Like any premium product, fresh tuna is priced based on how it is graded. This is especially true for tuna headed to the sushi kitchens of the world, where appearance and taste are scrutinized with every bite.
Each tuna can earn one of four grades: #1 (highest), #2+, #2, and #3. While this grading is highly subjective, over time a system has evolved to help guide fair pricing. Like the 3 C's in diamond, each fish is graded based on five indicators:
- Initial appearance
- Size and shape
- Fat content
Initial appearance (freshness) is where the grading process starts. Most tuna is traded headless, and one of the most apparent signs of freshness is the collar, where the head has been removed. Then the fish’s skin, scales, and fins are visually inspected. Once the outside is evaluated, then the inspector looks inside, at the belly wall, to grade based on what is visible from the cut made to gut the fish
Size and shape – The size of a fish and its marketable yield are directly proportional. Larger fish produce larger loins and fatty portions, which increases their value.
Color - Tuna’s meat is generally red but the specific level of redness determines the grade. The tail color (from where the tail is cut off) is a good indicator of the condition of the fish since that area tends to change color first. The color of the core sample and the bloodline are also good indicators of health and general quality.
Texture is best determined by physically feeling the core sample and the tail cut. The stickiness or pastiness of the core sample and the smoothness of the cut of meat are good indicators to determine tuna’s grade
Fat – A tuna’s grade depends also on its fat content. The best places to determine fat content are the core sample, belly wall, tail cut and the nape (collar).
These five indicators are in general what gives each fish its individual grade. More specifically:
Grade #1 Tuna - The highest grade of tuna. Sometimes called sushi grade or sashimi grade. In order to be graded #1, a tuna must exhibit all #1 quality of all five indicators
- The collar where the head has been removed should be clean with no discoloration.
- The skin should be clean as well without any puncture, scratch, or damages.
- Specific color differs by species but in general, a tuna’s original exterior color should be a reflective, metallic black. The scales should be intact as well.
- The belly should be clean and intact. Damaged or stained belly indicates spoiled meat. The color should be pink.
- Tuna should be firm to the touch.
Size and Shape
- #1 Tuna should be at least 60 pounds or larger since heavier fish have a more desirable loin size and fat content.
- The shape should be fat and round with a thick belly.
- #1 grade tuna should have bright red, shiny and translucent. The core and tail sample should have this color.
- The bloodline from the samples should be darker red than the meat. It should not be black or brown.
- There should not be any discoloration or brown under the skin where the fat is located.
- #1 grade tuna should have a fine and smooth texture, not coarse or grainy.
- The core sample should be clear and the fat should be felt when rubbing it between your thumb and index finger.
- The core sample should be sticky to the touch.
Fat - Bluefins and some Bigeyes are known for their fat content. Yellowfin are a much leaner fish with normally little to no fat.
- Fish with high fat content are generally regarded as more valuable and are priced higher.
- A thick belly is usually an indicator of high fat content.
- Fat content should be visible at the nape where the head has been removed.
- The presence of fat in the tail cut, just below the skin is essential in grading.
- The fat is visible in the meat like the “marbling” seen in beef.
Grade #2+ Tuna - The next grade of tuna following #1 grade. This grade is relatively new in US markets and has only been used since the 1980’s. The disparity between #1 and #2 was great so this median grade was created.
- Grade #2+ tuna might be close to Grade #1 tuna in skin color.
- The nape and the belly might be slightly flatter and not as bright.
- The outside should be clean, but with some small scarring and wounds acceptable. The scars should not be severe to affect the fish’s quality.
- A few imperfections on the scales and skin.
- Fins should not be broken.
Size and shape
- The size and shape should resemble #1.
- Grade #2+ may be smaller than 60 pounds.
- The shape may be less perfect than #1, but should not inferior. This fish is usually longer and thinner as opposed to fatter and stockier as in #1 grade.
- The tail cut is red but may be slightly discolored near the skin.
- Color is the most important factor when determining a Grade #2+ fish. The core sample should be red with less clarity than Grade #1.
- The loin cut is slightly less bright than Grade #1.
- Less consistency in color throughout the loin.
- Evidence of fading color from the top of the loin to the bottom near the skin may be seen.
- #2+ has less fat so the texture feels less sticky and leaner.
- It should still feel wet and smooth as in Grade #1.
- It should still have good and solid feel to the touch.
Grade #2 Tuna – This is the tuna of choice of many restaurants who don’t want to pay Grade #1 money for tuna dishes that will be cooked. Although not really considered sushi grade, some low-end restaurants may use it raw.
Grade #3 Tuna – This is a cooking grade, and the color has already turned brown or greenish.