Survival of Salmonella in dried chicken meat residues on the surface of packaging materials

Salmonella contamination in raw chicken products may be transferred on materials used for meat packaging or re-packaging, which could then potentially serve as sources of cross-contamination of surfaces or foods in the home. This study evaluated survival of Salmonella in chicken meat residues on stored food packaging materials. Samples (5×5 cm) of aluminium foil, butcher paper, cardboard, PVC overwrap film, and vacuum bags were spot-inoculated (0.5 ml; 2-3 log CFU/cm2) with a 7-strain mixture of Salmonella suspended in a non-sterile raw chicken meat/water homogenate (10% wt/wt), simulating chicken meat purge. Materials were stored aerobically in petri dishes at 4 or 25°C, and were periodically analyzed (two replicates with three samples per material each time) for survivors on tryptic soy agar and XLD agar. Initial levels (2-3 log CFU/cm2) of Salmonella increased to 4-5 log CFU/cm2 within 4 days of storage at 25°C on all tested materials, except cardboard. After 123 days at 25°C, Salmonella was recovered from all the tested materials, with counts ranging from <0.82±1.09 (cardboard) to 4.79±0.70 (butcher paper) log CFU/cm2. Counts decreased on all materials stored at 4°C and reached non-detectable levels (<-0.40 log CFU/cm2) on cardboard and PVC overwrap film by day-39 and -53, respectively. Survivors of not more than -0.32±0.19 and -0.20±0.49 log CFU/cm2 were recovered from butcher paper and vacuum bags, respectively, after 88 days at 4°C. Salmonella can survive in food residues present on packaging materials for long periods of time. Thus, cross-contamination should be considered when handling or storing soiled packaging materials.