Where does tetrodotoxin come from?

The shad, swordfish and puffer fish, also known as the "Three Seasons of the Yangtze River", have been the delicacies that gourmets have been eager for since ancient times.

In the Song Dynasty, Su You's poem "Night Scene of the Spring River in Hui Chong" is a proof: "Peach blossoms are three Liang outside the bamboo, and the duck prophet warms the spring river. Artemisia sphaerocephala has short reed buds all over the ground, which is the time for puffer fish to go up. "

Pufferfish enjoys the reputation of "king of fish" and its high nutritional value is well known. It is rich in protein, unsaturated fatty acids, DHA, EPA and other nutrients, but the fat content is very low.

However, puffer fish is delicious, but it is poisonous. Every year, there are several news reports that diners take risks to eat puffer fish, which leads to poisoning, ranging from hospitalization to death, which also makes many people "talk about puffer fish". But what is puffer fish? Why is it poisonous? How can we safely taste puffer fish without poisoning? Let me tell you something about puffer fish.

Although most people have heard the name of puffer fish, you may not know whether the correct spelling is puffer fish or river fish.

Some people think that the correct spelling should be river carp, and the word Tun on the right is next to the word fish on the left. But the puffer fish is the real name!

Because the puffer fish has a special skill, when it is frightened or angry, it will quickly swallow a lot of water or air, making itself round and floating on the water, much like a fat pig floating on the water. The ancients called it "puffer fish", and the word "Qu" was invented by later generations, which was mainly used to name this fish in taxonomy.

Broadly speaking, taxonomically, squids, including the largest bony fish-Tijuana dolphin, Scolioma with a bad temper, horse-faced squids commonly known as piranhas and stingrays, can all be said to be puffer fish.

But in a narrow sense, only puffer fish that live in fresh water, especially several kinds of "fugu orientalis" that we often regard as edible fish, can be called "puffer fish", and the most common one on the table is "fugu orientalis with dark lines", mostly puffer fish in Su's poems.

Then why is puffer fish poisonous?

The toxin in puffer fish is called "tetrodotoxin", which is a very strong neurotoxin. Only about 2 mg is enough to kill people. The content of tetrodotoxin in an adult female puffer fish can make you die more than 30 times. After poisoning, symptoms such as numbness of tongue and fingertips, dizziness, vomiting and diarrhea may occur, and in severe cases, numbness of limbs, unconsciousness, blood pressure drop, fainting and even death may occur.

Moreover, no antidote has been invented yet. It is said that the ancients found that after poisoning, they would pour dung juice to induce vomiting, but in modern times, the residual toxins in the body were mainly removed by gastric lavage. Tetrodotoxin is not only powerful, but also extremely stable, which cannot be destroyed by ordinary cooking methods. This makes many diners stop watching puffer fish.

But the good news is that puffer fish itself has no tetrodotoxin, and it is not toxic all over the body.

At present, the mainstream research view holds that puffer fish is a tetrodotoxin produced by some bacteria in the body, which is a process of enrichment and gradual accumulation in the body through food. The toxin mainly exists in organs such as ovary, liver, blood, eyes and skin, and the muscles of puffer fish are almost nontoxic.

In Japan, puffer fish dishes can only be sold in special restaurants, and chefs who handle puffer fish must undergo years of professional training before they can make puffer fish dishes for their guests. Moreover, there are very complicated and delicate steps to deal with puffer fish:

1. Wash puffer fish with running water, remove body surface mucus and cut off fins.

2. Carefully insert the fish skin and fish meat with a sharp knife, separate them, and peel off the fish skin to avoid damaging the fish skin or fish meat.

3. Dry the water on the surface of the fish with a towel, and then take out the fish's eyes.

4. Carefully take out all internal organs, and don't break them, otherwise the toxin may pollute the fish.

5. Open the skull of the fish and take out the fish brain.

6. Wash the fish repeatedly with running water to remove all blood and body fluids.

7.？ Check at least twice before cooking to confirm that all toxic organs have been removed and properly destroyed.

Even if you are so careful, you will occasionally hear that someone is poisoned by puffer fish, especially in spring. This kind of news is the most. Why?

There are two reasons, one is that spring is the traditional season to eat puffer fish, and the other is that puffer fish is the most toxic in spring.

Take fugu obscurus as an example, they usually migrate to fresh water to lay eggs in spring, and they need to accumulate a lot of fat in their bodies during the breeding season. At this time, the fish is the most abundant, not only the output is large, but also many people eat puffer fish and there are many reports of poisoning.

Moreover, the ovary of puffer fish is the organ with the highest toxin. At this time, in order to lay eggs, the ovaries of female puffer fish will mature, and the volume and mass will increase, which will increase the chance of poisoning.

So is it possible for us to taste puffer fish safely? The answer is yes.

At present, after years of efforts, scientists engaged in fishery technology in China have artificially cultivated four kinds of puffer fish, namely, fugu obscurus, fugu rubripes, fugu bifocalis and fugu fugu fugu, and cultivated drug-free strains.

In the artificial environment, puffer fish is completely isolated from the outside world and fed with artificial feed, which makes it impossible for puffer fish to obtain toxin-producing bacteria. After several generations of selection, the toxins in their offspring are gradually reduced, and finally a stable and non-toxic puffer fish is obtained.

20 16 The former Ministry of Agriculture of China issued the Notice on Filing the Source Base of Pufferfish Culture, and the former Ministry of Agriculture and the State Food and Drug Administration jointly issued the Notice on Conditionally Opening the Culture and Processing Operation of Fugu rubripes. Since then, puffer fish has been officially listed as conditionally open in China.

The document has made very strict management requirements for the opening of puffer fish, including: the source base of puffer fish should be put on record, the processing of puffer fish should be evaluated, the puffer fish should be equipped with safe processing procedures, and the quality of puffer fish products should be standardized.

Draw a key point. If you want to taste puffer fish safely, you must choose cultured fish that meet the above requirements and find a restaurant specializing in puffer fish to ensure that there is no danger of poisoning while tasting delicious food.