Beta-Lactam Antibiotic Stability in Chicken Meat

Background/Objectives: Residues of β-lactam antibiotics in foods of animal origin are important for official residue control and public-health risk assessment. Sample storage conditions may affect the measured concentrations of these analytes, whereas cooking may influence consumer exposure. This study evaluated the stability of six β-lactam antibiotics—amoxicillin, ampicillin, phenoxymethylpenicillin, benzylpenicillin, cefazolin, and cefotaxime—and clavulanic acid, a β-lactamase inhibitor, in chicken meat during storage and thermal processing. Methods: Incurred chicken meat samples were obtained after in vivo administration of the studied compounds. Stability was assessed during storage at +4 °C, −20 °C, and −86 °C for up to 165 days, during repeated freeze–thaw handling, and during heating at 100 °C for up to 30 min. The target compounds were quantified by HPLC–MS/MS after acetonitrile extraction and hexane clean-up. Results: The studied compounds were unstable at +4 °C, with concentrations decreasing below the detection limit within 3–27 days depending on the compound. Storage at −20 °C was insufficient for long-term preservation of most penicillins, whereas −86 °C improved stability. Cefazolin was the most stable compound under the tested storage conditions, while cefotaxime was the least stable. Heating at 100 °C for 30 min caused substantial reduction in parent-compound concentrations, ranging from 63.8 ± 4.0% for cefazolin to complete disappearance below the detection limit for cefotaxime. Conclusions: For reliable official residue analysis, chicken meat samples intended for β-lactam testing should be stored at −86 °C whenever long-term storage is required. Repeated thawing should be avoided. Cooking substantially reduces the concentrations of the parent compounds but cannot be considered a reliable safety measure, because degradation may be incomplete and degradation products were not assessed in this study.