Activity of trisodium phosphate compared with sodium hydroxide wash solutions against Listeria monocytogenes attached to chicken skin during refrigerated storage

Abstract

The potential of using trisodium phosphate (TSP) and sodium hydroxide (NaOH) to reduce Listeria monocytogenes populations in chicken skin was studied. Raw chicken legs inoculated with L. monocytogenes were dipped in water (control), in 8% (pH=12·59), 10% (pH=12·68) and 12% (pH=12·75) (w/v) TSP solutions, or in NaOH solutions of equal pH values to those of TSP: 0·175%, 0·200% and 0·220% (w/v). Surface pH values and L. monocytogenes counts of chicken skin were determined immediately after treatment (day 0) and after 1, 3 and 5 days of storage at 2°C. Compared with water dipping, TSP and NaOH treatments significantly (P<0·05) reduce Listeria populations at days 0, 1, 3 and 5 of refrigerated storage. Bacterial reductions varied between 1·12 and 3·34 log10 cycles for TSP-treated samples and between 1·80 and 3·28 log10 cycles for NaOH treated samples. The observed reductions in all treated samples were significantly (P<0·05) greater following storage. The concentration of the TSP solution was a significant factor in reducing the populations of L. monocytogenes. However, bacterial reductions were similar in samples treated with different concentrations of NaOH. The TSP or NaOH treatments resulted in relatively high residual surface pH values (8–9) initially and throughout storage. The pH values were significantly higher in the samples treated with TSP than in those treated with NaOH.