Why do lobsters turn red when cooked?

Lobster is usually green but when cooked, or heated (steamed, fried) their bodies turn bright red. Why is this impressive color shift?

Anita Kim, a scientist at New England Aquarium in Boston (USA), said lobsters often live in areas with rocks or mud. They rely on the characteristic blue pigments on the body to blend into the environment, avoiding the pursuit of enemies such as cod.

However, when heated, cooked, the distinctive blue color immediately turns into a bright red color. Why do lobsters turn red when cooked? Behind this seemingly simple question actually has many interesting things.

Pigmentation changes on lobster body when they are heated, cooked.

Since the 1870s, scientists have been searching for ways to understand the pigmentation changes in lobster bodies when they are heated and cooked.

For over a century, it has been found that two molecules in the lobster body are responsible for this particular transformation. The first is because the protein is called crustacyanin and a carotene (a pigment responsible for red, yellow and orange colors) is called astaxanthin .

When astaxanthin is free, it is red. Notably, lobsters cannot produce astaxanthin themselves, which they obtain due to diet. When linked to crustacyanin, astaxanthin turns green.

It was not until 2002 that researchers discovered that the crustacyanin protein alters the color of astaxanthin pigment by twisting the molecule and changing the way it reflects to light.

Therefore, when lobster is heated to a high temperature (baked or steamed), crustacyanin will remove astaxanthin, allowing the pigment to be unmodified and show its true color.

Meanwhile, the crustacyanin molecules lose shape and reorganize in different ways. It is the physical change in the shape of the protein that has a marked effect on the color of the lobster.

Michele Cianci, a biochemist at the Marche Polytechnic University in Italy, said: "Imagine you're holding a rubber band. You can bend the rope into many shapes you want. launch the rope, it will return to its original shape ".

"Similarly, like crustacyanin molecules that can twist astaxanthin, when crustacyanin is heated, it will bring astaxanthin to the free state, showing the original red pigment , " concluded Michele Cianci.

1. Explain why food changes color when cooked