Puffer Fish and Fish Maw
Puffer Fish and Fish Maw
(CMA Testing and Certification Laboratories)
Centre for Food Safety recently detected “tetrodotoxin” (TTX) from two kinds of puffer fish maw. The government therefore instructed the trade to stop the sale of affected products, and called on the public to stop consuming the problematic fish maws.
Image Source：Mingpao, 2016
What is Tetrodotoxin?
Tetrodotoxin is a neurotoxin, named after puffers with which it is commonly associated. Toxicity of puffer fishes varies by species, habitat and season. Generally speaking, liver and ovary of puffers are the most poisonous parts, followed by skin, intestine and muscle. During puffer fish processing, its swim bladder can become toxic due to contamination by other TTX-containing internal organs.
TTX is a deadly poison, 1250 times more toxic than (sodium) cyanide, and extremely heat stable. It cannot be completely destroyed even after continuous heating at 100oC for 5 hours. Symptoms of tetrodotoxin intoxication (e.g. dizziness, numbness, nausea, vomiting, diarrhoea, epigastric pain, convulsions and irregular heart rate) can appear after ingesting 0.2 mg TTX. Moreover, the lethal dose of TTX is just around 1 to 2 mg.
Fish Maw Derived from Toxic Fish
Many tetrodotoxin poisoning incidents in the past were due to consumption of toxic puffer fish. However, it is well noted that TTX could also present in other aquatic animals（e.g. goby and shellfish）.
Image Source：Centre for Food Safety, 2010
Fish maws, in general, are not toxic. It is absolutely safe to consume fish maws made from swim bladders of non-toxic fishes (e.g. white croaker and yellow croaker). However, fish maw derived from a puffer fish might be toxic, depending on its species, origin and processing method. If a fish maw processor cannot identify a toxic puffer species and its toxic organs, and/or fail to protect the swim bladders from contamination during puffer fish processing, the resulting product is likely toxic.
How to Prevent
As such, traders should not use fish species of unknown origin or a fish that he has no idea at all to make fish maws. During the stages of sourcing, fish processing and retail, extra attention are required to select non-toxic fish species and avoid mixing with the toxic ones.
On the other hand, several studies indicated that the tissues and organs of farmed puffers raised with artificial feeds were non-toxic. This suggests that farmed puffer fish is a safer raw material for fish maw production than wild puffer fish.
n order confirm the food safety of raw materials and fish maw products, different TTX detection methods can be used e.g. mouse bioassay, immunoassay and chemical method (e.g. LC-MS/MS).