Abstract: To provide a muscular protein denaturation inhibitor which is effective only in a small addition amount because of exerting an excellent effect of inhibiting heat denaturation and freeze denaturation of fish meat-origin muscular proteins, shows almost no taste as a solution, has been approved as a food additive, also has been employed as a component in supplements due to its health-promoting effects, and is safe to the human body. A muscular protein denaturation inhibitor characterized by containing a citric acid salt as the active ingredient and being capable of inhibiting heat denaturation and/or freeze denaturation of fish meat-origin muscular proteins.