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Food Safety Consortium Update By Dr. Ted Kramer
The Food Safety Consortium was organized in 1988 between the University of Arkansas, Iowa State University (ISU) and Kansas State University (KSU). It links three states with traditional strengths in three major food commodities: Arkansas for poultry, Iowa for pork and Kansas for beef cattle. The three states have recognized strengths in the production as well as in the harvesting and processing of these respective commodities.
The mission of the Consortium is fourfold. 1. To determine the optimal points of intervention - we would call it today Critical Control Points - for the control of microbiologic or chemical hazards.
2. To advance and develop technology for the rapid identification of infectious agents and toxins.
3. To develop risk monitoring techniques to detect hazards in the distribution chain.
4. To develop a statistical framework to evaluate health risks in the food chain.
We might add to these original objectives a recent orientation of the Consortium toward preharvest hazard analysis, and intensive involvement in the study of the economics of food safety.
I. A primary goal of the Consortium’s recent activities has been chemical, physical and biologic pathogen reduction in meat and meat products.
A. Chemical interventions investigated by Consortium researchers comprise
The team led by Dr. Curt Kastner (KSU) has determined the benefits of lactic acid rinse before packaging beef had a significant decontaminating effect. Similar beneficial decontaminating effects of organic acids were documented earlier for poultry by Mike Slavik of the University of Arkansas and also by Elsa Murano of Iowa State. Some specific benefits:
Current studies at Kansas State University (KSU) have documented long-term beneficial effects of lactic acid spray of subprimals. Gluconic acid was found to have decontaminating effects parallel to those of lactic acid. Research at Iowa State University (ISU) indicated that most acid-adapted Salmonella remained susceptible to organic acid decontamination.
Three percent lactic acid sprays on subprimal cuts of beef are more effective than treatment of the entire carcass in extending shelf life.
Ozone treatment during immersion chilling of poultry drumsticks extended shelf life by one to two days and significantly reduced coliform levels.
Ten percent trisodium phosphate sprayed on chilled poultry carcasses effectively reduced bacterial pathogens.
Cetyl piridinium chloride was found to be an effective antiseptic that prevented attachment of bacteria to poultry and other meat products. This commonly used antiseptic in mouth washes and throat lozenges should find ready public acceptance.
B. Physical methods of decontamination were investigated
Scalding temperature was found to be an important factor in preventing bacterial attachment to chicken skin. However, more is not always better; attachment of bacteria increased as superficial layers were removed when scalding temperature was raised from the 50’s to 60ºC.
Application of electric current to the chill water in poultry processing was highly effective in reducing E. coli and Salmonella bacteria in a dose-dependent manner.
Removal of meat from poultry carcasses without evisceration, especially when done in combination with antibacterial rinses greatly reduced bacterial contamination of poultry meat.
Irradiation studies were performed with Iowa State’s CIRCE III Linear Electron Accelerator. Mathematical models were developed to predict the growth of the spoilage microflora in low dose irradiated ground pork. Irradiation at medium doses (1.8 to 2.0 kGy dose) reduced significantly the numbers of Salmonella typhimurium and Listeria monocytogenes on cooked chops and cured hams. Irradiation was particularly effective in combination with salt and nitrite used for ham curing.
Sociologic studies on public acceptance of irradiated food suggested willingness to pay for safer food. However, survey results indicated that negative descriptions about the irradiation process made a greater impact on the public than descriptions of the benefits of the process.
Irradiation studies were also conducted on five viruses. A radiation dose of 3 kGy was ineffective in decreasing virus levels, except for large DNA viruses (such as herpesviruses), and even 10 kGy did not produce viral sterilization.
C. Biologic agents were also investigated as means of reduction of pathogenic and spoilage microbes
One of the biologic methods of microbial spoilage control investigated by Consortium researcher Wanda Lyon is the application of bacteriocins, heat-stable bacteriostatic proteins produced by certain harmless bacteria. Her most recent work focused on the incorporation of these bacteriocins into liposomes, in order to protect them from the proteolytic enzymes present in meat.
II. A second major focus of Consortium researchers was the identification and rapid detection of pathogenic agents on meat and meat products, and preharvest sources.
Identification systems based on numerical taxonomy, immunologic tests and molecular genetic procedures - PCR - have been effectively used by Consortium researchers to detect carcass and meat pathogenic bacteria.
Campylobacter jejuni and the closely related Arcobacter are important health hazards in poultry and pork. While Campylobacter was predominant in poultry, a high prevalence of Arcobacter was found by Consortium researcher Irene Wesley from the USDA National Animal Disease Center. She identified Arcobacters from 89 percent of ground pork by a combination of cultures and gene dot blot testing.
University of Arkansas researcher Mike Slavik is working on Arcobacter detection from poultry. The Arkansas team led by Michael Johnson has developed an immunoblot microcolony test for the detection of Listeria in foods.
Another Arkansas Consortium team of Donald Cave and Kathleen D. Eisenbach examined restriction length polymorphism of three important Salmonellae of poultry: S. typhimurium, S .enteritidis and S. heidelberg, and found remarkable homogeneity between isolates of S. enteritidis and S. heidelberg.
A rapid method for direct immunoblot detection of Salmonella from carcass lymph nodes is under investigation in cooperation with a commercial interest.
New techniques for the detection of E. coli O157:H7 and of the SL toxin are being evaluated by Lee Ann Thomas at the USDA National Veterinary Service Laboratory and at the National Animal Disease Center. At Kansas State University, researchers DYC Fung and KF Chuang have developed selective media with organic dyes for the visual differentiation of E. coli O157:H7 from the multiplicity of other E. coli serotypes.
Iowa State researchers determined that healthy pig livers can destroy 95 percent of a heavy inoculum of Salmonella in 3 hours. However, livers subjected to the acute phase reaction - also known as septic shock - permitted exponential growth of Salmonella.
The Consortium has a number of projects focused on the detection of carrier animals, particularly concerning healthy swine carriers of salmonellosis. One study seeks to determine the potential of isolated early weaning of pigs for the elimination of Salmonella. Another study seeks to determine the value of an ELISA assay for the detection of latently Salmonella infected swine.
Stress in swine caused plasmid mediated antimicrobial drug resistant bacteria to move from the upper to the lower digestive tract. Significantly more tetracycline and b lactam antibiotic resistant bacteria were found from stressed than from unstressed swine. Additional observations by Iowa State researchers determined differences between fecal and carcass-recovered antibiotic resistance patterns, and differences between resistance patterns of the upper and lower digestive tracts.
Sulfa drugs and antibiotics are another area of active investigation by the Consortium. Sulfadimethoxine depletion in swine occurred after 16-23 days of treatment in drinking water for five days at 12.5mg/lb. Tribrissen depletion to nondetectability occurred from 16 to 30 days after intramuscular injection for three days at a dose of 24mg/lb.
Looking into the future, the Consortium plans a major study to determine the sources of pathogenic bacteria on swine carcasses - whether of carrier swine origin, of environmental origin, or of human handler origin.
A similar study in beef will seek the source(s) of pathogenic bacteria in processed beef from the carcass through the processing chain.
III. The Food Safety Consortium publishes the Proceedings of its Annual Meeting which is held in Kansas City in October of each year.
For a copy of the Proceedings, please contact Dr. George Beran, Department of Microbiology, Immunology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011. Phone: 515-294-7630, FAX: 515-294-8500. Email address: gberan@iastate.edu
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