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Microbiology of Cooked Meats

Microbiology of Cooked Meats. Aubrey F. Mendonca Dept. of Food Science & Human Nutrition Iowa State University 7 th Annual Thermal Processing of RTE Meat Products The Ohio State University March 28-30, 2006. Outline. Sources of microbial contamination in meat

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Microbiology of Cooked Meats

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  1. Microbiology of Cooked Meats Aubrey F. Mendonca Dept. of Food Science & Human Nutrition Iowa State University 7th Annual Thermal Processing of RTE Meat Products The Ohio State University March 28-30, 2006

  2. Outline • Sources of microbial contamination in meat • Effects of heating on microorganisms • Factors affecting microbial growth • Pathogenic bacteria: characteristics

  3. Sources of Microbial Contamination in Fresh Meat • Animal’s environment • Animal itself

  4. Sources of Microbial Contamination in Fresh Meat • Slaughter facilities

  5. Microbial contamination of meat continues during preparation of primal, sub-primal, and retail cuts Surface of whole cuts Throughout ground products

  6. Some Further Processing Activities • Heating, packaging, chilling, freezing, wholesale & retail distribution

  7. Procedures Involved in Further Processing Activities • Aimed at reducing or preventing microbial growth and further contamination - Temperature control - GMP - Proper sanitation

  8. Heating of Meats • 65-71 OC (150-160 OF) destroys almost all vegetative cells • Survivors: • Thermoduric bacteria:Lactobacillus, Micrococcus, & Enterococcus spp. • Spores : Bacillus spp & Clostridium spp.

  9. Spoilage by microorganisms that survive heating: eg. souring, milky exudate, gas production

  10. Heating of Meats • Most vegetative cells are killed • Heat shock of spores • Spores triggered to germinate

  11. Heating of Meats • Rapid cooling of cooked meats important to prevent germination and outgrowth of Clostridiumperfringens spores

  12. Inadequate Heating • More microbial survivors • sub-lethally injured pathogens • development of heat resistance

  13. Sublethally Heat-injured Pathogens • Insidious problem • difficult to detect • some are sensitive to oxygen • can repair injury and regain pathogenicity

  14. Factors Affecting Microbial Growth in Meats • Intrinsic - part of the meat product itself • Extrinsic - associated with the storage environment

  15. Intrinsic Factors • Nutrient availability • water activity • pH (acid, neutral, alkaline) • antimicrobial agents

  16. Extrinsic Factors • storage temperature • gaseous atmosphere • relative humidity

  17. Hurdle Technology • “barrier concept” • use of two or more factors for control of microbial growth

  18. Use of Multiple Hurdles in a Ham-type Product • salt, nitrite, phosphates • heating/smoking • vacuum-packaging • refrigeration temperature

  19. Considerations for Effective Application of Hurdle Technology • know characteristics of pathogens and spoilage organisms • balance microbial safety and sensory quality

  20. Some Important Foodborne Pathogens • Listeria monocytogenes • Salmonella • Escherichia coli O157:H7 • Campylobacter jejuni • Staphylococcus aureus • Clostridium perfringens • Clostridium botulinum

  21. Food-Related Illness and Death in US OrganismEstm. CasesDeaths Campylobacter 2,453,926 2,454 (0.1%) Salmonella 1,412,498 11,017 (0.8%) C. perfringens 248,520 124 (0.05%) S. aureus 185,060 37 (0.02%) E. coli O157:H7 73,480 609 (0.83%) L. monocytogenes 2,518 503 (20%) C. botulinum 58 4 (8.6%) (CDC Sept-Oct 1999)

  22. Listeria monocytogenes: Sources • Soil and water • Animals • Humans • Foods - raw & cooked meat and poultry products - dairy products - vegetables

  23. Species of Listeria • L. monocytogenes -- Pathogenic • L. innocua -- NP • L. ivanovii -- NP • L. seeligeri -- NP • L. welshimeri -- NP • L. grayi -- NP • L. murrayi -- NP

  24. L. monocytogenes can cause: • Flu-like symptoms • meningitis • perinatal septicemia • abortion/still birth

  25. Persons who are most susceptible to listeriosis • Neonates • Elderly • pregnant women • immunocompromised patients

  26. Listeria monocytogenes • approx. 2,518 cases per year • 20-30% mortality rate

  27. L. monocytogenes: Growth Limitations Min Optm Max temp (OC) 1.0 37 45 pH 4.4 7.0 9.4 aW 0.92 0.99 >0.99 NaCl concentration (up to 9.0 %) oxygen: (facultative)

  28. Listeriosis Outbreak in US (1998-1999) • Hot dogs and sliced luncheon meats • 15 million lbs product recalled • Cost $50,000,000 • Disease reported in 16 states - 102 cases - 21 deaths (5 miscarriages) - serotype 4b

  29. Listeriosis Outbreak in US (2000) • Deli turkey meat • Disease reported in 10 states • 29 cases • 4 deaths • 3 miscarriages/stillbirths

  30. Listeriosis Outbreak in US (2002) • Sliceable turkey deli meat • 27.4 million lbs of fresh & frozen RTE turkey & chicken products recalled • Disease reported in 8 states • 46 cases • 7 deaths • 3 stillbirths/miscarriages

  31. Listeria monocytogenes Infectious dose for humans?

  32. FSIS Sampling of RTE Products forL. monocytogenes (1989 to present) ProductNo. Tested% + ve Jerky 575 0.7 L.D. Sausages 3099 1.6 Uncured poultry 6055 2.4 Beef roast 4900 3.1 Salads & spreads 3619 3.4 S.D.Sausages 4980 4.4 Luncheon meat 1360 5.7

  33. Salmonella

  34. Salmonella • about 2000 serovars • source - warm blooded animals, birds, and reptiles (eg. pet turtles) • causes foodborne infection • infectious dose -- 106 - 107/g • heat-sensitive

  35. Salmonella: Growth Limitations Min Optm Max temp (OC) 5.2 35-43 46.2 pH 3.8 7-7.5 9.5 aW 0.94 0.99 >0.99

  36. FSIS Sampling of RTE Products for Salmonella (1993-1996) ProductNo. Tested% + ve Jerky 177 0.6 L.D. Sausages 1624 1.2 Uncured poultry 2636 2.5 Beef roast 1972 2.8 Salads & spreads 2004 3.0 S.D.Sausages 2247 4.5 Luncheon meat 571 6.5

  37. Escherichia coli O157:H7

  38. E. coli O157:H7 • Source - cattle, deer, sheep • 1982 - recognized as foodborne pathogen • Symptoms - bloody diarrhea - Haemolytic uraemic syndrome (HUS) - Thrombotic thrombocytopenic pupura (TTP)

  39. E. coli O157:H7: Growth Limitations Min Optm Max temp (OC) 7-8 35-40 44-46 pH 4.4 6.7 9.0 aW 0.95 0.995 ----

  40. E. coli O157:H7 • 1993 outbreak in Pacific Northwest from undercooked hamburger State No. Cases Deaths Washington >500 4 Idaho 14 0 Nevada 58 0 California 34 1

  41. E. coli O157:H7 • Nov. 1994 USDA Regulation • Raw ground beef contaminated with E. coli O157:H7 is considered adulterated

  42. E. coli O157:H7 • 1994 Outbreak linked to Dry Salami - 23 cases - 1 case of HUS • Validation of Dry Sausage procedures for destroying 5 logs of E. coli O157:H7

  43. Foods implicated in E. coli O157:H7 Disease Outbreaks • Undercooked ground beef • Fermented sausage • Apple cider • Sprouts • Cheese curds • Mayonnaise • Water

  44. E. coli O157:H7 • Easily destroyed by heat • Low infectious dose (<100 cells)

  45. Clostridium perfringens

  46. Clostridium perfringens • Source - soil, feces • produces heat resistant spores • spores survive normal cooking procedures • Anaerobic but not a strict anaerobe

  47. Clostridium perfringens • Toxin is not produced in food but in the intestine • Diarrhea --- within 6-24 h • Transmission - inadequately heated or reheated meat products especially meat stews - improper cooling of cooked foods

  48. C. perfringens: Growth limitations Min Optm Max temp (OC) 12 43-47 50 pH 5.5-5.8 7.2 8-9 aW 0.93 0.95-0.96 ----

  49. FSIS Compliance Guidelines for Cooling Heat Treated Meat & Poultry Products (Jan 1999) • Cooling requirements for uncured and cured, fully cooked, partially cooked and char-marked meat patties • Designed to prevent growth of C. perfringens spores that survive heating

  50. Clostridium perfringens • Further research is needed to determine rate of outgrowth of spores during chilling of cured and uncured meat and poultry products

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