Control of Listeria monocytogenes


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Control of Listeria monocytogenes

  1. 1. Control of Listeriamonocytogenes<br />Kelly J.K. Getty, Ph.D.<br />Kansas State University<br />
  2. 2. Control and Growth of Listeriamonocytogenes<br />Packaging effects on jerky, snack sticks, kippered beef steak, and turkey tenders<br />Intrinsic factors in sliced deli turkey roast<br />Effect of salts <br />
  3. 3. Package Systems and Storage Times Serve as Post-Lethality Controls for Listeria monocytogenes on Whole Muscle Beef Jerky and Pork and Beef Smoked Sausage Sticks<br />J. Food Prot. (2011) 74:188-192<br />Support provided by the USDA CSREES under agreement 2003-34211-12998, the Kansas Department of Commerce and Housing, Agriculture Marketing Division, and Oberto Sausage Company <br />
  4. 4. Background<br />A “zero” tolerance policy is applied by USDA to Lm in ready-to-eat meat and poultry products<br />USDA defines a post lethality treatment as a process that reduces Lm by at least 1 log<br />Research has shown packaging can generate a 1 log Lm reduction following 1 or more weeks of storage at ambient temperature<br />
  5. 5. Objective<br />To determine the effect of packaging environment and storage time on reducing Listeriamonocytogeneson whole muscle beef jerky and pork and beef smoked sausage sticks<br />
  7. 7. Experimental Design<br />Jerky cut into square pieces<br />Dipped into Lminoculum <br />Dry Jerky ~ 1 h<br />Enumeration of initial level of Lm<br />Four packaging treatments applied<br />Measure Water Activity<br />Plates incubated for 24 hours at 35˚C<br />Hold for 24, 48, 72 h and 30 days<br />Enumeration after storage periods<br />Plates incubated for 24 hours at 35˚C<br />
  8. 8. Inoculum Procedures <br />Five strains of Lm were used to prepare a cocktail inoculum.<br />One loopful of each strain placed into 9 mL test tubes of tryptic soy broth (TSB). Incubated for 24 hours at 35˚C.<br />From the test tubes, 0.5 mL was pipetted into 200 mL jars of TSB. Incubated for 24 hours at 35˚C<br />Contents of jars were combined to create 1 L 5 strain cocktail<br />
  9. 9. Sampling Procedures<br />Jerky was aseptically cut into 4 x 4 cm2 pieces.<br />Dipped for 1 minute in 5 strain cocktail of Lm.<br />Allowed to air dry for 1 hour.<br />Packaged using four treatments: <br />- Nitrogen Flush with - Vacuum (VAC) <br /> oxygen scavenger (NFOS)<br />- Heat Seal with - Heat seal (HS)<br /> oxygen scavenger (HSOS)<br />Samples held for 0, 24, 48, 72 h and 30 days<br />
  10. 10. Enumeration of Listeriamonocytogenes<br />4 x 4 cm2 was placed in a stomacher bag and 34 mL of peptone water was added.<br />Samples were stomached for 1 minute.<br />Serial dilutions were prepared. <br />0.1 mL of each dilution was spread plated onto modified Oxford medium (MOX) plates.<br />Plates were incubated at 35˚C for 24 hours.<br />
  11. 11. results<br />
  12. 12. Mean Log Reduction of Lm on Beef Jerky Packaged in Different Packaging Environments and Stored at Ambient Temperature<br />de<br />abcde Means having a different superscript differ (P<0.05)<br />f<br />f<br />f<br />f<br />f<br />f<br />e<br />de<br />cd<br />c<br />bc<br />bc<br />bc<br />bc<br />a<br />a<br />
  13. 13. Mean Lm Log Reduction (CFU/cm2) on Smoked Sausage Sticks Packaged in Different Packaging Environments<br />b<br />b<br />b<br />a<br />
  14. 14. Mean Lm Log Reduction (CFU/cm2) on Smoked Sausage Sticks During Ambient Temperature Storage<br />c<br />b<br />ab<br />a<br />
  15. 15. Conclusions<br />Jerky - Using these packaging environments in conjunction with at least a 48 h storage time is a Lm post lethality control treatment.<br />Snack Sticks - Using these packaging environments in conjunction with at least a 24 h storage time is a Lm post lethality control treatment.<br />
  16. 16. Effect of Packaging and Storage Time on Survival of Listeriamonocytogeneson Kippered Beef Steak and Turkey Tenders <br />J. Food Sci. (accepted)<br />
  17. 17. Objective<br />Determine the effect of packaging environment and short term storage time on reducing Listeriamonocytogenesin meat or poultry snacks<br />
  18. 18. Materials and Methods<br /><ul><li>Two commercially obtained products:
  19. 19. Kippered Beef Steak:
  20. 20. Lean beef components, ground and formed
  21. 21. Cured Product
  22. 22. Turkey Tenders:
  23. 23. Whole muscle turkey breast, sliced and marinated
  24. 24. Uncured Product</li></li></ul><li>Experimental Design<br />4 packaging treatments X 4 storage times X 2 samples/treatment X 3 replications<br />Packaging treatments:<br /><ul><li>Heat sealed (HS)
  25. 25. Heat seal with oxygen scavenger (HSOS)
  26. 26. Nitrogen flushed with oxygen scavenger (NFOS)
  27. 27. Vacuum (VAC)</li></ul>Storage times:<br /><ul><li>0, 24, 48, or 72 h</li></li></ul><li>Procedures<br />Product cut into squares or used as intact strips<br />Dip into Lm inoculum for 1 min<br />Dry Product ~1 h at ambient temperature<br />Package in 1 of 4 treatments<br />Measure aw<br />Spread plate for initial Lm level (time 0 h)<br />Hold for 24, 48, or 72 h at ambient temperature<br />Incubate plates for 48 h at 35˚C<br />Spread plate following storage time <br />
  28. 28. Product Characteristics<br />
  29. 29. Mean aw During Ambient Time Storage<br />
  30. 30. Mean log reductions (CFU/cm2) of Listeriamonocytogenes in kippered beef steak<br />
  31. 31. Mean log reductions (CFU/cm2) of Listeriamonocytogenes in turkey tenders<br />
  32. 32. Implications<br />Processors of these products could use a combination of vacuum or nitrogen flushing and a hold time of 24 h prior to shipping to reduce potential Lm by at least 1 log.<br />However, processors should be encouraged to hold product for at least 72 h to enhance the margin of safety.<br />
  33. 33. Effect of Intrinsic Factors on Growth of Listeriamonocytogenes in Sliced Deli Turkey Roast<br />We acknowledge Cargill Meat Solutions for support of this project. <br />
  34. 34. Objectives<br />Evaluate how sodium nitrite concentration, percent pump, and salt type affect the growth of L. monocytogenesin vacuum packaged sliced turkey deli roast stored at 4°C for up to 91 days.<br />
  35. 35. Materials and Methods<br />Sliced turkey deli roasts were formulated with 1.5% sodium chloride (NaCl) or 0.75% NaCl and 0.75% potassium chloride, 10% or 45% pump, and 0 ppm or 200 ppm sodium nitrite (NaNO2) for a total of eight treatments.<br />Turkey slices were inoculated with a 5-strain Lm cocktail (inoculated) or peptone water (control) and then vacuum packaged.<br />
  36. 36. Materials and Methods<br />After 0, 7, 14, 21, 28, 42, 63, and 91 days of 4C storage, treatments were sampled for Lm populations on modified oxford media (MOX) and aerobic plate count (APC).<br />pH, water activity (aw), residual nitrite, and percent fat, moisture, protein, and sodium was measured using control treatments for each sampling day.<br />
  37. 37. Results<br />Lm populations in turkey deli roast slices containing 200 ppm NaNO2 were 0.70 to 2.39 log CFU/cm2 lower (P<0.05) compared with products formulated with 0 ppm NaNO2.<br />Using 10% pump reduced (P<0.05) Lm populations by 0.62 to 1.50 log CFU/cm2 on days 7 to 28 and at day 63 compared with products pumped to 45%. <br />
  38. 38. Results<br />Incorporating 1.5% NaCl or 0.75% NaCl and 0.75% KCl into turkey formulations did not affect (P>0.05) Lm or APC growth during 91 days of 4C storage.<br />
  39. 39. Conclusion<br />Growth of Lm and APC were reduced with higher nitrite concentrations and lower percent pump, while salt type did not affect Lm growth during 4°C storage.<br />
  40. 40. Effect of Salt and Salt Replacements on Listeriamonocytogenes Growth in a Broth System<br />Nigel Harper, Ph.D. candidate<br />
  41. 41. Objectives<br />To determine the effect that different salts have on the growth of L. monocytogenes<br />NaCl<br />KCl<br />CaCl2<br />MgCl2<br />Replacement salt<br />Sea salt <br />
  42. 42. Materials and Methods<br />Four chemical salts [sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl2) and magnesium chloride (MgCl2)] and two industrial salts (replacement salt and sea salt) at 0.5%, 1%, and 2.5.<br />Listeriaenrichment broth used in this study was made without the sodium chloride and dipotassium phosphate.<br />
  43. 43. Results<br />Results showed that MgCl2 actually induced growth (P > 0.05) compared to control (no salt) and other salt solutions.<br />The industrial salts both yielded greater (P > 0.05) populations than the controls.<br />These results show that replacing pure NaCl with a salt that contains magnesium could cause outgrowth of Lm.<br />
  44. 44. Next Steps<br />Effect of salts on ground beef, ground turkey, and ground pork<br />Effects of salts in more complex meat systems<br />
  45. 45. Acknowledgements<br />Dr. Elizabeth Boyle<br />Dr. James Higgins<br />Dr. Ann Brackenridge, Cargill Meat Solutions<br />Bruce Barry, Oberto Sausage Company<br />Kim Uppal, Oberto Sausage Company<br />Tyler Axman<br />Shayne Lobaton-Sulabo<br />Nigel Harper<br />TawnyaRoenbaugh<br />Dr. Melissa Weber<br />