pathogen transfer in fresh cut operations
TRANSCRIPT
9/22/2015
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Pathogen Transfer in Fresh‐Cut Operations
Dr. Elliot RyserDept. of Food Science and Human Nutrition
Michigan State UniversityEast Lansing, MI
USDA‐NIFA‐NIFSI‐2011‐SPECIAL EMPHASIS GRANT
AN INTEGRATED APPROACH TO ENHANCE THE MICROBIAL SAFETY OF FRESH‐CUT FRUIT AND VEGETABLE PRODUCTS DURING PROCESSING,
PACKAGING, AND RETAIL DISTRIBUTION
PROJECT GOAL
• To enhance the microbial safety and quality of ready‐to‐eat, fresh‐cut fruit and vegetable products via integrated research and outreach/training targeted at the processing, packaging, and distribution phases of the produce chain.
5 PROJECT MODULES
• PROCESSING– Quantify pathogen transfer and cross‐contamination
• PACKAGING– Develop optimal packaging systems to enhance microbial safety and
quality
• DISTRIBUTION– Evaluate and model potential for pathogen survival/growth during
distribution
• RISK MODELING/ECONOMICS– Quantify risk of pathogen survival, and appropriate intervention
strategies
• EDUCATION/TRAINING– Reduce risk of foodborne illness via high quality training programs
How Safe is Our Produce? The Good Old Days
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Welcome to the 21st Century Pre‐Harvest Contamination
Cattle Feedlots
Wild Animals
Irrigation Water
Composting Practices
Harvesting is Highly Variable Processing is Also Highly Variable
• Commercial Processors
– Mechanical
– Semi‐mechanical
– Manual
• Foodservice/Supermarkets
– Semi‐mechanical
– Manual
Contamination During Processing
• Crates, bins, tarps
• Food contact surfaces during processing– Equipment, knives, conveyors, brushes, flume tanks, shredders, shakers, dryers
• Non‐food contact surfaces– Floors, drains
• Coolers, storage areas
• Personnel– Gloves, hygienic practices
Leafy Green Processing
Shredder
Conveyor
Flume tank
Shaker tableCentrifugal drier
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50 lb of E. coli O157:H7‐inoculated lettuce or spinach
Buchholz et al. 2012. J. Food Prot. 75:1184‐1197
Sample equipment and water
Product Equipment and WaterDistribution of E. coli O157:H7 after
Centrifugal Drying of Lettuce
22.5 kg (50 lbs) uninoculated
+ 22.5 kg (50 lbs) inoculated
90 kg (200 lbs) uninoculated
STOP
Empty and refill water recirculation tank
EQUIPMENTand WATER
Equipment (and Water) Product
Buchholz et al. 2012. J. Food Prot. 75:1920‐1929
‐2
‐1
0
1
2
3
4
5
0 20 40 60 80 100 120 140
E. coli O157:H7 (log CFU
/g)
Cumulative Mass (kg)
Iceberg
Romaine
Spread of E. coli O157:H7 to Product during Processing of Leafy Greens Containing ~4 log CFU/g
Uninoculated Inoculated Uninoculated
Empty and refill water
recirculation tank
Spread of Contaminated Radicchio
STOP
9 kg (20 lbs)inoculated Radicchio
900 kg (2,000 lbs) uninoculated Iceberg
45 kg (100 lbs) uninoculated
Iceberg
Buchholz et al. 2014. J. Food Prot. 77:1487‐1494
Radicchio Remaining on Equipment Surfaces after Processing 900 kg of Uninoculated Lettuce
Conveyer Belt and Flume Tank
Blade and Interior Surface of the Lettuce Shredder
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Spread of Contaminated Radicchio to Iceberg Lettuce during Processing
0 500 1000 15000
5
10
15
20
400
600
800
1000Replicate 2
Replicate 3
Replicate 1
Cumulative Mass (kg)
Radicchio (g)
Percentage of Radicchio Recovered from Equipment Surfaces After Processing
AB
A
AB
B0.00
0.50
1.00
1.50
2.00
2.50
3.00
Shredder Conveyer Flume Shaker
% of Rad
icchio
http://www.youtube.com/watch?v=8mSKdjxauTw
How well do sanitizers work?
0
20
40
60
80
100
120
140
160
Whole Apples Sliced Apples Whole Lettuce Shredded Lettuce
Strawberries Cantaloupe
Tim
e (s
ec
on
ds
)
D-values for L. monocytogenes on fresh produce exposed to various sanitizers
Tsunami 80 ppm
Sodium Hypochlorite 100 ppmSodium Hypochlorite 200 ppmChlorine Dioxide 3 ppm
Rodgers et al. 2004. J. Food Prot. 67:766‐771
Not well if the organic load in the water is high?
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Wash Water Preparation
• Organic load (blended iceberg lettuce)
– 0%, 2.5%, 5%, or 10% (w/v)
• 890 L (235 gal) recirculation tank
Davidson et al. 2014. J. Food Prot. 77:1669‐1681
Chlorine‐Based Sanitizer
• XY‐12, at 50 ppm available chlorine
– Unadjusted, pH 8.10
– Adjusted to pH 6.5 with Citric Acid (CA)
– Adjusted to pH 6.5 with SmartWashTM (SW)
• Sanitizer concentration confirmation
– XY‐12: Chlorine Test Kit 321, Ecolab
Processing (5.4 kg Batches)
Uninoculated
(90 s)
Inoculated
(90 s)
Uninoculated
(90 s)
Uninoculated (90 s)
Uninoculated
(90 s)
Activities during 10 min intervals:
•Adjust sanitizer to 50 ppm
•Adjust pH to 6.5
•Collect water samples
10 min
10 min
10 min
10 min
Populations of E. coli O157:H7 in Recirculating Wash Water
B
B
C
C
B
B
C
C
B
C
BB
A
A
B B
A
A
B B
A
B
A
A
A
AAB
AB
A
A
AB
AB
A
A
AA
A
A
AA
A
A
AA
A
A
AA
‐3
‐2
‐1
0
1
2
3
4
5
6
I 1 2 3 I 1 2 3 I 1 2 3
XY‐12 XY‐12 + CA XY‐12 + SW
Log CFU
/ml
Batch
0% 2.5% 5% 10%
Populations of E. coli O157:H7 on Iceberg Lettuce after Centrifugation
A
A
B
B B
A
B
B A
B
A
A
AA
A
A
A
AB
ABB
A
AB
A
B
B
A
A
A
A
A
B
A
AB
AB
AB
A
AB
AB
B A
A
A
A
A
A
AB
A
AA
A
A
A
AB
AB
A
B
A
A
A
A
‐1
0
1
2
3
4
5
6
7
Initial I 1 2 3 Initial I 1 2 3 Initial I 1 2 3
XY‐12 XY‐12 + CA XY‐12 + SW
Log CFU
/g
Batch
0% 2.5% 5% 10%
Populations of E. coli O157:H7 in Centrifugation Water
B B
C C
B
C B
CB C
C
A
A
BB
A
B
A
B
A
B
B
A
A
A
AB
AB
A
A
A
A
A
A
A
A
A
A
A A
A
AB
AA
A
A
AA
‐3
‐2
‐1
0
1
2
3
4
5
6
I 1 2 3 I 1 2 3 I 1 2 3
XY‐12 XY‐12 + CA XY‐12 + SW
Log CFU
/ml
Batch
0% 2.5% 5% 10%
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Salmonella Transfer during Tomato Slicing
Assess the impact of multiple processing variables on Salmonella transfer during slicing of tomatoes.
1 inoculated tomato(~ 5 log CFU/g)
Slicer designTemperature
Time
WetnessThickness
Variety
Slicer
20 uninoculated tomato
Tomato slice samples
Microbial analysis
Wang and Ryser. 2015. Int. J. Food Microbiol. (submitted)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Manual Electric
Impact of Slicer Design onSalmonella Transfer
log
CF
U/t
om
ato
Tomatoes
Result: Objective 2
Salmonella Transfer to Different Parts of a Manual Slicer
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
whole slicer back & bottom plate blade
log
CF
U/t
om
ato
Tomatoes
Result: Objective 2
-0.5
0.5
1.5
2.5
3.5
4.5
5.5
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
whole slicer blade pusher & side
Salmonella Transfer to Different Parts of an Electric Slicer
log
CF
U/t
om
ato
Tomatoes
Result: Objective 2
Variables Transfer rate (%)
Slicer designManual
1.11 ± 0.48 AElectric
0.45 ± 0.28 A
Time0 min
1.11 ± 0.48 A30 min
1.01 ± 0.49 A
WetnessDry
1.11 ± 0.48 BWet
12.21 ± 2.44 A
Temperature23 °C
1.11 ± 0.48 A10 °C
0.1 ± 0.05 A 4 °C
0.63 ± 0.35 A
Slice thickness1/4 “
1.11 ± 0.48 A3/16 “
0.69 ± 0.16 A3/8“
0.18 ± 0.08 A
VarietyTorero
1.11 ± 0.48 ARebelski
0.08 ± 0.03 BBigdena
0.07 ± 0.06 B
Salmonella Transfer Rate to 20 Uninoculated Tomatoes
Result: Objective 2
Salmonella Transfer during Tomato Dicing
2 lb Inoculated tomatoes
(~ 5 log CFU/g)
50 g / sample
Microbial analysis
2 lb UninoculatedRoma tomatoes
10 batches of 2 lb Uninoculated
tomatoes
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Salmonella Populations Transferred to Uninoculated Tomatoes
0 1 2 3 4 5 6 7 8 90
0.5
1
1.5
2
2.5
3
3.5
4
Sal
mo
nel
la t
ran
sfer
red
to
to
mat
oes
(lo
g C
FU
/g)
ypred
yobs
asyCBasyPB
bootCB
bootPB
Uninoculated tomato weight (kg)
Diced Tomato Washing
Salmonella Populations on Diced Tomatoes during 2 min of Washing
A
A
A
B
A
B
A
B
0.00
1.00
2.00
3.00
4.00
5.00
6.00
Dip T20 T40 T60 T80 T100 T120 Tend
Water XY-12 + CA
Tsunami 200 Tsunami 100
Time (sec)
log
CF
U/g
Salmonella Populations in Wash Water during 2 min of Washing lo
g C
FU
/ml
Time (sec)
A
B B B
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
W20 W40 W60 W80 W100 W120 Wend
Water Tsunami 200
XY-12 + CA Tsunami 100
LOD
Salmonella Populations on Equipment Surfaces after 2 min of Washing
log
CF
U/1
00cm
2
Equipment sample locations
A A
A
AB ABB
AB
B
B
B
ABB
-3.50
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
Water tank Dump tank Shaker table
Water XY-12 + CA
Tsunami 100 Tsunami 200
Salmonella Transfer during Conveyingof Diced Tomatoes
inoculation
sampling
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A
A
B B
C
AAB
ABB
C
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
T200 T100 XY-12 EW Water
ThermoDrive InterLocking
Salmonella Reduction after Spray Treatment on Conveyor Belts
Lo
g r
ed
uc
tio
n
Spray treatment
Listeria Transfer during Celery Dicing
Kaminski et al. 2014. J. Food Prot. 77:756‐761
Uninoculated celery (250 g)
Inoculated celery or Swiss chard (250 g)
15 batches uninoculated celery (250 g each)
Experimental Design Percentage of Swiss Chard Transferred
0
10
20
30
40
50
60
Sw
iss
char
d t
ran
sfer
red
(%
)
Batch
AC
AB A
A A A
AA
A AA
AB
A
AB
A
AB AA
A
A
AA
A A
A
AA
A
AA
A
A AA
A A AA A
AA
A
AA
0
1
2
3
4
5
6
7
8
9
I 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Lo
g C
FU
/g
Batch
Day 0 Day 3 Day 7
Generation time = 3.54 d
Growth of L. monocytogenes in Diced Celery at 4°C
Growth of L. monocytogenes in Diced Celery at 7°C
BC
AB B
A B B
B B B BB
AB
A
A B
A
AB ABA
AB AB A
AB AB AB
AB
AAB
A
A AA A A
A
A
A
AA
AA
A
AA
A
0
1
2
3
4
5
6
7
8
9
I 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Lo
g C
FU
/g
Batch
Day 0 Day 3 Day 7
Generation time = 2.35 d
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Growth of L. monocytogenes in Diced Celery at 10°C
BC
CB C
B C C
C CC C
BC
BB
A B
B
A
B
A
B BB B
B B
A
B A
A
A AA
A A AA A
A AA
AA
A AA
0
1
2
3
4
5
6
7
8
9
I 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Lo
g C
FU
/g
Batch
Day 0 Day 3 Day 7
Generation time = 0.87 d
Slice 20 Uninoculated Onions
Spread of Listeria during Slicing of Onions
One onion dip‐inoculated with Listeria at 8.6, 6.4 or 5.5 Log
CFU/onion
Collect top, middle and bottom slice
Dry in fume hood for 90 min
Dilute or filter and plate on MOXIncubate at 37°C for 48 hr
Slice Inoculated Onion
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0 5 10 15 20
L. M
onocytogen
es(Log CFU
/onion)
Uninoculated onion
Listeria transfer from 1 inoculated onion (8.5 Log CFU/onion)
Rep1 Rep2 Rep3
Rep1 Rep2 Rep3
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 5 10 15 20
L. M
onocytogen
es(Log CFU
/onion)
Uninoculated Onion
Listeria transfer from 1 inoculated onion (6.4 Log CFU/onion)
Rep1 Rep2 Rep3
Rep1 Rep2 Rep3
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20L.. M
onocytogen
es(Log CFU
/onion)
Uninoculated Onion
Listeria transfer from 1 inoculated onion (5.5 Log CFU/onion)
Rep1 Rep2 Rep3
Rep1 Rep2 Rep3
Listeria Transfer during Mechanical Dicing of Onions
Dice 10 (2.3 kg) batches of
uninoculated onions
2.3 kg of onions dip‐inoculated with Listeria at 4 or 2 Log
CFU/g
Collect 50 g sample from each batch.
Dry in fume hood for 90 min
Dilute or filter and plate on MOXIncubate at 37°C for 48 hr
Dice 1 (2.3 kg) batch of inoculated
onions
Prime Dicer with 2.3 kg of
uninoculated onions
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 1 2 3 4 5 6 7 8 9 10
L. m
onocytogen
es (Log CFU
/g)
Onion Batch
Listeria Transfer from 1 (2.3 kg) Batch of Inoculated Onions (4.2 Log CFU/g)
Rep 1 Rep 2
Rep 3 Rep 1
Rep 2 Rep 3
Transfer of L. monocytogenes during Coring of Cantaloupe and Honeydew Melon
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L. monocytogenes on the Rind of Cantaloupe and Honeydew Melon
Transfer of L. monocytogenes from the Rind to Cantaloupe Flesh
Transfer of L. monocytogenes from the Rind to Honeydew Melon Flesh Slicing Experiments
• Dip‐inoculated for 10 min in a 3‐strain avirulent cocktail of L. monocytogenes (strains M3, J22F, and J29H) containing 109 CFU/ml, air‐dried for 1 h and then stored at 4oC for 24 h
• Two inoculated melon halves were mechanically sliced using a 0.75 inch manual slicer (Vollrath Redco 401N) followed by eight uninoculated melon halves
• Enumeration of L. mono on modified TSA‐YE and Enrichment with UVM media
Listeria Transfer from Inoculated to Uninoculated Cantaloupe Melon Halves during Mechanical Slicing
‐1
0
1
2
3
0 2 4 6 8 10
log (CFU
/g)
Melon Halves
‐1
0
1
2
3
0 2 4 6 8 10
log (CFU
/g)
Melon Halves
Listeria Transfer from Inoculated to Uninoculated Honeydew Melon Halves during Mechanical Slicing
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Take Home Message
• A small contamination event in the field can lead to the contamination of large quantities of product after processing.
• New microbial intervention strategies are needed to minimize contamination of fresh‐cut produce during washing.
• Changes in processing equipment design can lead to decreased levels of contamination
• The order in which fresh produce is processed may play a role in minimizing contamination
Acknowledgements
• Dr. Annemarie Buchholz
• Dr. Gordon Davidson
• Dr. Harry Wang
• Chelsea Kaminski
• Andrew Scollon
• Rocky Patil– and many undergraduate assistants
• Processing Equipment– Heinzen Manufacturing
– Urschel Laboratories
– Dorner Manufacturing
– Bolthouse Farms
• Financial Support
TEAM MEMBERSElliot T. Ryser
• Professor
• Food Science
Bradley P. Marks
• Professor
• Biosystems Engineering
Eva Almenar
• Assistant Professor
• School of Packaging
Kirk Dolan
• Associate Professor
• Food Science
Randolph M. Beaudry
• Professor
• Department of Horticulture
Janice B. Harte
• Assistant Professor
• Food Science
Maria Rubino
• Associate Professor
• School of Packaging
Sanghyup Jeong
• Visiting Assistant Professor
• Biosystems Engineering
Robert Scharff•Assistant Professor, Economics of Consumer Choice Economics of Health and Safety
•The Ohio State University
Donald W. Schaffner•Extension Specialist in Food Science and Professor
•Rutgers University
Keith Vorst•Assistant Professor
•Industrial Technology
•California Polytechnic State University
Craig Kaml
•Vice President
•International Food Protection Training Institute