Combination of sodium alginate with tilapia fish gelatin for improved texture properties and nanostructure modification

Abstract

Fish gelatin (FG) has been studied intensively as a potential replacement for mammalian gelatin; however, modification of the physicochemical properties of FG is often required to make them similar to those of mammalian gelatin. In the present study, sodium alginate (SA) was combined with tilapia FG to modify its properties to resemble those of mammalian gelatin. When the concentration of SA was increased from 0.05 to 0.4% (w/v) in a 6% (w/v) FG gel, the gel strength and hardness increased. However, at 0.60% (w/v) SA, the gel strength and hardness decreased. From 0.2 to greater than 0.4% SA, the gel changed from opaque to translucent. According to the zeta potential results, SA and FG associated via electrostatic interactions. The FG-SA complex coacervates, the SA fibrous network, and the FG-SA complex network were observed using atomic force microscopy. Based on the results, a schematic model was proposed, wherein at low SA concentrations (≤0.2%), FG associates with SA, resulting in large, complex coacervates with a diameter up to 1064 nm. With increasing SA concentrations, formation of complex coacervates was promoted because of the excess of negatively charged SA, which led to complex networks. The complex network structure was coarser than that observed for SA or FG alone. Moreover, the schematic model was further validated at the microstructure level using confocal scanning laser microscopy and Fourier transform infrared spectroscopy. The nanostructure mismatch between FG-SA and pork gelatin resulted in a texture mismatch.