Changes in Escherichia coli O157:H7 numbers during holding on excised lean, fascia and fat beef surfaces at different temperatures.

Aim: To investigate changes in Escherichia coli O157:H7 numbers on excised beef carcass surfaces over 72 h at different temperatures.

Methods And Results: Excised lean meat, fascia and fat were inoculated with E. coli O157:H7 and held in an environmental chamber for 72 h, at air speed 0.5 m s(-1), relative humidity (RH) 90%, and temperatures 4, 8 and 12 degrees C. On lean, pathogen counts increased significantly at 12 degrees C. On fascia, significant reductions in counts occurred at 4 and 8 degrees C. Pathogen numbers were significantly reduced on fat at 4, 8 and 12 degrees C (64 h). Counts on fat were significantly less at all temperatures, compared to lean or fascia and surface water activity, a(w), decreased significantly over time on fat at 4 degrees C. Significant decreases in surface pH values were recorded on all meat substrates.

Conclusions: The survival of E. coli O157:H7 varied in relation to the meat substrate and the holding temperature. Reductions in counts on fat surfaces appeared to be related to low surface a(w) values. No relationship between pathogen survival and surface pH was established.

Significance And Impact Of The Study: The use of excised meat pieces in an environmental cabinet offers a more flexible approach to determining the use of different chilling regimes in the production of safe meat.