey, Japanese quail; 2) wild plant-eating birds–ring-necked dove, grackle, peacock; 3) wild birds eating aquatic plants and animals–mallard duck, black duck; 4) wild aquatic carnivorous birds–laughing gull, brown pelican, great black-backed gull, black-crowned night heron; 5) wild mammal-eating birds–barn owl. Although egg size varied from 7 to 121 g, total cholesterol content ranged only from 12 to 25 mg/g yolk. Cholesterol present as ester ranged from 1 to 26% in the 14 birds studied. Most of the cholesterol present as ester was esterified to 18:1 or 18:2 fatty acids. Analysis of yolk lipid indicated that the fatty acids were comprised mainly of 16- and 18-carbon fatty acids. The predominant order of concentration in all species was 18:1>16:0>18:2. There was no consitent pattern in egg cholesterol content or in the percentage of cholesteryl esters in the species studied. Differences existed, however, in the composition of the cholesteryl esters and in the composition of egg yolk fatty acids that distinguished one bird species with particular feeding habits from another.