What Is Sashimi or Sushi Grade Fish? The Detailed Guide.

The terms “sushi-grade” or “sashimi-grade” are commonly used to refer to fish or seafood suitable for raw consumption. While the designation may appear authoritative, it is currently neither defined nor standardized. It is more of a widely accepted marketing term used to assist customers in selecting specific ingredients or to promote the sale of certain fishery products.

Consequently, many commercially available fish or seafood are suitable for the preparation of sushi or sashimi, provided they meet certain quality and safety criteria. In many countries, exact guidelines and standards are established regarding these requirements. These regulations dictate how fish or seafood must be handled if intended for raw consumption by consumers. Specifically, these rules typically address the maintenance of the necessary cold chain, hygiene, and the targeted elimination of parasites potentially harmful to humans. The preparation of sushi or sashimi is only one of many possible raw dishes. Therefore, the relevant regulations focus on food safety rather than qualitative (organoleptic) characteristics such as taste, appearance, smell, and color. Nevertheless, these characteristics, along with freshness and safety, play a central role in the selection of ingredients for the preparation of sushi and sashimi.

The following sections will explain the fundamental requirements for the general definition of sushi- or sashimi-grade. Since sushi has long become a global culinary phenomenon, consumers often encounter this terminology at the fishmonger’s counter, in supermarkets, or in various online retail shops. It is important to note that the term sushi- or sashimi-grade generally describes suitability in terms of food law, rather than “quality” in a specific sense. The quality range of suitable and “safe” ingredients thus spans from affordable mass-market products to high-priced premium items.

As is well known, taste is subjective, but quality is not. For an optimal taste experience when consuming sushi or sashimi, the raw ingredients should therefore be of very high quality. Exceptions are fish that have been aged to enhance flavor. During the aging process, their objective quality characteristics may deteriorate, but the taste intensifies correspondingly.

Regardless of whether you prefer fatty fish like salmon or lean fish like sea bass, the better the quality, the tastier the final dish. Therefore, from the consumer’s perspective, it is important to distinguish between high-quality and lesser-quality raw ingredients. The origin and seasonality are also crucial, especially for wild-caught species. Climatic influences and spawning times significantly impact general physiology and fat content, thus directly affecting the taste.^{[2] [3]} The price is not necessarily an indicator of quality or good taste. However, it is often observed that quality and good taste come with a higher price. Experience shows that farmed fish from high-quality aquaculture facilities are superior in taste to those from ordinary aquaculture, especially when intended for sushi or sashimi. Products from facilities that focus on low stocking density, gentle handling, feed composition, and special slaughter methods (e.g., ike-jime) have a distinct advantage.

Most wild fish species available in the broader market predominantly come from commercial or industrial fishing. The possible fishing methods range from rod and line to kilometer-long trawl nets. Fundamentally, any fishing method can be used to offer fish in sushi- or sashimi-grade quality. However, the fishing method can indeed be responsible for the difference between top and standard quality.^[4] The more desirable a species is, the more likely it is that the fishing methods will be differentiated with regard to quality, as in the case of tuna.

The freshness of fish and seafood is crucial when preparing sushi and sashimi. In the context of food, ‘freshness’ refers to a state in which the original properties of an ingredient are largely preserved.^[5] This is particularly important for dishes like sushi and sashimi, which rely on the quality and integrity of raw marine products. Fish and seafood are exceptionally perishable compared to other foods and therefore require special care in their handling. After the death of fish or seafood, proteins and fats are broken down by enzymes, leading to changes in texture and flavor. Simultaneously, bacterial growth accelerates, posing health risks when consumed raw.

To preserve freshness, fish for sushi or sashimi is rapidly chilled immediately after being caught and then stored at precisely controlled temperatures just above the freezing point. This slows bacterial growth without forming ice crystals that could damage the delicate flesh. Spoilage thus serves as an indicator of undesirable changes after catch or slaughter, directly impacting the quality and safety of the final product.

For certain species, particularly tuna (maguro), bastard halibut (hirame), and mackerel (saba), controlled aging can be used to enhance flavor and texture.^[6] This process is carefully monitored and always begins with fresh fish. Aging breaks down specific compounds, resulting in a more complex flavor profile and tender texture. However, it requires expertise to prevent spoilage. Even for ingredients requiring some aging, high initial freshness is crucial for optimal flavor development and safe consumption.

The chef’s ability to assess and maintain the freshness of ingredients for sushi and sashimi is crucial. This involves not only proper storage and handling but also the skill to evaluate ingredients based on sensory characteristics such as smell, color, and firmness.

Raw fish and seafood are considered particularly sensitive foods from a microbiological and hygienic perspective. The spoilage process is triggered by the action of enzymes, bacteria, and chemical reactions. Therefore, the longer the time since death, the more advanced the growth of potential pathogens. When using raw ingredients, a certain baseline level of microbial contamination should be assumed. Processing and preparation are expected to further increase this microbial load. This underscores the importance of freshness and the quality of the initial product, as sushi or sashimi is typically consumed raw, without prior (germicidal) heating.

The spoilage process typically involves changes in the physical properties of the raw material. These changes result in a deterioration of food quality, such as color, texture, and taste. While both freezing and cooling extend the shelf life of food, the objective quality of the food continues to decline regardless of the preservation method.^[7] Therefore, fish and seafood should be as fresh as possible, whether they are processed into sushi or sashimi or stored.

In everyday life, the term “freshness” is occasionally applied to indicate the recentness of the catch of fish. This is usually interpreted to mean that the product has not been and is not frozen. However, freezing fish or seafood does not diminish freshness, but rather helps to preserve it. It is important to note that while freezing extends the shelf life of food, it inevitably leads to a deterioration in food quality.^[7] The quality loss is significantly influenced by the freezing technology used.

Properly and industrially frozen fish or seafood, unlike catch-fresh products, have the advantage of significantly longer storage times. Freezing is one of the most effective forms of food preservation. Pathogens that cause food spoilage are deactivated at sufficiently low temperatures (starting at -18 °C). The use of industrial flash freezing minimizes the deterioration of food quality.^[8] Fish or seafood preserved by flash freezing immediately after catch thus provide adequate and qualitatively satisfactory ingredients for the preparation of sushi or sashimi.

The quality of frozen foods is often perceived to be inferior to that of “fresh products”, which are typically defined as items that have been recently caught or harvested. From an organoleptic point of view, fresh products that are properly chilled and consumed promptly are not significantly inferior and even have advantages in terms of handling. Frozen foods often have a reputation for being inferior to fresh products, primarily due to differences in texture, flavor, and appearance that can occur during the freezing and thawing process. From an organoleptic perspective, which involves the sensory evaluation of food (including taste, sight, smell, and texture), fresh products that are properly chilled and consumed promptly tend to maintain their original quality better than their frozen counterparts.

Freezing, especially slow freezing, can negatively alter the textural properties of products. However, flash freezing better preserves these properties, making the differences compared to fresh products very small or sometimes imperceptible. The very short freezing process in flash freezing forms only very small ice crystals in the cell fluid, keeping the cell structures intact. The degree of cellular damage is directly related to food quality in terms of taste, texture, nutritional value, and appearance.^[9] Modern methods enable the preservation of fish and seafood without significantly deteriorating their sensory properties or nutritional value. They serve as a convenient alternative to recently caught or harvested products when such ingredients are unavailable or impractical to utilize.

Strict hygiene measures are of paramount importance in the preparation of sushi and sashimi to ensure both the safety and quality of the dishes.^[10] The process begins with the careful selection of fresh and high-quality ingredients, with particular attention to the freshness and origin of fish and seafood. Maintaining an unbroken cold chain from procurement to processing is essential to prevent bacterial growth. Before and continuously during preparation, work surfaces, utensils, and hands must be thoroughly cleaned to minimize the risk of cross-contamination. Although the use of disposable gloves can be advantageous, it does not replace the need for regular handwashing. Specifically, the preparation of nigiri sushi proves ineffective with gloves, as the delicate manipulation and necessary pressure for shaping require direct contact. Additionally, touching kitchen areas with contaminated gloves can result in even more severe cross-contamination. It is also resource-intensive to change gloves with every contamination, and their reuse can lead to even more unhygienic conditions.

Proper storage of ingredients at appropriate temperatures is essential to prevent the growth of bacteria and the formation of toxins. The separate storage of raw fish and other foods is crucial to prevent cross-contamination, where bacteria or viruses can be transferred from one food item to another.

For professional processors and restaurants, implementing the HACCP system (Hazard Analysis and Critical Control Points) is crucial. The specific challenges in preparing and storing sushi, such as handling raw fish and preventing cross-contamination, require comprehensive risk analysis and control. The seven basic principles of the HACCP system allow for identifying and monitoring critical control points – from procuring ingredients to preparation and presentation. Implementing and complying with HACCP when handling ingredients is essential to ensure the highest standards of food safety and quality in sushi preparation. This includes measures such as temperature control of raw ingredients, preventing cross-contamination, and ensuring hygienic work practices. Furthermore, regular training of personnel on proper food handling and processing, as well as adapting HACCP plans to new procedures, are integral parts of these efforts.

When consuming fresh, previously unfrozen fish or seafood raw, there is a risk that they may be contaminated with viable parasites that can be harmful to humans.^[11] This is especially problematic for fish or seafood caught in the wild, as assessing the potential for parasitic infection is more challenging.

These parasites pose a significant challenge to the safety and quality of seafood, especially in the preparation of sushi and sashimi. Among the various parasites that can occur in fish and seafood, Anisakis simplex is one of the most relevant and concerning. A. simplex is a nematode parasite found in certain fish species, and it can cause anisakiasis in humans who consume infected raw or inadequately cooked fish. This parasitic infection can lead to symptoms such as nausea, vomiting, and abdominal pain.

Preventing infection by parasites requires careful preventive measures, including selecting fish from safe sources, proper processing, and specific methods to eliminate any parasites before preparing the fish for consumption.

It must be ensured, especially for raw consumption, that no viable parasites are present in the meat. For example, determining parasite infestation by illuminating fillets is only partially effective. This method only detects parasites immediately under the surface, and can thus only provide information about a fraction of the total burden.^[12] Epidemiological data from the source fishing areas can provide insight into the risk of possible parasite infestation, but are not an absolute guarantee for the absence of parasites in wild fish.^[13][14] According to regulation EC 1276/2011 ^[15] of the European Union, the following core temperatures and storage conditions must be met to kill nematodes; otherwise, fish or seafood is not approved for raw consumption unless there are exceptional conditions.

• Freeze at min. −20 °C until solid. Store at min. −20 °C for 24 hours; or
• Freeze at min. −35 °C until solid. Store at min. −35 °C for 15 hours.

The regulations of the US Food and Drug Administration (FDA) go even further and prescribe:^[16]

• Freeze at min. −20 °C until solid. Store at min. −20 °C for 7 days; or
• Freeze at min. −35 °C until solid. Store at min. −35 °C for 15 hours; or
• Freeze at min. −35 °C until solid. Store at min. −20 °C for 24 hours

Most household appliances are not capable of maintaining a continuous temperature of at least -20 °C. Additionally, the study by Podolska et al. (2019) shows that the speed of the freezing process should be considered, and extended storage times should be taken into account.^[17] The study by Sanchez-Alonso et al. (2018) suggests that domestic freezers, which operate with low cooling capacity and uneven temperature distribution, may not reliably ensure the complete inactivation of Anisakis larvae. This presents a potential health risk.^[18]

If fish or seafood come from aquaculture, the mandatory freezing treatment for raw consumption according to EU regulation can be waived under certain conditions. For safe consumption, the following conditions must be met according to this EU regulation:^[15]

• Use only animals reared from embryos
• Feed Free of Viable Parasites
• The animals must be raised in an environment that is epidemiologically proven to be free of parasites.

However, if the aquaculture operation uses officially approved procedures that ensure that no viable parasites are present in the products and therefore pose no risk to health, this obligation can be waived.

Farmed fish and seafood raised in land-based tanks or closed recirculating systems and fed with suitable feed are considered relatively safe regarding the presence of parasites that pose a health risk. This is contingent upon the condition that the farmed animals are raised from embryos and not taken from the wild, and that the water supply is demonstrably free of parasites.

The European Commission indicates that the parasite-killing freezing treatment of wild-caught fish can be waived if epidemiological data suggest that the fishing grounds of origin do not pose a health risk regarding the presence of parasites, and the competent authority approves this. However, the European Food Safety Authority (EFSA) considers that, based on current knowledge, no marine fishing grounds are known to be free of Anisakis larvae.^[15][19]

The U.S. Food and Drug Administration (FDA) maintains a list of species with a high risk of infestation by parasites harmful to humans but also recommends an individual assessment of the situation regarding raw consumption for species with a lower risk.^[16]

According to the European Food Safety Authority (EFSA), the likelihood of parasitic infection in farmed Atlantic salmon (Salmo salar) raised in floating cages (marine aquaculture) is considered low. Apart from Atlantic salmon, there is insufficient surveillance data for other farmed species. Therefore, it is not possible to identify additional fish or seafood species from marine aquaculture that pose no health risk concerning the presence of parasites.^[14][20]

In international comparison, particularly with regulations in the USA and Europe, Japan is characterized by a less restrictive approach to the consumption of raw fish. While strict guidelines exist in the USA and Europe that dictate the conditions under which fish for raw consumption must first be frozen to eliminate parasites like A. simplex, Japan adopts a more flexible approach. This approach relies both on recommendations and the expertise and diligence of the chefs.

The Japanese Ministry of Agriculture, Forestry and Fisheries and the Ministry of Health, Labor provide detailed recommendations for handling fish intended for raw consumption. These recommendations include adequately cooling, transporting, and gutting freshly purchased fish immediately. The need to quickly remove the internal organs is based on the fact that Anisakis spp. larvae mainly parasitize the surface of the organs. With decreasing freshness and progressing time, these parasites can, however, migrate into the musculature, the edible parts of the fish. Furthermore, it is recommended to consume fresh seafood that has been sufficiently frozen (at least 24 hours at –20 °C or 48 hours at –18 °C). For business operators, the Japanese Ministry of Health, Labor and Welfare provides clear instructions: The fish should be as fresh as possible and gutted immediately. The consumption of raw fish entrails should be avoided. A visual inspection and removal of Anisakis larvae is essential and is recommended, as is freezing the fish (at least 24 hours at –20 °C) or heating it (1 minute at 70 °C or higher).

The Japan Fisheries Association emphasizes that the only method to completely avoid anisakiasis is freezing or heating the fish. However, there is a discussion among professionals who emphasize that careful inspection of each fish can prevent anisakiasis.^[21] At the same time, this view underscores the high importance that Japanese gastronomy places on the freshness and quality of sushi and sashimi. It reflects a preference for using the expertise and judgment of chefs to ensure the safety of the consumed fish. However, this approach is not entirely free of criticism, as it relies heavily on the individual skills and diligence of chefs. Critics argue that this could lead to inconsistent safety standards and increase the risk of anisakiasis, as not all chefs can reliably identify and remove parasites.^[22][23] The prevalence of anisakiasis is closely linked to the tradition of consuming lightly cooked or raw fish or seafood, such as sushi and sashimi.^[24] Despite efforts to prevent parasitic infections such as anisakiasis by freezing raw fish, the disease is still prevalent in Japan and other regions with high consumption of raw fish dishes, albeit with low prevalence.^[25]

Japan's approach to raw fish consumption is based on a combination of government recommendations, expertise, and practical skills of the preparers. While strict regulations are preferred in other regions such as the USA and Europe, Japan emphasizes the importance of training and experience in handling and preparing raw fish. Nevertheless, it should be reassuring to note that trained and professionally educated chefs have a very low risk of infection. Their comprehensive training and experience enable them to effectively identify and minimize potential risks, ensuring the safety of the consumed fish. However, a very slight residual risk cannot be completely ruled out.

Not all fish species are used untreated for making sushi or sashimi. For example, mackerel, Pacific herring, or young sea bream are marinated in a sour solution of salt, vinegar, soy sauce, or other ingredients. A popular Japanese method is marinating in a vinegar solution. The Japanese word for this process, 'su-jime', refers to a procedure where raw fish is sprinkled with salt, rinsed, and soaked in vinegar. First, the salt draws water from the surface of the fish through osmotic pressure and firms the protein in the fish muscle. Subsequently, the vinegar also acts on the protein and hardens it, while small bones soften. This process makes the fish firmer, imparts the flavor of salt and vinegar, and retains moisture. A popular sushi or sashimi ingredient made by this method is shime saba. Marinating produces a certain antibacterial effect, but has little impact on potentially present parasites. Although some cooking or sushi literature may encourage killing parasites by marinating, studies show that traditional marinades are ineffective and thus not an adequate alternative to freezing treatment.^[26][27] An exception is the traditional German or Danish method of marinating herring fillets. However, this method requires a storage time of at least 5 to 6 weeks in an 8-9% salt solution to ensure that all parasites are killed.^[28] To reliably kill parasites using a salt and vinegar solution in a short time, the pH value would need to be so low that the meat would be nearly inedible.

Fish and seafood for sushi or sashimi must be fresh and meet the appropriate standards. Wild-caught marine and freshwater organisms can contain viable parasites that pose a risk to human health. In addition to diagnostic laboratory methods, inspection and visual examination during filleting are common methods for detecting parasite infestation. However, these visual methods are less reliable for large species or unprocessed fish and seafood, and they depend heavily on the expertise of the inspector or chef. Therefore, wild-caught fish without proper freezing treatment are rarely safe raw ingredients for sushi or sashimi. Despite traditional preferences, to ensure food safety, wild-caught fish should be industrially flash-frozen.

Freezing treatment can be waived if it is unequivocally ensured that the ingredient is free from parasites. Farmed fish and seafood can be processed fresh into sushi or sashimi. If non-flash-frozen wild fish is used, it should be left only to experienced chefs who can thoroughly inspect it for parasites. Nonetheless, there is a slightly increased risk of parasite infestation compared to flash-frozen products. Consumers should be aware of this risk and decide whether they are willing to accept this minimal risk for authentic taste. Those who want to be absolutely safe should choose flash-frozen products, where viable parasites are virtually eliminated.

In addition to safety, the freshness, and quality of the ingredients play a crucial role. Fresh and properly stored ingredients ensure a better taste experience and higher food quality. Factors such as fishing methods, farming conditions, timely cooling, and proper storage ensure that the raw ingredients are both safe and of excellent taste. The combination of freshness, quality, and safe handling makes the enjoyment of sushi and sashimi a safe and high-quality culinary experience. In this sense: Itadakimasu!