system
Given the following post, respond as if you're commenting on Reddit:
human
Why do crabs which are greyish in color turn reddish or orange when boiled or cooked?
gpt
When crabs and lobsters are alive, they have a protein-ligand complex called astaxanthin-crustacyanin. This appears as a blue/gray color. When they're cooked, the protein, crustacyanin, denatures and the astaxanthin becomes unbound. The unbound astaxanthin's color is the red that you see. It's also what gives salmon and shrimp their red colors.