Four or five species sold under one word, with almost nothing in common. King crab is bought cooked and frozen and only needs warming; blue crab is picked by hand for an hour to yield a cup of meat; soft-shells are eaten whole, shell and all.
Blue crab, the Atlantic and Gulf species behind crab cakes and Maryland steaming, is small — meat comes from the body chambers and the swimming legs, and picking one takes real time. Dungeness, from the Pacific, is larger with substantial body and leg meat and is the best value for eating whole. King crab is enormous, sold almost exclusively as cooked frozen legs, with dense sweet meat. Snow crab is smaller and cheaper with more delicate meat. Soft-shell crabs are blue crabs caught within hours of moulting, when the new shell is still membrane-soft, and they're eaten entirely. Picked meat is graded: jumbo lump comes from the two large swimming muscles, lump is smaller pieces, backfin and claw are darker and cheaper.
Almost all crab is sold already cooked, because crab meat degrades unusually fast after death due to enzymes in the digestive tract, so processors cook them within hours of harvest. That changes the cooking problem entirely: for king, snow and most picked meat, you are reheating, not cooking, and the goal is to add as little heat as possible. Crab muscle is fine-grained and lean like lobster, and it turns stringy and dry above about 140°F. The grades matter texturally rather than in flavour — jumbo lump holds together in visible chunks, which is the point of a good crab cake, while claw meat shreds and is better in dips and soups where texture isn't the feature.
The Chesapeake method, and steaming rather than boiling keeps the meat from waterlogging and keeps the seasoning on the shell.
HowRack above an inch of water and vinegar, layered with Old Bay, lid on, twenty to twenty-five minutes until the shells are bright red. Let them cool enough to handle before picking.
They arrive cooked, so any further cooking is subtraction. The aim is warm through, nothing more.
HowSteam four to five minutes from thawed, or six to eight from frozen. Or 375°F oven wrapped in foil for eight minutes. Melted butter and lemon; nothing else is needed.
The entire crab is edible at this stage, and frying crisps the membrane shell while the interior stays custardy.
HowClean them — snip the face, lift the shell points and remove the gills, cut off the apron. Dredge in seasoned flour, fry in half an inch of oil at 350°F, three minutes a side. They pop and spit; use a lid as a shield.
The grade is doing the work. The binder should be minimal so the lumps stay visible and intact.
HowJumbo lump, folded gently with just enough mayonnaise, egg, mustard and cracker crumb to hold — the mixture should look barely bound. Chill an hour so they set, then sear in butter three minutes a side. Anything that needs a lot of filler was made with the wrong grade.
Nearly all crab sold in the US — king, snow, and every tub of picked meat — was cooked at the dock, because the meat spoils fast enough that processors have no alternative. Treating it as raw and giving it fifteen minutes in a pot produces exactly what people complain about: stringy, dry, faintly ammoniac meat, and an expensive ingredient turned into a cheap-tasting one. Legs need four to five minutes to warm through, and picked meat should go into a dish at the very end or not be heated at all. The related error is grade. Pasteurized tubs are heat-treated for shelf life, which softens the muscle and breaks up the lumps, so they're fine in a dip or a bisque and wrong for a crab cake where you're paying for visible chunks. Fresh or fresh-frozen jumbo lump costs more for a reason that's visible on the plate.
Live blue crabs should be active and heavy for their size. Dungeness is usually sold cooked whole and is the best value for eating with your hands. King crab legs are sold cooked and frozen — buy them frozen rather than thawed at the counter, since thawed-at-the-shop is just frozen crab that has been sitting. For picked meat, jumbo lump for crab cakes and anything where the pieces show, claw meat for dips, soups and pasta at a third of the price. Check the country of origin and whether it's pasteurized. Soft-shells are seasonal, usually spring, and should be bought live and cleaned just before cooking. Figure a pound of legs or two Dungeness crabs for two people.
Doneness: Live blue crabs: steamed twenty to twenty-five minutes until bright red. Pre-cooked legs: warm through only, four to five minutes steamed, internal 130-140°F. Soft-shells: three minutes a side at 350°F. Picked meat in a hot dish should go in during the last minute.
Enzymes in the digestive tract break down the meat very quickly after death, faster than in most shellfish, so processors cook crabs within hours of landing to arrest it. That's why live crab is only really available near where it's caught, and why everything else — king, snow, tubs of picked meat — arrives already cooked. Once you know that, the cooking instructions for most crab reduce to 'warm it up'.
Where on the crab it came from. Jumbo lump is the two large muscles that power the swimming legs — big, white, intact chunks, the most expensive. Lump is smaller pieces of the same plus broken jumbo. Backfin is smaller flakes from the body. Claw meat is darker, stronger-flavoured and cheapest. For a crab cake where visible lumps are the point, buy jumbo lump. For a bisque or a dip, claw meat tastes better and costs a third as much.
Three cuts. Snip off the face just behind the eyes. Lift each pointed side of the top shell and pull out the feathery gills underneath — they're unpleasant and don't cook down. Turn it over and cut off the apron, the small flap on the belly. That's it; everything else is eaten. Do it just before cooking, and ask the fishmonger to do it if you'd rather, but then cook them the same day.