Gelling properties and interaction analysis of fish gelatin–low-methoxyl pectin system with different concentrations of Ca2+

Abstract Fish gelatin is a potential resource for the replacement of mammalian gelatin. This work sought to modify tilapia gelatin (TG) with low-methoxyl pectin (LMP) and Ca2+, to improve its gelling performance. The gel properties, microstructure, and formation mechanism of the modified gels were estimated by rheological, textural, and scanning electron microscopy analysis methods. Furthermore, physicochemical properties such as the transmittance, zeta potential, particle size distribution, and hydrogen-bonding characteristics were studied. The research showed that Ca2+ enhanced the melting temperature and apparent viscosity of TG-LMP gels as its concentration increased from 0 to 3.0 mM. The highest hardness was obtained at a Ca2+ level of 2.0 mM, while excessive Ca2+ resulted in a loose and fragile gel structure. The ability of the TG and LMP molecules to aggregate as large complexes was also promoted by Ca2+ via salt bridges and van der Waals forces. A schematic model was proposed to illustrate the progressive modification of TG by LMP and Ca2+. These results suggest that the addition of LMP and the appropriate concentration of Ca2+ triggers the formation of crosslinks with TG, which increase the melting temperature, viscosity, and hardness of the gelatin.