Vegan seafood is the hardest fake to make, and here is the reason

Cut into a piece of cooked salmon and it comes apart in sheets, not strings. Cut into cooked chicken and it comes apart in strings. The difference is not cooking technique. Fish muscle is arranged in short segments called myotomes, stacked one after another and bonded by thin sheets of connective tissue called myocommata, and each myotome runs only a few centimetres before the next sheet interrupts it. Land animal muscle runs continuously for the length of the fibre, sometimes the length of the limb. When collagen in either tissue gelatinises under heat, land muscle disintegrates into long shreds and fish muscle disintegrates into flakes, because that is where the structural breaks already were.

This matters to a vegan seafood company for a specific mechanical reason. The technology that makes a convincing plant-based chicken breast or ground beef is extrusion: soy or pea protein is heated, sheared and forced through a die under pressure, which aligns the protein molecules into long parallel fibres, the same shape as land muscle. Extrusion is very good at making long fibres and structurally incapable of making short interrupted ones. Run the process longer or harder and the fibres just get longer and more aligned, which is the opposite of what a fillet needs. How vegan meat is made covers extrusion in full; the seafood aisle is where the same machine runs into a wall.

The first workaround is layering rather than extruding: sheets of gelled protein are stacked and lightly bonded so the finished piece separates along the seams when cooked, deliberately reintroducing the myocommata that extrusion erases. The second is to abandon fibre formation altogether and use a set gel, most often konjac glucomannan or an alginate matrix, which has no grain at all and instead delivers a springy, uniform bite that works for shrimp, scallops and squid rings, where the eater expects a bounce rather than a flake.

The third is 3D printing, and it is one of the few uses of food printing that is solving a real problem rather than a marketing one. A nozzle deposits protein paste in programmed layers, varying thickness and composition line by line, which lets a manufacturer put a fattier layer next to a leaner one and a bonded seam every few millimetres, reconstructing the myotome and myocommata pattern on purpose. Researchers at the National University of Singapore printed a squid ring analogue in 2023 from mung bean and microalgae protein using exactly this layered approach, and Israel's Steakholder Foods has taken a version of the same printing method, marketed as Drop Location in Space, to commercial fish and seafood blends. Extrusion still makes the world's vegan sausages; it is print heads and stacked gels that are making the world's vegan fillets.

Konjac glucomannan is a starch milled from the corm of the konjac plant, long used in Japanese konnyaku and shirataki noodles, and it is the reason plant-based shrimp and scallops are as close to the original as vegan seafood gets. On its own, konjac forms a soft gel that melts when reheated, the same limitation as gelatin. Treat the solution with a mild alkali and heat it to roughly 85C at pH 9 to 10, a deacetylation process described in a 2007 process patent, and the acetyl groups on the glucomannan chain are replaced with hydroxyl groups, letting the polymer chains hydrogen-bond directly to each other. The resulting gel is thermo-irreversible: it holds its structure through cooking, reheating and even a second reheat, unlike agar or gelatin, which is exactly the behaviour a frozen scallop or a canned shrimp product needs to survive distribution.

Researchers publishing in a 2021 study on plant-based fishballs found that raising konjac glucomannan concentration toward 8% progressively increased hardness, chewiness and gel strength when crosslinked with soy protein, which is the tuning knob manufacturers use to move a product from a soft fishcake texture toward a firmer scallop bite. Konjac alone carries almost no protein or fat, so it is nearly always blended with soy or pea protein isolate to add nutritional substance and bind the gel.

Sodium alginate is extracted from brown seaweed and gels through an entirely different mechanism than konjac: it does not need heat at all. Drop a flavoured alginate solution into a bath of calcium chloride or calcium lactate and the calcium ions immediately cross-link the alginate polymer chains from the outside in, forming a thin gel skin around the droplet within seconds. This is the same spherification chemistry that produces the caviar-style beads served in modernist restaurants, and it is what plant-based roe and caviar substitutes use to get a pearl that pops between the teeth rather than crushing like a paste. Because the gelling front keeps moving inward for as long as the sphere sits in the bath, commercial roe substitutes are usually pulled and rinsed within a minute or two, before the membrane thickens all the way through and the bead turns solid.

Alginate also shows up as a binder inside layered fillet products and plant-based fishballs, where it is combined with calcium or magnesium salts to firm the outer surface. The alginate verdict page covers where it is sourced and whether any form is animal-derived; it is not.

Battered fillet-style products, the ones built to be breaded and fried whole, generally skip konjac and build on soy protein concentrate or pea protein isolate set with methylcellulose or a starch binder, sometimes layered with wheat gluten for chew. Good Catch's plant-based tuna uses a six-legume blend of pea protein isolate, soy protein concentrate, chickpea flour, lentil protein, faba protein and navy bean flour, shredded and pressed rather than extruded, which is closer to the layering approach than to a chicken-style extrudate.

Flavour is the part manufacturers rarely explain, probably because the honest explanation involves the word algae twice. Fresh seafood's marine taste comes largely from bromophenols, compounds that fish and shellfish do not synthesise themselves but accumulate from eating bromophenol-rich marine worms and algae, and from dimethyl sulfide, released when marine algae break down a compound called DMSP, which is also the molecule most responsible for the smell of the open ocean. Since no plant makes fish flavour directly, formulators extract it from the same source the fish did: seaweed and algal extracts supply the bromophenols and dimethyl sulfide precursors, rather than any synthetic fish flavouring. It is a rare case in the plant-based aisle where the flavour ingredient and the mechanism are the same seaweed.

This is the category's weakest point and the brand will not soften it. Konjac and starch-based gels carry almost no protein of their own, so a shellfish-style product built mainly on konjac can land far below the fish it replaces: a breaded plant-based shrimp typically supplies around 4g of protein per serving against roughly 18g in a 3oz serving of real shrimp. Soy and pea based fillet products do better; a plant-based fish fillet built on soy protein runs closer to 9g per piece, and Good Catch's legume-blend tuna reaches about 14 to 17g per 94g pouch, within range of canned tuna's 20g but still generally lower.

None of it supplies EPA or DHA, the two long-chain omega-3s fish are prized for, unless a manufacturer has deliberately added algal oil, which some do and most do not. The omega-3 evidence page covers the health case for EPA and DHA in full; the omega-3 verdict page covers sourcing. A 2024 review in the journal Current Research in Food Science, by researchers surveying plant-based seafood alternatives, found fortification with B12, vitamin D, iodine, zinc and omega-3s minimal across the products on the market. Good Catch is a rare exception, adding 350mg of algal DHA per pouch of its tuna. The rule for a shopper is simple and unglamorous: check the panel for grams of protein and for the words algal oil or DHA, because neither is guaranteed and the label is the only way to know.

The ethical case for not eating fish sits on the can vegans eat fish guide; this section covers the reasons someone who has not made that call might still reach for the plant-based aisle. The FAO's 2024 State of World Fisheries and Aquaculture report found 35.5% of assessed marine fish stocks were fished at biologically unsustainable levels in 2021, up from 10% in 1974, even as the weighted share of landings from healthy stocks stayed higher at 76.9% because well-managed large stocks still produce most of the tonnage.

Bycatch, the unintended capture of non-target species, adds a separate cost: a 2020 study in Scientific Reports estimated 9.1 million tonnes of catch discarded annually worldwide between 2010 and 2014, about 10.8% of total catch, with trawl fisheries responsible for the largest share. Mercury is a slower-moving concern: the FDA and EPA's joint fish advisory rates albacore tuna at roughly three times the mercury of canned light tuna and limits pregnant women to one serving a week of albacore against two to three servings of the lighter varieties, because larger, longer-lived fish accumulate more methylmercury up the food chain.

Labour conditions add a fourth, less visible cost. An Environmental Justice Foundation investigation, drawing on interviews with more than 430 Indonesian and Filipino fishers across 249 distant-water vessels, documented wage theft, violence and shark finning concentrated in the squid fleets of the Northwest Indian Ocean, Southeast Pacific and Southwest Atlantic, fleets the report says together supply around 60% of the world's squid. A 2023 U.S. Congressional investigation separately found 357 of 751 vessels in China's distant-water squid fleet, the largest in the world, tied to documented human rights or environmental violations. None of this is an argument that every fish sold is caught this way; it is the honest complication that sits behind a market that has grown for reasons well beyond animal welfare.

The processed aisle is not the only route in, and for some dishes it is not the best one. Banana blossom, the unopened flower bud of the banana plant, has a fibrous, pale flesh that shreds into flakes under a fork once simmered and pressed, which is why it has become the standard base for vegan battered fish and fish and chips; it carries almost no protein of its own, so the dish's protein has to come from the batter or a side. Hearts of palm, the inner core of certain palm trees, splits into long shreds well suited to crab cakes and lobster rolls and carries a modest 1.5 to 4g of protein per 100g depending on the source. King oyster mushroom stems, sliced into rounds and seared, brown and firm up in a way that mimics a scallop's sear far better than any gel does, because the mushroom's own cell structure collapses and caramelises the way muscle does. Firm tofu, marinated and pan-fried, stands in for a flaky white fish with 15 to 17g of protein per 100g, more than most commercial products in this category.

Smoked salmon is the case where the trick is entirely about flavour rather than texture: thin slices of carrot or tomato, cured briefly in salt and liquid smoke, take on a translucent, fibrous look close enough to sliced salmon that the flavour carries the illusion. Finish any of these with a strip of nori or a pinch of ground kombu and a caper, and the dish gets the same dimethyl sulfide and glutamate notes seaweed supplies to commercial products, for the cost of a pantry ingredient rather than a manufacturing process.