Integrating widely targeted and oxylipin-targeted lipidomics unravels lipid characteristic evolution and oxidation markers in walnuts during deterioration

Abstract

The susceptibility of walnut lipids to deterioration constitutes challenges for industry development, and the oxylipins formed during this process remain to be explored. This study employed lipidomics to reveal the dynamic evolution of lipid characteristics and identify oxidation markers from oxylipins in walnuts during accelerated storage. Glycerophospholipid (GP) content continuously declined in the initial and severe deterioration stages. The accumulation of diglycerides and partial lysophospholipids characterized initial deterioration. Triglycerides were prone to direct oxidation, while GPs tended to be first hydrolyzed. GP metabolism especially phosphatidylethanolamine degradation triggered walnut deterioration. Moreover, ten oxylipins derived from linoleic acids were identified in walnuts. Trans-EKODE-(E)-Ib, 13-HODE, 9-HODE, and 9(S),12(S),13(S)-TriHOME were screened as oxidation markers. The cellular structure exhibited the cell membrane and oil body membrane rupture during deterioration. Potential mechanisms of lipid deterioration were proposed, providing a scientific basis and guidance in optimizing quality control strategies and assessing practical deterioration degrees of walnuts.

Keywords: Deterioration; Glycerophospholipid; Lipidomics; Oxylipin; Paper-skinned walnut.