Reverse Screw Element(s) and Feed Composition Effects during Twin‐Screw Extrusion of Rice Flour and Fish Muscle Blends

The influence of location and spacing of reverse screw element(s) on specific mechanical energy input and product attributes during twin‐screw extrusion of rice flour and pink salmon blends was investigated. Incorporation of reverse screw element(s) increased specific mechanical energy, expansion ratio and water solubility index; but decreased bulk density and Warner‐Bratzler shear stress. Opposite trend was observed with increasing fish content except for shear stress, which was little affected either for rice flour or its blends with 30% fish solids in the expansion ratio range 5 to 10. Linear relationships were found between shear stress and bulk density and between solubility index and specific mechanical energy.