Phospholipid degradation is induced by heat in alpha-tocopherol-enriched eggs

A comparative study was undertaken to determine the effect of an alpha-tocopherol- and iodine-enriched laying diet on the phospholipid profile of egg yolk. In addition to the comparative study between the experimental and control eggs, experiments were conducted to determine the effects of heating on the phospholipid profile and the comparative molar ratios of cholesterol and total phospholipid. The phospholipid composition determined for frozen egg yolk samples showed no differences for the major components of phosphatidylcholine and phosphatidylethanolamine between the control and experimental diet group. In control eggs, exposure to boiling water produced time-related elevations in the concentration of lyso-phosphatidylcholine. A similar heat-related elevation in lyso-phosphatidylethanolamine was observed in both groups after 10 min. A time shift was observed in the heat susceptibilities of the experimental diet group. The control egg yolks hardened more quickly when exposed to heat. The results suggest protection against oxidative degradation of phospholipids and possible inhibition of phospholipases A2 and C, which may result from the elevated level of alpha-tocopherol in the experimental egg yolks.