The pigment responds strongly to heat, though: Once you dump a crab or a lobster in a pot of boiling water, it's body chemistry changes: The pigment—astaxanthin—gets separated from the membrane—the crustacyanin—transforming your dinner into that ruby-hued tone we know so well.
Fresh blue crab is blueish gray, but after a few minutes in boiling water, it turns a vibrant shade of red. At that point, you know it's just about time to take it off the heat.
A fully cooked crab claw will look bright red or orange—the color most people think of on crabs. An undercooked or uncooked crab shell will be green or brown in color.
Many consumers mistake the change from the raw, blue-green color to the red-orange color of the crabs as an indicator of adequate cooking. One seafood cookbook for example, recommends cooking crabs until they turn red (Stanforth, 1969).
Heat destroys the protein coating, and when the animals are cooked, the astaxanthin molecules are released, thus changing the color of the crustaceans.
The pigment responds strongly to heat, though: Once you dump a crab or a lobster in a pot of boiling water, it's body chemistry changes: The pigment—astaxanthin—gets separated from the membrane—the crustacyanin—transforming your dinner into that ruby-hued tone we know so well.
Crustacyanin, the colorant in lobster shell, consists of pigment molecules confined in a colorless multiprotein cage. On heating, the proteins denature, releasing their grip on the pigment molecules. Unshackled, the pigment molecules promptly turn red.
Claw. Claw meat is the dark pink meat that comes from the swimming fins and claws of the crab. It has a stronger taste, and is less expensive than the white color meat grades.
Cook the crabs for about 18-20 minutes, depending on size. The crabs are done when they turn orange and the meat flakes when tested with a fork. Carefully remove the crabs from the pot with clean tongs and serve on a platter with a sprinkling of seafood seasoning and some lemon wedges.
While they might be bright red when they hit your dinner plate, crabs and lobsters are usually brown, olive-green or gray when alive and in the wild (at least in the mid-Atlantic U.S.; crustaceans farther south come in a variety of vibrant colors).
Fishing and Cooking
Despite its great numbers, Christmas Island red crabs are not considered edible, at least not edible to humans.
Crab meat should smell a bit sweet; if it has a strong, fishy, sour odor––it's time to toss it. The shelf-life in a fridge is 3 to 5 days and in the freezer is 6 to 9 months. Whole cooked crab that is frozen can last from 9 to 12 months.
Other types of seafood, like shrimp, crab, scallops, eel and octopus are also widely and safely eaten raw.
Fresh crabs should be clean and their flesh should be a little moist. If you detect any hint of sliminess anywhere, this is a bad sign. Slime or mucus on any part of the crab indicates that there is bacteria growing on that portion.
It's the roe or eggs, also called "coral" in shellfish. Coral is delicious when it's warmed and served on toast or used in crab cakes.
If you're having any doubt about whether crab legs are cooked, look for visual cues – raw crab has a greenish-brown shell, and cooked crab has a white and pink or reddish shell. You can also check the crab leg packaging or ask the fishmonger if the crab legs you're buying are fully cooked.
Frozen crab legs are often precooked, so you're just reheating them in the boiling water. If that's the case, be careful not to overcook them, as the meat will toughen and lose its delicate flavor.
Once cooked and cooled, peel back the top shell and rinse the crab with water to remove the guts and gills.
Pink Crab Meat is more abundantly available than other grades of crab meat, and is considered one of the best values in terms of price. One serving of this fat-free food provides 17% of the daily needed protein. Try Pink Crab Meat in your favorite dips, salads and crab cakes.
It is these carotenoids that are what give salmon its pink color. Before the shrimp is cooked the astaxanthin is covered by protein chains called crustacyanin. The protein chains in fact wrap up the astaxanthin, concealing its lovely pinkish-red color.
Crabs can be killed by rapid destruction of both nerve centres by piercing both ganglia from the underside of the crab with a pointed spike (e.g. a thick, pointed pithing instrument, an awl or a sharp-pointed knife). Spiking must not be performed on lobsters because they have a long chain of nerve centres.
Because these protein chains are not heat-stable, their protein wrapping uncoils as soon as crustaceans are put in boiling water. Voila! Red-orange astaxanthin molecules are released. Because pigments related to the carotenes are stable, the astaxanthins now display their unique deep hues that are so appealing.
Contrary to popular belief, the "mustard" is not fat, rather it's the crab's hepatopancreas, the organ responsible for filtering impurities from the crab's blood. Although many find its flavor distinct and delicious, it is recommended that you do not eat this since many chemical contaminants concentrate in the organ.
Crabs host a ton of critters (bacteria) and they are completely harmless/killed during cooking. however if the crab dies before cooking, that bacteria breaks down the meat and generates the ammonia smell.