Analysis of stress-strain behavior of Alaska pollock surimi paste at constant moisture content

Mechanical responses to the applied stress on Alaska pollock surimi paste were analyzed with respect to the strain, storage modulus (G′), and loss modulus (G″). The mechanical properties of the paste with 83% moisture were measured using a dynamic rheometer (Bohlin CS-50, West Brunswick, NJ, USA). The yield stress was analyzed based on the stress-strain behavior during stress sweep test at 0.1Hz. Two-yield stress values, such as 218Pa and 653Pa, were obtained from the cross-sectional points of the three linear segments from the stress-strain curve in logarithmic scale. Structural meaning of two-yield stress values was interpreted based on the changes of dynamic properties of surimi paste, such as G′ and G″, during stress sweep. The yield stress value from the first cross-sectional point might indicate the stress that changes from solid-like gel to liquid-like sol, and the yield stress from the second point was the change from liquid-like sol to shear thinning fluid. Practical Application: Yield stress of the surimi paste is significantly important in designing the equipment for surimi seafood manufacturing. Particularly, in the molding operation of kamaboko and crabstick processing, the yield stress and shear thinning behavior of paste play major roles in designing the shape of extrusion die located between the pumping unit and heating unit. Appropriate design of extrusion head or molding die would be necessary to produce various shapes of commercial surimi seafood. In addition, the structural meaning of two-yield stress values will give an insight into developing the final product formula, if the yield stress values are obtained at various ingredient levels, such as moisture and/or starch content.