Title: EFFECTS OF ACETIC, LACTIC ACID AND TRISODIUM PHOSPHATE ON THE MICROFLORA OFREFRIGERATED BEEF CARCASS SURFACE TISSUE INOCULATED WITH ESCHERICHIA COLI O157:H7, LISTERIA INNOCUA, AND CLOSTRIDIUM SPOROGENES
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 31, 1996
Publication Date: N/A
Interpretive Summary: Acetic and lactic acid (organic acids), as well as trisodium phosphate are chemicals that have been approved for use in the beef processing industry to decontaminate beef carcasses. Since meat is not consumed immediately after the application of these carcass decontamination agents, this experiment was designed to test their long range effectiveness. Fresh cattle feces containing spoilage and other naturally occurring bacteria were spiked with foodborne pathogens and pathogen models (E. coli O157:H7, Listeria innocua, and Clostridium sporogenes), then used to contaminate beef carcass surface tissue prior to all treatment methods. The effect of the chemical treatments on the meat was tracked over time by monitoring the levels of E. coli O157:H7, L. innocua, and C. sporogenes along with total bacteria, and spoilage bacteria at selected times during refrigerated storage for 21 days. All treatments initially reduced total bacteria, spoilage bacteria, E. coli O157:H7, L. innocua, and C. sporogenes as much as 99.99 percent. All the acid treatments suppressed any re-growth of E. coli O157:H7, L. innocua, and C. sporogenes for the duration of the refrigerated 21-day storage period. Trisodium phosphate treatments were similar to acids in effectiveness for controlling growth of E. coli O157:H7 and C. sporogenes, but were less effective for total bacteria, L. innocua and some spoilage bacteria. These results demonstrate that the beef processing industry can use any of these chemicals to effectively reduce the number of certain pathogenic and spoilage bacteria from beef carcasses during processing and subsequent refrigerated storage.
The microbial profiles of inoculated beef carcass tissue (BCT) were monitored during prolonged refrigerated vacuum packaged storage following antimicrobial treatment. An industrial spray wash cabinet (W) was used to deliver water, 1.5 and 3.0% lactic (LA) or acetic (AA) acid, or 12% trisodium phosphate (TSP) washes. Fresh unaltered bovine feces spiked with antibiotic resistant strains of Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes were used to inoculate BCT prior to all treatments. The effect of treatments on bacterial populations was tracked by monitoring levels of the marked bacteria along with mesophilic aerobic bacteria (APC), lactic acid bacteria (LAB), and pseudomonads for up to 21 days at 5 deg C storage. Initial APC levels of approximately 5.6 log10 CFU/cm**2 were reduced 1.3-2.0 log10 CFU/cm**2 by LA, AA, and TSP treatments. Marked bacteria were reduced to < 1.3 log10 CFU/cm**2, remaining that way throughout 21-day storage. TSP treatments were not different in effectiveness from acids for controlling growth of E. coli O157:H7 and C. sporogenes, but were less effective for APC, L. innocua or LAB. The aerobic bacteria, L. innocua, and LAB had counts >/= 7 log10 CFU/cm**2 by 7 days in all but one case and by 14 days all had counts > 7 log10 CFU/cm**2 on the untreated controls and water washed samples. Treatments generally added a degree of safety regarding the foodborne pathogens and pathogen models used for the present study when beef tissue was stored up to 21 days and in no case did the treatments appear to offer any competitive advantage to select microorganisms on BCT.