The Freshest Fish Doesn't Always Make the Best Sushi

Fish has a freshness problem. The idea that we must consume seafood as immediately as possible after it's caught gets reinforced constantly. Think about how many "Catch of the Day" menus you've seen or seaside shacks that pull your dinner from the depths just before putting it on your plate. When buying fish, the advice is to avoid anything that smells fishy and to eat that filet as soon as possible. And there's nothing wrong with that mindset, except when it could interfere with us having the best sushi possible. That's what Mike Lim, corporate sushi chef for Roka Akor restaurants, is hoping to change.

Chef Lim comes from a South Korean family with a strong pedigree in fish preparation. His uncle was a prominent sushi chef in San Francisco and his parents were restaurateurs. At 18-years-old, Lim decided to dedicate his life to serving seafood, at one time studying under Chef Morimoto, and nearly two decades later he's still at it, leading a revolution of sorts based out of Roka Akor's San Francisco location. It's there that Lim has instituted a fish aging program that's allowing his chefs to deliver superior sushi. Yes, you heard that right: aged fish.

The concept of letting certain types of fish age before they're eaten isn't proprietary or even new. Chef Lim learned about it from his uncle, and certainly other sushi chefs around the world also subscribe to the practice and if you've eaten at a nice sushi restaurant, it's possible you've had aged fish and not even known it. The lack of awareness around fish aging could be due to it being a back-of-the-house technique that chefs might not think is pertinent to mention, or the simple fact that we're programmed to think old(er) fish is bad fish. That's why Chef Lim is on a campaign to educate customers about the process and reasons behind aging a variety of Roka Akor's sushi.

It all starts with, as you might expect, very fresh fish from Japan, usually the famed Tsukiji fish market. Lim says it's really a "mystery box" of whatever is in peak season. From there the aging process begins. For meatier fish, like tuna, Lim's team drains the blood and cuts the loins down into blocks before covering them in ice. They use a special highly-absorbent paper towel from Japan to remove as much moisture as possible. The fish is constantly monitored to make sure it's kept cold enough and dry enough to remain fresh. The washing and towel dressing is repeated twice a day for up to seven days before the fish is ready to be served as sashimi, maki or other specialty dishes.

More delicate fish, like those from the snapper family get a lighter two to three day treatment, some receiving a daily washing in a saline solution. Lim says the idea is to completely remove the metallic taste left by the blood, allowing just the flesh of the fish to shine through. What else does aging do? According to Chef Lim, the fish tenderizes a bit and the aging enhances the umami flavor. The pink flesh of a tuna turns a deep ruby red, and no, it doesn't smell. Occasionally flavoring elements are added onto the skin side of the fish during the aging process, such as green tea smoke or cherry blossom or seaweed to infuse the flesh with a hint of other flavor, though Chef Lim insists though that those additions do not overpower the fish itself.

Only certain species of fish receive this treatment, however—the aforementioned tuna and snapper for example. Shellfish, on the other hand should be eaten immediately. But Lim says that just as the quality of the product is important, so too is serving it when it when it has reached its peak. For some fish that time is up to a week after being caught, provided it's been cared for and monitored by a trained professional. That trained professional part is important and it's why Lim doesn't recommend trying to age fish at home. Even he has only implemented the labor-intensive process at one of his Roka Akor restaurants in San Francisco because of the training and facilities necessary, through he hopes to have other locations, including a new restaurant in Houston, serving up aged fish in the near future.