Efficacy of trisodium phosphate solutions in reducing Listeria monocytogenes populations on chicken skin during refrigerated storage

Chicken skin inoculated with 10(8) CFU/ml of Listeria monocytogenes was dip ped for 15 min in sterile water (control) and in 8, 10, or 12% trisodium ph osphate (TSP) solutions. Skin samples were stored at 2 degreesC for 5 days, with microbial monitoring on days 0, 1, 3, and 5 after treatment. Compared to the water dip, all TSP treatments significantly (P<0.05) reduced L. mon ocytogenes populations on chicken skin. The concentration of the TSP was a significant factor in reducing the populations of the bacteria at days 0, 1 , 3, and 5 of refrigerated storage. For all sampling times, the best outcom es were attained with the highest TSP concentration studied (12%). Bacteria l reductions in counts during the first day of storage were between 1.52 an d 2.70 log(10) cycles for 8 and 12% TSP-treated samples, respectively. Sign ificantly greater reductions were observed from the third day of refrigerat ed storage onward. This occurred largely because populations of L. monocyto genes on control samples increased somewhat, but on TSP-treated samples the pathogen remained practically constant. Differences between L. monocytogen es counts in skin samples immersed in water and those treated with TSP rang ed from 2.10 (8% TSP-treated samples) and 3.63 (12% TSP-treated samples) lo g(10) cycles on day 5 of storage. These results indicated that TSP is effec tive against L. monocytogenes in chicken meat, especially after several day s of refrigerated storage.