Characterization of surimi slurries and their films derived from myofibrillar proteins with different extraction methods

Characteristics of surimi slurries and their films made from fish myofibrillar protein were investigated. Films made from fish protein slurries consisting of Alaska pollock surimi (15% and 20%) and sodium chloride (0%, 2%, and 5%) were either adjusted to different pH (7, 9, and 11) or mixed with sodium tripolyphosphate (STP) (1.0%, 1.5%, and 2.0%). Increasing pH from 7 to 9 led to higher viscosity and exposed sulfhydryl sites, while further pH increase 9–11) reduced the viscosity values and surface reactive sulfhydryl groups. NaCl and STP addition decreased slurry viscosity. In most treatments involving the roles of pH and either sodium chloride or sodium tripolyphosphate in film formation, sodium chloride addition contributed to lower puncture strength and puncture distance. Meanwhile, there was a tendency for elevated tensile strength and reduced elongation at break as sodium chloride concentration was increased from 0% to 5%. Shifting pH to a more basic condition contributed to higher puncture strength and distance. As STP concentration in the surimi slurries increased up to 2%, puncture and tensile strength increased, but puncture distance and elongation at break decreased.