Uncovering the Metabolic Characterization of Pseudomonas psychrophila and Serratia grimesii Underlying Their Spoilage Potential in Refrigerated Salmon: Based on LC-MS Metabolomics Analysis.

This study investigated the individual and synergistic spoilage mechanisms of Serratia grimesii and Pseudomonas psychrophila in sterile salmon during refrigerated storage at 4°C. Subsequently, non-targeted metabolomics was applied to uncover the potential spoilage-associated metabolic pathways. The results showed that P. psychrophila led to larger increases in total viable count (TVC), pH, and total volatile basic nitrogen (TVB-N) compared with S. grimesii, as well as caused more pronounced protein degradation, as evidenced by lower sulfhydryl content, higher carbonyl content, stronger proteolytic activity, and more free amino acid (FAA) accumulation. Metabolomic analysis based on liquid chromatography-mass spectrometry (LC-MS) further revealed considerable disruptions in amino acid, purine, and glycerophospholipid metabolism, with lysine degradation and phenylalanine metabolism standing out as particularly affected pathways. In contrast, S. grimesii mainly promoted the early stage of lipid oxidation, as indicated by the higher conjugated diene (CD) and peroxide value (POV) levels. This finding was further supported by the enrichment of lipid-related metabolic pathways. Notably, co-culture induced a distinct spoilage pattern rather than a simple additive effect. Although it did not consistently increase all spoilage indicators, it significantly promoted lipid hydrolysis. This study revealed the metabolic pathway and mechanism of microbial spoilage of S. grimesii and P. psychrophila in the spoilage process of salmon, providing insights into the roles of specific spoilage bacteria in fish deterioration and a theoretical basis for future spoilage control studies.