Uncooked shrimp can come in a variety of colors depending on the species, but they are typically transparent with a grayish-green or bluish hue. Shrimp flesh can have a light gray or pinkish-gray appearance, shrimps are translucent and light blue when they are fresh. Their color changes to a tasty brilliant orange when they are cooked. But as the shrimps cook, they turn pink or orange, thanks to a natural pigment called astaxanthin.

The group of pigments known as carotenoids includes the pigment astaxanthin. Shrimp (crustaceans) consume astaxanthin-containing plankton and algae for food. In their skin and shell, astaxanthin accumulates over time. The exact reason why crustaceans store this pigment is unknown. But if they are in shallow waters, it may protect them from the sun’s ultraviolet radiation. When alive, crustaceans camouflage their orange-pink hue to avoid being seen by predators. Here’s how the orange color becomes visible.

Shrimps’ astaxanthin molecules are altered by heat during cooking, changing how they reflect light. Astaxanthin molecules in raw shrimp are linked to proteins to create crustacyanin, a carotenoid protein pigment. Crustaceans’ bodies produce carotenoid protein while they are alive. It conceals astaxanthin while controlling and obstructing it. This stops light from reflecting, giving the crustacean its blue hue and translucent appearance. The animal can camouflage itself from predators in this way. However, the link between the two molecules is disrupted when shrimps are cooked. The proteins in the shrimps lose their structure when they are exposed to high temperatures, which causes the astaxanthin molecules to which they are attached to be released. Now that they are liberated, these pigment molecules reflect light in a way that gives cooked shrimp its bright pink or orange hue. Therefore, color can be used to determine whether shrimp have already been heated.