Growth kinetic parameters of Gram-positive and Gram-negative bacteria on poultry treated with various chemical decontaminants

The aim of this study was to determine the influence of 12% trisodium phosphate (TSP), 1200 ppm acidified sodium chlorite (ASC), 2% citric acid (CA), 220 ppm peroxyacids (PA) and 50 ppm chlorine dioxide (CD) on the lag phase (L; days), the maximum growth rate (μ; increase in log10 cfu/cm2/day) and the maximum population density at stationary phase (D; log10 cfu/cm2) of four bacteria (Salmonella enterica serotype Enteritidis, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus) inoculated onto chicken legs. Microbiological counts were determined immediately after dipping (day 0) and every 24 h during 7 days of storage at 10 ± 1 °C. Kinetic data were fitted using the modified Gompertz model. Higher L figures were found in samples treated with TSP, ASC and CA (these samples showed L values ranging from 1.49 ± 0.56 days to 4.06 ± 1.16 days) than in control (untreated) samples (between 0.64 ± 0.58 days and 2.52 ± 2.28 days). These three compounds decreased D (from 2.46 ± 0.51 log10 cfu/cm2 to 6.44 ± 0.42 log10 cfu/cm2) with respect to controls (from 6.32 ± 0.89 log10 cfu/cm2 to 7.74 ± 0.20 log10 cfu/cm2). Similar (P > 0.05) levels of bacteria were observed throughout storage on control legs and on legs treated with PA and CD. ASC showed the highest antimicrobial activity against Salmonella, followed by TSP and CA, while CA proved to be the most effective compound against Gram-positive bacteria, followed by ASC and TSP. A similar behaviour was observed for E. coli in samples treated with of TSP, ASC or CA. These data may help regulatory agencies and poultry producers in the selection of the most effective decontaminants.