Inactivation of Inactivation of Listeria Listeria monocytogenesmonocytogenes,,

E. ColiE. Coli O157:H7 and O157:H7 and SalmonellaSalmonellain Frozen Ground Beef Pattiesin Frozen Ground Beef Pattiesby Electron Beam Irradiationby Electron Beam Irradiation

ABC Research CorporationJames “Ken” Kennedy, Ph.D.Director, Research Microbiology

.

Conducted for National Cattlemen’s Beef Association

ObjectiveObjective

To determine the inactivation rates and reduction of Listeria monocytogenes, Salmonella typhimurium and E. coli O157:H7 in Vacuum Packaged, Frozen Ground Beef Patties by doses of 1.1 to 4.4 kyG of electron beam irradiation.

MethodologyMethodology

Product: • Ground Beef (15% fat) fabricated at Univ.of

Florida Department of Animal Sciences • Inoculated, formed into patties, frozen,

vacuum and shrink packaged at ABC Research Corp.

Test Microorganisms: • Listeria monocytogenes (ATCC 19115,

Serotype 4B) • Salmonella typhimurium (ATCC 14028) • E. coli O157:H7 (MF1847)

Methodology Methodology continued

Sample Inoculation/Preparation: •Each microorganism separately inoculated into product at

high (10,000-1,000,000/g) or low (10-10,000/g) levels • Product formed into patties, frozen and vacuum/shrink

packaged in an irradiation approved barrier film

Irradiation Treatment: •Frozen patties irradiated by e-beam at “Florida

Accelerator Services and Technology,” Gainesville, FL •Irradiation dosages of 1.1, 2.2, 3.3, or 4.4 kGy via one to

four passes through the irradiation unit

Inactivation of Low Inoculum Inactivation of Low Inoculum Levels of PathogensLevels of Pathogens

Counts (per gram)

Dose (kGy) Listeria Salmonella E. coli

monocytogenes typhimurium O157:H7

0 20 -1,600 30 - 380 30 - 45,000

1.1 <10 <10 <10 - 50

2.2 <10 <10 <10

3.3 <10 <10 <10

4.4 <10 <10 <10

Pathogen ReductionsPathogen Reductions (High Inoculum Level)

Percentage (%) Reductions

1.1 kGy 2.2 kGy

Listeria monocytogenes 86.8 - 97.2 >98.2 - >99.97

Salmonella typhimurium 82.2 - 99.0 >99.0 - >99.94

E. coli O157:H7 98.5 - 99.9 >99.96 - >99.998

Pathogen ReductionsPathogen Reductions (Low Inoculum Level)

Percentage (%) Reductions

1.1 kGy 2.2 kGy

Listeria monocytogenes >56.3 - >99.4 >56.3 - >99.4

Salmonella typhimurium >67.6 - >97.4 >67.6 - >97.4

E. coli O157:H7 >67.6 - 99.9 >67.6 - >99.98

Summary of PathogenSummary of PathogenInactivation RatesInactivation Rates

• Microbial inactivation quantitatively described by:

D10 value dose in kiloGrays required to inactivate

90% of the microbial population

D10-Values (kGy) in Raw Red Meats

NCBA Gr. Beef Study Literature

Listeria mono. 0.72 - 1.25 0.45 - 1.21

Salmonella 0.69 - 1.18 0.55 - 1.28

E. coli O157:H7 0.38 - 0.60 0.24 - 0.88

ConclusionConclusion

Electron beam irradiation was effective in reducing pathogen levels in frozen ground beef patties at low doses (1.1 – 2.2kGy) and may serve as an additional intervention method to enhance the safety of fresh ground beef products.