Basic Knowledge | Sushiblog－Sushiuniversity

What is Toro Katsuo (Torogatsuo)?

In recent years, sushi menus have seen an explosion of creative names, many of which begin with the word “Toro.” But what exactly is “Toro katsuo (Torogatsuo),” and does it truly deserve the prestigious Toro label?

Toro is an absolute at sushi restaurants and it’s only natural to aspire to such a position. That’s why there are so many sushi dish names that start with “Toro”. The most laissez-faire of these is Toro salmon. In this case the definition of Toro is ignored in an attempt to promote sales. Just as bad is Toro katsuo (pronounced “Toro-gatsuo” in Japanese).

Katsuo is born in the warm southern seas. When it reaches about two years old it migrates north in pursuit of Iwashi and other small fish. There are two routes taken by the Katsuo that come to the seas around Japan. One of the routes rides the Kuroshio Current (a warm current) from around the Philippines, passing by Taiwan and the Ryukyus Islands, arriving in southern Kyushu. From there the Katsuo rarely heads toward the Sea of Japan and instead the majority moves northward on the Pacific Ocean side. The Katsuo migration schedule may shift depending on the temperature of the seawater and how the schools of Iwashi and Aji (which the Katsuo feeds on) are migrating that year. The first group appears around Ishigaki Island about January, then in the seas off the shores of Kyushu and Shikoku between February and March. It then moves to the seas off of the Izu and Boso peninsulas between April and June. It reaches the open seas off the southern coast of Sanriku and Hokkaido between July and September.

Another route follows the Ogasawara ocean current from below the equator in the seas off the shore of Papua New Guinea and the seas around Micronesia to the Ogasawara Islands, along the Seven Islands of Izu and approaching the open seas off the Boso Peninsula. The route then goes northward to join with the routes mentioned above.

It’s the Modori-gatsuo that begins reverse migration toward the south at the beginning of autumn when the water temperatures start to drop. Katsuo has a strong appetite before returning south in preparation for the long trip. Unlike the light-flavored Hatsu-gatsuo, the Modori-gatsuo has plenty of fat and its body fattens up quite a bit. The main fishing locations for Modori-gatsuo are in the northern Pacific, such as the waters off the shore of Sanriku. This is the season when it is truly worthy of the name Toro katsuo when served raw, and nothing else should be called by the same name.

When served at its peak in early autumn, Modori-gatsuo truly lives up to the name “Torogatsuo”—a seasonal delicacy that offers the richness and depth sushi lovers crave.

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Revision date: july 18, 2025

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What is Warisu?

Warisu is diluted vinegar, typically used for gently curing fish in the Sujime process. It is less acidic than undiluted vinegar, making it suitable for preserving delicate textures and flavors. Warisu refers to the vinegar used in Sujime.

The fish is first washed in water, then soaked in vinegar. When working with blue-backed fish, the smell of the fish’s fat is removed from the surface with vinegar that has been used once before (and thus has a low acidity). This is called Suarai. When preparing fish with Sujime, cooled Warisu is used, made either with a 10 to 3 ratio of vinegar to ice, or the same ratio of vinegar to cold water. Vinegar with a high acidity that hasn’t been cut with water only soaks the surface of the fish (denaturing it) and the vinegar does not penetrate to the inside. In addition, if the temperature of vinegar is high, such as during summer, the skin and body of the fish soften. That’s why the vinegar is diluted (acidity is between ph 3.3 and ph 3.7) and used as chilled Warisu.

How sushi chefs adjust vinegar for each type of fish

In traditional sushi preparation, vinegar is not just a preservative—it’s a seasoning tool carefully adjusted by skilled sushi chefs. The choice and dilution of vinegar used in warisu (diluted vinegar for curing) are not fixed; they vary depending on the type of fish, its condition, and even the individual preferences of the guest.

Different fish call for different vinegars. White-fleshed fish such as sea bream or flounder are delicate in flavor and low in fat. Using vinegar that’s too acidic can overpower their subtle sweetness. For these, chefs commonly use warisu made with rice vinegar, which offers gentle acidity and a clean finish that enhances the natural umami of the fish without masking it.

In contrast, blue-backed fish like mackerel or sardines are bolder in character, with strong aromas and rich oils. These require a more assertive approach. Chefs often reach for aged sake lees vinegar (akazu), which has deep complexity from long fermentation. However, because akazu can be quite sharp, it’s usually blended with rice vinegar to strike a balance—removing odor while drawing out flavor.

Fatty fish, such as toro, salmon, or yellowtail, pose a different challenge. Their richness can linger heavily on the palate, so vinegar is used to “cut” the fat and refresh the mouth. In such cases, a slightly stronger warisu—sometimes incorporating grain vinegar—provides the right amount of acidity to balance the richness and keep the dining experience light and pleasant.

But the decision doesn’t end with fish type alone. The condition of the fish also plays a vital role. Factors like the fishing method, season, and time since catch can all influence fat content and firmness. For instance, freshly caught mackerel in the morning may be mild, but by afternoon its oils begin to rise to the surface—prompting chefs to adjust the acidity accordingly. A winter yellowtail (kanburi), with its intense fattiness, might call for a bold akazu blend to bring out deeper umami.

Beyond the fish itself, experienced chefs also fine-tune vinegar based on the guest’s palate. An elderly customer might prefer a milder, smoother vinegar base, while a guest who enjoys bolder flavors or is pairing their meal with sake may appreciate a vinegar with more depth and presence. Some international guests, who may not be familiar with the distinct aroma of fermented vinegar, are served fish cured in blends that are gentler and more neutral in scent.

Ultimately, this level of customization reflects the spirit of sushi itself: it is not a standardized dish, but a conversation between chef and guest, expressed one piece at a time.

At the highest level of craftsmanship, chefs seek to create umami synergy—a phenomenon where the amino acids in vinegar (especially akazu) combine with the natural inosinate in fish to create a flavor experience greater than the sum of its parts. For example, a well-aged flounder paired with a carefully blended vinegar can produce profound depth, richness, and lingering satisfaction. In the language of food science, it’s a case of 1 + 1 = 3.

This thoughtful approach to vinegar usage is one of the quiet but essential reasons why great sushi tastes so perfectly balanced.

After the Sujime of the topping is finished, it is important to place it in the refrigerator and allow the meat to mature slowly. The unsaturated fats in oily fish are particularly prone to oxidation, which leads to unpleasant smells and off-flavors if the fish is not properly chilled and managed. For fish with strong fat, that fat oxidizes faster than the meat can mature, so it must be done very carefully.

What is Sekisaba?

Sekisaba (関サバ) and Sekiaji (関アジ) are ‘designer’ fish known for their high prices.

Of them, Sekisaba is a premium fish that can go for as high as US $50 per fish. So, what kind of fish is Sekisaba and what’s the difference between it and normal Saba (Mackerel)?

Sekisaba is a Saba caught in the Hoyo Strait with a fishing pole by a union member of the Saganoseki branch of the Oita National Federation of Fisheries Cooperative (JF Oita). In other words, Sekisaba is not a type of Saba, but a premium fish created by differentiating the fishing method.

Sekisaba started to become known all over Japan between the late 1980s and early 1990s. Until then, Sekisaba was only known as a commonplace fish that was caught incidentally with Aji and went for US $2 per fish.

However, the Saganoseki branch of JF Oita applied for the first trademark ever in the industry and then grew the brand through methods such as tagging each individual fish by hand. This resulted in recognition of its taste as “Saba that can be enjoyed even as sashimi” (while Saba is generally a fish that loses its freshness easily and not eaten raw), catapulting it to a national constituency After that, the thorough quality management and branding paid off and the price jumped to 10 times that of normal Saba.

The first difference between Sekisaba and normal Saba is that Sekisaba is caught carefully, one at a time. The use of ground bait is also banned so that the Sekisaba won’t eat anything but the natural diet (avoiding odor). Each fisher is only allowed to use fishing lures they make from fish skin or ragworms. Fish caught in this way are let out into a live holding tank on the ship and brought to the fishing port alive. After arriving at the port, the tank on the ship is checked, the fish size is looked at from the water surface and the approximate weight is measured. This method is called “Tsurugai”. This is because when the fish is placed on a scale, it struggles violently and can injure itself. The fish are allowed to calm down in the tank (called Ikekoshi) for a day at the fishing port. At the time of shipping, Ikejime is performed, in which a knife is put into gill parts, the spinal cord is cut, and then it is submerged into saltwater and the blood is let out. After that a processing method called Shinkeijime is performed in which a wire is inserted into the spinal cord to put the fish in a state of asphyxiation. Therefore, there is little damage to the fish, maintaining the freshness. When it is transported to the place of consumption, the temperature is kept at 5°C (41°F). This is because the fish does not lose its crunchiness compared to when it is cooled to 0°C. Even this is not easy to imitate.

The Hoyo Strait where Sekisaba is caught is rich in plankton, which the Sekisaba feeds on, and the flow of the tide is fast. The reason Sekisaba meat firms well and is fatty year-round is thanks to the good environment of the sea it is raised in.

If you come across a Sekisaba that so much work has been put into, try it as sashimi, not Nigiri sushi. This is because Saba, which has a peculiarity to it, is unpopular among some people. However, Sekisaba doesn’t have this off-taste and doesn’t taste like Mackerel, so even people who don’t care for fish should be able to find it tasty.

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Revision date: August 21, 2023

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What is Shiromi?

Hirame is a high-quality fish that goes for at least US $50 per kilogram. It can even exceed US $80 per kilogram, depending on the timing and the fish’s body.

Hirame is a typical shiromi (white meat fish) when winter is approaching and a great sushi topping to start off a meal. Also, the taste is so delicate that the original flavor can be cancelled out just by adding too much soy sauce. How the chef expresses this delicate taste is a tribute to his skill and something that foodies look forward to.

In the US, Hirame is often written as “halibut” on the menu of sushi restaurants. Technically the English name of Hirame is Bastard halibut. Hailbut (referring to Pacific halibut) is called “Ohyo” in Japanese. In Japan, the engawa of massive Ohyo is often used as a substitute for Hirame engawa at conveyor belt sushi, but the two are not confused for each other. There is no mistake that Hirame is related to halibut, but they are completely different species. Incidentally, the price of Ohyo is US $3 to $20 per kilogram. It is incomparably cheaper than Hirame.

Also, depending on the restaurant it may be represented in a variety of other ways such as fluke, flatfish and flounder. These terms refer to relatives of Hirame (鮃) or Karei (鰈), but do not indicate any certain species of fish. In other words, there is generally no distinction between Hirame and Karei in the US and to go even further, all white fish are thought to be the same species.

The delicious taste of fish is dependent on the distribution of fat and the amount of inosinic acid. Therefore, fish taste better in the seasons when they have fattened up. On the other hand, people have a hard time distinguishing between types of fish when comparing the tastes of the parts with less fat. The free amino acids in fish meat differ only slightly between different types of fish. In other words, the flavor of all fish is mostly the same. It is only the amount of fat and the amount of the umami component, inosinic acid, that differ between fish, so apparently even sushi chefs cannot distinguish between fish just by eating the back part, which has a low fat content.

This is part of the reason why in the US all white fish is all lumped into the same category and to top it off, the common consensus there is that white fish has no flavor.

At sushi restaurants in Japan, generally there are at least two types of white fish on offer. It is practically guaranteed that Hirame will be in stock in winter. The light flavor unique to this white meat that spreads with each bite maximizes the aroma and sweetness of the vinegared rice. Recently, white fish with high levels of fat such as Kinmedai and Nodoguro, have become standard, high-quality white fish.

The difference between how even these sorts of white fish are handled in the US and Japan is astonishing. That said, flavorless Hirame is not consumed as sashimi or sushi even in Japan. It is served in dishes with strong flavors, like carpaccio. It’s possible that delicious Hirame is just not available in the US.

Related contents: List of White flesh fish

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Revision date: July 16, 2022

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What is Masuzushi?

The origin of Masuzushi dates back about 300 years. Apparently, in 1717 it was first presented as Ayu narezushi (narezushi is a traditional food, said to be the original form of sushi and made from lactic fermentation of fish) to the third-generation feudal lord, Toshioki Maeda, by Shinpachi Yoshimura, a feudal retainer of Toyama who excelled in cooking skills. Toshioki liked the dish very much and assigned the role of vinegaring Ayu to Shinpachi. After that, it is said that the same narezushi was presented to the eighth shogun of the Tokugawa shogunate, Yoshimune Tokugawa, and that Yoshimune was extremely pleased with it.

Shinpachi’s ayuzushi was made through the painstaking process of washing salt-preserved ayu with sake, then pickling it for around 12 days, removing the rice the day before it was to be served, then adding new rice that had been flavored with sake and salt.

This transformed to the present-day Masuzushi in the late Edo period, when the amount of vinegar was increased. Hayazushi, in which vinegar is added to rice for a quick meal, became popular, and Sakuramasu started to be used instead of Ayu, These factors seem to have contributed to how it transformed into the Masuzushi we see today.

It is made by first filleting fresh Sakuramasu into three pieces and removing the skin and bones, then cutting into 3 mm thick strips. These strips are sprinkled with salt and left for 3 to 5 hours before being washed with a vinegar mixture made of salt, sugar and other seasonings (water is never used for this). The type and amount of seasonings mixed with the vinegar at this time is a secret and determines the house flavor of the restaurant or family. Sakuramasu that has marinated for 1 to 2 hours in the vinegar mixture is placed on sushi rice in the container, then held down with weights to press for several hours to complete the Masuzushi.

Long ago, it was only made with Sakuramasu caught in Jinzu River, so it was made between April and July. However, due to reasons such as a dam being built upstream and water pollution, Sakuramasu produced outside the prefecture and imported Masu (trout) is used now, and it is made year-round.

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Revision date: August 3, 2021

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What is Funazushi?

Narezushi (mainly a preserved food in which fish undergoes lactic fermentation with salt and rice), in which Sushi finds its roots, can still be found even today throughout Japan. The most famous is Funazushi (鮒寿司, 鮒鮓, 鮒寿し) in Shiga prefecture.

Although it has “sushi” in the name, according to common knowledge of the day, it would be called crucian carp. The sweet and sour smell tickles your nose and it’s almost like pickled crucian carp. When you actually put it in your mouth it fills with an intense sourness and it can only be described as a really sour pickled food. However, the more you eat it, the more you somehow get used to it and in the end it becomes a favorite food that you will even crave. This effect is so mysterious that people even wonder, “Could this have been synchronized at some point with the tastes of our Japanese ancestors?”

Making Funazushi sushi is surprisingly simple. The only ingredients are crucian carp caught in Lake Biwa, rice and salt. First the internal organs are removed from the crucian carp, next it is salted and then it is shade-dried. This crucian carp is packed tightly into freshly steamed rice in a large cask. “Sushizume” refers to this precise situation, and the ingredients are packed in so there is no air inside. If air is let in, the oxygen will cause microbiota to grow. In other words, it will rot. This is the most important thing in making funazushi.

While this cask is left for eight months to two years, special microorganisms will cultivate even without oxygen. These are lactic bacteria and acetic bacteria, which work to change the entire contents into a sour flavor.

After that, the mushy rice is removed from the finished Funazushi, and only the crucian carp is consumed. However, let me reiterate, this sour flavor is intense and complicated. Comparing it to bleu cheese or camembert cheese might make it easier to understand. The taste is so intense that it makes some people sick.

Incidentally, there are records from when Hideyoshi Toyotomi advanced his army to the Korean peninsula (around 1592), that Funazushi from Oumi was presented to soldiers on the front line as a comfort food. This episode illustrates the fact that Funazushi was a dish of pride for the people of the town of Nagahama (where Toyotomi’s castle was located, now part of Shiga prefecture).

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Revision date: June 23, 2023

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What is Yamawasabi?

Horseradish is believed to have originated in Eastern Europe. It’s a cruciferous vegetable, alongside mustard, wasabi, cabbage, and broccoli. Horseradish is very fertile, and buds and roots will sprout just by cutting the root stock part to an appropriate size and soaking it in water. Once transferred to soil the roots will multiply quickly even without any other efforts.

In Europe horseradish is used as an ingredient for sauces or to accompany sausage and roast beef, or as a subtle seasoning for other dishes. In Japan most is used as an ingredient in processed foods such as wasabi powder or wasabi paste. Unlike wasabi, horseradish is characterized by its pure white root and strong spicy flavor. In Hokkaido horseradish is called “Yamawasabi” and is a common sight at home dinner tables.

Farming of Yamawasabi for food started in the Meiji era and settled in Hokkaido. Currently over 90% of the domestic production in Japan is accounted for in Hokkaido. While it is grown throughout Hokkaido, the vast Yamawasabi fields befitting Hokkaido are especially prevalent in Abashiri and Kitami.

In Hokkaido, Yamawasabi is eaten as an accompaniment to white rice. Grated Yamawasabi is sprinkled on rice and there are also jars of “Soy sauce-marinated Yamawasabi” sold as a normal item at supermarkets. Besides on rice, it is also indispensable to Hokkaido cuisine as seasoning for hiyayakko (cold tofu) and sashimi.

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Revision date: June 28, 2021

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What is Rendaku?

In Japanese, when a compound word is made out of two individual words, and the first consonant of the second word changes from a “clear sound” to a “fuzzy sound”, it is called “Rendaku”. For example, Edomae (江戸前) + sushi (寿司) changes to Edomaezushi (江戸前寿司). However, the correct pronunciation is only generalized among Japanese people, so in this book we chose the most commonly searched version of each compound word.

Examples of Rendaku (連濁):

Nigiri (握り) + sushi (寿司)→Nigirizushi (握り寿司)

Inari (稲荷) + sushi (寿司)→Inarizushi (稲荷寿司)

Masu (鱒) + sushi (寿司)→Masuzushi (鱒寿司)

Kaiten (回転) + sushi (寿司)→Kaitenzushi (回転寿司)

Kuro (黒) + tai (鯛)→Kurodai (黒鯛)

Ma (真) + tako (蛸)→Madako (真蛸)

Aka (赤) + kai (貝)→Akagai (赤貝)

Tori (鳥) + kai (貝)→Torigai (鳥貝)

Shiromi (白身) + sakana (魚)→Shiromizakana (白身魚)

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Revision date: June 9, 2021

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What is Karami?

Sashimi essentials such as wasabi, ginger, karami-daikon, etc., are collectively called “Karami”. The term Karami comes from the Japanese word 辛味, which literally means “spicy” or “pungent taste.” In the context of sashimi, it refers not to intense heat like chili peppers, but to a sharp, aromatic pungency that stimulates the palate, cuts through richness, and neutralizes fishy odors. This quality is why karami ingredients—such as wasabi, ginger, or grated daikon—are used alongside raw fish: they enhance flavor while making the dish feel cleaner and more refreshing.

Originally Karami was a type of Tsuma. From the mid to late Edo period, Karashi (mustard) was mainly used for karami in sashimi. Eventually, due to the influence of Edomae sushi, wasabi became the norm. Wasabi was favored not only for its refreshing heat but also for its antibacterial properties and its ability to complement the delicate flavors of raw fish. For sashimi such as bonito and sardines, wasabi isn’t enough to offset the peculiar aroma. In some cases, it is better to use ginger, which works on the root components of the odor. These types of fish have the best flavor once spring has passed, and interestingly enough, wasabi is least prevalent in summertime, while ginger is in peak season. Mother nature seems to know what she’s doing.

Historically, karami was considered a type of tsuma, but today it is classified as a type of yakumi (condiment). Tsuma refers to the decorative and edible garnishes that accompany sashimi, serving both aesthetic and functional purposes—enhancing presentation, adding contrasting textures, and refreshing the palate between bites. Over time, karami came to be recognized not just as a garnish but as a form of yakumi (condiment), whose primary role is to add flavor, mask unwanted odors, and balance the taste of the fish rather than to decorate the plate.

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Revision date: August 12, 2025

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What is the trick to super cheap Ikura at conveyor belt sushi restaurants?

Immature salmon eggs still wrapped in ovarian membrane and salted are called sujiko. Ikura is salmon roe in which each mature egg is separated from the ovarian membrane before laying the eggs and then salted or marinated in soy sauce. The ikura of Chum salmon going upstream in the Kushiro River and Tokachi River in Hokkaido From October to December are considered to be premium ikura.

For cheap ikura, roe broken up inside the ovarian membrane in a fish that is approaching spawning time called “barako” is used. When the ovarian membrane of barako is torn, the eggs will fall out and scatter, so while they don’t take much work to prepare for serving, they also don’t taste particularly good. Even cats turn up their noses at barako, so they are also called “neko-matagi”, which literally means “the cat walks over it” and is used to refer to unpalatable fish. However, each egg is large and they look very appealing, so they are used at higher-end conveyor belt sushi. Unlike the 100-yen (US $1) restaurants, these higher-end restaurants don’t use disguised fish or substitute fish. This is because their basic business strategy is to differentiate themselves by attracting customers with authentic toppings. Generally they market the high quality of their toppings, but the ikura is actually this cheap “neko-matagi”.

Beneath this strategy of attracting customers with authentic toppings is this “Deceptive business strategy”. Salmon also swims upstream in the rivers of Tohoku and Hokuriku. However, the taste of ikura tastes inferior to that in Hokkaido. This ikura is also served at the higher end restaurants. That’s because although it doesn’t taste as good, it’s orthodox ikura. In case of orthodox ikura, the roe is used within one hour of the catch. But, if time passes and the freshness drops, the eggs will dry out and the surfaces will dimple, wrinkling. This is the type of ikura that is cheaper and often served at the cheap conveyor belt sushi restaurants.

The most commonly used roe in conveyor belt sushi restaurants is ikura from cheap Alaskan or Russian Chum salmon. An even cheaper type is masuko. Besides the masu roe, raw materials included soy sauce, salt, fermented seasoning, amino acids, reduced sugar syrup, enzymes, fish sauce, and fish and shellfish extract. For homemade versions, only soy sauce, mirin (sweet cooking sake) and sake are used.

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What is Salmon caviar?

In Japan, salmon roe that has been separated from the ovarian membrane and then salted is called ikura. At sushi restaurants, this is also marinated in broth that includes soy sauce, mirin and sake. This is called ikura marinated in soy sauce, or simply ikura. Worldwide, caviar is considered to be of more value than ikura. Therefore, in an attempt to improve the impression of soy sauce-marinated ikura, it is sometimes called ‘salmon caviar’. This is behavior especially seen among manufacturers selling soy sauce-marinated ikura.

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Revision date: March 9, 2021

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What is Red caviar?

Not to belabor the point, but the following is dependent on the following. In Japanese salmon is referred to as “鮭” (sake/salmon) or “鱒” (masu/trout). The characters look different, but they are part of the same family and there aren’t clear biological categories to separate them into. Incidentally, in English the type that makes their way into the sea are called “salmon,” and those that remain in freshwater their entire lives are known as, “trout.” They are all considered to be part of the salmon family. Now, foreigners who know about Japan may imagine Japanese sake (the alcoholic beverage) when they hear the word “sake” so we spell sake/salmon as “shake”, which is close to the sound pronounced by Japanese people.

First of all, shake is mainly Chum salmon, caught in the seas near Japan. Masu caught in the seas near Japan are mostly Pink salmon (Humpback salmon) and Sakura masu. Masu caught in rivers and lakes are generally Char or Rainbow trout.

Now we finally get to the topic of this article, shake roe that has been removed from the ovarian membrane then salted or marinated in soy sauce is called ikura while masu roe is called masuko and they are clearly distinguished. This is because masuko can be bought at just 20-40% of the cost of ikura. However, the difference is really that each egg is smaller than that of ikura and in general people can’t taste a difference.

Over the past 10 years or so, the masuko made from the roe of Rainbow trout farmed in France and the masu farmed in Japan have been called ‘red caviar’ by manufacturers. Of course black caviar made from the roe of sturgeon and tobiko made from the roe of flying fish are distinctive. Certainly there is no problem in calling fish roe caviar according to the Product Labeling laws, but it’s extremely clear that they are only trying to get a higher price out of it.

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Revision date: March 9, 2021

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What is ken?

Ken (剣) is a traditional Japanese garnish made from finely shredded vegetables like daikon radish. It is often seen alongside sashimi. While commonly mistaken for tsuma, ken has its own distinct role in Japanese plating and presentation.

It is not merely decorative—it helps absorb moisture, maintains freshness, and enhances the visual balance of the dish.

Ken is considered to be better the longer and thinner it is, but this is a mistake. Not only is Ken tangled and difficult to eat, but it also doesn’t give any sense of the flavor of the materials. It’s long been said that 10 cm is a reasonable length and this is also the length that looks the most refined. Creating ken requires precise knife skills, and its neatness often reflects the chef’s craftsmanship.

Many people believe that the thinly cut daikon radish strips that accompany sushi are tsuma. That is not tsuma. It’s called ken. Besides daikon radish, udo, pumpkin, cucumber, carrots and turnips are also used. It is cut into thin strands and stood up next to sashimi like a sword (which is called “ken” in Japanese). However, when the sashimi is laid on top of it, it is called shikitsuma. While it is a bit confusing, in that case it is a type of tsuma. The simplicity and elegance of ken align with the Japanese aesthetic of minimalism and natural beauty.

Since the Meiji era, combos of many different types of sushi have become popular, and with it larger dishes have become necessary. Therefore, there has also been a tendency to make it more showy. It’s only natural that the types of tsuma increase to place focus on the highly valued seafood, but if there is too much ken, it will take over the space meant for the sashimi.

What is the difference between denbu and oboro?

Oboro and Denbu are traditional Japanese ingredients often used in sushi and other dishes, known for their delicate texture and sweet flavor. While they may look similar and share many ingredients, understanding their subtle differences and uses can enrich your appreciation of Japanese cuisine.

Oboro and Denbu look the same, and the ingredients are also pretty much the same. In other words, there are no clear differences between them, but what it is called differs depending on the restaurant’s policy and the locality. There are various theories for this, but there is no clear line distinguishing oboro and denbu.

Denbu (田麩) is mainly boiled white fish that is then loosened and made into fibers, then seasoned with sugar, mirin, salt, etc., then roasted until the moisture is gone. The most commonly used fish for denbu are Tara (Cod) and Tai (Red seabream), which have a mild flavor and light color suitable for this preparation. Some are colored with red food coloring (called sakura denbu) while others are left as the brown color similar to tsukudani. The appearance is as if only the fibers of the original ingredients remain. This is why it was written with the kanji “田夫” (the literal meaning of kanji: rice patty+husband). The word “田夫” means “someone from the countryside” or “rough-cut” and refers to the way the fish is turned into a coarse form by pulling the meat apart. It is also used as a coloring for chirashizushi, futomaki (large sushi rolls), bento boxes, etc. Because of its bright color and sweet flavor, denbu is often used to add visual and taste appeal to children’s meals and festive dishes in Japan.

On the other hand, Oboro (朧) is made by using a grinding bowl to break down the meat of shiba shrimp or white fish, then seasoning with sugar, mirin and salt before removing the moisture over low heat. Oboro is used for bara-chirashi, futomaki (large sushi rolls), etc., and is also sometimes used between the topping and shari (vinegared rice) in nigiri sushi. This practice enhances the subtle flavor of the fish, serving as a base layer of umami, while helping the sushi topping blend more harmoniously with the vinegared rice. Oboro acts as a kind of “glue” between the neta (sushi topping) and the shari (vinegared rice), and it also adds a soft visual accent to the overall presentation. This gentle sweetness and the shrimp aroma are essential for Edomae-style sushi. Making oboro is laborious work, so there are fewer and fewer Edomae-style sushi restaurants that make their own oboro.

Although the distinction between Oboro and Denbu can be subtle and varies by region and restaurant, both play an important role in enhancing the flavor, texture, and appearance of Japanese dishes. Next time you enjoy sushi or chirashizushi, paying attention to these ingredients can deepen your culinary experience.

We hope this information will be helpful.

Revision date: August 5, 2025

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What is Fugu poison?

Why do people risk their lives to eat Fugu, a fish known to be deadly?

Fugu, or blowfish, is a celebrated delicacy in Japanese cuisine, but it comes with a deadly risk. Despite its exquisite taste and refined culinary presentation, Fugu contains one of the most powerful natural toxins known to humans. Understanding what makes this fish so dangerous—and how it’s safely prepared—sheds light on one of the most fascinating aspects of Japanese food culture.

In most cases, Fugu (blowfish) poison is found in non-meat parts of the fish such as the liver, ovaries, stomach, intestine, skin and eyes. There are Fugu that do not contain poison in these parts, but most of the Fugu in the waters near Japan are poisonous. A mistake in preparations that allows the meat to touch the poison of the liver or ovaries results in immediate death. Therefore, the general rule is to only eat Fugu at restaurants with an expert licensed in Fugu preparation. Cases of poisoning by Fugu are nearly always a result of an amateur trying to prepare the fish.

The toxin in Fugu is a chemical substance called tetrodotoxin and even heat from boiling or frying can’t detoxicate it. Even Torafugu (Japanese pufferfish) that we find so delicious (we eat the meat, skin and testes) has poison in the liver, ovaries and intestines. The toxicity is said to be at least 1,000 times that of potassium cyanide. They say 10 people would die from the organs of a single Torafugu. In the case of Fugu poisoning, the first poisoning symptoms occur between 20 minutes and three hours after eating the Fugu. It starts with numbness in the lips, the tip of the tongue and fingertips. This is followed by headache, stomachache and severe vomiting. The victim will stagger when trying to walk. Soon they will experience sensory paralysis, speech disturbance and difficulty breathing, accompanied by a decrease in blood pressure. After that, the entire body becomes paralyzed and the victim can no longer move even a finger. Finally, they will fade out of consciousness and eventually both breathing and heartbeat cease, resulting in death. If the consumer doesn’t notice they are experiencing poisoning symptoms, they will surely die.

The strength of the toxin of the fugu also varies depending on the season. Even on an individual basis, some fish have toxins while others don’t. It’s not possible to determine this based on appearance, so it’s better to never eat the organs and eyes, which have a high probability of containing poison.

Fugu has already been successfully farmed and is on the market. No toxins have been found in this farmed Fugu. If farmed Fugu has no toxins, it’s only natural to question what factors generate toxins in wild Fugu and apparently it‘s a cumulative effect of toxins from the food chain. Fugu’s main sources of nutrition are starfish and shellfish. Starfish and shellfish accumulate poison in the body by eating zooplankton with vibrio attached to them. This vibrio creates poisons. Then, Fugu accumulates toxins in the body by eating starfish and shellfish that have toxins accumulated in their bodies. Therefore, farmed Fugu are raised on man-made feed that doesn’t contain Fugu toxins, and since they don’t ingest Fugu toxins and there is no bioconcentration, so the Fugu does not contain poison.

Enjoying Fugu safely requires more than bravery—it requires expertise.
While the thought of eating a potentially lethal fish may seem reckless, the strict regulations and skilled craftsmanship behind Fugu preparation make it one of the safest delicacies when handled properly. As farmed Fugu becomes more common and toxin-free, the dangers may be diminishing—but the mystique surrounding this unique fish remains as strong as ever.

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We hope this information will be helpful.

Revision date: August 7, 2025

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