Sibling lobsters. Left: fed diet w/ Astaxanthin; Right: fed diet deficient in Astaxanthin pigment.

A: Astaxanthin is a red carotenid and is the most abundant carotenoid pigment found in some crustaceans (i.e. shrimp, crab, lobster). When the Astaxanthin pigment moves into the shell, proteins grab onto the end and twist it, flattening it out. This shifts the color (called a bathochromic shift) from red to blue. In an outer layer of the shell, the protein-astaxanthin cross-bind again; further twisting the pigment and again changing its color from blue to yellow (a hypsochromic shift). 

So, in living crustaceans we look through yellow and blue to red coloring resulting in the muddy brown lobster color (blue crabs have more pigment in the blue phase, European lobsters that are green have lots of yellow and blue). When they are cooked, the proteins denature, release the pigments and they revert to their red color.  

Source: Michael Tlusty, Ph.D., Director of Research, New England Aquarium

 

 

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