LONDON: British scientists have solved one of the world’s great underwater mysteries — why lobsters turn red when cooked.

Lobsters are naturally purple, shading to other sombre hues. Maine lobsters, for instance have been fished up dark brown, green and even blue. “Lobsters only turn bright red after being cooked,” says one lobster website. “Neat, huh?” The answer boils down to the structure of a key part of the lobster shell protein called beta-crustacyanin. Just as a glass prism splits light into rainbow colours, a protein will reflect different colours as its shape changes.

A team from Imperial College, London, and Royal Holloway College, first purified crustacyanin and then grew three dimensional crystals of it in the laboratory. They called upon crystallographers at the UK’s University of Manchester, and x-ray experts at the Daresbury Laboratory to complete their study in scarlet. They report in the Proceedings of the National Academy of Sciences, a US journal, that they could visualize what happened when a custacean got into hot water.

The answer lay in a subunit of the lobster shell protein called astaxthanthin. It is a carotenoid, and like a carrot, would naturally be orange. But when clamped by beta-crustacyanin in a live lobster shell deep in the sea, the astaxthanthin flattened to become blue.

Once the lobster fell into the hands of a cook, it was doomed to a different tint. The bubbling water denatured the crustacyanin segment so much that it became stuck in its free form, coloured orange.—Dawn/The Guardian News Service.