Efficacy of nisin-coated polymer films to inactivate Salmonella Typhimurium on fresh broiler skin

Nisin is an antimicrobial peptide produced by the food-grade microorganism Lactococcus lactis subsp. lactis. This peptide inhibits many gram-positive bacteria, and when combined with chelating agents it inhibits gram-negative bacteria such as Salmonella sp. The efficacy of packaging films treated with nisin-containing formulations to reduce Salmonella contamination of fresh broiler drumstick skin and increase the refrigerated shelf life was investigated. Three films (5.1 cm(2)) of varying hydrophobicities (polyvinyl chloride [PVC], Linear low density polyethylene, nylon) were coated with one of three liquid formulations (pH 3.5 to 3.8) composed of 100 mu g/ml nisin and varying concentrations of citric acid, EDTA, and Tween 80. The treated films were applied either wet or dry to 5.1-cm(2) broiler drumstick skin samples inoculated with a nalidixic acid-resistant (NAr) strain of Salmonella Typhimurium. After incubation at 4 degrees C for 24 h the populations of surviving Salmonella Typhimurium(NAr) organisms were recovered from the skin and film samples using a rinse procedure and enumerated on brain heart infusion agar containing 800 ppm NA. Log reductions (untreated versus treated skin) in Salmonella Typhimurium(NAr) populations ranged from 0.4 to 2.1. Treatment formulation compositions and wet versus dry treatment application also influenced the extent of kill. The shelf life of refrigerated broiler drumsticks was extended by 0.6 to 2.2 days following a 3-min immersion in a nisin-containing treatment solution and subsequent storage in a foam tray pack containing a nisin-treated PVC overwrap and a nisin-treated absorbent tray pad. These findings demonstrated that Salmonella Typhimurium and spoilage microorganism populations on the surface of fresh broiler skin and drumsticks can be significantly reduced using immersion treatments, absorbent tray pads, and packaging films treated with nisin-containing formulations.