This is due to a protein called myoglobin which stores oxygen in muscle cells, much like its cousin hemoglobin which does so in blood. When you cut into a steak, the red juices that come out are a mixture of the water in the meat and the myoglobin. Meats with more myoglobin are redder and considered “red meat,” while those with less or no myoglobin are considered “white meat.”
So what’s red meat and what’s white meat? Chickens and turkeys are considered white, but they do have more myoglobin in their legs since they use them more, so there is possibly a bit of red meat in them. Pigs are also considered white meat even though their bodies contain more myoglobin than other white meats. They still have a lot less than most red meats due to how little they move.
Fish are often white meat because they don’t need their muscles to hold themselves up, but there are some that are considered red meat. Sharks and tuna, for example, are fast swimmers and migratory and so need more myoglobin and are considered red meat.
