Characterization of packaging remnants and chemical contaminants in former foodstuff products for animal nutrition

Former foodstuff products (FFPs) are increasingly seen as promising circular feed ingredients that can enhance sustainability in livestock production by reducing food waste, improving resource efficiency, and promoting feed self-sufficiency. However, their safe use requires monitoring for physical and chemical contaminants, particularly from packaging residues and legacy pollutants. This study aimed to (1) quantify packaging remnants and regulated contaminants in FFPs, and (2) investigate correlations between packaging materials and contaminant levels. Fifteen FFP samples were analyzed for packaging fragments using µ-FTIR spectroscopy, identifying plastics, aluminium, and polysaccharides (e.g., paperboard). Metallic trace elements (MTEs: Al, As, Cd, Pb) were measured by ICP-MS, while persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), dioxins, and furans (PCDD/Fs) were assessed by HRGC-MS/MS. Packaging remnants were frequently detected, particularly polysaccharides (16.9 ± 11.7) and plastics (6.5 ± 6.6 pieces per 60 g sample). Although contaminant concentrations varied across samples, all remained below EU regulatory thresholds. Arsenic ranged from 0.01–0.12 mg/kg, Pb from 0.03–0.19 mg/kg, and Cd was detected in only five samples (0.05–0.06 mg/kg). The sum of indicator PCBs ranged from 0.14–0.63 µg/kg, and total TEQ values for PCDD/Fs and dioxin-like PCBs ranged from 0.03–0.11 ng TEQ/kg. Spearman correlation analysis revealed associations (P ≤ 0.05) between aluminium residues and hepta/octa-chlorinated PCDD/Fs (r = +0.56 to +0.71), polysaccharides with PCDD/F TEQ (r = +0.77) and Pb (r = +0.59), and plastics with Pb (r = +0.61). However, these results should be interpreted with caution due to unknown background contamination, variable amount and type of packaging materials identified, and small number of samples analyzed. Although current contamination levels pose no immediate risk, the frequent presence of packaging fragments highlights the need for improved processing strategies and continued monitoring to ensure the safe integration of FFPs in sustainable feed systems.