Have you ever wondered why fish texture is so different from other animal foods like beef or chicken? While fish do have flesh made of skeletal muscle, its structure is fundamentally different from land animals, leading to a much more delicate and soft consistency.
Moreover, fish muscle has much lower amounts of collagen than the muscles of land animals. Collagen is a major component of skeletal muscle, making up much of the connective tissue between and around muscle fibers. The amount of collagen in meat determines, in large part, its texture. Meat with more collagen will be less tender than meat with less collagen. Different bovine muscle groups contain more or less connective tissue, and thus collagen, depending on how often they are used.
More heavily used muscles have more connective tissue and are thus less tender (although they may be quite flavorful) than muscles that are used less. However, while land animals average about 15% collagen, fish only average around 3%. This collagen breaks down more easily and turns into a gelatin-like substance, making for a much softer texture when eaten.
Why Does Fish Meat Flake?
Fish meat flakes because of its unique muscle structure called myotomes. Thin layers of weak connective tissue (collagen) separate these short muscle fibers. When cooked, this collagen breaks down into gelatin, allowing the layered myotomes to separate easily into characteristic flakes. This unique biological arrangement is what defines fish texture, making it fundamentally different from the dense muscle of land animals.
Fish Texture: Delicate, Medium Firm, and Firm
All fish flesh is more delicate than the flesh of land animals when cooked, but some fish are more delicate than others. Fish can be loosely grouped by firmness (delicate, medium-firm, and firm). The table below lists different fish by texture, arranged in order of flavor, with mild-flavored fish at the beginning and fuller-flavored fish at the end.
For example, cod and whitefish are both delicately textured fish, but whitefish has a stronger flavor than cod, so it appears further down the list. Shellfish are not included in this list.
| Fish | Texture |
|---|---|
| Cod | Delicate |
| Flounder | Delicate |
| Fluke (Summer Flounder) | Delicate |
| Haddock | Delicate |
| Hake | Delicate |
| Pollock | Delicate |
| Sole | Delicate |
| Perch (freshwater) | Delicate |
| Butterfish | Delicate |
| Turbot | Delicate |
| Whitefish | Delicate |
| Whiting | Delicate |
| Catfish | Medium-firm (varies) |
| Pike (walleye) | Medium-firm |
| Orange Roughy | Medium-firm |
| Tilapia | Medium-firm |
| Mullet | Medium-firm |
| Ocean Perch | Medium-firm |
| Trout | Medium-firm |
| Sea Trout (weakfish) | Medium-firm |
| Arctic Char | Medium-firm |
| Bluefish | Medium-firm |
| Mackerel | Medium-firm |
| Sardines | Medium-firm |
| Grouper | Firm |
| Halibut | Firm |
| Monkfish | Firm |
| Sea bass | Firm |
| Snapper | Firm |
| Tautog (blackfish | Firm |
| Tilefish | Firm |
| Mahi Mahi | Firm |
| Pompano | Firm |
| Shark | Firm |
| Sturgeon | Firm |
| Marlin | Firm |
| Salmon | Firm |
| Swordfish | Firm |
| Tuna | Firm |
| Fish | Texture |
|---|---|
| Cod | Delicate |
| Flounder | Delicate |
| Fluke (Summer Flounder) | Delicate |
| Haddock | Delicate |
| Hake | Delicate |
| Pollock | Delicate |
| Sole | Delicate |
| Perch (freshwater) | Delicate |
| Butterfish | Delicate |
| Turbot | Delicate |
| Whitefish | Delicate |
| Whiting | Delicate |
| Catfish | Medium-firm (varies) |
| Pike (walleye) | Medium-firm |
| Orange Roughy | Medium-firm |
| Tilapia | Medium-firm |
| Mullet | Medium-firm |
| Ocean Perch | Medium-firm |
| Trout | Medium-firm |
| Sea Trout (weakfish) | Medium-firm |
| Arctic Char | Medium-firm |
| Bluefish | Medium-firm |
| Mackerel | Medium-firm |
| Sardines | Medium-firm |
| Grouper | Firm |
| Halibut | Firm |
| Monkfish | Firm |
| Sea bass | Firm |
| Snapper | Firm |
| Tautog (blackfish | Firm |
| Tilefish | Firm |
| Mahi Mahi | Firm |
| Pompano | Firm |
| Shark | Firm |
| Sturgeon | Firm |
| Marlin | Firm |
| Salmon | Firm |
| Swordfish | Firm |
| Tuna | Firm |
Why are fish different colors?
You may also be wondering why some fish are almost pure white while others are darker colored or red. The pigmentation of fish flesh depends on the amount of oxygen-carrying myoglobin in the muscle. The amount of myoglobin, in turn, depends on whether the fish has muscles that are predominantly “fast-twitch” muscles, “slow-twitch” muscles, or a mixture of both.
Fish with mostly fast-twitch muscles are white-fleshed fish. These fish rely on quick and explosive bursts of activity followed by long periods of very low-energy activity.
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Fish with mostly slow-twitch fibers need to swim very long distances, so they require more oxygen in their muscles. These fish are the endurance athletes of the fish world. Some fish have some of both, so that they will have meat of varying shades of white or dark. Whereas sole will be very light-colored, tuna can be a very deep red, but with varying tons of lighter and darker flesh.
The fat content of fish also affects how dark the flesh appears. Some fish, as salmon and sea trout, may have other pigments that affect the color. These fish have a carotenoid pigment called astaxanthin, giving them an orange-pink color. This carotenoid is similar to beta-carotene responsible for the orange color of carrots. Astaxanthin accumulates the muscle (flesh/fillet) of salmon, giving it a pink-red color. It also concentrates in other parts of the body, including the skin, liver, intestinal mucosa, and eggs. The fish get this pigment from the insects and crustaceans they eat, which in turn get it from plankton.
You will notice a similar color when you cook shrimp, lobsters, crayfish, or crabs. These all contain astaxanthin, but it is bound to a protein in their shells, causing the color to be reddish-brown or even bluish-green, rather than deep red. When cooked, the protein is denatured, so that the true color of the astaxanthin comes out.
Similarly, when salmon or sea trout digest this protein, it is denatured, and the red pigment is stored in the fat deposits over time. Many commercially farmed salmon are provided astaxanthin artificially, using synthetically or naturally derived products so that farmed salmon have the expected characteristic color.
