The Potential Impact of Rigor Mortis on Antibiotic Residues in Bovine Ribeye and Kidney

The current investigation aimed to evaluate the effects of rigor-mortis durations, ranging from four to forty-eight hours, on antibiotic residues found in bovine ribeye and kidney samples. The study's hypothesis is that some rigor mortis cascades can change and even destroy structural meat components, which affects the quality of the meat. Thirty random samples of fresh ribeye loin (Musculus longissimus thoracis et lumborum) cut and kidney (15 of each) were obtained from various butchers in Cairo, Egypt, and promptly delivered to the laboratory for analysis. The mean pH48h results of the ribeye samples were substantially lower than the mean pH4h. A 48-hour rigor-mortis with chilling at 4 °C shows statistically significant reducing effects on concentrations of 41.6% (5/12) of antibiotic residues detected in ribeye, including amoxicillin, ampicillin, ciprofloxacin, norfloxacin, oxytetracycline, and tylosin (P < 0.05). In contrast, antibiotic-residues in the kidney were not affected by the 48-hour postmortem duration. The antibiotic-residues declining curve could be caused by postmortem meat fluid loss, such as purge loss, and the potential occurrence of antibiotic residue biotransformation under rigor-mortem pathways. Nonetheless, the current study limitations should be the focus of future research involving many antibiotic-positive samples, focusing on discovering reaction products that may be generated postmortem from proposed postmortem biotransformation cascades such as hydrolytic cleavage of different antibiotic residues. Finally, the investigations on animals using known antibiotics should be undertaken to validate and/or rule out this possibility.