Don’t think that eating sashimi with mustard is safe and hygienic!

In recent years, with the popularity of various short videos on gourmet food, eating raw seafood has become a popular online food among young people. Whether it is Thai-style raw marinated seafood or Chaoshan Shunde sashimi, in the comments of the food videos of young men and women who visit the stores, countless people are eager to check in.

A view has gradually formed in everyone's mind that only by eating raw seafood can you taste the most original and sweet taste of seafood delicacies without cooking, and satisfy your appetite to the greatest extent. So the question is, is it really safe and hygienic to eat raw seafood?

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Parasites, bacteria, neither can be left out

The fish, shrimp, crab, shellfish and various freshwater aquatic products that we come into contact with in the market on a daily basis basically contain a large number of bacteria and parasites. Especially those freshwater aquatic products that are farmed on a large scale, because the breeding sites are often relatively closed and static water bodies, so there are more parasites. And many of these parasites can also parasitize the human body and affect human health.

In freshwater aquaculture, the most common parasite that can cause disease in humans is the liver fluke, whose scientific name is Clonorchis sinensis. It often changes hosts three times in its lifetime. The eggs of the liver fluke use freshwater snails as hosts. When it develops to the cercariae stage of the larvae, it often leaves the original host and parasitizes in the body of fish to continue to develop into metacercariae (cercariae and metacercariae are different stages of the development of liver fluke larvae). If the second host is eaten by a mammal, the liver fluke will choose the corresponding mammal as the final host. And humans are also on its final host list.

Image source: Paixin Creative, Yitu.com

After the liver fluke metacercariae enter the human body, they will enter the hepatobiliary duct through the common bile duct, blood vessels or through the intestinal wall when they reach the duodenum, and then develop into adults in about a month. The life span of a liver fluke is as long as 20 to 30 years, which means that once the liver fluke parasitizes a human, it will live "intimately" with the host for more than 20 years.

For the human host, these 20 years of "intimate" days can definitely not be considered a "honeymoon period". Liver flukes parasitize in the liver and bile ducts. The daily excretion, secretions and eggs produced by the liver flukes can cause inflammation and infection of the bile duct epithelial cells. When the lesions develop to the later stage, they may cause cholecystitis, gallstones, and biliary cirrhosis. When humans are infected with liver flukes, they will show symptoms such as abdominal pain and bloating, pain in the liver area, and loss of appetite. In severe cases, the overall appearance may be visibly thin, but the abdomen is swollen.

Image source: Paixin Creative

Compared with freshwater aquatic products, the probability of seafood containing parasites is lower due to the stronger flow of water in the ocean and the higher salt content of seawater, but this does not mean that the probability is zero. The most common parasite in seafood is Anisakis.

Like liver flukes, Anisakis will change hosts at different stages of growth and development. When they are larvae, they like to parasitize in marine fish, and when they reach the adult stage, they like to parasitize in the digestive tract of marine mammals such as whales and dolphins. From this perspective, the human body is not the most suitable host for Anisakis. If Anisakis is eaten into the human stomach along with seafood during the larval stage, it will lose the opportunity to continue to develop into an adult.

Image source: Paixin Creative

The problem is that the human body is not a paradise for Anisakids, but it is also not a hell. Anisakids will not continue to grow in the human body, but they will not be killed quickly either - they will remain in the form of larvae, "lying flat and rotting" in the human body, "roaming" idly in the human digestive tract all day long until they die. The process of them roaming in the human digestive tract will cause a symptom called "visceral larva migrans", and patients often show symptoms such as nausea and vomiting, abdominal pain, fatigue and low-grade fever. What's more frightening is that under the current medical level, Anisakids are difficult to kill with drugs and can only be removed from the body through surgery.

In fact, in addition to parasites, seafood may also contain many bacteria that are harmful to the human body, such as the more common Vibrio parahaemolyticus, which can cause acute gastrointestinal inflammation. There is also an even more terrible marine Vibrio vulnificus, a bacterium commonly found in marine shellfish, which can not only infect the human body through the digestive system, but can even spread short distances in seawater and infect open wounds in the human body, causing inflammation that is fatal.

Do spices kill insects? It's just a placebo effect

Many foodies who like to eat raw seafood believe that although there are parasites in seafood, it is fine as long as they are "disinfected" before eating. And the "disinfection" in their minds actually refers to various seasonings, such as wine, vinegar, and garlic in raw and marinated seafood, and mustard in Japanese cuisine. The saying that seasonings can kill parasites mainly comes from the subjective feeling of irritation after people consume seasonings such as wine, vinegar, garlic or mustard. Many people may think that since these seasonings can make people feel irritated, then the small parasites soaked in these seasonings will not be "irritated to death"? But is this really the case?

Image source: Paixin Creative

In fact, the irritation caused by these spices mainly comes from the chemical components. People are more familiar with alcohol in wine and acetic acid in vinegar. The chemical substance that can cause irritation in garlic is mainly allicin, whose scientific name is diallyl thiosulfinate, an organic sulfide. When we cut onions, the smell that can irritate us to the point of tears also comes from this thing.

As for mustard, whether it is the wasabi used in authentic traditional Japanese food or the horseradish used in low-end Japanese food, the irritant in them comes from isothiocyanate, which is also an organic sulfide. It is commonly found in cruciferous plants, such as mustard, cabbage, and kale. This substance brings a spicy and stimulating feeling to the human body.

Wasabi mustard丨Source: Yitu.com

Now that we know the chemical composition of the irritants in various seasonings, let's look at their "disinfection" effects. In fact, whether it is alcohol, acetic acid, allicin or isothiocyanate, they do have certain bactericidal and antibacterial effects, but they are difficult to be effective against parasites in aquatic products.

For example, the most effective drug for liver flukes is albendazole, which is the familiar intestinal worm clearing agent, while there is no specific drug to kill Anisakis. Not to mention the low concentration and dosage of irritating chemicals in the seasonings, their lethality is probably not as good as the stomach acid in the human stomach. Letting the parasites soak in it will at most just give them a bath and pickle them.

Can I still eat pickled food properly?

At present, the only way to effectively eliminate parasites is to create an extreme temperature environment. For example, steaming, boiling, roasting and frying food can create extremely high temperatures to kill parasites, while if you want to eat it raw, you can only create extremely low temperatures before eating.

At present, the ingredients used to make fresh seafood in regular restaurants are often treated with low temperatures below -20 degrees Celsius to kill insects. If you want to enjoy fresh seafood occasionally, try to choose to eat in regular restaurants. If you want to make fresh seafood at home, you must not skip the step of putting the ingredients in the freezer for at least 24 hours before eating.

Image source: Paixin Creative

Of course, low-temperature processing cannot completely eliminate parasite infection, so it is safest to eat fish, shrimp, crab and shellfish cooked at high temperatures. As for freshwater aquatic products, since they have many more parasites than seafood, you should never try to eat them raw, even if they have been processed at low temperatures.

Source: Chongqing Science and Technology Museum

Author: Yang Zhen, popular science writer

Review experts: Huang He, Li Chunli, Chen Tao, Xu Xiaoping

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