Rheological properties and structure modification in liquid and gel of tilapia skin gelatin by the addition of low acyl gellan

Fish gelatin (FG) was modified by low acyl gellan (Ge) to produce a replacer for pork gelatin (PG). Increasing mixing ratio of Ge:FG (w/w) modified rheological properties and structure of FG progressively. The largest of FG-Ge complex coacervates (1775 ± 593 nm) formed at Ge:FG (w/w) of 7.5:92.5, driven by electrostatic interaction between FG and Ge. However, the network density was reduced by the formation of large complex coacervates (fractal dimension, df 2.45 ± 0.01 in FG-Ge vs. 2.48 ± 0.00 in FG). The non-interacting FG re-associated to a greater extent into triple helix (helix/coil ratio, 3.10 ± 0.93 in FG-Ge vs. 0.58 ± 0.07 in FG), therefore increased the rigidity of the gel. The mixed gel was stronger and more stable, with lower compliances (J0, Jm1) and a higher melting temperature (Tm) than FG. The mixed gel at a Ge:FG (w/w) of 1:99 had similar rheological properties to PG. A schematic model was proposed to illustrate the progressive modification of FG by Ge.