Modulation and mechanistic control over fish gelatin hydrogelation using the variety of different ionic groups found on naturally occurring anionic polysaccharides

Abstract

Modifying fish gelatin (FG) with natural, functional polysaccharides is a cost-effective strategy for enhancing its gel properties for food applications. However, the mechanistic role of different ionic group types within polysaccharides in driving these enhancements remains unclear. In this study, three categories of commonly utilized anionic polysaccharides were selected: carboxylated polysaccharides (pectin, PEC; xanthan gum, XG; sodium alginate, SA); a glycosaminoglycan polysaccharide (hyaluronic acid, HA); and sulfated polysaccharides (fucoidan, Fu; carrageenan, κ-CG) were chosen as candidates to modulate molecular assembly by enhancing electrostatic, hydrogen-bonding, and hydrophobic interactions, ultimately optimizing gel properties. Of these, the Fu-FG composite hydrogel exhibited a marked ζ-potential decrease from −3.75 ± 0.25 mV (FG alone) to −24.23 ± 0.60 mV (p < 0.05). Sulfated polysaccharides (Fu, κ-CG) exhibited the most significant enhancement in the elastic modulus of the FG gel (583.8 Pa at 10 Hz). Carboxylated polysaccharides and the glycosaminoglycan polysaccharide were less effective. The Fu-FG composite gel exhibited the highest apparent viscosity (5126 mPa s at a shear rate of 100 s⁻¹). Structural characterization revealed that κ-CG-FG uniquely stabilized tightly bound water populations (T_2b1), while FTIR and circular dichroism analyses confirmed increased ordered secondary structures accompanied by a reduction in random coils. This study provides a theoretical foundation for designing functional protein gel materials based on ionic group types.