Understanding Sushi Grade Fish
The terms "sushi grade" and "sashimi grade" indicate that the fish is safe for raw consumption. There is no difference between these two labels; they both signify the same standard. For the sake of consistency, I’ll use "sushi grade" henceforth.
In the United States, "sushi grade" is not an officially recognized term by the FDA or any other governmental entity. Rather, it's a commercial term. That is to say, the vendor selling the fish determines its sushi grade status. If the fisherman or the fishmonger deems the salmon safe for raw consumption, for instance, they label it as sushi grade.
To buy fish for sushi, look for labels reading "sushi" or "sashimi," such as "Sushi Tuna" or "Sashimi Salmon." If these words are absent, ask the vendor if the fish is sushi grade. If their answer is yes, the fish should be safe for raw consumption. If they say no or seem unsure, it's better not to risk it.
So, how do they determine whether a fish is sushi grade? It's often based on a visual inspection of the fish, along with adherence to specific criteria. The process is complex because it involves more than visual inspection. However, I'll attempt to simplify it.
Unless you're a professional fishmonger or sushi chef, these are the best steps to follow. This is because determining sushi grade quality requires specific knowledge and experience, not unlike learning how to play baseball by merely reading a book about it.
What are the criteria for sushi grade fish? This varies widely and can be challenging to define due to several reasons:
There are numerous types of fish.
Each fish carries a different number and type of bacteria and parasites.
The number of bacteria that will make humans sick is determined by how the fish is stored (temperature and time.)
The third point is particularly complex because another critical factor comes into play: you, the consumer.
The risk of becoming sick from eating raw fish (or bacteria from raw fish rather) is largely dependent on your immune system. For instance, while I might tolerate eating raw tuna just fine, you might not due to differences in our immune defenses. This concept is similar to how some people become severely sick from COVID-19, while others experience mild symptoms. Although it would be beneficial for regulatory bodies like the FDA to establish general guidelines on bacteria thresholds that could induce sickness when "bad" fish is consumed, this is likely a complex task.
Japan, however, has implemented a health law for sushi grade fish that stipulates the acceptable level of bacteria. According to this law, fish sold as sushi grade at supermarkets must have a bacterial count of less than 1,000,000 (notated as 10^5). What does this mean for us? Unfortunately, without a device to test for bacterial content, neither you nor your supermarket can determine the exact bacterial count in your fish. Simply put, a bacterial level exceeding 10^5 typically indicates the fish has been left at room temperature for a prolonged period, or it has been handled on unclean surfaces. (Note: I am aware that “prolonged period” doesn’t exactly specify how many hours and minutes. This is the dilemma everyone faces when determining exactly what sushi grade fish is.)
Here is the law set by Osaka prefecture in Japan:
Brio parahaemolyticus is less than 100 per gram.
The water used for processing must be water for food manufacturing, sterilized seawater, or artificial seawater using water for food manufacturing.
Seafood must be fresh.
If the fresh fish and shellfish used as raw materials are frozen, they should be thawed in a sanitary place, or thawed in a clean water tank using water for food manufacturing, sterilized seawater, or artificial seawater using water for food manufacturing. It must be done while using and changing water sufficiently.
Fresh fish and shellfish used as raw materials shall be thoroughly washed with food manufacturing water, sterilized seawater, or artificial seawater using food manufacturing water to remove substances that may contaminate the product.
It's important to note that in the United States, the FDA provides guidelines, not laws, for eating raw fish. Despite common claims in articles, online posts, and comments suggesting that "all sushi fish must be frozen in the U.S.," this is not strictly accurate, according to my current research. It is now a law. It is a guideline. Regulations seem to be largely determined at the state level, and New York appears to be the only state that has adopted the FDA's guidelines into law as of this writing.
If you are interested in learning more detailed information, you can review the specifics on the FDA’s website. Be prepared, as the guidelines are not written in everyday language and can be complex. In a nutshell, the guidelines suggest that most fish types, excluding Tuna, should be frozen prior to consumption.
The FDA's guidelines also specify a range of acceptable periods of time during which fish can be stored at temperatures higher than refrigeration. However, the general rule remains that the colder you keep your fish, the longer it stays fresh and safe to eat. (Source: serious eats)
What Qualifies a Fish as Sushi Grade?
Once a fish is determined to be fresh, its qualification as "sushi grade" depends on the following criteria:
1. Species of Fish
Certain species are safe to consume raw, while others are not. For example, Yellowfin Tuna, Bigeye Tuna, and Bluefin Tuna are typically safe to consume raw. On the other hand, Wild Salmon is generally not recommended for raw consumption (details on Salmon to follow in the next section). Similarly, Spot Prawns, also known as Ama Ebi, can be consumed raw, but white shrimp from the Gulf of Mexico should not be. Cod is generally not eaten raw due to the high risk of bacterial infection, even after freezing the fish. Serious eats sites “particularly Atlantic cod, but also Pacific cod, haddock, and pollack—since they're highly susceptible to infection by a range of parasites.” I also read raw Cod is simply not tasty (also noted in the Serious eats article).
2. Frozen or Cured (Treated)
Wild salmon is not typically suitable for raw consumption due to the potential presence of parasites like anisakis, tapeworms and certain bacteria. To eliminate these parasites, the salmon needs to be properly frozen. This process gets technical, so for simplicity's sake, it can be stated that the fish needs to be frozen in a commercial freezer for at least 24 hours. In a home setting, it requires freezing for 7 days to effectively kill the parasites. (You can visit the US FDA page for a more in-depth understanding.) You can see the Salmon curing technique in the recipe section.
So, when you encounter Sashimi Salmon at a supermarket or sushi restaurant, it's highly likely that the salmon was previously frozen and then thawed.
An exception to this rule is certain types of farm-raised salmon that are parasite-free and therefore do not require freezing for safe raw consumption. Details regarding which types of salmon fall into this category can be obtained from the fishmonger or the salmon farm. Ora King Salmon, for instance, is a farm-raised salmon that is sushi-grade without the need for freezing.
Most Saba/Mackerel is not suitable for raw consumption, and simply freezing it does not make it sushi-grade. It must undergo a curing process, known as "Shime" in Japanese. This involves salting it for about two hours and then soaking it in vinegar for approximately 15-30 minutes, after which it becomes safe for raw consumption. Wild Saba also has higher chance of having parasite, anisakis that can cause you severe stomach pain when consumed. Since curing in salt and vinegar does not kill anisakis, it is recommended to freeze Saba if you want to be 100% parasite free.
However, there are rare types of Saba that can be consumed raw, caught in specific regions of Japan, during certain times of the year. Seki Saba, also known as Golden Saba, is one such variety. They need to be extremely fresh, preferably less than 8 hours old.
3. Toxin Presence
Unagi/Freshwater eel, is not fit for raw consumption due to the presence of a toxin in its blood that can be harmful to humans. Consequently, Unagi is always served cooked to neutralize this toxin.
Similarly, you may have heard about the potential dangers associated with Fugu, or blowfish. However, it's not the entire fish that poses a threat. Instead, specific parts such as the liver and skin contain the poisonous substance. Therefore, Fugu should not be consumed, whether raw or cooked, unless these toxic parts are expertly and safely removed by a certified individual. In Japan, a government-issued certification is required to fillet and serve Fugu, ensuring safety for consumers. When the toxins are removed, fugu can be served both raw and cooked.
Another one is starfish, which contains poison in some parts of the fish. I never tasted it and I understand its egg tastes similar to Uni, Sea Urchin.
Please note, these are general guidelines and it's important to always consult with a knowledgeable source or professional when selecting fish for raw consumption.
Q: Does freezing kill bacteria?
Freezing to below -17.7 °C (0˚F) inactivates any microbes, bacteria, yeasts and molds present in food. Once thawed, however, these microbes can again become active, multiplying under the right conditions to levels that can lead to foodborne illness. Since they will then grow at about the same rate as microorganisms on fresh food, you must handle thawed items as you would any perishable food. (from: Does freezing food kill bacteria? Ask USDA)
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