Why does meat change color when you cook it?

When meat is raw, it contains a protein called myoglobin, which holds oxygen and gives meat its red or pink color. When you apply heat, myoglobin undergoes a chemical change called denaturation, where the protein structure breaks down and unfolds. This process alters how the protein absorbs and reflects light, causing the color to shift from red or pink to brown or gray. The iron atom at the center of myoglobin also changes its oxidation state when heated, which further contributes to the color change. The specific temperature determines how much color change occurs, which is why a medium-rare steak stays pink in the center while a well-done steak turns fully brown throughout.