Structural Modification of Fish Gelatin by the Addition of Gellan, kappa-Carrageenan, and Salts Mimics the Critical Physicochemical Properties of Pork Gelatin

Pork gelatin is not suitable for halal and kosher application; however, fish gelatin (FG) can be modified for use as a pork gelatin (PG) mimetic. Herein, low-acyl gellan (GE), kappa-carrageenan (KC), and salts (CaCl2 or KCl) were combined with a 180 Bloom tilapia FG. A formulation comprising 5.925% (w/v) FG + 0.025% (w/v) GE + 3 mM CaCl2 best matched the physicochemical properties of PG. The modification increased the FG gel strength from 115 2 to 149 +/- 2 g (matching the 148 +/- 2 of PG), while the T-m increased from 27.9 +/- 1.0 to 32.4 +/- 0.8 degrees C (matching the 33.1 +/- 0.3 degrees C of PG). Nanoaggregates (diameter between 150 and 300 nm) could be an important structural factor affecting the physicochemical properties, as both PG and GE-modified FG showed a similar frequency distribution in this size group (57.4 +/- 1.6% (PG) compared with 56.3 +/- 2.2% (modified FG)). To further explore the differences between KC and GE in modifying of FG's structure, the FG-KC and FG-GE gels were compared. The zeta potential and Fourier transform infrared (FTIR) spectroscopy results for the FG-KC gel supported an associative interaction with complex formation, as indicated from the large aggregates and amorphous phase under atomic force microscopy (AFM). Contrastingly, a segregative FG-GE interaction took place in presence of CaCl2. These structures and interaction differences between FG-GE and FG-KC influenced the macro-properties of FG, possibly explaining the differences in the modification of the melting temperature of FG. A diagram representing the interaction-structure-physicochemical properties was proposed to explain the differences between the FG-GE and FG-KC gels.