Application of an Automated Hydrophobic Grid Membrane Filter Interpreter System at a Poultry Abattoir

The performance of a system to measure broiler carcass hygiene was investigated in the abattoir environment. The system involved: whole carcass rinses aided by a mechanical carcass shaker; filtration of rinse solutions though hydrophobic grid membrane filters (HGMF) (ISO-GRID^R, QA Laboratories Ltd.); and use of an automated HGMF interpreter. The interpreter recorded culture results in units of most probable number (MPN) of aerobic bacteria, in electronic data files (MI-100 HGMF Interpreter System, Richard Brancker Research Ltd.). Set-up and operation of the system by government inspection staff at an abattoir ran relatively smoothly with minimal interference to normal plant operation. The system demonstrated good repeatability in measuring log₁₀ most probable number per gram of carcass (LgMPN/g), between repeat readings of the same filters (r=0.993 p<0.001), and good repeatability between repeat filters within the same carcass rinses (r=0.970 p<0.001). Overall, the LgMPN/g ranged from 0.258 to 3.955 with a mean of 2.276 and a variance of 0.324. These corresponded to MPN/g counts in the range of 2 to 9000 and a geometric mean of 188.8 MPN/g. A regression model was developed to investigate poultry supplier and abattoir effects on the variability of counts. A significant supplier effect was observed. The addition of two more carcass showers located just after the venting machine along the evisceration line was not associated with a change in carcass hygiene.