I’ve recently gotten into cooking and making meals, and I quite like sushi, so it’d be nice to know what exactly distinguishes the two from each other. I’m not asking how do I get sushi grade fish, I will only eat raw it if I’m informed the fish is Sushi Grade. I’m more asking how the science, biology, chemistry, etc. behind it works, and how Sushi Grade fish is procured and produced in comparison to normal fish.
In: Biology
The main risk of fresh fish is parasites. If fresh fish is frozen immediately, it won’t develop any bacteria and if it is frozen deeply (-20C for several days or -35C for several hours) it will kill any parasites.
So sushi grade fish is typically caught, cleaned and flash frozen almost immediately then stored at a very cold temperature for a period of time.
Sushi is made from salt water fish (ocean fish) vs fresh water fish (river or lake fish). Ocean fish naturally has less parasites and bacterial content so it’s safer to eat raw. Fresh water fish needs to be cooked.
Fish like Tuna is fresh caught, bled immediately, and chilled to make it safe to eat. Tuna and other fish shipped to North America is packed in ice for the trip.
Many other fish like Salmon which are more prone to parasites are flash frozen to kill any parasites while retaining it’s texture and taste when thawed.
The simple answer is that the fish isn’t necessarily *raw* it’s flash frozen to kill anything bad for you.
Sushi/poké chef here, in the US the FDA recommends 7 days of freezing to kill any potential parasites or viruses. At my restaurant, I cure the Salmon by salting it and then rinsing the fish then put it in the freezers. It’s almost the same as like starting to ferment jerky with salt. Anyways that helps kill any other parasites and helps maintain the fish. With ahi Tuna, we receive the fish skin on with only the loins. We just clean them off with water and place in freezer. Hamachi (Yellowtail) we do the same as ahi tuna. PSA: Hamachi is known as yellowtail but it isn’t the same as yellowfin. Which is known as ahi tuna
If you’re in the US, absolutely nothing.
[There are no regulations whatsoever on the use of the term “sushi grade” in the US.](https://www.pbs.org/food/fresh-tastes/myth-sushi-grade/)
Your supermarket could call a defrosted Gorton’s fish stick “sushi grade” if they wanted to.
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