Transcript AOAC 2 pathogens

Existing Seafood
Pathogens and
Future Seafood
Safety Concerns
Taran Skjerdal
[email protected]
tlf +4723216268
AOAC meeting: Setting Performance Requirements
for New and Modern Methods Inaugural meeting,
June 25-26 2009, Rockville, USA
Objectives of the talk:
Give an introduction to
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Special concerns with seafood
● Global trade
● Water
Pathogens in seafood from different geographic areas
● Effect of water temperature, farming conditions and
seafood matrix
Effects of processing on food safety and quality
Trends in legislation
● Differentiated limit values at various stages in the farm-tofork chain
● Focus on ready-to-eat products
Seafood is a global trade
Existing and upcoming (expected) production areas,
as it was seen in 2007
0-3 days
+1-2 days
+1-3 days
+1-7..
days
Fish has a short shelf life,
But goes through many
Steps along the farm-to-fork chain
– where microbes can enter and multiply
and even change
Processing to ready-to-eat products, often in
transit countries, is more common than before
Photo: T Skjerdal
Fish products with various risk levels
Raw – lightly preserved – undercooked
and stored – cross contaminated
Traditional analysis method in trade:
Sensory quality (QIM-score)
Sensory quality assessment during storage
Torry scale - QIM (Quality index method)
Ideal conditions
deviations due
to catch
damages etc
Microbial spoilage
Photo: T Skjerdal
Storage on ice (days)
A scoring system for sensory attributes
Linear correlation with storage time
A good and rapid system for quality and freshness assessment
– when the head is on and inspection is possible
Read more on: http://www.qim-eurofish.com/default.asp?ZNT=S0T1O13
In large scale production and distribution…..
Photo: T Skjerdal
…the fish head is not
always on.
…inspection is not always
possible or cost effective.
At the German border: The
procedure for opening a container
takes 8 hours.
Other analysis methods are needed for quality and safety aspects
Analysis needed:
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Assessment and control of food safety of raw materials and
products
Assess legal aspects and trustworthyness in international trade
when
● traceability data are diffuse or missing
● the suppliers are new or not known
● the risk agents may vary
Analysis methods should preferably be
● Possible at the time when decisions have to be taken
● Cost effective
● Possible to combine with predictive models, meaning that
analysis at one step in the farm-to-fork chain should make it
possible to estimate the food safety risk later in the chain.
Consequence: measurement of total viable count may in some
cases give more information than the presence/absence of a
specific pathogen.
● Quantitative-Detection is in many cases not enough – the risk
is often more related to level
Presence of microbes in sea water
depends on for instance water temperature, contamination level, etc
Case: A farming locality is continuously supplied with human
pathogenic bacteria from the fish feed (Salmonella) humans and
mammalian sewage (Listeria, Vibrio, Shigella, viruses).
microbe level in the water
- Which strains will survive in 1) cold water and 2) temperate waters?
Microbes grow
Microbes grow very slowly,
but enough to balance for those who
die off – waters with high content of
organic material but low temperature
Time
Microbes die off – waters with low
temperature and/or low content of
organic material
Lower treshold temp
for growth
Infective dose
Reservoire
(example)
L. monocytogenes:
2-4 °C
10?-108 cfu
Everywhere
Vibrio parahaemolyticus :
above 8°C
108 cfu
water, sediments
Salmonella spp:
8 °C,
1- 102, 103-106 cfu birds, etc
Shigella spp:
7 °C
10 -105 cfu
Humans
Histamine forming bacteria
0-?
105 (estimated)
Sea water, skin,
process eqp.
Staphylococcus aureus
(toxine production)
app 12 °C
more than 105 cfu/g Everywhere,
mainly humans
Viruses (human pathogen)
?
app 106
Humans, water
•The water temperature varies between areas – ”living seafood” has the same
temperature as the surrounding water.
•The temperature in fish counters is higher than the threshold value for growth in
many countries
Some pathogens are more relevant in
some areas than others:
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The threshold temperature for growth of specific
pathogens explains why seafood from cold water
areas contain lower levels and fewer pathogens than
seafood from temperate water areas, even if both
areas are in polluted areas.
Example: Human pathogens Vibrio spp and
Salmonella spp are hardly present in cold water
areas, but represent food safety risks in warmer
areas.
Emerging pathogens are not only due to increased
travelling, production hygiene and pollution, but
also to changed temperatures/climate.
Pathogens in mussels and oysters
Filter
large amounts of water,
accumulate pathogens in the water in
the muscle, i.e. the part we eat.
Oysters are eaten raw, and are
therefore high risk products
Improve food safety:
Monitoring: Analysis of sea water to
detect pathogens and algal blooms, etc
Avoid muscle production/farming in
polluted areas to reduse the risk of
contamination from humans.
Fresh fish is not on the list of risk products,
but traces of pathogens, including L.
monocytogenes may be present on
Gills
Skin
Sea water
On equipment
In slaughter houses
In processing plants
Photo: T Skjerdal
and grow to infective doses during processing, storage and
distribution
”Distribution” of levels of human pathogenic
microbes early and late in the farm-to-fork chain
(illustration, not based on real data)
By slaughtering and primary processing
After distribution and secondary processing
at abuse temperature
at ideal temperature
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2
3
4
5
6
Human pathogenic bacteria level in fish (log cfu/g)
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Abuse
temperature
in this
example:
Temperature
above
threshold
value
for growth
The lower
threshold
temperature
for growth,
the higher
risk of high
levels in the
product
CFU/g fish
1000000
Spoilage bacteria
10000
100
0
1
Human pathogen
2
4
6
8
10
Days at 5-8°C
Unsafe product
100000000
Sensory spoiled
Will a fish with high levels of pathogens be
consumed, or sorted out due to spoilage?
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Raw fish becomes spoiled before it is unsafe to eat (raw) – as long as the
consumers are able to recognise spoilage
Preserved products may become unsafe before spoiled if human
pathogenic bacteria are present in low levels
Preservation may be a sieve where pathogens can go
through
Example: Histamine poisoning due to
preserved tuna
Histamine production is a problem only in fish that contains high levels
of histidine, the precursor for histamine. Species: tuna, sword fish,
mackerel, (herring), etc.
 Similar for other biogenic amines:
 Histamine is formed both in chemical and microbial reactions.
 Cold adapted histamine producing bacteria:
● Morganella psychrotolerans (identified by Emborg og Dalgaard,
Journal of Food Protection 2006)
● Photobacterium phosphoreum, present in most fish species
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Spoilage indicator for tuna: loss of fresh red colour. But: the colour
can be maintained during storage by use of preservatives.
Therefore, histamine can be formed even if the fish look fresh.
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Analysis of histamine (Based on Dalgaard, 2007):
● The level is highest near the belly flaps, lowest in the tail part of
the fillets.
● The level of histamine is nearly always higher than for other
biogenic amines
Is there any risk that a native fillet may cause a
food safety risk before the fish is spoiled?
Spoilage of fresh fish
 Specific spoilage bacteria in fish
(for further reading, see review papers of Gram, Dalgaard and Huus, International journal
of Food Microbiology, 1993 and 1996)
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Sulphide producing bacteria; mainly Shewanella putrefaciens.
● Grows in air and vacuum, but not in MAP
TMA forming bacteria; Photobacterium phosphoreum and
Shewanella putrefaciens
● P. phosphoreum grows in air, vacuum and MAP
Both kinds:
● Present in sea water, skin mucous, etc
● Grows even during ice storage.
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2
4
8
16
32
64
128
Ca 250
500
1000
2000
4000
8000
16000
32000
64000
128000
Ca 250000
500000
1000000
2000000
4000000
8000000
16000000
32000000
64000000
128000000
Growth rate of sulphide producing bacteria in fish
Max 24 doubling times before most consumers consider the fish
spoiled
Doubling time depends on temperature:
Temperature
Doubling time
0 °C:
24 doubling times
ca 15 hours
ca 15 days
4
”
ca 6
”
ca 6
”
7
”
ca 4
”
ca 4
”
10 ”
ca 2,5 ”
ca 2,5
”
20 ”
max 1 ”
max 1
”
Based on data from own experiments and data from Fiskeriforskning and DIFRES.
10 millions SPB per gram fish makes it smell putride/spoiled
Temperatures above threshold for growth
Time for 100 fold doubling of Listeria spp in
inoculated salmon, including the lag period.
0 °C
No growth observed
4 °C
8 °C
12 °C
0
1
2
3
4
5
6
7
Days
But, as fish spoils rapidly, will fish stored at such
conditions be sold to consumers?
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Risk of Listeria monocytogenes infection
depends on:
Amount of Listeria
monocytogenes in food
consumed
A fraction of the bacterium
survives through stomach acid
conditions
Ability to cause invasive
infection and illness
Sushi study:
Which fish quality is sold for preparation of sushi at
home – can the Listeria dose reach 100 cfu/g?
Shopping study:
Person 1: Ordered fish without asking
questions
Person 2: Asked for fish suited for
preparation of sushi for a 40 year
birthday with one pregnant guest.
Visited 19 shops
Foto: Taran Skjerdal
Results
Same quality offered for all kinds of dishes
Poor knowledge about food safety among the staff
5 % of the samples appeared to be stored at conditions
allowing a 100 fold increase of L. monocytogenes
Estimated the time-temperture history:
Combine analyses with traceability data, and
calculate quality and safety information.
Temperature,
contaminated during
production or older
than informed
Stored on ice!
(log SPB)
Quality degrading parameter
Stored at abuse
Storage time (days)
Traceability data: Catch/Slaughter date
predictive model of a quality parameter related to time and temperature,
test method for verification of predicted quality parameter value
Developed by T. Skjerdal during work in DNV
Analysis methods for sulphide producing
bacteria applied: NMKL 96 og FAST
log(SPB)
Sulfidproduserende bakterier i islagret torsk
6
5
4
3
2
1
0
Predicted level
Iron Lyngby Agar, NMKL 96
FAST
day 1
day 5
Skjerdal og Ranneklev, 2006
day 11
Sushi study part 2:
Does the preparation of sushi increase the risk that L.
monocytogenes survival in stomach acid condition?
Sushi prepared from
 Acetic acid marinated rice (low pH)
 Wasabi (also acidic)
 Slices of raw fish
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Main human barrier for food borne Listeria: Stomach
acid
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Reported in literature: Light acid stress leads to an
increased tolerance to stronger acid.
Survival of L. monocytogenes in synthetic stomach acid
Naturally contaminated salmon (<10 cfu/g)
Sushi
Undercooked minced fish
raw fillet
Listeria monocytogenes
(cfu/g)
10000
100
1
storage of product prior to stomach acid condition exposure (time and temperature
prior to acid exposure
10 min in acid
30 min in acid
Acid adaptation and/or components in other sushi ingredients increase
the tolerance of L. monocytogenes to stomach acid conditions stress
Storage of fish for some days at abuse temperature (orange
background) increase the risk of Listeria survival
Survival of L. monocytogenes in stomach acid conditions
7 days at
7°C
day 0
raw fillet
+7 days at
7°C
+7 days at
0
day 0
+7 days at
7°C
+7 days at
0
day 0
+1 day at
5°C
Undercooked minced fish
day 0
+ 1 day at
5°C
Sushi
day 0
Listeria monocytogenes (cfu/g)
Inoculated salmon
Storage of product prior to stomach acid condition exposure (time and temperature)
prior to acid exposure 10 min in acid 30 min in acid
Aspects to consider in food sampling (1):
Contamination in the slaughter house and
process environment
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Origin categories:
● Raw material (fish and water)
● Human handling
● Equipment, floor, roof etc (indirectly from humans or raw
material)
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Will the entire batch or only some fishes be contaminated?
● Direct human contamination: Few fish
● contaminated raw material and equipment: The entire
batch may be contaminated
The product from primary processing is the raw material in
secondary processing
Aspects to consider in food sampling (2):
Effects of processing, including preservation, on
human pathogenic microbes in food
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Preserved products are likely to contain higher levels of human
pathogenic bacteria due to
● Longer storage period – often at abuse temperature
● Temporary process hurdles like light heat treatments
remove spoilage flora but may also give the surviving
bacteria a ”growth kick” if slowly chilled.
● More processing leads to increased risk of contamination
from humans
● Product often consumed without traditional heat treatment
or other treatments eliminating the microbes – ready-to-eat
trend
● etc
Consequenses of international trade and
processing in seafood analysis and
legislation
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The food legislation including limit values for pathogens vary
between countries (e. g. Listeria, zero tolerance in some
countries, 100 cfu/g in others).
Some times there are different demands for semifinished
products and final products.
The demands from the customers are often higher than those
from the food authorities.
The same demands may be requested for seafood from
different parts of the world, even though the pathogens of
relevance differ in different parts of the world.
Limited traceability: suppliers and customers do not always
trust each other. Indicator organisms for assessment of process
hygiene, freshness and preservation, including masking, are
important
Due to rapid spoilage and long travel distance: The analysis
time and/or paper documents important for decisions.
Listeria risk management by food
authorities
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Give food advices to (vulnerable) consumers.
Upcoming: In Norway: Catch/slaughter day on label
from 2010
Upcoming: International legislation: Introduce
performance objectives (PO) and food safety objectives
(FSO) for intermediate products and final products,
respectively.
● What should the levels be? 10 cfu/g as PO for salmon
intended used for ready-to-eat products and 100
cfu/g as FSO in final product? No Listeria in
production environment samples if the fish that is
going to be served to vulnerable consumers?
● Relevant for other bacteria than Listeria
● Many questions – some will be studied in the new EU
project BASELINE starting in 2009.
Listeria risk management by companies
Keep Listeria levels as low as possible, both in products
and production environment.
● NB: Cleaning and desinfection may not be sufficient to
control the level if there is a reservoar of L.
monocytogenes in the processing plant.
 Upcoming: International regulation (Europe at least):
Companies will have to carry out risk assessment of
products based on durability studies and/or literature
data to prove that L. monocytogenes
● Is not able to grow in the product, or
● Can not reach maximum 100 cfu/g during the shelf life
● More companies can do the studies together. Samples
with naturally contaminated are most valuable.
Studies started at VI already.
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Summary
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Seafood is healty food, and the solution to the food
safety challenges is not to stop development of
ready-to-eat products or international trade, but to
manage the food safety risk risk.
Selection of good indicator parameters and analysis
for their quantification are very important.
Thank you for your attention and invitation