Sushi chefs use shiraita kombu to prevent the mackerel sushi from oxidizing.
The reason Kansai-style sushi makes extensive use of kelp—in the form of shiraita kombu (thinly shaved kelp), kelp broth, kelp rolls, and kelp-cured fish—is not simply because kelp contains umami, but because it treats sushi not as a “dish completed in an instant,” but as a “dish that develops over time.”
Kansai sushi, particularly oshi-zushi and hako-zushi, developed within a food culture that prioritized preservation. As a result, fish has been treated not just as something to be enjoyed at peak freshness, but as an ingredient whose texture and flavor are gradually stabilized through salt and vinegar, forming a cohesive whole over time. For this reason, sushi is designed to reach its final flavor and form through a series of carefully layered processes.
Within this approach, kombu functions not simply as a seasoning, but as a foundational ingredient that shapes both flavor and texture. Shiraita kombu enhances the visual appeal of pressed sushi while covering fish such as mackerel to protect it from air, preventing drying and oxidation, and helping preserve both flavor and quality. Kombu dashi enhances the depth of the rice’s flavor, while kombu-zume draws out excess moisture from the fish and stabilizes its texture. Kombu-maki wraps the ingredients, allowing the flavors to gradually meld over time.
In other words, kombu serves multiple roles. It is used across different layers—inside, outside, and as a finishing element—each contributing in a different way to stabilize both flavor and structure.
This is rooted in history. Kelp was transported in large quantities to the Kansai region via Kitamae trading ships, becoming not a luxury item but an everyday ingredient. Over time, the idea that “umami comes from kelp” became widely shared.
As a result, in Kansai sushi, kelp is used not as decoration, but as a fundamental part of the sushi itself, supporting the entire dish in multiple ways.
Although Kansai-style pressed sushi and Edomae-style nigiri sushi (Edomae sushi) are both categorized as “sushi,” their historical backgrounds and underlying philosophies differ significantly. The differences between the two go far beyond shape; they reflect distinct urban structures, distribution environments, and regional attitudes toward food.
In particular, Kansai-style pressed sushi (Hakozushi and Bozushi) developed under the conditions of preservation and transport. Its core regions include urban centers such as Osaka and Kyoto, where refrigeration technology as we know it today did not exist. As a result, it was difficult to transport seafood over long distances while keeping it fresh. This made extending the shelf life of ingredients a central concern in culinary development.
Within these constraints, a method emerged in which vinegared rice and toppings were layered in a wooden mold and pressed firmly from above. Oshi-zushi is not merely a shaping technique. The pressure helps remove excess air and moisture, slows bacterial growth, and improves shelf stability. Vinegar itself also has antibacterial properties, and when combined with fish, it became a highly practical form of preserved food for its time.
In addition, oshi-zushi offers a high degree of physical stability. Pressing the ingredients into a wooden mold creates a compact, block-like form with uniform thickness and density. This makes it resistant to crumbling, easy to slice, and well-suited for transport. It is especially practical for celebrations, festivals, and travel meals, striking a strong balance between practicality and refined presentation.
This “molded form” is also closely tied to the aesthetic sensibilities of Kansai food culture. The cross-section of oshi-zushi reveals fish and vinegared rice arranged in precise, geometric layers, creating a visual presentation reminiscent of an edible artwork. In this sense, it is not only a dish to be tasted, but also one meant to be seen.
In contrast, Edomae sushi developed under entirely different conditions. In Tokyo, as population density increased and urban life expanded, a vibrant street food culture emerged. Here, the emphasis was on immediacy—being able to eat sushi right away, convenience, and enjoying freshness at the moment of service. As a result, sushi evolved into a form centered on instant consumption.
The shari is shaped just enough to hold its form without falling apart.
A defining feature of nigiri sushi is that the rice is gently shaped to retain air, creating a light, tender texture. This is not simply about softness. The air allows the rice to break apart easily in the mouth, while the fish and rice are designed to come together and dissolve simultaneously, creating a unified flavor experience. In other words, nigiri sushi is designed to deliver a culinary experience that is complete the moment it is formed, emphasizing lightness and immediacy.
What is important here is that the difference between the two is not simply technical, but reflects fundamentally different ideas of how food should reach its peak condition. Kansai-style pressed sushi is designed to remain stable and well-balanced even after some time has passed. Edomae nigiri sushi, on the other hand, is designed to be at its best immediately after it is made.
In this sense, oshi-zushi is a style of sushi that maintains its quality over time, while nigiri sushi is a style that reaches its peak in an instant.
What makes this even more interesting is that both share the same foundation of vinegared rice. Using the same core ingredient, entirely different eating experiences are created simply through physical technique—pressing versus shaping. This demonstrates that Japanese cuisine is not merely dependent on ingredients but is a highly refined culinary culture built on structure and design.
Ultimately, pressing oshi-zushi firmly is not just about compression, but a practical method of achieving preservation, structure, and visual harmony at the same time. Conversely, gently incorporating air into nigiri sushi is a deliberate design choice to maximize fleeting texture, aroma, and mouthfeel.
Although both are forms of sushi, the key difference lies in how each is designed to reach its optimal eating condition.
A Complete Guide to Japan’s Essential Sweet Cooking Wine
Mirin is one of the foundational seasonings in Japanese cuisine. It is widely used in dishes such as teriyaki, simmered foods, sukiyaki, mitarashi dango, and tamagoyaki. Its ability to add gentle sweetness, depth, and a beautiful glossy finish makes it indispensable in Japanese cooking.
While mirin is rarely used in sushi restaurants, substitutes like sugar or sake are not the same. To truly understand Japanese cuisine, it helps to understand mirin properly.
1. What Is Mirin?
Definition
Mirin is a traditional Japanese sweet cooking wine made from glutinous rice, rice koji (rice inoculated with fermentation mold), and shochu (distilled alcohol). Unlike simple sweeteners, mirin develops its sweetness naturally through enzymatic saccharification and aging.
The result is a seasoning that provides sweetness, depth, and shine — all at once.
Alcohol Content
Authentic mirin, known as hon mirin, contains approximately 13–14% alcohol by volume. Under Japanese law, it is classified as an alcoholic beverage and is regulated accordingly.
When heated during cooking, most of the alcohol evaporates, leaving behind sweetness and flavor.
Flavor Characteristics
Mirin’s sweetness is mild and rounded rather than sharp. It comes from multiple naturally occurring sugars such as glucose and various oligosaccharides.
During cooking, mirin:
Adds gentle sweetness
Enhances depth and umami
Creates a glossy finish
Helps balance saltiness
Aging also produces amino acids and organic acids that contribute complexity and richness.
2. Types of Mirin
Not all mirin is the same. There are several categories available in Japan and abroad.
Hon mirin is made through traditional saccharification and aging. Some versions contain added sugar, while others rely entirely on natural enzymatic conversion. Both qualify as hon mirin if made from the core ingredients.
This type provides the most depth, gloss, and authentic flavor.
Mirin-Style Seasoning
Alcohol: Less than 1% Salt: Less than 1%
This product was developed to avoid liquor taxes. It contains added sugars and flavor enhancers to approximate mirin’s taste.
Advantages:
Lower cost
Can be used without cooking off alcohol
Widely available
However, it lacks the complexity of hon mirin.
Salted Mirin (Fermented Seasoning)
Alcohol: Typically 8–14% Salt: About 2%
Salt is added to prevent it from being classified as alcohol under tax law. Because of the salt content, seasoning adjustments are necessary when cooking.
3. The History of Mirin
Mirin is believed to have originated between the Warring States period and early Edo period. There is no definitive consensus on its origins, and two major theories exist.
Chinese Origin Theory
A Ming Dynasty Chinese text mentions a sweet liquor called “mi-lin (密淋),” described as sweet like dripping honey. Some scholars believe this beverage was introduced to Japan via Ryukyu and Kyushu during the Warring States period and gradually evolved into hon mirin.
Japanese Origin Theory
Japan already had sweet rice-based alcoholic drinks such as nerizake (練酒) and shirozake (白酒). Records from the 15th century describe sweet liquors brewed in Hakata.
These early drinks were sweet but prone to spoilage. The later addition of distilled alcohol (shochu) improved preservation and stability, eventually leading to modern mirin production.
From Sweet Drink to Essential Seasoning
By the mid-Edo period, mirin was popular as a sweet alcoholic beverage. As Japanese culinary culture matured, it gradually shifted from being consumed as a drink to being used as a seasoning.
By the late Edo period, records clearly show mirin being used in eel sauce and soba dipping sauce in the Kanto region. From that point forward, mirin became an essential component of Japanese cuisine.
4. How Hon Mirin Is Made
Hon mirin differs from sake in one crucial way: it does not rely on yeast fermentation.
Instead, shochu is added at the beginning. The alcohol activates enzymes in the rice koji, which break down starch in the glutinous rice into sugars.
Key Steps
Steamed glutinous rice is prepared.
Rice koji provides enzymes (amylase and protease).
Shochu is added.
Saccharification and aging occur over time.
During this process:
Amylase converts starch into sugars.
Protease breaks proteins into amino acids.
Sugars, amino acids, and organic acids interact during aging to create depth and complexity.
Pressing and Finishing
After maturation, the mash is pressed to separate:
Mirin liquid
Mirin lees
The liquid is filtered and bottled.
Traditional breweries may use wooden press methods, while modern facilities often use mechanical or centrifugal systems.
5. The Role of Mirin in Cooking
Mirin does far more than add sweetness.
Reduces Unwanted Odors
When heated, alcohol evaporates and helps carry away unwanted odors from meat and fish. Aging compounds also help mask strong smells.
Prevents Ingredients from Falling Apart
Sugars and alcohol interact with the surface of ingredients during cooking, helping them maintain their shape. This is especially useful in simmered dishes.
Adds Depth and Umami
Because mirin contains amino acids and organic acids, it adds more than sweetness — it enhances overall flavor complexity.
Provides Gloss and Shine
As it cooks, mirin forms a light glaze on the surface of food, creating the beautiful shine seen in teriyaki dishes.
Enhances Flavor Penetration
Alcohol helps other seasonings permeate ingredients more effectively, resulting in deeper flavor absorption.
6. Choosing Between Hon Mirin and Mirin-Style Seasoning
Choose Mirin-Style If:
You want convenience
You prefer lower alcohol
You need a budget-friendly option
Choose Hon Mirin If:
You want deeper flavor
You care about authentic results
You are making traditional simmered or glazed dishes
If using hon mirin without cooking, you may want to briefly simmer it first to evaporate the alcohol.
7. Storage Tips
After opening, store mirin in a cool, dark place or in the refrigerator. Over time, it may darken slightly — this is a natural result of maturation.
Avoid over-reducing it during cooking, as excessive heat can concentrate sweetness too much.
8. Availability Outside Japan
Outside Japan, hon mirin and mirin-style seasonings are typically available at Japanese grocery stores and some Asian markets.
Common substitutes such as white wine mixed with sugar or sake with added sugar may approximate sweetness, but they do not replicate mirin’s complexity, gloss, or depth.
Final Thoughts
Mirin is far more than a sweetener. It is a carefully crafted cooking wine that adds balance, shine, depth, and refinement to Japanese cuisine.
Understanding the difference between hon mirin and imitation products allows you to cook Japanese dishes with greater authenticity and precision.
Kochi’s Inaka sushi (pronounced inaka-zushi in Japanese) is a unique style of sushi that developed in the mountainous regions of the prefecture. Unlike typical nigiri sushi (pronounced nigiri-zushi), which highlights seafood, Inaka sushi is defined by topping vinegared rice with locally harvested vegetables and wild mountain greens.
Although Kochi Prefecture faces the Pacific Ocean and is known for its seafood, Inaka sushi originated in inland areas where fresh fish was scarce. It emerged from the ingenuity of mountain communities, who created special dishes using the ingredients they had on hand. At the time, rice was a precious commodity, and sushi was mainly prepared for special occasions such as weddings, funerals, and festivals. Compared to fish-based sushi, Inaka sushi was more affordable and kept longer, eventually becoming a staple in everyday life.
Representative Ingredients
The main ingredients of Inaka sushi are familiar staples in mountain villages:
Myoga (Japanese ginger): Boiled and pickled in sweet vinegar, myoga ginger highlights its refreshing aroma and vibrant color. It is traditionally prepared to welcome guests.
Ryukyu (taro stem): Also called hasuimo, this taro variety is eaten only for its stem, which has a crisp, satisfying texture. The stems are lightly prepared to maintain their crunch.
Konjac: In areas where fried tofu was not readily available, mountain communities used konjac as a substitute. The konjac is shaped into a pouch, cut, and simmered in a sweet-savory sauce to absorb flavor.
Shiitake mushrooms: Simmered with dashi, sugar, and soy sauce to enhance their natural umami. Some recipes also include small dried fish or finely grated raw fish for a simple, rustic flavor.
Bamboo shoots and zenmai (royal fern): Seasonal mountain vegetables that appear primarily in early spring.
Each ingredient is individually seasoned and placed on slightly sweet vinegared rice, then gently pressed. While visually similar to nigiri sushi, Inaka sushi’s charm lies in its mild flavor, which allows the natural taste of the ingredients to shine. Its colorful presentation—red myoga, green ryukyu, dark shiitake, and yellow bamboo shoots—reflects the vibrant hues characteristic of Kochi’s cuisine.
Seasoning and Vinegared Rice
Inaka sushi is made with slightly sweet vinegared rice, seasoned with a balanced mix of vinegar and sugar. The toppings are often simmered in a sweet-savory sauce, creating a gentle, rounded flavor profile. Rather than relying on strong saltiness or fatty richness, the dish is defined by the harmony of dashi and sweet vinegar. In Kochi, citrus fruits such as yuzu are sometimes added to the sushi vinegar, giving the rice a subtle aromatic note.
Role as Festive Food
Traditionally, Inaka sushi was prepared not for daily meals, but for special occasions such as festivals, celebrations, or visits from guests. The sight of community members arranging colorful sushi on large platters symbolizes the cooperative culture of mountain villages. Today, Inaka sushi can be enjoyed at local restaurants, farmers’ markets, and specialty shops throughout the prefecture, including around Kochi City, making it accessible for both locals and tourists.
Modern Significance
Inaka sushi is often plant-based, making it well-suited for vegans and vegetarians. However, its essence lies not in replacing fish-based sushi, but in the creativity and resourcefulness of mountain communities using local ingredients. As a “mountain sushi” distinct from ocean-based nigiri, Inaka sushi reflects the climate, landscape, and daily life of Kochi, representing a unique regional food culture.
Many Westerners find black nori spooky, leading some to avoid onigiri (rice balls) and norimaki (rolled sushi). Yet it’s an indispensable ingredient in Japanese sushi, with sushi chefs even saying they “eat the aroma of nori.” Its appeal isn’t merely about flavor—it’s supported by scientifically backed aromatic compounds. Let’s take a closer look at how nori’s aroma directly contributes to the deliciousness of sushi.
One of the main components of nori’s aroma is dimethyl sulfide (DMS), a volatile sulfur compound. DMS contributes to nori’s distinctive “ocean aroma” and is detectable at very low concentrations, making nori’s flavor highly memorable. Additionally, nori contains aldehydes, ketones, alcohols, esters, and decomposition products derived from fatty acids. These elements create the nori’s complex fragrance.
Nori also contains umami components like free amino acids, taurine, and inosinic acid. The combination of aroma and taste ensures that the flavor and deliciousness of nori are richly perceived the moment it’s eaten. DMS, in particular, while not directly contributing sweetness or umami, triggers the brain to associate its “sea aroma” with freshness and rich flavor. This creates an effect where simply smelling it anticipates deliciousness. The aroma that gently rises immediately after cutting or upon entering the mouth naturally conveys the seaweed’s inherent flavor, drawing out a deeper taste experience.
Furthermore, there is evidence suggesting an interaction between aroma and umami. The umami components in nori, such as free amino acids (like glutamic acid) and inosinic acid, may work synergistically with volatile compounds to enhance how the flavor is perceived. While this relationship hasn’t been fully quantified, research in sensory science underscores the close connection between smell and taste, highlighting the importance of aroma in the overall sushi experience.
Sushi chefs leverage this property, employing techniques to maximize aroma through nori selection, timing of toasting or searing, and careful storage management. Furthermore, they cut or roll the nori immediately before serving to diffuse its aroma into the air, directly appealing to the customer’s sense of smell. Thus, the aroma of nori is not merely a flavor; it is a crucial element that determines the overall quality of sushi, resulting from the combination of its chemical properties and the chef’s skill.
Fatty tuna and conger eel, along with squid and shrimp known for their sweetness, are sometimes served with salt instead of nikiri shoyu (soy sauce). A touch of grated yuzu zest or a few drops of kabosu juice are often added for their refreshing aroma.
It can be viewed from three angles: how chemistry shapes flavor, how technique refines timing, and how our senses perceive texture and aroma.
In sushi, using salt or citrus is not merely seasoning—it is a refined technique to balance umami, aroma, and texture delicately.
Salt enhances sushi’s flavor because it does more than just season. Taste receptors in the thousands of taste buds on the tongue’s surface are electrically stimulated by sodium ions from added salt, which send a “salty” signal to the brain. At the same time, sodium ions help glutamic and inosinic acids—the key umami compounds—bind more effectively to the receptors, amplifying the taste response. In other words, salt not only imparts saltiness but also heightens the sensitivity of umami receptors, enhancing the fish’s natural savory flavor.
Furthermore, salt gently draws out excess moisture from the surface of the fish through osmosis. This concentrates umami components such as free amino acids and nucleic acids, while reducing any fishy odor and sharpening the flavor profile.
A small amount of salt is also believed to stimulate saliva production, which helps counter the numbing effect of fat on the taste buds. As a result, flavor compounds reach the tongue more readily, making the sweetness and richness of the fat feel more distinct.
Citrus fruits, on the other hand, are rich in volatile aromatic compounds such as limonene. The refreshing scent that fills the nasal cavity when you chew conveys a sense of freshness. Meanwhile, acidic components like citric acid cut through the heaviness of the fat, leaving the palate clean and refreshed, and making the next piece even more enjoyable.
In essence, salt and citrus engage different senses—the tongue and the nose—not merely adding to sushi’s flavor, but bringing out the ingredients’ natural qualities and creating perfect harmony.
Traditional sushi restaurants never serve modern sushi.
Traditionally, nigiri sushi strives to perfect the taste, aroma, texture, and appearance of the fish in a single piece. Sushi chefs never layer different toppings on one piece, because combining the flavors, aromas, and richness of multiple fish makes it difficult to fully appreciate each fish’s natural flavor in a single bite. The texture of each topping, its balance with the shari, and the beauty of its color and precise cuts are all carefully considered to preserve the complete taste and visual harmony of a single topping.
That said, some sushi restaurants, aiming to showcase their unique style, may serve combinations that emphasize visual impact, such as squid topped with sea urchin, salmon roe, or caviar. Each piece of sushi is a complete dish in itself, and this act is somewhat like eating meat and fish dishes together. In such cases, the technique a sushi chef should employ involves harmonizing the natural flavors with salt and citrus to draw out the squid’s rich sweetness, while meticulously adjusting the knife work to alter the squid’s texture.
This is not to say that modern sushi is bad, as shown in the image at the beginning. Undoubtedly, layered flavors can create a lingering taste and rich depth. Even at traditional sushi restaurants, if regular customers request such modern sushi, it may be served, but in reality, few customers ever ask for it.
In Japan’s past, sushi was primarily known for its light and refreshing taste. Edo-period nigiri sushi centered on toppings like white-fleshed fish (such as hirame) or hikarimono (such as kohada) cured with vinegar or salt, where “freshness” and “clean, light flavors” were prized. Fatty fish spoiled easily and were not particularly favored among Edo diners.
However, as time progressed, food values underwent a significant shift. Advances in refrigeration and freezing technology made it possible to handle fatty fish while keeping them fresh, propelling toro, yellowtail, and salmon to become the stars of sushi. Toro, in particular, was once considered a “discarded part,” but is now celebrated worldwide as the “ultimate flavor.” To modern palates, fatty fish have a “melting richness” reminiscent of marbled beef, and this sensation fuels the popularity of fatty fish.
In recent years, fish such as blackthroat seaperch (nodoguro), splendid alfonsino (kinmedai), broadbanded thornyhead (kichiji), largehead hairtail (tachiuo), bigeyed greeneye (mehikari), and gnomefish (kuromutsu)—once rarely eaten by the public—have gained prominence as premium sushi toppings. These fish are often rich in fat and possess a deep umami flavor, embodying the “richness” and melt-in-the-mouth umami sought by modern palates.
Using fatty fish in sushi demands advanced craftsmanship. For fish like kinmedai and nodoguro, which have beautiful skin, special techniques are needed to highlight the skin’s beauty and the aromatic richness of the fat. Furthermore, to accentuate the natural sweetness in the fat, the temperature and acidity of the shari (vinegared rice), as well as the type of vinegar blend used, are subtly adjusted to balance the umami of the fat with the overall dish.
Through this accumulation of techniques, sushi chefs have refined their skill in “utilizing fat as umami.” Consequently, fatty fish have become not merely “rich ingredients,” but a canvas for the chef’s artistry and skill. Furthermore, modern taste preferences are underpinned by shifts in Japanese dietary habits. Increased consumption of fatty foods like meat and butter, coupled with palates accustomed to processed foods and chemical seasonings, now responds more strongly to rich, fatty, or salty flavors than to subtler tastes. This environment also fuels the growing preference for fatty fish.
Moreover, the influence of media and social networks heightens expectations of deliciousness even before tasting.
Thus, the fatty fish once shunned byEdo-period people now captivates as a “fish representing sushi.” This shift in taste can be seen as a uniquely modern symbol of affluence, born from technological progress and cultural sophistication.
Nigiri sushi is perfectly complete with just soy sauce and wasabi.
― From the Science of Taste, Culinary Techniques, and Cultural Background ―
Why do soy sauce and wasabi alone complete the flavor of sushi? It is because the umami and aroma of the seafood, the acidity of the vinegared rice, the chef’s skill, and the values of Japan’s unique food culture all unite, come together harmoniously in the mouth.
The umami components in seafood, such as glutamic acid, inosinic acid, and succinic acid, combine with the acetic acid in the vinegared rice and the amino acids in the soy sauce to create a deep flavor. Soy sauce integrates these umami flavors, and its fermented aromatic components (phenols and furanones) blend with the natural aroma of the seafood to add depth to the flavor. Salt tightens the flavor profile by assisting taste receptors, balancing the overall composition alongside the vinegar rice’s acidity.
Furthermore, the pungent compound allyl isothiocyanate in wasabi is also perceived as an aroma in the nasal cavity, uniting spiciness and fragrance to further enhance the multidimensional taste experience.
The unsaturated fatty acids (EPA and DHA) contained in fish fat oxidize slightly to produce volatile components such as hexanal, which are perceived as the “aroma of the sea.” These aromas are released most naturally at room or body temperature. The acidity of the vinegared rice melts in the mouth and enhances the aroma, bringing out the maximum umami of the fish topping and creating a scientifically sound harmony of flavors.
The artisan’s skill exists to further enhance this chemical interaction. They perform preparatory steps tailored to the freshness and condition of each topping, removing excess moisture and off-odor to highlight the ingredient’s inherent umami. Cutting techniques are also meticulously chosen for each topping—such as sogigiri (angled slicing), hikkikiri (pulling cut), or hirazukuri (flat slicing)—considering the fish’s fiber and fat distribution to adjust texture and aroma release.
The temperature and firmness of the shari (vinegared rice) are precisely calculated to ensure the fish’s fat melts perfectly in the mouth, creating the moment where aroma and umami unite. Wasabi is meticulously adjusted in quantity and placement for each piece to accentuate its fragrance and balance the mouthfeel. The combination of all these elements creates a single, complete taste experience in the mouth.
And cultural background underpins this harmony. This refers to a culinary philosophy that highlights the inherent appeal of ingredients by subtracting unnecessary elements rather than adding excessive flavors or aromas. For example, instead of drenching fatty white fish in strong sauce, it is designed so that the fish’s natural umami and aroma can be felt in a single bite, simply seasoned with the spiciness of wasabi and the saltiness of soy sauce. Whereas Western cuisine is often described as “additive cooking,” building flavor through layers of seasonings and sauces, sushi emphasizes the natural flavors of ingredients through subtraction.
The umami of the fish, the flavor of its fat, the acidity of the rice, and the aroma of the wasabi are calculated to harmonize naturally. In the early Edo period, wasabi was expensive and not something commoners could use daily. However, during the late Edo period, as “hayazushi” (sushi using vinegared rice to shorten fermentation time) became popular at street stalls, artisans noticed that wasabi’s spiciness and aroma enhanced the flavor of raw fish. They gradually began incorporating it into sushi. Thus, artisans continued refining their craft to complete each piece with minimal adjustments while respecting the individuality of the ingredients, establishing the philosophy of harmonious flavors in sushi.
Thus, sushi is perfectly complete with just soy sauce and wasabi. The fusion of scientific umami synergy, the artisan’s meticulous technique, and the cultural backdrop of the subtractive aesthetic allows one to experience the depth of flavor and the three-dimensionality of aroma in a single bite. Soy sauce and wasabi are not mere seasonings; they embody the essence of sushi.
The safety of sushi in Japan is not solely dependent on the meticulous daily hygiene practices of sushi chefs.
― Raw gastronomy supported by science and culture ―
Japanese sushi is recognized worldwide as “safe to eat raw.” In many countries, consuming raw fish carries risks. Bacteria, parasites, and inadequate temperature control can lead to food poisoning. However, a culture where sushi and sashimi can be enjoyed with confidence has been built over a long history in Japan. This is no accident; it is the result of scientific management and laws combined with artisans’ skills and cultural awareness. Let’s take a closer look.
Thorough freshness management via cold chain
When discussing the safety of Japanese sushi, the most crucial element is the low-temperature management system known as the “cold chain.” This refers to the mechanism that maintains a constant temperature throughout the entire process, from the fish being caught in the sea to its arrival at the sushi counter. First, the caught fish is immediately chilled with ice onboard the vessel and kept at a low temperature around 0°C. This minimizes bacterial growth and deterioration of freshness. Then, the fish is delivered by refrigerated trucks from the fishing port to the fish market.
Upon arrival at the fish market, the fish is kept at low temperatures in the auction halls and warehouses, maintaining its freshness until purchased by the chefs. Transportation from the market to the restaurants also uses dedicated refrigerated trucks or containers to maintain a constant temperature. At the restaurants, further management occurs in the sushi display cases and refrigerators, ensuring the quality of the fish remains at its absolute best.
Furthermore, fish like salmon, which carry a risk of parasites, undergo proper freezing during distribution, ensuring they are safe for raw consumption. This rigorous temperature control from catch to plate is what makes Japanese sushi a unique “safe raw food” unmatched anywhere else in the world.
Japan’s globally high food safety standards
One reason Japanese sushi is globally safe is its strict food safety standards based on laws and systems. Japan’s Food Sanitation Act thoroughly regulates the hygiene management of raw fish for consumption and cooking utensils. Furthermore, the HACCP (Hazard Analysis Critical Control Point) system is implemented in all food service establishments, analyzing hazards and clearly defining control points at each stage from fish reception and refrigerated storage to cooking and serving. For example, meticulous hygiene management is routinely practiced, covering details such as temperature control of sushi toppings, parasite risk management, maintaining hand cleanliness, and disinfecting knives and cutting boards.
Sushi restaurants also strictly adhere to these standards. Beyond simply complying with laws and regulations, hygiene awareness is thoroughly instilled during the training of their chefs. Maintaining hand cleanliness, disinfecting cooking utensils, and controlling the temperature of sushi toppings are daily routines across all sushi establishments.
Furthermore, regular on-site inspections are conducted by municipal health centers. These inspections verify temperature management records, kitchen cleanliness, and employee handwashing practices. Violations result in corrective guidance and, in some cases, suspension of operations. This combination of legal oversight and artisan traditions enables Japanese sushi restaurants to routinely achieve a level of hygiene management unparalleled anywhere else in the world.
According to the Tokyo Metropolitan Government Health and Medical Services Bureau, the number of food poisoning incidents in fiscal year 2025 was 114 cases (affecting 1,536 people). Compared to 76 cases (affecting 833 people) at general restaurants, sushi restaurants had only 8 cases (affecting 27 people), a very low number.
Sushi chefs’ rigorous sanitation practices
One of the most critical factors supporting the safety of Japanese sushi is the daily sanitation practices of sushi chefs. Chefs pay meticulous attention to sanitation, just as much as they do to their nigiri-making and knife skills.
Maintaining clean hands is the top priority. Chefs wash their hands between tasks and disinfect their fingertips with vinegar water. Cutting boards and knives are also wiped down and disinfected after each sushi. These practices prevent cross-contamination. Furthermore, during their apprenticeship, trainees are rigorously taught by their masters to visually inspect fish for anisakis parasites and remove them thoroughly.
Sushi toppings are always kept below 5°C (41°F) to minimize bacterial growth. Careful consideration is given to the chef’s workflow and tool placement. Areas for handling raw fish and cooked ingredients are separated, and dedicated tools are used to prevent cross-contamination.
Sushi chefs’ hygiene management is not merely a formality; it is a scientifically grounded “procedure for ensuring safety.” The chefs’ experience and skill are reflected in their daily hygiene practices, allowing us to enjoy raw sushi with confidence.
A culture that values freshness and eating food right away
One reason Japanese sushi is safe and delicious lies in its “freshness-first, eat-food-immediately culture.” This culinary tradition, passed down from the Edo period to the present day, is based on the premise of eating fish caught on the same day. At sushi restaurants, it is standard practice to prepare and serve fish purchased at the market that very day.
This culture maximizes the freshness of fish, rice, and seasonings while significantly reducing the risk of food poisoning.
Summary
It is the combination of tradition, science, the artisan’s skill, and a culture that values freshness that makes Japanese sushi so reliably safe to eat raw. The combination of a culture prioritizing freshness dating back to the Edo period, scientific temperature control and inspection, and artisans’ meticulous hygiene management achieves a level of safety unparalleled anywhere in the world.
This title might seem like a uniquely Japanese question. However, in neighboring countries like Korea and China, flounder (karai) and halibut (hirame) are also commonly eaten, and efforts are being made to cultivate them.
In many other countries, however, these fish are not distinguished and are often lumped together as “flatfish.”
One reason is the broad range of species covered by the English term “flounder.” For instance, many species like flounder, plaice, halibut, lemon sole, common dab, Pacific Dover sole, and fluke are all grouped under “karei.” Even the names alone can be confusing.
The common method to distinguish hirame and karei is the rule that when placed belly-side down (the white side), the hirame faces left and the karei faces right. However, there are exceptions like Numagarei (Starry flounder).
Species in the Pleuronectidae family, whose eyes are on the right side, are known as “righteye flounders,” while those in families such as Paralichthyidae and Bothidae, with eyes on the left, are called “lefteye flounders.”
Similarities and Differences Between Karei and Hirame
Both karei and hirame belong to the order Pleuronectiformes and share very similar shapes and colors. They both have flat bodies, are asymmetrical, and possess the unique characteristic of having both eyes on one side of their body.
What is Karei?
The Illustration of Karei
Flounder encompasses a vast number of species with a wide distribution range. In Japanese coastal waters alone, approximately 40 species have been identified, including Magarei (Yellow striped flounder), Meitagarei (Ridged-eye flounder), Ishigarei (Stone flounder), and Makogarei (Marbled flounder). The species caught also vary by region.
As they are relatively inactive fish, their flesh is characterized as soft and rich in fat. They feed on small fish, ragworms, and small crustaceans, resulting in a small mouth shaped like a “pursed mouth.” Additionally, their eyes are located on the right side of their body.
While fresh specimens can be eaten as sashimi, they generally have a slight distinctive flavor. Therefore, they are typically enjoyed cooked through methods like simmering, frying, deep-frying, or drying.
What is Hirame?
The Illustration of Hirame
Compared to karei, hirame has fewer species and a narrower distribution, making it relatively rare. Its scientific name is Paralichthys olivaceus, and it is a premium fish found in the coastal waters of Japan and Korea.
Hirame has well-developed muscles for agile movement, resulting in firm flesh. It has a large mouth and sharp teeth for catching small fish and crustaceans, and its eyes are located on the left side of its body.
When eaten raw, it has a crisp, firm texture that turns tender and flaky when cooked. It’s known for its mild flavor and delicate umami. It is popular as a premium ingredient for sushi and sashimi, and in French cuisine, it is also used in main dishes like meunière.
Its peak season runs from late autumn to early spring, with the winter variety, “Kanbirame,” boasting particularly rich fat content and exceptional flavor.
Conclusion
While karei and hirame may look similar, they have distinct differences in taste, texture, and ecology. In Japan, summer Makogarei (Marbled flounder) and winter Bastard halibut (Hirame) are considered premium fish, highly prized in sushi restaurants and traditional Japanese restaurants. Understanding these differences enhances the enjoyment of dining at sushi establishments.
When sauce is about to drip, do you catch it by cupping your hand like a plate with the hand opposite your chopsticks? This is commonly called “Tezara (手皿: Te means hand and zara means plate).” It often appears on Japanese TV during meal scenes.
While it might seem elegant, it’s actually considered bad manners in Japanese dining etiquette, so it’s best to remember this. You should be especially careful during important occasions. The basic etiquette for Japanese cuisine is to hold the bowl or dish in your hand while eating, so the correct way is to use the sauce in a small side dish, not your hand.
However, there are times when small side dishes aren’t provided, like when eating out or at home. In those cases, the basic Japanese approach is to hold the bowl itself close to your mouth for dishes with sauce. Alternatively, you can use techniques like lightly cutting the sauce with the tips of your chopsticks before bringing it to your mouth to eat neatly without using your hands.
Why is using your hand as a plate considered bad manners? If sauce drips onto your hand and stains it, you’ll need to wipe your hands with an oshibori (wet towel), creating extra laundry. Oshibori are meant for wiping hands before eating. If they get stained with food sauce, they may require stain removal, causing trouble for the restaurant.
Furthermore, while it’s common, seeing someone use their palm as a plate and then bring the food to their mouth can feel somewhat unhygienic and vulgar, even if the person themselves doesn’t mind. Depending on the situation, it’s considered bad manners during a proper meal.
In Japan, holding bowls and small dishes is considered polite.
In Japanese dining culture, holding bowls and small dishes is considered polite. Proper etiquette dictates lifting bowls and soup bowls to your mouth, while flat or large dishes should not be lifted—specific manners exist for each type of vessel. Using a serving dish instead of tezara is rooted in these uniquely Japanese dining customs.
Of course, during casual meals at home or with friends, you might unconsciously use your hand as a plate. While it often isn’t a major issue in daily life, it’s especially important to refrain from doing so at formal occasions, kaiseki dinners, or when dining with seniors. Being mindful of etiquette according to the situation will make your dining manners appear more refined.
It’s a gesture that anyone can easily do, but it’s best to avoid it at formal occasions. It may even look as if you’re drawing attention to a spill, so using a side plate or small dish is always the better choice.
Vegetables, fish, and meat each have their own “peak season” when they taste their absolute best.
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.
An illustration of cross section
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.
An illustration of kuromaguro cutting daigram
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.
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.
