Survival of Pseudomonas fluorescens on beef carcass surfaces in a commercial abattoir

The influence of a commercial chilling process (18 h at 10 degrees C followed by up to 78 h at 2 degrees C) on Pseudomonas fluorescens inoculated on beef carcass surfaces at four sites, neck (NE), outside round (OR), brisket (BR) and foreshank/brisket (FB) before chilling ("hot inoculated") or after chilling for 24h ("cold inoculated") was investigated. Pseudomonas counts increased significantly at all sites on "hot inoculated" carcasses during storage, but on "cold inoculated" carcasses, counts declined or remained unchanged. On hot and cold inoculated carcasses, differences in Pseudomonas growth or survival were demonstrated between sites. No clear relationships were observed between Pseudomonas growth or survival and chiller relative humidity (RH) or surface water activity (a(w)) at the different sites. These results were unexpected, and are discussed in relation to environmental factors that affect the growth/survival of P. fluorescens on carcass surfaces during chilling i.e. temperature, RH, and the relationship of these parameters to surface water activity (a(w)).