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Why Is Fish So Flaky? (And How to Cook It Well)

The mystery of flaky fish, unraveled. Understand why fish flakes when cooked and what that means for how you prepare it.

When handling, cooking, and eating fish, one can’t help but to notice that these creatures of the sea are nearly weightless compared to their counterparts who live on the land.

Their bones, light and pliable, can be boiled, fried, or baked to the extent that they melt in the mouth. Their flesh, pale and tender, flakes when pressed with a fork, giving minimal resistance when bitten into.

This makes the curious among us wonder: Why is fish this flaky? What is it that makes the texture of the flesh of aquatic animals so different from that of cattle, swine, and lambs? The answer, as it turns out, is in its structure. Take a gander below to find it out.

Fish is flaky and fragile because its muscles are arranged in flakes and have very little collagen—the connective tissue that holds muscles together and gives elasticity to joints—between them.

Not only that, but the collagen in fish melts and turns into gelatin at temperatures significantly lower than that contained in the meat of land animals. This means it doesn’t take much to make cooked fish tender and succulent.

“Meat collagen,” American culinary writer Harold McGee writes in his book, On Food and Cooking: The Science and Lore of the Kitchen, “is tough and must be cooked for some time near the boil to be dissolved into gelatin.”

McGee goes on to explain that, in most fish, collagen dissolves at 120-130°F (48.8-54.4°C), at which point the muscles separate into flakes. Fish muscles, in addition to that, are designed to work in cold water, not ambient air. Believe it or not, they start to cook at room temperature, the main reason why fish spoils so quickly.

All of this together is what makes fish flaky and fall-apart tender. It’s also why fish remains frangible, if dry, even when it’s overcooked.

Selecting the Best Fish at the Market

Fish, high in protein and low in fat, is a delicious and nutritious food to send to the table. Exactly how low in fat the fish is depends on the variety: Salmon, mackerel, and trout are on the fattier side; cod, haddock, sea bass, and monkfish are on the leaner side.

Fish also has the tendency to spoil fast—much faster than the meat of land animals does. For this reason, knowing how to choose fish at the fish market or grocery store is a skill that every cook, whether they live near the sea or not, should have.

When selecting whole fish, trust your senses. You’re looking for firm, supple skin and a scent reminiscent of the sea or a lake. As a general rule of thumb, you want to stay away from anything that smells off, feels slimy, and seems dated.

Look for bright, bulging eyes; murky, sunken eyeballs are a tell-tale sign that the fish at hand is past its prime. The gills on the fish should be red and lively; if the redness is replaced by a light brownish hue, it is stale. The scales should have a metallic sheen on them and not be sticky and slimy.

Nowadays, fish is gutted, filleted, packaged, and sold in the supermarket, whether at the fish counter or in the frozen foods aisle. Look for firm, white fillets with a shiny, reflective surface. Pink spots are signs of bruising and brown spots are signs of spoilage.

Storing And Thawing Fish at Home

Refrigerate the fish in the lowest shelf of your fridge, where it is coldest, and cook it within 1-2 days of unpacking your grocery bags. If you want to store the fish for longer, seal it in freezer bags and put it in the freezer, where it will keep its best qualities for 2-3 months.

To thaw fish, move it from the freezer to the fridge the night before you plan to cook it. Place it in a tray, a deep plate, or a bowl to catch the water that drips from it (handle safely; that water is laden with bacteria) and prevent it from pooling in your refrigerator.

To thaw fish quickly, use the “Defrost” setting on your microwave or put it in a zipper bag and submerge it in a bowl of cold water. For food safety reasons, it’s imperative to cook the fish immediately after.

Remember that raw fish shouldn’t be left at room temperature for more than 1-2 hours—thawing fish by leaving it out on the counter for hours on end is out of the question. Otherwise, pathogenic bacteria can grow on the surface in dangerous quantities, making it impossible to eat.

Cooking Fish to Deliciousness

Fish, despite lore to the contrary, is one of the easiest proteins to prepare. The only non-negotiable is to have good fish (and we already covered the basics of selecting it).

For starters, fish can be seasoned without fuss. Nine times out of ten, it’s enough to salt the fish and spice it up with a pinch or two of freshly cracked pepper. It’s also easy to prepare: Boil it, fry it in olive oil, or slide it in a hot oven and turn it once. Finally, it goes deliciously with grains, greens, and starchy veg alike.

To prepare whole fish for cooking, you must gut them and remove the scales. Some cooks debone the fish using gloves and pliers or tweezers. Fish, whether whole or filleted, should be rinsed under cold running water to remove fish odor—then patted thoroughly dry for cooking.

Thin fish cook quickly, in a matter of a few minutes. As such, they tolerate high heat on the stove or cooking under the broiler, and can be prepared hastily on weekdays. Large fish and thick fillets take time; they’re best prepared over medium heat, and the cook must be very attentive lest they overcook.

To keep fish fillets intact, fry them in a ceramic, non-stick, or well-seasoned cast iron skillet skillet with a dollop or two of cooking oil. The cooking oil will keep the fish from sticking to the bottom and assist in the transfer of heat, which leads to better browning and more even cooking.

Bake fish, whole or filleted, in a sheet pan with a wire rack that lifts it off the cooking surface and eliminates the need for turning. The less you need to handle the tender, delicate fish, the lower the chance of you mangling it.

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Written by

Jim is the former editor of Home Cook World. He is a career food writer who's been cooking and baking at home ever since he could see over the counter and put a chair by the stove.