Why does cooking meat change its texture and color?

When meat is cooked, heat causes proteins like myosin and actin to denature, meaning they unfold and then bond together in new configurations. This protein coagulation is what makes meat firm up and change from soft and pliable to a tougher, more solid texture. The more heat applied, the more the proteins tighten and squeeze out moisture, which is why overcooked meat becomes dry and chewy. The color change happens for a different reason. Raw meat gets its red color from myoglobin, an oxygen-carrying protein. When heated, myoglobin denatures and oxidizes, turning brown or gray. The appealing brown crust on seared meat comes from the Maillard reaction, where amino acids and sugars react under high heat to create hundreds of new flavor and color compounds.