Dear Steve and Seafood Listserv Subscribers
There is no doubt that presence of Clostridium botulinum organisms and
spores are a hazard in fish and fish products. Surveys of wild and farmed
fish show the presence of the organism with a very varied prevalence in both
marine and freshwater environments. What seems less certain to me from my
readings of the literature is what the risk is. Sumner, J. & Ross, T.,
(2002, A semi-quantitative seafood safety risk assessment, International
Journal of Food Microbiology, 77, 55-59), calculated a risk estimate scaled
between 0 and 100, where 0 represents no risk and 100 represents all meals
containing a lethal dose of the hazard and allocated C. botulinum in vacuum
packaged fish to a low category with a value of 28. They remark that items
in this low risk category had not been reported to have caused food
poisoning in Australia.
There are a few published reports of the outcome of challenge tests of
vacuum packaged fish in which the products have been surface inoculated with
large numbers of organisms. It is questionable just how much this model
reflects the situation of naturally contaminated products. In most of these
studies the time to production of toxin were compared with the time to
'spoilage'. I have used quotes here because it seems to me that a very
tolerant view of spoilage has been used in these studies. For example Reddy
et al (1997, Shelf life and toxin development by Clostridium botulinum
during storage of modified-atmosphere-packaged fresh aquacultured salmon
fillets, Journal of Food Protection, 60, 1055-1063), gave the time to
spoilage in air packs as 24-27 days at 4ºC. Bear in mind that spoilage at
this temperature is about twice that at 0ºC so this implies a storage life
of around 7 weeks at 0ºC. Even with the tolerant criteria of end shelf used
in these challenge studies it is typically found that the product is at or
beyond its shelf life, that is, is inedible, by the time botulinum toxin is
detected. It should be noted that use of an oxygen permeable film does not
ensure safety. In these challenge test toxin is produced in the control
product in an air pack though later than in the vacuum packs.
The National Advisory Committee on Microbiological Criteria For Foods has
posted a report on Vacuum or Modified Atmosphere Packaging for Refrigerated
Raw Fishery Products on
http://www.fsis.usda.gov/OPHS/nacmcf/past/map_fishery.htm
The summary has the following text:
"The Committee recommends that VAC/MAP technology be permitted for raw
fishery products only when the following conditions are met:
The products are packaged under an established Hazard Analysis Critical
Control Point (HACCP) plan.
Detectable spoilage and rejection by the consumer precedes the possibility
of toxin production.
High quality raw fish is used.
Packaged product is stored at or below 38ºF ( 3.3ºC ).
Product is adequately labeled for storage, temperature, shelflife, and
cooking requirements."
Similar recommendations are made by official food safety agencies in other
countries including the UK. Readers might wish to read the complete report
for its overview of the hazard and risks, the problems of interpreting the
results from challenge tests, and its comprehensive bibliography, (mostly
related to MAP; there are not many studies on vacuum packaged fish).
Peter Howgate
----- Original Message -----
From: "Steve Roberts" <stever@offratel.nc>
To: <seafood@ucdavis.edu>
Sent: Wednesday, March 10, 2004 6:44 AM
Subject: Vacuum-packed chilled fish
> During a recent assignment in a South Asia country I came across a
> number of processors who are packing and shipping by airfreight chilled
> vacuum-packed tuna loins and reef fish fillets. These are shipped in
> styrofoam boxes with gel ice. The products are sent to the UK and few
> other European destinations.
>
> I know that the group has discussed the topic of botulism and
> vacuum-packs / MAP in the past - but I am now wondering if there is more
> recent scientific / technical information available to suggest that,
> with appropriate precautions, this practice is not as hazardous as once
> thought.
>
> I'd appreciate any feedback.
>
> Steve Roberts
>
> Seafood Processing / HACCP / Auditing Consultant
> Gillett, Preston & Associates Inc
> Noumea, New Caledonia
> E-mail: stever@offratel.nc
>
>
>
>
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