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-DEGREES-C

The long-term effectiveness of several beef-carcass surface-tissue (BC T) wash interventions on the microbiology of ground beef produced from this tissue was determined. BCT was inoculated with bovine feces cont aining one of two different levels (ca. 4 or 6 log CFU/ml) of Escheric hia coli O157:H7, Listeria innocua, Salmonella typhimurium, and Clostr idium sporogenes. The BCT was then subjected to one of several treatme nt 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 treatme nts, 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 degr ees C for 3 days. AA-treated samples held at 12 degrees C for 3 days y ielded significantly lower aerobic plate counts than the control and a lso yielded the lowest levels of pseudomonads when compared to other s ample groups. After being held at 4 degrees C for 21 days or 12 degree s 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 con trol. Ground beef produced from tissue treated with HW yielded lower p opulations 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 conti nued throughout all storage conditions over time. Results from this st udy indicate that the use of carcass interventions, especially antimic robial compounds, presently available to the slaughter industry will l ower bacterial counts in ground beef.