Author: tabimori

It’s often said that when it comes to food, freshness is everything. However, greater freshness doesn’t always mean better flavor. Each type of food, such as vegetables, fish, and meat, has its own “peak ripeness” when it tastes its best.

When it comes to fish, the strong belief that “freshness is everything” can sometimes prevent us from fully appreciating its value. Consider fish that are still swimming before the customer’s eyes and then prepared on the spot. While its texture is unique and firm, its umami is weak, and its flavor is lacking. Yet, the notion that “fresh equals delicious” remains deeply ingrained, creating a mindset where belief in freshness outweighs actual flavor.

Let’s take this opportunity to reexamine what truly constitutes the perfect time to enjoy food at its most flavorful.

Vegetables, after harvest, continue breathing, consuming their internal sugars and nutrients while losing moisture, which causes their freshness to decline. To suppress this respiratory activity, effective methods include cold storage, packaging that prevents moisture evaporation, or storage in an environment with low oxygen and high carbon dioxide levels.

On the other hand, vegetables like potatoes and sweet potatoes become more delicious through aging. When potatoes are stored at low temperatures, cold-induced sweetening occurs, breaking down starch into sugar and increasing sweetness. Sweet potatoes also undergo curing after harvest (It forms a protective cork layer, preventing pathogen invasion and suppressing decay). Storing them at a specific temperature and humidity allows the starch to saccharify, enhancing their sweetness and sticky texture. However, apart from these specific examples, vegetables generally lose their freshness over time, so eating them right after harvest is when they taste best.

The optimal time to eat fish varies by species. Coastal migratory fish like sardines and mackerel spoil quickly, making freshness extremely important. These contain EPA, a beneficial fish oil, but since it is vulnerable to heat and oxidation, it is best to choose fresh, high-quality fish for raw consumption.

Even among blue-backed fish, large pelagic migratory species like tuna and yellowtail are different. If they are too fresh, their umami flavor is weak. The umami components increase once rigor mortis subsides and aging begins, reaching their peak flavor.

Furthermore, white-fleshed fish like red seabream and flounder also require careful handling. While Ikejime techniques are used to preserve freshness, freshly caught fish offer a firm, crisp texture. However, umami compounds increase after rigor mortis sets in, meaning “freshness” doesn’t necessarily equate to “deliciousness.”

Sushi chefs fully understand that the ideal eating time varies by fish species. They also fully understand that freshness ensures good texture. On top of that, they strive to balance seemingly conflicting conditions like optimal eating time and texture. In Japan, it’s not uncommon for fish caught by local fishermen to arrive at major city fish markets the same day. Some even arrive at the market still alive. So, freshness alone is something anyone can obtain.

Next, let’s look at meat. Chicken has a small body, and rigor mortis sets in quickly, within just 1 to 2 hours after death, allowing umami to develop rapidly. On the other hand, it also loses freshness quickly. Therefore, it’s safe to say that freshness is absolutely vital for chicken.

On the other hand, large animals like pork and beef require time for rigor mortis to subside, followed by maturation. The recently popular “dry aging” is a traditional method where meat is matured for about a month at 1-2°C while being exposed to airflow, resulting in tender, flavorful lean cuts. Additionally, “wet aging,” practiced in Japan for centuries, involves vacuum-sealing the meat and resting it at 0–2°C for 1–2 weeks, a method that also enhances umami.

Thus, meat isn’t necessarily more delicious the fresher it is; rather, aging increases umami components like inosinic acid, leading some to even say “some even say it tastes best when it’s on the verge of spoiling.” In other words, freshness and deliciousness don’t always go hand in hand.

In other words, the notion that “freshness equals deliciousness” isn’t always accurate; each ingredient has its own “peak flavor” period when it tastes best. What matters is not blindly trusting freshness, but understanding the characteristics of the ingredient and discerning its optimal eating window.

First, let’s confirm where chutoro and otoro are located on the tuna using a cross-section diagram of the fish’s midsection.

Looking at the tuna cross-section, the center part is red meat (Akami), while the surrounding areas closer to the skin are medium fatty (chutoro) and extra fatty (otoro). However, the borders aren’t clearly defined like this, so it’s merely a guideline. If the cut is closer to the tail, it will be just red meat.

Next, when the tuna is dissected, as shown in the illustration below.

The tuna is broadly divided into three main sections from the head: “Kami (Near the head)”, “Naka (Central section)”, and “Shimo (Near the tail)”. The back side is divided from the head downwards as “Sekami (se means back),” “Senaka,” and “Seshimo,” while the belly side is divided as “Harakami (hara means belly),” “Haranaka,” and “Harashimo.” Sushi chefs purchase these sections by width, measured from the index finger to the little finger. This width corresponds exactly to the size of one piece of sushi.

Now, let’s get to the main topic.

Basically, “otoro” refers to the fatty belly section of bluefin tuna or southern bluefin tuna. While various tuna species exist, this term is limited to bluefin and southern bluefin tuna. The term “otoro” isn’t applied to yellowfin or bigeye tuna, though yellowfin tuna can still be fatty. Japanese supermarkets sometimes use the term ‘toro’ for promotional purposes. In-season Albacore (bincho tuna) has exceptionally rich fat, and that cut is sometimes called “bintoro.” Depending on the cut, it can be divided into truly otoro-like otoro and otoro closer to akami-like chutoro.

Otoro generally includes all of the harakami and part of the haranaka. Furthermore, otoro also exists in the kama section near the pectoral fins. Otoro, much like marbled beef, is marbled with white fat. This gives it a rich, melt-in-your-mouth texture. However, some sushi chefs dislike it being too fatty and prepare it as aburi (seared) or zuke (marinated in soy sauce) to balance it with the shari (vinegared rice). Since otoro yields less per fish than akami or chutoro, its price is inevitably higher.

Chutoro, on the other hand, is found on both the belly and the back. It has a base of lean red meat with patches of white fat mixed in. It balances the savory flavor of the lean meat and the sweetness of the fatty tuna, making it universally popular. It consistently ranks among the top favorite sushi toppings for Japanese people. Some parts of the back section also yield a prized cut called setoro. In sushi restaurants, it is the second most expensive tuna cut after otoro.

Incidentally, farmed bluefin tuna and southern bluefin tuna tend to have a higher proportion of fatty parts (toro) compared to wild tuna. This is because they are raised in confined cages with limited exercise and are fed high-fat feed.

The question then arises: where exactly is the boundary between otoro and chutoro?

In reality, there is no clear-cut definition. The distinction is made by tuna wholesalers and sushi restaurants based on years of experience and practical knowledge.

One initiative in producing regions involves branding fish. When certifying branded fish, various criteria are used. One of these is the fish’s fat content. This is objective data and significantly impacts the fish’s deliciousness. The method involves simply touching the fish with the tip of a measuring device, taking only a few seconds. For example, the peak fat content of mackerel imported from Norway to Japan is reportedly around 25-30%.

For otoro, this value is over 20% and can reach 40%. Chutoro is often said to be 15-20%, but such standard values actually don’t exist.

Sushi chefs determine whether it’s chutoro or otoro by cutting the purchased portion into akami, chutoro, and otoro. If the fat content is 15%, it should be classified as chutoro, but if the sushi chef says it’s otoro, then it becomes Otoro.

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You know toro tuna and akami, but have you heard of the more rare parts of the tuna?

We hope this information will be helpful.

Revision date: October 1, 2025

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Wasabi, a vegetable native to Japan, is traditionally served with raw fish dishes such as sashimi. While it has antibacterial properties, its primary role is to enhance the flavor of the fish. Japan has numerous aromatic vegetables, including wasabi, ginger, myoga, green onions, and sansho pepper, among others. Each possesses a unique aroma and aromatic compounds. Adding these to other foods or mixing them during cooking stimulates the taste buds, significantly enhancing the flavor of the dish. Since all these aromatic vegetables have antibacterial and sterilizing effects, they are often served with sashimi and similar dishes.

The pungent flavors of these aromatic vegetables can be broadly categorized into three types: the sharp, stinging heat of wasabi; the fiery, burning heat of chili peppers; and the numbing, tingling heat of sansho peppers. Each type has different components responsible for its distinct heat. Let’s examine them individually.

The pungent component in wasabi is a substance called sinigrin. Sinigrin itself has no pungency, but when the cells are broken down by grinding or similar processes, exposing sinigrin to oxygen in the air causes the enzyme myrosinase to produce a substance called allyl isothiocyanate. This allyl isothiocyanate is the pungent component in wasabi and Leaf mustard or Mustard greens. Wasabi is a plant in the Brassicaceae family, and sinigrin is a substance widely found in vegetables of this family. The pungent taste in other Brassicaceae plants like Mustard cress or Daikon mustard also comes from sinigrin. Wasabi simply contains a particularly high amount of it.

There are two types of wasabi: Sawa wasabi and Yama wasabi. Sawa wasabi is the common, green variety you see most often. Yama wasabi, on the other hand, is the horseradish served with roast beef and similar dishes. Although both are wasabi, their shape and color are completely different. Yama wasabi resembles spicy radish and is used as the base for prepared wasabi paste and powdered wasabi. It has low moisture content and is large in size, resulting in a high yield, making it well-suited for processed products.

Wasabi has been consumed since the Heian period, with records indicating it was eaten mixed into dishes like grated yam broth. At that time, there seemed to be established rules: carp sashimi was served with wasabi vinegar, sea bream sashimi with ginger vinegar, and sea bass sashimi with tade vinegar. Given the era’s hygiene concerns, it’s likely a considerable amount of aromatic vegetables were used. Wasabi began to be eaten with soba noodles, now commonplace, around the Edo period. Originally, spicy radish was served alongside soba. However, when radish was unavailable, wasabi was substituted. It is said that wasabi became a staple because it masked the distinctive fishy odor of the bonito flakes in the soba dipping sauce. Generally, it’s hard to imagine wasabi replacing radish.

Next, when it comes to chili peppers in Japan, Takanotsume (Bird’s eye chili) and Shichimi togarashi (seven flavor chili pepper) are common. Bird’s eye chili is often added to preserved foods such as rice bran pickles, and it has also been traditionally kept for medicinal purposes. This is because Bird’s eye chili also has antibacterial properties. It offers significant health benefits, burning body fat, warming the body, opening pores, and promoting sweating. It is especially effective in winter for raising body temperature. In summer, eating spicy food induces sweating, allowing moisture to evaporate along with body heat, thereby lowering temperature. The capsaicin in Bird’s eye chili promotes fat breakdown and accelerates the breakdown of glycogen in the liver and muscles. Consequently, it not only stimulates the stomach and improves blood circulation but also activates digestive movements within the internal organs, boosting appetite. It is effective during winter when lack of exercise reduces appetite, and also combats summer fatigue-induced loss of appetite.

Chili peppers have also been widely used in preserved foods like pickles, miso, and tsukudani. Their intense pungency and antibacterial properties enhance the shelf life of ingredients, making them a cherished seasoning that supports Japanese dietary habits.

The numbing spiciness of sansho comes from a compound called sanshool. Sanshool increases gastric acid secretion, making it a perfect match for rich, fatty dishes like eel. It also contains an aromatic compound called diterpene, which boosts immunity and enhances antioxidant effects. The name “sansho” (山椒) itself comes from the mountain-scented fruit that is spicy like pepper. Sansho is known as Japanese pepper in English, making it an iconic spice of Japan.

Furthermore, sansho has been utilized in diverse dishes by selecting either the berries or leaves. It is also used in preserved foods like tsukudani and chirimen sansho, enhancing ingredient preservation through its refreshing aroma and antibacterial properties. Additionally, in ancient times, it was valued medicinally as the herbal remedy “Shokushō (蜀椒),” prized for its stomach-strengthening and anthelmintic effects.

In other words, the practice of always serving wasabi with sushi and sashimi is not merely a custom. It is a tradition born from the convergence of scientific reasons like sterilization and antibacterial properties, the culinary ingenuity of maximizing the umami of fish, and the wisdom cultivated by the Japanese people throughout history. Wasabi is more than just a condiment; it is passed down to modern dining tables as a “key component” that elevates the dish’s overall quality.

Both Aburi and Tataki are Japanese cooking techniques that involve exposing food to high heat, but they differ in both purpose and process.

Aburi means “to sear,” and refers to lightly grilling the surface of food while leaving the inside raw.

In sushi, aburi is often applied to fatty cuts like salmon or tuna, where the flame enhances aroma, melts fat, and creates a contrast between the charred surface and the fresh interior. Some chefs use handheld gas burners, though Edomae-style masters often disapprove because of the faint odor left by the gas. For them, aburi is not about making the fish richer, but about controlling fat so the sushi remains balanced.

Other methods such as charcoal grilling, ovens, or iron plates can also be used, producing different aromas and textures. Aburi also appears in vegetables—like peppers or eggplants whose skins are charred and peeled—and in desserts such as crème brûlée or baked custard pudding, where caramelized surfaces are essential.

Tataki, in contrast, is more polysemous. In its seared form, tataki refers to quickly grilling the surface of fish or meat, then cooling it and slicing it.

Unlike aburi, tataki is always finished with seasonings: the slices are eaten with condiments such as soy sauce, ginger, garlic, or other pungent garnishes. This seasoning process is essential to the identity of tataki. The best-known example is katsuo no tataki from Kochi, where bonito is straw-seared, chilled in ice water, and served with generous amounts of aromatic condiments.

The term tataki also extends to finely chopping fish into a mince or even a paste, and to vegetables like cucumber or burdock root that are pounded to soften their texture, but in comparison with aburi, it is the seared and seasoned preparation that is most relevant.

Thus, while both techniques highlight the interplay of cooked and raw, aburi serves primarily as an aromatic finish that enhances natural flavor, whereas tataki is a preparation that combines searing with deliberate seasoning. This requirement of seasoning after searing marks a fundamental difference between the two.

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