* Reddish-pink color change: This is most common in crustaceans like shrimp, lobster, and crab. It's not due to blood, but to a pigment called astaxanthin.
* Raw: Astaxanthin is bound to a protein, making it appear colorless or slightly gray.
* Cooked: The heat breaks down the protein, releasing the astaxanthin, which is bright red.
* White to opaque: Fish like cod, halibut, and tilapia will turn white or opaque when cooked. This is due to the denaturation of proteins in the muscle tissue.
* Other colors: Some seafood, like salmon, has a natural reddish-pink color even when raw due to the presence of astaxanthin in their diet.
So, it's not always about turning red, but rather about the changes in pigment and protein structure that happen when seafood is heated.