Why Sashimi Comes in White, Red and Blue-Backed, and What Each Colour Tells You

The colour of the flesh is set by how that fish swims. Flounder, rockfish and sea bream stay near the bottom and twist their bodies only in the instant prey passes, so they run mostly on white muscle built for short bursts, which leaves the flesh pale and low in fat. Species like tuna, yellowtail and salmon work the other way: they cover long distances without resting, so their muscle carries a great deal of the pigment that stores oxygen, which turns the flesh red, and they stock fat between the muscle fibres as the fuel for staying in motion. Mackerel, gizzard shad and Spanish mackerel have blue backs with flesh closer to the red side, but because their oil gathers right beneath the skin they get grouped separately as the blue-backed family. Put simply, the three branches are white flesh with burst muscle and little fat, red flesh with endurance muscle and plenty of fat, and blue-backed with an oil layer toward the skin, and these same three are what the Jagalchi floor calls them. Eight in ten guests ask why the colours differ the moment the plate lands. The answer is short: flesh that moved a lot is red. That is also the reason the restaurant veteran with over a decade at Jagalchi sets the plate down with the white toward the outside and the red toward the inside, because that arrangement is the eating order.

White flesh carries almost no fishy edge and its sweetness rises the longer you chew, which is why it is the first thing we recommend to anyone eating raw fish for the first time. Flounder comes out cut thin so the springy chew leads, rockfish has firmer flesh than flounder with a more pronounced bite, and sea bream is the softest of the three with a quiet sweetness that lingers. With little fat, elasticity arrives before any sense of melting in the mouth, and that is exactly what lets it pair well with strongly seasoned combinations like vinegared chili sauce or a leaf wrap. It is also why most of the fish that goes into the sashimi set meal at KRW 20,000 (about USD 14) or the sashimi rice bowl at KRW 15,000 at a Jagalchi Haean-ro restaurant belongs to this family: it is the dependable one. Look at a group table around 7 PM and the white plate empties first, with chopsticks only reaching the red side after a few rounds of drinks. If your party includes a child or an older guest meeting raw fish for the first time, or anyone who avoids fishy flavours, starting with a small size weighted toward white flesh is the choice that does not go wrong.

Red flesh is fatty because that fish swims without resting. Tuna, yellowtail, salmon and skipjack have to keep covering long distances, so they bank fat between the muscle like fuel, and once that fat reaches your mouth it melts at body temperature and turns into a deep savory flavour. Yellowtail puts on flesh as winter approaches with the belly cuts especially rich, while salmon carries even fat through all four seasons and stays soft enough that someone new to raw fish finds little to resist. One piece weighs heavier in the mouth than white flesh, so three or four pieces fill you, which is why the share it takes up on a platter is normally smaller than the white side. On Jagalchi Haean-ro there are days when the fatty family comes out separately as premium wild-caught sashimi from KRW 80,000 (about USD 58) at the day-selected species price, and from the medium size at KRW 80,000 upward the red share rises noticeably. On a weekend evening, about half the tables are ones where the red plate empties first. With drinks involved, the red going first is the Jagalchi pattern.

Blue-backed sashimi is sensitive to freshness because the oil layer sitting right beneath the skin oxidises quickly once it meets air. For blue-backed species like mackerel, gizzard shad, Spanish mackerel and saury, that oil layer is the core of the richness, and the same oil becomes the source of a fishy smell as time passes. So the rule for this family is to eat it immediately after it has been cut, and a Jagalchi restaurant prepares it only once the order comes in and brings it straight out. Ginger, garlic or chopped spring onion alongside settles the oily weight, and soy sauce with a generous amount of wasabi suits it better than the vinegared chili sauce. Gizzard shad comes alive in autumn cut bones and all for a nutty chew, and with mackerel, the clearer the silver pattern on the skin side, the better the condition. Some guests try blue-backed for the first time and say it tastes fishy, and nine times in ten that is a case of the plate arriving and then sitting a while before they ate. Eat it the moment it arrives and the richness comes first. If there is a pregnant guest or a child at the table, shifting this family toward the cooked grilled fish set at KRW 15,000 (about USD 11) is the easier call.

White flesh wants vinegared chili sauce and a wrap, red flesh wants soy sauce and wasabi, and blue-backed wants ginger soy sauce. With little fat, the white side has a clean enough taste that the sharpness of the chili sauce does not cover the flesh but actually lifts its sweetness, and wrapping it in lettuce or perilla leaf with a clove of garlic turns one mouthful into a meal in place of rice. The red side carries plenty of fat, so laying chili sauce on it stacks oil and sweetness together and turns heavy fast, which makes a light dip in soy sauce with a little wasabi on top the cleaner move. The Jagalchi wrap goes in this order: one perilla leaf with lettuce layered on it, one piece of white flesh, a little chili sauce and one clove of garlic, while the fatty family does better eaten plain than wrapped, because that keeps the fat tasting of itself. The raw seaweed or cabbage salad served alongside rinses the palate regardless of colour, so take them between plates, and the side dishes rotate daily based on what is fresh. If the chili sauce dish empties first at a table it is a table that likes white flesh, and if the soy sauce goes first it is a table that likes the red side, which is the rule of thumb you can see from the floor.

The assorted platter at a Jagalchi Haean-ro restaurant is built by laying white flesh as the base and setting the red family that came in that day on top, under fixed-size pricing at KRW 60,000 small (about USD 43), KRW 80,000 medium (about USD 58), KRW 100,000 large (about USD 72) and KRW 120,000 extra large (about USD 87). The small size, built for two, is weighted toward the white side; from medium up, one or two more fatty species go on; and the large and extra large grow the plate itself while the range of colours widens with it. If you want to enjoy the red side on its own, there is the route of premium wild-caught sashimi from KRW 80,000 at the day-selected species price, where you get offered the species that yielded well that day, such as spotted halibut or roughscale sole. Saying mostly white flesh, or a bit more of the red, when you order gets the ratio adjusted within the same size. The location is 220m from Jagalchi Station (Line 1) Exit 2 toward Jagalchi Haean-ro, about a 3-minute walk, and with 190 seats across the first and second floors it takes group dinners. For four or more, calling +82-10-8998-4803 ahead holds the size and the seat. Around 7 PM is the busiest, so avoiding that hour gets you seated with no wait.