Potential for fabricating tough double network hydrogels using mixed polysaccharides: High-acyl gellan with low-acyl gellan, agar, or κ-carrageenan

In this study, the possibility of creating tough, non-animal sourced double-network hydrogels for application in plant-based foods was examined. High acyl gellan (HG) was used to form a soft/elastic network and kappa-carrageenan, low acyl gellan, or agar were used to form a hard/brittle network. The gelation of the polysaccharides was induced by controlling the temperature and adding monovalent cations (K+) to create physical crosslinks between the polysaccharides. Texture profile analysis, which involved measuring the stress versus strain relationship during large-deformation compression, showed that different polysaccharides exhibited different fracture behaviors. Composite hydrogels were formed by blending soft and hard gelling polysaccharides at differing mass ratios (1:4 to 1:8). These hydrogels were proposed to have a (semi-) interpenetrating network structure without strong interactions between the different polysaccharides, based on the results of differential scanning calorimetry, zeta-potential, and structural analyses. Texture profile and rheological analyses showed a greater gel strength for the composite hydrogel than for the pure HG hydrogel in the linear range, but non-linear texture analysis showed no synergistic improvements in fracture behavior. Instead, the composite hydrogels exhibited fracture properties that were between those of hydrogels formed from the individual polysaccharides. Temperature ramp measurements showed that HG formed gels at significantly higher temperatures than the other polysaccharides, which may have inhibited effective network formation. This may have caused the hard gels to not dissipate energy effectively. This study offers valuable insights into the design and development of tough, edible double-network hydrogels that could be used to formulate plant-based foods with improved textural and oral processing properties.