COMPARISON OF CONVENTIONAL PLATING METHODS AND PETRIFILM FOR THE RECOVERY OF MICROORGANISMS IN A GROUND-BEEF PROCESSING FACILITY

The objective of this study was to compare recovery of microoganisms f or various beef samples and beef contact surfaces using conventional p our plating techniques and Petrifilm methods. Comparisons for aerobic plate count APC),icl coliform count (CC), and Escherichia coli count ( ECC) were done for 104 fresh or frozen retail cuts and 56 food surface or food contact surfaces. Samples were taken at a midwestern retail g round beef processing plant during a 12-month project. APC comparisons were made for pour plating using Trypticase soy agar versus Aerobic P late Count Petrifilm. CC and ECC were compared for pour plating using violet red bile + MUG agar versus E. coli Petrifilm. Overall, paired t tests revealed a significantly higher recovery for APC from fresh and frozen beef samples using the pour plating technique (P less than or equal to 0.05). No significant differences (P > 0.05) were observed fo r CC from fresh and frozen meat samples. Recovery of E. coli from many beef samples was better using Petrifilm. Significantly higher ECCs we re observed from fresh and frozen meat samples using Petrifilm compare d to the pour plating technique (P less than or equal to 0.05). For fo od surfaces and food contact surfaces, a comparison between pour plati ng and Petrifilm was done for aerobic plate count. No significant diff erences (P > 0.05) in recovery could be found between methods. A compa rison between neutralizing buffer and letheen broth for recovery of su rface microorganisms was done for both the APC pour plating method and APC Petrifilm. In both cases, recovery when using letheen broth was s ignificantly (P less than or equal to 0.05) higher than neutralizing b uffer. Because it is convenient and gave comparative results, Petrifil m offers a good alternative for environmental microbial testing and re d meat product testing.