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Keeping Listeria at Bay: The battle that ready-to-eat processors can’t afford to lose. Host: Bill Kinross, Publisher, Meatingplace Moderator: Lisa Keefe, Editor, Meatinglace. Presenter. Harshavardhan Thippareddi,

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keeping listeria at bay the battle that ready to eat processors can t afford to lose

Keeping Listeria at Bay:The battle that ready-to-eat processors can’t afford to lose

Host: Bill Kinross, Publisher, Meatingplace

Moderator: Lisa Keefe, Editor, Meatinglace


Harshavardhan Thippareddi,

Associate Professor of Food Science, Department of Food Science and Technology, University of Nebraska, Lincoln

listeria control old problem new solutions

Listeria Control:Old Problem, New Solutions

Harshavardhan Thippareddi, Ph. D.

Sept 9, 2009

Prepared by: Martin Wiedmann, Ph. D., Cornell University, Ithaca, NY

well known facts
Well Known “Facts”

Human listeriosis can occur as an epidemic or as sporadic cases

L. monocytogenes common in certain/many environments

L. monocytogenes grows at refrigeration temperatures

Infectious dose is high

Growth in foods is usually needed to reach levels likely to cause human disease

Martin Wiedman, Cornell University

well known facts5
Human exposure is common

Majority (ca. 99%) of human listeriosis cases are foodborne

Potentially long incubation period (7-60 days)

Human listeriosis affects predominantly elderly and immunocompromised people, pregnant women and newborns

Well Known “Facts”

Martin Wiedman, Cornell University

the fda csfan usda fsis cdc risk assessment highlights
The FDA-CSFAN, USDA-FSIS, & CDC Risk Assessment – Highlights

Most human listeriosis cases in US appear to be caused be contaminated deli meats

RTE deli meats – 1,598 cases

Pasteurized milk – 90 cases

High fat and other dairy products – 56 cases

Not-reheated frankfurters – 31 cases

Cooked ready-to-eat crustaceans – 2.8 cases

Smoked seafoods 1.3 cases

Fruits and vegetables – 1.1 cases

prevalence of listeria monocytogenes on rte meat and poultry products
Prevalence Of Listeria Monocytogenes On RTE Meat And Poultry Products*

Percent Positives

*FSIS results of ready-to-eat products analyzed for Listeria monocytogenes

human listeriosis trends
Human Listeriosis - Trends

listeria monocytogenes prevalence on rte meat and poultry 2008
Listeria Monocytogenes Prevalence(%) On RTE Meat And Poultry, 2008

challenges towards continuous reduction of human listeriosis
Challenges Towards Continuous Reduction Of Human Listeriosis

LM is common throughout the food chain

A single magic bullet will not work

Focusing on one product (RTE deli meats) at one point (processing) does not seem to work

usda fsis final rule rte processing establishments
USDA-FSIS Final Rule –RTE Processing Establishments

Establishments producing post-lethality exposed RTE product must comply with requirements included in one of the following alternatives (§430.4)

Alternative 1:Use post-lethality treatment AND an antimicrobial agent or process

Alternative 2: Use post-lethality treatment OR an antimicrobial agent or process

Alternative 3: Use sanitation measures ONLY

physical post lethality treatments
Physical Post-lethality Treatments



Submersion in hot water

Radiant oven heating

High Pressure Processing

thermal surface pasteurization systems for rte meat products
Thermal (Surface) Pasteurization Systems for RTE Meat Products

Meat product type and composition

Whole muscle vs. restructured product - product surface characteristics

Thermal properties

Product packaging

Packaged vs. non-packaged

Film thickness and material

Product orientation & package design

Single vs. double layer – hot dogs

Sliced product – deli type products

product orientation effects
Product Orientation Effects



Separated Franks






Courtesy: Alkar

product orientation effects16
Product Orientation Effects

Turkey breast

Roast beef


Courtesy: Alkar

thermal surface pasteurization systems for rte meat products17
Thermal (Surface) Pasteurization Systems for RTE Meat Products

Hot water-based systems

Steam-based systems

Non-condensing steam

Condensing saturated steam

Flash steam system

high hydrostatic pressure systems
High Hydrostatic Pressure Systems

Non-thermal intervention technology

Minimal quality changes

Can be combined with other treatments such as heat

Pressures in the range of 250 MPa (36,260 PSI) to 600 MPa (87,023 PSI)

100 MPa=14,504 PSI

high hydrostatic pressure treatment factors controlling application
High Hydrostatic Pressure Treatment – Factors Controlling Application

Product type and composition

Processing time and temperature

Types of microorganisms to be inactivated

antimicrobial agents lethality treatments
Antimicrobial Agents – Lethality Treatments

Acidic calcium sulfate

Acidified sodium chlorite

Peracetic acid

Lauric arginate

ε- polylysine

antimicrobial agents lethality treatments28
Antimicrobial Agents – Lethality Treatments

Liquid smoke fractions

Listeria phages

Octanoic acid

Ozone (ozonated water)

acidic calcium sulfate
Acidic Calcium Sulfate

Nunez et al., 2004

acidic calcium sulfate30
Acidic Calcium Sulfate

Nunez et al., 2004

acidified sodium chlorite
Acidified Sodium Chlorite

Luchansky et al. 2006

model system polylysine
Model System – Ε- Polylysine

Geornaras et al., 2005

organic acids salts
Organic Acids Salts

Approved for meat product use

Sodium or Potassium salts of lactic acid

Sodium acetate or diacetate

Sodium citrate buffered with citric acid to pH 5.6

Live bacteria – Canbiocin

Levulinate (not commercialized yet)


This Project was funded through a grant from the National Integrated Food Safety Initiative (Special emphasis grant No. 2005-51110-03278) of the Cooperative State Research, Education and Extension Service, U. S. Dept. of Agriculture


John N. Butts,

Vice President of Research,

Land O’ Frost

data analysis investigation and corrective action

Data Analysis, Investigation and Corrective Action

“Follow the data trail to the source but always be alert and aware to the organism’s ubiquitous presence and pervasive nature.”

John Butts

Land O’ Frost

Meatingplace Webinar

Sept 2009

commitment model
Commitment Model

Resistant – don’t believe it has value

Accepting – why not

“Buy-in” – we will do it

Engagement – involved in solution

Commitment – hold self and others accountable for achieving results

sources of ls in high risk rte area
Sources of Ls in High-Risk RTE Area

Transferred from Zone 4 area outside of the High-Risk RTE area

Homeless, but looking for a harborage location

Typically found with a transfer point monitoring positive

Growth niches within High-Risk RTE area

This means they are established, and have found a protective home in equipment or facility.

They may exist in a transient home such as rework pans, trash containers or other difficult to clean mobile container / environment.

transfer points vs niches
Transfer Points vs Niches

Many positive sites found during monitoring are not growth niches. They are transfer points (i.e., a product handler’s gloved hands, floor sample in high traffic pathway).

Transfer points are not growth niches because the organism is eliminated during the cleaning and sanitizing process.

growth niches

Locations harboring the organism after the routine sanitation process for that area has been completed.


  • Hollow roller on conveyor transporting food product
    • Hollow rollers not disassembled cleaned and sanitized or heat treated in a manner to eliminate any contaminating organisms can become growth niches.

Growth Niches

Hollow roller with solid stainless steel shaft in center (almost press fit).

When center shaft removed organic matter is evident.

growth niches49

Must either be designed out of the system or managed as a part of the process.

Design Examples

Equipment is redesigned to eliminate or seal hollow areas

Hollow areas of equipment (e.g., frames, rollers) must be eliminated where possible or permanently sealed (caulking not acceptable). Bolts, studs, mounting plates, brackets, junction boxes, name plates, end caps, sleeves and other such items must be continuously welded to the surface of the equipment and not attached via drilled and tapped holes.

AMI Equipment Design Task Force

growth niches50
Growth Niches

Minimize with process control techniques

The potential to support growth still exists within the machine, part or area

Whenever this becomes the chosen path remember to implement methods that will hold the gains with turnover in both hourly and management ranks.

growth niches51
Growth Niches

Examples of how to minimize with process control techniques

Disassemble clean and sanitize

Heat sanitize

Cook in oven or smokehouse

Cover with tarp and inject steam

Place in COP tank


Seek and Destroy Process

Normal cleaning and


Observe flood


Are all parts and

components being

Observe assembly


sanitized (chemical

or heat)?

Observe Post assembly sanitizer


Observe normal setup and

Are GMP's

start up activities


Stop operation before product

is placed on the line

Disassemble to normal daily

sanitation level

Disassemble any remaining

Inspect and swab

machine components

any suspect areas

Clean and flood or heat sanitize all

disassembled line components

Evidence of



Are cleaning

Is degree of






If APC growth is supported then

If area is Ls positive then it

the suspect area is a potential

is a growth niche

growth niche


Time Study

Locating a Transfer Vector

The Time Study typically starts during setup and assembly . Samples will be taken as workers and product come to the line, repeated after line is running then every 2 hrs thereafter

A Time Study consists of sampling the line components and every thing that comes to the line over a period of time

swat team sampling
Swat Team Sampling

Sample during an idle period after sanitation, before production i.e. Saturday when no production is running

Sample large areas using sponges or gauze.

Sample areas not typically sampled during routine sampling

We found a transient growth niche using this method – COP basket handle


Mike DeSmet,

Vice President of Food Safety,

West Liberty Foods


Scope: It Takes More Than One

There is no one magic bullet.

There is no one department responsible.

Attitude must start from the top one down.

For every one dollar spent up front, multiple dollars are saved later.

No one is immune.


Multiple Hurdle Approach

Building Design/Physical Barriers

Chemical Interventions

Preventive Programs

Product Design/Handling


Verification Activities


Building Design/Physical Barriers

Each product slicing cell has separate positive pressure, air handling system.

HEPA air filtering systems keep with our clean room focus.

Separate slicing cells prevent cross contamination.

Encapsulated suits to prevent cross contamination from employees.


Building Design/Physical Barriers

Separate drain system in each slicing cell with capability of back flooding each drain system.

Ceilings, floors and walls are designed for easy cleaning and sanitizing.

Exposed product production areas are targeted to <38°F.

Design eliminates cardboard and wood from entering exposed product areas.


Chemical Interventions


Sanitizer challenge studies

Rotating Sanitizers

Equipment Fogging

Choosing the correct cleaners and sanitizers for your equipment, your environment and the organism.


Preventive Programs

Equipment audits/repair

Deep cleaning programs (see next 2 slides for examples)

Use of indicator organisms to identify potential niches

GMP audits

Maintenance PM’s

Maintenance Tool Cleaning


Operator Side Spindle Cover




Cover removed

When removed this cover exposed the spindle to allow for cleaning. This cover is removed and cleaned with a Solvaxx solution once a week.


Flip Flop Electrical Cabinet

Operator side

Non-operator side

These cabinets are opened up and inspected weekly. These areas can be carefully cleaned with a Wypall lightly saturated with isopropyl alcohol by a qualified member of the maintenance department.


Product Design/Handling

Proper Cooking

Antimicrobial Ingredients

Modified Atmosphere Packaging


Shelf Life Determination

Temperature Control (cold chain management)



Partnered with Iowa State

Use of Visual Aids

Food Safety Certification as a pre-hire concept

GAP Training (Getting Acquainted Period) successive classes throughout the first 90 days

Annual Re-training


Verification Activities

Strong Listeria program

>3500 Listeria species swabs per month company wide

Zone 1 (conveyors, slicers, product beds)

Zone 2 – indirect contact (on off buttons, framework, etc.)


Verification Activities

Zone 3 environmental (floors, ceilings walls)

Zone 4 adjacent to RTE areas (employee welfare areas, hallways, dry storage)

Every line, every week

Random product sampling

Rapid detection methods


It Never Ends

The listeria control system is a never ending process.

Constant changes due to continuous education, extensive training and monitoring processes.

Watching for new technology.

Utilize Trade organizations as valuable resource for latest topics and technical expertise.

Utilize your chemical representatives and equipment representatives.


Sharing Technology

Growing concept that Food Safety is not proprietary.

When one company stumbles we are all affected in the eyes of the consumer.

WLF and IA State teamed up to sponsor a food safety conference to share our training program with everyone.

for more information
For More Information

Harshavardhan Thippareddi:

John N. Butts:

Mike DeSmet:

Bill Kinross:

Lisa M. Keefe:

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