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Listeria monocytogenes transfer during slicing of delicatessen meats
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Listeria monocytogenes transfer during slicing of delicatessen meats

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  • 1. Dr. Elliot Ryser Department of Food Science and Human Nutrition Michigan State University East Lansing, MI September 14, 2011
  • 2.  
  • 3.  
  • 4.  
  • 5. Listeriosis Outbreaks Traced to Delicatessen-Sliced Turkey
    • May – Dec 2000: 16.9 million lbs recalled
      • 29 cases
      • 4 deaths
      • 3 miscarriages
    • June 2001: 16 cases of acute febrile gastroenteritis (no deaths)
    • October 2002: 27.4 million lbs recalled
      • 46 cases
      • 7 deaths
      • 3 miscarriages
  • 6.  
  • 7. Predicted Annual Listeriosis Cases (Log Scale) from Different Food Categories in the United States (FDA/FSIS, 2003) DM = Deli meats ; FNR = Frankfurters (not reheated); P= Pâté and Meat Spreads; UM= Unpasteurized Fluid Milk; SS= Smoked Seafood; CR = Cooked Ready-To-Eat Crustaceans; HFD = High Fat and Other Dairy Products; SUC = Soft Unripened Cheese; PM = Pasteurized Fluid Milk; FSC = Fresh Soft Cheese; FR = Frankfurters (reheated); PF = Preserved Fish; RS = Raw Seafood; F = Fruits; DFS= Dry/Semi-dry Fermented Sausages; SSC = Semi-soft Cheese; SRC = Soft Ripened Cheese; V = Vegetables; DS = Deli-type Salads; IC= Ice Cream and Frozen Dairy Products; PC = Processed Cheese; CD = Cultured Milk Products; HC = Hard Cheese.
  • 8. USDA Listeria Alternatives Implemented October 2003
  • 9. Deli Meat Recalls, 1994 - 2005 0 2 4 6 8 10 12 1994 1995 1996 1997 1999 2000 2001 2002 2003 2004 2005 2006 Year Number of recalls Ham Turkey Chicken Beef Corned Beef Other > 84 recalls > 53 million lbs
  • 10. Year Number of Recalls Recalled Product (lbs) 2006 1 375 2007 3 8600 2008 7 16,000 2009 3 39,000 2010 6 170,000 2011 6 9,500
  • 11.
    • Gombas et al., 2003
      • 0.4% of manufacturer-sliced
      • 2.7% of delicatessen-sliced
    • Draughon et al., 2006
      • 0.2% of manufacturer-sliced
      • 1.4% of delicatessen-sliced
    • Deli-sliced meat still 7 times more likely to be contaminated
    • Sales
      • 24.4% manufacturer-sliced
      • 75.6% delicatessen-sliced
  • 12. Current Concerns  ~ 1,600 listeriosis cases annually including ~255 fatalities  ~ 290 of 1,600 listeriosis cases from deli meats: ~ 42 pre-sliced , ~ 248 deli-sliced  ~ 46 fatalities from deli meats  ~ 6 fatalities from pre-sliced  ~ 40 fatalities from deli-sliced
  • 13.
    • Raw materials
    • Manufacture
      • Slicing
      • Food contact surfaces
      • Packaging
    • Retail
      • Slicing
      • Product handling
      • Deli environment
    • Consumer
      • Refrigerator
      • Slicing
      • Product handling
      • Environment
    Contamination primarily occurs after processing
  • 14. Distribution of Listeria spp. in a Local Deli/Restaurant ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Location Listeria L. seeligeri L. innocua L. mono ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Basement 35 20 7 8 Kitchen 50 27 11 12 Front line 7 7 0 0 Sandwich line 20 9 8 3 Seafood case 5 0 5 0 Cheese case 9 4 5 0 Meat case 7 4 3 0 Display floor 10 3 2 5 Open back case 1 1 0 0 Board (meat, cheese) 10 1 9 0 Slicer (Hobart, sandwich line) 8 7 0 1 Slicer (Bizerba, deli) 5 4 0 1 Slicer (Bizerba, cheese) 2 2 0 0 Slicer ( Hobart, basement sandwich line ) 0 0 0 0 Slicer (Hobart), basement, cheese 1 1 0 0 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Total 170 90 50 30 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  • 15. _________________________________________________ Location Listeria pos/ # of positive visits # tested (%) Listeria LM _______________________________________________________ Basement 35/70 (50) 13 4 Kitchen 50/84 (60) 14 6 Front line 7/42 (17) 4 0 Sandwich line 20/56 (36) 14 3 Cases(meat, cheese 42/154 (27) 13 5 floor, seafood) Slicer (H,SL) 8/70 (11) 4 1 Slicer 1(B,deli) 5/70 (7) 2 1 Slicer 2(B,deli) 2/70 (3) 1 0 Slicer 1/103 (1) 1 0 (Cheese, basement) Slicer 0/70 (0) 0 0 (meat, basement ) _________________________________________________________________
  • 16.
    • 1. Transfer of L. monocytogenes to different components of a deli slicer
    • 2. L. monocytogenes transfer to deli meats during slicing
    • 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats
    • 4. Development of a risk assessment for L. monocytogenes in deli meat
  • 17. Back plate Table Guard front Guard back Collection area Blade Guard holder
  • 18. Hobart Berkel Food Residue Behind the Blade
  • 19.
    • Product inoculation and slicing
      • 1-cm strip on surface of product inoculated to contain L. monocytogenes at 10 8 CFU/cm 2
      • Held 1 hour at 5 °C before slicing
    • Sampling method after each slice
      • 1-ply composite tissue method (Vorst et al. 2004. J. Food Prot. 67:2212-2217)
  • 20.  
  • 21.  
  • 22.
    • Other components of the slicer will be contaminated if a positive product is sliced on a commercial machine, not just the product being sliced
  • 23.
    • 1. Transfer of L. monocytogenes to different components of a deli slicer
    • 2. L. monocytogenes transfer to deli meats during slicing
    • 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats
    • 4. Development of a risk assessment for L. monocytogenes in deli meat
  • 24.  
  • 25.
      • Slicer blade to product
      • Product to slicer blade to product
  • 26.
    • Slicer blade inoculated with a turkey slurry to contain ~10 3 , 10 5 , and 10 8 Lm CFU/blade
    • Held 1 hour at 21 – 23 ° C before slicing
    • 3 replicates
  • 27.  
  • 28.  
  • 29.
    • 10 3 CFU/blade
      • Turkey: Slice 28
      • Bologna: Slice 20
      • Salami: Slice 23
    • Except for salami, 99% of the original L. monocytogenes population is transferred in the first 10-15 slices, but much is unaccounted for.  Assumption is that Listeria is spread into the immediate environment, remains on the blade or dies off  With salami continual transfer likely exceeds 30 slices
  • 30.
    • Products– turkey, salami, bologna
      • Surface inoculated to contain 10 5 and 10 8 CFU/cm 2
      • 1-cm strip on the product surface
      • Held 1 hour at 4.5 °C before slicing
    • Slicer inoculation
      • Inoculated product sliced 5 times to contaminate the blade at approximately 10 3 and 10 5 CFU/blade
    • Product transfer
      • Uninoculated product sliced sequentially
      • 24 - 36 replicates
  • 31.  
  • 32.  
  • 33.
    • Salami followed by salami
      • Slice 30
    • Salami followed by turkey
      • Slice 10
    • Turkey followed by salami
      • Slice 17
  • 34.  
  • 35.
    • 1. Transfer of L. monocytogenes to different components of a deli slicer
    • 2. L. monocytogenes transfer to deli meats during slicing
    • 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats
    • 4. Development of a risk assessment for L. monocytogenes in deli meat
  • 36.  
  • 37.  
  • 38.
    • Conditioning layer: meat, meat exudate
    • Unlikely to meet moisture requirement
      • will rely on RH of the operation and food products for moisture
    • Cleaning and friction from slicer will disrupt biofilms
    • Attached bacteria and food particles likely, but not biofilms
  • 39.
    • Persistent strains of L. monocytogenes attach to food contact surfaces and form biofilms more readily than non-persistent strains
    • Sublethal injury enhances resistance of Listeria to environmental stresses and leads to more persistent strains
  • 40.
    • L. monocytogenes strains
      • Strong and weak biofilm formers
      • Healthy, starved, cold-stressed and chlorine-injured
    • Inoculate to contain ~10 8 CFU/blade
    • Allow to dry, incubate blades in humidity chamber at 78% RH, 22°C, 6 and 24 h
    • 24 replicates for healthy and cold-injured models each, and 36 replicates all others combinations
  • 41. Transfer of Uninjured L. monocytogenes to Salami
  • 42.  
  • 43.
    • 1. Transfer of L. monocytogenes to different components of a deli slicer
    • 2. L. monocytogenes transfer to deli meats during slicing
    • 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats
    • 4. Development of a risk assessment for L. monocytogenes in deli meat
  • 44. Risk Assessment Framework Hazard Identification Exposure Assessment Hazard Characterization [Dose-Response] Risk Characterization Description of the Hazard (agent in the food) And adverse effects What is the probability of consuming contaminated food AND what are the likely numbers of a pathogen in the food at the time of consumption A mathematical model which predicts the probability of an adverse effect from a given dose . • Provides a RISK ESTIMATE • What is the nature and likelihood of the health risk? • Who and how many are likely to become ill? • What are the sources of variability and uncertainty in the information used? Jaykus et al. 2007
  • 45. Contamination Levels at retail (cfu/ g ) Growth in the retail refrigerator Contamination level at consumption (log CFU) / g) Contamination level per serving
    • Lag time
    • Growth rate
    • Storage time
    • Refrigeration
    • temperature
    • Maximum growth
    • Serving size
    • Enumeration data
    • L. monocytogenes
    • distribution in food
    Prevalence Initial contamination level (log cfu/g) Cross contamination during deli slicing Growth in the home refrigerator
    • L. monocytogenes
    • transfer rate
    • product composition
    • type of slicer blade
    Left-over portions
    • % frequency data
    Jaykus et al. 2007
  • 46.
    • Sl icing a contaminated product will lead to contamination of all slicer components
    • > 90% of Listeria transfer from the blade to the product occurs during the first 10-15 slices of delicatessen meats after mechanical or knife slicing
    • Deli meats will “clean” the slicer blade, but with varying effectiveness
  • 47.
    • Additional Factors Impacting Listeria Transfer
    • Product composition
      • Moisture, Fat
    • Product temperature
    • Order in which products are sliced
    • Model and design of the slicer
    • Characteristics of L. monocytogenes
      • Healthy vs. injured
      • Strong or weak biofilm former
  • 48.
    • Avoid the first 10 slices?
    • Do opened packages of non-recalled product pose a significant risk?
  • 49.
      • Dr. Keith L. Vorst
      • Dr. Lindsey Keskinen
      • Dr. Zhinong Yan
      • Dr. Bradley P. Marks
      • Dr. Ewen Todd
      • Dr. Gary Burgess
      • Amanda Benoit
    • Funding
      • FDA
      • USDA-NAFSS
      • USAD-NISFI

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