Quantitative lipidomic analysis of chicken egg yolk during its formation.

BACKGROUND: The accumulation of lipids in egg yolk during its formation represents a knowledge gap between food science and animal science research to which researchers in either field have not paid sufficient attention. Therefore, the egg yolk samples during different periods of formation (yellow follicle, YF; small hierarchical follicles, SF; and the largest hierarchical follicle, LF) were prepared, and their fatty acid compositions and lipidomes were quantitatively compared. RESULTS: The fatty acid profiles and lipidomes of egg yolks at the three stages of formation were significantly different. The relative content of oleic acid and palmitic acid were increased, but that of the main polyunsaturated fatty acids (linoleic acid, linolenic acid and docosahexaenoic acid) was decreased in the SF period to the LF period. Among the 786 lipid molecular species identified, 150 and 46 differentially abundant lipids (DALs) were identified in the pairwise comparison of YF/SF (early stage of egg yolk formation) and SF/LF (late stage of egg yolk formation), respectively. Triglycerides and diglycerides, represented by TG(14:0/18:1/20:1) and DG(18:1/18:1/0:0), were decreased, whereas free fatty acids (especially free unsaturated fatty acids) were greatly increased during yolk formation. The changes in phospholipids were complex; the relative abundance of phosphatidylcholine [represented by PC(18:0/22:5)] decreased, whereas phosphatidylethanolamine [represented by PE(18:0/18:0)] increased. In addition, the relative abundance of lysophosphatidylcholine [represented by LPC(18:1/0:0)] was increased during egg yolk formation. CONCLUSION: The transport and accumulation of lipids into the egg yolk is dynamically adjusted during its formation, and the transport and timing of different lipid molecular species are different. © 2022 Society of Chemical Industry.