Harris,L.J.UCDavis04/19/2016
Harris,LindaJ.,UCDavis 1
Linda J. Harris, Ph.D., CFSDepartment of Food Science and Technology
UC DavisApril 19, 2016
FDA tree nut risk assessment
FDA to Assess Risk of Salmonellosis Associated with Eating Tree Nutsp July 17, 2013
n The risk assessment will inform FDA policy and may be useful for owners and operators of tree nut processing plants and other postharvest facilities, among other stakeholders.
http://www.fda.gov/Food/NewsEvents/ConstituentUpdates/ucm361206.htm
FDA Tree Nut Risk Assessment
p The purpose of the risk assessment will be to quantify the public health risk associated with the consumption of potentially Salmonella contaminated tree nuts and to evaluate the impact of risk-based preventive controls on the risk of human salmonellosis arising from consumption of tree nuts.
http://www.fda.gov/Food/NewsEvents/ConstituentUpdates/ucm361206.htm
Rationale: Salmonella contaminated tree nuts are a concern
1. Outbreaks of salmonellosis have occurred, e.g.:- Raw almonds (2000/2001 & 2003/2004)- Pine nuts (2011)- Desiccated coconut (1999)
2. Product has been recalled due to Salmonella contamination, e.g.:- Pistachios (2009/2010) - Pine nuts (2011)- Walnuts (2010) - Macadamia nuts (2013)- Hazelnuts (2009, 2013)
3. Salmonella has been isolated from product during surveys, e.g.:- Almonds - Macadamia nuts- Cashew nuts - Walnuts- Brazil nuts - Pistachio nuts
4
For references: please see Federal Register Notice or contact the presenters
http://www.fda.gov /d ownl oa ds/ Fo od /Foo dScie nc eRe se arc h/Ris kSaf etyA sse ssm en t/UC M 36 229 7. ppt x
Risk assessment: The risk Assessment Framework
Conduct & Manage Process
Step 1: Commission
Step 2: Data collection & evaluation
Step 3: Develop model/reportStep 4: Review & clearance
Step 5: Issue
5http://www.fda.gov /d ownl oa ds/ Fo od /Foo dScie nc eRe se arc h/Ris kSaf etyA sse ssm en t/UC M 36 229 7. ppt x
Risk assessment: Choosing a quantitative approach• We anticipate the following model outputs:
- Expected number of cases / serving or cases / year- Quantified impact of interventions through
“what-if scenarios”
• Model likely based on peer-reviewed risk assessment models: – e.g. Lambertini et al., 2012 (developed for U.S. almonds)– Plan to evaluate product pathway: harvest to consumption
• Expected extensions beyond currently published models:– Adaptation to consider other tree nuts in addition to almonds– Quantification of uncertainty – Sensitivity analysis
6http://www.fda.gov /d ownl oa ds/ Fo od /Foo dScie nc eRe se arc h/Ris kSaf etyA sse ssm en t/UC M 36 229 7. ppt x
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Risk assessment: Proposed model outline
7
Salmonella prevalence at harvest Salmonella concentration at harvest
Pre-process storage
Post-harvest treatment
Post-process storage
Retail storage
Consumer home storage
Risk of illness per annum & r isk per billion servings
Dose-Response model Serving size
Number of servings
http://www.fda.gov /d ownl oa ds/ Fo od /Foo dScie nc eRe se arc h/Ris kSaf etyA sse ssm en t/UC M 36 229 7. ppt x
Risk assessment: Data needs for modeling
1. Salmonella prevalence & concentration on tree nuts
2. Salmonella survival & inactivation on tree nuts during storage
3. Salmonella inactivation through post-harvest treatments
4. Salmonella dose-response relationships (we currently plan to use published Salmonella dose-response models)
5. Tree nut consumption in the U.S.
8http://www.fda.gov /d ownl oa ds/ Fo od /Foo dScie nc eRe se arc h/Ris kSaf etyA sse ssm en t/UC M 36 229 7. ppt x
Data Request: Salmonellaprevalence and concentration
Example: Prevalence of Salmonella in 100-g Raw Almond Kernels With 95% Confidence Intervals (Wilson Score)
0
0.5
1
1.5
2
2.5
Prevalence(PercentPositive)
Total 14,949 samples
~1% positive
Danyluk et al., 2007; Bansal et al., 2010; Lambertini et al., 2012, unpublished
0123456789
10
2002 2003 2004 2005 2006 2013
MPN
/100
g
Year
Example: Levels of Salmonella in almonds per 100 g
Average level of Salmonella in 109 positive samples -----13 ± 14 MPN/1000 g
Danyluk et al., 2007; Bansal et al., 2010; Lambertini et al., 2012, unpublished
Receiving
PostharvestHandlingofPistachios
Pre-cleaner
Huller(peeler)
FloatTank
Dryer
Sinkers85%
Silo
Dryer
Floaters15% Silo
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90.0%
10.0%
2.6%
15.0%
5.0%
25.0%
2.4%
50.0%
0.0% 20.0% 40.0% 60.0% 80.0% 100.0%
Sinkers
Floaters
Inshell (Edible) Ediblekernel Shell InedibleKernel
Harris calculations
p Average prevalencen Almonds (kernel):
p 0.98% (100 g; 95% CI, 0.83 to 1.2%; 137 of 13,972) n Almonds (inshell):
p 1.3% (100 g; 95% CI, 0.61 to 2.8%; 6 of 455) n Pecans (inshell):
p 0.95% (100 g; 95% CI, 0.70 to 1.3%; 44 of 4,641)n Walnuts (inshell):
p 0.14% (375 g; 95% CI, 0.054 to 0.35%; 4 of 2,903) n Pistachio (inshell)
p Sinker: 0.37% (100 g; 95% CI 0.21 to 0.67; 11 of 2,934)p Floater: 2.0% (100 g; 95% CI 1.3 to 3.0; 21 of 1,032)
Danyluk et al., 2007; Bansal et al., 2010; Lambertini et al., 2012; Davidson et al., 2015; Brar et al., 2016; Harris et al., in press; unpublished
Prevalence equivalent? Data Request: Salmonella survival, growth or inactivation
p Impacts of nut composition, water activity, storage temperature
p Different stages on farm-to-fork continuum n Impact of relative humidity during storage,
geographic region or seasonp In different foods made with tree nuts as
ingredients
SurvivalofSalmonelladuringstorageat23°C,4°C,and-20°Conalmondsandpistachios.
Kimber et al.,submitted to Journal of Food Protection
Allenrichmentswerepositive
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0 50 100 150 200 250 300 350
Population(logCFU/g)
StorageTime(days)
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6
0 50 100 150 200 250 300 350
Population(logCFU/g)
StorageTime(days)
SurvivalofSalmonelladuringstorageat23°C,4°C,and-20°Conalmondsandpistachios.
Kimber et al.,submitted to Journal of Food Protection
Allenrichmentswerepositive
0
1
2
3
4
5
6
0 50 100 150 200 250 300 350
Population(logCFU/g)
StorageTime(days)
0
1
2
3
4
5
6
0 50 100 150 200 250 300 350
Population(logCFU/g)
StorageTime(days)
Slopeofline=-0.15logCFU/monthSlopeofline=-0.24logCFU/month
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Salmonella declineinpistachiosandalmonds(Harrislaboratory,varioussources)
Data set (23ºC) Reduction Rate (log CFU/day)
Reduction Rate (log per 30 days)
P-value
AlmondsS. enteritidis PT30:
171 days 0.0105 0.32 <2·10-16
365 days 0.0069 0.21 <2·10-16
560 days 0.0079 0.24 <2·10-16
Log 9 180 days 0.0055 0.16 2.5·10-07
Log 7 180 days 0.0071 0.21 4.6·10-09
Log 5 180 days 0.0083 0.25 3.8·10-09
Log 3 180 days 0.0068 0.20 5.7·10-08
Salmonella cocktail, 201 days 0.00929 0.28 <2·10-16
PistachioSalmonella cocktail 0.00513 0.15 1.4 ·10-7
Reduction ratesbased on the linear fit: log (CFU)= log (CFU)– rate* time
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1
2
3
4
5
6
0 100 200 300 400 500 600
Popu
lation
(lo
g CF
U/g)
Time (days)
75°F (24°C)
Survival of Salmonella on stored almonds
Kimber et al., 2012, Journal of Food Protection 75:1394–1403
FDA analysis of storage data
Santillana Farakos, S. M., R. Pouillot, N. Anderson, R. Johnson, I. Son, and J. Van Doren. 2016. Modeling the survival kinetics of Salmonella in tree nuts for use in risk assessment. Int. J. Food Microbiol. 227:41–50.
Santillana Farakos et al., 2016. Int. J. Food Microbiol. 227:41
Santillana Farakos et al., 2016. Int. J. Food Microbiol. 227:41 Santillana Farakos et al., 2016. Int. J. Food Microbiol. 227:41
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Survival of Salmonella in tree nuts
Santillana Farakos et al., 2016. Int. J. Food Microbiol. 227:41
CalculatedReductionsofSalmonellaDuringStorage
Nuttype MethodWeeks(LogCFU Reduction)
1 4 12 52Almonds FDA 0.40 0.84 1.50 3.27
Harris 0.055 0.22 0.66 2.85Pistachios FDA 0.14 0.35 0.73 1.99
Harris 0.035 0.14 0.41 1.79Walnuts FDA 0.66 1.20 1.93 3.62
Santillana Farakosetal. ,2016.Int. J. FoodMicrobiol. 227:41-50.Kimberetal. ,2012, JournalofFoodProtection75:1394–1403.Lambertinietal. ,2012.FoodResearchInternational45:1166–1174.
FDAcalculations
• Uncertainty dimension– Median,mean,2.5%,97.5%
• Variability dimension– Includestandarddeviation
CalculatedReductionsofSalmonellaDuringStorageofAlmonds
Method UncertaintyWeeks(LogCFU Reduction)
1 4 12 52FDA 97.5% 0.33 0.72 1.31 2.88
Median 0.40 0.83 1.48 3.23Mean 0.40 0.84 1.50 3.272.5% 0.49 1.00 1.78 3.85
Harris 0.055 0.22 0.66 2.85
Santillana Farakosetal. ,2016.Int. J. FoodMicrobiol. 227:41-50.Kimberetal. ,2012, JournalofFoodProtection75:1394–1403.Lambertinietal. ,2012.FoodResearchInternational45:1166–1174.
Santillana
Farakosetal.,2016.Int.J.FoodMicrobiol.227:41-50.
Week1 Week52
FDA uncertainty analysis
p Prevalencep Survivalp Concentrationp Consumption amountp Treatmentp Treatment variability
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Data request:Storage, handling and processingp Typical storage conditions
n Time, temperature, relative humidityn From harvest to processing
p Types of treatments used to reduce bacterian Frequency appliedn Process conditionsn Efficacy of treatments
p Storage conditions post treatmentp Handling practices that are typically
applied by the consumer
Process Validation
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6
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10
0 5 10 15
log
CFU/
g
Treatment time (min)
TSA 6 0 ºCTSA 7 0 ºCTSA 8 0 ºC
05
101520253035
5.0-5.45.5-5.96.0-6.46.5-6.97.0-7.4
Freq
uenc
y (%
)
Log CFU/almond reduction
SE PT30 reduction on almonds treated with PPO
PPO September 2004 Blanching June 2005Oil Roasting June 2005
0.0
2.0
4.0
6.0
8.0
0.0 1.0 2.0 3.0 4.0 5.0
Log
CFU/
g
Treatment time (min)
240°F 250°F 260°F
Du, et al., 2010, J . Food Prot. Danyluk et al., 2005, J . Food Prot. Harris , et al., 2011, Food Res . Int.
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1 0
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5 0
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5 0
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1 0
2 0
3 0
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5 0
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1 0
2 0
3 0
4 0
5 0
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1 0
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4 0
5 0
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1 0
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5 0
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1 0
2 0
3 0
4 0
5 0
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1 0
2 0
3 0
4 0
5 0
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1 0
2 0
3 0
4 0
5 0
Consumer StorageofTree Nuts(Leeetal.,2010)
Storagetime(weeks)
60.2% 36.9% 55.2%
RoomTemperature:23ºC Refrigerator:4ºC Freezer:-20ºC
Storagetime(weeks)Storagetime(weeks)
62.1% 46.1%34.2%
46.8% 10.5% 11.6%
% C
onsu
mer
s st
orin
g fo
r th
e sp
ecifi
ed
dura
tion,
am
ong
cons
umer
s st
orin
g at
the
spec
ified
te
mpe
ratu
re
Data request:Food consumption practicesp Frequency consumed by population
subgroupsp Frequency consumed raw by different
population subgroupsp Frequency with which tree nuts that have
undergone treatments are consumed by different population subgroups
p Serving sizes
Almond Risk Assessment
Lambertini, E., M. D. Danyluk, D. W. Schaffner, C. K. Winter, and L. J. Harris. 2012. Risk of salmonellosis from consumption of almonds in the North American market. Food Res. Int. 45:1166–1174.
AlmondRiskAssessment• InitialRiskAssessmentin2006helpedestablishtarget4-log
reductionforregulation
• Version2:FoodResearchInternational,2012
• ElisabettaLambertini(PostDoc),DonSchaffner(Rutgers),MichelleDanyluk(UFL),CarlWinter(UCD),LindaHarris(UCD)
• Significantmodificationof2006riskassessment:– added new prevalence data, recalculation of levels, assumes
mandatory treatment (with portions andvalidation dataused inmodel), new information onconsumer handling, updatedconsumption, reassessment of2001outbreak
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Modelformat–@Risksoftware
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0 2 0 0 4 0 0
Population
logCFU/g
Sto rage Time (d ays)
0 .0
0 .5
1 .0
1 .5
2 .0
Perc
ent p
ositi
ve 1
00 g
sa
mple
s
Harv es t y earHistogram of conc
Salmonella Concentration on almonds (MPN/100 g)
Rel
ativ
e fre
quen
cy
0 5 10 15 20
0.0
0.5
1.0
1.5
2.0
Selectpositiveornegativesampleandlevelbasedon8-yearsurvey.
Selectpre-processingstoragetime/tempbasedonindustrydata.Calculatedecline.
Selectprocessbasedonindustrydata.Determinereductionachievedinthatprocessbasedonvalidationdata.
Selectpost-processstoragetime/tempbasedonindustryandconsumerdata.Calculatedecline.
Selectamountconsumed(average31.5g(1gto100g)
DetermineillnessbasedonFAO/WHOdose-responsecurveforSalmonella.
Lambertinietal. ,2012
Salmonelladose-response model (WHO/FAO 2002)
Dose response
p There is no such concept as the “infectious dose”
p One cell can make you sick
p 1 cell = 0.02% prob of illness, 1/392 people
p DR modeln FAO/WHO 2002. Risk
assessments of Salmonellain eggs and broiler chickens.
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0.4
0.6
0.8
1
0 2 4 6 8 10
Pro
babi
lity
of
Ill
nes
s
Log CFU/serving
RiskAssessmentModelOutput– SingleRun100,000IterationsBaselineAssumptions
Lambertinietal. ,2012
D. Percent untreated: 10%0.250.200.150.100.05
0-10 -8 -6 -4 -2 0 2 4 6
Log (cases/year)
Freq
uenc
y
B. Prevalence: 65%
0.250.200.150.100.05
0-10 -8 -6 -4 -2 0 2 4 6
Freq
uenc
y
Log (cases/year)
C. Concentration: 100 MPN/100g0.250.200.150.100.05
0-10 -8 -6 -4 -2 0 2 4 6
Freq
uenc
y
Log (cases/year)
A. Baseline
0.250.200.150.100.05
0-10 -8 -6 -4 -2 0 2 4 6
Freq
uenc
y
Log (cases/year)
RiskAssessmentModelOutput– SingleRun100,000Iterations
Lambertinietal. ,2012
Summary
• FDAtreenut riskassessmentforalmonds isunder review– Unknownpublicationdate
• Riskassessmentscanbeusedtoinformriskmanagementdecisions– Exampleofmanagementdecisions
• Appropriatelevelofpathogenreduction• Criterionfor“pasteurized”label.
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Questions?