EFFICACY OF OPTIMIZED NISIN-BASED TREATMENTS TO INHIBIT SALMONELLA-TYPHIMURIUM AND EXTEND SHELF-LIFE OF BROILER CARCASSES

Nisin is an antimicrobial peptide produced by Lactococcus lactis subsp . lactis. Nisin exhibits a broad spectrum of inhibitory activity again st gram-positive microorganisms such as Listeria monocytogenes and Clo stridium botulinum. In previous studies, a method was developed using nisin in combination with food-grade chelating agents to inactivate Sa lmonella species and other gram-negative bacteria. The objectives of t his study were to determine the efficacy of several optimized nisin-co ntaining preparations for reducing the population of Salmonella typhim urium NAR on broiler drumstick skin and whole drumsticks and extending the shelf life of broiler drumsticks. In previous studies, a simplex algorithm was used to optimize the biocidal activity of nisin towards Salmonella by adjusting formula pH and adding varying concentrations o f chelating agents (EDTA, citric acid) and a surfactant (Tween 20). Fr om these studies, four optimal treatments were identified. These were tested more extensively in the present study. Significant reductions i n viable S. typhimurium NAR populations on broiler drumstick skin were achieved and ranged from 3.1 to 4.9 log(10) cycles following immersio n for 30 min at 25 degrees C. The inhibitory activities of these four treatments against S. typhimurium NAR-contaminated drumsticks were als o compared to treatments with 20 ppm chlorine. Numbers of survivors fo llowing a 30-min dip ranged from <10 to 2.57 x 10(1) organisms per mi of skin rinse for the nisin formulations versus 1.32 x 10(2) organisms per mi on the chlorine-treated drumsticks. In other studies, the shel f life of refrigerated broiler drumsticks was extended by 1.5 to 3 day s following immersion for 30 min in one of the optimized nisin-contain ing treatments in comparison to drumsticks dipped in sterile distilled , deionized water.