Objectives:1) To determine solubility of the muscle proteins, especially myosin, of white and dark flesh fish at salt concentrations approximately equal to physiological concentrations using ions that specifically dissociate proteins and modify solubility properties; adjustment of pH will be an important variable;2) To correlate changes in myofibrillar and cytoskeletal structures of sarcomeres with removal of specific proteins;3) To determine functional properties of muscle protein preparations treated to solubilize myosin with emphasis on gelation, emulsifying ability and water holding capacity, conditions will be kept as similar as possible to those used in the solubilization experiments, and;4) To carry out the preparations of washed minced muscle and fractions thereof so as to minimize loss of protein and maximize functionality and stability.Methodology:This work will be carried out with both white and dark flesh fish. SOlubility of muscle proteins will be evaluated by suspending the minced/homogenized muscle tissue in aqueous solutions of various salt compositions and pH values. These conditions will be chosen to maximize protein solubility at physiological ionic strengths while using components that are acceptable to the U.S. FDA in food products. Total protein solubility will be determined as will the solubility of the individual proteins of the muscle tissue. Protein solubility will be related to changes in structural elements of the sarcomere and cytoskeleton. Correlations will be made between protein solubility and functional properties with emphasis on gelation, water binding capacity, and emulsifying properties. Procedures will be optimized to minimize protein losses while maximizing functionality and stability of the muscle preparations. Protein losses will be controlled by minimizing the washes necessary and controlling the pH and ion composition of wash solutions. Rationale:Depleted stocks of traditional species make it necessary to develop high value products from low value species and by-products. We propose a process by which good functional properties of both dark and white flesh fish can be developed using low salt concentrations. This should fulfill a need for low salt products, provide greater stability, and allow the use of fish proteins in non-muscle food products.