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Freezing as a Post Harvest
Process (PHP) for Oysters
July 16, 2015
2001 ISSC Vv Risk
Management Plan
• Illness reduction goal based on
reported illnesses in California,
Florida, Louisiana, and Texas of 40%
for years 2005-2006 (average) and
60% for years 2007-2008 (average)
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April 15, 2003
• California Cracks Down on Hazardous
Gulf Coast Oysters
• California public health officials today
banned the sale of raw oysters harvested
in warm months from the Gulf of Mexico
because of concerns about bacterial
contamination.
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ISSC Approach
• Education to at risk populations and
expanded efforts for PHP
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Consequences for Failure
• Raw half shell oysters subjected to an approved PHP to
reduce Vv to 30 MPN/g or less during certain months
of the year when water temperatures are high
• Label “For shucking by a certified dealer” during
certain months of the year when water temperatures
are high
• Close growing water areas for oysters intended for the
raw half shell market during certain months of the year
when water temperatures are high
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Freezing as a Post Harvest
Process (PHP) for Oysters
• The FDA and ISSC have established a
formal validation procedure for PHP for
oysters
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PHP Requirements
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Process Validation
Equipment Validation
Verification
Revalidation when process fails
Processor Requirements
• The HACCP plan shall contain process controls to ensure
that end point criteria are met for every lot.
• Sampling program to periodically verify that the end point
criteria are met.
• Packing and labeling all shellfish in accordance with all
requirements.
• Record Keeping
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Labeling
• “Processed for added safety” if all pathogens are reduced to safe
levels for the at risk population;
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•
“Processed to reduce (name of target pathogen) to non-detectable
levels" if one but not all pathogens are reduced to safe levels for
the at risk population and the level is non-detectable;
•
“Processed to reduce (name of target pathogen) to non-detectable
levels for added safety” ”if one but not all pathogens are reduced
to safe levels for the at risk population and the level is nondetectable;
•
A term such as IQF, Pasteurized, Pressure Treated may be
substituted for the word “processed.”
Validation Protocol
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For Validation Testing:
Data on ten processed
samples from each of three
processing days (total of 30
samples) are required
All oysters on the processing
day must come from the
same lot
Oysters must contain Vv
numbers with an adjusted
geometric mean (AGM) MPN
of 100,000 per gram as an
initial load (now 10,000/g)
A sample will consist of 10-12
oysters
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IQF Oysters
12
Half Shell Oysters Being
Glazed
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Oyster C02 Freezer Profile Dwell
Time = 9 minutes 08/07/2002
Temperature in Degrees F
80
60
40
20
0
0.0
1.8
3.5
5.3
7.0
8.8
10.5
12.3
14.0
15.8
-20
-40
-60
-80
Elapsed time in minutes
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17.5
Meat 4
Meat 5
Env 6
Env 7
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Summary of Results
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Date Frozen
AGM
Weeks of
Storage at
-18°C
Vv Levels
7/7/03
1.5x105
8 wks
12 wks
<30/g
<3/g
7/21/03
1.5x105
12 wks
16 wks
<30/g
<3/g
8/11/03
2.1x106
16 wks
16 wks
<30/g
<3/g
Summary of Results
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Date
Frozen
AGM
Weeks of
Storage at
-18°C
Vv Levels
9/9/03
2.1x105
>20 wks
<30/g
>20 wks
<3/g
Summary of Results
Date
Frozen
AGM
Weeks of
Storage
at -18°C
Vv Levels
7/19/04
2.6x106
12 wks
<30/g
>12 wks
<3/g
>12 wks
>12 wks
<30/g
<3/g
7/27/04
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6.5x106
Summary of Results
Date
Frozen
AGM
Weeks of Vv Levels
Storage
at -18°C
8/1/05
5.2x104
12 wks
<30/g
19 wks
<3/g
>15 wks
(25wks)
<30/g
<3/g
8/22/05
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2.1x105
API and PCR Comparisons
• Good correlations of MPN numbers for Vv by API and PCR
• Vv by API-Total Negative 174 out of 352 samples
• Vv by PCR-Total Negative 161 out of 351 samples
• (17 positive by PCR, but not by API). Three samples were
also negative by PCR, but positive by API.
• Total Vp was still present in oysters by PCR when Vv was
reduced <30MPN/g as determined by API and PCR
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Conclusions
• Need to refine time/temperature abuse conditions needed
to achieve required Vv levels in the test oysters
• Protocols should include requirements to continue to
analyze oysters at least one additional time for Vv after
previous analysis indicated 0, 1 or 2 positive tubes
• Initial IQF freezing temperatures and the months when the
validation study is conducted may affect the time required
in frozen storage needed to reduce Vv numbers to nondetectable levels
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Acknowledgement
• This study was funded by the
Virginia Fishery Resource Grants
Program (VFRGP) and by the
Commercial Fish and Shellfish
Technologies Program (CFAST)
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