Spoilage characteristics and mechanisms of dominant spoilage Bacteria in fresh beef stored at ice temperature: Insights from in situ analysis and metabolomics.

Pseudomonas and Carnobacterium are the predominant spoilage microorganisms in beef, each playing a critical role in the spoilage process. However, the synergistic spoilage effects of these microorganisms on ice-temperature-stored fresh beef remain unclear. In this study, Pseudomonas marginalis (P.m), Pseudomonas lundensis (P.l), and Carnobacterium divergens (C.d), isolated from beef, were inoculated singly or in combination into ice-temperature-stored fresh beef to analyze their major metabolic pathways, spoilage characteristics, and mechanisms. After 15 days of ice-temperature storage, the co-culture of P.m and P.l exhibited enhanced motility and environmental adaptability, which accelerated spoilage and protein degradation. In contrast, in co-cultures containing C.d, the changes in total viable count (TVC), total volatile basic nitrogen (TVB-N), scanning electron microscopy (SEM) observations, TCA-soluble peptide content, electrophoretic profiles, and tissue structure were predominantly shaped by Pseudomonas species during spoilage. Metabolomic analysis revealed that, in the P.m-P.l group, the differential metabolites were mainly associated with histidine metabolism, glycerophospholipid metabolism, the tricarboxylic acid (TCA) cycle, purine metabolism, and biosynthesis of unsaturated fatty acids. Synergistic interactions between P.m and P.l significantly enriched metabolic pathways associated with amino acid, lipid, energy, nucleotide, and microbial metabolism. These two bacteria maintained intracellular metabolic homeostasis through microbial interactions. This study elucidates the spoilage phenotypes and metabolic networks of dominant bacteria in ice-temperature-stored fresh beef, thereby facilitating meat quality maintenance and providing a theoretical basis for targeted preservation strategies in the meat industry.