The orange stuff on a piece of uni sushi is the reproductive organ of a sea urchin. Menus call it roe, and that’s wrong. Sea urchins have separate sexes, so each piece is an ovary or a testis (SRAC Publication 7211).
Vinegared rice goes underneath, and the topping is served as gunkan maki or as nigiri. It’s creamy and briny, with some sweetness.
Sushi counters in Japan treat it as a premium item. At Toyosu in Tokyo on 5 January 2026, a 400 g lot of Hokkaido murasaki sold for 35 million yen (Guinness World Records, 2026).
What is uni sushi?
Uni (oo-nee) is the Japanese word for the edible gonads of a sea urchin. Each urchin holds five creamy orange lobes inside its shell, and they’re the only part of the animal people eat. Lay them raw on vinegared rice, or wrap them against it, and you get uni sushi.
The “roe” label is still wrong, since the lobes are ovaries or testes (SRAC Publication 7211). A piece on your rice can come from a male or a female urchin.
A typical piece has hand-pressed vinegared rice and raw uni, plus a strip of nori if it’s the gunkan style. There’s a dab of wasabi, and soy sauce comes on the side.
Ikura (salmon eggs) and tobiko, the tiny flying fish eggs, are real roe, and they often ride on the same nori-wrapped base. Uni isn’t roe, which is why it feels so different in the mouth.
What does uni taste like?
Most people notice the brine first and the sweetness a second later. The texture is custard-like, so it melts on the tongue instead of asking for a chew.
Fans compare it to foie gras or oysters. Everyone else calls it too much sea in one bite, which is why it counts as an acquired taste.
A 1964 sensory study by Komata (Nippon Suisan Gakkaishi) rebuilt the flavor from pure amino acids and nucleotides to see which compounds carry it. Glycine and alanine account for the sweetness. Valine adds a bitter edge. The meaty, savory side comes from glutamic acid, boosted by inosinic and guanylic acids.
Methionine is a minor component, yet the study found the characteristic uni taste doesn’t develop without it. It also thickens the flavor and lengthens the aftertaste.
What the urchin eats changes the result. A 2020 Frontiers in Marine Science paper on Mesocentrotus nudus linked higher alanine in the gonad to a more desirable taste, and raised it by adding glutamic acid and alanine to the feed.
Sushi Walker makes the same point from the fishing side: the more good kombu in the water, the better the uni.
Fresh uni smells of clean sea and tastes sweet. Poor uni turns bitter and metallic, and picks up an ammonia note as it ages.
The bitterness has more than one cause, and the freshness section further down sorts them out.
Bafun, murasaki and other uni varieties, and when each is in season
Murasaki (purple) and bafun (short-spined) show up at most sushi counters. Hokkaido adds kita-murasaki and ezo-bafun, and the rarer aka uni sits apart from both.
| Variety | Species and area | Color and flavor | Season by source |
|---|---|---|---|
| Murasaki | Heliocidaris crassispina (formerly Anthocidaris); warm waters from the Kanto region southward | Mustard to pale yellow, mild, clean | July to August (Gurunavi) |
| Kita-murasaki | Mesocentrotus nudus; Hokkaido | Pale, delicate, sweet | June to August on the Sea of Japan side (Sushi Walker) |
| Bafun | Hemicentrotus pulcherrimus; found across Japan | Small, orange, rich, occasional bitterness | October to November (Gurunavi) |
| Ezo-bafun | Strongylocentrotus intermedius; Hokkaido, Rishiri and Rebun | Vivid orange, intense, creamy | June to August on the Sea of Japan side (Sushi Walker) |
| Aka uni | Pseudocentrotus depressus; Kyushu | Creamy, rare, pricey | March to May (Japan-Food.guide) |
Around Shakotan in western Hokkaido, kita-murasaki makes up 80 to 90 percent of the volume reaching market, and ezo-bafun is the rarer, pricier one (Sushi Walker).
Some omakase counters, Udatsu Sushi in Tokyo among them, serve bafun and murasaki side by side so the difference is obvious (Omakase Je).
If you’re tasting both, start with murasaki or kita-murasaki and move on to bafun. Go the other way round and the murasaki tastes thin.
Aka uni is a slippery term. Gurunavi and Robb Report treat bafun as aka uni, Four Magazine applies it to the red urchin of Kyushu, and the Singapore blog I Eat I Shoot I Post uses it for the red sea urchin (Mesocentrotus franciscanus) landed in Canada and on the US West Coast.
Season tables disagree too. Visit Hokkaido names summer as the best time for kita-murasaki and ezo-bafun, and Sushi Walker puts the Sea of Japan side at June to August, when the nutritive cells in the gonads are full but the reproductive cells haven’t developed yet.
Gurunavi lists ezo-bafun for December to February instead, and Japan-Food.guide puts kita-murasaki at January to June around Cape Erimo and Rausu.
The gap is geography. Four Magazine reports that fishing dates are set legally, region by region, so ask where the uni was landed and not only which kind it is.
How uni is served: gunkan maki, nigiri, uni don and sashimi
Gunkan maki is what you’ll get at most sushi counters. The others are nigiri, uni don over rice, and plain sashimi.
Gunkan maki and nigiri
Gunkan maki is a hand-pressed oval of rice wrapped in a tall band of nori, leaving a shallow well on top for the uni. The wall exists because soft lobes won’t sit on a flat slice of rice.
Sushi Walker credits Hisaji Imada of Kyubey in Ginza with devising the form in 1941.
Uni nigiri, with the topping set straight on the rice, needs larger and firmer lobes, so it appears mostly with premium uni (Yuzu Omakase). Some chefs prefer it because nori can overpower the delicate flavor (Omakase Je).
Eat either one in a bite or two, soon after it’s made. Nori softens within a few dozen minutes (Sushi Walker), and many chefs season uni already, so taste before reaching for soy sauce.
Uni don and sashimi
Uni don skips the nori and piles the lobes straight onto rice.
Rebun Island is said to be the birthplace of the bowl (Visit Hokkaido). Shops on the Shakotan Peninsula serve it through the summer (Sushi Walker).
Served sashimi style, with no rice underneath, the lobes sit on the plate alone. Rice is the only difference between uni sushi and uni sashimi (Yuzu Omakase).
Soy sauce and wasabi are the usual companions, though very fresh uni needs neither. Dry sake is a common partner (Omakase Je).
How to tell fresh uni from bad uni
Good uni looks glossy, holds its shape, smells of clean sea and tastes sweet. Bad uni is dull or slumped. It smells of ammonia and tastes bitter or metallic.
Alum is one source of that bitterness, since the preservative itself tastes rough and bitter when overused (US Patent 5,169,661).
Age is another. Boxed uni turns metallic, then fishy, as it gets older (Tasting Table), and it develops an ammonia note as it degrades (Pogogi).
Handling matters too. A shaken or dropped box lets the myoban show through (Yama Seafood), and urchins held out of water before opening give roe that breaks down faster (University of Otago).
How uni is graded
No single grading scale exists. A 2020 Frontiers in Marine Science paper states that Japan has no quantitatively ranked classes for sea urchin gonads.
Sellers fill the gap with their own labels, mostly judged on color, texture, size and freshness.
- A, B and C (Sushi FAQ)
- AAA, AA, A+, A and regular, assigned by auctioneers (Weee listing for Hokkaido uni)
- Jou and Tokujou, set by each processor (Yama Seafood)
- Grades 1 to 3 for the best bafun and murasaki at Toyosu (Robb Report)
Narabi trays, with the lobes lined up, usually carry the higher grade, while bara trays (loose lobes) can mean less alum (Yama Seafood).
Read the letters as a seller’s shorthand. Compare trays on color, shape and smell instead.
Alum-treated versus alum-free uni
Alum (myoban, a potassium alum) firms the lobes so they survive shipping. Alum-free uni, labeled muban or mutenka, skips it.
Alum buys you shape and a lower price. Lobes keep their form through transport (Pogogi), and the uni is cheaper and easier to find.
The cost is taste. Overdosed uni tastes rough, bitter or metallic, and the firming effect lasts only a few days, per US Patent 5,169,661. An Icelandic Matis shelf-life study found that alum gave every green urchin sample a strong off-flavor.
Alum-free uni tastes cleaner, with no alum note (Pogogi), and a firm alum-free tray signals top grade, because only the best lobes hold together unaided (Weee). It does cost more and spoil faster (Pogogi), and it falls apart in transit unless the grade is top or the tray holds salt water (Weee).
Dose explains the gap between the Icelandic result and Japanese trade practice, since the patent ties the bitter taste to large amounts of alum. Brine-only storage avoids the problem altogether (Tasting Table).
If the uni is the point of the meal, order alum-free. Alum-treated is still fine when it was packed recently and tastes clean.
Checking a piece before you eat it
- Look at the lobes. They should be glossy, firm and defined, with no liquid pooling in the tray.
- Check the color. Vivid orange or gold signals top grade, while dull lobes are usually processing leftovers (Just One Cookbook).
- Smell the tray. Clean sea is right, ammonia means pass.
- Read the label for the packing date, the grade and whether alum was used.
- Taste one lobe. Bitter or metallic points to alum or age, so stop there.
Keep fresh uni in the refrigerator and eat it quickly. Freezing turns fresh roe mushy after thawing, and Matis found no difference between slow and rapid freezing.
Why uni costs so much, and when it is worth paying for
Supply is small, the roe breaks down fast, and extraction is done by hand. Prices are then set at auction, which is where the headline numbers come from.
| Driver | What the sources report |
|---|---|
| Auction pricing | Daily price set at Toyosu’s uni no seri (Sushi-pedia) |
| Grading | Shape, appearance, size and taste checked before the best lots reach auction (Robb Report) |
| Labor | Urchins hand-picked by divers or pole-caught (Four Magazine) |
| Supply | Japan’s domestic output down sharply since 1977, with imports from Russia filling part of the gap (Four Magazine) |
A few figures show how wide the range runs.
- JPY 35,000,000 for 400 g of Hokkaido murasaki, bought by Sushi Takamitsu and Unitora (Beyond Tsukiji Holdings) at Toyosu on 5 January 2026 (Guinness World Records). That is 87,500 yen per gram, against 2,100 yen per gram for the record tuna that same morning (AP).
- JPY 1.5 million for a 400 g box of Akatsuki, Hadate Suisan’s top grade of kita-murasaki, bought by Chef Hiroki of Sushiyoshi Hong Kong at the first auction of 2024, a record for that grade (Media OutReach; Time Out Tokyo)
- About JPY 4,000 to 5,000 per piece of uni on a Tokyo course menu (Japan-Food.guide)
The record lots are New Year publicity bids, not shelf prices. Nippon.com notes that the publicity value of winning the first tuna is hard to measure, even as competition for it intensifies.
Fresh, alum-free kita-murasaki or ezo-bafun eaten plain, as nigiri or sashimi, is worth the money. So is same-day uni from a counter that buys at the market each morning.
Frozen uni isn’t, because fresh roe turns mushy once thawed (Matis). Record-tier lots make little sense for a first taste either. And skip the good stuff for pasta or sauces, where preseasoned jarred uni does the job at a lower price (Just One Cookbook).
Red sea urchin from Canada and the US West Coast costs less than Japanese uni. It runs large and creamy, with a less intense flavor (I Eat I Shoot I Post).
Pay for freshness, not for a grade letter.
Is raw uni safe to eat, and who should avoid it?
Raw uni carries the standard raw-seafood warnings. People with a sea urchin or fish roe allergy should skip it, along with pregnant people and anyone with liver disease or a weakened immune system.
The allergy risk is real. Uni can trigger anaphylaxis, including on first exposure, according to Tanaka and colleagues (Int Arch Allergy Immunol, 2014).
IgE from four of their five patients recognized the major yolk protein. Binding to a second egg protein was blocked by salmon roe extract, which points to cross-reactivity with ikura.
An earlier report in Acta Dermato-Venereologica (Yamasaki et al., 2010) identified the same yolk protein as a major allergen after a patient reacted to uni sushi. It also notes earlier anaphylaxis reports after both raw and boiled roe, so cooking does not remove the allergy risk.
On the infection side, the CDC estimates 80,000 vibriosis illnesses and 100 deaths a year in the United States, with raw or undercooked shellfish a leading source.
None of that data is specific to uni. Parasites draw most of the attention in raw sushi, and that debate centers on fish.
| Group | Why they skip raw uni | Source |
|---|---|---|
| Allergy to sea urchin or salmon roe | Anaphylaxis risk | Tanaka et al., 2014 |
| Pregnant people | Raw seafood can carry Listeria and parasites. The advice lists sushi, raw oysters, clams and scallops, and does not name uni | FoodSafety.gov |
| Liver disease, cancer, diabetes, HIV, thalassemia | Higher risk of severe vibriosis | CDC |
Cooked formats exist, such as baked yaki uni and steamed mushi uni (Sushi FAQ). They address the raw-seafood risk, but not the allergy.
Is eating uni sustainable?
It depends on which urchin is on the plate. Off California, purple urchins that have grazed down the kelp are a pest, and ranching them is the proposed fix, while Japan’s wild catch has been shrinking since the 1970s (Four Magazine).
California’s purple urchin (Strongylocentrotus purpuratus) isn’t Japan’s murasaki. It boomed after sea star wasting disease killed the sunflower sea star, its main predator in Northern California (NPR).
Northern California has lost most of its bull kelp since 2014. The starving urchins left behind carry almost no uni (California Sea Grant).
Ranching targets exactly that gap. In a trial by Gardner and colleagues (Aquaculture America, 2021, NOAA repository), barren urchins on prepared diets went from a mean gonad index of 6.8 percent to above 15 percent in nine weeks, the marketable threshold, while kelp-fed urchins reached 11.7 percent.
There are trade-offs. The two prepared feeds gave similar roe yields, but one produced more bitter-tasting amino acids than the kelp-fed urchins did. The other gave a more natural flavor profile. A 2026 Aquaculture America abstract measured gonad size, texture and color on pellet-fed urchins but reports no taste test.
Barrens aren’t empty everywhere, and the answer changes with the species. A University of Tasmania thesis on the long-spined urchin Centrostephanus rodgersii found barren-living animals with commercially acceptable roe, which made feeding them up unnecessary there.
Work on Heliocidaris erythrogramma in Port Phillip Bay, Australia, found the opposite, with barren urchins carrying small, poor-quality roe (Pert et al., 2018).
Ranched purple urchin is the choice with a stated benefit for kelp forests, though the 2021 results come from tank trials, not a market.
Uni Sushi FAQ
Is uni the same as ikura or tobiko?
No. Ikura is salmon roe and tobiko is flying fish roe, both true eggs, while uni is the sea urchin’s gonad.
All three ride on gunkan maki, which is why they get lumped together in the same menu section.
How is uni harvested from the shell?
Processors cut the spiny shell open and lift out the five gonads, which rest against the inner wall.
Cutting on the wrong side can destroy the lobes, so the job takes practice (Umami Days).
Can you make uni sushi at home?
Yes, and the rice is the easy part. Sourcing is harder, because fresh uni needs live urchins or a fishmonger with high turnover (Pogogi).
Japanese grocery stores also sell imported uni (Just One Cookbook).
Why is bafun uni called horse dung uni?
Bafun means horse dung in Japanese, named for the round, short-spined shell that resembles it (Sushi Walker).
The name stuck even though ezo-bafun from Hokkaido is widely ranked among the best uni (I Eat I Shoot I Post).
Does uni sushi come with a quail egg?
Sometimes. Some sushi bars serve uni with a raw quail egg (Sushi FAQ), though it’s an option, not the standard.
The egg adds one more raw ingredient, so guests who avoid raw foods should ask first.
What to Ask for When Ordering Uni Sushi
A first order of uni sushi should be murasaki or kita-murasaki, landed that day, with the alum question settled before the plate arrives. That keeps both the price and the odds of a bitter first bite down.
Ask for the landing date and port first, then whether it’s alum or alum-free, and go from a mild variety to a rich one.
Freshness comes first because no variety or grade rescues old roe. The alum answer comes next, since it shows whether a bitter note is preservative or age.
Variety matters last, because the choice only counts once the tray passes those first tests.
The cost of this approach is money and time. Alum-free uni runs higher and should be eaten the day it is bought.
The advice holds as verified on 21 October 2026 and changes if a shared grade scale replaces seller-by-seller labels.
Pairing the uni with other dishes worth ordering alongside sushi rounds out the meal.
