Effectiveness of trisodium phosphate against Listeria monocytogenes on excised and nonexcised chicken skin

The influence of sample type (i.e., excised versus nonexcised chicken skin) on the efficiency of trisodium phosphate (TSP) solutions in reducing Listeria monocytogenes populations and inhibiting their growth during refrigerated storage was studied. Whole chicken legs and excised chicken leg skin fragments inoculated with 108 CFU of L. monocytogenes per ml were dipped for 15 min in sterile tap water (control) or in a solution containing 8, 10, or 12% TSP L. monocytogenes counts were determined after 0, 1, 3, and 5 days of refrigerated storage (2degreesC). The decontamination effect of TSP was greater for excised skin than for whole legs. Microbial differences between control and TSP-treated samples were significantly- larger for excised skin than for whole legs for 9 (75%) of 12 tested combinations of TSP concentrations and storage times. These differences varied from 1.05 +/- 0.26 log(10) cycles (day 1) to 3.30 +/- 0.14 log(10) cycles (day 5) for nonexcised-skin samples (whole legs) and from 1.54 +/- 0.48 log(10) cycles (day 1) to 4.28 +/- 0.86 log(10) cycles (day 5) for excised-skin samples. Significantly larger reductions were observed from the third day of refrigerated storage onward. The TSP concentration was a significant factor in the reduction of L. monocytogenes populations. These results suggest that bacteria are more readily accessible to TSP in excised than in nonexcised chicken skin and that the type of sample used to ascertain the efficacy of antimicrobial surface treatments may influence the findings of this type of study.