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Why do lobsters turn red?

by Hari M


Lobsters are known to change their color to red when they are cooked. Lobsters also possess various colors in their shells. The red color is due to the pigment called ‘Astaxanthin,. This pigment is surrounded by protein chains. The lobster shells appear dark colored. When lobsters are cooked, the protein chains get denatured and release the pigment inside them. So the dark colored shell changes to red colored one.

The lobster shell displays variety of colors and its body has carotenoid pigment. Most of the wild lobsters are brown to olive-green in color with red tinge. The protein chain wrapped carotenoid pigment in the lobster appears greenish-blue in color. The pigment Astaxanthin is the only one that remains stable when the lobster is heated. All other colors of the shell will be lost except red color. The cooking of lobster separates the carotenoid pigment from the protein chains. Now, the lobsters appear red in color due to carotenoid pigment. The release of pigment from the surrounding protein chains can be done by immersing the lobsters in boiling water.

Scientists have done research on why the lobsters turn red when cooked. This question was first put by biologist George Wald in 1940s. He was a Nobel Prize winner. The research on this issue was conducted by a team of scientists belonging to Imperial College, Manchester University, Daresbury laboratory and Royal Holloway University for seven years. They have come out with an answer.

They have identified the structure of the beta-crustacyanin which constitutes the shell protein of the lobster. The proteins surrounding the pigment Astaxanthin, changes its shape when cooked. The structure of the beta-crustacyanin changes after cooking and it tends to change even the shape of the bound pigment molecule Astaxanthin. The bound molecule gets released from the protein and imparts red color to the shell instead of blue. This research work was published in the journal proceedings of the National Academy of Sciences.

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