Background

It is widely understood that hides of beef cattle contaminated with fecal material play a primary role in carcass contamination during the slaughtering process. If contamination does occur, it typically happens during the dehiding step. Previous research has shown that hides and errors in slaughtering and dressing are the primary vehicles of beef carcass contamination.

Contamination of carcasses with Escherichia coli O157:H7 is a major concern to the beef industry due to the risks of human illness from eating beef products contaminated with E. coli O157:H7. The U.S. Department of Agriculture (USDA) Food Safety Inspection Service (FSIS) has established a zero-tolerance policy for the presence of E. coli O157:H7 on beef carcasses. As a result, the beef industry continues to research a variety of safety intervention methods to ensure the safest product possible for consumers.

To address these issues, the beef harvesting industry has adopted several carcass antimicrobial intervention technologies, such as steam pasteurization and acid rinses. However, no validated processes involving the decontamination of hides prior to dehiding are currently commercially utilized. A commercial laboratory (Sandia National Laboratories) has developed a product (Decon Foam-200) that has been shown to be very effective against bacterial vegetative cells, spores and viruses. The formulation (DF-200) is non-toxic, non-corrosive and forms a highly stable foam. A significant volume of research has been completed at Kansas State University, demonstrating a high degree of activity against foodborne spoilage and pathogenic agents, including E. coli O157:H7, Salmonella and Listeria monocytogenes.  

Two studies were conducted, in which the objectives of the first were to evaluate DF-200 Foam’s effectiveness at reducing natural microbial flora counts on cattle hides. The second study was designed to test the most effective treatments on inoculated hide samples. 

Methodology

Study 1

The objective of this study was to generate basic data on native bacterial populations on cattle hides to determine adequate treatment parameters for the inoculated study. Hide samples were obtained (1 foot x 1 foot) from a commercial beef processing facility. Researchers cut approximately 40 to 50 circular pieces from each hide sample. A subset of the hide samples were prepared to exhibit a high level of fecal contamination (“tag”) by applying fresh fecal material. Fecal material was collected from a feedlot and was smeared on the hide samples to simulate the amount of hide contamination that occurs in feedlots. The non-inoculated hide samples were treated with either:

1. Hot and cold water pressure wash
2. Hot and cold DF-200 liquid wash
3. Hot and cold water drench
4. Hot and cold DF-200 liquid drench
5. Dry DF-200 foam
6. Pre-moistened hides followed by DF-200 foam. 

Study 2 

Bacterial cultures of five strains of Salmonella spp., and five strains of Escherichia coli O157:H7 were mixed together in equal parts and were applied to hide samples. After inoculation, the hide samples were treated with one of three treatments:

1. 15 seconds of pressurized rinse with cold water and five minutes rest
2. One second of pressurized cold DF-200 Foam and five minutes of rest, or
3. 15 seconds pressurized rinse with cold water, plus one second pressurized cold DF-200 Foam and five minutes of rest. 

The treated samples were analyzed for E. coli O157:H7 and Salmonella spp.

Findings

Study 1
The untreated control hide samples had average aerobic plate counts of 4.5 log colony forming units (CFU)/cm² and had no counts for E. coli or coliforms. The untreated control hide samples with “tag” added had average aerobic plate counts of 7.0 log CFU/cm², E. coli counts of 4.2 log CFU/cm², and coliform counts of 4.2 log CFU/cm².

Study 2
The hide samples were inoculated with E. coli O157:H7 at an average level of 5.3 log CFU/cm² and for Salmonella at an average level of 4.9 log CFU/cm². Reductions in both E. coli O157:H7 and Salmonella counts were similar for each treatment. The water pressure wash was the least effective treatment against E. coli O157:H7 and Salmonella populations with reductions of only 0.36 and 0.34, respectively. The foam DF-200 treatment by itself or combined with water, had similar reduction in counts for both pathogens. The DF-200 foam treatment resulted in reductions in E. coli O157:H7 and Salmonella spp. counts of 3.44 and 2.89, respectively. A water pressure treatment followed by a DF-200 foam treatment resulted in reductions of E. coli O157:H7 and Salmonella spp. counts of 3.04 and 3.02, respectively.

Implications

The application of DF-200 foam on cattle hides was effective at reducing microbiological counts of E. coli O157:H7 and Salmonella spp. by three log CFU/cm². the DF-200 foam was just as effective at reducing microbiological counts by itself as it was with the addition of a water prewash. However, DF-200 was not effective on hides with large amounts of “tag” present. The addition of a mechanical action may be necessary to better remove this organic matter prior to DF-200 application to achieve greater effectiveness.