An evaluation of simple cleaning methods that may be used in red meat abattoir lairages

Concrete tiles artificially contaminated with field strains of Escherichia coli and Salmonella kedougou, with and without the presence of bovine faecal matter, to simulate visually clean and visually dirty surfaces respectively, were cleaned using a specially designed mechanical rig. Cleaning was carried out using (1) water under mains pressure, (2) water under pressure, (3) water under pressure with a proprietary sanitising agent, (4) steam under pressure and combinations of (5) mains water followed by steam under pressure or (6) water under pressure followed by steam under pressure. Thirty replicates of each of visually clean and visually dirty concrete surfaces were cleaned using each method. Where there was no faecal matter, the use of a proprietary sanitiser at maximum recommended concentration, or the application of steam under pressure gave greater reductions in microbial contamination than the use of mains or a pressure wash. Where the surface was visually contaminated with the faecal material, the use of a pressure wash followed by immediate steam application gave reductions in microbial contamination comparable with the use of a proprietary sanitiser at maximum recommended concentration. The use of steam alone on a visually dirty surface was not an effective means of reducing microbial contamination. A small pilot trial under commercial conditions ranked the efficacy of cleaning treatments as follows: pressure washing followed immediately by steam application was the best method of cleaning a holding pen floor, followed by use of a sanitising agent at the greatest concentration recommended by the manufacturer, and then by pressure washing alone. Pressure washing followed by a delayed steam application appeared to give a poor final result on the surface.