Is the Sea Urchin a Villain of the Sea? Or a Savior of Humanity? — The Forefront of Gourmet Food and Medical Applications Brought by Sea Urchins @Villain (Former Professor, 755th Day of Retirement)
Disliked by children, captivating to adults — The “taste gap” of sea urchins
I previously watched the NHK "The Backyard" special on the "Kanagawa Prefectural Fisheries Technology Center," and wrote on note about the dark-culture of tiger pufferfish, as well as the issue of seaweed bed destruction caused by sea urchins and the story of sea urchins eating cabbage. This time, NHK's "Villain's Argument" featured the sea urchin as a villain. The program began by introducing a ranking of foods children dislike. Sea urchin was the only seafood to make the top 7, being treated as "the most hated creature in the sea." On the other hand, for adults, it is a staple of high-end sushi. I also laughed at MC Tomohito Yashima's story about trying to show off at a sushi restaurant by saying, "Order whatever you like," only to be told, "Then I'll have the sea urchin," and thinking, "Hey, wait a minute." Furthermore, sea urchins are not just limited to Japanese sushi, sashimi, and sea urchin bowls; they are now gaining support from gourmets around the world as the "foie gras of the sea." In France, fresh raw sea urchin is placed on French bread or processed into mousse or hollandaise sauce. In Italy, it is used to add umami to risotto and pasta. The gap between it being such a delicacy and yet disliked by children is what makes it interesting. (Please also see the title photo and the photo below: Note 1)
In fact, when I was a child, I wasn't very fond of the unique briny smell of sea urchin. I think it was around the time I turned 30 that I started to like it. There was an academic conference in Hokkaido, and I went to the Nijo Market near my hotel in Sapporo several times with my students. At that time, I was surprised by the deliciousness of the sea urchin bowl I ate along with a salmon and salmon roe bowl. There was no briny smell at all, and it had a creamy, melting texture—it was truly "sweet," just as I had heard in TV food reports. Since then, it has become one of my favorite foods. Unfortunately, however, I have rarely had the opportunity to eat market-priced sea urchin at a sushi restaurant.
The surprisingly unknown, intricate body structure of the sea urchin
The program also explained the body structure of the sea urchin in detail. For example, I thought all sea urchin spines were of the same type, but apparently, there are three types. In addition to the regular spines, there are "pedicellariae" that have claw-shaped tips. When debris gets stuck on the body surface, these pedicellariae grab and discard the foreign object like a UFO catcher. It is also said to be used for defense against natural predators. Also, what extends from between the spines are the "tube feet." The tips are suction cups, which allow them to pull in seaweed or cling to rocks so they aren't washed away by waves. Sea urchins are not just creatures that sit still covered in spines; they live by using various tools. Furthermore, sea urchins have a top and bottom, and are properly equipped with internal structures such as a mouth, anus, and internal organs. By the way, the yellow part we eat is the gonad. Looking at it again, I realize that the sea urchin is a creature with a very intricate structure. (Please also see the photo below)
<Postscript> Due to the rise in seawater temperature caused by global warming, the metabolism of sea urchins is promoted, and their activity has become abnormally intense, with their breeding season extending from the original July-August to June-September. As a result, "seaweed bed destruction (desertification of the sea)," where mass-produced sea urchins eat up all the seaweed in the shallows, is becoming a serious problem in various parts of the world, including Japan. When rich seaweed beds are lost, it also deals a major blow to the diverse fish and shellfish that lived there. Furthermore, the "blue carbon" function, where seaweed absorbs carbon dioxide, is also lost. On the other hand, the sea urchins themselves that have eaten all the seaweed are in a state of extreme starvation, becoming "thin sea urchins" where the edible parts do not develop. (Please also see the photo above and the bottom right)
Miura cabbage, Aomori sake lees, Okinawa mango — New generation sea urchins born from "local feeding"
The sea urchin that appeared as a villain on the program began to tell its own "side of the story." The unique briny smell and bitterness of sea urchins are caused by the scent component "hexanal" contained in their original food, seaweed, transferring to their bodies. In other words, by feeding them something other than seaweed, the taste can be greatly improved. For example, when fed cabbage, the bitterness is significantly reduced and the sweetness increases. The guests actually tasted it, and it was well-received, with the briny smell suppressed and a faint scent of cabbage, making it easy to eat even for those who dislike sea urchin. Also, sea urchins fed Sanuki udon apparently lost their bitterness, and the taste became richer, mellower, and stronger in umami. (Please also see the photo below)
In this initiative, non-standard cabbage that was scheduled to be discarded due to discoloration or damage in places like the Miura Peninsula is being used as feed. In other words, it is also leading to the reduction of food loss. Furthermore, by removing and culturing the sea urchins, the recovery of seaweed beds can also be expected. If the seaweed beds return, the function of seaweed absorbing carbon dioxide will also be restored. It can be said to be a groundbreaking initiative that simultaneously realizes the reduction of food loss on land and the preservation of the marine environment.
Spines and shells are also useful — The potential hidden in sea urchins in the medical field
Another "side of the story" for the sea urchin as a villain was that its spines and shells are being researched and utilized in the medical field. It is said that they may be useful for treating intractable diseases and regenerating bone.
One is the medical application of the pigment "echinochrome" contained in sea urchin spines. Echinochrome is said to have the effect of suppressing excessive active oxygen in the body and reducing inflammation. Therefore, it is expected to be a therapeutic drug for "uveitis," an intractable eye disease that carries the risk of blindness. In animal experiments, it was shown to not only suppress the symptoms of uveitis but also potentially have fewer side effects, and research was underway. (Please also see the photo below)
Another application is the use of discarded sea urchin shells, or skeletons, in bone regenerative medicine. Sea urchin skeletons have a porous structure that is very similar to human bone. It is said that large holes through which osteoclasts and other cells pass are intricately intertwined with small holes through which blood and nutrients pass. The program also introduced the process of bleaching and special processing. When sea urchins are soaked in bleach, the proteins dissolve, and the spines fall off in tatters after about an hour. This reveals a sea urchin skeleton that reminds one of Yayoi Kusama's pumpkin works. It has been confirmed in culture experiments that when this is specially processed to create bone regeneration blocks and implanted as a scaffold for damaged areas such as fractures, cells become active and new bone repair progresses. (Please see the photo below as well.)
In this way, I am surprised that parts of the sea urchin, which are often thought of as dangerous spines or waste, are creating new value as medical materials that save humans.
Are sea urchins that eat mangoes sweet?
In this feature, what I was particularly interested in was the aquaculture of so-called "local sea urchins," which are raised by feeding them various ingredients in different parts of the country. According to the diagram shown in the program, asparagus is used in Hokkaido, sake lees in Aomori Prefecture, and mangoes in Okinawa. I didn't think sea urchins were this omnivorous, so it was quite a shock. It is also interesting that sea urchins, which are a luxury food item, are raised by eating other luxury food items. In particular, I feel like sea urchins that have eaten mangoes, a fruit, would surely become delicious. I would definitely like to try them someday. Well then, until next time.
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Note 1: From the NHK "Villain's Argument" feature on "Sea Urchins"