Process Validation Updates…
and a reminder about Food
Defense
Steve Ingham
Food Safety Extension Specialist
UW-Madison
Areas of Validation Emphasis

Beef carcass dry-aging interventions


Slow-cooking of whole-muscle beef roasts


Kim Wiegand
Ground & formed beef jerky process lethality


Ryan Algino
Alena Borowski
Shelf-stability of RTE products

Darand Borneman
Validating Beef Carcass Dry-Aging – the
Microbial Performance Standard

E. coli O157:H7 must be undetectable



If slaughter process is hygienic or animal is not a
carrier, standard could be met without an
intervention
The intervention adds assurance or overcomes
slaughter hygiene lapses
There is no specified “log reduction”
Validating Beef Carcass Dry-Aging – the
Microbial Performance Standard


A practical approach to meeting this
standard: use an intervention that would
cause a statistically significant decrease in
the number of E. coli O157:H7 cells
Our goal: help you validate your intervention
process

Show that your intervention would cause a
significant decrease in the number of E. coli
O157:H7 cells
Validating Beef Carcass Dry-Aging Challenges


Inoculation studies using pathogens aren’t
possible in plants
Dry-aging conditions vary





Weather
Size and number of carcasses in cooler
Air movement
% Relative Humidity
Length of dry-aging period
Validating Beef Carcass Interventions – a
new approach

Inoculate beef carcass with harmless bacteria
that survive the same (or better) compared to
E. coli O157:H7



Take a “before” sample
Take an “after” sample


Lactic acid bacteria starter culture = “LAB”
How much did levels of LAB decrease?
If LAB decrease enough, E. coli O157:H7
would have decreased, too
How much do the LAB levels have to
drop?


The Least Significant Difference (LSD) for E.
coli O157:H7 in simulated dry-aging studies
is 0.3 logs (50% decrease)
This LSD corresponds to an LAB decrease of
at least 0.25 logs
Accuracy of LAB performance standard
in predicting adequate reduction of
E. coli O157:H7 during dry-aging
Part
Accurate
Fail-safe
Fail-dangerous
Brisket - fat
15/15
0
0
Brisket – lean
12/15
3/15
0
Heart
12/15
3/15
0
Liver
15/15
0
0
Tongue
13/15
2/15
0
Kit for Evaluating Beef Carcass
Intervention Treatments
LAB culture and Diluent
Add diluent to LAB
Mix
Add LAB solution to sponge
Squeeze sponge 10 X
Get ready to inoculate brisket
Inoculate both halves of the carcass


One is sampled “before”
The other is sampled “after”
Inoculate brisket
Score sample with sterilized scalpel
Peel sample away with sterilized
scalpel and forceps
“Before” sample is ready to ship
Ship sample to lab (same way as you
ship generic E. coli samples)
The “after” sample



Use dead locks to pin the large template to
the second carcass half
Take sample when dry-aging is complete
Ship to the lab
Next step:

Determine E. coli O157:H7 LSD and LAB
reductions needed to validate acid-spray
interventions



Acetic acid
Lactic acid
Fresh Bloom
Predicting the Probability of
Achieving a 7-Log Reduction of
Escherichia coli O157:H7 During Roast
Beef Slow-cooking Processes
Beyond THERM…

Slow cooked beef roasts have unique food
safety concerns





Temperature abuse  growth before cooking?
Heat shocked pathogens  tougher to kill?
Slow come-up times  growth before cooking?
Salt and spices  tougher pathogens?
Need predictive tools to evaluate heat
lethality associated with meat processing
Slow-cooking of beef: microbial
performance standards




6.5 log reduction in Salmonella
USDA recommends no more than 6 h
between 50 and 130°F
Besides killing Salmonella, we must also
provide adequate lethality against E. coli
O157:H7
We’ve chosen a 7-log lethality target

Allows for a small amount of growth before
cooking (0.5 log)
Evaluating slow cook processes: our
model system

Unseasoned
ground beef
4 simulated
commercial
slow-cook
schedules
Simulated Cook Schedules
140
130
120
Set Temperature (deg F)

110
Commercial Process
100
90
Slow come-up time
80
Fail to reach 130F
70
Potential heat shock
60
0
60
120
180
200
240
270
Time (min.)
300
330
360
390
405
Evaluating slow-cook processes

Inoculation studies of 4
cook schedules

each 6 h 45 min.

25 g ground beef
9 sampling times each
schedule.

Evaluating slow cook processes



Overlaid plates with
MEMB – recover
injured cells
Determined cumulative
F-value based on time
and temperature history
Used E. coli O157:H7
CFU/g plate counts to
create model
Cumulative Process Lethality




D-value: number of minutes at constant temperature needed to
destroy 90% of organisms
Z-value: change in temperature (°F) needed to change the D-value
by 10-fold
Lethal Rate: shown below, equivalent heating rate per minute;
expressed for reference temperature.
Cumulative process lethality (F-value): cumulative lethal rate
over a given cooking/heating process.
F  10
( T Tr ) / Z
• T = internal temperature
• Tr = Reference temperature
• Z = reference z value
Logistic Regression Analysis




Z = 10.4°F and Tr = 130°F
F-value determined at each sampling point
If process was successful, the sample
achieved an E. coli O157:H7 reduction of 7logs.
Logistic regression used to determine
probability of achieving 7-log reduction for
any given F-value
Logistic Regression Curve for Predicting 7-log Kill
1.2
1
Pr(7 log red)
0.8
0.6
0.4
0.2
0
100
150
200
250
Lethality
300
350
400
1.2
1
Pr(7 log red)
0.8
95% probability of
achieving a 7-log
reduction of E.
coli O157:H7
0.6
0.4
Heat equivalent to
308 min. at 130oF
0.2
0
100
150
200
250
Lethality
300
350
400
Tool development
Representative samples
E. coli
O157:H7 kill
< 7.0 log
E. coli
O157:H7 kill
≥ 7.0 log
Lethality <308
Lethality ≥308
113/124
0/20
11/124
20/20
A sneak peek at the
finished product…
Core temperature
160
140
Temperature (F)
120
100
80
60
• Easy-to-use Excel worksheet
calculations produce two graphs
40
20
0
0
100
200
300
400
Time (min)
• Lethality outlines the cumulative
lethal rate
Lethality
450
400
• Interpretation for processor:
probability that process would
attain the 7-log kill
350
F-value (min)
• Core temperature shows the total
cooking process
300
250
200
150
100
50
0
0
100
200
Time (min)
300
400
•Above an established F-value
(based on temperature and time
combination)  process has high
probability of 7-log kill
Comparison of adequate and inadequate cooking
processes
Cooking process not brought
up to temperature (e.g.
undercooked at 130oF)
Cooking process brought
up to 135oF (e.g. rare roast
beef)
Lethality
Lethality
450
450
400
350
350
300
300
F-value (min)
F-value (min)
400
250
200
150
250
200
150
100
100
50
50
0
0
0
100
200
Time (min)
300
400
0
100
200
300
Time (min)
Process lethality calculations greatly highlight
inadequate cooking processes
400
Next Steps


Seasoned ground beef model system
Model validation with actual roasts


Without seasoning
With seasoning
Validating Lethality of
Processes for Making Ground
& Formed Jerky
Jerky Process Lethality Issues



Evaporative cooling
Adaptation of pathogens if drying is before
high temperature
Seemingly infinite number of processes being
used by processors
Microbial Performance Standards for
Jerky-Making


5-log reduction of Salmonella
5-log reduction of E. coli O157:H7 (beef)
Validating Ground & Formed Jerky
Process Lethality – a new approach

Inoculate jerky mix with harmless bacteria
that survive the same (or better) compared to
E. coli O157:H7 and Salmonella



Take a “before process” sample
Take an “after process” sample


Lactic acid bacteria starter culture = “LAB”
How much did levels of LAB decrease?
If LAB decreases enough, pathogens would
have decreased, too
Process 1 (Cabela Dehydrator), Hot
10
9
8
log CFU
7
Salmonella
6
E. coli
5
Saga 200
4
Biosource
3
2
1
0
0
210
Time (min)
420
Process 1 (Cabela Dehydrator), Cold
10
9
8
log CFU
7
Salmonella
6
E. coli
5
Saga 200
4
Biosource
3
2
1
0
0
210
Time (min)
420
Process 2- no smoke
(Alkar smokehouse)
10
9
8
log CFU
7
Salmonella
6
E. coli
5
Saga 200
4
Biosource
3
2
1
0
0
30
90
150
Time (min)
180
210
240
Process 2- with smoke (Alkar smokehouse)
9
8
7
log CFU
6
Salmonella
5
E. coli
4
Saga 200
Biosource
3
2
1
0
0
30
150
Time (min)
240
Process 3- no smoke (Alkar)
10
9
8
log CFU
7
Salmonella
6
E. coli
5
Saga 200
4
Biosource
3
2
1
0
0
30
45
75
Time (min)
105
135
175
Process 3- with smoke (Alkar)
9
8
7
log CFU
6
Salmonella
5
E. coli
4
Saga 200
Biosource
3
2
1
0
0
30
Time (min)
45
175
Process 4- no smoke (Alkar)
10
9
8
log CFU
7
Salmonella
6
E. coli
5
Saga 200
4
Biosource
3
2
1
0
0
45
90
Time (min)
150
270
Process 4- with smoke (Alkar)
9
8
7
log CFU
6
E. coli
5
Salmonella
4
Biosource
Saga 200
3
2
1
0
0
30
90
Time (min)
180
270
Process 5- no smoke (Alkar)
10
9
8
log CFU
7
Salmonella
6
E. coli
5
Saga 200
4
Biosource
3
2
1
0
0
90
150
210
Time (min)
270
330
Process 6- no smoke (Alkar)
10
9
8
log CFU
7
Salmonella
6
E. coli
5
Saga 200
4
Biosource
3
2
1
0
0
75
105
Time (min)
180
210
How does LAB kill relate to pathogen
kill?
Pediococcus spp. Death (logs)
E. coli Death (logs)
<4
>4
<5
84
0
>5
37
51
How does LAB kill relate to pathogen
kill?
Pediococcus spp. Death (logs)
Salmonella Death
(logs)
<4
>4
<5
98
1
>5
23
50
How does LAB kill relate to pathogen
kill?
P. acidilactici Death (logs)
E. coli Death (logs)
<4
>4
<5
83
3
>5
32
54
How does LAB kill relate to pathogen
kill?
P. acidilactici Death (logs)
Salmonella Death
(logs)
<4
>4
<5
95
5
>5
20
52
Shelf-stability of RTE meat products

Issue is whether Staphylococcus aureus will
grow

Pathogen that best tolerates reduced water
activity
Shelf-stability of RTE meat products






Gathered wide range of commercial products
Made several “substandard” versions of
summer sausage, jerky
Inoculated all products
Vacuum-packaged
Stored at room temperature
Monitored S. aureus levels
Where we’re going with this topic



Determine algorithm for calculating a shelf-stability score
 pH
 Water activity
 MPR
 % Water-Phase Salt
Determine minimum shelf-stability score needed for no
S. aureus growth
Develop computer worksheet for processors to enter
their product characteristics
Some thoughts on Food Defense




Prevention of tampering, terrorism via
commercially processed foods
No regulations…yet
Do an evaluation and take some basic steps
to prevent problems
Info will be on our website:
www.meathaccp.wisc.edu
Need more information or help?




Phone me: 608-265-4801
E-mail me: scingham@wisc.edu
Check our website:
www.meathaccp.wisc.edu
THANK YOU!