Identifying and Controlling Listeria in Food Processing

FacilitiesJames L. Marsden, Ph.D.

Executive Director – Food SafetyChipotle Mexican Grill

Listeria monocytogenes• Higher heat resistance than most foodborne bacterial

pathogens• Survives freezing and drying• Can survive and grow in refrigerated, packaged, ready-to-

eat products (RTE) and resists high salt levels, nitrite, and acid

• Can grow in vacuum packaged products • Causes Listeriosis• Variable virulence

Controlling Listeria monocytogenes in Plant Environments• Lm contamination usually occurs in the post-processing environment of

food plants• Lm is very hardy and survives in the cold and wet environments found in

many food processing plants• Control of Lm requires the maintenance of strict sanitary controls • Elimination of Lm from RTE environments may also require technologies

that go far beyond traditional cleaning and sanitation

Three Components of Listeria Control

1. Inactivation• Listeria monocytogenes that may be present in food and other

ingredients must be inactivated during the manufacturing process. This often occurs in during thermal processing.

2. Post-Processing Control• The product must then be protected from recontamination up

until the time it’s packaged. This means that post-processing and packaging areas in the plant must be maintained as true RTE zones and kept Listeria free.

3. Prevent Outgrowth• For products that support outgrowth of Lm, the third objective is

to formulate in a way that prevents outgrowth during storage and distribution.

Manufacturing Processes for Inactivation of Listeria monocytogenes

• Thermal Processes• Fermented Processes – Salt, pH, Drying• High Pressure Processing (HPP)

Thermal Processing and Inactivation of Listeria monocytogenes• COMPLIANCE GUIDELINES TO CONTROL LISTERIA MONOCYTOGENES IN

POST-LETHALITY EXPOSED READY-TO-EAT MEAT AND POULTRY PRODUCTS

http://www.fsis.usda.gov/wps/wcm/connect/8cf5e6a1-1f52-406c-bd8b e3608a5a3c7e/Lm_Rule_Compliance_Guidelines_May_2006.pdf?MOD=AJPERES

• Thermal inactivation studies of Escherichia coli O157:H7, Salmonella,and Listeria monocytogenes in ready-to-eat chicken-fried beef patties, Osaili, T.; Griffis, C. L.; Martin, E. M.; Beard, B. L.; Keener, A.; Marcy, J. A.Journal of Food Protection, Number 5, May 2006, pp. 984-1216, pp. 1080-1086(7)

• Thermal Inactivation of Salmonella and Listeria Monocytogenes in Ground Chicken Thigh/Leg Meat and Skin, R.Y. Murphy, T. Osaili, L.K. Duncan and J.A. Marcy, Poultry Science (2004) 83 (7):1218-1225.doi: 10.1093/ps/83.7.1218

Control of Listeria monocytogenes• Post-processing application of chemical solutions for control of Listeria

monocytogenes, cultured under different conditions, on commercial smoked sausage formulated with and without potassium lactate–sodium diacetate, l. Geornaras, P.N. Skandamis, K.E. Belke, J.A. Scanga,P.A. Kendall, G.C. Smith, and J.N. Sofos, Food Microbiology, Vol. 23, Issue 8, December 2006, Pages 762–771

• Organic Acids and Their Salts as Dipping Solutions To Control Listeria monocytogenes Inoculated following Processing of Sliced Pork Bologna Stored at 4°C in Vacuum Packages. Samelis, John; Sofos, John N.; Kain, Mindy L.; Scanga, John A.; Belk, Keith E.; Smith, Gary C. Journal of Food Protection, Number 11, November 2001, pp. 1653-1877, pp. 1722-1729(8)

• Modeling the Growth of Listeria monocytogenes in Cured Ready-to-Eat Processed Meat Products by Manipulation of Sodium Chloride, Sodium Diacetate, Potassium Lactate, and Product Moisture Content. Seman, D. L.; Borger, A. C.; Meyer, J. D.; Hall, P. A.; Milkowski, A. L. Journal of Food Protection, Number 4, April 2002, pp. 595-725, pp. 651-658(8)

High Pressure Processing and Control of Listeria monocytogenes

• High-pressure processing and antimicrobial biodegradable packaging to control Listeria monocytogenes during storage of cooked ham, B. Marcos, T. Aymerich, J.M. Monfort, M. Garriga. Food Microbiology, Vol 25, Issue 1, February 2008, Pages 177–182

• Effects of high-pressure processing on Listeria monocytogenes, spoilage microflora and multiple compound quality indices in chilled cold-smoked salmon, R. Lakshmanan and P. Dalgaard, Journal of Applied Microbiology, Vol. 96, Issue 2, pages 398–408, February 2004

Controlling Lm in Plant Environments

1. Conduct a Microbiological Mapping Audit • Identify harborage sites and potential vectors of Lm

contamination

2. Control Drains and Floors • Evaluate drain design and construction to assure that sanitary

conditions can be maintained• Specialized Sanitizers to eliminate biofilms and provide an on-

going antimicrobial effect• Use Silver Dihydrogen Citrate. (SDC) provides residual Silver

ions in drains and drain systems, reducing thepotential for Lm contamination

Controlling Lm in Plant Environments

• Control Drains and Floors• Maintain sanitary conditions and consider direct application of

sanitizers that will remain in place during operations• Control vectors of contamination involving employee and visitor

footwear• Prevent Drain blockages that can result in contaminated water

backup and positive air pressure. Both can introduce microbial pathogens into processing environments

• Verify control through rigorous environmental testing of drains and floors

Controlling Lm in Plant Environments• Food Contact Surfaces

• Use validated cleaning and sanitation chemicals and procedures to assure control of Lm

• Proven most effective sanitizers against Lm are quaternary ammonia compounds, chlorine solutions, iodophors, Silver Dihydrogen Citrate and products containing Peroxyacetic acid

• Rotate between alkaline and acid based sanitizers• Periodically use a sanitizer specifically to address biofilms • Use dry clean-up procedures for cleaning at breaks and mid-shift

(possibly discontinue the use of high pressure hoses during processing operations)

• Consider the use of aqueous ozone as a Sanitizer in RTE areas

• Verify through rigorous environmentalfor Lm

Controlling Lm in Plant Environments

• Control of Airborne/Particle Borne Vectors of Contamination• Establish positive air pressure movement out of RTE areas• Consider the use of Advanced Oxidation technologies to pre-treat

incoming air to contain low levels of vapor hydrogen peroxide. This will inactivate Lm on surfaces and on particles that may be present in RTE areas

• Regularly clean and sanitize air cooling units in RTE areas• Use antimicrobials in drop pans• Consider using Ozone generators in unoccupied

spaces throughout the plant. This can be donein RTE areas as wells as warehouses,maintenance areas on dry goods storage rooms

• SDC is a stabilized silver ion complex in which a single silver ion is weakly bound to a citrate ion.

• SDC utilizes a multiple prong attack against the cell wall and DNA of microorganisms. SDC targets an organism’s cell wall (cell membrane) due to the high affinity of ionic silver to membrane bound proteins.

• In addition, bacteria view the citric acid in SDC as a food source, allowing SDC to easily enter the microorganism. SDC then SDC binds to DNA and intracellular proteins causing irreversible damage to the DNA and protein structure.

• Allows for disinfection on food contact surfacescoupled with residual protection on treatedsurfaces

Controlling Lm in Plant EnvironmentsSilver Dihydrogen Citrate Technology

Controlling Lm in Plant EnvironmentsSilver Dihydrogen Citrate Technology

• Successful Plant Decontamination• FDA approved eradication plan implementing SDC-based cleaner and

disinfectant/sanitizer in specialty food manufacturer closed due to two separate Lm contamination events

• Previous interventions unable to eradicate Lm from equipment and environment

• After treatment with SDC based products, plant and packaging equipment released by FDA for manufacturing FDA regulated products

• SDC highly effective at eliminating Lm in contaminated environments and preventingcontamination in processing environments

Controlling Lm in Plant Environments

OH·

H2O2/ O3/UV

O3/UV

H2O2/ O3

Photocatalyticoxidation

H2O2/ UV

Advanced Oxidation Technology

Controlling Lm in Plant Environments

How it works

Contaminant

Ozone

ROS

HydrogenPeroxide

Water

CarbonDioxide

Advanced Oxidation Technology

Controlling Lm in Plant Environments

• USDA Guidance http://www.fsis.usda.gov/wps/wcm/connect/5f890501-9270-4ef0-9199-908464fc34ca/38_IM_RTE_Sanitation.pdf?MOD=AJPERES

Applications for Secondary Inhibitors• Secondary Inhibitors

• Organic acids or other natural antimicrobials• Functional food ingredients• Reduce initial microbial load• Prevent outgrowth• Protect food from cross-contamination

and re-contamination• Make food safer

Post Process Pasteurization in the Consumer Package Using HPP or Thermal Processing

• High Hydrostatic Pressure• Results in a 5+ log reduction for Salmonella, Listeria

monocytogenes and E. coli O157:H7• Allows individual package processing hence improve their

safety and prevent cross-contamination during packaging• considered a processing aid and does not require labeling

Post Process Pasteurization in Consumer Package Using HPP or Thermal Processing• Inhibition of Listeria monocytogenes and Salmonella by Natural

Antimicrobials and High Hydrostatic Pressure in Sliced Cooked Ham, Aymerich, Teresa; Jofré, Anna; Garriga, Margarita; Hugas, Marta, Journal of Food Protection, Number 1, January 2005, pp. 4-207, pp. 173-177(5)• A synergistic effect to inhibit a cocktail of Listeria monocytogenes CTC1010, CTC1011,

and CTC1034 was observed between potassium lactate, high hydrostatic pressure (400 MPa, 17°C, 10 min), and low storage temperature when sliced cooked ham was stored for 84 days at 1°C

Post Process Pasteurization in Consumer Package Using HPP or Thermal Processing• Effect of Prepackage and Postpackage Pasteurization on

Postprocess Elimination of Listeria monocytogenes on Deli Turkey Products, Muriana, Peter; Gande, Nanditha; Robertson, Will; Jordan, Brad; Mitra, Suparna, Journal of Food Protection, Number 11, November 2004, pp. 2368-2626, pp. 2472-2479(8)• Prepackage pasteurization provided 2.0 to 2.8 log reductions when processed for

60 s and 2.8 to 3.8 log reductions when processed for 75 s. An improved radiant oven provided 3.53 (60 s) and 4.76 (75 s) log reductions of L. monocytogenes. No positive samples were detected after enrichment when 40 samples of deli turkey (4 to 4.5 kg) undersides were inoculated at low levels and processed for 75 s. Submersed water postpackage pasteurization provided 1.95 to 3.0 log reductions when processed for 2, 3, 4, or 5 min, and combinations of the two processes gave 3.0 to 4.0 log inactivation of L. monocytogenes using either 60 + 60 s or 60 + 90 s for the prepackage and postpackage pasteurization processes, respectively.

Control of Lm in Food Plant Environments Summary

• Controlling Listeria requires extraordinary efforts and state-of-the-art technologies. Traditional sanitation isn’t enough

• Each and every potential vector of contamination must be controlled

• Continuous application of antimicrobial technologies is required

• Systems should be in place to prevent outgrowth or eliminate post-process Lm contamination through a pasteurization step