Place:
Texas A&M University, College Station, Texas; University of Arkansas; USDA-ARS, College Station, Texas.

Authors:
Drs. Jimmy T. Keeton, Steve Ricke, Robin Anderson, Douglas Miller, and Njongmeta Nenge Lynda Azefor.

Purpose:
Overall objective: Evaluate undeveloped and cost effective pathogen interventions using a multiple hurdle approach suitable for small meat plant operations in an effort to further reduce contamination and growth of pathogens, specifically Salmonella spp., E.coli O157:H7 , and Listeria monocytogenes.

1. 1. Evaluate warm water (control), lactic acid, acidified calcium sulfate (ACS) and/or epsilon-polylysine (EPL) as beef carcasses/trimmings decontamination agents using minimal application procedures to reduce the time and cost of the intervention for small plants that are applied as a warm rinse following standard washing procedures. Different concentrations of the treatments were examined to determine optimal reduction of Salmonella Typhimurium (ST), E. coli O157:H7 (EC), and Listeria monocytogenes (LM).
   2. Determine the residual antimicrobial effects of ACS with and without EPL over time on carcasses/trimmings and selected raw products.
   3. Evaluate the efficacy of the best intervention identified above in two to three small local processing plants and to determine its efficacy as part of the HACCP plan.
   4. Evaluate the bactericidal/bacteriostatic efficacy of the best treatment on a cooked ready-to-eat (RTE) product contaminated with a Listeria cocktail. Due to time limitations, this objective was not covered, but it merits further study.

Summary:
A hot (55°C) spray application of ACS followed sequentially by a hot EPL spray at constant pressure for 15-20 seconds reduced ST, EC, and LM inoculated on the skin-side surface of pre-rigor beef rounds more effectively than a single treatment of ACS, LA, EPL, or warm water alone. A 5 to 10 minute interval was allowed between ACS and EPL applications to simulate carcass processing in a small plant which would not have continuous line speeds as found in high capacity operations. In general, all decontamination treatments, except warm water alone, caused a reduction in ST counts after 7 days of refrigerated storage with the ACS + EPL combination being the most effective antimicrobial treatment against ST. EPL appears to have enhanced antimicrobial activity in combination with acidic antimicrobials. The ACS +EPL combination was the most effective antimicrobial treatment against EC while warm water showed the least reduction. The greatest mean log reductions in ST, EC, and LM on pre-rigor beef rounds were obtained when ACS was applied followed immediately (within 5-10 minutes) by EPL.
 

Benefits:
The results of this study support the use of multiple interventions as a better strategy for pathogen reduction in small processing plants more so than single treatments. It also appears that the combination of antimicrobial agents that express different modes of action for suppressing pathogen growth and the sequential application of different decontamination sprays (e.g., ACS + EPL) are significant factors for obtaining greater reductions in pathogen numbers on beef carcasses at slaughter. This research should also help minimize their operating cost while helping them to ensure food safety and public health protection. Plants will, however, need to validate that their methodology achieves these parameters.