Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 16, 1998
Publication Date: N/A
Interpretive Summary: The effect of lactic acid, acetic acid, trisodium phosphate, 162 deg F water, and 89 deg F water washes on bacteria placed on beef carcass surfaces before they were treated, and then converted to ground beef, was determined. The monitoring of bacteria in the ground beef was continued for 21 days of refrigerated (38 deg F) or 3 days of abusive (54 deg F) storage. Cattle feces containing various low levels of Listeria innocua, Salmonella typhimurium, E. coli O157:H7, and Clostridium sporogenes was used to contaminate the carcass surface. In general, growth of these four bacteria, and of total bacteria, was suppressed or not observed when lactic acid or acetic acid treatments were used. Bacteria introduced to beef surfaces before the tissue had received a trisodium phosphate treatment demonstrated some growth suppression in the ground beef. Water washes of 89 or 162 deg F offered little growth suppression of pathogens during the storage periods. The use of a final lactic or acetic acid wash during the processing of beef carcasses offers some long lasting protection against growth of potentially harmful bacteria accidentally introduced into ground beef from the surfaces of carcasses contaminated during processing.
Technical Abstract: The long term effectiveness of several beef carcass surface tissue (BCT) wash interventions on the 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. 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 deg C at the tissue surface), or water (WW; 32 +/- 2 deg C at the tissue surface). A control group was left untreated. After treatments, BCT was held at 4 deg C for 24 h then ground. The ground beef was packaged and incubated at 4 (21 d) or 12 deg C (3 d). AA-treated samples held at 12 deg C for 3 d 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 (21 d) or 12 deg C (3 d), 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, but the populations were generally higher than those observed in any of the chemical antimicrobial-treated samples. These trends continued throughout all storage conditions over time. Results from this study indicate use of carcass interventions, especially antimicrobial compounds, presently available to the slaughter industry will lower bacterial counts in ground beef.