Exudate-based microbial and metabolomic profiling for assessing beef spoilage and Salmonella contamination

This study evaluated the microbial and metabolomic profiles of beef exudate to determine its suitability as a non-invasive matrix for monitoring spoilage (experiment 1) and Salmonella contamination (experiment 2). In experiment 1, vacuum-packaged longissimus lumborum (LD) muscles from six United States Department of Agriculture (USDA) utility-grade beef carcasses were stored at 1 °C (control) or 10 °C (accelerated spoilage) for up to 6 weeks. In experiment 2, ground LD and gluteus medius muscles were assigned to control or Salmonella Typhimurium -inoculated groups and stored at 4 °C for 28 days. Exudate and tissue samples were analyzed for total viable count (TVC), lactic acid bacteria (LAB), and Salmonella counts (experiment 2). Untargeted ultra-performance liquid chromatography–mass spectrometry (UPLC–MS) was conducted on exudate samples. Microbial loads increased with storage time, particularly at 10 °C. In experiment 1, TVC reached 6.03 log 10 CFU/mL in tissue and 8.39 log 10 CFU/mL in exudate, and LAB reached 5.80 and 6.34 log 10 CFU/mL, respectively, after 6 weeks at 10 °C. In experiment 2, Salmonella counts declined during storage but remained detectable, while TVC and LAB increased. Metabolomic profiling identified 49 spoilage-associated metabolites in experiment 1, including hypoxanthine, xanthine, trimethylamine, acyl-coenzyme A, nicotinamide adenine dinucleotide (NAD), and adenosine monophosphate (AMP). In experiment 2, 40 key metabolites were associated with Salmonella -inoculation, predominantly amino acids and peptides. Notably, L-methionine, proline, and arginine exhibited 1.2–6.5 log 2 fold increases in inoculated samples. These findings provide proof-of-concept evidence that beef exudate reflects microbial dynamics and metabolic shifts during spoilage and Salmonella challenge. The identified metabolomic features warrant further validation as potential non-destructive biomarkers for meat quality control and contamination detection. • Beef exudate was evaluated as a non-invasive matrix for spoilage and contamination monitoring. • Microbial counts (TVC, LAB, Salmonella ) increased with storage time and temperature. • Exudate metabolomics identified key spoilage-associated metabolites (hypoxanthine, TMA, AMP). • Salmonella -inoculated samples exhibited distinct amino acids enrichment (proline, arginine). • Exudate profiling integrates microbial and metabolic signals for predicting meat quality assessment.