Lipolysis and Oxidation of Lipids during Egg Storage at Different Temperatures

The aim of this study was to investigate lipolysis and lipid oxidation of stored eggs at different temperatures (4 and 22 degrees C) by evaluating the changes in physicochemical index, lipid profiles, enzymatic activity, and oxidative index. The results showed that the changes in physicochemical index were more significant at 22 degrees C than at 4 degrees C. Weight loss, moisture content, and pH of egg yolk increased significantly (P < 0.05), whereas the yolk index decreased during storage. However, there was no significant difference in lipid profiles between 4 and 22 degrees C storage temperature. The lipid composition analysis demonstrated that lipid hydrolysis took place during egg storage and resulted in a marked decrease of PL and increase of FFA. It was also found that the content of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI) decreased significantly during storage. The correlation analysis showed that the lipid degradation is significantly positively related to lipase activity (P < 0.05), and the marked changes of lipid fractions are results of both hydrolysis and oxidation. It can be concluded that the egg physicochemical index and lipase activity were greatly influenced by temperature during storage, but the yolk lipid stability was not significantly influenced by storage temperature.