Category: Basic Knowledge

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.

Related contents:

What is “Katsuo no Tataki”?

The freezer compartment of a household freezer typically operates at -18°C. However, in practice, due to factors such as how often the door is opened and closed, the temperature often only reaches around -12°C. While this is cold enough to freeze water, it does not freeze the core of the food, so it may appear frozen at first glance. Proteins, enzymes, and lipids remain unfrozen, causing the taste and texture of the food to deteriorate significantly within a few weeks.

On the other hand, ultra-low temperature freezing can freeze all the components of fish meat, suppressing protein decomposition and stopping lipid oxidation. This makes it possible to store food for up to six months. All living organisms begin to age and deteriorate after death, eventually leading to oxidation and decay. The temperature that can stop this process is the world of ultra-low temperature freezing at -42°C.

Inhibition of enzymatic protein degradation

Under normal conditions, proteins that have ceased activity at room temperature undergo enzymatic degradation. For example, the proteins in freshly caught fish are in a high-molecular-weight state. Through enzymatic degradation, they break down into lower-molecular-weight compounds, advancing the aging process. If this process progresses too far, decay occurs.

Additionally, fish have a high water content of 70%, making them age much faster than livestock meat. Therefore, the key is to quickly cool the fish to ultra-low temperatures after catching them and then thaw them while maintaining the aging process.

Inhibition of fat oxidation

What is commonly referred to as “freezer burn” occurs when the fat naturally present in food rises to the surface and oxidizes, causing the color to turn yellowish and the appearance and taste to deteriorate. To prevent this, it is essential to prevent the food from coming into contact with air. Furthermore, by storing it in an ultra-low temperature environment, the oxidation process itself can be almost completely halted.

Inhibition of microbial proliferation

Even at the -18°C environment of a household freezer, microbial proliferation can be largely suppressed. However, for complete inhibition of all types of microbial growth, ultra-low temperatures are ideal.

Real-world applications

Ultra-low temperature freezing is already widely used in the seafood industry. At Tokyo’s Toyosu Market, premium tuna is stored and transported at -60°C to preserve its deep red color, fatty texture, and fresh taste for overseas shipments. In Hokkaido, Pacific saury is frozen at -50°C immediately after being caught on specialized vessels, allowing them to be enjoyed months later with near-fresh quality. Some Japanese supermarket chains use -45°C freezing for salmon fillets, enabling them to offer sashimi-grade products all year round while minimizing quality loss.

In sushi restaurants, anago (saltwater eel) is often purchased in bulk when prices are stable, stored at ultra-low temperatures, and thawed to maintain quality and cost efficiency. Likewise, ikura (salmon roe) is typically prepared in autumn, its peak season, and frozen for year-round use, ensuring consistent flavor and texture regardless of the season.

The fact that a 10,000-year-old mammoth excavated from Siberian permafrost was still edible after being cooked is a testament to the capabilities of ultra-low temperatures.

In Japanese culinary terms, “nitsumeru” (verb) refers to the process of reducing the liquid content of a sauce containing seasonings by boiling off the moisture, thereby concentrating the flavor and increasing its thickness. Both “eel sauce” and “conger eel nitsume” are sauces made by reducing the liquid content through boiling.

First, you need to understand the difference between eel and conger eel.
In Japanese, the word “unagi” generally refers to a freshwater eel. The scientific name is Anguilla japonica Temminck & Schlegel, 1846. On the other hand, the word “anago” generally refers to the conger eel. Its scientific name is Conger myriaster (Brevoort, 1856).

While both eel sauce and conger eel nitsume are made by reducing liquid through boiling (the process known as nitsumeru), only the latter is traditionally referred to as “nitsume” in sushi restaurants.

So, what is the fundamental difference between them?
Eel sauce (known as unagi sauce or unagi no tare) is a rich, sweet soy sauce-based sauce that is ideal as a dip or drizzling sauce. It does not actually contain any eel ingredients, but it is a sweet, sticky sauce that is perfect as a topping for sushi rolls and other dishes.

“Eel sauce” can refer broadly to both mass-produced sauces and artisan sauces made by eel restaurants. The basic method for making eel sauce is to mix mirin and soy sauce and heat it. Various ingredients such as sake, sugar, tamari soy sauce, water amber, honey, dashi, and potato starch (commercial products often contain thickening agents) are added to create a unique flavor.

Incidentally, most traditional eel restaurants make their eel sauce using only high-quality mirin and soy sauce. This gives the eel a beautiful glaze and subtle sweetness when grilled, as well as a clean aftertaste, which is why it is considered a craftsmanship.

When making kabayaki, the process of applying eel sauce is repeated multiple times. The components of the eel sauce combine with the umami of the eel to create a deeper, more complex flavor. In addition, applying the sauce and grilling it causes chemical reactions such as the Maillard reaction and caramelization, which further enhance the appetizing flavor.

While you can easily buy eel sauce at the market, it’s incredibly easy and tasty to make at home. Eel sauce can be used as a seasoning for other dishes if there is any left over, but it is primarily a sauce specifically made for making kabayaki. By the way, kabayaki is a fish dish where the long-bodied fish is filleted, the central bone removed, skewered, grilled, and then coated with a thick sauce before being grilled again. In Japan, when people say “kabayaki,” they are usually referring to “unagi kabayaki.” Other ingredients used include hamo and anago.

Nitsume is brushed onto nigiri sushi made with anago, shako, shellfish, and other toppings. In sushi restaurants, it is often abbreviated as “tsume.” There are several methods for making nitsume, including reducing the cooking liquid from simmered conger eel, or simmering the head and bones of conger eel to extract the broth, then adding seasonings and reducing it further. In other words, nitsume contains components of conger eel.

Compared to anago, unagi is more flavorful, fatter, and meatier. Moreover, unagi is considered a higher-quality delicacy in Japan and is therefore more expensive. In terms of taste, unagi has a richer, more intense umami flavor. The common opinion is that anago, because of its lighter taste, harmonises better with soured sushi rice and is therefore the preferred choice for making nigiri sushi.

As a side note, while nigiri sushi with eel is common in the Kansai region, eel is not used as a sushi topping in Edomae sushi. Therefore, Edomae sushi restaurants do not serve unagi nitsume.

In summary, unagi (eel) sauce is made by eel restaurants, while anago (conger eel) nitsume is made by sushi restaurants. Eel sauce does not contain eel components, while conger eel nitsume contains conger eel components.