MadSci Network: Biochemistry

Re: What exactly makes a lobsters exoskeleton turn red when cooked?

Date: Thu Jun 17 15:47:41 1999
Posted By: Michael Onken, MadSci Admin
Area of science: Biochemistry
ID: 928820150.Bc

After multiple volunteers and a bit of research, I found the answer, and found it to be pretty simple. In the words of the Northeastern Fisheries Science Center, "The red pigment is the most stable component of the coloring in a lobster shell. The greens and browns which darken the shell in a live lobster are destroyed by cooking." For a more complete answer I did some further digging and found that the red pigment common to all decapod (shrimp, prawn, crab, lobster) exoskeletons (shells) is letons (shells) is astaxanthin, a carotenoid (like b-carotene, the pigment that makes fruits red-orange) found in many organisms from bacteria to birds. Astaxanthin was first identified in the exoskeletons of crayfish, Astacidea, hence its name. In lobsters, as in many decapods, astaxanthin is not a free pigment, but is complexed with a protein called a -crustacyanin, which alters the resonance of astaxanthin such that the complex acts as a blue-green pigment. As mentioned above, astaxanthin is heat stable, while the a-crustacyanin protein is not, so boiling the lobster shell denatures the blue-green a-crustacyanin releasing the red-orange astaxanthin.

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