What are Konacha and Mecha?

a photo of green tea

When it comes to green tea, I’m sure you’ve heard of Gyokuro (玉露) and Matcha (抹茶), but you are likely not familiar with Konacha (粉茶) and Mecha (芽茶). Let’s remedy that by explaining both Konacha and Mecha here.

First and foremost, the three broad tea categories based on the processing method of the young leaves include green tea, oolong tea and black tea, but these are all made of leaves picked from the same trees, and then end up as completely different teas just by changing the processing method. Oolong tea and black tea are made by artificially fermenting the tea leaves as part of the processing. On the other hand, green tea is made without fermentation. The raw material of green tea that is eventually made into Sencha, Gyokuro and Tencha (碾茶), which is the raw material for Matcha among others. Then Konacha, Mecha, etc. are byproducts of the process for making Sencha and Gyokuro.

First of all, Sencha is the foundation of Japanese tea.

Sencha is known for its gentle flavor with a lingering, but subtle sweetness amidst the inherent fresh scent and bitterness. Generally, the color of Sencha is a transparent yellowish gold. Freshly picked tea leaves are immediately steamed, stopping the fermentation process. The steaming process gives each completed, individual tea leaf a deep green color. Tea was originally introduced to the world from China, but Sencha is the only tea with a unique, deep flavor created by Japan. About 80% of the tea produced in Japan is said to be Sencha. The most delicious Sencha comes around from the end of April to May, which is the beginning of the tea season. The appropriate volume of tea when steeping for one person is 2 to 3 grams of tea leaves to 70 milliliters of hot water and the appropriate water temperature is around 70℃ in order to bring out the sweetness and umami.

Next, we’ll describe Gyokuro.

a photo of matcha tea

By blocking sunlight and growing in the shade during the sprout timing, the leaves for Gyokuro grow full of theanine, which is an umami component, ending up with tea leaves that have a unique sweetness. It is common to focus only on taste, but the fragrance, described as “enveloping” is also wonderful and should not be discounted. This fragrance is often described by people from outside of Japan as a having a seawater-like scent or being salty. Yame in Fukuoka, Uji in Kyoto and Okabe in Shizuoka prefecture are the three famous production spots for Gyokuro. The appropriate volume of tea when steeping for one person is 2 to 3 grams of tea leaves to 20 to 30 milliliters of hot water and the appropriate water temperature is around 50 to 60℃ in order to bring out the sweetness and umami. This will give you the ultimate cuppa that is the epitome of luxury.

Most of the Agari (cup of tea to finish the meal) served at sushi restaurants is Konacha.

a photo of konacha

By avoiding the use of a teapot and only preparing the number of teacups needed, directly in the cup, strong tea can be made just by adding the hot water later. Conventionally, steaming is a very important step in making tea, but it isn’t necessary with Konacha. Konacha raw ingredients are mainly made up of the broken tea leaves from the Gyokuro and Sencha manufacturing process.

Brewing konacha results in a dark, deep green color. As the name suggests, it has a lot of powder in it, so the tea leaves in powder form settle in the bottom of the teacup. There for it also carries the benefit of being richer in nutrients than other teas. The sense of transparency is moderate and has a bit of a more somber color. The appropriate amount of water when brewing konacha is one gram of tea leaves to 40 to 60 milliliters of hot water. Konacha is strong, so making it with water that is about 80℃ gives it a mellow flavor. Tea that is made quickly with hotter water gets a moderate bitterness typical of Japanese tea and cleanses the palate.

Also, Japanese people have treasured food since long ago. For example, the leaves of vegetables like daikon radish are sauteed and consumed rather than discarded. As a society they have spent many centuries making efforts to figure out how each part can be made delicious. Mecha is made by collecting the cut-off tips of sprouts and leaves in the process of manufacturing Gyokuro and Sencha. There are many people who think Mecha is tea made just from picking the small buds from tea trees, so don’t make that mistake.

a photo of tea

Mecha is a strong green tea that gets a strong scent when brewed. The longer the extraction time is, the stronger the tea, so if the color is too dark it changes the impression it gives and also affects the flavor. That’s why it’s important to pay close attention to extraction time. In general, the volume should be 2 grams for 70 milliliters of hot water–the same as Sencha. When preparing for more people, fewer tea leaves should be used. When brewing, wait patiently for the rounded Mecha leaves to open up. Around 80℃ is the appropriate temperature, but if less bitterness is preferred then it can be made with hot water at 90℃.

In summary, Konacha and Mecha, which are teas used at sushi restaurants, are made from the broken-off parts of the tea leaves carefully selected for Sencha and Gyokuro. They don’t require the steaming step of the tea-making process, so they can be prepared quickly and include the appropriate amount of bitterness for cleansing the palette, making them perfect pairings for nigiri sushi.


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Revision date: September 8, 2022

 

What is Ikekoshi?

A photo of fish rioting

When a fish is pulled from the sea, it is put into an extraneous environment with sunlight, temperature and hot human hands that it isn’t used to, so it starts to swim violently with all its might, trying to get away, in a perpetual state of tension. If cooked in this state, blood will still be running through all the cells of the body. There is no sense of transparency in the meat at this point, especially the white meat. The body also hardens. The entire body reeks of blood. In other words, the meat of white fish is full of blood, making it unsuitable for preparing as food.

Fish are placed in a tank with enough water and oxygen, only in numbers so that they do not rub up against each other. A lid is placed on the tank to create a temporary dark space. At this time, the temperature of the water is an ideal, low temperature. This keeps the fish from struggling. After being left for half a day, it will regurgitate anything undigested that was eaten prior to being caught, become acclimated to the dark space and settle down. The bloody tone from struggling fades throughout the body and the fish relaxes.

Creating this state is called “Ikekoshi”.

Ikekoshi methods differ depending on the species of fish, but the idea is to keep this state for only one day at most. When left for two or three days, the fish loses meat, starts to swim around the dark chamber that it has now grown accustomed to, and its body, tail and fins rub up against other fish or the sides of the tank, causing damage. This hurts the meat quality and appearance so it is something the fisherman must look out for.


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Revision date: August 5, 2022

Do you know why canned crab is wrapped in paper inside the can?

a photo of crab canning

Crab protein has a high sulfur content. This sulfur can bind with the iron in the can, resulting in ferric sulfide that causes black spots in the meat. Black discoloration of the crab meat significantly mars the appearance and reduces the product value. In order to prevent this, parchment paper with superior water resistance and oil resistance is used to keep the crab meat from coming in contact with the can.

Meanwhile, the trace amounts of magnesium, ammonium and phosphoric acid contained in crab and fish meat sometimes bind to create magnesium ammonium phosphate glassy crystals. This chemical phenomenon is called struvite.

These crystals have no taste or odor and dissolve easily in the stomach so they are not considered to be an issue under the Food Sanitation Act. However, large crystals may hurt the oral cavity so efforts are made to improve production methods to prevent generation of crystals and keep any crystals that do form as small as possible. However, parchment paper does not reduce the struvite phenomenon.

In summary, do you now understand the truth of why crab meat is wrapped in white paper? Of course, nowadays the surfaces of cans are processed in a way that the iron doesn’t start to dissolve, so perhaps the correct theory is that the parchment continues to be used to give a sense of luxury.


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Revision date: August 1 2022

What makes good quality Kuromaguro?

A photo of KuromaguroThere are three elements that make good quality Kuromaguro(Bluefin tuna).

They are decidedly, color, fragrance and texture.

A photo of bluefin tunaFirst of all, color does not simply refer to the color of the cross-section when the fish is cut with a butcher knife.

It refers to how long the fish maintains its “characteristic coloring”. After all, tuna darkens as time passes, eventually turning a burnt-brown color. The true, visual charm of Kuromaguro is the eye-awakening red color that catches your attention when the sushi is placed on a counter or plate. This wonderful coloring is a characteristic of tuna caught through longline fishing or single‐hook fishing. On the other hand, it is said that those caught in round haul nets don’t hold their color and don’t last long. When frozen tuna is thawed, it turns brown within a day. This focus on color is based more on Japanese restaurants that serve sashimi at tables that are located farther away from where the food is being prepared, than on sushi. Incidentally, Mebachi, despite also being tuna, holds its color longer than Kuromaguro does and is suitable for take-out sushi. Minamimaguro is a darker red color than Kuromaguro, but it also loses its color quicker. Kihada maintains its color best.

Next, where does Kuromaguro’s appealing fragrance come from?

The truth is that the source of fish flavor components is still being researched and there are a lot of unknowns. What we do know is that this fragrance is made up of many volatile compounds, but since there are only trace amounts of each one, they are difficult to analyze.

Yet, in the case of expensive Kuromaguro, every measure possible is taken to make sure this fragrance is maintained. Kuromaguro is a migratory fish that gets around by swimming at high speeds in the surface layer of the sea. It needs strong muscles to swim this fast. it also needs to circulate blood throughout its entire body in order to vigorously move those muscles. When a tuna violently struggles to resist and twists its body to avoid being caught, the proteins in its muscles (myosin and myoglobin) rapidly react with oxygen and start to degenerate. This causes Yake and the oxidized odor of tuna. It is important to catch the tuna while causing it as little stress as possible, quickly remove the organs and then use ice to rapidly cool the entire body. If this process is delayed then the pleasant fragrance will transform into an odor. In other words, the scent of Kuromaguro all depends on how it is processed after being caught.

The meat of Kuromaguro that is properly processed emits a unique aroma with a slightly acidic taste when you put it in your mouth. That fragrance lingers for a long time and it combines beautifully with the acetic acid of the sushi rice to go straight to your nose. Then, the moment the fish has disappeared down your throat, the scent of the iron and a subtle acidic taste linger very nicely. This experience is only possible with the exceptional Kuromaguro.

As for the texture, this is determined by the fat distribution of the tuna.

Especially in winter, the Harakami cross-section of Kuromaguro is marbled, much like the Ribulose of Wagyu beef. The melting point for the fat of high-quality tuna is low, and it starts to dissolve even at human skin temperature. This is why sushi chefs who are particular about the sense of unity between shari (sushi rice) and tuna, say, “Shari should be skin temperature.”

There are many chefs who say that the umami of Kuromaguro is in the fat. In the first place, Kuromaguro is one of the fattier fish, and especially between autumn and winter, the Kuromaguro that fed on Surumeika and Sanma has exceptional Harakami. The organs of both Surumeika and Sanma are rich, full-bodied and delicious, even when grilled and eaten by humans. In other words, it is the Surumeika and Sanma that the tuna feeds on that determine the quality of meat. As an example of the meat quality of tuna being affected by what that tuna fed on, Kuromaguro in the Atlantic ocean that has fed on Nishin may exhibit the scent of Nishin when made into sashimi.

However, having a high fat content is not the most important factor. For example, farmed Kuromaguro is fed a high-protein diet so that it will be fatty regardless of the season. Yet, the fat is tougher than that of the wild fish and it’s not something that leaves you wanting a lot more. In comparison, the fat of wild Kuromaguro has a fine texture throughout, immediately melts in your mouth and is digested easily. As sushi chefs know, the fresh fish seems to suction to their hands when making the nigiri sushi. In the same way, it has a smoothness that seems to suction to your tongue when you put it in your mouth. Once you’ve swallowed, it leaves you craving more.

This is the depth of wild Kuromaguro.


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Revision date: July 2 2022

What is Odori?

a photo of odori ebi

Both conveyor belt sushi and premium sushi have versions of sushi made with raw sweet shrimp or botan shrimp. However, in Edomae Sushi, boiled shrimp is always used. The use of raw shrimp in sushi started in the Kansai region. Moreover, in the Kansai region, there are many restaurants that make sushi with live Kurumaebi known as “Odori or Kassha”. However, this way of eating may be declining nationwide. It is probably because there is increased texture when boiled, so it tastes better.

Going back to Odori, “Odori” means “dance” in Japanese and it is said that this name came from the fact that shrimp twitches on the sushi rice and looks like it is dancing. If you look up the roots, it seems that this method of serving started at a sushi restaurant in Kyoto City in the early Showa period. It spread throughout the Kansai region, but although Odori may look easy to make, the method is actually quite elaborate.

Let’s introduce the common recipe here. First wash the live Kurumaebi with fresh water and start by bending the head with your hand while detaching it from the body, then peel off the shell. Next, peel the skin off the abdomen and cut the abdomen open vertically. Fresh shrimp is difficult to peel, so it is important to do it very carefully. Next remove the veins from the back and sprinkle on just a bit of mirin and vinegar, then lightly rinse off with ice water. After that, parboil just the tail in boiling, salted water to make it look attractive.

Then make the sushi with the open side facing up. The direction is important because it is easier to tell that the shrimp is dancing when it is arranged this way. To finish, sprinkle lemon juice over the shrimp meat. This stimulates movement of the body.

Now let’s discuss how a customer eats Odori. It goes without saying that since the shrimp is still alive, the moment you dip the topping in the soy sauce, the shrimp twitches in its death throes, convulsing violently. Apparently the customers are greatly pleased to see this. We don’t recommend the faint of heart to order this dish.

Incidentally, eating only the shrimp in this way is called “Odorigui”. In China there is a dish in which living shrimp is soaked in Shaoxing rice wine or fermented alcohol, made drunk, and then eaten once it has settled down. These sorts of methods may be considered cruel in some western countries.


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Revision date: June 6, 2022

What is Ciguatera fish poisoning?

a photo of Star snapper

Ciguatera fish poisoning is a type of food poisoning caused by consuming certain fish that live in tropical and subtropical coral reef areas such as Moray eel, Grouper, Star snapper, Japanese scavenger and Parrot fish.

It is caused by toxins such as ciguatoxin, but it mainly generates from dinophyceae that are stuck to algae. The process of ciguatera occurring involves the food chain. Even if a fish itself doesn’t originally contain toxins, an herbivorous fish may eat algae that turns it toxic. That fish may be eaten by a carnivorous fish, which then accumulates high concentrations of ciguatera in its body. When a human consumes the carnivorous fish it can cause food poisoning in the human. There are as many as 300 species of fish that contain ciguatoxin. The ciguatoxin, which causes the food poisoning, cannot be killed by boiling or grilling, so it can’t be prevented through food preparation.

Symptoms of this food poisoning mainly consist of sensory nerve abnormalities, muscle soreness, itchiness and abdominal pain, but it is rarely fatal. However, it takes quite a long time to recover from compared to other toxins and the average recovery time is said to be two to three weeks. It is vital to diagnose ciguatera fish poisoning as soon as possible. Most symptoms develop within one or two hours and up to to 24 hours after consumption and one unique symptom is dysthermesthesia. This is a form of dysesthesia in which touching cold things feels like its burning. It occurs one to two days after the poisoning and is a known characteristic of ciguatera fish poisoning. Another characteristic symptom of ciguaterafish fish poisoning is joint pain within 24 hours after consuming the fish. In any case, it is important to be seen by a specialist as soon as possible.

Incidentally, the name ciguatera came from Spanish immigrants to Cuba as a name for food poisoning caused by the cigua shellfish in that region. Later it was also used to describe fish poisoning, which causes similar symptoms.


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Revision date: May 9, 2022

The answer to the question, “Can I eat sushi leftovers the next day?”

a photo of Takeaway sushi

Nigiri sushi is generally made with raw seafood. It can be said that the seafood starts to go bad as soon as it is put on warm rice. Of course, at the stage of preparation, there are procedures being taken to reduce the causative micro-organisms of food poisoning. Out of all food that is commonly eaten raw, sushi is considered to have the least micro-organisms that cause food poisoning.

For example, Vibrio parahaemolyticus, a typically known bacteria that causes food poisoning, attaches to seafood, and if the conditions, such as temperature, are just right, it proliferates at double the speed of other food poisoning bacteria. When you are eating at a sushi restaurant, bacteria growth is being suppressed. However, if you take sushi home to eat it, depending on conditions bacteria could proliferate.

This is why as a basic rule, you cannot take sushi home from a sushi restaurant.

So then, what is the difference between sushi sold at the grocery store and prepared at sushi restaurants?

There are obvious differences between sushi made by sushi chefs and take-out sushi, as explained below.

Take-out sushi is lined up at the store, selected by the customer, then eaten at home, which takes time. Therefore, a higher amount of salt seasoning is used compared to Nigiri sushi restaurants, in order to delay the degradation in quality. Sushi made by sushi chefs at restaurants has a salt content of about 1% in the sushi rice, while that of take-out sushi has about a 2% content.

Next, with a pH of around 4.5%, it is difficult for bacteria such as Salmonella, Staphylococcus aureus, E. coli bacterium bacteria and Vibrio parahaemolyticus to proliferate, and there are experimental results that show they die out. In an experiment that measured the pH of sushi rice in take-out sushi, it was usually measured at 6%. Nigiri sushi made at a restaurant is often around 6.2%, so this acidity is put to good use in the sushi rice and could be delaying degradation.

Furthermore, although it may not be a pleasant topic of discussion, preventing spoiling and deterioration in food caused by micro-organism is done by adding preservatives to improve the shelf life. For example, classic preservatives such as benzoic acid, Sorbic acid and PH adjusters are used all over the world. There is an obligation to list these on the product label when used.

Now let’s get into the main topic.

This all being said, sometimes when you buy take-out, there are leftovers. There is no question that it is better to promptly discard them. But you may think that you can just eat it the next day, right?

You can. And it will taste the same as when you bought it.

First of all, there is something important to remember; not all toppings are equal in take-out. Unfortunately, things that require freshness like shellfish, squid, mackerel and sardines, cannot be saved. These must be consumed on the day they are bought.

Next, let’s go over how to eat your day-after sushi so that it still tastes good.

The toppings this method works for are tuna, salmon, white fish and steamed shrimp. However, the only white fish it works for are benthic fish such as flounder. As long as the meat is still transparent the next day, it’s safe. For Hamachi, which always has more than 20% body fat, which oxidizes, so avoid keeping it to the next day. Raw shrimp is out too. Steamed shrimp becomes more delicious when quickly put into sushi vinegar for storage.

The method is simple!

First, remove the Nigiri sushi topping from the rice. Next, wash that topping with running water for a few seconds and then dry well with a paper towel. Make sure you are quick in all of these steps. Finally, wrap in plastic wrap and store in the refrigerator.

Next, use a wet paper towel to wrap the sushi rice. Wrap this set in plastic and put it in the vegetable drawer if possible. If you don’t have a vegetable drawer than the normal refrigerator compartment is fine.

The next day, when you are ready to eat, heat the sushi rice in the microwave at 1000W for 10 seconds. The point is just to warm it up a little. Next, just take the topping from the refrigerator and place it on the rice. You can add some wasabi if necessary.

Incidentally, if you use this method for take-out sushi, even when consuming it on the same day, it will taste even better than just eating it right away.

The practice of sushi chefs is to put somewhat cold sushi toppings (16~19℃) or room-temperature toppings (20~23℃) on top of sushi rice that is the same temperature of the human body (37℃). We are trying to imitate this method. If you are consuming on the same day, any topping can be removed from the rice and prepared like this.

But please do not wait any longer than the next day to eat any leftovers.

Do not bend this rule. Let me warn you that the symptoms of food poisoning from shellfish and silver-backed fish are horrible. It should also go without saying that if the sushi rice has already dried out, there is no bringing it back, even with this method. Once you’ve reached that point, you just have to throw it away. Naturally, you cannot eat smelly sushi toppings.


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Revision date: April 1, 2022

What is Yake or Yake-maguro?

An illustration of Longline fishingTuna fishing methods include Purse seine fishing, Fixed-net fishing, Drift-net fishing and Longline fishing, among others. Ocean fishing for tuna in the South Pacific Ocean, Indian Ocean and Atlantic Ocean, is often done by longline fishing. A main line can exceed 150 km in length and have over 3,000 hooks hanging from it. A main line is let out for 6 to 7 hours, and it takes 3 to 4 hours from running the line in the sea, to catching tuna. After that it takes another 10 to 15 hours to reel it up, so the tuna that was caught early may have already died during this time. There are times when sea water may feel warm to the touch, even in the dead of winter. The problem here is, that the body of the tuna that died early, will be warmer if the sea water is warmer. The body temperature will also be unusually high if a tuna caught by a hook ends up struggles for a long time and dying before being reeled in. The same is true for Kuromaguro caught in game fishing.

When this tuna is cut into pieces, the meat is whitish, as if grilled in a fire, so it is called “Yake (焼け)” or “Yake-maguro (焼け鮪)” as “Yake” means “burnt” in this case. The meat can also be a grayish-brown. In the industry it’s known as “White tuna” due to its color. It loses its characteristic red color, the texture of the meat when eating it is flakey and it doesn’t taste good.

Even if the fish body is cooled with ice water after catching, once the meat has been “burnt”, it won’t turn back to red. This renders even the premium Pacific bluefin tuna and southern bluefin tuna worthless, with zero commercial value as food. However, the fishermen don’t just toss the dead fish back into the sea without a second thought. This is mostly processed into pet food. Also, since it can’t be determined externally whether the meat is “burnt” or not, no one can tell until the fish has been cut open. It runs a big risk to the broker and can be a cause of its fishing port brand losing credibility.

It is currently believed that burnt tuna occurs from high temperature and low pH in the muscles of the fish after death, and that there is a complicated, indirect causal relationship between the conditions such as the environmental temperature, fishing method, handling of the catch, length of processing time, type of fish and size of fish. However, the mechanism that causes this phenomenon is not clearly understood.


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Revision date: March 1, 2022

What is used as a substitute for the expensive Mongou ika?

an image of mongou ikaNo people in the world love squid more than the Japanese. Squid ranks third in import volume behind shrimp and tuna. Squid is brought to Japan from the oceans all over the world. There are between 400 and 500 species of wild squid on Earth. Some, like the pygmy cuttlefish, are tinier than 3 millimeters while the giant squid is over 10 meters.

There are about 100 species of squid that live in the waters surrounding Japan. Surume ika (Japanese common squid) makes up the highest volume of domestic-caught squid. It is used as a Yari ika or Surume ika topping in eastern Japan, but Surume ika isn’t used very often in western Japan. At sushi restaurants, squid like Sumi ika (Golden cuttlefish), Aori ika (Bigfin reef squid), Kensaki ika (Swordtip squid) and Mongou ika (Ocellated cuttlefish) go for high prices, but they are all caught in smaller quantities and therefore only available to high-end sushi restaurants that can procure them fresh.

There are some conveyor belt sushi restaurants that list Mongou ika (モンゴウイカ又はカミナリイカ) on the menu, but actually serve European common cuttlefish (ヨーロッパコウイカ). It is produced in the waters off the coast of West Africa. Even some sushi restaurants do this. This is actually still too pricey for conveyor belt sushi though. What is generally used at conveyor belt sushi is Flying squid (アカイカ), which goes for only 1/10 the price of the European common cuttlefish and reaches 60 cm in length. Jumbo flying squid (アメリカオオアカイカ) is also often used. The Jumbo flying squid is more than twice as long as the Flying squid and exceeds 1 meter in length. The Jumbo flying squid is mainly imported from places on the other side of the world such as Chile and Mexico. The thickness of the meat is similar to Mongou ika. However, a big drawback is that the Jumbo flying squid lacks the sweetness peculiar to squid. Therefore, it is soaked in water that has been artificially sweetened. This alters the dried out sensation to a plump, moist sensation, making the customer believe it is Mongou ika.

The squid must have a certain thickness in order to masquerade as Mongou ika. Rhomboid squid (ソデイカ), which has a torso length of 80 cm is also disguised as Mongou ika. Rhomboid squid is found in the warm waters of the world and is even caught in relatively high volume in Japan. Large squid have a low price cost, so it’s good for the shops to make a profit. Furthermore, the sweetness is brought out more when frozen first than by serving it fresh. That means it can be used as Mongou ika without any need for the artificial sweeteners used in Flying squid and Jumbo flying squid.

The fact is that there are many substitute products for Mongou ika. But even so, it doesn’t change the fact that using ingredients disguised as others is an unacceptable practice.


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Revision date: March 1, 2022

The general rule is to only eat oysters in months that contain the letter “R”.

In other words, avoid them from May to August.

an image of oysterIt’s won’t hurt you to eat Magaki (Japanese oyster), which has its spawning season in the summer, but in the months with no R in the name, the glycogen concentration is low, so you can’t get the full-bodied texture that you get in winter. In addition, almost all amino acids such as glutamic acid, glycine, alanine, arginine, which are important components for delicious flavor, are known to accumulate from winter through spring, and conversely, they decrease in the summer, which is the spawning season. You cannot expect the same deliciousness from oysters in summer as you can from months that contain the letter R.

Furthermore, the oyster takes in large amounts of seawater and filters out the plankton for its food. Therefore, in warm seasons it fills up on large volumes of the toxic plankton that proliferates in the sea. Eating toxic plankton can make the oyster toxic and toxified oysters can cause food poisoning when consumed by humans. In addition, in the warmer months, the oyster loses its freshness faster after being harvested, increasing the likelihood of getting a bad one and risk food poisoning. Therefore, it’s best to not go out of your way to eat oysters in summer.

On the other hand, one certain oyster is actually in season in summer.

Iawagaki (Rock oyster) is known as the summer oyster. This type is close to the Magaki, and it lives attached to reefs at depths of 2 to 20 m, deeper than the intertidal zone and facing the open sea. A large Iwagaki has a shell length of 10 cm, a shell height of 20 cm or more and weighs more than 1 kg. However, the edible part is small compared to the size of the shell. It is an oviparous hermaphrodite. Growth is slow at a rate of around 5 cm in one year, around 7 cm in two years. It takes three to four years to reach 10 cm or more and grow big enough to harvest.

The glycogen volume in Iwagaki is high from March to July, peaking around May, and it then decreases from September to October. The main production areas are the Sea of Japan on the coasts of Akita, Yamagata, Niigata, and Tottori. Many of the Iwagaki in circulation are harvested from the wild, unlike Magaki, which is almost all farmed.


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Revision date: February 1, 2022

A lesson on how the price of Nigiri sushi is determined

In order to prosper, a business wants to sell products at as high a price as possible. So how does a chef determine the price of nigiri sushi?

Naturally, the cost price is what it costs the restaurant for the ingredients while the price on the menu is the selling price. The ratio of these two prices is called the cost rate. In the case of a sushi restaurant, the ideal cost rate is 35% or less. A restaurant operating with only Omakase will have a cost rate of 40% with a focus on the quality of the toppings.

For sushi restaurants, handling of this ratio and the yield are very important. Yield refers to the part of the purchased fish and shellfish that can actually be used. For example, when purchasing a whole fish there are bones, skin, eyes, tail and internal organs that cannot be served as sushi or sashimi. No matter how good a chef is when preparing fish, the bones and skin will remain. In other words, the yield rate is the percentage of parts that can be used as sushi or sashimi. Typical fish yield rates are as follows:

Wild Maguro (Tuna): 65~75%

Buri (Japanese amberjack): 50%

Hirame (Bastard halibut): 40%

Tai (Red seabream): 35%

Akagai (Ark shell): 25%

Mirugai (Keen’s gaper): 20%

The weight of just the topping for a single piece of nigiri sushi is 12 to 18 grams, depending on the ingredients and the policy of the restaurant. The market price for rice is said to be about US$5 per kilogram, and assuming a weight of 15 grams per Nigiri, the rice for a piece of sushi is generally said to cost about US$0.05, including vinegar and salt. Even if you count the shari (sushi rice), soy sauce, wasabi, nori, etc., it’s fair to consider the cost to be about US$0.10.

Now, let’s figure out the price of Hirame, for which 3 kilograms were bought at $60 per kilogram. Assume that the weight of one topping is 15 grams.

The yield rate of Hirame is 40%, so the chef can make 1,200 grams of sushi toppings from 3,000 grams of Hirame. (formula: 3000 g × 0.4 = 1200 g). Since the weight of one topping is 15 grams, 80 pieces of sushi can be made from 3,000 grams of Hirame (1200 g ÷ 15 g = 80 pieces).

Next, we calculate the cost of one topping. Hirame is US$60 per kilogram, so US$180 (US$60×3 = US$180) for 3 kilogram. Since this volume can yield 80 pieces, the cost of one topping is US$2.25 (US$180÷ 80 pieces = US$2.25).

Add the shari price of US$0.10 to this: US$2.25+0.1=US$2.35. In other words, the cost of one Hirame nigiri sushi is US$2.35.

If the ideal cost ratio of 35% is applied here we get 2.35÷0.35 (35%) = US$6.71. For a restaurant serving mainly Omakase, 2.35÷0.4 = US$5.88.

In summary, one piece of Hirame sushi is sold between $5.88 and $6.71.

It may feel surprisingly cheap, but if you perform these calculations with Kuromaguro or Uni, it will be $60 to $90 per piece, and then you’ll feel that it is too expensive. Therefore, the total margin is secured by setting the cost rate for Kuromaguro and Uni to 80-90%, while the cost rate for Saba and Ika is set to 10-20%.

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Revision date: January 6, 2022

Is the combination of Chablis wine and Japanese oysters match made in heaven?

White wine is generally thought to go well with fresh seafood.

For example, every Frenchman knows that Chablis wine and Belon oysters go together like peanut butter and jelly. The soil of Chablis is made of the stratum that dates back to the Kimmeridgian age and a unique characteristic is that the soil is rich in fossils of small oysters and shellfish. That is why oysters and Chablis wine are said to be the perfect pairing. However, surely there are Japanese people who sense the fishy odor when having Chablis wine and Japanese oysters (Magaki) together. Therefore, some people say that sake is definitely preferred over wine.

The reason for this is that the types of oysters in France and Japan differ.

Famous for its Belon brand name, the oyster native to Europe has a flat, rounded shell. It belongs to the genus Ostrea. To be honest, Belon oysters aren’t sweet and don’t have a distinguished flavor compared to Japanese oysters, and the salty fragrance of the sea is dulled, so it can seem less flavorful.

Meanwhile, the Japanese oyster is elongated and shaped like a raindrop. It is characterized by a smell like it swallowed the whole ocean. This is the main species farmed in Japan. It belongs to the genus Crassostrea. The taste is as if the umami components of the sea have all been concentrated together in one little shell.

Going back to pairing Chablis wine with oysters, it’s common sense in the world of flavors that items with basically similar components pair well together.

The issue lies in how wine is made. Chablis wine contains lactic acid because it is made through forced mal-lactic fermentation. Because it contains this lactic acid, it is partially fighting against the Belon oyster, which has a high glycogen content. In addition, lactic acid is called “warm organic acid”, and it has the property of becoming delicious at warm temperatures. Oysters are eaten cold, so they aren’t good for taking advantage of “warm organic acids”.

Therefore, it can be said that rather than Chablis wine, it goes well with cold organic acid white wine that is delicious when cooled to 7 or 8 degrees, for example, German Franken wine.

So then, what should be done when pairing oysters with Chablis wine?!

If you insist on pairing oysters with Chablis wine, go all out and add squeezed lemon so the citric acid will work to mask the lactic acid and succinic acid, in turn making the wine taste good even when cold. Citric acid is a “cold organic acid” that becomes delicious when cooled, and oysters rich in glycogen go well with “cold organic acid”. Cold acid-based white wine is abundant in the refreshing “cold organic acids” known as malic acid and tartaric acid. Oysters lack this cold organic acid (malic acid and tartaric acid), so adding the citric acid of lemon creates an exquisite harmony.

However, in France there was a time when a disease spread that caused the death of the Belon oyster, nearly rendering it extinct. Therefore, since the Japanese oyster has been transplanted so many times, it is said that nowadays, at least 90% are Japanese oysters hybrids of Japanese oysters.

That means the question remains among Japanese as to whether the combination of Chablis wine and oysters really is a match made in heaven or not. Personally, we’ve never heard of oysters served without lemon, so the fishy smell really isn’t an issue at all in the end.


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Revision date: January 6, 2022

What is used as a substitute for Madako (Octopus)?

Among the many sushi toppings, Pacific bluefin tuna, and actually the Madai (Red sea bream) as well, are toppings that are difficult for an amateur to tell whether it is farmed or wild. However, there is no need to worry about that when it comes to Tako (Octopus). There are no octopus farms to be found in the world, so it is a 100% wild topping.

In Japan, domestic production isn’t enough to satisfy the appetite of Japanese who like Tako, so the majority relies on imports. Imports from Africa account for 80% and the remainder is imported from China, Southeast Asia, Mexico, Spain and other places in the world.

Most of the African imports are produced by nations on the northwestern coast, with the highest number coming from Mauritania. Until 2003 the highest volume came from Morocco for many years. However, due to continued mass catches to sell to Japan, Tako numbers dropped drastically, leading to the Moroccan government panicking and outlawing fishing. For some reason, Japanese people have grown to love Tako and now consume nearly half of the Tako caught throughout the world.

There are over 200 types of Tako in the world with approximately 60 types inhabiting the seas near Japan. Among these, the Japanese mainly only eat Madako, Mizudako and Iidako. Even among these, Madako makes up at least 80% of consumption.

Most of the Tako found at conveyor belt sushi is African Madako (Madako from Africa). African produced Tako is boiled on-site before being imported frozen. The cost is 20 cents or less per topping.

Amateurs can’t tell the difference between domestic Tako or African imports. However, there is one aspect that even an amateur can use to distinguish between the two. There is one condition for this to work, and that is that at least one of the suckers is in-tact. The suckers are scraped off for most toppings, but in cases where they are sliced by the restaurant, there are often suckers remaining. If the sucker is pure white, it is almost definitely from Africa. Meanwhile, domestic Tako suckers maintain a faint red color in the suckers, even when boiled. The reason the suckers turn white seems to be an effect of the food preservatives added during processing, but this has not been confirmed.

There happens to be a substitute for Madako as well.

One of these is the Iwadako from Vietnam, which grows as large as the height of an adult human. It is imported in frozen slices that can be used as raw Tako as soon as it thaws. The cost of this topping is 20 cents or less per piece. This ends up disguised as Hokkaido Tako.

There are also domestic substitutes. Yanagidako (Chestnut octopus) is mainly caught in the Pacific Ocean, from Chiba prefecture northward. The flavor is lighter than Madako, but it is also softer than Madako, so some people actually consider it to be better than Madako. If it is boiled and made into sushi, an amateur can’t distinguish between it and Madako. The legs are thin so they just need to be cut at an extreme angle in order to make the topping appear bigger. The cost of this topping is 15 cents or less per piece. It is also used as Mizudako because it is watery when eaten raw.

As you can see, there are also many substitute toppings for Madako.


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Revision date: December 21, 2021

What is Toro Katsuo (Torogatsuo)?

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.


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Revision date: December 1, 2021

What is Warisu?

Warisu refers to the vinegar when doing 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. After the Sujime of the topping is finished, it is important to place it in the refrigerator and allow the meat to mature slowly. For fish with strong fat, that fat oxidizes faster than the meat can mature, so it must be done very carefully.


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Revision date: November 23, 2021