Bacterial profile of ground beef made from carcass tissue experimentally contaminated with pathogenic and spoilage bacteria before being washed with hot water, alkaline solution, or organic acid and then stored at 4 or 12°C

The long-term effectiveness of several beef-carcass surface-tissue (BCT) wash interventions on the microbiology of ground beef produced from this tissue was determined. BCT was inoculated with bovine feces containing one of two different levels (ca. 4 or 6 log CFU/ml) of Escherichia coli O157:H7, Listeria innocua, Salmonella typhimurium, and Clostridium sporogenes. The BCT was then subjected to one of several treatment washes: 2% (vol/vol) DL-lactic acid (LA), 2% (vol/vol) acetic acid (AA), 12% (wt/vol) trisodium phosphate (TSP), hot water (HW; 74 +/- 2 degrees C at the tissue surface), or water (WW; 32 +/- 2 degrees 0 at the tissue surface). A control group was left untreated. After treatments, BCT was held at 4 degrees C for 24 h and then ground. The ground beef was packaged and incubated at 4 degrees 0. for 21 days or 12 degrees C for 3 days. AA-treated samples held at 12 degrees C for 3 days yielded significantly lower aerobic plate counts than the control and also yielded the lowest levels of pseudomonads when compared to other sample groups. After being held at 4 degrees C for 21 days or 12 degrees C for 3 days, samples treated with antimicrobial compounds had lower or no detectable (<1 CFU/g) levels of E. coli O157:H7, L. innocua, S. typhimurium, and C. sporogenes than beef treated with a WW or the control. Ground beef produced from tissue treated with HW yielded lower populations of these bacteria when compared to WW or untreated control beef, but the populations were generally higher than those observed in any of the antimicrobial chemical-treated samples. These trends continued throughout all storage conditions over time. Results from this study indicate that the use of carcass interventions, especially antimicrobial compounds, presently available to the slaughter industry will lower bacterial counts in ground beef.