A method for washing fish flesh to remove water soluble sarcoplasmic proteins includes producing a mixture by combining wash water with fish flesh having sarcoplasmic and myofibrillar proteins, wherein the wash water removes some of the sarcoplasmic protein from the fish flesh； depositing the mixture on a screen separator. The wash water having sarcoplasmic proteins is separated from the mixture while a speed of the screen separator and a speed of the mixture at the interface with the screen separator remains about equal and reducing or eliminating shear forces at the interface between the screen separator and the fish flesh. Thus, washed fish flesh fish flesh with an increase in a percent of myofibrillar protein retained in the fish flesh is produced. In order to have a speed of the screen separator belt be equal with a speed of the mixture at the interface, the perforated screen separator is stationary, vibrating only in the up and down direction, advancing slowly or fast, or advancing only intermittently, while the wash water is allowed to percolate through the fish flesh and exit the perforated screen.
