Why Does Lobster Turn Red When You Cook It? (PopSci)

Summer in New England means many things, but especially lobster.  Ever wonder why they turn red?  Now you know:

Though natural color variations due to diet and genetics do occur, the shelled seafood you crack open at Red Lobster probably didn’t start off that deep orange-red color we’ve come to associate with crustacean snacks. Live American lobsters usually look kind of muddy brown, even though their shells contain astaxanthin, a carotenoid from the same family of organic pigments that includes beta-carotene, the source of carrots’ bright hue. Astaxanthin is also responsible for the pink coloring of flamingos, salmon, krill, shrimp and crabs.

Lobstah. (Photo: bennylin0724 via Flickr - CC BY-NC)

Lobstah. (Photo: bennylin0724 via Flickr – CC BY-NC)

Free astaxanthin appears red, but when it binds to proteins in the lobster’s shell, the bonds twist the pigment, changing its color. Depending on the type of protein it bonds to, there’s either what’s called a bathochromic shift, which turns the pigment blue, or a hyspochromic shift, to yellow. When you’re looking at a lobster, you’re seeing light reflecting through different layers of free and bonded astaxanthin–a lot of colors mixed together, hence the muddy brown.

Adult lobsters’ size keeps them from getting eaten by most other sea creatures, but since it takes them 7 years to grow to their full stature, a little bit of camouflage is a survival necessity in the interim. The nondescript color helps them blend into their surroundings at the bottom of the ocean. “They really need to have this cryptic lifestyle,” says Michael Tlusty, the director of research at Boston’s New England Aquarium.

“What happens when you cook it, you denature the protein through the heat, and it releases the pigment,” he explains. The resulting free astaxanthin makes the shell red all the way through. The same process applies to crabs and shrimp. Read more.

To learn more about the chemistry of cooking, check out SP.287 Kitchen Chemistry:

This seminar is designed to be an experimental and hands-on approach to applied chemistry (as seen in cooking). Cooking may be the oldest and most widespread application of chemistry and recipes may be the oldest practical result of chemical research. We shall do some cooking experiments to illustrate some chemical principles, including extraction, denaturation, and phase changes.

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