Gelation properties of tilapia fish protein isolate and surimi pre- and post-rigor

The structural changes and rheological properties of tilapia proteins prepared using two refining methods (pH shift processing and surimi processing, respectively) with pre- and post-rigor muscle were investigated. Higher storage modulus (G′) and better gel texture were observed in surimi produced from pre-rigor fish than surimi made from post-rigor fish, but no rigor effect was noted on the gel-forming ability of fish protein isolate (FPI). The effect of salt on the gelation of tilapia muscle with different rigor states or refining method was also determined. The addition of salt appeared to readily unfold protein structures in FPI as measured by surface hydrophobicity, surface reactive sulfhydryl content, dynamic rheology, and Raman spectroscopy. However, the effect of salt on the degree of unfolding in surimi was not as sensitive as in FPI.