The Food and Environmental Hygiene
Department (FEHD) and the Consumer Council conducted a joint
study on histamine in canned fish and tuna sandwiches with
an aim to assess the health risk of histamine in canned
fish and tuna sandwiches. As improper handling and storage
of canned fish after opening may result in high level of
histamine, the study also explored the measures for reducing
their formation.
2. Histamine is formed by conversion of
the free amino acid histidine in muscle of dead fish with
the presence of certain bacteria, mainly species of the
family Enterobacteriaceae such as Morganella morganii.
Consumption of fish containing high levels of histamine
can cause foodborne intoxication, known as histamine poisoning
(or scombroid fish poisoning). Histamine poisoning occurs
throughout the world and is reported sporadically in Hong
Kong.
3. In our study, the levels of histamine
were measured in 23 canned fish samples (12 tuna, 5 sardines,
3 mackerels and 3 anchovies) and 20 tuna sandwiches samples
which were sampled from different major retail outlets and
restaurants in May 2005. To devise measures for reducing
the formation of histamine, further experiment was performed
in canned tuna samples which were kept under 3 different
storage conditions (2oC, room temperature and
33oC respectively) with inoculation of the bacteria
Morganella morganii. All the laboratory analyses
were done by the Food Research Laboratory of FEHD.
4. Results showed that histamine levels
in all the canned fish and tuna sandwiches samples were
well below the maximum level in Codex standards. However,
further experiment showed that high levels of histamine
sufficient to cause histamine poisoning were detected in
the tuna fish samples that were kept at room temperature
for 24 hours, or at 33oC for 6 to 8 hours.
5. The public and the trade are therefore
advised to observe personal and food hygiene to prevent
cross contamination. Tuna sandwiches and opened canned fish
should be stored at 4oC or below and be consumed
as soon as possible. The trade is also advised not to store
/ display the tuna sandwiches at room temperature for more
than 2 hours.
September 2005
Risk Assessment Section
Food and Environmental Hygiene Department
Last
revision date: 16-09-2005