Dear Amber,. In lobsters, crab, and shrimp, however, a pigment called "astaxanthin" lies hidden, camouflaged by a protein covering. Astaxanthin is a member of the carotene family of pigments, which are responsible for coloring many of the yellow and orange or "carotene" fruits and vegetables. Because these protein chains are not heat-stable, their protein wrapping uncoils as soon as crustaceans are put in boiling water.
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. Same goes for usually boring grey shrimp , which also have a pink pigment in their meat and shells that is released by heat. There are also those very rare blue lobsters , which fishermen consider good luck charms.
Scientists think that one in every two million lobsters are born with that brilliant blue color, which is triggered by a genetic abnormality that causes them to produce a certain protein in overabundance. Prized for their beauty, these lobsters are mercifully tossed back into the ocean by fisherman searching for their more common-colored brethren.
By Elisabeth Sherman Updated May 24, Image: Shutterstock. The answer to this question lies in the breaking of specific chemical bonds by heat. When a prawn, lobster or crab is alive and well, scurrying around in its normal habitat, their shell is a dull grey or green colour, which helps them blend in with their surroundings. But when these creatures are exposed to heat — say, during the cooking process — all the pigments in their shell break down, apart from the one responsible for providing a red colour called astaxanthin.
This pigment is stable in heat and is usually bound to proteins in the shell. But as these proteins denature and unwind, it becomes free.
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