UHPLC-Q-Orbitrap-based untargeted lipidomics reveals the variation of yolk lipids during egg storage

Egg yolk is recognized for its excellent nutritional benefit and economic value; however, egg is a perishable food, potentially losing quality if not handled properly between the time from farm production to consumption. Knowledge of the changes of yolk lipid composition under an extreme storage condition close to vitelline membrane breaking, which results in an inedible condition for shelf-eggs, remains incomplete. Considering the complexity of yolk lipids, the architectural features of yolk lipids at high-temperature storage (30°C for 10 days versus fresh) were classified through lipidomics.

This strategy yielded 1508 features within the lipid database coupled with 74 significantly different lipids (P < 0.05, fold change > 1.2 or < 0.83), mainly triglycerides, phospholipids, and sphingolipids. Most of them were decreased after storage; for example, triglycerides were assumed to play a role as a 'buffer' to maintain the system stability during storage by balancing fatty acid saturation, which strongly reduces the egg edible value for humans. Furthermore, phospholipids, especially the highly unsaturated phosphatidylcholine, decreased significantly and were suggested to be the primary cause for the variation in yolk emulsifying properties and flavor.

Altogether, these results deriving from oxidation and lipolysis reactions enhance our understanding of lipid transformation and the biochemical mechanisms, at the molecular level, of the deteriorative process of the egg yolk. These findings may lay the foundation for identifying processes, including some modifications of the lipid composition of rations fed to laying hens, aiming to improve the long-term shelf-stability of shell eggs and egg products. © 2022 Society of Chemical Industry.