Preactivated iota-carrageenan and its rheological effects in composite surimi gel

Hydrodynamically active iota-carrageenan was examined for the effects of its rheological properties and volume fraction on the textural, structural and thermal properties of composite surimi sol and gel, using dry, cold-water hydrated or thermally preactivated forms. To study the rheological effects, preactivated iota-carrageenans with different levels of solids were added to Alaskan pollock (Therragra calcogramma) surimi. For the effects of volume fraction, powdered or preactivated iota-carrageenan was incorporated into surimi at varying levels. Preactivated iota-carrageenan yielded a significantly weaker texture than the powdered and hydrated forms. A negative relationship was found between the initial compressive force and viscosity of preactivated iota-carrageenan and composite gel strength. A similar relationship was found between the volume fraction and gel strength. The rheological manifestation of dispersed biopolymers in composite surimi gel depended not only upon their rheological and hydrodynamic properties in the active state, but also upon the form in which they were dispersed, namely, strand or globule. The strands of preactivated iota-carrageenan may have structurally interfered with crosslinking required for gel network formation, causing gel weakening.