Effects of post-harvest hypoxic stress on post-landing recovery of live scallops (Mizuhopecten yessoensis) revealed by untargeted metabolomics based on UPLC-Q-TOF-MS

Abstract

Early post-harvest processes, from on-board handling to land-based depuration, is considered as the quality determination period (QDP) of bivalves. Hypoxic stress induced by air exposure is one of the most severe stresses during the QDP. In the present study, a metabolomics analysis based on ultra-performance liquid chromatography quadrupole-TOF mass spectrometry (UPLC-Q-TOF-MS) was performed to characterize the metabolic changes in emersed scallops (Mizuhopecten yessoensis) during the QDP and the metabolic regulation after reimmersion. A total of 34 differentially abundant metabolites between the control and emersion groups were identified, including 6 down-regulated and 28 up-regulated; these metabolites were involved in the pentose phosphate pathway, glyoxylate and dicarboxylate metabolism, and biosynthesis of unsaturated fatty acids. Additionally, disturbances in energy metabolism, the osmotic regulation system and membrane fluidity also occurred in emersed scallops. Among the discriminant metabolites, 13 metabolites were significantly regulated after reimmersion and can be considered biomarkers for scallop quality assurance. Moreover, the pH, glycogen and ATP-related compound levels of scallops were changed under air exposure conditions but recovered after reimmersion. The results show that this metabolomics approach could be used as a new strategy for investigating metabolic variations in scallops to reveal the effects of post-harvest hypoxic stress on freshness quality. This study indicates that air exposure is a feasible, simple and convenient method that can be used in early post-harvest handling during the QDP without causing irreversible physiological disruption to scallops.