1
Useful Microbiological
Testing in Food Safety &
Quality Management
Katherine M.J. Swanson, Ph.D.
Vice President Food Safety Ecolab
President-Elect IAFP
Arkansas Association for Food Protection
Springdale, AR
September 14, 2011
2
Discussion Topics

International Association for Food Protection greeting

Different tests serve different purposes

Testing for maximum value
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Different Tests Serve Different
Purposes
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Microbial Testing

“Microbial testing” means
different things to different
people
 Reams of data
 Detective game to identify unknown or
causative agent
 Presence/absence or qualitative
reaction that’s observed
 Quantitative measurement of the
microbiological status of a sample or
lot
Presentation focuses on process
control and product acceptance
OR
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The Purpose of a Test Determines:
The target
Indicator or pathogen
The method
Time to results, accuracy, repeatability, etc.
The sample
Environment, line residue, end product, location
collected, size/ number of samples
The frequency
Daily, weekly, monthly, etc. or event triggered
The interpretation Investigational, routine, regulatory, etc.
The action
Rejection, process adjustment, recall, outbreak
investigation, etc.
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International Commission on Microbiological
Specifications for Foods

Founded in 1962 to advance scientific concepts for
government and industry consideration to:
 Reduce foodborne illness
 Facilitate global food trade
 Focus on testing applied to foods

Membership
 6 Academia, 6 Government, 5 Industry from 11 Countries
 All work is voluntary and without honoraria

Partners with FAO, WHO, ILSI, IUFoST, IAFP etc.

Provides advice through books, papers, workshops, etc.
 Advice has no official status
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When & Where to Test for Food
Safety Management

When there is good evidence that:
 There is a microbiological problem
- Food safety or quality
- Historical or current
AND
 Testing will help to control the problem
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Target Organism Examples
ICMSF Hazard Categories
EXAMPLES
Utility
Spoilage, reduced shelf life, no
health concern
Total counts, yeast, mold,
etc.
Indicator
Measure of GHP or process control
Coliforms, generic E. coli,
Enterobacteriaceae, etc.
Moderate
hazard
Not life threatening, short duration,
self limiting, no sequelae
S. aureus, B. cereus, C.
perfringens, Norovirus, etc.
Serious
hazard
Incapacitating, usually not life
threatening
Salmonellae, Shigella
flexneri, Yersinia
enterocolitica, etc.
Severe
hazard
Life threatening, chronic sequelae,
or long duration OR
E. coli O157:H7, C
botulinum toxin or
Cronobacter (infants)
Designed for sensitive subpopulation
From ICMSF Book 7
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Key ICMSF Sampling Plan Terms
n
Number of sample units analyzed
c
Maximum number of sample units with
unsatisfactory test results
m
Level that separates acceptable quality from
marginally acceptable or unacceptable quality
M
Level above which is unsatisfactory or requires
further investigation
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Choosing m and M
m
Relative proportion of
sample units in a lot
No concern
M
Some
concern
Mean log count
Decisive concern
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ICMSF Suggested Sampling Plans
FOR LOT ACCEPTANCE TESTING
Likely Change Before Consumption
Hazard Group
Reduce
No Change
Increase
Utility
Case 1
Case 2
Case 3
n=5, c=3
n=5, c=2
n=5, c=1
Case 4
Case 5
Case 6
n=5, c=3
n=5, c=2
n=5, c=1
Case 7
Case 8
Case 9
n=5, c=2
n=5, c=1
n=10, c=1
Case 10
Case 11
Case 12
n=5, c=0
n=10, c=0
n=20, c=0
Case 13
Case 14
Case 15
n=15, c=0
n=30, c=0
n=60, c=0
Indicator
Analytical
unit = 25g
Moderate
Serious
Severe
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Probability of Acceptance
Sample Size Influence on Probability
of Acceptance
m=0
1.2
74%
n = 15
n = 30
55%
n = 60
86%
1
0.8
0.6
0.4
0.2
0
0
1%
5
10
% Defective
15
20
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Testing to Maximize Value
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Useful Microbial Testing

Identification of contamination sources

Environmental monitoring to identify potential harborage
sites

Utility and indicator organisms to verify effective controls &
trends
 Effective processing
 Effective control of post process contamination

Investigation sampling for problem solving
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Process Example
Process 1
Ingredients
Packaging Line A
Process 2
Packaging Line B
Process 3
What action do you take when an unacceptable result is
found on Line B?
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Result Format Influences Information
Provided
Quantative
Presence/Absence
5
Log (CFU/g)
Positive
Negative
4
3
2
1
0
0
10
Lot Number
20
0
10
Lot Number
20
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5
5
4
4
Log (CFU/g)
Log (CFU/g)
Trend Analysis Can Inform Process
Control
3
2
3
2
1
1
0
0
0
10
0
20
5
4
4
Log (CFU/g)
Log (CFU/g)
5
3
2
3
2
1
1
0
0
10
Lot Number
20
Lot Number
Lot Number
0
10
20
0
10
Lot Number
20
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Testing Considerations

Primary production

Ingredients

In-process

Processing environment

Shelf life

End product
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Book 8 Contents

Part 1-Principles
 Utility of microbial testing for
safety & quality
 Validation of control measures
 Verification of process control
 Verification of environmental
control
 Corrective action to re-establish
control
 Microbial testing in customersupplier relationships

Part 2 – Product Categories
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Meats
Poultry
Seafood
Feed & pet food
Vegetables
Fruits
Spices, dried soups, flavorings
Cereals
Nuts, oilseeds, dried legumes
Cocoa and confectionery
Oil based foods
Sugar, syrups, honey
Beverages
Water
Dairy products
Eggs
Shelf stable, heat treated foods
Infants and young children
Formulated foods
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Primary Production

Included when production conditions
have a major influence on the
microbial quality or safety
 Fruits, vegetables, spices, meat, poultry and
fish products

Examples of samples to consider
 Irrigation water
 Fertilizer
 Feed
 Other on-farm practices
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Ingredient Testing

May be useful for some
applications and not others

Example - cocoa powder:
Used in chocolate, no heat treatment
? Used in ice cream mix that is
subsequently pasteurized

Question
 Is control at the ingredient step
necessary?
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In-Process Testing

Verify a kill step or predict potential recontamination

Examples
 Intermediate product, line residues, tailings,
wash water
 Typically indicators with quantitative results

Questions:
 Is the process needed to control a microbial
concern?
 Is testing needed to verify:
- the process is functioning as intended or
- contamination is not occurring in the process?
32
Processing Environment Testing

Use to verify that the environment is
under appropriate hygienic control

Examples
 Swabs or sponges for equipment or in the
environment
 Rapid testing to verify cleaning & sanitation
adequacy

Identify harborage sites that can
contaminate end product

Frequently, earlier detection of issues
than end product testing

Questions considered:
 Does the environment need to be controlled
to prevent contamination?
 Will testing be beneficial to verify control?
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Shelf Life Testing

Relevant for products subject to microbial spoilage

Purpose – verify microbial stability for the product life cycle

May predict issue before they are experienced in the
market place

Questions considered:
 Is shelf life limited by a microbiological safety or quality concern?
 Is shelf-life testing feasible?
34
End Product Testing

Demonstrate successful application of controls or assess
the status of a lot when no other information exists.

Alternative sampling plans may be appropriate, for
example:
 Fewer samples for on-going surveillance activity
 More samples when investigating significant process deviations or
outbreaks.

Questions considered:
 Is end product testing necessary to verify the overall manufacturing
process?
 Is end product testing relied upon for ensuring the safety or quality of
the lot?
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Example: Dried Ready-to-Eat Cereal
Relative importance
Useful testing
Critical
ingredients
Medium
In-process
High
Test appropriate product residues and in-line samples for
Salmonella. Typical guidance levels:
Salmonella – absent
Processing
environment
High
Test for Salmonella and Enterobacteriaceae in the
processing environment Typical guidance levels:
Enterobacteriaceae – 100-1000 cfu/g
Salmonella – absent
Shelf-life
Not
relevant
Test for mycotoxins if confidence in raw grains is low
Test nuts, cocoa, and other sensitive ingredients with no
subsequent kill step for Salmonella if confidence in supplier
is low.
-
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Example: Dried Ready-to-Eat Cereal (continued)
Relative
importance Useful testing
End
product
High
Testing for Enterobacteriaceae is recommended to verify process
control.
Product
Dried
cereal
Low
Microorganism
Enterobacteriaceae
Analytical
method
ISO
21528-2
Sampling plan & limits/g
Case
n
c
m
M
2
5
2
10
102
Testing for pathogens is not recommended during normal
operation when GHP and HACCP are effective as confirmed by
above tests. When above testing or process deviations indicate a
possible safety issue, test for Salmonella.
Product
Dried
cereals
Sampling plan &
limits/25g
Microorganism
Analytical
method
Case
n
c
m
M
Salmonella
ISO 6579
11
10
0
0
-
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Example: Comminuted Meat
Relative importance
Useful testing
Critical
ingredients
Low to
high
Pre-testing beef trimmings for E. coli O157:H7 may be
useful when confidence in supplier control is low.
In-process
Low
Routine in-process samples are not normally collected.
Samples of meat at various stages of processing can be
used to establish a baseline and understand changes in
the microbial population during processing.
Processing Low
environment
Sample equipment surfaces before start-up to verify
efficacy of cleaning and disinfecting. Typical levels
encountered may vary by surface type.
Shelf life
Routine shelf life testing of refrigerated raw meat is not
recommended. Shelf life testing may be useful to validate
code dates of new retail products or when new packaging
systems are installed.
Low
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Example: Comminuted Meat
(continued)
Relative
importance Useful testing
End
product
Medium
Test freshly packaged product for indicators for on-going process
control and trend analysis using internally developed guidelines.
Levels for processing do not apply during distribution or at retail.
Product
Microorganism
Raw, comminuted
meat
E. coli
Analytica
l method
ISO 16649-2
Sampling plan &
limits/g
Case
4
n c m M
5 0 0
-
Medium Routine testing is not recommended for salmonellae. In regions
where ground beef is a continuing source of E. coli O157:H7 illness,
the following criteria are recommended.
Product
Microorganism
Analytical
method
Ground beef
E. coli O157:H7
ISO 16654
Sampling plan &
limits/25g
Case
n
c m M
14
30
0 0
-
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Microbial Sampling Summary
 Testing
safety “into” products usually does not work
because of sampling probability
 Testing
is recommended to generate meaningful data
 Impact quality or safety
 Verify appropriate controls or direct corrective action
 Focus
on verification of process control preferred
 Environmental monitoring
 Selected sampling tailored to the line to verify control
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Acknowledgements
ICMSF

Dr. Martin Cole, CSIRO, Australia
(Chair)

Dr. Russ Flowers, Silliker Group, United
States

Dr. Fumiko Kasuga, National Institute of
Health, Japan (Secretary)

Dr. Bernadette Franco, Universidade de
São Paulo, Brazil

Dr. Jeff Farber, Health Canada
(Treasurer)

Dr. Leon Gorris, Unilever, China

Dr. Anna Lammerding, Public Health
Agency, Canada

Dr. Xiumei Liu, CDC China
Dr. Lucia Anelich, Consumer Goods
Council, South Africa

Dr. Tom Ross, University of Tasmania,,
Australia
Dr. Robert Buchanan, University of
Maryland, United States

Dr. Katie Swanson, Ecolab,
United States
Dr. Jean-Louis Cordier, Nestle,
Switzerland

Dr. Marta Taniwaki, Instituto de
Tecnologia de Alimentos, Brazil
Dr. Ratih Dewanti, Bangalore Agricultural
University, Indonesia

Dr. Marcel Zwietering Wageningen
University, The Netherland





Dr. Wayne Anderson, Ireland Food
Safety Authority
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Reference
www.slideshare.com