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Buying frozen fish isn’t what it used to be. Here’s what you need to know.

Standing in your grocery store seafood department, you see a counter with fillets of salmon, cod and tuna bedded on ice. Their tenderness beckons. Somewhere nearby, packages of those same fish and more, each fillet vacuum-sealed, wait behind a freezer glass door. They look . . . well, you can’t quite tell, but the labels indicate where the stuff comes from and its sustainability. Which ones will go in your basket?

In many cases, the frozen fish is less expensive and ought to be a slam-dunk. Yet “fresh is best” has been hammered home as a selling point for so many Americans fortunate enough to have the choice that they will opt for what’s on display.

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Why go frozen? “It is a major win for sustainability,” says Barton Seaver, the Maine-based chef and seafood educator who once called Washington home. “It decreases waste and takes advantage of seasonal bounty to spread its availability throughout the year.

“From the introduction of micro-misting to more powerful and rapid deep-freeze technologies at lower temperatures, the process has really turned frozen product . . . into a means to capture pristine quality,” he says.

Experts agree about those advances in technology, which can allow consumers to buy fish that is frozen mere hours after being harvested. The “fresh”-looking fish at the counter may be weeks old, and, these days, a good portion of it might be labeled “previously frozen” — all of which means that frozen can be fresher, or at least in better condition.

At the consumer level, though, frozen fish is still seen as less than optimal. You can’t open a package and smell it — a historically fail-safe test of quality — although I can’t remember the last time I saw a supermarket shopper ask to sniff first before her fish gets wrapped in paper.

Wegmans stocks half as much frozen fish as it does fresh, says Steve Philips, the East Coast grocery chain’s seafood group manager. With a few exceptions, the supermarket’s fresh fish on display has not been previously frozen — in part, he says, because Wegmans noticed that its customers “weren’t moving over to the frozen case.” The result is that its seafood department pulls fresh fish after two days in the case and destroys it; none of it is repurposed for in-house use.

Frozen fillets are priced significantly less than fresh at Wegmans, because their shelf life reduces consumer risk and company costs. “There is a misperception that what goes into a frozen package is somehow lesser quality, but that is not the case with anything we sell,” Philips says, adding that any frozen fish treated with chemical additives might be partially to blame. He advises consumers to compare labels when they shop for frozen (see TIPS, below). Wegmans’ frozen fish is chemical-free.

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A 2016 study funded by the National Fish and Wildlife Foundation that tested consumer preferences for fresh black cod and coho salmon vs. frozen (both bought at retail) found that the frozen fish, simply baked, were both rated superior or equal to their fresh counterparts. The study also measured the quality of those frozen and fresh fish, based on the conductivity of cell structure, and found that the overall score of the frozen fish was at least three times higher than the fresh fish.

So, you need to learn about frozen fish to maximize its potential. In return, you get to sample species that come from the Antarctic, such as Chilean sea bass, and enjoy it anytime. And by that I mean you don’t even have to defrost it before you cook it.

Tips for buying

* Terms matter. “Fresh frozen,” “frozen fresh” on the label means the fish was quickly frozen while still fresh, but it does not always mean from a raw state. “Quickly frozen” and “flash frozen” can mean the fish was subjected to a sufficient-enough blast of subzero air to freeze it, without any deterioration.

* Buy at a market with high turnover; ask how often frozen products are restocked.

* Check the label for additives. Sodium tripolyphosphate is a chemical that is used to retain moisture. The overall effect, says Wegmans’ Steve Philips, is that it adds weight to the frozen product that is then leached out during cooking: “It adds weight and increases cost to the consumer, and decreases the customer experience.”

* Never refreeze fish; if you plan to take it home and freeze what you buy, be sure it isn’t labeled “previously frozen.”

* When you plan to buy frozen fish, ask the fishmonger to pack it with a bag of ice. Bring a cooler with an ice pack for transport home. You want to keep that fish as cold as possible, to help reduce the formation of ice crystals, which can deteriorate the texture of the fish.

* The fish should be frozen solid, with no trace of liquid in the packaging.

* Cod fillets should be almost blue-white; cod that has a yellow cast or looks more opaque than translucent shows signs of age. Compare the color of frozen fillets with that of the cod that is sitting on ice at the seafood counter, to see whether there’s any difference.

Tips for defrosting and cooking

* Defrost frozen fish after removing it from its original vacuum-sealed, reduced-oxygen packaging. This helps eliminate risk of anaerobic bacteria growth. (This is the reason you may see a label, like the one shown above, on individual frozen fillets.)

* When you are not in a hurry, remove frozen fish from its original packaging and place on a plate; cover with plastic wrap and defrost overnight in the refrigerator.

*  You can marinate the fish as it defrosts in the refrigerator; for the last 20 minutes, add a simple and thorough coat of olive oil plus a few fresh herbs. Season with salt and pepper just before cooking. (See the shallow scoring on the skin in the fillet shown below? Do that with a sharp knife, because it will help the fish keep from curling as it cooks.)

*  To defrost frozen fish more quickly, remove it from its original packaging and place in a zip-top bag; seal and place under cool running water or change the water several times during the course of 15 minutes to an hour.

*  Cook from a frozen state. This works especially well with white-fleshed, skinless fillets; steaming is the gentlest method, followed by roasting and poaching.

*  Timing can vary; in general, figure 8 minutes per inch thickness of the fillet (140 to 145 degrees on an instant-read thermometer). The flesh should be opaque, and when you insert the tip of a sharp knife into the thickest part of the fish, the flesh should pull apart gently, but not so much that it “flakes” (a sign of overcooking).

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