Why Do Crabs and Lobsters Turn Red When You Cook Them

Why Do Crabs and Lobsters Turn Red When You Cook Them?

Whether it is boiled or baked and grilled, if lobsters are heated to a high temperature which is the boiling temperature 100°C and it will allow astaxanthin to appear its true colour which is the bright red colour. The physical alteration of the protein’s shape has a remarkable effect on the lobster’s colour.

The lobster is heated and the crustacyanin molecules in the shellfish are losing its structure and reorganizing in different ways. It has the same concept as the rubber band. If the rubber band in your hands is stretched it is the same as astaxanthin molecules twisting its form. It returns to its original form when you stop stretching the rubber band. For crustacyanin. It lets go of astaxanthin when it is heated at the boiling point making the lobster’s and crab’s pigment turn to bright red in the pot.


Crab and lobsters are typically orange, olive-green or grey when they are alive. But, when they reach the dinner plate they will turn into bright red. Changes in colour during cooking are related to how molecules react to heat. Astaxanthin is a pigment of carotenoid that absorbs blue light and tends to change its colour to red, orange or purple. Inside the crustacean’s shellfish there is a protein called crustacyanin as when they are alive. The protein simply holds the pigment so close that it is flattened and modified its light absorption characteristics.

The fact that Crustacyanin is not stable in heat causes it to break its bonds with astaxanthin by inserting it into a boiling pot of hot water and it unravels and allows the true bold red pigment to shine. One in every 100 million lobsters is albino and has no shell pigments.