Why does cooking meat change its color and texture?

When meat is cooked, heat causes the proteins inside to denature, meaning they unfold and restructure. Myoglobin, the protein responsible for meat's red color, breaks down and loses its ability to bind oxygen, turning brown or gray. This is why raw beef is red but cooked beef turns brown. The texture change happens because heat causes muscle proteins like actin and myosin to tighten and contract, squeezing out moisture and making the meat firmer. At higher temperatures, collagen in connective tissue breaks down into gelatin, which can actually make tougher cuts more tender with long, slow cooking. The Maillard reaction also occurs on the surface, browning the exterior and creating complex flavors through chemical reactions between amino acids and sugars.