Cholesterol and phospholipids content of yolk from fertilized and unfertilized hen eggs

Three lipid-containing fractions (granules, low-density lipoproteins (LDL) and infranatant) of fertilized and unfertilized yolks were obtained from hen eggs, either from commercial sources or from Arbor acres hens kept by the Pena Branca Aviário Pernambuco and utilized fresh (laid during the previous 7 days). Total cholesterol (TC) and total phospholipid (TP) levels (mg/g yolk, reported as means +/- SD) were determined. In the yolk granules (insoluble fraction) the levels of TC (2.05 +/- 0.36) and TP (0.90 +/- 0.43) of fertilized egg yolks were similar to the levels of TC (2.20 +/- 0.41) and TP (0.90 +/- 0.14) of unfertilized eggs. The TC levels in the LDL from fertilized egg yolks (8.29 +/- 1.63) were not statistically different from those in unfertilized eggs (7.31 +/- 1.50). In contrast, TC was not detected in the infranatant fraction of unfertilized egg yolks, but was present in the infranatant fraction (1.39 +/- 0.69) of fertilized eggs. The TP levels of LDL (0.73 +/- 0.23) and infranatant (0.32 +/- 0.09) fractions of fertilized egg yolks were significantly lower than the levels of TP in the LDL (1.73 +/- 0.51) and infranatant (0.79 +/- 0.59) fractions of unfertilized eggs. Consequently, the TC/TP ratio (mol/mol) increased in the LDL and infranatant fractions of fertilized egg yolks when compared to unfertilized egg yolks. TC levels were similar in the total yolk of fertilized (10.76 +/- 1.32) and unfertilized (10.33 +/- 1.77) eggs, while the TP levels were significantly lower in the fertilized (1.92 +/- 0.17) than in unfertilized (3.43 +/- 0.97) eggs.(ABSTRACT TRUNCATED AT 250 WORDS)