Chemical Hazard : Scombrotoxin (Histamine)

Chemical Hazard : Scombrotoxin (Histamine)

Chemical Hazard : Histamine

Scombrotoxin (Histamine): Scombrotoxin is a foodborne toxin most associated with the consumption of certain fish species, e.g. mackerel and tuna.

Histamine is a biogenic amine and can be produced during and/or storage of fish and certain other foods, usually by the action of spoilage bacteria.

Certain bacteria (Photobacterium phosphoreum and Raoultella planticola) produce the enzyme histidine decarboxylase during growth. This enzyme reacts with histidine, a naturally occurring amino acid that is present in larger quantities in some fish than in others. The result is the formation of scombrotoxin (histamine).

Once the enzyme histidine decarboxylase is present in the fish, it can continue to produce histamine in the fish even if the bacteria are not active. However, once histamine is produced, it cannot be eliminated by heat (including retorting) or freezing.

The process of decarboxylation is induced mainly by enzymes produced by gram negative enteric bacteria (e.g., Morganella morganii, Escherichia coli, Klebsiella spp., and Pseudomonas aeruginosa) that are found in the intestine or in the skin of the fish.

Occurrence in Foods: Scombrotoxin is most often associated with scombroid fish, especially tuna, skipjack, bonito and mackerel. Also, other non-scombroid fish such as sardines, herring, pilchards, marlin and mahi-mahi. There have been reports it may also occur in salmon species.

The toxin is not limited to fresh and frozen fish. It may be present in canned and cured fish

products at high enough concentrations to cause illness.

Effects on Health:

If the histamine is ingested in large quantities, it causes an anaphylactic reaction with a variety of symptoms from moderate to severe to life-threating.

Symptoms of scombrotoxin poisoning include nausea, vomiting, diarrhoea, hives, itching red rash (flushing). It may also cause an oral burning sensation or peppery taste in the mouth. Include tingling or burning in or around the mouth or throat; rash or hives on the upper body; drop in blood pressure; headache; dizziness; itching of the skin Hypotension including light headedness, dizziness or fainting are also known symptoms.

Histamine concentrations near or above 100mg/100g are typically noted in actual illnesses. Regulatory guidelines have not been established for all the various fishes of concern, but 50mg/100g is inferred from the U.S. FDA's poisonous action level for tuna.

Control and Preventive Measures:

Some of the histamine-forming bacteria are halotolerant (salt tolerant) or halophilic (salt loving). Some are more capable of producing histamine at elevated acidity (low pH). As a result, histamine formation is possible during processes such as brining, salting, smoking, drying, fermenting, and pickling until the product is fully shelf-stable. Refrigeration can be used to inhibit histamine formation during these processes.

Histamine-forming bacteria are facultative anaerobes that can grow in reduced oxygen environments. As a result, reduced oxygen packaging (e.g., vacuum packaging, modified atmosphere packaging, and controlled atmosphere packaging)

Chilling: One of the key measures to control histamine production in fish is rapid chilling as soon as possible after death especially if the fish had been exposed to warm water. Fish that have been gutted and gilled before chilling should be chilled to 4.4 ˚C (40˚F) or below as soon as possible but no more than 12 hours from the time of death.

Supplier Control

Purchase from reputable suppliers who store the fish on ice or under refrigeration.

Receive product at refrigerated temperatures <5°C (41°F).

Good Hygiene Practices

Careful handling of fish to avoid damage to muscle tissue as puncture wounds in fish can introduce contamination bacteria into deep tissue where large concentrations of histidine are available.

Good hygiene at processing and preparation stages along the supply chain such as cutting, or packing is important to prevent contamination of fresh fish, or recontamination of frozen and cooked fish.

 Testing Method

Testing by chemical methods such as HPLC or ELISA and other immunological techniques can provide some assurance of histamine levels. Variability in histamine levels in a single fish mean that very large numbers of samples must be taken.

Reference

USFDA