Ammonia will be produced by the breakdown of urea and is particularly
prevalent in those fish that use it as an osmoregulator, sharks and rays for
example. In these fish it can appear immediately after death, disappear,
then returns strongly as spoilage progresses. My point being that even
fresh fish can have a taint, although storage conditions (close packing, or
lack of ice may exacerbate the condition). I would, however, normally take
the presence of ammonia as an indicator that the fish is of poor condition.
Even if the odour dispersed it will probably have had a deleterious effect
on the market.
If the fish was not cartilaginous then the presence of ammonia certainly
means the fillets were off. The Torry Scale indicates ammonia in raw fish
developing at a score of 2-3 out of 10 (where the break point between
acceptable and not acceptable is 6 for round white fish). At this the
cooked product would be soft or sloppy, bitter and almost certainly smell
sufficiently strongly to dissuade the consumer before they got too close.
The Tasmanian system did not go into such depth the last time I looked at
it.
There are many references to ammonia in fish both from the spoilage aspect
(early material from Connell et. al., Torry Research and recent material
Peter Howgate - on this list) and from the biological (try Moyle, B P., and
Cech, J. J. 1996. Fishes an introduction to Ichthyology).
----- Original Message -----
From: Adam Simpson <AdamS@ahsl.co.nz>
To: <seafood@ucdavis.edu>
Sent: Wednesday, May 17, 2000 3:24 AM
Hi List
I have received several complaints relating to a very strong ammonia smell
associated with fillets from various different types of fish. I believe
this is an indication of spoilage and have also been made aware it relates
to the gutting of the fish. Is there any literature or comments out there
to provide me with further explaination/clarification? Could this smell
ever reach the stage of causing a physical reaction such a burns to the
mouth?
Much appreciated
Adam Simpson
Health Protection Officer
Public Health, Auckland Healthcare Services
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