It is probably cutting fish just before serving. For a big size fish, keep its skin on the meat during the process of preparing and cutting into half, and at every serving use sogigiri* as much as customers eat. Protected by the skin, the fish flesh will expose to air for the first time as it is cut. The skin blocks the oxidation process significantly because the fat in fish centers right under the skin in general. Needless to say, even with any amazing fish, it loses flavor if the fat gets oxidized.
＊Sogigiri－A method of cutting makes a slice thinner with a greater surface, by holding the knife diagonally and cutting in line with the cutting board. Usually used for white fish with firm flesh because it is easier to be eaten when served thin.
Hirazukuri－A method of cutting gives thickness to each slice so that the texture of sashimi can be enjoyable. This is used for akami like tuna.
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Revision date: April 1, 2020
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Once tuna caught in the open sea is processed by draining its blood on the ship, it is flash-frozen at ultra-low temperatures (-60℃). Ultra-low temperatures stops the enzymatic hydrolosis of protein, oxidation of fat and cultivation of microorganisms so it can be stored over a long period of time. The process can prevent discoloration for over two years and maintain a freshness worthy of being served as sashimi. Therefore, skillful sushi restaurants mature the thawed tuna in the refrigerator for about one week to attain the perfect balance of umami and change in color.
In the United States and other countries, “
As an aside, three cousins (closely related species) of buri are often used as sushi toppings in sushi restaurants. In the Fish Name Dictionary, the translations of these cousins are Goldstriped amberjack (
I’m sure you’re interested in the price, and while the price of the seasonal winter buri varies, it is generally around $10-20 per kilogram. Since there is very little distribution of hiramasa, the price is said to be about double that of buri. The price of 
Why is only tuna brought into certain ports high-priced, even though all of the tuna is caught in the seas near Japan? This is because the level of stress caused to the fish when it is caught has a huge impact on the quality, including taste, color and texture. In other words, the same fish may be delicious or taste unpleasant depending on how the fisher handles the fish directly after catching it. Naturally, everyone ends up wanting the fish from the ports with fisherman who are skilled in this practice*. Furthermore, it is individuals who process the fish. The quality changes drastically depending on who caught it.
However, sushi chefs will remove the topping from the refrigerator and leave it standing out for a while (in the case of tuna, the fat will melt at around 23℃). They do this because if the topping is cold, it becomes difficult to taste the essential nature of the fish. The temperature of the shari is best at human skin temperature (around 36℃) to maximize the taste and sweetness of the rice. However, the ideal temperature differs very slightly depending on the topping.
For example, conger eel which is often lightly grilled or prepared in another, similar way, should have a slightly higher temperature (around 42℃) than the shari, and kuruma prawn, which are boiled, should be the same temperature as the shari.
No one is more sensitive to the changing of the seasons than sushi lovers. This must be because the taste of sushi toppings is directly tied to the seasons. There are terms to describe this such as Hashiri (early season), Sakari (in-season) and Nagori (late season), and using these words to understand what state the sushi topping is it allows you to grasp and enjoy the various different flavors. There is nothing that says a sushi topping is less delicious because it has a lower fat content.
Japanese mustard refers to 
Fish seasons are categorized as the ‘catch season’ and the ‘flavor season’. The ‘catch season’ is the time when lots of fish can be caught and are cheap. Take Japanese Spanish mackerel (Sawara), for example, they approach the coasts during the spring to spawn and this is the peak season. This is the catch season. Once they’re about to spawn and their bodies fatten for winter, we’ve entered the tasting season. However, these seasons differ depending on the region, and may be longer or even happen twice a year.
At high-class restaurants, the minimum required nikiri soy sauce is brushed on to the piece, but at restaurants frequented by the general public, customers dip their sushi in as much sauce (soy sauce that includes chemical seasonings) as they like. In fact, there is a gimmick here. The high-class restaurant provides an opportunity for their customers to eat sushi toppings in the most delicious state possible, but the restaurants for the general population allow customers to eat casually with sauce, a daily necessity. This changes how topping ingredients are selected. If the sushi is going to be dunked into the soy sauce, then the topping must have an appropriate fat content that won’t be overpowered by the soy sauce. Therefore, instead of a coastal tuna, a farm-fattened tuna with oily fat is preferred. It is often said that farm-fattened products are too rich, but it is also said that they have an impact that isn’t overpowered by the sauce they are enjoyed with.
There is a sensor on the tongue that feels the degree of saltiness. This prevents us from eating too much of things that are extremely salty. Chemical seasonings confuse that sensor. The chemical seasoning palliates the degree of saltiness felt by the tongue. Even if you were to, for example, dunk your sushi into the soy sauce and chemical seasoning mixture, it won’t feel salty. If you eat sushi with the sauce, you can take in a high volume of sodium, which is a pleasure trigger for the human body, without feeling the saltiness on your tongue. In other words, it may be more accurate to say that with commoner sushi, you actually drink the sauce, not dip into it.
The difference between common people who eat this sauce and foodies is a delicate nose, meaning their sense of smell. This sense is acquired through childhood experiences and repetition after becoming an adult. Tasting through sense of smell is a person’s food culture. The reason that the so-called celebrities, or the upper class made through business success, don’t have an appreciation for high-class sushi restaurants is because they don’t have this culture of distinguishing by smell, or the culture of feeling the seasons. Also, in order to target the upper-middle class clientele, it is important to use strong flavors and give a performance that is easy to understand, while worrying about details is not necessary. That is why the obvious show of using a burner for searing is popular.
Natural fish are part of the food chain and have concentrations of harmful substances. Since 2000 the amount of mercury found in fish has become an issue. The American Natural Resources Defense Council has said tuna is a fish that should be avoided if pregnant or planning to get pregnant. A more recent problem is the large amounts of micro plastics found in fish meat. This shocking phenomenon will likely be reported by research organizations at some point in time. If it does reach that extreme, then it will be better to avoid the danger of eating fish.