Everything You Need to Know About Uni

This prized ingredient is beloved in kitchens from Japan to Italy.

Uni Explainer

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The edible part of the sea urchin known as uni has earned its status as a high-end sushi bar treat in Japan and now pretty much everywhere else. But sea urchins have been long fished and harvested anywhere there’s a coast, from Peru to Italy and Korea, where for centuries specially trained female scuba divers, called haenyeo, have free-dived to collect sea urchins prying these spiny creatures off rocks with knives. 

If you know uni, there’s a chance you love it. There’s also a chance that you took one look at this creamy yellow seafood and decided it would never enter your mouth. 

Uni is complicated. Some people will tell you it’s sweet and buttery, and while icy-cold raw uni atop a gunkan-maki at the sushi bar is their preferred way to enjoy it, it also tastes delicious when lightly cooked or steamed. Fans say the flavor evokes a dip in cool saltwater. Detractors use more colorful metaphors.

There comes a point in any discussion of uni where you have to get into the finer points of echinoderm physiology and explain that uni is a reproductive organ and not the roe, as it is often billed. Suffice it to say that each sea urchin produces five uni “tongues” that slip out with a spoon. Once you see a video of its harvesting, you’ll see that it’s not something you’d mind eating from the shell, like an oyster. 

Of the hundred-plus species of sea urchin, there are a handful that grow in commercial fisheries that diners are most familiar with. The waters around Japan’s northerly island of Hokkaido are famous for uni that feeds on pristine kelp, which gives it an umami-intensive flavor. There are several species of note, including Murasaki (purple) uni, which fetches the highest price for its large tongues and sweet flavor. Also worth mentioning is the smaller Bafun uni, whose name literally translates as “horse shit” due to the way these round, brownish creatures cluster on the sea bed. 

America has two major uni fisheries. On the West Coast, Santa Barbara uni comes from the giant red sea urchin and is noted for its large size, coarse texture and brightly sweet flavor. Back east, Maine uni comes from longer-spiked green sea urchins.

Freshness is the key to uni. It should be firm and bright colored without any signs of seepage and, ideally, still tiled or crisscrossed in its original packaging. Once harvested, it begins to melt, and its flavor can turn unforgettably bitter and off. In the best of worlds, uni is cleaned, iced and shipped before it can spoil. But it can also be treated with additives, including alum, to keep it firm. These chemicals may contribute to an off flavor if the uni gets old. Some sushi chefs, like Otto Pham of Chicago’s Kyoten, prefer ensui uni, which is shipped in a brine that mimics the salinity of seawater. 

Beyond the sushi bar, uni has been showing up in restaurants of every stripe. Because of its natural buttery flavor, it plays well with real butter, and can be mixed with butter as with these Barbecued Oysters with Smoky Uni Butter and this Squid Ink Mafaldine Pasta with Uni Butter. For a simpler recipe, try fresh fettuccine tossed with butter and herbs. A few tongues of uni folded in at the very end and stirred until just warm is delicious, and shows you another way to appreciate its flavor.

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